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10 db signal improvement on ao40 - free



I've been thinking about posting this and was reminded to do so on
Tuesday's pass when Leila welcomed me for the first time.  What intrigues
me is the huge difference between the readability of my downlink signal on
cw vs. ssb.

I run 30w. ssb/40w. cw watts up 45 feet of 9913 to my old KLM 44 el. crossed
yagi.  Down link is a bbq dish, UEK3000 converter and another 45 feet of
9913 (typical and not exciting).  AO40 was WSW of me and moving slowly west
and up.

The cw signal with my 500 hz narrow filter was s8 with transmit power turned
down to the minimum of nominally 6 watts.  I worked W0SAT and W0TUP at this
level.  There were a few ssb signals on, just above or below my noise level.

My signal was decreasing as the bird moved away.  I then tried to compare my
signal on ssb with cw.  Although difficult to quantify with my equipment the
signal seemed to be about 1.5 s units better on ssb as measured through the
2.4khz if filter.  This tells me that there has to be a db gain for a cw
signal on
transmit as well as on receive.

As far as I know after discussions with VP2VI and KP2A over the years the
transmit gain advantage has never been formally quantified.  It seems to
make sense in that all the rf power is concentraged at one frequency on cw
while it is spread over the voice spectrum on ssb.  The two cw gurus agreed
this gaini must be at least equal to the cw receive gain.  Therefore, if I
double my ICOM's hypothetical receive gain of about 5db (due to the narrow
filter) one would
arrive at 10db or about what I have been experiencing.

If anyone knows of any formal study of transmit gain in relation to
bandwidth of signal I would be interested.  If not it might be a worthwhile
endeavor for someone to do one.

In any it event, it looks like by using cw you can get about a 10 db signal
improvement at no cost.

Mal, NP2L


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