I just got a directional coupler, because of this video and tried it out with a lot of success. I am a big fan and watched a lot of your videos. They are extremely good, not trivial, but very understandable. In my youth I was a ham operator. In these days the frequencies and the budgets were much lower than now. I enjoy the revival of my "RF hobby" (also with my first spectrum analyzer), now paired with microcontrollers. Thank you very much for your effort to put your knowledge online!
A suggestion for a video might be the difference between a directional coupler and a return loss bridge... The insertion loss for a bridge seems to be much higher... Enjoy your videos, very very informative...
Alan, This is the first video of yours I watched and you are an amazing instructor. I sincerely thank you for taking the time to explain directional couplers to me!
Alan, can't thank you enough for all your videos and expertise. You inspire many to dig deeper into the technical aspects of radio and electronics. Thanks again!
At 4:23 you refer to 20 dB being "1/10th the power", but isn't it 1/10th the voltage, and 1/100th the power? I found this video very informative, and a great explanation. If the mood comes to you, I would like a video that explains a few of the ways couplers work.
@@w2aew 20 db down on power is 1/10 of voltage since "P-dbm = 20 * log(V-mpvv) - 56". so 1/10 of voltage is 20 db down. I did this calculation on my video: th-cam.com/video/_1R9fDVkjwk/w-d-xo.html
20 db down on power is 1/10 of voltage since "P-dbm = 20 * log(V-mpvv) - 56". so 1/10 of voltage is 20 db down. I did this calculation on my video: th-cam.com/video/_1R9fDVkjwk/w-d-xo.html
Can’t say how many times ive watched this video. Can i add that at the moment you are seeing reflected signals that they may also be out of phase at 7:39 ?
I'm glad you did this video. I recently purchased a spectrum analyzer with a tracking generator. I wanted to look at S11 and VSWR with it and there is a directional coupler made for this analyzer that cost around $700.00. However, that Mini Circuits directional coupler does the same thing for under $100.00 fantastic! I really enjoy your video's lots of good information. Thanks!
At my former job I always had access to a network analyzer for these type of measurements. It is funny that I didn't know there was a such thing as a tracking generator for a spectrum analyzer as a 'lower tech' way to measure a coupler's response. Very nice tutorial, I enjoy watching them.
Have been home brewing some amateur osc/amps and an antenna for 1.269 GHz. I have the same type coupler. Your video is a great help. I am using attenuators and crystal detector to get my measurements. Great video!
Yes, I could've used the noise generator and spectrum analyzer in the MDO and it would've worked fine. However, I showed this technique to show the filter responses in the SDR radios and figured that viewers like yourself would recognize that this would be an alternative way to "sweep" the antenna.
Thanks for this video, I recently got a Rigol DSA-815TG and also a directional coupler, but I have a lot of problems with ripples in my return loss plots. I tried to connect a 6dB or 10dB pad between the TG and the SWR bridge, but the ripples keep persisting. I've tried using my 10 meter long coax for HF, and also a good quality 1 meter long SMA cable, but the ripples are still noticeable. However, when using a short piece of SMA cable (15cm or so) the ripples are almost completely gone. Would connecting an attenuator between the SWR bridge and the spectrum analyzer input achieve anything? I'm waiting for some N to SMA adapters so those should come in tomorrow, I can't try it out yet. Thanks again!
I got an EE degree 50 years ago and at some point the prof zipped through how a directional coupler works. I didn't understand it but I still managed to use couplers and hybrids through a career. NOW I'm retired and I don't need the devices but I want to learn how they actually work. Can't seem to find an explanation. I guess everybody just uses them. But if you look at a coupler logically, it's like a bumblebee-- bumblebees are not supposed to be able to fly. Likewise for the directional coupler--can't fly and shouldn't divide out the forward and backward signals. They are too small. If you stick a stake in a creek or river, it can tell you the level of the water -- analogous to showing the vector sum of the voltage at a point on a transmission line. You have no way of knowing the direction in which the water is flowing. The same should be true of a "directional" coupler. At microwave frequencies maybe there is room for more "direction finding" components. But a classical directional coupler for a 7 MHz sine wave is usually less than 6 inches wide--at 7 MHz a quarter wavelength is about 40 feet---CAN'T WORK. It's a bumblebee. I'm still searching for an explanation. For now, I treat directional couplers like UFOs--some people say they've seem them--personally I haven't. Don't believe in them myself.
I have a directional coupler with no data sheet. What test can I perform to determine its frequency range. I have a 1-4ghz sweep generator and a 2.4-2.5ghz spectrum analyzer. Ports are in, out, -30db, and ISO? Made by RF Power. SDC-182-202-R1-30
Firstly, you are a great instructor. Being licensed in 1953 as W5WTN, a lot has changed. I wonder if you are familiar with the Rogol SA. I have the 2 Ghz version and when I try to use the normalization function, the soft key is grayed out. The instructions state to change the settings to Dbm, which I did. No cigar. If you have any suggestions, please let me know. Keep up the good work. Best 73's Eddy W5WTN
First rate Allan. I can't afford the Mini-Circuits device but see that Paul W1GHZ has a pair of bi-directional coupler designs in Hammond die-cast boxes that probably do as well for £20 home made. 73 de M0YDH
Thank you, sir, I have 2 questions. 1. Can I connect an RF signal generator instead of an Antenna at 9:37 to measure the output impedance of the RF signal generator? 2. Can you explain the difference between VWSR Bridges & Directional Couplers? If you have a chance, could you explain them to me?
I ran this experiment on a 1.27 GHz antenna using a signal generator, spectrum analzyer and compared 2 directional couplers. 1 Mini-Circuits like in the video and a Chinese model. The results were significantly different. Mini-Circuits return loss was 18.51 dB Chinese model was 42.41 dB with a much narrower trough. The frequency also shifted 84MHz. Since I don't have a tracking gen, I sweep the frequency range and use "Max Hold" until the screen fills in and use that as the '0' reference. I have repeated this experiment multiple times in different frequency ranges with similar results. Any Idea why the results would be this different between 2 couplers?
Is it possibile, when antenna is matched to 50ohm (checked using resistors bridge, antenna tunner and oscilloscope), that there is standing wave in antenna's feedline? (Asuming that coax is also 50ohm). I think that should not because whole system is matched so should be no reflectuons, but I am not sure if coax dimensions can introduce some reflections.
Ideally, if the 50 ohm coax is terminated in a 50 ohm load, there will be no standing waves. However, depending on the coax, small impedance discontinuities can be introduced by bending the coax, which can result in small reflections and small standing waves.
Hi, I didn't know for directional couplers. I'm learning basic of RF and transmission lines... I tried to create directional coupler of piece of cable. Terminated output, give me 0 on coupled output. When output is open, coupled signal and signal from source are in phase, which is expected, but when I short output, signals are about 90 degrees out of phase. Why 90? I expected 180. Is it my setup problem or I didn't understood. Thanks
I would love it if you made a video on multichannel RF splitters and distribution amps ( splitter loss gain loss ) theory. I'm trying to split a single Log Periodic Dipole Array antenna for Diversity reception ( 2 x antenna ) into 4 x diversity radio mic receivers and would like to add 2 x antenna LNA's onto the antenna to boost the signal to match the db gain loss made on the splitter. There are many factors!! cable loss , splitter loss. RF amp noise per antenna. at least I'm looking at 50ohm impedance all the way ( i hope ) from antenna to receivers so hopefully no mismatch. Anyway , splitter theory and distribution amp / noise etc theory video would be so helpful. Thanks for these great videos :)
should also say any ideas on low cost 50ohm LNA's with variable gain for approx 400mhz - 700mhz would be helpful. I think from watching this video I can use a sig gen to check the gain on the splitter outputs is unity from antenna output with an oscilloscope.
I"ll add these topics to my long list. Suffice it to say that power is always reduced through a splitter - even for the basic reason of conservation of energy. Even considering an ideal lossless 2-way splitter, the power in each output would be half of the input. However, there is no such thing as a lossless splitter...
@@w2aew Yes, it seams you get 3db loss ( half gain ) + insertion loss of say 0.4db at best ( at least on my micro circuits splitter ) so far I've learned i should place the 2 x LNA's near the antenna to compensate for the loss so that i'm not amplifying cable noise. Also finding LNA's all introduce noise! I also need to try and learn if gain is that important! As far as I can understand what is more important is signal to noise ratio? I'm thinking in a diversity setup the gains should be reasonably equal so that the receiver can switch to best receive signal strength. Thats assuming received signal strength is relative to gain? I will do some tests but I wouldn't be surprised if the LNA's don't help me in the real world with TX - RX range :) anyway , would be great if you could do some LNA gain / splitter gain compensation theory one day. Thanks a lot for all these great videos.
@@BenBilesBB-box Yes, of course LNAs add noise - the amount of noise added is measured by something called the Noise Figure - something else I need to add to my long list.
Taking what Alan says in that video, at face value, might do more harm than good, as the finite directivity of the coupler inserted between the spectrum analyser and the antenna under test, does limit the range of return loss, where the proposed setup makes sense in terms of engineering accuracy; I'll let you do the math' and evaluate the dramatic impact of the directivity of some commercial couplers... Pray pardon my candour, as I feel compelled to say how surprised I am, that the highly qualified & experienced engineers who have commented here, have not picked up on that limitation, not to mention the effect of a slight mismatch of the load of the so-called isolated port, that is a port that is not so isolated after all (!) * internal or plugged externally
Dip the plate, lower the current. Efficiency of a tube with a directional coupler used as a sample port. Used them with gridded traveling wave tubes as well. Great channel you have!!
Alan, A very informative video per usual but -- and forgive me if I sound grumpy -- it would be great if you could do more stuff for us proles who limp along with a test equipment budget several magnitudes less than yours. For example, your time domain refectometry stuff was a tour de force and scintillating because it had "everyham" written all over it. Most of us are lucky if we have An old 465 and an AN/URM-25D and some grotty RG-8X. Respectfully, Willie, the Grouch.
Understood Will. Of course you could manually sweep the return loss with a directional coupler and a scope and signal generator. But, I wanted to focus more on the coupler rather than the manual process with this video. So some videos will involve more extensive equipment, some won't. Thanks for watching, and for your comments.
***** I completely understand. Thank you for your response. I think I need to get a grip and realize that you are doing this on your own time, out of the kindness of your heart, and I am essentially getting this content for free. Was having a bad hair day. Please keep up the good work!
William Phinizy No problem Will! I am lucky that I have access to some really cool tools due to my job. Hopefully I'm striking a good balance between my hobbyist and professional viewers. Thanks again for watching!
Thank you for taking your time to make this video! I learned so Much. I recently purchased a Rigol DSA815 TG and a ZFDC 20-4 coupler. I was confused on using the coupler till you cleared it up! 73's David. K8KEM
Hi Alen. I cannot find what is mix power, that this direction coupler can handle? I mean, can I use this for monitor 40 or 50dBm with spectrum analyzer. I will connect radio -> direction coupler -> antenna, and coupling port -> 2W 30dB attenuator -> SA? I cannot find this information on minicircuits site (I have ZFDC-20-4 20db 1GHz coupler). Thanks for great videos
The maximum input power is listed in the datasheet. For 1-10MHz, the maximum input power is 0.5W (27dBm), and for 10-1000MHz, the maximum input power is 2W (33dBm). So, unfortunately this coupler is not suitable for 40-50dBm input. For that kind of power level, you're much better off using an RF sampler.
I have the same mini circuits directionaql coupler that you have there and an eagle return loss bridge. I bought one of those el cheapo green directional couplers off ebay and I was very surprised at how well it performs
Alan, great video. Question, how accurate do you find the MFJ to be? I see it being used by most hams, including my dad, but I am aware that numbers on an LCD don't always reflect the truth. On the other hand, if it is a tool used by most it can be considered as a standard no matter the downsides. Would it be valuable for you to make a video on the MFJ pointing out how to correctly interpret the values displayed by it? Regards, CX6BT
I've found the MJF to be accurate enough to be effective. One thing you have to be careful with is that when testing antennas, signals that are picked up by the antenna may couple into the bridge and upset the readings. I'll think about doing a few vids on the 259B in the future.
A good video. Interesting is that the waveform voltage on channel 1 increased when the load was increased from 50 ohm to 1 meg ohm. And the power transferred was then less than with the 50 ohm load even though the waveform voltage increased. If you known what the increased voltage was across the 1 Mohm load, you could compare the transferred power to when the load was 50ohm.
Thank your for this video... as a junior RF engineer this was informative. Maybe some one has already asked but can the coupled port be used to inject a sample signal? How would that work?
Thank you so much Alan for teaching us this. I used a directional coupler tonight to look at a chinese fpv antenna and found out it wasn't exactly what I thought it was. All thanks to you! Mike K8MB.
Hello Alan! I do hope you don’t mind me asking a question via email than on utube? I am unfortunately, not a real smart guy (82 yrs old!) when it comes to seeing different values of R/L in different scenarios and thus , I have confused myself and could use a bit of help if you don’t mind ? Case one : I have a Rigol DSA815TG SpecAn along with a Mini Ckts ZFDC 20-5 DC and a highly Precision HP 50 ohm Load. I also purchased (from either a China or Russia) a 01 to 3000 MHz RF Bridge. This bridge requires an external 50 Ohm Load unlike the ZFDC that has the 3rd port terminated in a 50 ohm Load, For the first part of this - The Rigol was set to start QRG 1.8 MHz and stop QRG at 450 MHz (the Rigol goes to 1.5 Ghz) for this experiment- RBW set 30 KHz - VBW set at 1 KHz A) Using the RF Bridge, “Output to SpecAn input” - “Input to TG Output”. “Excellent 50 ohm Load on the “REF port” and nothing on the “DUT” port - then I “Normalize” the DSA815TG. (TG level set to zero db from -20db). A 10db pad is on the “Output” of the TG. Best Results : 30 MHz R/L 59db 145 MHz R/L. 59db 450 MHz R/L. 38db All I do now is exchange the RF Bridge for the ZFDC And renormalize again. Best Results: 30 MHz R/L 32 dB 145 MHz R/L 31.8 dB 450 MHz R/L. 30.2 dB Question: Why a difference of 20 db or so between the Bridge and ZFDC? Which is believable ? Or are they both correct ? Part two (with me, there is always a part two!) I also have. HP 8711A RF Networks Analyzer. On this unit, there is of course no need for either a bridge or DC due to it being an internal device in this unit. I have set up the network Analyzer with same start/Stop QRG And I use my “Precision” HP # 909F 50 ohm Load. The Analyzer is calibrated with an open/short and load (using the same 50 ohm Load as I will be testing) Results: 1.8 MHz. 54db 30 MHz 53db 450 MHz 50db Alan, your thoughts? Anything will be very much appreciated! 73 David. de K8KEM
It *is* a bit of RF magic, coupled quarter wave transmission lines most often, but there are other configs with lumped elements, or coupled transformers, etc.
Just to make a point; not ALL energy is reflected back or radiated, some of the energy is being disipated as heat in dielectric and conductivity losses by the transmission line and the antenna. I believe you made a video on skin effect.
Miguel Rodriguez Good points. Skin effect isn't much of an issue at the HF frequencies where this coupler is designed to work. However, dielectric and IR losses should be taken into account for longer transmission line runs and higher frequencies.
***** One good video would be to make one just about skin effect and losses in coaxial trasmisión lines, you did mentioned it on your video #56. KE6OJE
Hey I really like this video. I am considering in buying a spectrum analyzer for tuning antennas on a PCB (chip antennas). But they can be so damn expensive! So I was wondering, would a MFJ-259B do the trick? Thanks in advance! What power rating on an attenuator would you recommend so that an antenna as a DUT doesn't drive the tracking generator by picking up arbitrary rf signals from the air?
The MFJ-259B only goes up to 470MHz, which seems a little low for PCB chip antennas. But, if this is within your frequency range, this unit works pretty well. It will give you VSWR as well as impedance and phase - it just can't distinguish between positive or negative phase angle. It would be difficult for me to recommend an attenuation value because I don't know you're situation (how tightly coupled your antenna will be to the off-air signal, what kind of power levels you're dealing with, etc.).
Hi James. I've never used the Siglent spectrum analyzer, so I really can't tell you why the "normalization" function is grayed out on your unit. This is a function that is used along with the Tracking Generator. Maybe you don't have the tracking generator setup/configuration completed?
Thank you for another great video. At about 6:40, you switch the load from 50ohm to 1M ohm and comment that almost all the power is now reflected. On the scope, indeed I see both the yellow voltage trace and the yellow rms voltage readout go from around 225V to 407mV, the result of the two signals adding together. FB. And I can see the blue trace showing the coupled reflected signal. My questions: Why is the coupled signal phase shifted (about 45degrees), why isn’t the main line voltage shifted some too?
The main line isn't shifted, because the scope is triggering on that line (so it always lines up in the same place on the screen). The phase shift of the reflected signal in this case is simply due to the propagation delay back and forth through the coax.
I bought a directional coupler on ebay. Coaxial dynamics model 3580. The coupled ports dont have coax connection. They have two leads on each port. You can find pictures of it in Google. My question is, what and how do I measure and how do I use that to find the rf signal strength going through the main line? I couldn't find any help anywhere and the seller also has no idea. I thought I would ask you. I watch your videos.Very educational. I am a new hobbyist in the RF field.
It's difficult to say without any kind of a data sheet. But, since it's designed for 800 MHz and the sense ports are not coaxial, I'd expect that there's probably a diode detector behind each of the sense ports, so you'd probably see a DC voltage proportional to sensed power. Might bonded a capacitor across the terminals.
Excellent video. I have a question... if I use a basic and inexpensive antenna tuner like RigExpert AA-600 to observe the tuning dip, will that be as good as the spectrum analyzer method you have used?
Nice video. I'm a new HAM and I'd like to characterize the 20m half-wave dipole antenna I recently installed in my attic. Can I use this technique without generating RF interference from my antenna?
when i terminate with dummy load i get -45dbm thats. 25 down on an open, very good. Thing is when i connect and tune my antenna i get -55dbm, how can the antenna be better than a perfect load. cable and generator all 50 ohm
Thnx ... very useful. I just received my reflection bridge and want to check my antenna's using the VNA. My reflection bridge has IN OUT and a DUT .... i should connect the antenna to DUT and the signal output of the tracking to IN. I don't quite understand your setup.
If you have a VNA, it would already have the bridge or directional coupler built in. There shouldn't be a need for an external reflection bridge (unless it is an older VNA that specifically used external bridges/couplers).
@@egbertgroot2737 OK, that's an older analyzer that uses an external transmission/reflection test set. A directional coupler will sample the signal going thru the coupler from IN to OUT. Since the signal you want to measure is the reflection coming back from the antenna, you would want to connect the antenna to IN and the signal source to OUT. The manual for the HP4195A can be found here: literature.cdn.keysight.com/litweb/pdf/5950-2942.pdf?id=619880
Great video! This is the second time I watched it, and can't tell you how much I appreciate the work you do in producing these. Very helpful to us folks returning to the hobby! I do have a question. Rigol sells a "SWR Measuring Kit" for their spec analyzer that pretty much looks like one of these couplers and a few fittings stuffed into a fancy box (with matching price). Is that all it is? It looks like there might be software also, but I'm guessing that it's just minor stuff - say, calibration data and a few automation procedures - for whatever coupler they used. What do you think? Thanks again!
gave it a try on a 2M Jpole type antenna, worked great. I'm confused about return loss bridges and when and why to use them over a directional coupler.
+Mark Butterworth Return loss bridges output a DC voltage in proportion to an impedance mismatch, while directional couplers output a sample of the RF energy flowing in a chosen direction. Either one can be used to characterize the mismatch of an antenna system - it all depends on how you want to process/measure the reflected signal.
Thanks a lot for this video w2aew. Learnt a lot from it. Directional coupler is a neat device. Very nicely explained. The only thing a little unclear @10:00 is that we are viewing the coupled port correct?
Hey, Is the output seen in the spectrum analyzer the actual s11 curve, as the output is obtained from a different port than the input? It seems to contradict the common definition of s11.
+Pranjal Paliwal A network analyzer uses a directional coupler to measure the output and reflected power at each port - so there's basically a coupler behind each port of a network analyzer.
Hi, I have a question. When you are testing the antenna, the signal from the tracking generator to the antenna is reflected back to it for the non-resonating frequencies. Won't this interfere with the subsequent signals sent from the tracking generator?
+Shalini Srinivasan It can, which is why an attenuator is often included in series with the TG output. However, if the end goal is to achieve a good match (no reflection), then the point is moot because there will be no reflection at the desired point.
Hi Allen! Thank you for taking your time to make this excellent video! I have some questions. If I may! I now have a ZFDC 20-4 (which works for me and no -5 on eBay!) I am using a Rigol DSA815 w/Tracking Gen. From the D.C. I have the OUT going to the TG, the CPL to the SA and then with 0db i "Normalize" the TG. "Then" I attach a precision 50 ohm load to the "IN" port. I believe that this is the correct procedure to measure Return Loss. In this scenario, it appears I am seeing the R/L of the 50 ohm load. The freq start 1 MHz Stop Freq 1Ghz. Please correct my procedure if I am in error. Final question, what is the procedure for checking Directivity for the D.C. ? Thanks In advance Allen. 73's David K8KEM
In your procedure, you're using the "open" on the IN of hte D.C. to provide a 100% reflection in order to normalize the coupling factor of the D.C. This should work well enough. Then, connecting your 50 ohm load, you should see a very low (large negative number) return loss. To measure the directivity - connect the TG to the IN, SA to the CPL and 50 ohm to the OUT. You should get something that is about 20dB down (the coupling factor). You can "normalize" this trace, then swap the IN and OUT connections on the D.C., and what you see should be the directivity (about 27dB down). Directivity is the difference of the CPL response for forward and reverse signals.
w2aew again Thank you so very much Allen! I have learned so much from you! What makes your videos so great is that you speak clearly and quite distinctly and at a pace that is very good! 73's David K8KEM
Generally a signal that is intended at some point to be sent over the air, hence Radio Frequency. Usually single-frequency signal that is modulated in some way.
get a dual directional coupler to measure reflected power. I have always been taught to terminate at the load, not at the source. have you heard this or think it makes a difference?
Hello... I'm trying to find what the vswr is for a SMA to TNC RF adapter and Using your set up to find what the VSWR is from 2 to 8.0 GHZ, 8 to 16 GHZ and 16 -18 GHZ. Since the adapter is not an antenna will it work you procedure Work?
You can probably estimate it with an appropriate directional coupler and careful calibration/normalization - but it won't be as accurate as a proper VNA.
Thanks... Do you happen to know who can offer testing for our requirement? All I find is new VNA on line and no companies listing measurements services. I appreciated any help you can give us.
I just got a directional coupler, because of this video and tried it out with a lot of success. I am a big fan and watched a lot of your videos. They are extremely good, not trivial, but very understandable. In my youth I was a ham operator. In these days the frequencies and the budgets were much lower than now. I enjoy the revival of my "RF hobby" (also with my first spectrum analyzer), now paired with microcontrollers.
Thank you very much for your effort to put your knowledge online!
...and it is a pleasure for me to meet the two youtubers favorite by me on the same page !!! Great!
@@picwiz2 same to me ;-)
Good stuff!
this is most professional channel about electronics in educational aspect on yt. Thank you Alan
Thank you, I'm glad you enjoy it!
A suggestion for a video might be the difference between a directional coupler and a return loss bridge... The insertion loss for a bridge seems to be much higher... Enjoy your videos, very very informative...
Alan, This is the first video of yours I watched and you are an amazing instructor. I sincerely thank you for taking the time to explain directional couplers to me!
Alan, can't thank you enough for all your videos and expertise. You inspire many to dig deeper into the technical aspects of radio and electronics. Thanks again!
At 4:23 you refer to 20 dB being "1/10th the power", but isn't it 1/10th the voltage, and 1/100th the power?
I found this video very informative, and a great explanation. If the mood comes to you, I would like a video that explains a few of the ways couplers work.
Ack! I hate when that happens! Of course, you're right. I've added an annotation to correct my mis-spoken narration.
gets tricky when you speak volts and dbm
@@w2aew 20 db down on power is 1/10 of voltage since "P-dbm = 20 * log(V-mpvv) - 56". so 1/10 of voltage is 20 db down. I did this calculation on my video: th-cam.com/video/_1R9fDVkjwk/w-d-xo.html
20 db down on power is 1/10 of voltage since "P-dbm = 20 * log(V-mpvv) - 56". so 1/10 of voltage is 20 db down. I did this calculation on my video: th-cam.com/video/_1R9fDVkjwk/w-d-xo.html
Can’t say how many times ive watched this video. Can i add that at the moment you are seeing reflected signals that they may also be out of phase at 7:39 ?
Wonderful tutorial! Thanks for posting.
Great video. Thank you so much
I'm learning so many things from your channel.. Thank you very much... 👍👍👍
I'm glad you did this video. I recently purchased a spectrum analyzer with a tracking generator. I wanted to look at S11 and VSWR with it and there is a directional coupler made for this analyzer that cost around $700.00. However, that Mini Circuits directional coupler does the same thing for under $100.00 fantastic! I really enjoy your video's lots of good information. Thanks!
4:30 you mean one tenth the VOLTAGE is 20dB.
Yup - I mis-spoke
At my former job I always had access to a network analyzer for these type of measurements. It is funny that I didn't know there was a such thing as a tracking generator for a spectrum analyzer as a 'lower tech' way to measure a coupler's response. Very nice tutorial, I enjoy watching them.
Brilliant....i think .if anyone can explain it you can
I am impressed and this helped me greatly figure out how to measure the VSWR on one of my antennas at work.
Have been home brewing some amateur osc/amps and an antenna for 1.269 GHz. I have the same type coupler. Your video is a great help. I am using attenuators and crystal detector to get my measurements. Great video!
I could watch these many times over as they have great density of. Information. Ty for taking time to do these clear tutorials as always .
Szkoda, że nie widać kabli łączących urządzenia oraz generatora.
Your video helped me a lot today. Thank you.
Wow! Just the explication I've been looking for for a very long time. Thanks!!
Glad it helped you out!
why you don't using MDO3104 spectrum analyzer ?
Noise function will not work for this measurement ?
Yes, I could've used the noise generator and spectrum analyzer in the MDO and it would've worked fine. However, I showed this technique to show the filter responses in the SDR radios and figured that viewers like yourself would recognize that this would be an alternative way to "sweep" the antenna.
Great video! Thanks for providing this good (and well presented) info. Cleared up a few things for me. 73s!
Thanks for this video, I recently got a Rigol DSA-815TG and also a directional coupler, but I have a lot of problems with ripples in my return loss plots. I tried to connect a 6dB or 10dB pad between the TG and the SWR bridge, but the ripples keep persisting. I've tried using my 10 meter long coax for HF, and also a good quality 1 meter long SMA cable, but the ripples are still noticeable. However, when using a short piece of SMA cable (15cm or so) the ripples are almost completely gone. Would connecting an attenuator between the SWR bridge and the spectrum analyzer input achieve anything? I'm waiting for some N to SMA adapters so those should come in tomorrow, I can't try it out yet. Thanks again!
Was für eine schreckliche Computerstimme. Hab mitten drin leider abgeschaltet. So was mag ich überhaupt nicht
I got an EE degree 50 years ago and at some point the prof zipped through how a directional coupler works. I didn't understand it but I still managed to use couplers and hybrids through a career. NOW I'm retired and I don't need the devices but I want to learn how they actually work. Can't seem to find an explanation. I guess everybody just uses them. But if you look at a coupler logically, it's like a bumblebee-- bumblebees are not supposed to be able to fly. Likewise for the directional coupler--can't fly and shouldn't divide out the forward and backward signals. They are too small. If you stick a stake in a creek or river, it can tell you the level of the water -- analogous to showing the vector sum of the voltage at a point on a transmission line. You have no way of knowing the direction in which the water is flowing. The same should be true of a "directional" coupler. At microwave frequencies maybe there is room for more "direction finding" components. But a classical directional coupler for a 7 MHz sine wave is usually less than 6 inches wide--at 7 MHz a quarter wavelength is about 40 feet---CAN'T WORK. It's a bumblebee. I'm still searching for an explanation. For now, I treat directional couplers like UFOs--some people say they've seem them--personally I haven't. Don't believe in them myself.
I have a directional coupler with no data sheet. What test can I perform to determine its frequency range. I have a 1-4ghz sweep generator and a 2.4-2.5ghz spectrum analyzer. Ports are in, out, -30db, and ISO? Made by RF Power. SDC-182-202-R1-30
Firstly, you are a great instructor. Being licensed in 1953 as W5WTN, a lot has changed. I wonder if you are familiar with the Rogol SA. I have the 2 Ghz version and when I try to use the normalization function, the soft key is grayed out. The instructions state to change the settings to Dbm, which I did. No cigar. If you have any suggestions, please let me know.
Keep up the good work.
Best 73's Eddy W5WTN
First rate Allan. I can't afford the Mini-Circuits device but see that Paul W1GHZ has a pair of bi-directional coupler designs in Hammond die-cast boxes that probably do as well for £20 home made. 73 de M0YDH
Thank you, sir, I have 2 questions.
1. Can I connect an RF signal generator instead of an Antenna at 9:37 to measure the output impedance of the RF signal generator?
2. Can you explain the difference between VWSR Bridges & Directional Couplers?
If you have a chance, could you explain them to me?
I ran this experiment on a 1.27 GHz antenna using a signal generator, spectrum analzyer and compared 2 directional couplers. 1 Mini-Circuits like in the video and a Chinese model. The results were significantly different. Mini-Circuits return loss was 18.51 dB Chinese model was 42.41 dB with a much narrower trough. The frequency also shifted 84MHz. Since I don't have a tracking gen, I sweep the frequency range and use "Max Hold" until the screen fills in and use that as the '0' reference. I have repeated this experiment multiple times in different frequency ranges with similar results. Any Idea why the results would be this different between 2 couplers?
this was very clear. thanks. I will give this a go building my new antenna
Is it possibile, when antenna is matched to 50ohm (checked using resistors bridge, antenna tunner and oscilloscope), that there is standing wave in antenna's feedline? (Asuming that coax is also 50ohm). I think that should not because whole system is matched so should be no reflectuons, but I am not sure if coax dimensions can introduce some reflections.
Ideally, if the 50 ohm coax is terminated in a 50 ohm load, there will be no standing waves. However, depending on the coax, small impedance discontinuities can be introduced by bending the coax, which can result in small reflections and small standing waves.
Hi,
I didn't know for directional couplers. I'm learning basic of RF and transmission lines...
I tried to create directional coupler of piece of cable. Terminated output, give me 0 on coupled output. When output is open, coupled signal and signal from source are in phase, which is expected, but when I short output, signals are about 90 degrees out of phase. Why 90? I expected 180. Is it my setup problem or I didn't understood.
Thanks
I would love it if you made a video on multichannel RF splitters and distribution amps ( splitter loss gain loss ) theory. I'm trying to split a single Log Periodic Dipole Array antenna for Diversity reception ( 2 x antenna ) into 4 x diversity radio mic receivers and would like to add 2 x antenna LNA's onto the antenna to boost the signal to match the db gain loss made on the splitter. There are many factors!! cable loss , splitter loss. RF amp noise per antenna. at least I'm looking at 50ohm impedance all the way ( i hope ) from antenna to receivers so hopefully no mismatch. Anyway , splitter theory and distribution amp / noise etc theory video would be so helpful. Thanks for these great videos :)
should also say any ideas on low cost 50ohm LNA's with variable gain for approx 400mhz - 700mhz would be helpful. I think from watching this video I can use a sig gen to check the gain on the splitter outputs is unity from antenna output with an oscilloscope.
I"ll add these topics to my long list. Suffice it to say that power is always reduced through a splitter - even for the basic reason of conservation of energy. Even considering an ideal lossless 2-way splitter, the power in each output would be half of the input. However, there is no such thing as a lossless splitter...
@@w2aew Yes, it seams you get 3db loss ( half gain ) + insertion loss of say 0.4db at best ( at least on my micro circuits splitter ) so far I've learned i should place the 2 x LNA's near the antenna to compensate for the loss so that i'm not amplifying cable noise. Also finding LNA's all introduce noise! I also need to try and learn if gain is that important! As far as I can understand what is more important is signal to noise ratio? I'm thinking in a diversity setup the gains should be reasonably equal so that the receiver can switch to best receive signal strength. Thats assuming received signal strength is relative to gain? I will do some tests but I wouldn't be surprised if the LNA's don't help me in the real world with TX - RX range :) anyway , would be great if you could do some LNA gain / splitter gain compensation theory one day. Thanks a lot for all these great videos.
@@BenBilesBB-box Yes, of course LNAs add noise - the amount of noise added is measured by something called the Noise Figure - something else I need to add to my long list.
Taking what Alan says in that video, at face value, might do more harm than good, as the finite directivity of the coupler inserted between the spectrum analyser and the antenna under test, does limit the range of return loss, where the proposed setup makes sense in terms of engineering accuracy; I'll let you do the math' and evaluate the dramatic impact of the directivity of some commercial couplers... Pray pardon my candour, as I feel compelled to say how surprised I am, that the highly qualified & experienced engineers who have commented here, have not picked up on that limitation, not to mention the effect of a slight mismatch of the load of the so-called isolated port, that is a port that is not so isolated after all (!)
* internal or plugged externally
Srry Alan i can only thumb up yr video one time.
Excellent video. Thank you very much for sharing it. Truly useful information.
Dip the plate, lower the current. Efficiency of a tube with a directional coupler used as a sample port. Used them with gridded traveling wave tubes as well. Great channel you have!!
Alan,
A very informative video per usual but -- and forgive me if I sound grumpy -- it would be great if you could do more stuff for us proles who limp along with a test equipment budget several magnitudes less than yours. For example, your time domain refectometry stuff was a tour de force and scintillating because it had "everyham" written all over it.
Most of us are lucky if we have An old 465 and an AN/URM-25D and some grotty RG-8X.
Respectfully,
Willie, the Grouch.
Understood Will. Of course you could manually sweep the return loss with a directional coupler and a scope and signal generator. But, I wanted to focus more on the coupler rather than the manual process with this video. So some videos will involve more extensive equipment, some won't. Thanks for watching, and for your comments.
*****
I completely understand. Thank you for your response. I think I need to get a grip and realize that you are doing this on your own time, out of the kindness of your heart, and I am essentially getting this content for free.
Was having a bad hair day. Please keep up the good work!
William Phinizy No problem Will! I am lucky that I have access to some really cool tools due to my job. Hopefully I'm striking a good balance between my hobbyist and professional viewers. Thanks again for watching!
Thank you for taking your time to make this video! I learned so
Much. I recently purchased a Rigol DSA815 TG and a ZFDC 20-4 coupler. I was confused on using the coupler till you cleared it up! 73's David. K8KEM
“Hope you learned something”. You bet. Thanks Alan, Cheers, Mark
Finally I understand how a coupler works. Thanks
Hi Alen. I cannot find what is mix power, that this direction coupler can handle? I mean, can I use this for monitor 40 or 50dBm with spectrum analyzer. I will connect radio -> direction coupler -> antenna, and coupling port -> 2W 30dB attenuator -> SA? I cannot find this information on minicircuits site (I have ZFDC-20-4 20db 1GHz coupler). Thanks for great videos
The maximum input power is listed in the datasheet. For 1-10MHz, the maximum input power is 0.5W (27dBm), and for 10-1000MHz, the maximum input power is 2W (33dBm). So, unfortunately this coupler is not suitable for 40-50dBm input. For that kind of power level, you're much better off using an RF sampler.
@@w2aew Thank you
I have the same mini circuits directionaql coupler that you have there and an eagle return loss bridge. I bought one of those el cheapo green directional couplers off ebay and I was very surprised at how well it performs
Alan, great video.
Question, how accurate do you find the MFJ to be? I see it being used by most hams, including my dad, but I am aware that numbers on an LCD don't always reflect the truth. On the other hand, if it is a tool used by most it can be considered as a standard no matter the downsides. Would it be valuable for you to make a video on the MFJ pointing out how to correctly interpret the values displayed by it? Regards, CX6BT
I've found the MJF to be accurate enough to be effective. One thing you have to be careful with is that when testing antennas, signals that are picked up by the antenna may couple into the bridge and upset the readings. I'll think about doing a few vids on the 259B in the future.
Than you. In Algeria, this informations is confidential and monopolistic
Yep, coupled ports are used to monitor antennas along the path. Basically the load is coupled pre and post wherever it goes next.
Thank you very much for taking your time to make this video! It's appreciated 73's David. K8KEM
A good video. Interesting is that the waveform voltage on channel 1 increased when the load was increased from 50 ohm to 1 meg ohm. And the power transferred was then less than with the 50 ohm load even though the waveform voltage increased. If you known what the increased voltage was across the 1 Mohm load, you could compare the transferred power to when the load was 50ohm.
Thank your for this video... as a junior RF engineer this was informative. Maybe some one has already asked but can the coupled port be used to inject a sample signal? How would that work?
I have been 'standardized' by using a 1dB pad for the impedance leveling.
Hi Allen ... great info. Could you perhaps do a video on the MFJ analyser as to how to properly calibrate it?
Thank you & 73,
Neil,
K7WK
Thank you by this clear explanation !
Friend, you have a lot of toys!
Great great great .. thank you sir .
Thanks for your informative and educational videos. It's good to know how and why something works, and not just what it does.
Terrific video - that was _exactly_ what I wanted to know, very clearly demonstrated. Many thanks.
Thank you so much Alan for teaching us this. I used a directional coupler tonight to look at a chinese fpv antenna and found out it wasn't exactly what I thought it was. All thanks to you! Mike K8MB.
Hello Alan! I do hope you don’t mind me asking a question via email than on utube?
I am unfortunately, not a real smart guy (82 yrs old!) when it comes to seeing different values of R/L in different scenarios and thus , I have confused myself and could use a bit of help if you don’t mind ?
Case one : I have a Rigol DSA815TG SpecAn along with a Mini Ckts ZFDC 20-5 DC and a highly Precision HP 50 ohm Load. I also purchased (from either a China or Russia) a
01 to 3000 MHz RF Bridge. This bridge requires an external 50 Ohm Load unlike the ZFDC that has the 3rd port terminated in a 50 ohm Load,
For the first part of this -
The Rigol was set to start QRG 1.8 MHz and stop QRG at 450 MHz (the Rigol goes to 1.5 Ghz) for this experiment-
RBW set 30 KHz - VBW set at 1 KHz
A) Using the RF Bridge, “Output to SpecAn input” - “Input to TG Output”. “Excellent 50 ohm Load on the “REF port” and nothing on the “DUT” port - then I “Normalize” the DSA815TG. (TG level set to zero db from -20db). A 10db pad is on the “Output” of the TG.
Best Results :
30 MHz R/L 59db
145 MHz R/L. 59db
450 MHz R/L. 38db
All I do now is exchange the RF Bridge for the ZFDC And renormalize again.
Best Results:
30 MHz R/L 32 dB
145 MHz R/L 31.8 dB
450 MHz R/L. 30.2 dB
Question: Why a difference of 20 db or so between the Bridge and ZFDC? Which is believable ? Or are they both correct ?
Part two (with me, there is always a part two!)
I also have. HP 8711A RF Networks Analyzer. On this unit, there is of course no need for either a bridge or DC due to it being an internal device in this unit.
I have set up the network Analyzer with same start/Stop QRG
And I use my “Precision” HP # 909F 50 ohm Load.
The Analyzer is calibrated with an open/short and load (using the same 50 ohm Load as I will be testing)
Results:
1.8 MHz. 54db
30 MHz 53db
450 MHz 50db
Alan, your thoughts? Anything will be very much appreciated!
73
David. de K8KEM
replied via direct email
Very understandable. Thank you!
But...how on Earth can it differentiate between forward & reverse signals?? Sounds like magic.
It *is* a bit of RF magic, coupled quarter wave transmission lines most often, but there are other configs with lumped elements, or coupled transformers, etc.
So could this be used with an rf probe on the reflected side to isolate an impedance mismatch in a circuit?
Just to make a point; not ALL energy is reflected back or radiated, some of the energy is being disipated as heat in dielectric and conductivity losses by the transmission line and the antenna. I believe you made a video on skin effect.
Miguel Rodriguez Good points. Skin effect isn't much of an issue at the HF frequencies where this coupler is designed to work. However, dielectric and IR losses should be taken into account for longer transmission line runs and higher frequencies.
***** One good video would be to make one just about skin effect and losses in coaxial trasmisión lines, you did mentioned it on your video #56. KE6OJE
Miguel Rodriguez I'll keep that topic on my list for future videos.
Hey I really like this video. I am considering in buying a spectrum analyzer for tuning antennas on a PCB (chip antennas). But they can be so damn expensive! So I was wondering, would a MFJ-259B do the trick? Thanks in advance!
What power rating on an attenuator would you recommend so that an antenna as a DUT doesn't drive the tracking generator by picking up arbitrary rf signals from the air?
The MFJ-259B only goes up to 470MHz, which seems a little low for PCB chip antennas. But, if this is within your frequency range, this unit works pretty well. It will give you VSWR as well as impedance and phase - it just can't distinguish between positive or negative phase angle.
It would be difficult for me to recommend an attenuation value because I don't know you're situation (how tightly coupled your antenna will be to the off-air signal, what kind of power levels you're dealing with, etc.).
Amazing! Many thanks!
James Fowler again. Misprint on the SA name. It is a 2 Ghz Siglent. I had Rogol on my mind when I sent the original comment.
Sorry
Hi James. I've never used the Siglent spectrum analyzer, so I really can't tell you why the "normalization" function is grayed out on your unit. This is a function that is used along with the Tracking Generator. Maybe you don't have the tracking generator setup/configuration completed?
@@w2aew Thanks, will double check.
Thank you for another great video. At about 6:40, you switch the load from 50ohm to 1M ohm and comment that almost all the power is now reflected. On the scope, indeed I see both the yellow voltage trace and the yellow rms voltage readout go from around 225V to 407mV, the result of the two signals adding together. FB. And I can see the blue trace showing the coupled reflected signal.
My questions: Why is the coupled signal phase shifted (about 45degrees), why isn’t the main line voltage shifted some too?
The main line isn't shifted, because the scope is triggering on that line (so it always lines up in the same place on the screen). The phase shift of the reflected signal in this case is simply due to the propagation delay back and forth through the coax.
Hi, can you explain DAS Directional Coupler 698-2700MHz, why do I have to use the coupler for DAS? instead of 3-way Splitter?
www.cablinginstall.com/wireless-5g/article/16476534/engineering-brief-explains-use-of-das-directional-couplers
Awesome Thank you 😊
I bought a directional coupler on ebay. Coaxial dynamics model 3580. The coupled ports dont have coax connection. They have two leads on each port. You can find pictures of it in Google. My question is, what and how do I measure and how do I use that to find the rf signal strength going through the main line?
I couldn't find any help anywhere and the seller also has no idea. I thought I would ask you. I watch your videos.Very educational. I am a new hobbyist in the RF field.
It's difficult to say without any kind of a data sheet. But, since it's designed for 800 MHz and the sense ports are not coaxial, I'd expect that there's probably a diode detector behind each of the sense ports, so you'd probably see a DC voltage proportional to sensed power. Might bonded a capacitor across the terminals.
Excellent video. I have a question... if I use a basic and inexpensive antenna tuner like RigExpert AA-600 to observe the tuning dip, will that be as good as the spectrum analyzer method you have used?
+Debamalya Banerjee Yes, an analyzer like this can illustrate the return loss just as well as the spectrum analyzer.
Great explanations !! I just learned something from you sir.Thanks.
Really good video, I was about to ask you to make a video about directional coupler and boom here is it. Thank you very much.
Nice video. I'm a new HAM and I'd like to characterize the 20m half-wave dipole antenna I recently installed in my attic. Can I use this technique without generating RF interference from my antenna?
+jimhollister50 Sure - any method that uses a very small amount of power would be acceptable.
That was very educational and professionally presented sir. Thank you.
question ,i have zfdc 20-2000mhz, with 0dbm connected to output and in open, cpl line=-20 all good, total reflection,with perfect termination
when i terminate with dummy load i get -45dbm thats. 25 down on an open, very good. Thing is when i connect and tune my antenna i get -55dbm, how can the antenna be better than a perfect load. cable and generator all 50 ohm
Very interesting, thank you.
Thnx ... very useful. I just received my reflection bridge and want to check my antenna's using the VNA. My reflection bridge has IN OUT and a DUT .... i should connect the antenna to DUT and the signal output of the tracking to IN. I don't quite understand your setup.
If you have a VNA, it would already have the bridge or directional coupler built in. There shouldn't be a need for an external reflection bridge (unless it is an older VNA that specifically used external bridges/couplers).
@@w2aew Interesting answer ... i have a HP 4195A .... how should i connect an antenna in that case?
@@egbertgroot2737 OK, that's an older analyzer that uses an external transmission/reflection test set. A directional coupler will sample the signal going thru the coupler from IN to OUT. Since the signal you want to measure is the reflection coming back from the antenna, you would want to connect the antenna to IN and the signal source to OUT. The manual for the HP4195A can be found here: literature.cdn.keysight.com/litweb/pdf/5950-2942.pdf?id=619880
@@w2aew Ah i understand! Very useful answer. I only have old equipment ;-) ..... thanks for your quick reply! Greetings from the Netherlands. Pe1JKU
Great video! This is the second time I watched it, and can't tell you how much I appreciate the work you do in producing these. Very helpful to us folks returning to the hobby! I do have a question. Rigol sells a "SWR Measuring Kit" for their spec analyzer that pretty much looks like one of these couplers and a few fittings stuffed into a fancy box (with matching price). Is that all it is? It looks like there might be software also, but I'm guessing that it's just minor stuff - say, calibration data and a few automation procedures - for whatever coupler they used. What do you think? Thanks again!
It is likely a directional coupler and software.
I am late to the party but great lesson and thanks! 73
gave it a try on a 2M Jpole type antenna, worked great. I'm confused about return loss bridges and when and why to use them over a directional coupler.
+Mark Butterworth Return loss bridges output a DC voltage in proportion to an impedance mismatch, while directional couplers output a sample of the RF energy flowing in a chosen direction. Either one can be used to characterize the mismatch of an antenna system - it all depends on how you want to process/measure the reflected signal.
Thanks, It was great, specially when you learned all of this just in the book
Keep going ;)
Thanks a lot for this video w2aew. Learnt a lot from it. Directional coupler is a neat device. Very nicely explained. The only thing a little unclear @10:00 is that we are viewing the coupled port correct?
Yes, the analyzer is measuring the coupled port which is sampling the signal being returned from the antenna.
Similar to my video on 978MHz antenna testing/tuning.
w5cdt Yes, nice video!
Very very useful vedeo .thanks keep it up
Excellent.
Hey,
Is the output seen in the spectrum analyzer the actual s11 curve, as the output is obtained from a different port than the input? It seems to contradict the common definition of s11.
+Pranjal Paliwal A network analyzer uses a directional coupler to measure the output and reflected power at each port - so there's basically a coupler behind each port of a network analyzer.
very clearly explain for a directional coupler
thanks
Excellent work and execution done
thanks for the video - it's the best description of the operation of a directional coupler I've found.
Hi,
I have a question. When you are testing the antenna, the signal from the tracking generator to the antenna is reflected back to it for the non-resonating frequencies. Won't this interfere with the subsequent signals sent from the tracking generator?
+Shalini Srinivasan It can, which is why an attenuator is often included in series with the TG output. However, if the end goal is to achieve a good match (no reflection), then the point is moot because there will be no reflection at the desired point.
Cannot thank you enough for this explanation.
I learn something new every time I watch this video and I’ve watched it many times 🤓 thank you
Hi Allen! Thank you for taking your time to make this excellent video! I have some questions. If I may! I now have a ZFDC 20-4 (which works for me and no -5 on eBay!) I am using a Rigol DSA815 w/Tracking Gen. From the D.C. I have the OUT going to the TG, the CPL to the SA and then with 0db i "Normalize" the TG. "Then" I attach a precision 50 ohm load to the "IN" port. I believe that this is the correct procedure to measure Return Loss. In this scenario, it appears I am seeing the R/L of the 50 ohm load. The freq start 1 MHz Stop Freq 1Ghz. Please correct my procedure if I am in error. Final question, what is the procedure for checking Directivity for the D.C. ? Thanks In advance Allen. 73's David K8KEM
In your procedure, you're using the "open" on the IN of hte D.C. to provide a 100% reflection in order to normalize the coupling factor of the D.C. This should work well enough. Then, connecting your 50 ohm load, you should see a very low (large negative number) return loss. To measure the directivity - connect the TG to the IN, SA to the CPL and 50 ohm to the OUT. You should get something that is about 20dB down (the coupling factor). You can "normalize" this trace, then swap the IN and OUT connections on the D.C., and what you see should be the directivity (about 27dB down). Directivity is the difference of the CPL response for forward and reverse signals.
w2aew again Thank you so very much Allen! I have learned so much from you! What makes your videos so great is that you speak clearly and quite distinctly and at a pace that is very good! 73's David K8KEM
Interesting,
what does RF mean exactly?
Generally a signal that is intended at some point to be sent over the air, hence Radio Frequency. Usually single-frequency signal that is modulated in some way.
get a dual directional coupler to measure reflected power. I have always been taught to terminate at the load, not at the source. have you heard this or think it makes a difference?
Yes, of course you want the load to properly terminate the line to minimize reflections.
Hello... I'm trying to find what the vswr is for a SMA to TNC RF adapter and Using your set up to find what the VSWR is from 2 to 8.0 GHZ, 8 to 16 GHZ and 16 -18 GHZ. Since the adapter is not an antenna will it work you procedure Work?
You can probably estimate it with an appropriate directional coupler and careful calibration/normalization - but it won't be as accurate as a proper VNA.
Thanks... Do you happen to know who can offer testing for our requirement? All I find is new VNA on line and no companies listing measurements services. I appreciated any help you can give us.
Thanks, very helpful video well presented.