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Re: Test Tools for determining ao-40 RX performance



A suggestion,,, Instead of 9913 try LMR-600  .505 OD with low loss at that
freq.....that is what I am using...Next best thing to hard-line and costs a lot
less..

Very Interesting email and I totally agree.....

Guy Kd6mtu

"Alan K. Adamson" wrote:

> All,
>
> I've followed the discussion on NF and RX performance for some time.  I've
> also been one of the lucky ones that came up with a pretty good RX setup
> from the start.... I won't say it's on the cheap side, but it works pretty
> well.  I'll explain that setup and some changes I'm going to make in a
> moment, but first I wanted to offer some observations.
>
> When I first started listening to ao-40, I built my system with anticipation
> that we'd get access to the V uplink and so I used 432 as the IF for my
> downconverter.  In retrospect, this had good and bad benefit.  The Good was
> I spent the first month listening to ao-40, capturing telemetry and reading
> all the posts about RX performance and comparing them to mine.  As some of
> you know, I've shared my performance live on the net with both streaming mp3
> audio and live telemetry.  The Bad was, I was unable to use the transponder
> :(.
>
> Well, Saturday I remedied that problem by replacing the 432 IF with a 144
> IF.
>
> What I've noticed in doing a months worth of SWLing on the bird.
>
> - yes, there are people that are running modest setups with medium to high
> noise floors that are making contacts.  But for each of those, I've heard
> time after time, people calling them after a contact that they obviously
> can't hear.  They finish the contact they just made and start calling CQ,
> right on top of people that are trying to work them.
> - yes, there are people who can't hear their downlink and turn up the power
> until they can.  It's pretty amazing to watch the level of ones signal come
> up when this happens.  I'm assuming, that they turn up the power to the
> point where they can hear it and hope that everyone else can and that leila
> doesn't get them :)
> - the most interesting, is the mode where you crank up the power till Leila
> gets you, then you back it down, until just under.  And that is where you
> setup and operate.  What ever happened to the "use the least amount of power
> appropriate to make the contact" rule of amateur radio :).  BTW, this mode
> always produces, "Leila - Gotcha", it gets you right when you are trying to
> exchange that grid square.
>
> Now let me offer some more tidbits of information towards system setup.
>
> - Not only is it RX performance, but it's also TX performance to some
> extent.  You have to think about this, not in the context of turning up the
> power, but more in the context of system performance to get an adequate
> EIRPC for the bird to hear you.  For example, here is what I'm stuck with.
> I have a system where I have about 185' of 9913 between my station and my
> antennas.  (It has to do with trees, towers, etc.)  Saturday, while I had
> everything apart working on the DC exchange, I decided to check the power to
> the antennas.  For 50W of output on the TS2000 to the 435 Antenna, I had a
> whopping 10W.  For 100W of output on 144, I had 37W of output to the
> antennas.  See where this is going.... Improve both your setups and that
> doesn't mean adding more "amp" unless that is the only way.
>
> - On RX performance....I continue to read people saying "I make contacts, so
> I think my setup is good enough".  Well, it might be for you, but understand
> what you present for others with better system as I discussed above.  I'm
> not advocating that everyone go out and buy top of the link equipment, I'm
> just providing some insight.  If you can't hear the transponder noise floor
> at apogee, you are missing *lots* of signals.  I'll offer a case in point.
>
> I was all excited to get my system on the air on Saturday night after the DC
> change.  Pieter - N4IP lives pretty close to me and he runs a 4.5' dish on
> the downlink.  The "unqualified" difference between his system and mine is
> usually 2 Sunits.  If I'm hearing S3 - he usually hears S5.  Our performance
> is "pretty close"... But I'll tell you, I can't hear the Transponder NF.
> The sat was at apogee Saturday night when the transponder came on over the
> Eastern US.  We first established that I could get into the sat and hear
> myself... All whopping 10W of power to the antennas and all.  We were
> coordinating on IRC (btw, for those that want to check out your system, I
> would encourage you to get on there, you'll get a real feel for what others
> are hearing vs. your setup).  We next started looking around the band.
> There were some DL's, and some other Europeans on.  I made a couple of
> contacts and then Mark Hammond came up on the IRC an wanted to test his 1.2
> and 435 uplink/downlink setup.  So we worked to figure out everyone DC
> offsets and found common ground (always an interesting challenge with
> doppler, differing DC offsets, etc).  I was hearing Pieter as one of the
> loud ones.  I could hear a very faint carrier occasionally and through IRC
> determined that it was Mark.  All of a sudden Pieter started to have a
> conversation with him.  I couldn't hear squat!  I tried every combination of
> filter I could think of on the 2000, but nada!  Bummer, my setup wasn't as
> good as I thought.  But I do know how to fix it and I'll explain that later.
>
> I just read an email from Hasan that I hope everyone takes to heart.  Just
> remember one thing.... Just because you can hear yourself, doesn't mean you
> can hear what's on the bird!  That's really the bottom line.  Get on the IRC
> channel and work with some of us to test your system and make some
> comparisons.  We are all experimenting and trying things, some us are
> throwing $$$ after it and others aren't.  We'll all have to accept
> compromise, but we should all work to as optimum of a system as we are able.
>
> I've found some tools that might help in making test.  There is a pretty
> good tool from the guys in DE, that can be used with a sound card to measure
> all kinds of things with radios... SNR is the most useful, but there are
> others as well.  It's called Analyzer 2000.
>
> Between this software and a calibrated Smeter and the "spreadsheet", you
> should be able to measure a "relative" system performance.  I've included
> the link below.  Just as a note, it is shareware.
>
> http://www.brownbear.de/
>
> Ok, back to some changes that I'm going to make to try to improve my RX on
> 2.4.  I can't run a dish at the top of an 80' free standing crank up tower,
> so I'll have to make some long term compromises.
>
> My current setup
> 1 - DirectiveSystems.com 1252 - 52 element loop yagi on an 8' boom, 21dbi
> (linear - horizontal)
>
> 10' of 9913 to the downconverter, this is scary, because 9913 at 2.4 has
> almost 7db/100' loss.  So a 10' section is almost 1 db taken directly away
> from the DC's input :(
>
> SSB UEK3000SAT Downconverter - .7db noise (this isn't a 2000, it's a 3000
> and they spec it at .7 instead of .8 on the 2000) with 30db of gain
>
> 180' of 9913 to get back to the shack... Again a compromise, but this
> doesn't show as bad on the RX side of the DC...
>
> Kenwood 2000 with an evaluated NF of 5 @ 2100hz bandwidth
>
> Spreadsheet number on the above. 63000km, 15 degrees of squint
> system NF = 1.4
> MDS = -144.9
> Beacon S/N = 17.4
>
> My new setup will be
> 2 - DirectiveSystems.com 1252 - 52 element loop yagis, stacked vertically
> with a Directive systems power divider - cross your fingers, 24dbi (still
> linear horizontal).  this is *way* less wind loading than a dish, and what
> I'm going to run for now.
>
> 1 - DEM 2.4G preamp attached right at the antenna (should remove that .7db
> of loss from the 10' of 9913)
>
> 10' of 9913 between the DEM and the UEK.  I'm hopeful that the 17db of gain
> in the DEM will make up for the .7db of loss at 2.4 with the 9913
>
> Rest of system unchanged.
>
> Spreadsheet number on the above. 63000km, 15 degrees of squint
> system NF = .6 (-.8)
> MDS = -148.8 (-3.9)
> Beacon S/N = 22.8 (+5.4)
>
> For me, this will be about as good at it gets....Course, I could always
> think about stacking 2 more 2.4's for an additional 2.5-3db :)..... Nah!!
> Maybe, I'll figure out a way to create a phasing array for circular
> polarization of this combination.... that would be work 3 more db... In
> theory.
>
> My .05 for what it's worth!
> Alan
>
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