Tom,
One interesting thing to try would be to put a shorting plug on the
Centurion relay control input so that the T/R relay stays closed all
the time and then check to see if any arcing occurs on leading
characters from the exciter. That experiment would control for
hot switching of the T/R relay. For convenience, you could use a
footswitch on the amp control line and close it before you start
sending.
73 de Mike, W4EF..........................
----- Original Message -----
From: "Georgens, Tom" <tom.georgens@engenio.com>
To: <amps@contesting.com>
Sent: Wednesday, November 10, 2004 9:08 PM
Subject: RE: [Amps] Ten-Tec Centurion
> 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@contesting.com [mailto:amps-bounces@contesting.com]On
> Behalf Of Georgens, Tom
> Sent: Wednesday, November 10, 2004 3:16 PM
> To: 'amps@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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