Where to buy a Radiometrix HX1 / something better for APRS HAB transmission?

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Patrick van Staveren

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May 8, 2024, 5:06:55 PMMay 8
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Hi there,

I'm looking to run my first HAB flight since moving back to the US and since I doubt I'll get many listeners in my area, I'd like to fly an APRS transmitter.  It seems like the old standby is still the Radiometrix HX1 - but I can't seem to find one for sale anywhere (except a distributor in Australia).

Does anyone have a recommendation of a similar sort of module?  I have a perfectly acceptable Raspberry Pi tracker which just needs an APRS transmitter and a bit of testing - but I'm not even sure what to use.

Thanks!
Patrick


Patrick "Trick" van Staveren
https://trick.vanstaveren.us/

Antal Vincz

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May 9, 2024, 12:44:27 AMMay 9
to uk...@googlegroups.com, Patrick van Staveren

Mark Jessop

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May 9, 2024, 3:43:08 AMMay 9
to uk...@googlegroups.com, Patrick van Staveren
None of those links are particularly useful for high-altitude ballooning. 
Hooking up a handheld to a raspberry pi might be fine on the ground, but the weight penalty is considerable on a HAB launch. Then again with the large mass of many US launches maybe it's the norm...

While you might be tempted to fly APRS, remember that APRS network coverage isn't going to extend to the ground, and you're still going to need to run your own receiver. Also, due to the lower update rate you're going to have to use to avoid APRS network issues (typically APRS trackers might only beacon once every minute), this means you may not have as much positional information close to landing.

There are a few groups in the US that are now ditching APRS in favor of running Horus Binary ( https://github.com/projecthorus/horusdemodlib/wiki ) since one base station in a good spot will provide as good coverage as many APRS igates, and since they don't need to worry about affecting the APRS network, they can run high update rates. The group that launch with Mt Carmel College in San-Diego is a good example of this.

73
Mark VK5QI



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Patrick van Staveren

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May 9, 2024, 9:14:45 AMMay 9
to UKHAS, Mark Jessop
You're absolutely right Mark, I should work on a Horus 4FSK transmitter.  Thanks for the reminder!

I intend to fly multiple payloads - a LoRa tracker that I trust and gives me frequent transmissions, an APRS transmitter (honestly for the novelty of doing something that's been done before), and I could add a Horus 4FSK tracker to the list.  Too bad I haven't managed to catch any RS41s here; all I have is a pile of DFMs and a half hacked DFM firmware that I don't trust to fly. 

Erm, wait, I just re read https://github.com/mikaelnousiainen/RS41ng - DFM17 support added!? News to me. That's amazing news! I have a bunch of them. I'll give it a go!

Thanks.  I might see if a DFM can transmit APRS too - maybe I'll fly two.  Looking at the DFM it looks like it has an output filter that'll attenuate anything far off it's native 400MHz so 2m might not fly well, but I did manage to send some APRS packets with one...so I'll see :)

Cheers
Patrick


Patrick "Trick" van Staveren
https://trick.vanstaveren.us/

Mark Jessop

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May 9, 2024, 9:52:45 AMMay 9
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Don't transmit on 2m with a DFM17 without some other filtering - the harmonic content is... not good.

Also, be warned that the battery chemistry of the CR123 Lithiums used in them (even the Energizers) is not the same as the Energizer AA Lithiums we all know and love. We have seen DFM17's fail due to low voltage mid-flight, so I'm not sure I'd be trusting them as a primary tracker just yet!

73
Mark



Mark Goergen

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May 9, 2024, 10:26:33 AMMay 9
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I've been using Horus for a year now and love it. Constant updates compared to APRS, landing predictions in Sondehub, a really inexpensive ground station and chase receiver. I have not recovered an RS41 either, but you can buy them on Ebay for $30 or so. Programming them is a bit of a pain, but find a friend who is already set up and convince them to program for you. I'm lucky - my friend programs for Buffalo Wings and an extra RS41. And I get APRS out of the RS41 also. The ridiculous amount of data available about your flights from Sondehub is impressive. 

Mark KM4DDY

Mark Goergen

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May 9, 2024, 10:32:34 AMMay 9
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Speaking of the Sondehub. When I was a US DoD contractor, launching really large He balloons, we paid several hundred thousand dollars to develop a program that doesn't really do more than Sondehub. Having real-time knowledge of the landing site for a cut-down is very valuable to me.

Gavin Gill

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May 9, 2024, 4:54:27 PMMay 9
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Not sure if this is any help or not as I’m still learning the ropes and aprs is not my forte yet.

But uputtonics who I think are uk based( might be easier to ship to the us, not sure) sell these aprs modules which work with a flex track which runs off a pi.
Maybe it will work without a flex track in the middle but you may find it interesting…
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Rick Eason

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May 9, 2024, 4:55:15 PMMay 9
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I used to buy the Radiometrix for APRS (US) from https://lemosint.com/,
but haven't bought any in few years. You might call and check their status.

Rick
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Anthony Stirk

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May 9, 2024, 5:01:09 PMMay 9
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Hi Uputronics here,

You can pretty much straight swap the HX1 for a Dorji DRA818V module and its frequency agile unlike the HX1. Our FlexTrak APRS board is designed for use in conjunction with the Flextrak tracker but I guess with some wiring could work independently and with another microcontroller. 

Cheers

Anthony 

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Patrick van Staveren

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May 17, 2024, 4:48:41 PMMay 17
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Thanks for the post about 2 meters Mark - I had assumed this would require hardware modifications on the output side of the radio as my tests on 2 meters (even less scientific) were not great.

Flashed my first DFM17 with rs41ng this week - up and running quick!  I'll give it a go as a secondary payload for sure.

Cheers
Patrick


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