[Amps] Ten-Tec Centurion

[Georgens, Tom]

Thanks to all respondents for the thoughts.

A few comments.

1.  The fact that it does not happen with the other amps does work against
my theory.  I should note that the other amps are not the same (AL1200,
TL922, AL80A).  That said, I don't think it disqualifies the theory.  The
AL1200 can probably absorb the spike.  The TL922A relay is so slow, the
spike may pass before the relay closes.  No guess on the AL80A.

2.  The RFsense in the Centurion is in support of QSK.  It is not intended
to work the way I inadvertently used it.  It is true that it necessitates
hot switching of the relay.  I do believe that it supports the theory of an
overshoot transient.  Oddly, the despite the hot switching, the transceiver
does not fold back.  Conversely, the TL922 is so slow that it does cause
foldback.  Even if the RFsense makes the problem go away, this is not how I
wish to operate the amp.  I still would want to understand root cause.

3.  The padder cap transient response suggestion is a good one.  However,
when not arcing, the amp works exactly as expected with the settings where
the manual suggests they should be. The padder caps are also both used on 80
as well.

4.  I do not think the antenna is much of a factor.  It is a halfwave
inverted V at 90 feet.  Admittedly, it is not a pure resistive 50 ohms at
all frequencies but it should be well within the tuning range of the amp.  I
mention it just so that you all know it is nothing exotic or dramatically
shortened.  I believe it to be free of intermittent connections.

5.  K2VCO's suggestion on the carrier level is something I will try.  I may
be causing this myself.

6.  Could advancing the load control slightly help out?

7.  I was also going to try and see if the problem still happened with the
radio autotuner on in case it impacted any potential spike.

8.  Ten Tec suggested that the variable cap is probably pitted, causing the
arc.  I do not think this is the problem as the arc is not always in the
same place.

73, Tom

-----Original Message-----
From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com]On
Behalf Of Georgens, Tom
Sent: Wednesday, November 10, 2004 3:16 PM
To: 'amps at contesting.com'
Subject: [Amps] Ten-Tec Centurion



I have a Centurion at my contest station in Barbados that works flawlessly
on 10-80 but will arc on 160.  It is tuned into a resonant antenna with a
reasonable SWR.

On 160, the amp will occasionally arc immediately on key down.  If it does
not arc immediately, it will not arc if the key is held down.  Also, when it
does not arc, it tunes smoothly and at the predicted settings.  All of the
arcing is in the Tune cap and is not always in the same place.

My theory is that there may be power overshoot from the TS850 on the leading
edge of the carrier that is causing the arcing.  It is hard to see this on
the wattmeter and my 3 other amps all work fine.  Does this seem like a
reasonable theory and is there any way to compensate for this?

On my most recent trip, I performed a flawed experiment.  For convenience, I
used a different TS850 to drive the amp and the problem occurred only once
out of dozens of tries.  I then moved it to the TS850 where I had previously
noted the problem.  In this case, I was never able to reproduce the problem.
I tried mistuning to some degree but no hint of the problem.  However, when
taking the whole thing apart, I noticed that I had never connected the amp
relay cable.  The amp was using RF sensing to key the relay.

As I said my experiment was flawed but I would like to understand what is
really happening.

Any suggestions would be greatly appreciated.

73, Tom W2SC 8P1A

Tom
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