[Boatanchors] How to Protect from Nearby Transmitter?

[Rodger Singley]

The preamp will still get killed when powered up or not unless you include a relay to short the input when the preamp is powered off and this would be the most robust solution.  Regular diodes may not react fast enough to provide the protection needed and fast Schottky types will likely work better however depending upon the device the protective diode may need a series resistance to protect against excessive current through the diode during your transmit period.



Rodger WQ9E



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________________________________
From: boatanchors-bounces at mailman.qth.net <boatanchors-bounces at mailman.qth.net> on behalf of Rob Atkinson <ranchorobbo at gmail.com>
Sent: Monday, December 4, 2017 8:47:45 AM
To: David Stinson
Cc: Boat Anchors List
Subject: Re: [Boatanchors] How to Protect from Nearby Transmitter?

kill the dc to the preamp on transmit.

rob
k5uj

On Mon, Dec 4, 2017 at 5:37 AM, David Stinson <arc5 at ix.netcom.com> wrote:
> This is a Palomar LP-1 loop amplifier.  It works
> well listening to Longwave.  The last time I
> transmitted near it (75 mtrs), it blew the FETs.
> The diodes didn't do the job.  How can I protect
> the amplifier from a nearby 472 KC transmitter?
> Use a fast MOSFET to short the loop on transmit?
>
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