[Drake] TR7 PA problem: part 3

[ik2bcp - Guido Tedeschi]

Sorry for the delay, my ADSL was down yesterday evening...

Hi Larry,
    thanks for the explanation.
If you will try to make some measurements, I will check if my PA is fine and
go further.
Ciao, 73 and thanks
Guido, ik2bcp


----- Original Message ----- 
From: <ltaft at charter.net>
To: <drake at mailman.qth.net>
Cc: <ltaft at 2fords.net>
Sent: Sunday, February 06, 2005 3:12 AM
Subject: Re: Re: [Drake] TR7 PA problem: part 3


> Guido,
>
> I think the predriver board has a increasing gain with frequency response.
> Also the 15 and 10 meter bands switch in gain increase networks in the
> feedback ALC loop.  This means that Drake designed in compensation for the
> amp decreaseing gain versus frequency.
>
> Your statement that drive input level signals are constant over the bands
> means something is wrong in the early part of the xmtr.
>
> I will try to make some measurements to confirm.
>
> 73, Larry  K2LT
> drakerepair.com
>>
>> From: "ik2bcp - Guido Tedeschi" <guido.ted at tin.it>
>> Date: 2005/02/05 Sat PM 10:54:26 GMT
>> To: <drake at mailman.qth.net>
>> CC: ltaft at charter.net,  ltaft at 2fords.net
>> Subject: Re: [Drake] TR7 PA problem: part 3
>>
>> Hello Larry,
>>     many thanks for the answer.
>> Do you say that about 12dB of gain difference between 1.8 and 18MHz is
>> normal?
>> If my PA is fine, what do you think about my problem?
>> Please, look at my previous two message on the list ("TR7 PA problem" and
>> "News about TR7 PA problem")
>> 73 and thanks
>> Ciao
>> Guido, ik2bcp
>>
>>
>> ----- Original Message ----- 
>> From: <ltaft at charter.net>
>> To: <drake at mailman.qth.net>
>> Cc: <ltaft at 2fords.net>
>> Sent: Saturday, February 05, 2005 5:29 PM
>> Subject: Re: [Drake] TR7 PA problem: part 3
>>
>>
>> > You should have an increase in drive signal as the frequency increases.
>> > The gain of the amp decreases with increasing frequency.
>> >
>> > Using an oscilloscope on the input to the amp board I measured the
>> > following:
>> >
>> > At 3.5 MHz
>> > Input to amp board 1.6 volt peak to peak.
>> > Output 120 watt output.
>> >
>> > At 28 MHz
>> > Input to amp board 6.2 volt peak to peak.
>> > Output 85 watt output.
>> >
>> > 73, Larry  K2LT
>> > drakerepair.com
>> > 800-687-9161
>>
>>
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>
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