drive levels, isolation and clicks
- I just bought a new rig (FT-847) and connected it (from the HF DATA in/out
socket) to the sound card. I find that receive audio levels are fine
and I can afford to use quite a bit of input gain. Transmit audio
levels are a bit low though; maximum power out through this interface
is about 50W, although I can do 100W on CW key down.
I put 1:1 isolation transformers in the transmit and receive audio
paths. Audio out of the sound card on the MT63 terminal's tune 1 signal,
or the Feld Hell tuning signal, is about 200mVp-p, which should be
plenty. On the other side of the transmit transformer, I only get
40mVp-p (which looks very noisy on the scope, too).
The unofficial FT-847 FAQ has an interface circuit which suggests
a 1k:8 ohm audio transformer in the transmit line and no transformer
in the receive audio. Is that a better choice of transformer?
I thought 1:1 would have been ideal. (Of course, with the quality
control at the electronics store, they could be some other ratio
too for all I know).
Another problem -- I seem to get clicks in the transmited audio,
even just listening on the PC speakers. Presumably they've always
been there. Anyone know why that might be and how I can fix it?
They seem to occur at all sorts of volume levels. I also changed
the PC type settings (486/P100/P200+) in the Hell terminal to see
if that changed the sampling rate and fixed the problem, but there
was no difference.
Hamish Moffatt VK3SB <hamish@...> <hamish@...>