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TX Inhibit

[email protected] All Messages By This Member #102675 I want to connect a receive only loop antenna and don't want to risk killing it if the 817 goes into transmit. Is there a way to inhibit the TX output. I could remove the mic so that the PTT is not available but I'd like something a bit more sure than that. Wellbrook loops are very expensive to replace!
Bill Boyer #102676 开云体育 IIRC, there is a tx inhibit on the CAT or audio port on the back.? ?? ? ? ? This message was delivered by flying monkeys! toggle quoted message Show quoted text On Nov 12, 2016, at 10:11, g4edr@... [FT817] <FT817@...> wrote: I want to connect a receive only loop antenna and don't want to risk killing it if the 817 goes into transmit. Is there a way to inhibit the TX output. I could remove the mic so that the PTT is not available but I'd like something a bit more sure than that. Wellbrook loops are very expensive to replace!
Joseph Wonoski All Messages By This Member #102684 开云体育 If the microphone PTT line is a pull down to ground or some such function, you might be able to tie that line high. If there's anything on the rear panel which serves the same function a similar method might be used there as well. Just a thought without a diagram in front of me. ? Sonny N1KHB ? ? ? In a message dated 11/12/2016 1:43:45 P.M. Eastern Standard Time, FT817@... writes: toggle quoted message Show quoted text ? I want to connect a receive only loop antenna and don't want to risk killing it if the 817 goes into transmit. Is there a way to inhibit the TX output. I could remove the mic so that the PTT is not available but I'd like something a bit more sure than that. Wellbrook loops are very expensive to replace!
Bill Boyer #102692 开云体育 I finally got around to looking at the manual, and there is a TX Inhibit pin on the ACC connector on the back of the radio. You'll need to dig through a bunch of sequencer documentation to figure out if you pull the pin high or low to disable transmit.? ?? ? ? ? This message was delivered by flying monkeys! toggle quoted message Show quoted text On Nov 13, 2016, at 10:19, N1KHB@... [FT817] <FT817@...> wrote: If the microphone PTT line is a pull down to ground or some such function, you might be able to tie that line high. If there's anything on the rear panel which serves the same function a similar method might be used there as well. Just a thought without a diagram in front of me. ? Sonny N1KHB ? ? ? In a message dated 11/12/2016 1:43:45 P.M. Eastern Standard Time, FT817@... writes: ? I want to connect a receive only loop antenna and don't want to risk killing it if the 817 goes into transmit. Is there a way to inhibit the TX output. I could remove the mic so that the PTT is not available but I'd like something a bit more sure than that. Wellbrook loops are very expensive to replace!
Chris Cox, N0UK All Messages By This Member #102693 I use this feature as part of my 10GHz transverter sequencing. i am pretty sure, albeit from memory, that a high (+12v) voltage on the TX Inh input will disable any RF out even though teh radio does switch to transmit mode. 73 Chris, N0UK, G4JEC ----- Chris Cox, N0UK chrisc@... toggle quoted message Show quoted text On Mon, 14 Nov 2016, Bill Boyer daweasel@... [FT817] wrote: I finally got around to looking at the manual, and there is a TX Inhibit pin on the ACC connector on the back of the radio. You'll need to dig through a bunch of sequencer documentation to figure out if you pull the pin high or low to disable transmit.
[email protected] All Messages By This Member #102695 Many thanks for all the replies. It looks like if I pull up the TX Inhibit pin to the +V supply rail then?any RF output will be prevented. Regards,?David - G4EDR?
John Green All Messages By This Member #102694 Taking the TX inhibit pin on the ACC connector high inhibits transmission (although the radio still switches to transmit mode). ?I've read some posts in various places which talk about the 817 sensing when a plug is inserted into the ACC socket and causing the line to be pulled high so that you have to actively pull it low in order to be able to transmit. ?I haven't actually verified this (it's certainly not the case on digital modes in my experience) but at least one discussion (on the AMSAT site I think) claims to have verified this by experiment. ?However, I've looked at the schematic and can't see any obvious evidence of this. ?But whether there's a sensor or not, pulling the line high (greater than 5 volts) will inhibit transmission and pulling it low will enable it. ?Hope that helps. 73. De John M0ACN
Andrew G0JCC All Messages By This Member #115645 Hi David.....i'm following up a very old post you made back in 2016.? TX inhibit on an FT817.? Did you get to the bottom of it?? Does it work?? It looks like placing 12v on the TX Inhibit pin on the ACC socket prevents RF being transmitted.? I am working on the sequencing for my 10Ghz system and a TX Inhibit would be very useful! ? Thanks, best wishes ...and Happy New Year ? Andrew G0JCC
davebb123456 All Messages By This Member #115646 Hi Andy? Sorry I honestly can not remember, sorry? Dave toggle quoted message Show quoted text On Sat, 4 Jan 2025, 11:40 Andrew G0JCC via , <andrewmlancaster=[email protected]> wrote: Hi David.....i'm following up a very old post you made back in 2016.? TX inhibit on an FT817.? Did you get to the bottom of it?? Does it work?? It looks like placing 12v on the TX Inhibit pin on the ACC socket prevents RF being transmitted.? I am working on the sequencing for my 10Ghz system and a TX Inhibit would be very useful! ? Thanks, best wishes ...and Happy New Year ? Andrew G0JCC
Nikolai VE3NKL All Messages By This Member #115651 Hi Andrew, ? I may help here... My radio is FT-817ND and the plan is to use it as an IF rig for a 10 GHz station. Of course, I needed a sequencer and decided to design and make it myself. Using the inhibitor was part of this design. It allows to control the TX of the station by the PTT button of the radio mic. You press PTT, the sequencer can sense it, but no RF goes out of the rig until the sequencer makes the necessary switches. After it does and deems it to be safe, it lets the RF go. All this is possible due to controlling the inhibitor line. ? In my case, I use a 47K resistor to pull the Inhibitor line to the 13.8V point (also available on the same connector). This prevents generating any RF by default. When it is time to transmit, the inhibitor pin is connected to the ground.? ? I did testing using a power meter and it appears to be working pretty well. ? 73, Nikolai VE3NKL
Chris Cox, N0UK All Messages By This Member #115652 Definitely does work, Andrew. I do exactly the same on one of my 10GHz rigs. If I remember correctly, I have a ~1k current limiter resistor in series between the +Vcc and the TxInh pin. Chris Cox, N0UK chrisc@... toggle quoted message Show quoted text On Jan 3, 2025, at 06:32, Andrew G0JCC via groups.io <andrewmlancaster@...> wrote: Hi David.....i'm following up a very old post you made back in 2016. TX inhibit on an FT817. Did you get to the bottom of it? Does it work? It looks like placing 12v on the TX Inhibit pin on the ACC socket prevents RF being transmitted. I am working on the sequencing for my 10Ghz system and a TX Inhibit would be very useful! Thanks, best wishes ...and Happy New Year Andrew G0JCC
Chris Cox, N0UK All Messages By This Member #115653 Removal of that +Vcc is the final step the sequencer performs when switching to transmit, and the first signal to be output when switching back to receive. Chris Cox, N0UK chrisc@... toggle quoted message Show quoted text On Jan 6, 2025, at 08:21, Chris Cox, N0UK via groups.io <chrisc@...> wrote: Definitely does work, Andrew. I do exactly the same on one of my 10GHz rigs. If I remember correctly, I have a ~1k current limiter resistor in series between the +Vcc and the TxInh pin. Chris Cox, N0UK chrisc@... On Jan 3, 2025, at 06:32, Andrew G0JCC via groups.io <andrewmlancaster@...> wrote: Hi David.....i'm following up a very old post you made back in 2016. TX inhibit on an FT817. Did you get to the bottom of it? Does it work? It looks like placing 12v on the TX Inhibit pin on the ACC socket prevents RF being transmitted. I am working on the sequencing for my 10Ghz system and a TX Inhibit would be very useful! Thanks, best wishes ...and Happy New Year Andrew G0JCC

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