[CQ-Contest] results auto sw bandpass filters for all bands

Charles Harpole hs0zcw at gmail.com
Sun Jul 26 01:07:04 EDT 2015

My own and perhaps unique solution is to depend on the isolation of the
Radio 1 and Radio 2 and SO2R wiring inside the Expert 2K-FA.   That is the
SO2R RF socket on the amplifier can be either shorted or further isolated
to aid in bandpass interdiction for the "other" radio set on receive during
a high 1.5KW transmission by the "first" radio.

Consult the block diagram at

​to see the chance to get access to the signal chain for more isolation via
the SO2R socket (which I will not otherwise be using).

Factory says about 25db isolation at worse case, without SO2R shorted to
Sounds ok to me if "other" radio is on a different band from "first" radio.
73, Charly​

On Sun, Jul 26, 2015 at 10:49 AM, Mark Ketchell <k5er at arrl.net> wrote:

> Hi Charly,
>      From the two BPFs in my example, you could follow with a simple
> remote A/B switch (Dow-key, etc.). The "A" side from the regular bands is
> normally connected. When a warc band is selected, a diode matrix added
> inside the band decoder could output a  voltage to switch the A/B to the
> "B" side. The common of the A/B goes to one input of your SPE. Duplicate
> for the other radio.
>      Unfortunately, this is now many more pieces than your original
> request for a single box. Before I lead you too far down this path, you may
> want to check out the book, "Managing Interstation Interference" by George,
> W2VJN, available from Inrad(.net). May help you decide what is most logical
> for you. Good luck.
> 73,
> Mark, K5ER
> ------------------------------------------------------
>> Great suggestion Mark.
>> However, where does your RF output from the two filters go?  If directly
>> to
>> antennas and antenna switches, ok, but what if one puts a linear amplifier
>> to follow the BP filters?
>> My SPE amp allows two RF inputs, switchable, so the one input could be
>> regular bands and the other input be for WARC.  That could work great.
>> But, then where is the OTHER transceiver/amp?  No need for the filters if
>> there is no second source of huge levels of RF.  Seems then one would need
>> two SPE amps and a second transceiver??
>> I thank all with suggestions.  73, Charly
> Charly, HS0ZCW

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