[usa2003ardf] Re: Transmitters

Homingin at aol.com Homingin at aol.com
Sat Aug 9 00:25:45 CDT 2003

Today I'm sorting through over 300 snapshots of the action at the 
Championships.  It's great fun to everyone in action again, and I hope to get a bunch of 
these photos onto the Web in the next couple of weeks.

Congratulations and thanks once again to Bob, Dick and everyone else who made 
the 2003 Championships an overwhelming success.  This will be very tough to 
top next year.

Regarding Ken's equipment questions:

My ammo cans have both two meter and 80m transmitters in them -- there's 
plenty of room for both.  They have permanently-mounted PicCons and can be easily 
configured for either band.  Actually, it's possible to run both bands 
simultaneously!  The 80m RF deck is an ON7YD board and the 2m rigs are made from 
surplus (free) 25-watt Yaesu business-band (151 MHz) mobile transceivers  The 
Yaesu final RF stages are disabled and the drivers run directly into the output 
harmonic filter.  These drivers are capable of 7 watts output, but I added DC 
regulators for adjustment range from 100 mW to 3 watts.  (Added advantage of 
regulators:  power stays constant as batteries discharge)  At these power levels, 
I don't worry about blowing an RF transistor if the antenna is removed or 
shorted.  (That happens!)

It's very important to build your foxboxes to be as rugged as possible, for 
reliability.  They will get dropped, kicked and otherwise beaten up.  I added a 
plate and foam padding to keep the battery from bouncing around and crashing 
into the RF decks (which are mounted on the lid) when that happens.  PicCons 
are hard-wired to the plates, along with a homebrew battery fuse (AWG 32 wire). 
 All wiring is tied down so it can't won't flex and break.  I eliminated all 
switches, fuseholders and most jacks, because they can get intermittent.  
Everything is soldered in except for the batteries.

There's no external on-off switch, as it would be too easy for a fox to get 
turned off during the hunt, accidentally or deliberately.  For urban parks, add 
provisions to secure the ammo box with a bicycle chain to something immovabl
e.  (One of my older mini-foxes without a chain got stolen at our last practice 
session.)  There's an ID sticker with my pager number on each fox in case the 
Homeland Security folks see them and get nervous.

Photos and details of my boxes, including a circuit to separately key the 
oscillator and final stages of the ON7YD TX to eliminate backwave during OFF 
time, are in articles I wrote for 73 Magazine, March 1998 and November 2000 
issues.  (Some of you might not know that 73 has had a column on RDF topics every 
month for almost 15 years.  Check it out at your local ham store or library.)

Regarding PicCon programming, I prefer a slightly different method from 
Marvin.  I use the A4xxxx command to get the foxes to start in sequence at hunt 
start time.  Delayed start saves battery life and prevents hunters from getting 
advance bearings as they arrive.  Once I got the hang of it, this has been 100% 
reliable, with no incorrect starts or sequences.  Programming is done at home 
before I head for the site, as the boxes don't have (or need) receivers for 
remote programming.

After putting them into the IARU mode (D1-D5) and entering the callsign, all 
five PicCons are programmed as follows:

A20057 (57 seconds of MOx before ID)
A30500 (5-minute cycle)
C423# (sends MOx repetitively followed by ID)
A50360 (Turns all foxes off after four hours of hunting*)

*There is a firmware bug in some PicCons such that if you set A4 or A5 to an 
exact number of hours (e.g. A50400), it defaults to zero time for that 

Then I program each fox with it's own turn-on delay.  For instance, if I sync 
them at 6:59 AM for a hunt that starts at 9:30, they are programmed this way:

MOE:  A40231
MOI:  A40232
MOS:  A40233
MOH:  A40234
MO5:  A40235

Then I sync-start them all simultaneously with an octopus audio cable and 
TouchTone "1"

Joe Moell K0OV

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