[W6YRA] UHF Kit Transmitter (rocket recovery beacon)

[Ryan Caron]

Eric (CC'ing ham club & other rocketeers),

Yes, I was able to place the http://fmtv.us/rf_beacon.html transmitter 
on NPS' rocket. It worked great! The flight was estimated to do 8 G's 
and reach 4000ft (they executed a turn with servo-driven fins). It was 
probably beeping away for an hour before it launched, and perhaps an 
hour afterwards by the time it was picked up and disassembled.

They placed the beacon inside their lower avionics bay (which stays with 
their motor - they fully separate and come down on two chutes), so the 
antenna was pretty close to threaded rods and other metal. Not ideal, 
but their body was fiberglass at least. Even when it was relatively 
close overhead (right when the chutes deployed) I could still only hear 
the first two tones. I think you guys can do a much better job with 
transmitter placement on the glider, but it will be important on the 
rocket body to get out of the carbon fiber and away from metal 
structure. Hanging on the descent lanyard is not a bad idea.

Anyway, once it landed on the ground, approx 5600ft away ENE of the 
launch site, I couldn't actually hear the beacon at all - even after 
removing my offset attenuator and horizontally polarizing the antenna. 
Their upper half had an even slower descent rate and traveled 6400ft 
away, and took a bit longer to find, so there is value in having 
multiple transmitters in different sections.

They had all sorts of expensive avionics (like a serious IMU) in the 
upper section though, so even though they knew it would travel further 
they didn't want to risk any incompatibilities. 50W TDP all told, and 
they cooled with dry ice (fantastic idea!).

Once I got within 4200ft or so of the lower section (these are all rough 
numbers based on Google Earth and remembering the terrain - no GPS 
waypoints) I started hearing tones again. The terrain was a gentle 
uphill slope, so if anything the receiver was being presented to me, but 
I did not have a visual despite no significant hills/valleys. Evidently 
it doesn't take much to block a ~50mW transmission just a few inches 
above the ground. Some scrub brush may be enough.

Since I was on foot, and the NPS guys had a van, they picked up the 
lower half when I was still about 3000ft away. At that point I still 
hadn't picked up the 3rd (highest pitch, lowest power) tone. So I didn't 
really get a chance to really try out the offset attenuator (useful for 
~500ft range, but you still can't find the thing). I did try it 
pre-launch, and in that case it worked pretty well (but that's cheating 
since I knew where it was).

and that will improve range, but there are higher power levels available 
to too if you need significantly more range than this.

I used my D72 HT for this, with your Arrow UHF antenna, but there's no 
reason you guys can't use one of my cheap Baofengs when you go to Utah.



A few suggestions for next time, these are all pretty basic RDF things - 
I'm just a bit out of practice.

1) head downrange and a little cross track in advance - the launch crew 
will get their own bearing by watching it on the chutes,  but since 
you're prepositioned elsewhere you can both go toward it and when you 
intersect you know you're in the right place. This is especially helpful 
if all you have is visual if the beacon broke (or you have unintended 
separations, etc).

2) a 2nd person with a radio & a yagi can also speed up triangulation

3) have some compasses, and voice radios to communicate with everybody. 
A few positions & bearings and someone with a laptop can estimate a 
position pretty fast using Google Earth.



The beacon & rest of the gear is at home right now, but I can bring it 
back to campus on Monday.

Ryan Caron
Associate Development Engineer
UCLA - Institute of Geophysics & Planetary Physics
Tel 310-267-0696   |   Cell 603-801-8233

On 4/5/2016 11:30 PM, ERIC HIDALGO wrote:
> Hey Ryan,
>
> Thanks for your help during the Hot Fire with the launch box issues.
> I heard that you were able to place the UHF transmitter onto a rocket also.
> Was the transmitter able to still work?
>
> Best,
> Eric
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