Janurary 2010 Foxhunt

Scores for last Friday nights fox hunt are as follows.  

TeamHunt 1Hunt 2Hunt 3Hunt 4Hunt 5Hunt 6Hunt 7TotalPlace

    Some history about why I have foxes on so many odd frequencies.   As far as I can remember the WIA fox, which we still use, was the first “dedicated” fox. This was originally on 144.480MHz. The frequency was most likely determined by the builder having a crystal on hand which could be multiplied to somewhere in the first 0.5 MHz of the 2M band.  Most people used AM receivers then so it was AM modulated. Also, as mobile phones, hhelds and even mobile TRX’s were unheard of or scarce it was usual to call in the hounds using the fox.   The availability of the IC202 in the 70’s caused the fox frequency of the WIA to be changed to 144.250Mhz. The 202 is a portable 2M SSB transceiver which tunes from 144.0MHz to 144.4MHz in standard form. It made a good fox hunt receiver. You could use it in the car and as a sniffer. If you replaced the PTT switch with a variable resistor you could also control the gain over a wide range.      At sometime I decided I needed a smaller fox.  To make this I rebuilt the TX driver stage from a Pye FM 734 two way radio, simply because I had the bits. In the process I removed the original FM modulator and added an AM modulator, ignoring most of the design rules for AM modulators. Hence it doesn’t work all that well. Never the less it’s caused hounds much frustration and given the fox much enjoyment over the years. It’s frequency was initially 144.480MHz and was changed to 144.250Mhz when the WIA fox changed. This is the small brown TX with the external AA battery pack. Power O/P is about 600mw.   Many years ago, Jack VK3WWW donated a Dick Smith 1watt FM TX kit to the foxhunt group, which I built. This ended up in a larger brown box as I included a 1200ma gel cell  and space for 1 or 2 other bits of circuitry which might happen one day. The frequency is 144.247MHz. Why. Simply because the crystal won’t work at 144.250 MHz even tho it was spec’d to do so. The highest it will go reliably is 144.247MHz.  If someone has a good supplier of crystals let me know and I’ll move it to 145.3MHz. I’ve been going to do this for some time but usually remember the day before the fox hunt……..  This TX is available to anyone who would like to borrow it for foxhunting purposes.   Sometimes a higher power fox is required so the larger black/brown fox came into being. The driver stage of this is home grown and the PA is from an FM 734.  Power O/P is 6-7 watts. The box was originally made so a battery charger could be included but recently I abandoned that idea and cut the box down to a more suitable size. I also added a clip on battery box. Frequency is 145.3MHz   A yr or so ago I needed a low pwr fox so the small black TX with the external 9 volt battery happened. The TX is basically the predriver stage from a Phillips FM747 UHF transceiver. Some unnecessary circuitry was removed with a hacksaw, a jumper or 2 added and I had a 40mw TX. It uses the crystal from the small  brown Tx mentioned above hence O/P frequency is 144.250MHz.  I later reinstalled the original crystal in the small brown TX and tuned it lower in frequency, i.e. 144.470MHz, as the TX produced a little more power there.   regards Ewen