[Space] more APRS info

nils at shkoo.com nils at shkoo.com
Thu Feb 11 01:01:14 UTC 2010

This is probably something I should've cc'd the list on instead of just 
sending to Mikolaj. :)


---------- Forwarded message ----------
Date: Mon, 1 Feb 2010 01:13:03 -0700 (MST)
From: nils at vicious.com
To: Mikolaj Habryn <dichro at rcpt.to>
Subject: Re: Fwd: argent order

That looks good to me, assuming the kenwood mic cable does indeed work with it 
as advertised.

You probably want to at least use an external antenna to receive the APRS 
beacons, even if you don't use one for transmitting.  I have a magnetic car 
mount 2m/70cm dual band antenna which should do great for receiving APRS at 
144.390 Mhz.  It has a SMA connector, which looks like it's the same one that 
the PX777 takes.  If you want to borrow it for next weekend, coordinate with 
Erin (eri.comparri at gmail.com) since I'll be out of town. Christie might also 
have an external antenna.

For positioning the antenna in the payload, I bet you'll want to make sure it's 
vertical.  You'll have trouble getting packets through if the orientation of 
the antenna changes in the middle of the packet leading to different ground 
stations being able to get good reception, as might happen with turbulence or 
if the payload spins or whatever. Unfortunately this means that you'll have a 
tough time receiving becaons directly when you're close to directly underneath 
the baloon.  This is complicated to mitigate and probably a regular vertical 
antenna is best for this launch.

For APRS, there are lots of digipeaters about, and any digipeater that hears 
the becaons will generally retransmit it.  I think you want to use the 
"WIDE1-1,WIDE2-2" path when transmitting APRS (see 
http://info.aprs.net/index.php?title=Paths); this will give you the best chance 
of the beacons making it both to the internet (http://aprs.fi/ is the best 
interface I've seen) and to your receiver via RF.

You can see what the raw APRS packets look like here if you're interested: 

Xastir with soundmodem under Linux sounds like a good way to get the APRS 
packets onto your computer.  I only have OSX right now so it's tough for 
me to test that part. :(


On Sun, 31 Jan 2010, Mikolaj Habryn wrote:

> ---------- Forwarded message ----------
> From: Mikolaj Habryn <dichro at rcpt.to>
> Date: Sun, Jan 31, 2010 at 3:30 PM
> Subject: Re: argent order
> To: "Michael C. Toren" <mct at toren.net>
> PX-777:
> https://www.argentdata.com/catalog/product_info.php?cPath=25&products_id=74
> We'll want two of these, I think - not sure about power for it on the
> balloon - maybe a large battery, but then maybe a charger and lots of
> dry cells instead. TBD, but probably won't worry about it for this
> order. Shall we get a single programming cable to share, or is it
> better to have multiples of these?
> OT+ preassembled:
> https://www.argentdata.com/catalog/product_info.php?cPath=22&products_id=72
> OT+ kit:
> https://www.argentdata.com/catalog/product_info.php?cPath=22&products_id=65
> If they have the preassembled & tested OT+ units in stock, then one of
> those and a kit, otherwise two kits.
> 2 Kenwood mic cables:
> https://www.argentdata.com/catalog/product_info.php?cPath=21&products_id=70
> Garmin GPS with connector for OT+:
> https://www.argentdata.com/catalog/product_info.php?products_id=37{4}4
> 2 9-pin male serial cable:
> https://www.argentdata.com/catalog/product_info.php?cPath=21&products_id=117
> ...I think that's it. Right? :)
> m.
> On Wed, Jan 27, 2010 at 11:07 PM, Michael C. Toren <mct at toren.net> wrote:
>> Do you want to grab product_id= numbers for his website, to be sure we
>> get exactly what you want?  I don't know what the appropriate cables are
>> offhand, for example.  (And, in the end, you may need to build it with
>> some of the DB9 parts we have a Noisebridge.)
>> -mct
>> On Wed, Jan 27, 2010 at 10:47:23PM -0800, Mikolaj Habryn wrote:
>>> Two PX-777s, two OT+ kits, two cables to connect them, and a Garmin
>>> GPS with the appropriate connector for the OT+. I think that's about
>>> it for me.
>>> m.
>>> On Wed, Jan 27, 2010 at 9:41 PM, Michael C. Toren <mct at toren.net> wrote:
>>>> No, I haven't yet.
>>>> Hmm, it looks like the OT1+ kit is out of stock, though? ?Hard to tell for
>>>> sure with his shopping cart software vs. the inventory wiki list he links
>>>> to (http://wiki.argentdata.com/index.php/Product_Status). ?I'll have to
>>>> drop Scott a line about it...
>>>> Do you know what you'd like to order? ?It looks like Priority Mail (with
>>>> 2-3 day delivery) is $7.55 for the 2.1lb package my order came out to be,
>>>> so we'd be saving ~$4 by combining orders. ?My shopping card contents:
>>>> (1) Puxing PX-777 PLUS VHF Handheld Radio 
>>>> (https://www.argentdata.com/catalog/product_info.php?products_id=74)
>>>> (1) OpenTracker+ Kit 
>>>> (https://www.argentdata.com/catalog/product_info.php?products_id=65)
>>>> (1) Speaker Mic Cable - Kenwood Type 
>>>> (https://www.argentdata.com/catalog/product_info.php?products_id=70)
>>>> (Note that the speaker/Mic cable is a slightly different one than I
>>>> showed you before -- this one doesn't have the RJ45 connector on the
>>>> other side, but simply pre-stripped and tinned leads. ?But, this cable
>>>> only matters if you're getting the PX-777 handheld.)
>>>> -mct
>>>> On Wed, Jan 27, 2010 at 05:40:06PM -0800, Mikolaj Habryn wrote:
>>>>> Have you already sent your argent order? I'm about ready to give up on
>>>>> getting a consensus opinion from people and make it up as I go :P
>>>>> m.

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