[600MRG] [rsgb_lf_group] Receiver protection

[Bart Lee]

A a couple of big knife switches, one of which shorts the antenna(s) to
ground work for lightning protection, as well as transmit / receive.  As a
historian I like the resonance (pun intended) with the old wireless days:
throw one switch when you want to transmit and throw it back when you want
to receive.  Of course I also use front end protection on the main SDR
receiver (DXE) and that instant saturation works remarkable well.  73 de
Bart, K6VK ##
-- --
Bart Lee

Texts only to: 415 902 7168

www.bartlee.com

{Bart(dot)Lee(dot)K6VK(at)gmail(dot)com}
<http://www.lawforhams.com/>



On Tue, Jul 10, 2018 at 11:59 AM Bill Cromwell <wrcromwell at gmail.com> wrote:

> Hi David,
>
> I wondered if somebody was going to mention shorting the RX input to
> ground. I supposed that was too simple and old-fashioned for today's
> hams so I sat on it. That's what I do and always did. I have the grey
> beard to prove it :) Just because it's old school doesn't mean it won't
> work any more.
>
> 73,
>
> Bill  KU8H
>
> On 07/10/2018 12:13 PM, David G0MRF via 600MRG wrote:
> > Hi Paul
> >
> > I'm sure you will get many good ideas from the group.
> > I took the view that my preamp protected the receiver....and the preamp
> > was expendable. - Also the max output from the preamp was not sufficient
> > to damage the receiver.
> >
> > Even so....After using it for a while, I decided that a little more
> > protection was called for, so I placed a small relay (about 1/2 inch
> > square) to short the input to the preamp to ground when the system was
> > in 'transmit'
> >
> >
> > 73
> >
> > David
> >
> >
> > -----Original Message-----
> > From: N1BUG paul at n1bug.com [rsgb_lf_group] <
> rsgb_lf_group at yahoogroups.co.uk>
> > To: rsgb_lf_group <rsgb_lf_group at blacksheep.org>; rsgb_lf_group
> > <rsgb_lf_group at yahoogroups.co.uk>; Discussion of the Lowfer (US,
> > European, & UK) and MedFer bands <lowfer at mailman.qth.net>; 600MRG
> > <600MRG at mailman.qth.net>
> > Sent: Tue, 10 Jul 2018 12:05
> > Subject: [rsgb_lf_group] Receiver protection
> >
> >
> > Does anyone have ideas for receiver front end protection at LF and
> > MF? I am worried about my TX signal damaging receivers.
> >
> > Of course the best idea is to disconnect the RX antenna from the
> > receiver while transmitting. Any good solution while leaving it
> > connected?
> >
> > Now I have a pair of back to back 1N4148 diodes across the receiver
> > front end but I don't think this offers real protection because they
> > allow too high voltage before conducting. Also there is a preamp
> > after the didoes which can bring the RF to dangerous levels!
> > (Somehow nothing was damaged during last winter operating this way... :)
> >
> > 73,
> > Paul N1BUG
> >
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