Back in the days of steam radio, didn't we use TR switching using bottles? I
seem to remember an 807 used as a switch, but the memory dims and I'm not next
to my library to look it up. Do we *have* to detach the PA on receive?
Perhaps there's a way without resorting to PIN diodes, but then, someone would
have thought of it already.
David
G3UNA
> >
> Hi guys:
> It so happens that during the last 2 years or so I worked on high power
> amplifiers in the kilowatt range .
> PIN diodes are made by very few manufacturers, coming and going all the
> time. They can run In the 300$ dollars range, are susceptible to burn out at
> mediocre SWR,s and require back bias voltage approximately 3 times the PTP
> RF voltage involved. They also require a forward current of a few hundreds
> of mA to conduct well when open. This adds directly to the input noise
> because they operate as a noise diode would.
> In short, if you don't need fast switching speeds, don't mess with them.
> They also have only a poor isolation of around 30 dB. In QRO use the
> leftover power at the receiver port is still to much so that you need some
> additional switching after the main diode with associated driving circuits.
> In short, drop it!!!
> 73 and all the best:
> Alex 4Z5KS
>
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