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system comparison



Hi All,
   please turn your PC to Gene's AO40 xls program...

Given
3 foot dish 24db gain (calculated with Gene's other program dish_design xls)
patch feed ( circular, so set program for circular)
dc with a .6 db NF figure and 28 db gain... (this info was pulled off the paperwork sent with the dc)

you will see the blue line well below  xpondr signals, this station hears them all and has some margin

Given
BBQ system... 3x2
BBQ 24db gain  (not likely since were missing some on the sides compared to a round 3 foot dish but ok)
dipole feed  (linear,so program set for linear)
dc with 1.1db NF   37 db gain  ( this info was pulled off one of k5gna ads on ebay, this is for a transystem that has been tweaked
for best performance, he lists the NF at 1.1 to 1.4 with 1.25 typical, I'm assuming  the best...)

you will see the blue line well above the xpondr floor,  this station can not hear the lowest station... it only marginally hears
the next one up... it  requires the other station to be stronger for a qso...

any questions???

Is this setup worthless? NO!       can it not work other stations? NO!      is there a probability that the person is going to need
to run more power and need the other station to run more power up to hear each other? without a doubt...

So dont get mad, its just the way it is... go  buy or build a low NF preamp, get a surplus dish, build a helix feed or a patch  and
use the excellent program Gene wrote to see where is the best place to improve your system....

btw this was all at the programs default setting of 50,000 range and 0 squint , at more range or higher squint  it only gets harder
for both systems, when was the last time you were on at 0 squint?

73's
Kevin
WA6FWF

for more fun change the values  to 7 for squint  and a 59,000 range... and compare each system... you will see why it is nice to
have some margin..


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