[1000mp] Re: Mark V Field Power Output Mod

[D. J.]

  "Sick person" is a little harsh.  I don't think we have crazy people 
here just a little over enthusiastic ham and I can relate to that as 
I've done my share of experimenting too.

Operating the radio beyond it's designed specifications is not  good 
engineering practices and that is how the FCC states it in the rule 
book.   My recommendation is get a MKV for only about $300 bucks more 
you have a 200 watt rig.  Use the field as it was designed.  More power 
is easy with an amplifier, but use it judiciously also.

73
Dale, K9VUJ


On Aug 6, 2004, at 16:55, Joe Subich, K4IK wrote:

>
> Mike,
>
>> I think the Toshiba 2SC2897 IMD Po curve speaks for itself,
>> but a few extra words about it won't hurt.
>>
>> There is a world of difference with IMD numbers ranging from
>> -38db to -24db, the change from 60 watts to 100 watts.  The
>> idle current was set to 100ma, in the test set up.
>>
>> The factory apparently sets the radio at 50 watts output per
>> transistor, or IMD numbers of approximately -35 db.  Therefore
>> operation at 100 watts per transistor, degrades IMD performance,
>> with this circuit configuration, by a factor of approximately
>> 10 times.
>
> The Field is operating very close to the point of minimum IMD.
> If you look at the test circuit, it does not contain much of
> any output filtering - just an impedance matching "L" network.
> Since most practical lowpass filters  will have on the order
> of .6 dB to 1 dB of insertion loss, I'd estimate the push-pull
> pair of transistors in the Field is actually generating about
> 115 watts at the collector to make 100 Watts at the output
> connector.  That would set the IMD at around -36 or -37 dB.
> The output of the radio can't be controlled any more closely
> than that.
>
> I stick by my original comment, anyone who would run a Field
> at 150 or 200 watts is the same kind of immature, sick person
> who would illegally "hotrod" a CB radio.  BTW, Texas Star (one
> of the biggest trash peddlers) uses four 2SC2897s in their 350
> Watt "export" amplifier - need I say more?
>
> 73,
>
>    ... Joe, K4IK
>
>
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