Adjusting the Yaesu FT-1000 MP or most any 100 watt output SSB transceiver for AM transmission. IE. Is your voice lopsided ? Yes it is if you have a larynx
If you had a symmetrical voice, which a female or a very high pitched male have , 100% modulation of a 25 watt carrier would produce 100 watts PEP. Deep sounding males ( thanks to their larynx ) can easily be asymmetrical ( lopsided ) up to 150% which would mean that a 12.5 watt carrier would produce 100 watts PEP. I run a carrier level of 10 to 15 watts on AM for little distortion. I can push it to about 20 watts, but other fussy people notice the distortion. I also have audio phase reversal switches on my microphones. With a Oscilloscope you can quickly get your audio phase properly set for about a negative going 95 % and well over a positive going 100% ( up to 145% ) modulated carrier. Thus your output wave form would be identical to your audio input wave form. The last thing we want to do is over modulate with negative going ( over - 100% ) modulation as substantial adjacent channel noise is produced when the low level mixer is cutoff (carrier cutoff). Therefore with a MP ( 100 PEP) I recommend 15 watts and a Mark 5 ( 200 PEP ) 30 watts with audio phase set for more positive going than negative going modulation. You can feed your mike directly into a scope to check your asymmetry. But put scope on RF for proper phase setting as even some factory mikes are backwards. In SSB there is no need for any phase check.
With no modulation .. RF power
level on front panel fully clockwise. AM position. Set internal carrier level
pot to 15 watts output for a MP... 30 watts for a Mark 5. These are
the maximum carrier amounts for an asymmetrical (male) voice !
The 15 watts applies to any 100 watt PEP output transmitter. Now when you
modulate, crank up the Mike gain watching a watt meter on
Average ( not peak ) Power, until the carrier power only occasionally kicks
downward. This downward kick is your carrier being cutoff, resulting in
distortion. No downward deflection would be distortion free. Without compression
or peak limiting a little downward would be acceptable to keep the average up.
If you monitor yourself with good headphones ( I like Sony CD10's about $20) ,
as you bring up the Mike gain you should hear the distortion as you start to
kick your external average watt meter downward. When set properly with little
average downward, now observe the Internal PO (power out) meter. You should see
your 15 watts of carrier and as you modulate your peaks of 100 watts or slightly
higher should show momentarily. Although your carrier power is only 15 watts
your PEP will be 100 watts or slightly higher. Yaesu properly automatically
disables ALC and Processing in AM. By the manual I set my metering menu hang
time to two seconds (2000 ms) for all functions. For excellent modulation
reports I use a $30 dollar Radio Shack Mike #34069 with a Radio Shack wind sock
plugged into the RCA Phone Patch input on the rear and the FT-1000 MP's internal
TX EQ Menu 4-4 set to #4. And then to roll off some lows on SSB ( as
my voice is too bassy ) : Menu 7-7 SSb-t at 150-3100 or 200-3100 .
Modulating the FT-1000MP Balanced Modulator Directly from your Audio Processor or Audio Equalizer.
A New Inexpensive Studio Condenser Microphone and audio processing; digital Behringer & Marshall
01/16/2004