Re: Guy Atkin's Independent Testing of PL-380 7.5" Loopstick

jim_kr1s <jkearman@...>

--- In ultralightdx@..., "Pollock,Raphael E" wrote:
> Hi Jim!
> Do you know of any plans for the regen pre-amps that you mention in text below? It would have to be an improvement over my old BAX-1, a one transistor kit from the mid 1980s that is a broad band preamplifier...

Is that BAX-1 the old International Crystal amplifier? Meant to ask. A regen preamp might be an improvement, but it may not be necessary. I don't know of any published circuits, would like to get a look inside the commercial one.

In a tuned circuit where the inductance is fixed, the reactances increase as you go higher in frequency. A regen made with, say, a 240-uH coil and a 365-pF cap, can be hard to manage at the high end of the band, but very mellow at the low end. That's why I split the band on my receiver. I wondered how they managed that on the commercial antenna-preamp. Assuming you don't need extremely high selectivity (the antenna probably doesn't have to provide anywhere near the selectivity you can get with a regenerative circuit), you could swamp the tuned circuit with resistance and still get lots of gain, and reasonable selectivity.

I should look into this a little more. When I was cogitating on it, I was thinking of something that could be remotely located and tuned. You'd definitely want to use it with a ferrite-rod antenna to reduce hand effects. But an experimental version tuned with an air variable wouldn't be hard to whip up. I do think it would be more useful with older receivers, than with the latest high-gain ULRs and standard portables, which already have lots of front-end gain.


Jim, KR1S 

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