[FoxHunt] Moded ELTS

Sun, 24 Mar 2002 13:04:13 -0800

Rick..

Great response..and yes there is a real difference between
T-hunting for fun and hunting for real in the learning and
zeal of the team. On the other hand, I went T-hunting with
the FCC once in their fancy $20K equipped car and that was a
real joke. They are bright, fine people, just too much
paperwork and not enough field practice. 

In SoCal the serious HAM hunter (or anyone else--no license
required) can go on a hunt three times a week and on a once
a month basis go on a really tough hunt. I have been doing
the monthly for over 20 years and have really seen some
tough hunts and some tough hunters. The only differences
between the CAP ELT problem and the HAM hunt is the CAP
transmitter is continous and there is usually only one, but
it is usually in a location where man has not gone before.
The tough monthly hunt is usually 2 or more (up to a maximum
of 26) transmitters all on the same frequency and
transmitting on duty cycle usually 20% and unsychronized.
Now you need to be able to copy CW to tell them apart. 

I just got off of a hunt (Last night) where there were 5+
transmitters, all on the same frequency, three were
sychronized, all in low local altitude (making local
reflections) positioned in the Angeles Forest (2000-11,000
ft) in valleys giving a lot of long-range multipath. I don't
think I got a bearing that was within 5 degrees all night.
The only salvation that made the hunt even possible was the
fact that the transmitters were hidden by people and
therefore were in places where people could get to. This
"benefit" is not available to the ELT and this is a real
benefit that eliminates about 90% of the bad bearings. 

There is no substitue for training and more training and
even more. Knowing your equipment so well that it is never
your focus but an extension of your senses and your focus is
in trying to understand the data.

Another whole school of T-hunting are the animal people.
Locating a wolf wearing a 0.10 Watt collar with a 1%
dutycycle is not easy when you consider that a typical wolf
will move 10-25 miles/day. 

Bob, WB6JPI

de Rick K5RIC wrote:
> 
> Be careful attaching non LPER Antennas to your LPER DF unit.  When you are
> in the DF mode DC  power will be sent up the coax, if you have a grounded
> antenna, you my damage the LPER unit.
> 
> As a ham I am sorry to say, I have over 30 years experience in SAR, and I
> have never seen a ham DF team that could hold a candle to the CAP teams I
> have worked with.  Our cadets were some of the best DF teams I have ever
> worked with, we have even used multiple ELT Tx's and they found both with
> no problem.  I will note that I was in Texas CAP units in those days.  My
> CAP job covers six states now and I think most will still do very well.
> Even when we used 121.6 we held DF training every three months or so.  But
> we got real exercises bi-weekly, but as noted most were on the ramp.  I
> will note my first CAP DF mission was to find a real crash, but in West
> Texas we had much fewer false alarms than most areas.
> 
> Here in New Mexico, SAR is run by the state police, and we have some big
> mountains, so as noted earlier many non CAP teams are active here.  This is
> just the opposite from Texas where CAP manages all non military aircraft
> search missions and CAP will be called for most non aviation rural SAR.
> Until recently CAP in NM did not have a qualified ground team.  One team
> qualified for ground SAR, but I have not heard if they are still active.
> As with any mountainous area, most aircraft crashes are during bad weather
> when the CAP can not fly.
> 
> I am sure some hams are better trained and qualified than any I have met so
> far, so I am sure some ham DF teams can do a better job than I have seen,
> but so far, I have not met them.  I did take some training from the group
> in Albuquerque and I am sure they are one of the teams that are well above
> average for hams.  I hope to see them in action some day soon.
> 
> One tip, one time we where Searching for an ELT and one of the LPER meters
> failed.  By this time we had determined the direction of the true signal
> path, so we were DFing, we found that in the DF mode, you can hear a tone
> when the two antennas are not the same distance to the TX.  But when you
> get the two antennas at the same distance the tone will vanish (in phase)
> This allowed us to keep working with that LPER.
> 
> My wife and I found a crashed aircraft that crashed in the restricted area
> around an Areostat radar site.  We used triangulation to pin point the
> crash site and guide the ground team to crash.  We could not fly in the
> area, but someone did and they crashed.  Triangulation from the air can
> eliminate faulty signal paths in less than 5 minutes.
> 
> rick sohl
> k5ric
> cap west 4
> 
> At 07:19 AM 3/23/02 -0800, you wrote:
> >
> >>
> >>Maybe this is a good idea or not: In using the ELPer in Rec mode, Ive
> sometimes
> >>noticed  that the signal "null" off the back of the antenna(opposite from
> the
> >>direction of the arrow,) seems to give a much sharper and more distinct
> bearing
> >>than the signal peak, in the normal direction. Is this a better way than
> using
> >>the signal peak?
> >
> >   I've not had good results hunting the null in an antenna pattern - at
> >   least not on VHF.  It is not always predictably straight off the back
> >   of the antenna (and can vary with frequency.)  But also it is very
> >   susceptable to being confused by weak reflections.
> >
> >   In general, a null can be much sharper than a peak, but it only takes
> >   a little reflection to shift it.  It is a good idea to know what the
> >   pattern looks like off the back of your beam, as, on occasion, it may
> >   be usable.  Just another trick to have up your sleeve.
> >
> >   The antenna for the LPER is not designed for a sharp peak, but rather
> >   for a clean pattern in DF mode.  For weak signal work, a larger yagi
> >   or quad comes in handy.
> >
> >
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