It depends on the location and the wires around. Your power lines might get loaded with RF, and conduct part of the radiated RF back into the shack. A power line filter and a good ground may take care of it. You don't want to fight the RF current, just attenuate it enough, so an L input filter is recommended. I usually include such a filter in all the low voltage power supplies I build.
The interface with two transformers and isolated grounds is a good idea. I built one with scrounged transformers and an optocoupler. It is a good idea not only for avoiding ground loops, but for avoiding thunder induced damage as well, which is pretty common in a tropical place like mine. Once I had to change the cable of an old (still alive) keyboard to use shielded audio cable. A 0.1 uF + 10 uF tantalium capacitor in parallel did the rest of the cleaning in the +5V inside the keyboard. I used a 5 pin audio DIN connector to plug it into the motherboard. I am not advicing you to do anything you are uncomfortable to do, I am only telling what I have done to have up to 400 watts packet on the air. Hope it helps, Jose, CO2JA adrianrav4 wrote: > > Hi All > Having just moved house (& country!), and set up the HF radio gear for > the first time in quite a few years - I'm having a dabble with PSK31. > > I suspect that I'm having problems with poor isolation between the > radio and the PC - at the moment the 'quickly knocked-up' interface is > 'direct' - no opto or transformer isolation. > I can read the PSK31 quite nicely (using DigiPan) - and load up the TX > on low power (10W) - but higher TX power seems to generate odd squeaks > and general instability.... > ...also - I have yet to get a reply from any other station on PSK - > which makes me wonder if my signal's getting distorted past the point > of readability ? > > Does anybody have a source for 1:1 audio isolation transformers ? I > can't seem to find them from the usual suspects (ebay, CPC...?) - > would need to be an organisation that ships to Ireland..... > > Many thanks in advance > Adrian - EI5JV
