[Amps] TT Centuruion oscillation

[m.ford]

----- Original Message ----- 
From: "Mike Schatzberg" <cherokeehillfarm at earthlink.net>
To: "Henry Pfizenmayer" <pfizenmayer at worldnet.att.net>
Cc: <amps at contesting.com>
Sent: Saturday, October 08, 2005 6:03 PM
Subject: Re: [Amps] TT Centuruion oscillation


> Hello Henry:
> 
> If you remove the coax from the Orion, while it is oscillating, does the
> oscillation stop?
> 
> Are you using the tuner, if yours is so equipped, in the Orion when the unit
> oscillates?
> 
> If you are using the tuner, try turning the tuner off.  If you have no
> tuner, you might try inserting one between the Orion and the Amp.
> 
> You may have a ground loop on 40 that might be causing some issues.  You
> might try a longer length of coax between the Orion and the Amp, say about
> 20 feet of RG 8 type.
> 
> Also, it is worth trying a line isolator to help with the ground loop if one
> is present.  I have an extra one if you want to try and see if it will help.
> They are not very expensive in any event.  Place the line isolator between
> the Orion and the Amp.
> 
> When you add the longer coax, see if the input SWR does not indeed improve
> from the 1.4:1 which you have now.

When you add longer coax you increase the return loss thus improving the SWR.
If you add enough coax you can drive the return loss so high that you appear to
have a nearly perfect match no matter what is connected to the other end.

Of course you wouldn't hear anything either.

Mike k1ern

> 
> 73 and Happy Dxing,
> 
> Mike Schatzberg
> WB2AJI
> ----- Original Message ----- 
> From: "Henry Pfizenmayer" <pfizenmayer at worldnet.att.net>
> To: <amps at contesting.com>
> Sent: Saturday, October 08, 2005 10:58 AM
> Subject: Re: [Amps] TT Centuruion oscillation
> 
> 
>> By any chance has anyone experienced self oscillation with a Centurion
> key
>> up after application and removal of drive ? Mine has decided to do this on
>> 40 meters only (into a good 50 ohm dummy load). It is fine on all other
>> bands. On 40 it appears to tune normally and have normal power out but key
>> up it continues to put out about 250 watts PF and PR on the internal meter
>> (nothing is coming out of the amp because the TR  relay  is in  receive.)
>> Have not determined the freq of oscillation as of right now. Input SWR
> seems
>> about normal 1.4 worst case on 40 .
>>
>>  Once its oscillating - makes no difference if its in operate or standby .
>> You can kill it by pulling the key lines - or by turning the Orion off.
> (no-
>> the Orion is not putting out power key up - and have tried changing the
> qsk
>> delays)
>>
>>  Using Orion driver - have tried changing to ant 2 and keying loop 2 - no
>> difference. Orion seems perfectly normal in all respects. (output power
> does
>> not hang on any band )
>>
>> Have checked the Centurion input filter band switching voltage to the lpf
>> board and it is switching ok.  Have the  lpf board out , all solder
>> connections look fine , 40 meter filter has continuity  - will check the
>> relay tomorrow .
>>
>>  Just wonder if anyone has seen this . TT has not seen this and I have
> tried
>> several things they suggested on a couple different calls.
>>
>> Rgds-- Hank K7HP