[TowerTalk] External Receive Antenna Switch

[Roger (K8RI)]

On 10/20/2010 8:55 PM, Richard Solomon wrote:
> I would like to add an external Receive Antenna to an older radio that does
> not have a separate Receive Antenna input.
> The crude way would be another T/R relay but that has inherent problems.
An external "T/R switch" such as a Dow Key with the auxiliary contacts 
should do just about every thing you need with few negatives. You might 
need to run semi-break-in instead of full QSK but that is sufficient for 
most.
Actually you could just use the amp keying line to also key a small 
relay to disconnect the receive antenna and ground out the receiver 
terminals. If need be you could use a surplus vacuum relay or a pair of 
them for the receiver. Set the key and unkey time constants so on key up 
the receiver disconnects and shorts out first and when unkeying the 
receiver is connected *after* the output drops.

It really works pretty much the same whether you use the same antenna 
for transmit and receive, or separate antennas. The requirements are the 
same as far as timing.

73

Roger (K8RI)
> Anyone know if something more exotic exists ?
>
> Thanks, Dick, W1KSZ
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