[aprssig] APRS DFing SUCCESS with only an HT!

Scott Miller scott at opentrac.org
Wed Jul 25 16:12:18 EDT 2007

Transmitter hunting is still one of the best ways to get new people 
interested in ham radio.  It's also a useful skill, and there's 
absolutely no substitute for practice.

SAR teams in particular (the ones I've dealt with) seem to under-utilize 
their equipment.  You can do a lot better than the textbook approach of 
driving to a spot, taking a bearing, plotting it on a map, and 
repeating.  It just takes practice, and knowing how your equipment works 
and what it's capable of.

I miss the days of driving around town with big PVC quads hanging out 
the passenger's window, and then hopping out of the car to go sniff 
around with an HT (antenna off, 5 kHz off frequency, using body blocking 
to search for a null) to find some transmitter hidden in a field. 
Haven't had a good t-hunt around here in years.


Robert Bruninga wrote:
> To see a great view of DFing using only your mobile and an HT,
> see the 5 map views of my track while recovering a tiny balloon
> payload yesterday. (A key-chain 433 MHz oscillator and tiny
> balloon (no APRS)).
> These views are less than 100k images but very cleary show how
> easy it is to find ANY RF source without any special DF
> equipment, using only your mobile rig and HT with OMNI antennas.
> I have added this series of annotated map images and a
> description to my usual APRS DF-ing web page:
> http://www.ew.usna.edu/~bruninga/dfing.html
> Slide down about 70% down the page and look for HT-ONLY DF-ing:
> Remember, on the east coast we don't get many balloon launches
> because they all go out to sea.  So pardon my excitement.  But
> this experience again proves, that we can DF anything with just
> our own rigs if we just take the time.  I have been preaching
> this for years, (usually from the APRS perspective), but you
> simply don't need any technology.  Just your ear and the ability
> to HEAR (and mentally visualize) signal strength (quieting
> quality) and the patience to bracket the signal as you get
> closer.
> Bob, WB4APR
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