[Yaesu] Fw: FT-101zd question

[rb]

The combo that wrote this did a pretty good job!!!  Not bad!!


----- Original Message ----- 
From: "Dr. Gerald N. Johnson" <geraldj at weather.net>
To: <yaesu at mailman.qth.net>
Sent: Saturday, February 04, 2012 12:05 PM
Subject: Re: [Yaesu] FT-101zd question


> That was written in Japanese by a tech writer who didn't understand
> radio transmitter tuning and then transliterated into broken English by
> a technically illiterate translator.
>
> Driving and loading are separate operations. You drive to make power,
> but if you overdrive you splatter. You tune and load to resonate the
> output PI network so it presents a resistive impedance to the PA tubes
> that is the impedance where the PA tubes give the greatest power output
> and are still operating in a linear mode. With only metering for PA
> plate current its conventional to drive for rated plate current, then to
> increase the loading in increments while tuning the tuning for the plate
> current dip. Typically one starts with the loading capacitor at some
> value larger than gives the proper load. This works best for class C
> which is NOT linear. Tuning a linear amplifier, I think, works best with
> a RF power output meter and tuning for maximum output power. The with
> voice adjusting the drive for occasional ALC indication. That presumes
> that the ALC threshold is set to properly prevent driving to clipping in
> the PA and the associated splatter. Otherwise an oscilloscope with
> adequate bandwidth to see the RF envelope is a good tool for setting the
> drive to prevent clipping.
>
> 73, Jerry, K0CQ
>
> On 2/4/2012 8:37 AM, rb wrote:
>> In the FT 101zd manual, page 14, I see this instruction:
>>
>> "Again rotate the LOADING control and PLATE control, each time advancing 
>> the
>> DRIVE control approximately 2 step, until the DRIVE control is fully
>> counterclockwise. The transmitter is now tuned for maximum power output. 
>> Do
>> not exceed the maximum tuning time stipulated previously. Return the VOX 
>> GAIN
>> switch to the VOX position (out of the MOX position, return the METER 
>> switch to
>> IC, and return the DRIVE control to the fully counterclockwise position."
>>
>> This is a different process than I normally go through. What I do is set 
>> DRIVE
>> to 150-175ma, and keep it there. Different things I do cause it to go up 
>> or
>> down slightly. I just re-tweak it to wherever the plate currrent is I 
>> want to
>> be at. I just switch over to USP/LSB from CW tune, leaving it right 
>> there.
>>
>> Going by the above process, it looks like you could easily get 
>> "over-drive"
>> (loaded more than you'd like) by going to full clockwise. Than, going 
>> back to
>> full counterclockwise seems you'd have zero-drive.
>>
>> I'd certainly like to know if this is the correct tuning.
>>
>> What keeps is from going into "over-drive", and what would make it be 
>> zero-drive
>> if at fully counterclockwise position?
>>
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