[amsat-bb] Re: ARR Preamp Help

Edward R. Cole kl7uw at acsalaska.net
Sat Aug 6 14:54:17 PDT 2011

Another thing that may have gone is the RF sensing circuit that is 
probably set for 25w max.  RF switched preamps are more susceptible 
to burn-out as they rely on fast switching of the preamp bypass 
circuit.  Even a few milliseconds delay will allow enough RF energy 
to zap the delicate GasFet in the preamp.  This is why we suggest 
using a sequencer to control RF switching before RF is 
generated.  Its not done much by satellite operators but very common 
by mw and eme stations.

Some high-end radios have transmit RF delay settings available in 
their menu.  if you radio has such, add 50-100 ms delay will provide 
much more protection.

You know re-reading your comments I wonder if you transmitted 440-MHz 
thru a 144-MHz preamp?  The RF sense circuit might not detect 440 as 
well as 144 MHz.  That is why radio with separate VHF and UHF 
antennas are preferred.

Best to return to ARR for repair - it is a flat rate.
I have repaired many ARR P144VDG over the years.

73, Ed - KL7UW

At 12:48 PM 8/6/2011, Zachary Beougher wrote:
>Thanks for the responses everyone.  And Dee, no, I am not a handy tech -
>obviously!  I transmitted probably 2-3 times through it using 35w, 1-2
>second each, then it blew.  Like you, Mark, I am a little surprised it blew
>so quickly, but oh well.
>KD8KSN (aka reckless preamp handler) =P
>-----Original Message-----
>From: Dee
>Sent: Saturday, August 06, 2011 3:51 PM
>To: 'Zachary Beougher' ; amsat-bb at amsat.org
>Subject: RE: [amsat-bb] ARR Preamp Help
>You have blown it--If you are not a handy tech.  - Send it back to ARR
>and they have a flat fee for repairs.  Check with them on the
>Dee, NB2F
>-----Original Message-----
>From: amsat-bb-bounces at amsat.org [mailto:amsat-bb-bounces at amsat.org]
>On Behalf Of Zachary Beougher
>Sent: Saturday, August 06, 2011 3:40 PM
>To: amsat-bb at amsat.org
>Subject: [amsat-bb] ARR Preamp Help
>Hi All,
>I was monitoring some passes while mobile today, and amidst all of the
>confusion of messing with coax and frequencies, I accidently
>transmitted on 440, through the preamp, with 35w (the relay is rated
>at 25w).  I thought I had switched the VFO back to 2m, but I guess
>not.  It was only for a split second, but since that every time I turn
>the preamp on it automatically knocks out all received signal.  Does
>anyone have any idea on what I need to do/check to see what I did to
>it?  I have heard of this happening, I just need to know what path to
>take now to get it fixed.
>It is worth mentioning that I can receive fine with the preamp
>in-line, but the minute I throw the power switch it knocks out all
>receive (just static, no received audio).  I have not changed any of
>the connections, so having a coax hooked up backwards is not the
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73, Ed - KL7UW, WD2XSH/45
BP40IQ   500 KHz - 10-GHz   www.kl7uw.com
EME: 50-1.1kw?, 144-1.4kw, 432-100w, 1296-60w, 3400-?
DUBUS Magazine USA Rep dubususa at gmail.com

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