Hello everybody and welcome back to the Everything Ham Radio Podcast! In this episode we are going to talk about Radio Direction Finding or the more fun term, Fox Hunting.
Fox hunting is the fun to do in your spare time thing that we as amateur radio operators use to train our skills in the event that we have to use those skills to track a downed airplane or harmful interference. In Radio Direction Finding or RDF for short, there are many tools that you can use to increase your chances on finding what you are looking for. You can use a directional antenna, an attenuator, or even just your body to help you determine where the signal is coming from.
For a yagi antenna you need a minimum of three elements. The driven element, the reflector and one or more directors. The direction of the directors is going to be the direction the signal is directed towards or being received the best from. Yagi antennas can be made from a bunch of different materials – things like aluminum or copper tubing, piano wire, a tape measure. The possibilities are only limited by your imagination and the laws of conductivity.
For any of you older people out there, you will probably remember using rabbit ears
on your TVs. If your rabbit ears were like mine, they had two vertical antennas that were used for the VHF channels and a round antenna for the UHF channels if memory serves me correctly. The round or ring antenna was a delta loop antenna. The signal was best received when the open part of the antenna was facing where the signal was coming from. Unlike the yagi antenna, the delta loop antenna will receive signals from two opposite directions.
Doppler Antenna Systems
The doppler antenna system is a pretty nice system, but it is geared more towards mobile use, I think. It would excel at a long-range fox hunt where you had to drive you vehicle quite a bit. Unlike using a yagi or a delta loop and having to stop every once in a while to get your bearings, or going to three different points and triangulating, you can just drive and the doppler system will constantly give you the bearing to the signal.
The parabolic dish is something that everyone show know about even if you don’t
know that you know. The parabolic dish is what is used for satellite TV(i.e. Dish Network, Direct TV, etc). This type of antenna is generally used for the upper UHF bands, but can be used on VHF to receive on.
Other Useful Equipment
An attenuator can be used between your antenna and receiver to cut down on the
signal that you receive. This allows you to see the difference in the signal when you are close to the transmitter.
Whether you use some type of mapping program or just a paper map of the area, this is a good thing to have. If you are looking over a large area, you can take a reading from three different points and triangulate the location of the signal using the map.
On the Homing In website, I saw a link to a page that says someone wrote a program that would automatically take a reading from a doppler system and transmit your location and the bearing to the signal over the APRS network.
- Local Club Events
- Local ADRF Training and Practice
- Harmful interference
- Search and Rescue – Planes, Boats, People, etc
More Than Safe Blog
My wife has started her very own blog describing our journey through the foster care system and things that happen to us and how we dealt with the situation. Some things may just be foster care related but some of the stuff can be used as just general parenting. If you are a parent or are interested in learning a little bit about the foster care system, please check out her blog at MoreThanSafe.com. If you like what you see, subscribe to her email list to get notifications on when she puts up something new.
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Amateur Radio Club Spotlight
- First Monday of the month at 7 pm at the Red Cross Building, 1050 Fuller Ave NE Grand Rapids, Michigan 49503
- No Club Nets Listed
- 147.260 + PL 94.8
- 444.400 + PL 94.8
- Ham Fest – Sat, Sept 24 from 8 am to 1 pm. It will be located at The Home School Building, 5625 Burlingame, SW, Wyoming, MI, 49509. $6 tickets at the door.
- Open Radio Room – Red Cross Building, Every Wednesday Night
- Michigan QSO party
- Field Day
- Fox Hunting – More Info
- VE Testing – 2nd Friday at 6:30 pm at the Red Cross Building
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Until next time…
73 de Curtis, K5CLM