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Re: TNC Reccomendation




On Nov 12, 2007, at 6:16 PM, John Henderson wrote:

> Great response Nate........I am aware of RigBlaster type  
> applications. I am
> interested in sats like Go-32 and A0-16 for starters. What do they  
> require?


Thanks John, but it really was only the "tip of the iceberg" so to  
speak.  I think you hit "reply" and the reply only came to my personal  
inbox (not to the list) so I'll reply back to both you direct and the  
list both -- I think you'll find that there are a LOT of much more  
experienced and talented folks on the list who can answer specific  
questions about specific birds and types of operation of that bird.

So list folks... John specifically mentioned here in his reply above  
that he'd like to work GO-32 and AO-16 and in another reply I didn't  
copy here he mentions ISS.  You all might comment on his goals and  
options for those birds.

As a start of a reply -- AO-16 has been a bit ill lately.  Search for  
AO-16 on this page <http://www.amsat.org/amsat-new/news/> to see the  
latest.  It has been partially recovered and the command team is  
working on reloading software, so at least for the time being, it's  
probably "out" as an option to start with, but with luck, she'll be  
back.

This page is an excellent resource on the current status of different  
birds, with the caveat that it isn't always updated:
http://www.amsat.org/amsat-new/satellites/status.php

(AO-16 is still showing "green" on that page, so -- you do have to  
take all of this with a bit of a grain of salt.  The best way to stay  
informed that I've seen is to get on the e-mail distribution for the  
AMSAT News Service (ANS) e-mails, which are sent out on a regular  
basis and include the current satellite status information of all  
active birds.  The webpages lag and/or don't always get updates, no  
fault of the volunteers -- they do a great job -- but sometimes it's  
different folks responsible for different things, etc...)

ISS will be your "easiest" choice of the three you've mentioned.  It  
doesn't take much (relatively) to be heard and to hear ISS... you're  
not dealing with ultra-weak signals, and even directional antennas are  
not *always* necessary.   In fact, you can start now, by placing a  
receiver on a good outside antenna on 145.825 and listening when ISS  
is scheduled to be overhead.  If you hear 1200 bps packet bursts, you  
are likely hearing ISS!  (Or a local station attempting to digipeat  
through ISS...)

When it's active (and the Amateur stations on board are turned off for  
Astronaut safety whenever there's an EVA going on), it has a nice  
power budget (!!!) and easily hears stations.  The only "difficulty"  
with ISS is knowing what mode the Amateur station is in.  Various  
volunteers try to keep everyone updated.  Over the years,  there have  
been some challenges when it accidentally gets left (or purposely set)  
in a mode that isn't "useful" to us earth-bound folks.  (Someone might  
pipe up here with the ISS team's website, I forget where that one is.)

Someone on the list commented that *sometimes* a hardware TNC is a  
"plus", especially at the higher speeds.  I will not argue with that  
at all.  Sound card interfaces and software do have limitations  
depending on the quality of the sound card interface, and the way it's  
connected to the rig.  (Of course, the quality of the rig also  
"counts" here.)  I think it's probably "safe" (although someone will  
certainly argue with me... heck, this is the Internet and people will  
argue for any reason!) to say that 1200 bps comms with anything sound  
card based, is "do-able".  At 9600 bps and above, you start to get  
into some more difficult territory, especially at higher frequencies  
(UHF and above) because of Doppler shift as the satellite from your  
ground vantage point seems to be going by at a high rate of speed.   
You can learn a LOT by doing some terrestrial high-speed packet with a  
buddy, or if you're lucky enough to live in an area where there's a  
lot of high-speed packet going on (not as common as it once was),  
there's probably some "Elmers" hiding in that group.

Heck, come to think of it, you're going to want to get even your 1200  
bps packet station up and going "terrestrially" first, too.  Most  
areas have some traffic on 144.39 (APRS Nationwide frequency) and if  
there's active "packeteers" you'll usuall also find some activity on  
145.01 in most metropolitan areas.  (I'm not sure where Cape Carteret,  
NC is in relation to other densely ham-populated areas, so ... again,  
a grain of salt needed here.  You'll find the locals quick enough, if  
they're "out there"!)

Not to send you off away from your digital "dream", since that's your  
goal -- but you should also give AO-51 a try.  The bird is *usually*  
in FM mode, but has the ability to be switched to other experimental  
modes, and Drew KO4MA and the rest of the user-team that work with the  
command team, do a great job of keeping this list updated with the  
current status of the bird.  There have been past opportunities to try  
digital modes through it, and I believe those will happen again.  It  
helps to stay "plugged in" via the mailing lists and ANS.  (They also  
have an excellent website with a schedule posted, when different modes  
are being tried.)  It's a very easy bird to work, and can be done  
(with some practice holding everything, aiming the antenna, changing a  
few memory channels you've pre-programmed for the Doppler shift, etc)  
with a handheld radio and a handheld dual-band yagi, like the Arrow  
antennas, or similar.  It helps to have an Elmer demonstrate this once  
before you try it, but many folks have done it with a little  
encouragement from this list.  It gives you a "feel" for how "fast"  
the birds move across the sky, how long a pass typically is, and let's  
you "shake down" your pass prediction software and other tools a bit  
on something "easy" before adding the computers to the mix.  It's  
worth the effort, and heck,

To be completely honest, my fascination with VHF+ is centered 90%  
around weak-signal terrestrial work, and maybe 10% around satellites.   
I like to listen to the birds more than I ever work them.  But I find  
that satellite folks and terrestrial VHF+ SSB and CW operators  
struggle with very similar technical details... how much loss is this  
feedline?  How do I calculate the Noise Floor of this particular  
receiver and mast-mounted pre-amp setup versus perhaps putting the pre- 
amp down in the shack for convenience?  How much attenuation is in  
this LMR-400 versus running a big honkin' piece of hardline out to the  
antennas?  Etc etc.  You get the idea.

I have a desire to try out some of the new-technology type EME  
contacts and meteor-scatter also, using things like WSJT (and it's  
multiple flavors) which one could argue is a "digital mode" but  
completely designed from the ground up (no pun intended) for use in  
meteor-scatter and weak-signal VHF+ operations.  I have the gear here  
to give it a try, but just haven't gotten any time to do it... (sigh).

So I guess you'd say I'm more of an AMSAT "groupie" than really an  
active satellite operator -- thus, my reluctance to really dive in and  
answer your satellite digital mode questions... there are folks here  
that LOVE that type of operation, and will be more than willing to  
help you out as you get going.

As a final note, there are some excellent references on the AMSAT site  
for new satellite operators.  Some of them are a little bit out-dated  
at this point, and reference birds that aren't with us anymore... but  
the information contained in those documents, combined with a little  
mental cross-referencing to the current list of active birds, is still  
quite valid!

I think this is probably as good a place as any to start looking up  
information:  <http://www.amsat.org/amsat-new/information/faqs/>

Perhaps someday, you can pen an article about your initial learning  
curve, and what you learned as you start operating these birds, and  
help others along.  I'm sure the AMSAT newsletter folks (and website  
folks) would be more than happy to post a slightly more "modern"  
discussion of "How to do it"!

Once you've made a satellite contact, it's addictive -- you'll enjoy  
it!  You can also apply for your "Satellite Communicators Club" award,  
of course!  <http://www.amsat.org/amsat-new/awards/#communicator>

As they say, jump on in, the water's fine!

--
Nate Duehr, WY0X
nate@natetech.com

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