[DSP-10] 1296 RSU contest wrapup

[Courtney Duncan]

I made a couple of two meter contacts in the contest in an attempt to  
raise someone with 1296 gear.  The two I worked didn't and the ones I  
heard who did couldn't hear me on 2 meters or didn't hang around long  
enough or were covered by QRM or something.  This made it seemed  
unlikely they were positioned for a tough 1296 attempt.

The last technical problem was to get the 64 MHz to come up and stay  
up reliably.  My diagonal mismounting of the LO board in the box was  
contributing.  A trip to the store for the right mounting hardware and  
this seems to be cleared up.

I have a 2.5K slug for my Bird wattmeter.  Realizing that 20 mW would  
be about 40% of one small division on the meter, I put it in line.   
Sure enough, PTT and forward power moves the meter about .4 division.   
Reflected, nothing.  Good.  But then I noticed that it this defection  
occurs regardless of modulation.  PTT in CW mode and it's .02 Watt  
out, whether the key is down or not.  PTT in SSB and it's .02 watt out  
whether I'm talking or not.  Listening on FM, it does the right  
things.  No signal key up, signal key down...  This was not the  
experience I had with the KA7EXM meter (extrapolated) measurements.   
They showed 10-20 dB difference key down to key up.  Yes, it was 10s  
of dB higher TX than RX too, as most transmitters are, and 10s of dB  
higher RX than disconnected and terminated, as most receivers are.

I don't have anything like this power doesn't change key down to key  
up on the DSP-10 itself.  What is it?  Spurs?

Now I'm continuously monitoring with the DSP-10 spectrum display on a  
very slow scroll, all receiving.  One line every two minutes takes  
10-11 hours to fill up the screen.  I can see from spectral content if  
there has been QSO activity on a channel as transmitters typically cut  
off pretty sharp at 2500 - 3000 Hz audio.  This distinguishes them  
from QRN.  One peak around noon local today could have been a QSO.  I  
was at work.  Monitoring audio now.  I hear something that must be  
radar.  S (dididit) on-off noise repeats three times for a seconds  
then a second off.  This repeats six times followed by a break.  In 2  
WPM CW that's SSSSSS  SSSSSS  ....  Too regular to be oscillations.   
Nothing I turn on or off in the shack effects it.

Listening 1296.329 right now,

http://www.newsvhf.com/beacons2.html lists
1296.329 N6XQ    DM12jr CA San Diego    18W to 4 loopers @ 330 deg.
That would be pointed right at me but 150 miles away.  Still, I have  
heard this beacon on my HT while hiking in the foothills near here, a  
couple thousand feet higher.  The scanner stopped on it!
I'm seeing something on about the right frequency but it doesn't sound  
like CW.  No recognizable code or sound recognizable as code.  Maybe  
just a birdie.  Doing an LTI now to see if I can learn anything else.   
Don't hear the SSSSSS here.

After the contest last night, I put the DSP-10 on FM and went driving  
around the neighborhood to see what range 1296 at 20 mW has from a  
discone to an HT antenna (Diamond SRH-999, four bands, but a  
compromise on all).  The picket fencing was typical for L-band, ten  
(well, nine to be precise) times as bad as two meters.  Full quieting  
stopped at about 100 yards.  Copyable with noise went out to maybe  
300, each measured in three directions.  Stopped altogether when I  
went behind blockage like a hillside.  I had forgotten to instruct the  
base operator (KG6GXW) in DSP-10 squelch operation, but the test was  
good enough.

So, I got to thinking about my L-Band experience from about 1990 and  
this doesn't disagree with it.  Back then I ran 10 watts to a 44  
element loop yagi and --- struggled.  That was 50 dB better.  The  
discone was always quite poor at 1.3 GHz except for the 50 ohm load  
part.  I've tried HT to HT operations with it and not done better than  
this, so that's actually good.

One more test, measure the noise figure with my calibrated Sabin source.

Eventually I'll get lucky and hear something, perhaps.  There's a  
local Friday night net....

Longer term plans:  horn, slippers (1-5 W) preamp, antenna mounting,  
small dish.

but 73 for now,  Courtney, n5bf/6


"It's science. They don't know anything; they just make a lot of  
educated guesses."  -- Viannah Duncan

Courtney Duncan, n5bf/6
cbduncan at earthlink dot net
144.200, 7.040.
n5bf at amsat dot org