This was an excellent video! I built almost the same setup yesterday and wanted to share my experience in case it's helpful for anyone. I used Yeasu FT991A and RSPdx (but first tested with RTL SDR v3 dongle). Instead of this MFJ unit, I used the equivalent unbranded T/R switch from Banggood ($45 in May 2023). I also built my own PTT cable by soldering 2 wires to a 8 pin mini DIN connector and using a 3.5mm mono jack at the other end. For the 991A I soldered Pin 2 (TX GND) to the tip of the jack and pin 3 (GND) to the base of the jack. The pinout can be found in the Yeasu manual. I agree that using a cable is better than relying on any RF sensing technology. Regarding your questions: the most important one in my opinion is about protecting the SDR. What I found is that when transmitting the SDR does pick up your own signal (the other part of the band is clearly being suppressed). However the signal is shown in SDR Uno at around (-50 dBm in my case). SDR Play have a video on their youtube channel about protecting the SDR when in close proximity to transmissions. It covers several scenarios with examples. They say that at 0dBm or above the SDR may be damaged. The video is titled "Protecting Your RSP from Near-field Coupling". The video also shows instructions on how to measure and protect the SDR. I also experienced that using this TR switch from Banggood is not realistic on 145MHz due to very high SWR. Others have reported this in the video made by Tech Minds titled "PANADAPTER For Any Radio DC - 160 MHz SDR Antenna Switch". I didn't experience any issues when testing in on the 10m band. The 991A can indeed be controlled by SDR Uno through the use of omni-rig. To do this, both the 991a and the RSPdx must be connected to the computer using separate USB cables.
Hi Richard, thanks for the kind words, I do training where I work and I like putting together these, a lot of the stuff I do to help me see and understand, Power Point is my friend and I really appreciate the feedback, let me know if there's anything you need '73
There is no such risk if you engage any substantial transmit delay on the transceiver. The relay will switch the SDR out when the 12 v key line is activated - the transceiver delays actually transmitting for x milliseconds set in the MENU system. No worries on hot switching. The REAL CONCERN is the device is very poorly isolated and the SDR continues to receive during transmission. In other words, when you transmit, there is substantial coupling between the transmitter and the SDR receiver - not quite enough to negate the purpose of the switch device, but it still couples a LOT of energy and this is easily seen on videos demonstrating the switch. While it disconnects the SDR, the SDR still picks up a strong transmit signal - view the other videos and see the bright line on the SDR display whilst transmitting. So, set sufficient transmit delay to allow the relay to do its thing and avoid hot switching the relay, and build your own switch for less money with a simple relay that activates on the radio's 12v key line making sure it has more isolation than the MFJ product. Just MY take. Good luck. TRT
I've also been mulling over this option for my IC-7100 with my RSPdx using Win4Icom Suite for several months. I returned the MFJ-1708 once because I didn't realize I had the wrong cable connecting the 13 pin jack on the radio to the 1708. Right now I just have RF limiters hooked on to the antenna inputs of the RSPdx and using the Win4Icom as the panadapter. I don't get more than +20 on the SDRuno S meter. I understand that the S meter could go as high as S50 before the dx is threatened. That reading is while transmitting on 2 meters while the SDR is just using an MLA-30 HF antenna. If both rigs were operating on the same band antennas no doubt the S reading would be much higher. I keep delaying my decision realizing I'd either have to buy TWO MFJ-1708s ($280+) or switch cables around each time I switch from HF to VHF/UHF or back. Not sure the cost is worth the Benitez. At least you have a version of a waterfall with your rig. Have you done anything with this project since your last comment?
Good evening sir, thanks for the message, to be honest I did not go any further with this project, my concern was with a 50 Ohm feedline, if I put the MFJ and the FT991A on the same coax this would no longer be 50 ohms and to be honest I really didn't want to try anything on the new FT991A, so I ended up not going any further, sorry I can't be more help I just never really like this whole setup. Thanks for the message and let me know if there's anything else I can do for you '73 sir!!
Another option would be to simply run the SDR using a separate antenna, perhaps a small Active Antenna on the the other side of the property (reasonably far from the transmitting antenna). Especially if you're using the SDR to feed the Spectrum display or Waterfall, where you'll not be seeing very much of the very weakest signals anyway (an argument that perhaps you don't actually need a share of the primary antenna). Note, all this is speculation.
seeing this 2yrs post and curious what solution there is for the ctrl cable IF the tun/lin 8pin is already occupied by a automatic tuner and/or amplifier?
If you are set on using the same antenna then this seems like a safe way to protect the SDR. You could also utilize the additional antenna inputs and possibly try to get cat control to change sdr antenna input on yaesu transmit. Virtual comm ports amd/or omnirig maybe???
Hi Phillip, thanks for the message, one of the concerns is in receiving with receiver this would create a impendence mis-match instead of 50 ohms I think you would have 25 ohms, not sure how that would impact the radio receive quality, i never ended up using this I found the FT991A waterfall to be adequate for the job. Thanks for the message appreciate hearing from everyone👍
@@westtexasvideogateski5juf255 I'm going to assume the MFJ splitter is transformer based so impedance would remain 50 ohms. At a minimum it should be 50 ohm in transmit with SDR port switched to ground. Also best to always use PTT cable and have the RF sense as a backup, just in case. There are a few projects online of panadapters using embedded RTL-SDRs in the 991A too on Hackaday and RTL-SDR Blog. 73 de AC5G
This is what I want to setup. The RSPdx is incredibly sensitive and you can pick out signals that don't show in the waterfall. Your not hallucinating and Yaesu with a good antenna can transmit to them. It is very sensitive to adjacent transmitters so the switch is required. The SDRPlay had great input protection but you'll have to send it back to have the diodes replaced it you got them with more +15db for too long.
I have the 991a, the RSPdx and the MFJ1708. I wanted the experience of a bigger waterfall, not interested in transmitting...yet. My findings and, as you mentioned earlier in the video, you're basically seeing the waterfall of what the SDR (RSPdx) sees and not neccesarily, the signals seen in the 991a. Huge letdown to me. Decided to return the MFJ1708 and wait to upgrade to an FTDX-10 alter down the line.
How you doing, thanks for the message, yeah I understand I never executed this project, there's a whole different aspect I did not mention working on a video now on the fact when you connect the SDR and your radio to the same 50 Ohm Antenna System there is a impedance issue being in Parallel which both are no longer at 50 Ohms. Have a good evening and thanks for the message 73
I have the exact setup, 992a, rspdx,1708, win for yaesu. Make sure you use the newest best model of 1708 sdr sma for rspdx with the cable to activate it. Its 4 real realays. I use same antenna no problem at all 2 years now. I use resonant antennas that switch on one antenna. It defaults to the sdr when no tx. Sdr console has a protection system for overloading as a back up for strong signals. I do put an A-B switch on the uhf vhf side to disconnect a to b position is open when operating hf possibly over kill by the way the sencing Part of the 1708 works also no arks . Also use omni rig with your rig control and turn it on in sdr uno. No matter where you tune the other one follows. Never us the old mfj 1708 switches it would be a problem. Love my 991a ! Chuck AA4CP FORT PIERCE FL
I think you are talking about the MFJ-1708, it is a relay device that allows you to attach your SDR (sdrplay RSPdx as an example) to your antenna. When you transmit, the sdr input is grounded to prevent damage.
Hi Chris, I'm embarrassed I got my part numbers reverse, I just corrected the description it now reflects the correct MFJ part number. I apricate you pointing that out - have you done this using the MFJ 1708 and if you did how do you like it? Again I apricate the correction and '73 de Ki5JUf sir!!
As always, nice detailed videos, Good thinking on your part. However how about installing a receive antenna only to the SDR if space allows it, keeping it all separated..
If you have common transmit frequencies, using a bandpass filter, nullifying those for your receive antenna, will alleviate any switching component that takes far too long before engaging.
Whenever I start researching something to do with my 991a you make a vid. Its uncanny. I won a sdrp-rsp1a in a foxhunt & looking at same scenario. I've been looking at that mfj switch, hadn't thought of the cable yet. DXE-RTR-2 do the same thing?
Good afternoon, well to be honest I never went any further with this project and I see no advantage other than getting the waterfall from the SDR on a computer screen, the FT991A already has the water fall. I like using the same radio for transmit and receive, this project got put on the back shelf. Thanks for the message '73
You can plug an RJ45 cable into the open connection on your MD-100 Microphone. there are two pins where You pick up the PTT from the mic, and use that to switch the relay. I have the same setup as you, FT991a, and MD100 and do it that way. I don't trust the RF sensing, use the PTT
Hi Chris, thanks again I appreciate the information and tips, there are still many aspects of this project scope I'm trying to get comfortable. My email is shope02@yahoo.com send me any notes you have. I want to peruse your idea it seems to be a better solution. I was looking for a setting under the "Menu/Setup" that might allow me to send that Transmit to Ground sooner before the actual radio went into transmits to allow the relay to get situated. Again '73 de KI5JUG sir
Good video and explanation, thank you. I'm about to do this as well, however I would NEVER trust an MFJ (bargain basement vendor) product to do it, so I'm looking at other vendors with similar products.
Hi Vincent, that's great I never actually did this and I'm glad the video helped, let me know what you do I might be curious to do something similar '73 and have a great weekend!
Interesting. I've had a 991a for a little over a year, but have been real busy in '21. Now, I'm looking to get my General and get more into HF and you have my interest piqued!
Hi Lee, how you doing did you get your General? Let me know of there's anything I can do for you I just recently passed my Extra, let me tell that took every brain cell I had to pass that one, anyway let me know how you did, I mostly work 10 and 6 and local VHF repeaters here in Abilene. '73 my friend keep in touch
@@westtexasvideogateski5juf255 Congrats on the Extra! I did get my General back in Feb. I dabble w/ FT8 mostly on 10-20M, but am always looking at ways to better my antenna setup (it's in the attic of my condo). How's that MFJ-1708 working out for you?
Steve, Just checking have you added the SDR to your setup? If so I don't see a video of it. Also which do you like better Ham Radio Deluxe or Win4Yaesu with the FT991A? Great job on your video's. KD9SZQ 73's
Hi Tim, Thanks for the message, I decided not to do that at this time, budget reasons at that time I've started a path down CW and HRD so that's I've been up to, appreciated your message and apricate you checking in - hope you had a nice xmas and new years '73 de KI5JUF keep in touch
With the ft991a you have 2 antenna terminals to protect , you can run a second mfj 1708 to protect the vhf uhf antenna side with a separate recieve antenna connected see video below
I use this setup all the time with the cable from my FY-991A. I use the waterfall built in to Win4Yuaesu. I had to mod the MFJ device by shorting the Antenna and Transmitter connectors.
Good evening sir and thanks for the message, I have since realized the impedance mismatch and I never actually did this project, I never liked the idea of having a micro relay on the TX and RX, again thanks for the message I appreciate your feedback good info for all '73 de KI5JUF
@@westtexasvideogateski5juf255 Is this why some people choose to tap into the IF circuit of the 991A to feed the signal to their SDRs? I too am researching these methods to see which way I want to go, so I THINK that the IF tapping method would get rid of the issues of reduced RX signal strengths in both the radio and SDR. But won't the SDR's RX still get overloaded during the radio's transmit? So is the MFJ T/R switch still needed for that??? I'm assuming I'll be using CAT control to keep both VFOs in sync, although I can see some use-cases where I'd want to be monitoring X band while working Y band. Any input would be appreciated!
Omnirig software will let rsp control your transceiver. I’ve been doing the same research, would like to use a small tv to monitor SDR UNO and control my 991A. Thanks for the video ! K5EGD (Haven’t pulled the trigger yet)
Also, if you're using the RF Sensing Relay just as an RF Relay (controlled with the 'TX GND' signal), then you don't need the RF Sensing function, so just buy a much cheaper plain and simple RF Relay.
This was an excellent video! I built almost the same setup yesterday and wanted to share my experience in case it's helpful for anyone. I used Yeasu FT991A and RSPdx (but first tested with RTL SDR v3 dongle). Instead of this MFJ unit, I used the equivalent unbranded T/R switch from Banggood ($45 in May 2023). I also built my own PTT cable by soldering 2 wires to a 8 pin mini DIN connector and using a 3.5mm mono jack at the other end. For the 991A I soldered Pin 2 (TX GND) to the tip of the jack and pin 3 (GND) to the base of the jack. The pinout can be found in the Yeasu manual. I agree that using a cable is better than relying on any RF sensing technology.
Regarding your questions: the most important one in my opinion is about protecting the SDR. What I found is that when transmitting the SDR does pick up your own signal (the other part of the band is clearly being suppressed). However the signal is shown in SDR Uno at around (-50 dBm in my case). SDR Play have a video on their youtube channel about protecting the SDR when in close proximity to transmissions. It covers several scenarios with examples. They say that at 0dBm or above the SDR may be damaged. The video is titled "Protecting Your RSP from Near-field Coupling". The video also shows instructions on how to measure and protect the SDR.
I also experienced that using this TR switch from Banggood is not realistic on 145MHz due to very high SWR. Others have reported this in the video made by Tech Minds titled "PANADAPTER For Any Radio DC - 160 MHz SDR Antenna Switch". I didn't experience any issues when testing in on the 10m band.
The 991A can indeed be controlled by SDR Uno through the use of omni-rig. To do this, both the 991a and the RSPdx must be connected to the computer using separate USB cables.
A very well thought out and very excellent presentation. Corporate quality.
Hi Richard, thanks for the kind words, I do training where I work and I like putting together these, a lot of the stuff I do to help me see and understand, Power Point is my friend and I really appreciate the feedback, let me know if there's anything you need '73
There is no such risk if you engage any substantial transmit delay on the transceiver. The relay will switch the SDR out when the 12 v key line is activated - the transceiver delays actually transmitting for x milliseconds set in the MENU system. No worries on hot switching. The REAL CONCERN is the device is very poorly isolated and the SDR continues to receive during transmission. In other words, when you transmit, there is substantial coupling between the transmitter and the SDR receiver - not quite enough to negate the purpose of the switch device, but it still couples a LOT of energy and this is easily seen on videos demonstrating the switch. While it disconnects the SDR, the SDR still picks up a strong transmit signal - view the other videos and see the bright line on the SDR display whilst transmitting. So, set sufficient transmit delay to allow the relay to do its thing and avoid hot switching the relay, and build your own switch for less money with a simple relay that activates on the radio's 12v key line making sure it has more isolation than the MFJ product. Just MY take. Good luck. TRT
Thanks for the feedback - appreciate it
I've also been mulling over this option for my IC-7100 with my RSPdx using Win4Icom Suite for several months.
I returned the MFJ-1708 once because I didn't realize I had the wrong cable connecting the 13 pin jack on the radio to the 1708. Right now I just have RF limiters hooked on to the antenna inputs of the RSPdx and using the Win4Icom as the panadapter. I don't get more than +20 on the SDRuno S meter. I understand that the S meter could go as high as S50 before the dx is threatened. That reading is while transmitting on 2 meters while the SDR is just using an MLA-30 HF antenna. If both rigs were operating on the same band antennas no doubt the S reading would be much higher.
I keep delaying my decision realizing I'd either have to buy TWO MFJ-1708s ($280+) or switch cables around each time I switch from HF to VHF/UHF or back. Not sure the cost is worth the Benitez. At least you have a version of a waterfall with your rig.
Have you done anything with this project since your last comment?
Good evening sir, thanks for the message, to be honest I did not go any further with this project, my concern was with a 50 Ohm feedline, if I put the MFJ and the FT991A on the same coax this would no longer be 50 ohms and to be honest I really didn't want to try anything on the new FT991A, so I ended up not going any further, sorry I can't be more help I just never really like this whole setup. Thanks for the message and let me know if there's anything else I can do for you '73 sir!!
Another option would be to simply run the SDR using a separate antenna, perhaps a small Active Antenna on the the other side of the property (reasonably far from the transmitting antenna). Especially if you're using the SDR to feed the Spectrum display or Waterfall, where you'll not be seeing very much of the very weakest signals anyway (an argument that perhaps you don't actually need a share of the primary antenna). Note, all this is speculation.
seeing this 2yrs post and curious what solution there is for the ctrl cable IF the tun/lin 8pin is already occupied by a automatic tuner and/or amplifier?
If you are set on using the same antenna then this seems like a safe way to protect the SDR. You could also utilize the additional antenna inputs and possibly try to get cat control to change sdr antenna input on yaesu transmit. Virtual comm ports amd/or omnirig maybe???
Hi Phillip, thanks for the message, one of the concerns is in receiving with receiver this would create a impendence mis-match instead of 50 ohms I think you would have 25 ohms, not sure how that would impact the radio receive quality, i never ended up using this I found the FT991A waterfall to be adequate for the job. Thanks for the message appreciate hearing from everyone👍
@@westtexasvideogateski5juf255
I'm going to assume the MFJ splitter is transformer based so impedance would remain 50 ohms. At a minimum it should be 50 ohm in transmit with SDR port switched to ground. Also best to always use PTT cable and have the RF sense as a backup, just in case.
There are a few projects online of panadapters using embedded RTL-SDRs in the 991A too on Hackaday and RTL-SDR Blog.
73 de AC5G
@@TX_AC5G Thanks good feedback keep in touch let me now how things are going '73
This is what I want to setup. The RSPdx is incredibly sensitive and you can pick out signals that don't show in the waterfall. Your not hallucinating and Yaesu with a good antenna can transmit to them. It is very sensitive to adjacent transmitters so the switch is required. The SDRPlay had great input protection but you'll have to send it back to have the diodes replaced it you got them with more +15db for too long.
I have the 991a, the RSPdx and the MFJ1708.
I wanted the experience of a bigger waterfall, not interested in transmitting...yet.
My findings and, as you mentioned earlier in the video, you're basically seeing the waterfall of what the SDR (RSPdx) sees and not neccesarily, the signals seen in the 991a.
Huge letdown to me. Decided to return the MFJ1708 and wait to upgrade to an FTDX-10 alter down the line.
How you doing, thanks for the message, yeah I understand I never executed this project, there's a whole different aspect I did not mention working on a video now on the fact when you connect the SDR and your radio to the same 50 Ohm Antenna System there is a impedance issue being in Parallel which both are no longer at 50 Ohms. Have a good evening and thanks for the message 73
I have the exact setup, 992a, rspdx,1708, win for yaesu.
Make sure you use the newest best model of 1708 sdr sma for rspdx with the cable to activate it. Its 4 real realays. I use same antenna no problem at all 2 years now. I use resonant antennas that switch on one antenna. It defaults to the sdr when no tx. Sdr console has a protection system for overloading as a back up for strong signals. I do put an A-B switch on the uhf vhf side to disconnect a to b position is open when operating hf possibly over kill by the way the sencing
Part of the 1708 works also no arks .
Also use omni rig with your rig control and turn it on in sdr uno. No matter where you tune the other one follows. Never us the old mfj 1708 switches it would be a problem. Love my 991a !
Chuck AA4CP
FORT PIERCE FL
Thanks and '73 hope to catch you on the air
Excellent video
I think you are talking about the MFJ-1708, it is a relay device that allows you to attach your SDR (sdrplay RSPdx as an example) to your antenna. When you transmit, the sdr input is grounded to prevent damage.
Hi Chris, I'm embarrassed I got my part numbers reverse, I just corrected the description it now reflects the correct MFJ part number. I apricate you pointing that out - have you done this using the MFJ 1708 and if you did how do you like it? Again I apricate the correction and '73 de Ki5JUf sir!!
As always, nice detailed videos, Good thinking on your part. However how about installing a receive antenna only to the SDR if space allows it, keeping it all separated..
Good evening sir, thanks for the complements, I looked the separate receive antenna option, I like it, thanks again '73 de Ki5JUF
If you have common transmit frequencies, using a bandpass filter, nullifying those for your receive antenna, will alleviate any switching component that takes far too long before engaging.
Whenever I start researching something to do with my 991a you make a vid. Its uncanny. I won a sdrp-rsp1a in a foxhunt & looking at same scenario. I've been looking at that mfj switch, hadn't thought of the cable yet. DXE-RTR-2 do the same thing?
Dx engineering has a s several of the same things but much more expensive for the good ones around 200 usd
I am confused. Why would you want SDR when radio receives? What is the advantage?
Good afternoon, well to be honest I never went any further with this project and I see no advantage other than getting the waterfall from the SDR on a computer screen, the FT991A already has the water fall. I like using the same radio for transmit and receive, this project got put on the back shelf. Thanks for the message '73
You can plug an RJ45 cable into the open connection on your MD-100 Microphone. there are two pins where You pick up the PTT from the mic, and use that to switch the relay. I have the same setup as you, FT991a, and MD100 and do it that way. I don't trust the RF sensing, use the PTT
Hi Chris, thanks again I appreciate the information and tips, there are still many aspects of this project scope I'm trying to get comfortable. My email is shope02@yahoo.com send me any notes you have. I want to peruse your idea it seems to be a better solution. I was looking for a setting under the "Menu/Setup" that might allow me to send that Transmit to Ground sooner before the actual radio went into transmits to allow the relay to get situated. Again '73 de KI5JUG sir
The cable you have to purchase separately directly switches the newer 1708 switch, also rf sinking is a backup at the same time
Good video and explanation, thank you. I'm about to do this as well, however I would NEVER trust an MFJ (bargain basement vendor) product to do it, so I'm looking at other vendors with similar products.
Hi Vincent, that's great I never actually did this and I'm glad the video helped, let me know what you do I might be curious to do something similar '73 and have a great weekend!
ive been waching videos all afternoon. still a coin toss on the MFJ or the chinese one on amazon.
can you explain what the AUX used for on the 1708b-sdr
AUX is an output that mirrors the control input. You can use it to key your amplifier.
@@richkelley5112 yep figured it out thanks for getting back
Interesting. I've had a 991a for a little over a year, but have been real busy in '21. Now, I'm looking to get my General and get more into HF and you have my interest piqued!
Hi Lee, how you doing did you get your General? Let me know of there's anything I can do for you I just recently passed my Extra, let me tell that took every brain cell I had to pass that one, anyway let me know how you did, I mostly work 10 and 6 and local VHF repeaters here in Abilene. '73 my friend keep in touch
@@westtexasvideogateski5juf255 Congrats on the Extra! I did get my General back in Feb. I dabble w/ FT8 mostly on 10-20M, but am always looking at ways to better my antenna setup (it's in the attic of my condo). How's that MFJ-1708 working out for you?
Steve, Just checking have you added the SDR to your setup? If so I don't see a video of it. Also which do you like better Ham Radio Deluxe or Win4Yaesu with the FT991A? Great job on your video's. KD9SZQ 73's
Hi Tim, Thanks for the message, I decided not to do that at this time, budget reasons at that time I've started a path down CW and HRD so that's I've been up to, appreciated your message and apricate you checking in - hope you had a nice xmas and new years '73 de KI5JUF keep in touch
With the ft991a you have 2 antenna terminals to protect , you can run a second mfj 1708 to protect the vhf uhf antenna side with a separate recieve antenna connected see video below
I'm watching your videos - I'm still watching some of the videos - thanks again - '73 de KI5JUF
I use this setup all the time with the cable from my FY-991A. I use the waterfall built in to Win4Yuaesu. I had to mod the MFJ device by shorting the Antenna and Transmitter connectors.
Thats what you do on the older version mfj 1708 , it is much better to have the new 4 relay version it protects better an less signal loss
Thanks very much, I really apricate all your help and knowledge, I keep looking into this and '73 de KI5JUF
One other item you should consider is when listening you have two 50 ohm load on the antenna. This makes a voltage divider.
Good evening sir and thanks for the message, I have since realized the impedance mismatch and I never actually did this project, I never liked the idea of having a micro relay on the TX and RX, again thanks for the message I appreciate your feedback good info for all '73 de KI5JUF
@@westtexasvideogateski5juf255 Is this why some people choose to tap into the IF circuit of the 991A to feed the signal to their SDRs? I too am researching these methods to see which way I want to go, so I THINK that the IF tapping method would get rid of the issues of reduced RX signal strengths in both the radio and SDR. But won't the SDR's RX still get overloaded during the radio's transmit? So is the MFJ T/R switch still needed for that??? I'm assuming I'll be using CAT control to keep both VFOs in sync, although I can see some use-cases where I'd want to be monitoring X band while working Y band. Any input would be appreciated!
Omnirig software will let rsp control your transceiver. I’ve been doing the same research, would like to use a small tv to monitor SDR UNO and control my 991A. Thanks for the video ! K5EGD (Haven’t pulled the trigger yet)
Omnirig works great with the sdrplay and rig sinking with it.
One button to sinking or unsink
Also, if you're using the RF Sensing Relay just as an RF Relay (controlled with the 'TX GND' signal), then you don't need the RF Sensing function, so just buy a much cheaper plain and simple RF Relay.
991a rx is better than any cheap sdr with cheap filters.