Fox Hunting 101 - Part 2

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#1
Yes, you "can" find that fox!
When a fox hunter is getting very close to the fox (hidden radio transmitter) the signal is very strong and seems to be coming from every direction. It then becomes very difficult to pinpoint the precise location of the fox if it is well hidden. While a directional antenna, such as a Yagi, is useful in finding the general direction of the signal when the fox is some distance away, it will not give any directional assistance at all when the fox is very close.


What we need now is a method of dramatically narrowing the angle within which our receiver is able to pickup a signal. The solution is very low-tech and costs nothing. First, we must remove the antenna from our receiver. It is usual to use a handheld transceiver for this, so we take the rubber-ducky off our HT and set it aside. An antenna is not needed when we are very close to the fox. The signal will be entering the HT through the case.


Our free, low-tech piece of fox hunting kit is a tall, narrow metal can. I use a can from a bottle of beer that came in special Christmas packaging. It is 13 inches tall and 3.5 inches diameter. My HT fits nicely inside the can. If you don't have such a can available you can use 3 baked bean cans. Remove both ends from two of the cans and just the top from the third can. Now join all three cans together in Red Green fashion (i.e. use duct tape) and drop your HT inside. Be careful the HT doesn't slide out while you are moving the can around.


The can acts as a crude Faraday cage with a narrow aperture. The directionality of this arrangement is really quite good. You should now be able to zero in on the fox very easily.


Why don't we get a group of GBARC members together to do some local fox-hunting. Experienced fox-hunters can help train newcomers in the techniques used. A typical event lasts a couple of hours and ends when a hunter successfully tracks down a hidden low power transmitter. Please reply to this post if you would like to know more, or get involved.
John, VA3KOT
SKCC #11989T NAQCC #7155 FISTS #19777
May the Morse be with you.
Reply
#1
Yes, you "can" find that fox!
When a fox hunter is getting very close to the fox (hidden radio transmitter) the signal is very strong and seems to be coming from every direction. It then becomes very difficult to pinpoint the precise location of the fox if it is well hidden. While a directional antenna, such as a Yagi, is useful in finding the general direction of the signal when the fox is some distance away, it will not give any directional assistance at all when the fox is very close.


What we need now is a method of dramatically narrowing the angle within which our receiver is able to pickup a signal. The solution is very low-tech and costs nothing. First, we must remove the antenna from our receiver. It is usual to use a handheld transceiver for this, so we take the rubber-ducky off our HT and set it aside. An antenna is not needed when we are very close to the fox. The signal will be entering the HT through the case.


Our free, low-tech piece of fox hunting kit is a tall, narrow metal can. I use a can from a bottle of beer that came in special Christmas packaging. It is 13 inches tall and 3.5 inches diameter. My HT fits nicely inside the can. If you don't have such a can available you can use 3 baked bean cans. Remove both ends from two of the cans and just the top from the third can. Now join all three cans together in Red Green fashion (i.e. use duct tape) and drop your HT inside. Be careful the HT doesn't slide out while you are moving the can around.


The can acts as a crude Faraday cage with a narrow aperture. The directionality of this arrangement is really quite good. You should now be able to zero in on the fox very easily.


Why don't we get a group of GBARC members together to do some local fox-hunting. Experienced fox-hunters can help train newcomers in the techniques used. A typical event lasts a couple of hours and ends when a hunter successfully tracks down a hidden low power transmitter. Please reply to this post if you would like to know more, or get involved.
John, VA3KOT
SKCC #11989T NAQCC #7155 FISTS #19777
May the Morse be with you.
Reply
#2
Hi John,
That sounds interesting, and I'd like to give it a try when one is planned. So far I still don't own an HT of any kind.  Are the foxes generally built using only 2M? Or would I need to plan for a dual band HT?
Thanks,
Dan
Reply
#2
Hi John,
That sounds interesting, and I'd like to give it a try when one is planned. So far I still don't own an HT of any kind.  Are the foxes generally built using only 2M? Or would I need to plan for a dual band HT?
Thanks,
Dan
Reply
#3
Thanks for replying Dan. I prefer VHF over UHF. VHF penetrates obstacles like trees better than UHF. To participate in a fox hunt you can use any receiver that is capable of tuning the ham bands. Even a simple scanner works. Most hams end up owning multiple radios so you could probably borrow one for the event.

Our president Tom has expressed  his support for a fox hunt so we may be able to get enough people interested soon to put one together.

John, VA3KOT
John, VA3KOT
SKCC #11989T NAQCC #7155 FISTS #19777
May the Morse be with you.
Reply
#3
Thanks for replying Dan. I prefer VHF over UHF. VHF penetrates obstacles like trees better than UHF. To participate in a fox hunt you can use any receiver that is capable of tuning the ham bands. Even a simple scanner works. Most hams end up owning multiple radios so you could probably borrow one for the event.

Our president Tom has expressed  his support for a fox hunt so we may be able to get enough people interested soon to put one together.

John, VA3KOT
John, VA3KOT
SKCC #11989T NAQCC #7155 FISTS #19777
May the Morse be with you.
Reply


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