-----Original Message-----
From: Tom Rauch <w8ji@contesting.com>
To: amps <amps@contesting.com>; Steve Thompson <rfamps@ic24.net>
To: <amps@contesting.com>
Date: 08 September 2000 05:38
Subject: Re: [AMPS] Blown TL922A... What to do?
>
>> Has anyone been able to measure the frequency of oscillation in, for
>> example, TL922? What dip frequencies are found with a GDO in a 922? In
>> other amps?
>
>
>I'm missing something in the above Steve.
>
>Tell me how a GDO can be used to measure the mode of
>resonance? How do you know the impedance is high, instead of
>low? How do you know what you are measuring in a complex
>system, since it has no directional ports?
In order - it can't, you don't, you don't. On the other hand, sometimes when
I look at a cap which could do service as a tune C, I see more than one
resonance. If the tune C in a particular amp has similar characteristics
then dip frequencies from a GDO can be a piece of a jigsaw puzzle if it's
not possible to do proper measurements.
>
>I can dip my amplifier tank on 1.8 MHz. Does that mean it
>oscillates there also?
>
>These are serious questions, don't take them as flip remarks. I'd
>like to know those answers.
I've tried to make the replies concise.
>
>> >Of course you nee a real amp to measure. What amplifier do you
>> >have available? If you have one that I have, we can go through the
>> >measurements and compare results on here.
>>
>>
>> I don't. I've never mastered a straight key, so I've not been able to
pass
>> the code tests to get on hf over here. A degree and 25 years designing rf
>> for a living doesn't count. I'm hoping to sidestep the system by taking
>> Extra class exams next month.
>
>OK, so you can't measure a PA...and haven't measured one.
>Without doing that, on a device that measures impedance of
>coupling between ports, how do you know all this stability
>handwaving is true?
I don't - I'm just gathering data that might help me understand things in my
own way a little better. Sometimes along the way, the questions might help
someone else do the same, in the way that you and others here have done for
me.
Steve
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