Re: 12V Power for the Pi (was Re: [RaspberryPi-4-HamRadio] Getting back to the RPi)

Ray Wells

In simple terms 9600 is not audio tones, it's a data switching rate (actually at 4800 and doubled in the process) . For 9600 the frequency response of the signal chain is ideally down to a DC response which of course won't pass through a transformer. One of the "fathers of 9600 packet was James Miller G3RUH who produced various modems. His writings on 9600 are worth a read for some detail about what works and what doesn't. Try this for starters

Ray vk2tv

On 1/1/20 3:02 pm, Daniel Holmes wrote:
It’s always been my understanding it’s not the transformers that are the problem, it’s where the audio is injected—if it’s injected in the mic input then you are limited to 1200 baud, but if you inject elsewhere (the IF? I can’t remember) the you can get 9k6. A lot of modern radios have inputs for data that take 9k6. I think any soundcard can connect to those inputs for higher baud rates via direwolf. The signalink and other specialized cards I think have optical isolators that isolate from the computer. ‘Course it is NYE, and I could be all wrong due to that. 


. Please pardon any mispelings or errors.

On Dec 31, 2019, at 8:48 PM, Michael WA7SKG <wa7skg@...> wrote:

"the Signalink will not work at the higher speed because it has transformers in the audio chain."

Huh?? It is audio. Maybe a greater bandwidth due to the speed, but audio nonetheless. Entertainment system audio often goes over 15 kHz through transformers. I would be interested in understanding why the Signalink cannot do the higher speeds because it has transformers. I always like to learn new things.

Michael WA7SKG

Bill Vodall wrote on 12/31/19 4:13 PM:

The DRAWS board is designed for 9600 baud which most other sound card
interfaces won't handle.  In particular, as handy as it is, the
Signalink will not work at the higher speed because it has
transformers in the audio chain.

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