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Re: Topband: Protecting short receive antennas and Phasers

To: Les Rayburn <les@highnoonfilm.com>, <Topband@contesting.com>
Subject: Re: Topband: Protecting short receive antennas and Phasers
From: Pete Smith <n4zr@contesting.com>
Date: Tue, 14 Dec 2004 07:24:45 -0500
List-post: <mailto:topband@contesting.com>
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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