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[TenTec] Using Manual Ant Tuner With Pegasus

To: <tentec@contesting.com>
Subject: [TenTec] Using Manual Ant Tuner With Pegasus
From: wa3fiy@radioadv.com (WA3FIY)
Date: Tue, 5 Feb 2002 10:39:35 -0500
On 5 Feb 2002, at 7:36, n4lq@iglou.com wrote:

> There isn't any "safe way". Some ways are less dangerous than others.
> Use something else to tune the antenna then change over to the
> Pegasus. Palomar had a switchable noise bridge for this purpose.
I must respectfully disagree that it is dangerous to tune-up a Pegasus 
or any other popular 100 watt transceiver.  All major manufactures 
provide warranties on their radios and they would have to have rocks 
in their heads to produce a unit so frail that it would not withstand 
the wide range of abuse the ham radio community will dream up to 
see just how good their engineering departments really are!     :-)

Seriously, it is not uncommon to find intermittent open or shorted 
connections in our feedlines or to inadvertently transmit into the 
wrong antenna and so on.   These conditions hardly ever cause 
failure of the PA.  

The PA stage in the Pegasus is robust and well protected against 
catastrophic failure modes, so don't worry about doing damage to 
the finals.  Someone in an earlier post said that the only protection 
on a Pegasus is the fuse.  Not so!  Beginning with the Paragon I 
believe, all TT 100 watt radios have included a current limit sensor 
to fold back drive when the PA current reaches design max levels.   
In my opinion this is a much better design than SWR fold-back 
because it is current, not SWR that damages transistors.  As I recall, 
the Motorola MRF 45X series transistors were able to operate into 
infinite SWR.  All transistors have finite voltage and current limits 
however.  I know TT is now using a different transistor part number 
in the PA and I don't know it's SWR rating but I'll bet it is about the 
same as the Motorolas.

That said, I'm not suggesting we deliberately abuse our radios and I 
agree that it is good practice to reduce power during tune, not so 
much to protect the radio as to comply with FCC rule 97.313(a) and to 
be considerate of others using the band.

Just follow the instructions for your tuner, use minimum power 
needed and fear not!    Your Pegasus will live a long and healthy life 
and your stress level will be much lower.  Hey..........this ham radio 
stuff is supposed to be fun!!!!            :-)



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