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Re: 6 Buck S-band Downconverter results and question



Quoting Steve Holly <sgholly@optonline.net>:

> Greetings,
>  
> First the question: Has anyone successfully used their 6 buck
> downconverter with a simple low gain antenna like a patch or corner
> reflector to work AO-51?
>  
> I converted my CalAmp 130215 by changing the crystal and tuning the
> filter using a low level 2.4GHz signal source but so far have only
> achieved marginal results. Using a preamp ahead of the downconverter
> signals are Q5 and I made several contacts. Without the preamp I can
> pick out an occasional word or two out of the noise but QSO's are
> impossible. Comments and/or suggestions welcome.
>  
> 73,
> Steve WI2W
> ----
Steve:

I've had my unit working for a month or so, and worked a couple of people
on AO-51, including a WI2W :-) 

A description of the work in progress is at
http://www.amsat.org/amsat/archive/amsat-bb/200509/msg00861.html
and I produced some notes on my work at:
http://www.amsat.org/amsat/archive/amsat-bb/200509/msg00882.html
In particular, I describe what I found tuning the thing by ear. I'd be
interested in others' experiences. Before P3E goes up, I'd like to send the
unit to someone with proper test gear to tune expertly and compare to
high-grade equipment. A two-figure donation to one of the HEO campaigns
would perhaps make appropriate recompense.

It hasn't been perfect readability, but I think I'm getting better results
than you. With only a few feet of cheap catv cable, I was getting S9+20
full quieting. Now that the unit is in a tupperware container on the
rotating beam and with 50' of equally cheap catv cable, I'm finding the
signals more choppy: sometimes full quieting, sometimes quite difficult to
work out. (I don't *think* this is the fault of cable loss, since I still
have an S1 noise floor.) I recently discovered that my computer was spewing
a few S-units of noise on S-band. The last pass I listened to was better
once I'd turned it off (but that meant tuning by hand.)

A note for full scientific honesty: between my first observations and
latter one I twice transmitted 2m signals of about 4w up to the thing. It
seems that the horrific losses in the catv cable did their stuff for me,
because I can still hear my test signal at about the same level. I assume
that a busted front end would result in a deaf downconverter.

I find there are deep fades, and I look forward to building a RHCP helix
antenna to see if the circular polarization and/or the increased gain will
help. Long-term the goal is something that will work for HEO, so narrowing
my beamwidth will help develop a system with HEO-style accuracy. And if it
can track a LEO, it certainly can track a HEO.

I found a reasonable guide to how well I was improving the system could be
measured with the distance from it that the signal source (ref. above)
could be heard. Tuning increased this remarkably, as did the antenna.

An additional note, which I didn't include in my letter direct to Steve:
the letter above claims that the s-meter on my if rig didn't change in the
presence of the s-band signal unless someone transmitted. I now realize
this is incorrect: even though the static sounds the same, one's s-meter
will indicate the signal. Why doesn't the s-band transmitter on AO-51
produce a silent FM signal as does the one in mode V/U?


73, Bruce
VE9QRP
----
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