Years ago we made a bias supply for a condenser mic. from a simple 2 gate astable circuit, followed by a voltage multiplier, made from a bunch of diodes and capacitors. I would question whether it's worth the trouble though.

K9KJM,

That looks like an interesting article, but that website is really horrible. Is the documant available anywhere else?

Good advise has been given. I would just add that I would always do a visible inpsection before I apply power for the first time. I would also check power supplies and regulators before checking functionality.

The one I'll never forget, from a contest long ago, was "xylophone enema two queen queen".

In the past I bought several off-brand counters and was never satisfied with them. I ended up getting a used HP 5383A about 15 years ago. It's a basic 500 MHz counter and works well for my needs. The IC's are mostly generic types. The only repair I've had to do was to replace a seven segment LED that had a bad segment. It happened to be the same part my company had used on an old instrument, so we had a stock of them. I often see these counters at hamfests for reasonable prices.

I'm not sure exactly when Beckett got the call. W9OE is not listed in the 1977 callbook but is in the 1980 book. There was a period in the '70s when 1X2s were made available to Extras. I think '77 was towards the end of that. So I would assume he received the call closer to '77 than to '80.

I looked through my collection of callbooks and as far as I can tell, W9OE was vacant from the time 9OE dropped out until Raymond Beckett had the call in the late '70s.

There are many directional hearing aids, if that would help.

If they are current production or recently discontinued parts, I think the best place to get data sheets is directly from the manufacturer's website.

I'll admit that it bothers me when people use then instead of than or quite instead of quiet.

I have owned three portable generators. The first was a Coleman. It was very noisy and produced a horribly distorted waveform but was cheap and reliable. The second was a Kipor. It was quiet and produced a nice sine wave, but would not run for more than a couple hours without fouling the plug. The third is a Yamaha 2400 watt. It's very quiet, always starts in one or two pulls, has a nice sine wave output and runs like a champ.

Another advantage of some inverter generators is, they can be paralleled with a like unit for more power if needed.

Hard to say what they mean by "EMI/EMC knowledge". I would assume you would need to understand basic principals of emissions and immunity and be able to apply that knowledge. So your design stands a good chance of passing the required tests or you can fix it if it doesn't.  They might want you to know something about EMC standards and whats involved in the testing.

My point is that even if you pick a cap that is small enough to not be a loading problem, it can cause the amplifier to oscillate. Possibly at several MHz and rail to rail.

It's not a good idea to put capacitors across the output of solid state audio amps. Capacitive loads can cause stability problems. Aside from that it probably wouldn't solve your problem anyway.

There are a lot more 10m chambers around these days, since they have been proven to give results as good as an OATS. We use one at a test lab here. The chamber's elimination of ambients along with improved test software has vastly reduced testing time. Emissions tests that used to take a full day or more, if everything went smoothly, have been cut down to a couple of hours.