[Amps] CW and High Voltage

[Iezzi Family]

I also have a TL-922.  When I first got the Kenwood, I always adjusted for 
peak power but received reports of poor audio quality.  With the help of 
some pricey lab equipment that I have access to at work, we came up with a 
good tune up procedure that yielded much better performance.

My new tune up procedure is as follows:

Adjust the transceiver for about half power out.
Dip the plate capacitor.
Adjust the Load capacitor such that the grid current is one quarter of the 
plate current.

The Load capacitor usually ends up between 4 and 6.

Although this adjustment is not the peak power output for this power input, 
the measured distortion was substantially lower at this point than at the 
peak power adjustment.  The plate to grid ratio holds true as I increase the 
power of the transceiver up to the max where the plate is at 800 mA and the 
grid is at 200 mA.

 The procedure in the Kenwood manual will yield a similar setting although 
they just tell you to turn the Load cap slightly clockwise for better 
performance.

Measurements at the lower voltage settings yielded slightly higher harmonic 
products (still within spec) but the amplifier was easier to tune.

Steve
KT4FY

----- Original Message ----- 
From: "Steven Cook" <sccook1 at cox.net>
To: "Phil Clements" <philc at texascellnet.com>; <Amps at contesting.com>
Sent: Saturday, September 03, 2005 9:31 PM
Subject: Re: [Amps] CW and High Voltage


> Thanks to all for your collective wisdom.
>
> I assume manufacturers added the CW position on older amps to meet FCC
> limits on input power for that mode.
>
> Did this serve to maintain circuit Q, or were there other considerations;
> e.g., power supply limitation, et al.
>
> Just seems weird to operate an output stage that is not fully "dipped and
> peaked."  Old habits are hard to break!
>
> When I tune up my Kenwood TL-922 in the CW mode, and then decrease my
> exciter output to around 50W, I notice a "HUGE" residual "dip and peak"
> remaining in C1 and C2 respectively and a 200+ watt increase in output
> power.  What's up with that???
>
> I guess I'll just have to get over the urge to "fine tune" things.
>
> Grrrrrrrr <smile>
>
> -Steve (WG7K)
>
>
>
> ----- Original Message ----- 
> From: "Phil Clements" <philc at texascellnet.com>
> To: "'Steven Cook'" <sccook1 at cox.net>; <Amps at contesting.com>
> Sent: Saturday, September 03, 2005 12:01 PM
> Subject: RE: [Amps] CW and High Voltage
>
>
>>
>>> Team,
>>>
>>> I've acquired an older Henry 2K-4, which only has one High Voltage
>>> setting
>>> ~ 3500V no load.
>>>
>>> It runs a pair of 3-500z triodes and will be driven with ~100W
>>>
>>> My question concerns running the amp at reduced output on CW and if it 
>>> is
>>> better to:
>>>
>>> 1.  Apply full drive, and adjust C1 and C2 until the desired level of
>>> output is achieved...
>>
>> This is never done under any circumstances on any mode!
>>
>>
>>> 2.  Apply full drive, adjust C1 and C2 until maximum power is achieved,
>>> then reduce the exciter drive without readjusting C1 or C2.
>>
>> This is correct for all modes.
>>>
>>> What is the ramification of starting out with reduced drive, (like 25 or
>>> 50 Watts) and adjusting C1 and C2 until maximum output is achieved?
>>
>> Because the tank circuit is designed to operate at only one impedance
>> transformation and Q, and it is usually designed at the maximum key-down
>> anode voltage available and maximum rated anode current for the tube(s).
>>
>> For best harmonic attenuation, cleanliness, and efficiency, always use
>> method 2 above.
>>
>>
>> (((73)))
>> Phil, K5PC
>>
>>
>>
>
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