[FoxHunt] ELT Training

[Anthony Levand]

Ideally that would be the case, however the higher frequencies have more mutipath
and attenuation from vegetation. At 3 times the fundamental, an object 1/9 the area
will reflect, and absorb. From my experience a good attenuator on 2.5 meters would
be better. I just modified an Icom radio for a fellow hunter. I put 3 gain controls
on it. We tested it on his set up, a 4 element Yagi pointing at the 5/8 vertical on
his hood 2 feet away. Running 50 watts the signal could be squelched out with only
half the attenuation dialed in. An on-scale reading was easily had.

The Park Service uses a broadside array of 2 Yagis on their vehicles. The radio tag
signals are weak. The azimuth pattern is sharper than a single boom of the same gain
and feed line is run away nicely perpendicular. Many a time I am the only one that
can get a bearing at the hunt start.

Tony
AA9CC

sdonnell wrote:

> Hi, Have  been reading the ELT thread w/ great interest. Much of which we can
> directly relate to; When we were first licensed as a Ham 25 yrs ago, we did a
> bit of "fun" foxhunting w/ some  friends, using just a "ZL Special" antenna. For
> over 15 yrs now weve been an active member of CAP, doing mostly Comm and LOTs of
> Ground DF. We typically average 6 - 10 missions per yr.While(fortunately) we
> have only been involved w/ a few "actual" search missions, we always try to keep
> in mind what COULD be the result whenever we are called out to DF a signal. In
> truth, this is part of the "hook" that makes DFing such a challenge and
> interesting: You absolutly never know where you are going to end up or what you
> are going to find as the source of the signal. Weve tracked beacons in all typs
> of weather, and at all times of day and night, and while always keeping in mind
> the VERY serious nature of of activity, I can also say that its the most fun
> that you can have w/ a radio and antenna,,.But I suspect that many of the list
> members already know that part,.
>
> I living near the coast as we do, a good many of the false alarms that we see
> are from boat EPIRBs, whch also operate on 121.500. While (thankfully) seems to
> be dropping back, in recent yrs as much as 3 out of 5 DF searchs that we went
> out on, ended up being an EPIRB. Most of which were improperly disposed of older
> beacons that were thought to not be of any use,,,,. While the newer generation
> "406" beacons should help reduce this issue, weve already had 2 close encounters
> w/ these type as well.
>
> While CAP has many dedicated members, and provides very good training programs,
> I think that one of their primary limitations(as far as DFing goes) is that they
> only have one tool in their bag of tricks, that being the Ltronics ELPer. While
> an ELPer can be very effective, Ive seen many instances where that is not the
> case. It also helps be familiar w/ the readings that you get from it, and how to
> properly deploy it, which can be hard of you only use it once or twice a
> yr...Ive also think that (more)CAP Ground  DF training should focus on DFing w/o
> assistance from aircraft. All too often, Ive seen training scenarios where
> Ground teams are brought in(directed from the aircrew) simply to "finish off"
> locating the target which has already been IDd by the aircrew. As this does very
> little to hone the skills of the ground team... In all of my experience to doing
> Ground DF, Ill say that having an aircraft avaible for DF, can be an EXTREMELY
> useful asset, and save countless hours in searching. And that there are many
> aircrews that are VERY good at narrowing down the location of a signal. However
> in reality, there are also many instances where using an aircraft for DF is
> simply not an option, and the job falls entriely on the Ground team. Or that by
> the time an aircraft  takes off, the approximate location of the signal has
> already been determined.
>
> One recent addition to my Dfing "tool kit" is an Arrow Antenna yagi. In speaking
> w/ the Co owner at Dayton, I heard that they already had made antenans for
> beacon DFing. But I ordered one that had 3 elements cut for 121.5, AND 4
> elements for 243 on the same boom, similiar to their OSCAR antenna, but w/o the
> phasing harnass. I havent(yet) tried placing both sets of elements on the boon
> at the same time, I simply wanted the versatility of being able to have a 121 or
> 243 antenan available. I also figured that using a 4 el 243 yagi could,be useful
> in geting a tighter bearing plot, and would be a bit easier(lighter) to use. It
> could also be used to track a 243-only beacon, however unlikely. Besides the
> additional signal gain of the 3 el yagi, one distinct dividend that Ive  gotten
> from using it, is from being able to easily swap from vertical to horizontal
> polarization. In two search mssions over the past yr, this has enabled us to get
> a bearing on a very weak signal that our standard ELPer would not hear at
> all...I highly recomend that anyone who does 121.50 DFing, to give the Arrow
> Antenna a try.
>
> Another part of our bag of tricks has been in tracking the beacon signal from
> one of its harmonics; I keep 486.00 Mhz in one memory channel of my vehnicle's
> IC-R100, right next to the channels where 121.50 and 243.00 are kept. I have
> found that by simply switching from 121, to 243, and then 486, and using the
> Attenuator as well, we can usually get to within one hundred feet of a beacon,
> w/o ever getting out of the car. Which can be kind of handy  when its raining or
> have 30 below zero wind chill... But our secret zinger, is with the use of a 5
> element yagi designed for 800 MHz. fom using this, w/ an HT or scanner set for
> 850.500(121.5 x7), we can easily pinpoint a specific house, or vehicle(or
> airplane or boat). Then for the final "kill", some variety of Field Strength
> meter, either one of those new consumer "bug detectors" or a modified VE2. In
> many situations, its one thing to "know" where a beacon is, its another to
> actually get your hands on it, such can be the case in finding out where it is
> stored on a large boat. This can also be helpful in verifying which specific
> boat or plane, or car the beacon is in. We once tracked a beacon signal to a
> house. The owers, who lived on the first floor had no idea as to what an ELT
> was. When we placed a handheld frequecny counter to the downstairs ceiling and
> got a "121.500" reading, we knew we had it nailed. The beacon was found on the
> floor of a recently vacacted appartment. One word of caution though, from what
> Ive seen in the new "406" beacons, besides the much lower power 121.5 signal,
> they have almost NO harmonic content, even on 243.0.
>
> Id be quite interested in hearing form other CAP members about these ideas or
> what DFing techniques they find useful.
>
> Steve Donnell
> WA1YKL/Abenaki 102
>
> "J. Craswell" wrote:
>
> > Well sounds like that would be a good scheme.  Any Hams who can outdo us
> > will of course have to be "drafted."  <grin>  Of course a lot of our crew
> > are Hams also and were previously drafted <grin>  Per the comment about high
> > percentages of false alarms we have had a good number of non distress
> > missions as well.  I think the percentages are 90+%  We worked on one really
> > nasty crash a while back and my fervent hope is that it will be the last.
> > But, we will continue to work as if all are real.  A very bad idea is (I
> > think) to go out on a ELT Mission-Foxhunt and assume it is another in a
> > series of false alarms.  What is it they say about assume?  It makes and ASS
> > or U and ME? <grin>
>
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