[amsat-bb] New and improved Echo receiving

["Edward R. Cole" <al7eb@xxxxxxxxxxxxx>]

After transmitting into my 432 preamp this Sunday, I made some improvements.

I decided to assemble the 432 portion of my Arrow and mount in on the B5400
az-el system that has the AO-40 dish.  Then I repaired the N9MKC preamp by
installing a mgf-1402 GasFet (didn't know what the orignal device was).
That increased the preamp gain from 20 to 25-dB.  

Tonight I observed the 0550-0605 utc pass (orbit# 95 per NOVA) which had a
max elevation of 34-deg at range of 1312-km.  It rose right on schedule
peaking at 435.160 MHz with a signal of s-7 to s-9 (noise floor is s-5).
At closest range the freq was 435.153 and at set it was 435.142 MHz.  At
times the s-meter was maxed at s-9+60.  This with the FT-847 internal
preamp turned on.  Turning the pre-amp off the signal was still s-9+10 to
+20 dB!  Interesting experience manually tracking with the B5400 and hand
tuning the radio.  It required adjustments about every 30-seconds.  I am
using the keps with epoch time = 4183.1227440900.  AOS and LOS were within
30-seconds of NOVA predicted.

Now to fiddle with Echo-tlm and MixW now that I have the patch cable wired
correctly (first time I wired into pin-3, the PTT line, with obvious
results...argh!).

My original observations using a 3/4 WL ground-plane worked but I agree
having some excess gain probably is an advantage for capturing good tlm.
For FM-voice the ground-plane may be adequate.  A 432 preamp is a necessity
unless using high-gain antennas and low-loss feedline.

73's, Ed - AL7EB
BP40iq


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