Sorry but I dont agree with this. It´s a shame people increase
the transmitter power above factory specs.
It will defenitly make IMD performance much much worse.
Even at the factory specs 100W the 1000MP Field has very poor
IMD performance, increasing power to 175W will defenitly
make something poor even worse.
Measurements has shown that at 100W splatter products 5 kHz
on each side are only down 35 dB on one side and 40 dB on
the other (not symetrical).
When power was decreased to 50W it got about 20 dB better,
i e splatter was down 50 dB 5 kHz away on also symetrical,
at 50W the TX is actually pritty good.
This is not measured with 2-tone test but with voice modulation,
i e like reel life conditions.
This was measured on a HP analyser and also done in a RF test lab
by someone that knows what he was doing.
As we can notice daily there are more and more wide signals on
the bands and it do have an explanation.
My recomendation would be to run a 1000MP Field only at 50W but
ofcourse nobody would do that sadly enough.
73 Jim SM2EKM
--------------------------------------------------------------------
Thomas Giella KN4LF wrote:
My original post below has stimulated allot of controversy and posts. I stand by what I already said:
.....I've tested the rig extensively at 175 watts on CW and RTTY and have suffered no component failures, overheating, etc. and no transmit spectral degradation. Of course like all mods. make it at your own risk.....
I look at it this way. In the original spirit of ham radio I'm not afraid to open up my modern expensive rice box, to experiment and modify. In my original post I never mentioned operating my V Field at 200 watts but it did hold up very well with no overheating etc. at 175 watts on CW and RTTY, as an experiment. Why did it hold up so well? It's because the rig is better engineered and has better specs. then advertised and a certain amount of "appliance operator" headroom is built in.
Am I stressing the rig? Maybe so but if it blows up I'll fix it and/or buy another one. One ham posted in response to my original post, to paraphrase, "Real Ham's understand how electronics work and don't turn up the power on their rig". I say "Real Ham's" are not afraid to experiment.
In any event, in my day to day operations I never run my V Field above 125 watts. I originally tweaked up the power output because from the factory my V Field only put out 90 watts on 160 meters and I needed 125 watts to drive my old linear to 800 watts.
73,
Thomas F. Giella, KN4LF
Plant City, FL, USA
Grid Square EL87WX
Lat & Long 27 58 31 44N 82 09 51 98W
PODXS 070 PSK31 Club Member #349
KN4LF Solar Space Weather & Geomagnetic Data Archive: http://www.kn4lf.com/kn4lf5.htm
----- Original Message -----
From: Thomas Giella KN4LF
To: a Yaesu E-Group ; a 1000MP QTH e-List ; FT-1000MP@yahoogroups.com
Sent: Monday, August 02, 2004 6:28 PM
Subject: Mark V Field Power Output Mod
Justin et all,
The Mark V Field power modification is simple but it will attract naysayers that will warn of power supply damage/failure, finals failure, degraded transmitted spectral purity, etc.
Pop the top and bottom covers. Gently turn the rig upside down on a hard surface with the front of the rig facing you. There are three boards visible. One is the "Control" board on the left side, the "AF" board on the back right side and the "IF/Filter" board on the front right side. Go to VR3003 on the AF board and turn it clockwise. It's marked "RF Power" (I think it was). Fully clockwise gives you 190 watts in the CW mode on 14200 kc, 200 watts on 1845 kc and 180 watts on 28400 kc. Of course connect an antenna with low VSWR or a good dummy load.
I've tested the rig extensively at 175 watts on CW and RTTY and have suffered no component failures, overheating, etc. and no transmit spectral degradation. Of course like all mods. make it at your own risk.
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