Awesome find. I had so many of those things then my apartment complex caught fire Oct, 28 2006 and all of my ham stuff was never returned to me (along with all of my valuables). Very nice find indeed.
fantastic video again. Could you say something about the amount of Volts before the variable capacitors blow up into lightning? In other words up to which power is this matchbox useable?
+Carsten Koch I'd have to look up the voltage ratings of the caps. I think I found the specs for the smaller variable cap, and it was rated for 600V. The larger one would be more. Rating for power is a bit more complex because it would depend on the degree of mis-match - that will determine the voltages. Based on what I see, I'd expect that this tuner would work well to 100W for moderate mismatches.
I'm an extra, but have probably never seen a manual tuner in operation (only operated HF twice on resonant antennas, no balun). Learned a lot. Thank you.
Nice find Alan. I have a box of these older vari-caps and inductors that I salvaged when I was a teenager. I've been hanging onto them all these years for use in a radio project that I never have time to build. Are you aware of any manufacture that still makes either of these "old" style variables? I've seen some on ebay but they appear to be salvaged.
That is a nice little tuner. For a couple of bucks for an LED and some resistors, you could add an indicator for a matched condition. That would be nice for portable operation.
@@w2aew I would love to see this converted into a z match. I wonder if you could find a dual varicap small enough. Trying to find a good compact z match that will run more than a few watts is not easy. When i can find my vari caps i'll see what i can manage. Somewhere i have a vari ball inductor, i am wondering if it has enough inductance or if i will have to switch in extra inductance and use the vari-ball to fine tune. Something i could use at home, perhaps rated between 100-500W but something still small enough to take hiking. I've seen the micro stuff but not much available for the 50-100W range in Z-matchers.
Nice video. I have homebrewed a couple of tuners using the exact same components. Concerning the bypass switch, your schematic shows it shorting the inductor, but the caps are still connected to the transmitter and antenna terminals. Would that not add some additional Xc to the impedance the transmitter sees (unless the caps are set to minimum)? On a Tee type tuner you can use simple bypass switching, but on a Pi, it is a little more involved.-Gary N4AST
+Gary Boyles I agree - the bypass switch the original builder included is of limited usefulness because of this. You can rotate the caps to their min values, but this will still leave several pF shunting the line.
Hello Alan. Very helpful video. Is there some kind similar equipment to measure and tune a 868 Mhz antenna. Or you have to go and buy a vector network analyzer to do that . With a direcional coupler and an Spectrum Analyzer you could also do that but how you can tune to the 50 impedance without spend hours in soldering different C and L Values in the PI Network.
+Max Denort There are a few relatively low cost analyzers that would cover 868MHz. Here are a few: www.rigexpert.com/index?s=aa1000 www.arraysolutions.com/Products/AIMUHF.htm
+w2aew thanks a lot. I also found in a forum this VNA-0440. What would be your recomendation for semi professional RF-Design in 868 MHz. The VNA-0440 has 100kHz resolution, i dont know if it is a not so good spec ?
+Max Denort I'm not familiar with the VNA-0440, but from the data I just looked up online, it looks pretty decent. Without any experience with it, I can't comment any further.
Alan, I could use some advice on outfitting an RF workbench. So far i have a Rigol Ds2302A, a Tek 2465A, a Tek 2465, a Boonton RF 4210 RF microwattmeter, An RF sig gen (35Mhz to 4.4Ghz) a Rigol Arb Funct gen to 25Mhz, a Levelled sine wave Tek SG504, 6.5 Digit Rigol 3068 and a 3058 too, a couple Fluke 87Vs, a DSA 815-TG, Mastech 5308 LCR meter, some attenuators and cables and RF ends/adapters on order. Some textbooks on RF & PCB design for RF. I can do doublesided SMT PCBs down to around 10mil reliably. As an RF noob i need some advice on what else i might need to tool up to eventually do my own RF designs and products....such as sig gens, med. pwr amps and TX/RX, etc.
+Ancel UnfetteredOne Sounds to me that you're pretty well equipped from an equipment standpoint. You'll need to make sure you've got a nice selection of probes for the scopes, RF connector adapters, coax test cables, etc. You may want to add an RF sampling tee, directional coupler, and maybe a few splitter/combiners. Many people have designed a lot more, using a lot less than what you have now.
+w2aew , ok I am looking at a couple of these: www.ebay.com/itm/Mini-Circuits-Directional-Coupler-ZFDC-20-5-N-N-Type-0-1-to-2000-Mhz-/291346673928? The RF sampling Tees seem every expensive and work in a 'relative' fashion based on adjustment. It might be better to mod an actual BNC tee to do the job and 'cal' it after. Most splitter combiners seem to be 75 ohm. Any decent 50 ohm units u can suggest? The bird wattmeters & sampling Tees are nice but I think not req'd once I can attenuate the signal for the Boonton 4210 or the DSA 815. I don't need more than 5W RF or so.
+Ancel UnfetteredOne Tee's are relative, and reasonably easy to build yourself. There is a version of the Bird 43 style wattmeter that has a adjustable RF sampling tap built in - very handy. There is even a slug for the Bird 43 that is a sampling plug. Have you seen my video on RF samplers? th-cam.com/video/0Kk_N_TpDeo/w-d-xo.html
When I saw the name I was hoping it was some kind of adjust able band pass filter for the Raspberry Pi. It's been found that you can transmit short distances from the rasberry pi gpio pins, so you can play audio to an FM radio, trigger remote door bells that operate on 433mhz. The signal is very bleedy and not very fcc friendly. Some kind of nice band pass filter might be good for something like that.
+Tony T. Not sure if there were "plans", probably just decided to build a classic Pi network, and decided that the variable caps he had weren't large enough, thus added the extra compression caps. I don't like the bypass switch, because it still leaves the variable caps connected even when the inductor is bypassed.
+w2aew re: the bypass: could his feedline/antenna setup have provided enough inductance required to resonate, therefore all that's needed is capacitance?
I haven't tested it too much further yet. I suspect it'll handle 10:1 or worse mismatches on 20, maybe even on 40. I'm going to try it out on my 130' dipole.
Those variable air capacitors look to have about 1 or 2 mm spacing. How much power do you think you could send through it before arcing over (or any other component failing)?
+ladams00 The smaller cap is rated for 500V. I haven't found a spec for the larger one. Based on this, I would think it would work fine at 100W for moderate mismatches.
Why is it that the variable inductor starts with tightly wound wire one one end and switches to more widely spaced wire on the other end? Is that to get a logarithmic scale?
+pocoapoco2 To some extent, yes. At higher frequencies where the lower inductance is used, a smaller incremental change in inductance is desired for easy tuning. At lower frequencies where the higher inductance is used, a larger change in inductance per turn is desired.
That is a video distribution amplifier, used to be used in video security systems. Found at the same hamfest, also very cheap I picked it up to harvest the BNCs.
+w2aew LOL. Yep, you're a ham (even if I never knew it) I could tell cause we are all pack rats harvesting stuff for just the moment we will use them and we all know we will just might be in two or three lifetimes but who counts the minutes anyway?
+Donald D'Egidio Not precisely, but estimated them at a few hundred pF based on some quick measurements of capacitance to ground at each terminal, with the variables at their min values, and inductor at max value, noting the change in capacitance when I kicked in the switch to bring them in-circuit.
So, I understand how to tune a magnetic loop antenna to make it resonant. It is merely a long single or double looped coil in parallel with a capacitor. What I don’t understand is how an antenna tuner can make an antenna resonant through a length of coax. Is it just making the radio think the antenna is tuned for the transmit frequency? Antennas and their construction interest me because I live in a CC&R (HOA) neighborhood. I just got my general ticket and I’ve come to the realization that no antennas of any sort are allowed. They were nasty enough to including flagpoles in their not-allowed list. A neighbor up the street has a strange sculpture in their back yard. If it were shaped slightly differently, it would make a nice magnetic loop antenna. This is what I intend to do, a 6 foot double helical loop.
An antenna tuner does not make an antenna resonant. The name is misleading. A better name is a transmatch, because it is an impedance transformer that transforms the impedance of the antenna system (antenna and coax) to the impedance required to match the transmitter (usually 50ohms). It's an impedance matching device, not really a tuner. It does not change the resonant frequency of the the antenna. You may want to read up in it here: en.m.wikipedia.org/wiki/Impedance_matching# or here: www.qsl.net/va3iul/Impedance_Matching/Impedance_Matching.pdf
just a question from a newbie, why people still use the old pl259 connector while there are others way better than it (N connectors)? I know it's ok for low frequency but why bother?
+w2aew thank you very much for the answer. I'm learning a lot from your videos, maybe in the future it'd be interesting to show the performance of various connectors over the frequency range,as far as I know there aren't videos on this topic
+marco56702 This is a bit off topic, but should you decide to use Type N connectors or BNC connectors in the future, study the installation a bit. The biggest problem comes from people getting the center pin extended too far. It should not be beyond the internal ground ring in the connector. If it is longer than that, you risk splitting the female connector. Conversely if you don't get the shield pushed far enough into the connector, contraction of the materials will pull the center pin back. I have seen many connectors put on with the pin at an angle to the center conductor. Again this will split the female connector. Finally when putting the connectors together, you should be holding the body from turning and only screw on the ring. Twisting the body will eventually damage the male/female connection. This becomes a bigger problem as you increase frequency. I worked in the industry for 30 years and have repaired/replaced many poor installations made by "professionals". The N connector makes a much better connection when properly installed, but you won't really notice a difference until you get beyond VHF. Someone else mentioned cost. It is hard to beat the old PL-259 for price. Connectors add up fast on a big job. Sorry about the longwinded tutorial on an off topic.
Yep, agree with you. Although I think it would be easy to solve this issue replacing the featured switch by a DPDT switch. One at the input connector and the other at the output connector. One side bypassing the signal, the other inserting the PI in the signal path. I hope I my message is clear. 73 de CT7AFR, Emmanuel.
Awesome find. I had so many of those things then my apartment complex caught fire Oct, 28 2006 and all of my ham stuff was never returned to me (along with all of my valuables).
Very nice find indeed.
Looking forward to your impedance matching series! Especially about ANT->PreAmp, Osc->Buffer, Filters->RF Amps! Your videos are always helpful!
Love the variable roller inductor, first time I've ever seen own.
Nice.
fantastic video again.
Could you say something about the amount of Volts before the variable capacitors blow up into lightning? In other words up to which power is this matchbox useable?
+Carsten Koch I'd have to look up the voltage ratings of the caps. I think I found the specs for the smaller variable cap, and it was rated for 600V. The larger one would be more. Rating for power is a bit more complex because it would depend on the degree of mis-match - that will determine the voltages. Based on what I see, I'd expect that this tuner would work well to 100W for moderate mismatches.
I'm an extra, but have probably never seen a manual tuner in operation (only operated HF twice on resonant antennas, no balun). Learned a lot. Thank you.
Nice find Alan, always a great experience when you spot a jewel amongst the rough! 73 - Dino KL0S
Nice find Alan. I have a box of these older vari-caps and inductors that I salvaged when I was a teenager. I've been hanging onto them all these years for use in a radio project that I never have time to build. Are you aware of any manufacture that still makes either of these "old" style variables? I've seen some on ebay but they appear to be salvaged.
One of the only ones I'm aware of is Viking, formally Cardwell. cardwellcondenser.com/
Also found this one for the caps.
www.orenelliottproducts.com/index-1.html
*****
Thanks much Alan. It is appreciated!
+bain5872 This store has some pretty nice offerings:
www.ebay.com/sch/rfamp/m.html?_nkw=&_armrs=1&_ipg=&_from=
That is a nice little tuner. For a couple of bucks for an LED and some resistors, you could add an indicator for a matched condition. That would be nice for portable operation.
+Stephen Moore I've got a similar SWR indicator on my Z-match QRP tuner.
@@w2aew I would love to see this converted into a z match. I wonder if you could find a dual varicap small enough. Trying to find a good compact z match that will run more than a few watts is not easy. When i can find my vari caps i'll see what i can manage. Somewhere i have a vari ball inductor, i am wondering if it has enough inductance or if i will have to switch in extra inductance and use the vari-ball to fine tune. Something i could use at home, perhaps rated between 100-500W but something still small enough to take hiking. I've seen the micro stuff but not much available for the 50-100W range in Z-matchers.
Nice video. I have homebrewed a couple of tuners using the exact same components. Concerning the bypass switch, your schematic shows it shorting the inductor, but the caps are still connected to the transmitter and antenna terminals. Would that not add some additional Xc to the impedance the transmitter sees (unless the caps are set to minimum)? On a Tee type tuner you can use simple bypass switching, but on a Pi, it is a little more involved.-Gary N4AST
+Gary Boyles I agree - the bypass switch the original builder included is of limited usefulness because of this. You can rotate the caps to their min values, but this will still leave several pF shunting the line.
Hello Alan. Very helpful video. Is there some kind similar equipment to measure and tune a 868 Mhz antenna. Or you have to go and buy a vector network analyzer to do that . With a direcional coupler and an Spectrum Analyzer you could also do that but how you can tune to the 50 impedance without spend hours in soldering different C and L Values in the PI Network.
+Max Denort There are a few relatively low cost analyzers that would cover 868MHz. Here are a few:
www.rigexpert.com/index?s=aa1000
www.arraysolutions.com/Products/AIMUHF.htm
+w2aew thanks a lot. I also found in a forum this VNA-0440. What would be your recomendation for semi professional RF-Design in 868 MHz. The VNA-0440 has 100kHz resolution, i dont know if it is a not so good spec ?
+Max Denort I'm not familiar with the VNA-0440, but from the data I just looked up online, it looks pretty decent. Without any experience with it, I can't comment any further.
Alan, I could use some advice on outfitting an RF workbench. So far i have a Rigol Ds2302A, a Tek 2465A, a Tek 2465, a Boonton RF 4210 RF microwattmeter, An RF sig gen (35Mhz to 4.4Ghz) a Rigol Arb Funct gen to 25Mhz, a Levelled sine wave Tek SG504, 6.5 Digit Rigol 3068 and a 3058 too, a couple Fluke 87Vs, a DSA 815-TG, Mastech 5308 LCR meter, some attenuators and cables and RF ends/adapters on order. Some textbooks on RF & PCB design for RF. I can do doublesided SMT PCBs down to around 10mil reliably. As an RF noob i need some advice on what else i might need to tool up to eventually do my own RF designs and products....such as sig gens, med. pwr amps and TX/RX, etc.
+Ancel UnfetteredOne Sounds to me that you're pretty well equipped from an equipment standpoint. You'll need to make sure you've got a nice selection of probes for the scopes, RF connector adapters, coax test cables, etc. You may want to add an RF sampling tee, directional coupler, and maybe a few splitter/combiners. Many people have designed a lot more, using a lot less than what you have now.
+w2aew , ok I am looking at a couple of these: www.ebay.com/itm/Mini-Circuits-Directional-Coupler-ZFDC-20-5-N-N-Type-0-1-to-2000-Mhz-/291346673928?
The RF sampling Tees seem every expensive and work in a 'relative' fashion based on adjustment. It might be better to mod an actual BNC tee to do the job and 'cal' it after. Most splitter combiners seem to be 75 ohm. Any decent 50 ohm units u can suggest? The bird wattmeters & sampling Tees are nice but I think not req'd once I can attenuate the signal for the Boonton 4210 or the DSA 815. I don't need more than 5W RF or so.
+Ancel UnfetteredOne Tee's are relative, and reasonably easy to build yourself. There is a version of the Bird 43 style wattmeter that has a adjustable RF sampling tap built in - very handy. There is even a slug for the Bird 43 that is a sampling plug. Have you seen my video on RF samplers?
th-cam.com/video/0Kk_N_TpDeo/w-d-xo.html
AG6AV here. I would like videos on impedance matching using various matching networks. Thanks for the content Allan!
I would love some more videos on the subject. You should do one on a tuner like the MFJ 16010 (I'm pretty sure it is a L tuner)
Thanks for taking the time to show your find and your test. 73.
I would like to see the effect of the capacitors and coil on the smith chart on the NanoVNA.
Look at this video - it uses a different VNA but you'll see the same thing: th-cam.com/video/gw1TYWwfvGk/w-d-xo.html
When I saw the name I was hoping it was some kind of adjust able band pass filter for the Raspberry Pi. It's been found that you can transmit short distances from the rasberry pi gpio pins, so you can play audio to an FM radio, trigger remote door bells that operate on 433mhz. The signal is very bleedy and not very fcc friendly. Some kind of nice band pass filter might be good for something like that.
Agreed, but sorry, this isn't the filter you're looking for.
Great find, Great unit! I tip my hat to the builder, and you, for showing it and it's operation. Maybe he worked off plans from a ARRL Handbook?
+Tony T. Not sure if there were "plans", probably just decided to build a classic Pi network, and decided that the variable caps he had weren't large enough, thus added the extra compression caps. I don't like the bypass switch, because it still leaves the variable caps connected even when the inductor is bypassed.
+w2aew re: the bypass: could his feedline/antenna setup have provided enough inductance required to resonate, therefore all that's needed is capacitance?
Could be.
Nice find! How well does it work with a further mismatched load?
I haven't tested it too much further yet. I suspect it'll handle 10:1 or worse mismatches on 20, maybe even on 40. I'm going to try it out on my 130' dipole.
Those variable air capacitors look to have about 1 or 2 mm spacing. How much power do you think you could send through it before arcing over (or any other component failing)?
+ladams00 The smaller cap is rated for 500V. I haven't found a spec for the larger one. Based on this, I would think it would work fine at 100W for moderate mismatches.
Why is it that the variable inductor starts with tightly wound wire one one end and switches to more widely spaced wire on the other end? Is that to get a logarithmic scale?
+pocoapoco2 To some extent, yes. At higher frequencies where the lower inductance is used, a smaller incremental change in inductance is desired for easy tuning. At lower frequencies where the higher inductance is used, a larger change in inductance per turn is desired.
Neat find, Alan. I always enjoy your videos. BTW, what is that box with 80 BNCs in the background?
That is a video distribution amplifier, used to be used in video security systems. Found at the same hamfest, also very cheap I picked it up to harvest the BNCs.
+w2aew LOL. Yep, you're a ham (even if I never knew it) I could tell cause we are all pack rats harvesting stuff for just the moment we will use them and we all know we will just might be in two or three lifetimes but who counts the minutes anyway?
+w2aew Might be worth covering the differences between 50 and 75 ohm BNCs sometime and how they can/can't be interchanged. 73 - Dino KL0S
+Dino Papas Good topic for the future.
Dino Papas
I don't think I have ever seen a 50 ohm BNC as they are all those smaller 75 ohm types.
Alan
Did you determine the values of the trimmer caps?
Don WB3BJU
+Donald D'Egidio Not precisely, but estimated them at a few hundred pF based on some quick measurements of capacitance to ground at each terminal, with the variables at their min values, and inductor at max value, noting the change in capacitance when I kicked in the switch to bring them in-circuit.
That's a nice size tuner!
So, I understand how to tune a magnetic loop antenna to make it resonant. It is merely a long single or double looped coil in parallel with a capacitor. What I don’t understand is how an antenna tuner can make an antenna resonant through a length of coax. Is it just making the radio think the antenna is tuned for the transmit frequency?
Antennas and their construction interest me because I live in a CC&R (HOA) neighborhood. I just got my general ticket and I’ve come to the realization that no antennas of any sort are allowed. They were nasty enough to including flagpoles in their not-allowed list. A neighbor up the street has a strange sculpture in their back yard. If it were shaped slightly differently, it would make a nice magnetic loop antenna. This is what I intend to do, a 6 foot double helical loop.
An antenna tuner does not make an antenna resonant. The name is misleading. A better name is a transmatch, because it is an impedance transformer that transforms the impedance of the antenna system (antenna and coax) to the impedance required to match the transmitter (usually 50ohms). It's an impedance matching device, not really a tuner. It does not change the resonant frequency of the the antenna. You may want to read up in it here:
en.m.wikipedia.org/wiki/Impedance_matching# or here: www.qsl.net/va3iul/Impedance_Matching/Impedance_Matching.pdf
Hi Alan, Thanks for this video.
Looking forward to a video about T, PI and L networks basics theory and design tips.
73 de CT7AFR, Emmanuel.
Alan, time for Smith Chart tutarial!
i'm guessing something like this could be built to create an input tuner for an amp.
+dale myers That is certainly one use for it.
just a question from a newbie, why people still use the old pl259 connector while there are others way better than it (N connectors)? I know it's ok for low frequency but why bother?
+marco56702 Probably because they're cheap and "good enough".
+w2aew Plus most people can' put them on properly, and they are delicate. As stated, the PL-259's are good enough.
+Stephen Moore ah ok, thank you very much for the answer.
+w2aew thank you very much for the answer. I'm learning a lot from your videos, maybe in the future it'd be interesting to show the performance of various connectors over the frequency range,as far as I know there aren't videos on this topic
+marco56702 This is a bit off topic, but should you decide to use Type N connectors or BNC connectors in the future, study the installation a bit. The biggest problem comes from people getting the center pin extended too far. It should not be beyond the internal ground ring in the connector. If it is longer than that, you risk splitting the female connector. Conversely if you don't get the shield pushed far enough into the connector, contraction of the materials will pull the center pin back. I have seen many connectors put on with the pin at an angle to the center conductor. Again this will split the female connector. Finally when putting the connectors together, you should be holding the body from turning and only screw on the ring. Twisting the body will eventually damage the male/female connection. This becomes a bigger problem as you increase frequency. I worked in the industry for 30 years and have repaired/replaced many poor installations made by "professionals". The N connector makes a much better connection when properly installed, but you won't really notice a difference until you get beyond VHF. Someone else mentioned cost. It is hard to beat the old PL-259 for price. Connectors add up fast on a big job. Sorry about the longwinded tutorial on an off topic.
If I use a pi tuner with a QRP transmitter, do I still need to include the low pass filter?
Maybe, maybe not. It all depends what the harmonics look like after the tuner.
Even even when by past those two capacitors are still in parallel with the antenna is that a problem
Yes, it can be. The bypass function of this homebrew tuner was not done properly.
I like that tuner. The parts would cost a lot more than $15. I use my MFJ-259C a lot.
Lucky Dog! A great Hamfest find!
Thats such a score wish I could get such an amazing tuner for such a low price.
I don't like the bypass choice. It leaves the caps connected, so not a true bypass.
+Kevin Loughin I agree entirely - the bypass isn't a true bypass. It looks like the builder didn't put much thought into it.
Yep, agree with you. Although I think it would be easy to solve this issue replacing the featured switch by a DPDT switch. One at the input connector and the other at the output connector. One side bypassing the signal, the other inserting the PI in the signal path.
I hope I my message is clear.
73 de CT7AFR, Emmanuel.
+CT7AFR Yes, this is a better way to implement the bypass.
That was good. Thank you. It exercized my teoretical only knowledge of antennas.
So elegant solution.
damn. I thought it had something to do with a raspberry PI.
Cheers
$15?! That ham must have a pile of roller inductors (and cash) sitting around.
Oddly, he really didn't know what he had.
i like pumpkin pi
I'm jealous - I want something like that for my shack.
Excellent ! Thank you ! 73 WA7AXT
Whoever built that little tuner knew their stuff. Excellent work - and a great demonstration video. de: KE7LOY - I'm a homebrewer.