In a message dated 17-Sep-99 09:04:23 Central Daylight Time, n4lq@iglou.com
writes:
> Note: I said MOST. Omni A through D used the reed relay. All Paragons,
> Omni 5's etc also used it. I'm not sure about the Corsair using diode
> switching at the antenna. Are you sure? Someone with a Corsair needs to
> put their ear on the cabinet and listen. Century 21 and 22 used diodes.
> I'll have to check the Argosy I have.
Yepper. There is a relay in the Corsairs for switching an amp [which can
only be defeated by electrical or mechanical means mentioned earlier in this
thread], but the T/R switching is done between two diodes. The circuit
rectifies RF from the transmit line [with 1N914's], develops a negative
voltage and applies this to the Anode-to-Anode junction of the T/R diodes to
reverse bias them, essentially 'shutting off' [actually, more like placing a
huge attenuator in there really fast] the circuit between the aerial and the
receiver. While the Corsair circuit uses 1N4007 as the 'PIN' diodes [IIRC],
the circuit in the '509 [which is significantly different and quite elegant]
uses a true PIN diode.
If you put your ear to the cabinet of a Corsair, you'll hear a relay, but
that is only for external amplifier switching.
73, Jim
NØOCT
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