Paul Beringer wrote:
> I recently built a hard line coax loop for RX and am pretty happy with
> it.However, my Pro3's RX antenna jack doesn't seem to have the feature to
> disable RX during TX. So what's happening on the coax loop is that it's
> getting RF back into the radio and causing the radio to disable power out.
>
Yes Paul your PRO-3 radio protection features is being trigger by
excessive RF on the RX antenna. Sometimes a series low voltage light
bulb will help but a better solution is a positively driven relay on
TX....not by RF but DC derived from the TX.
With my PRO-3 I simply put a relay in a metal box with BNC connectors.
The relay is 12 volts DC but the trigger for it on TX is drawn from the
plus 8 volts which occurs on TX. The box also has a toggle switch to
allow me to transfer the relay from external RX antenna to the straight
through functionality. I have tried to use the MFJ noise canceling box
backwards as a mean to provide a second RX port...and also other and
other RF actuated devices but after to many complaints of chopped
leading edge characters I stopped that.
On ACC-2 (If I recall) there is a plus 8 volts on TX which will
drive...as in my case the Darlington pair of 2N2222 or equal...without a
worry about the current demand of the relay. You can get 12 volts from
the same socket but it is not switched on TX and the current is only
about 200 ma but enough for a small TX/RX relay which when configured
will give you a RX separate port for the PRO-3.
Ever since Earl Cunningham, K6SE did a critical review on the Icom Pro-3
I was sold on the fact that there is *not* a better low band radio the
market today that, with the rebates and free supply, can get anywhere
near the weak signal performance. It has clean CW, so many so many
firmware driven feastures, along with super DSP and just over $1200 even
today with a switching power supply. Only I just don't know why ICOM
never felt it required to have a external antenna for RX......they do
have other switchable antenna ANT 2 AND VHF with PL-258. but for TB they
have never offered a mod....perhaps to protect the front end from
RF...but a small pc relay circuit on their MB would have solved all that.
73,
Herb Schoenbohm, KV4FZ
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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