[Milsurplus] parachute mobile

[Sean Kelly]

> http://boeing377.googlepages.com/parachuteradio


Was that you in the pictures? How high did your heart rate go during the descent?

 

> Would really like to use a mil radio on one of my parachute mobile comm jumps, but my PRC 74 is just too big and heavy. Any suggestions? It is a lot of fun to do QSOs under canopy even if it was likely not done by the military.


Well, one thing you don't have during the usable part of a parachute jump is the ground to refract the HF signal back up towards the part of the sky that will cause the signal to bounce off of the ionosphere and land where you want to communicate. That said, I believe that air mobile operations require less power in spite of that. But the only example I can come up with is the 100 watt AM and CW liason sets installed in allied bombers of WWII, which I expect could communicate back to their bases in the United Kindom from deep inside of Germany.

 

I think the best factor that could improve the chances of success in this situation is planning. That is, planning to have people who want to communicate with you so that they know when and what frequency you plan to communicate on. The next thing is a suitable rig. If you are willing to spend the time reading the ARRL Handbook, you can build a small crystal controlled transmitter and transmit-receive relay, then use a commercial receiver such as a used Radio Shack DX-390. Or you could get one of the currently-made HF transceivers. I know one of them has an internal battery, solving the problem of where to put it.

 

Antenna issues should be easily solved by having a weighted lower half dangling and an upper half supported by it's own small parachute. Perhaps some fishing weights will allow you to throw this far enough so that it could rise to a position above your main 'chute if that is safe.

 

> I have been reading about SOG (Special Observation Group) HALO jumps made in Viet Nam. The jumpers reported being supplied with a beacon (for the leader) and DFs?(for the rest) ?that looked like converted BC band transistor radios. The gear was used ?to locate each other after landing in the jungle. 
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> Any ideas on what this gear was?


"(b) No amateur station transmitting in the 1900-2000 kHz segment, the 70 cm band, the 33 cm band, the 23 cm band, the 13 cm band, the 9 cm band, the 5 cm band, the 3 cm band, the 24.05-24.25 GHz segment, the 76-77.5 GHz segment, the 78-81 GHz segment, the 136-141 GHz segment, and the 241-248 GHz segment shall cause harmful interference to, nor is protected from interference due to the operation of, the Federal radiolocation service."

 

That paragraph above is from the Part 97 rules. Probably the converted BC band radios were converted to work above 1900 KHz. The antenna in a portable BC band radio exhibits a deep null when the axis of the loop is pointed towards the station. So, shoot a bearing on the directions of the null (there are two), walk far enough for the bearing to change, shoot another bearing to figure out which of the two directions the transmitter is at, and close in on the transmitter, using the receiver to make sure you are staying on the right heading.

 

The transmitter was probably contracted and designed from scratch.

 

Please keep me apprised.

 

Sean Kelly