[FoxHunt] Moded ELTS

[de Rick K5RIC]

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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