[1000mp] Mark V Field Power Output Mod

[Mike Schatzberg]

Hello All:

This question seems to come up regularly, here and on other Yaesu forums as
well.  I repeat here an earlier posting on this subject.

73,

Mike
WB2AJI

> Hello Yaesu Fans:
>
> Other than the fact that the higher power levels most likely are not
> properly  supported by the power supply or final transistor cooling
> capability, an operator should take a look at the IMD numbers for the
final
> transistors, and the curves which represent signal purity at various power
> level values.
>
> Although I have never checked the finals in the Field, if you look at the
> curves for the Motorola finals in the Mark V, you will see a very
> significant difference in output quality at 100 watts per transistor,
versus
> 200 watts.  The same reduction in quality is also found if they are run
too
> low in output as well.
>
> The final biasing will also be incorrect if the output is changed, and
will
> need modification also, if a clean high quality signal is desired.
Neither
> of the Mark V's  make changing the bias easy with a front panel
adjustment.
> Very low output levels are probably better run in Class A, rather than in
> AB2 for this reason.
>
> Considering the change from 100 to 150 watts output is less than even 2 db
> gain, this increase is really not significant unless the power is needed
to
> drive an amplifier, which I doubt is the case.
>
> Before I would change the output upward, I would see what the signal
quality
> will look like by checking those IMD curves.  No doubt neighbors will
> appreciate the time spent in considering the potential interference
issues.
>
> Regards and happy DXing,
>
> Mike Schatzberg
> WB2AJI

----- Original Message ----- 
From: "Mike MacDonald" <mikemacd at erols.com>
To: "All about Yaesu 1000mp" <1000mp at mailman.qth.net>
Sent: Tuesday, August 03, 2004 8:34 AM
Subject: RE: [1000mp] Mark V Field Power Output Mod


> Exactly. My question was kind of devil's advocate to get a
> discussion started. I've always been an advocate of letting
> equipment loaf instead of pushing the envelope. Even if the
> Field will put out 200W is the stress on the rig and possible
> dirty signal worth the lousy 3db? If the consensus is that more
> than 25W AM is not a good idea with the Field then 200W SSB
> isn't either. Leave some headroom.
>
> Mike
> WA2E
>
> -----Original Message-----
> From: 1000mp-bounces at mailman.qth.net
> [mailto:1000mp-bounces at mailman.qth.net]On Behalf Of Adam Farson
> Sent: Monday, August 02, 2004 8:44 PM
> To: 'All about Yaesu 1000mp'
> Subject: RE: [1000mp] Mark V Field Power Output Mod
>
>
> Hi Mike,
>
> Safety is not the issue with AM operation; the PEP of an AM signal at 100%
> modulation is four times the resting carrier power.
>
> Cheers for now, 73,
> Adam VA7OJ/AB4OJ
>
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