[Amps] Titan 425 Reflected Power

[Will Matney]

Jim,

It sounds to me like you have a meter in the amp that is reading off, if several other meters have shown a different swr after the amp, and all but the amps meter have agreed. Most all meter circuits are the same, whether using a strip line or a transformer. Two things that could be wrong is the circuit not be balanced out (nulled) with if it has balancing caps. Another thing could be a resistor that has lost its tolerance. Both circuits merely rectify the RF, filter it, run it through a resistive divider circuit, and feed that to the meter. The balancing caps are generally piston trimmers used to null out the meter. They will be right where the RF is picked up at, whether it be a strip line or a small toroidal transformer that the RF output line will go through. The input tuning, nor the antenna relay wouldn't have anything to do with it as generally the wattmeter/swr circuit is between the relay and the RF out jack. That is in a lot of amps, if the relay was after the meter, then a relay contact could cause a false reading if it were dirty and messing with the impedance. I'd about be the meter is out of adjustment somehow though.

Best,

Will	

*********** REPLY SEPARATOR  ***********

On 9/24/06 at 11:53 PM Michael Tope wrote:

>----- Original Message ----- 
>From: "Michael Tope" <W4EF at dellroy.com>
>> From: "Jim Brown" <jim at audiosystemsgroup.com>
>
>>> I'm encountering a strange problem with my Titan. If I follow 
>>> standard practice and achieve a 1:1 match with the exciter, then 
>>> take the amp out of standby, the amp typically shows mismatch on 
>>> the order of 1.5 or 2:1. 
>>> 
>>> If I then re-tune the antenna for minimum reflected power on the 
>>> Titan, the VSWR at the tuner, and also at a Bird inserted right 
>>> after the Titan, shows a mismatch of 1.5 - 2:1. The mismatch seems 
>>> to be greater at higher frequencies. 
> 
>> Jim, 
>> 
>> Sounds like you may have a load impedance that varies with 
>> applied power. Try the following experiment - put the the Titan 
>> in operate mode at full power, make the adjustment with the 
>> external tuner for minimum VSWR (as you describe above) and 
>> then slowly start backing off the exciter drive to see if the VSWR 
>> changes slowly or abruptly as the output power of the Titan is 
>> lowered. IOW, right now you have two data points - exciter 
>> only and amplifier at full power. Try plotting the points in 
>> between. 
>> 
>> 73, Mike W4EF.............
>> 
>
>Nevermind my previous suggestion, Jim. It doesn't apply here. 
>I misread your original post and was somehow thinking that the 
>Titan meter matched the reading on the Bird and the antenna 
>tuner bridges and that the readings just differed between high
>and low power. You clearly state that the Titan meter does 
>not agree with the Bird and the tuner bridges. Sorry for the 
>mixup. I'll try to read more carefully next time. 
>
>BTW, have you tried driving a 50 ohm dummy load with the 
>amplifier. It would be interesting to see if you could get a 
>good tuning solution (high output power, low grid I) using
>a 50 ohm dummy load connected through a short piece of
>50 ohm cable to the amplifier output. 
>
>73, Mike W4EF.................................
>
>
>
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