Radio Direction Finding


Radio Direction Finding is a very popular hobby here in Denver and around the world. The one nice thing about Direction Finding, DF’ing, is that it can be very inexpensive and does not require a Ham Radio License to participate since you only receive. But, with any hobby, the sky is the limit on the price of equipment and the number of different setups you desire. This includes different setups for mobile in a car or while walking. Many items, if not all can be homebrewed. Because I am new to Ham Radio, I have little experience in making my own stuff with the exception to some of the antennas I use. Below I will show you some pictures of equipment that I use on my DF’ing hunts.



Garmin Etrex Summit


This is my GPS unit that I use to make sure I don’t get lost and to take bearings. I mainly use the Summit for balloon chasing with EOSS, Edge of Space Sciences group. I usually participate with the tracking and recovery group. We are responsible for tracking the balloon through DF’ing from the beacon that is on every payload we launch. When the trackers are called to provide a bearing, I use the Summit in conjunction with the Tape Measure Beam and VK3YNG Sniffer 4 to get a bearing on the DF beacon. The Summit has a built in compass that works without input from the GPS system, which means I do not have to be moving to get a bearing. We provide these bearings so we can provide regular updates to the ground station, which in turn update the FAA with the projected flight path and landing spot. After the payload has landed, we recover the payload for the group that has contracted us to launch and recover their experiments.



Tape Measure Beam


This Tape Measure Beam was very light, cheap, and easy to make. The tape measure beams can be bent and inserted into the openings of the PVC. This makes for easy transportation. There is also a beneficial side effect. Once folded, the beams are stronger and add about 15 dB of attenuation. The attenuation is helpful, but being able to stand out in strong gusty winds while taking bearings is very much appreciated. The antenna has a gain of 7.3 dB with a front to back ratio >50 dB, which gives a huge notch in the pattern at the rear of the antenna. More information and specifications for making it can be found here. Below are some pictures of the antenna and the Sniffer 4, a dedicated radio receiver.



Tape Measure Beam handle and mount



VK3YNG Sniffer 4


This is a great piece of equipment. This sniffer has the capability of listening to any frequency in the 2m band, 143.000 – 149.995 Mhz, and the aircraft band, 120.000 – 129.995 Mhz. In addition, the sniffer can receive in AM, FM, and in tone modes. The tone mode gives you the ability hear the direction of the monitored signal with the common whee-whoop tone which you just point the antenna towards the highest pitch you hear. The sniffer is quite expensive, but actually well worth it for the serious DF hunter. It is made by hand by Brian, VK3YNG, in Australia. I am lucky enough to have number 58. A friend of mine, Larry Noble, N0NDM, was lucky enough to get the prototype when he participated in the World DF’ing Championship in Slovakia. I think he got it for helping one of the guys from The Australia team with some equipment, and they returned their appreciation. More specifications and ordering info can be found at their website.



VK3YNG Sniffer 4 on mount



Tape Measure Beam and VK3YNG Sniffer 4



MFJ frequency counter



The freq counter is used to determine what frequency a certain object is transmitting on if you are not sure. It can also be used to get really close to a transmitter with proper attenuation and get a pinpoint signal. These are quite cheap and have a range of about 200 – 300 feet with the stock antennas. If you were to attach a directional antenna such as a beam or quad, you will get much better range and accuracy.




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