[OZAPRS] Re: Packable Tracker

[vk7arn]

I've put some pictures and notes on the APRS BakPak tracker here
http://tas.wicen.org.au/APRS/aprs_bakpac.html.  Seems to work without RF
feedback OK now at 4W.  Thanks for the contributions, some of which (those
suited to the concept) I'll incorporate.

Interested in any ideas for the TT config.  Would like it to cut back beaconing
when not moving, without having to switch off.  Currently have it at 120 seconds
with a slow speed of 1 mph and 30 seconds at 2 mph (recognising that it's use
will be short term "on event").  Min. Turn Angle 30degrees, Turn Slope 150, Min
Turn Time 10 (don't ask me why - it's a stab in the dark!)  Suspect the maths
won't work with only 1 mph between Fast and Slow. It's set for alternate digi
paths of WIDE1-1,WIDE2-1 and TAS3-3.

Roger vk7arn

PS Thanks Sasi for the Foundation CD comment.

-----Original Message-----
From: Sasi Nayar [mailto:sasidiver at yahoo.com.sg] 
Sent: Wednesday, 7 May 2008 16:11
To: ozaprs at aprs.net.au
Subject: [OZAPRS] Re: Packable Tracker


G'day Roger and others,
I have been trying to upload the pics when this discussion started with no luck.
I have finally managed to do it a short while ago. I have two units that I made
up. One is in the car with an average regulator to drive my Maxon radio from the
car's cigarette lighter socket. 
The second one was designed to be portable. I assembled it late last year. I too
had issues with RFI. As you found out, lots of long ferrite rods made the
difference. Shortening the power leads too made a huge impact. Some pics are
uploaded at http://picasaweb.google.co.uk/sasinayar/APRSPortablePack

Yes, it is an overkill to use a 7Ah battery, but then I am doing some
trials from rescue boat for the local sea rescue group. 
Would love to see what you come up with
73 and good luck
Sasi
VK5SN
http://www.findu.com/cgi-bin/find.cgi?call=vk5sn-9
 
PS : Some one handed me a copy of your Foundation Licence CD-ROM. Must say it
was a brilliant piece of work!


---------------------------------------
Date: Tue, 6 May 2008 23:17:02 +1000
From: "vk7arn" <vk7arn at bigpond.com>
Subject: RE: [OZAPRS] Packable Tracker
To: "'Rob Heyer'" <vk2xic at yahoo.com.au>,    "'Australian APRS Users'"
    <ozaprs at aprs.net.au>
Message-ID: <001c01c8af7b$79109ff0$0500000a at Roger>
Content-Type: text/plain;    charset="us-ascii"

Hi Rob
It's good to know I'm not the only one with an RF feedback problem!  I've
changed my concept and now have the Puxing PX777 and TT3+ in a "rehydration"
back pack with bladder removed - and it's working on low power.  Initially I
used the plastic lunch box approach and overcame some of the RF problem by
lining the box with aluminium foil, but found I still had to put the GPS at
least a metre away from the radio antenna.  The purpose of the set up is to use
pedestrian or horseback mobile and the lunch box needed a backpack to carry it
anyway.  Opening specials of a new Anaconda store in Hobart included
"rehydration" packs for $20 which seemed to lend themselves to the purpose,
given outlets for drinking tubes and filling etc.  After much sewing to make an
insert with appropriate pockets, the result was an RF disaster.  Double lots of
ferrite on every lead (GPS, Tx, Rx and power) and it now works fine on low
power. (The power lead ferrite seemed to have greatest effect). I have read that
a similar problem was solved by placing the TT in a metal box inside a second
metal box and providing a common ground to all.  I'm hoping to achieve the same
with aluminium foil.  Shopping for heavy duty foil tomorrow.  Also have a
problem with the Byonics supplied TT to Kenwood HH lead which sticks out at a
right angle to the radio and therefore takes up space and is vulnerable. Waiting
for delivery of a right angle plug from Argent Data Systems.  The foil lining
will hopefully also assist the antenna.  I've made up an aluminium bracket with
a BNC connector which, together with the coax, fits through the drinking tube
outlet to sit on one shoulder (ear fryer).  The bracket extends inside and
across the top the back pack.  The aluminium foil will be in close contact with
the bracket, hopefully to form a ground plain of sorts.  The antenna is a
Nagoya  NA-702 BNC dual bander approx 300mm long.  The Byonics GPS is Velcro'd
to the other shoulder strap, with the lead passing through the second drinking
tube outlet on that side.


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