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Call Sign : 108-CT-226 / MM0IMC Posts : 107 Times Thanked : 3 Join date : 2023-03-10 QTH or Location : Ayrshire Equipment Used : Amstrad 901 Sidebander
Subject: SSTV Interface... Wed Jun 07, 2023 1:11 pm
In the past, I've built a DIY PSK31 interface for HF. It worked very well and used an optoisolator for keying the radio, plus audio transformers to keep any ground loops isolated.
I've got the parts to make a similar project, but for 11m SSTV. The problem is that I want to use a CRT 6900v7 as the radio and I'm not sure if the optoisolator will be able to key the radio or if the pinouts on the mic socket are even compatible, due to the voltage present of the pins.
Any ideas?
Victor likes this post
Victor CT Directors
Call Sign : 26-CT-3228 / M7VIC Posts : 6513 Times Thanked : 397 Join date : 2019-11-10 QTH or Location : Bedford Equipment Used : Various
Subject: Re: SSTV Interface... Wed Jun 07, 2023 4:50 pm
Hi Ian,
The TX pin on the CRT is active low and tied high within the processor so your opto-coupler idea should work OK.
The only pin to avoid is the 5 volt pin which is used with resistors to enable channel up/down functions and fair warning is given not to short this out to ground! (Pinouts available on various sites and I believe also in the manual.)
Have fun with it.
All the best, Victor
MM0IMC likes this post
MM0IMC Senior contributor
Call Sign : 108-CT-226 / MM0IMC Posts : 107 Times Thanked : 3 Join date : 2023-03-10 QTH or Location : Ayrshire Equipment Used : Amstrad 901 Sidebander
Here's the interface I built. It's oversized and over-engineered, but works well. I just need some skip now...
Last edited by MM0IMC on Sun Jul 23, 2023 8:31 am; edited 1 time in total
GaryWilson, Victor and SangueG like this post
Victor CT Directors
Call Sign : 26-CT-3228 / M7VIC Posts : 6513 Times Thanked : 397 Join date : 2019-11-10 QTH or Location : Bedford Equipment Used : Various
Subject: Re: SSTV Interface... Sun Jul 23, 2023 5:52 am
Hi Ian,
"Oversized and over-engineered" can often be the order of the day and so long as it all works who's to say anything indifferent.
(My first FT8 radio interface on my old FT757 was built in a similar vein. )
Should be up to the job of any data mode transmission you're likely to encounter so well done with your build.
All the best, Victor
GaryWilson and MM0IMC like this post
MM0IMC Senior contributor
Call Sign : 108-CT-226 / MM0IMC Posts : 107 Times Thanked : 3 Join date : 2023-03-10 QTH or Location : Ayrshire Equipment Used : Amstrad 901 Sidebander
Subject: Re: SSTV Interface... Sun Jul 23, 2023 8:30 am
Victor wrote:
Hi Ian,
"Oversized and over-engineered" can often be the order of the day and so long as it all works who's to say anything indifferent.
(My first FT8 radio interface on my old FT757 was built in a similar vein. )
Should be up to the job of any data mode transmission you're likely to encounter so well done with your build.
All the best, Victor
I've built an interface previously, but gave it away to someone else whom wanted to do PSK31 on an Icom 706.
It's a standard design using an opto-isolator, two audio transformers and a 100:1 voltage divider to reduce the audio level from the external speaker socket on the back of the radio, down to what the laptop soundcard can handle.
Today at 3:42 pm by 
Subject: SSTV Interface... 
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