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Re: [Yaesu] V Field Mod For Power Level

To: "Thomas Giella KN4LF" <kn4lf@tampabay.rr.com>,"a Yaesu E-Group" <yaesu@contesting.com>
Subject: Re: [Yaesu] V Field Mod For Power Level
From: "Mike Schatzberg" <cherokeehillfarm@earthlink.net>
Date: Sun, 27 Jun 2004 21:14:16 -0400
List-post: <mailto:yaesu@contesting.com>
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
----- Original Message ----- 
From: "Thomas Giella KN4LF" <kn4lf@tampabay.rr.com>
To: "a Yaesu E-Group" <yaesu@contesting.com>
Sent: Sunday, June 27, 2004 7:48 PM
Subject: [Yaesu] V Field Mod For Power Level

You go to VR3003 on the IF board. My V Field only put out 90 watts on 160
meters from the factory.  The rig will put out up to 200 watts on CW but I
set it to 150 watts max. I run allot of MFSK16 and RTTY at 150 watts with no
power supply or finals problems. The power increase mod no no is just
another ham radio urban legend. I've also run my FT-990 and FT-840 at 150
watts for years with no problems. There are some appliance operators that
can screw anything up so the rig manufacturers write the manuals for the
lowest common denominator.

Thomas F. Giella, KN4LF
Plant City, FL, USA
Grid Square EL87WX
Lat & Long 27 58 31 44N 82 09 51 98W

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