[TenTec] re: pegasus internal tuner

[George, W5YR]

I am not a Pegasus owner, so my horse is not in this race, but from what I
have read on the reflector, TT has a history of designing amp stages that
*must* be loaded rather correctly or they draw too much current and
self-destruct. Hence the high-speed circuit breaker used in TT power
supplies and required for non-TT supplies. Perhaps those days at TT have
passed and they no longer design amps with such tender devices and lack of
protection built-in protection.

With that a background, I would have to temper my usual position that any
SWR under 2:1 is "good enough" and say that if the Pegasus finals are that
tender, then perhaps there is some risk, however slight, that the amplifier
devices might be subject to damage under the conditions described.

I think that Carl is probably correct and that it is a non-problem for most
users, based upon the number of good working radios out there with the
built-in tuner. And, as I have posted before, one cannot expect two SWR
bridges in cascade to give the same result since the one nearest the load
will always introduce circuit effects that will alter the reading of the
one nearest the source. But, it the one nearest the source that is coming
closest to telling the truth about the loading situation for the finals.

In my station, I always tune my external manual tuner for 1:1 SWR
indication on the internal bridge and meter in the radio. That is the meter
and the location that is showing more accurately than any others how close
the load seen at that point comes to being the required 50-ohm resistive
load for the final amp. 

Usually, the external SWR bridge is either spot on or very close to showing
zero reflected power under these conditions, but on some bands and
antennas, it may show 1.3:1 or so when the transmitter meter shows 1:1.
But, that is the one I believe and tune for, not the one in the external
tuner.

If the Pegasus internal tuner is automatic and cannot be "touched up"
manually after it does its thing, then I would have to agree that the
finals are probably not seeing exactly the design load. BUT, how much the
difference and how much the effect, I have no idea.

Pragmatically, per Carl, the problem is minor at best.

72/73, George W5YR - the Yellow Rose of Texas         
Fairview, TX 30 mi NE of Dallas in Collin county EM13qe   
Amateur Radio W5YR, in the 56th year and it just keeps getting better!
QRP-L 1373 NETXQRP 6 SOC 262 COG 8 FPQRP 404
Icom IC-756PRO #02121  Kachina #91900556  IC-765 #02437

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Carl Moreschi wrote:
> 
> I think this thread has developed down a bad stream.  First of all, there
> are
> a lot of pegasus internal tuners out there and most are doing very well.
> Second,
> it is normal for two different SWR meters to give results that do not
> exactly
> agree.  Third, any SWR less than 2 to 1 is normally fine, and even 3 to 1
> really
> isn't so bad under most circumstances.  What I was trying to say in earlier
> posts
> is that we really never know what are true SWR is anyway, only an
> approximation
> to at best a half an SWR point.