Topband: Protecting short receive antennas and Phasers

[Pete Smith]

Seems to me you need to sense the PTT state of the radio versus the state 
of the Phaser's switch, and only allow the PTT to actuate if the switch is 
set to the transmit antenna.  This could be done with relays or with a 
simple gate.  You might take a look at the circuitry of TopTen's DX Doubler 
SO2R box to get some ideas on how they do things like this.

73, Pete N4ZR

At 06:36 PM 12/13/2004, Les Rayburn wrote:


>For the second time in as many years, I fried my Quantum Phaser (I use
>this to phase a beverage on the ground and an EWE against each other)
>by "tuning up" into the receive antenna input on my MFJ-933.
>The auto-tuner has an A-B switch to select either the transmit
>antenna or the output of the phaser (receive antenna). I had
>been listening to some DX, then switched frequencies. I hit
>the "tune" button on the rig and watched in amazement as
>it struggled to match the antenna.
>Seconds passed, and I was wondering why the tuner couldn't find a match.
>Then I started screaming! As feared, it had blown a bi-polar transistor
>inside the unit. So I was without the phaser for the duration of
>the contest.
>Can someone recommend a way of protecting the receive antennas,
>phasers, and transformers from accidental transmissions.
>73,
>
>Les Rayburn, N1LF
>
>
>Les Rayburn, director
>High Noon Film
>100 Centerview Drive Suite 111
>Birmingham, AL 35216-3748
>205.824.8930
>205.824.8960 FAX
>205.253.4867 CELL
>http://www.highnoonfilm.com
>205.253.4867
>
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