Have you ever participated in a T-Hunt/Fox Hunt?

How many times have you participated in a Transmitter Hunt?


  • Total voters
    20
  • Poll closed .

vagrant

ker-muhj-uhn
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I am curious how many RR members have actually participated in a transmitter hunt and if so, how many. If you have had to do this in a professional capacity, please provide some details on the equipment you used.
 

mmckenna

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SNCZCA01DS0
Professionally.
Started off with a spectrum analyzer to try and determine if what I was hearing was actually right on our repeater input frequency. It was.
Used a directional antenna with the spectrum analyzer, but quickly discovered that a hand held radio with an RSSI display in dB made life easier.

Took a long time since it only transmitted a few times during the day. Had to set up in locations that would allow me to get a fix, then slowly narrowed it down. Probably drove about 400 miles total trying to triangulate it. Once I had it narrowed down, I put the regular antenna on and started walking around using my body as a shield. When I got close enough, removing the antenna helped.

As for the Yagi...
I needed one quick and didn't have time to wait for our glacial paced purchasing system. So I made one out of some PVC pipe and an old harbor freight tape measure. Worked well enough for what I needed, and I could just toss it in the back of the truck without worrying about damage.

Tried to get some hams to participate, but no luck, they all got flakey.
 

N8RDF

(vanity call, "Radio Direction Finding")
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Aug 31, 2009
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Brighton, MI
I began 2m foxunting with a ham buddy and the metro Detroit SMART repeater gang in the late 70's. That (and the no-code Tech option :cool:) motivated me to get my license (then N8NTC, now N8RDF). I started with a yagi and scanner, then another ham gave me an old W6AOP doppler (excellent), a CMOS kit version of a Roanoak. After decades of occasional ham foxhunts, lots of VHF/UHF random tracking on my own and two "semi-pro" (unpaid, unofficial searches for a rogue repeater site and a daily strong interference issue on a DPW channel), my preferred mobile setup is:
KN2C DDF2020T Doppler with GPS (great hardware, antique pc software, modified for front panel calibration)
EA270ZB13 2m/440 Yagi, horizontal polarization (mast through the car roof, hand turned)
RF rotary attenuator, 100db, 10db steps (for yagi)
BCD-996XT scanner with antenna switch for doppler/yagi above
VK3YNG 2m (ONLY, excellent) ARDF Receiver or HT/Scanner plus attenuator and handheld Arrow Antenna(s) - very good
RF detector meter with variable gain amp (homebrew) and 1/4 wave mag mount antenna - great for determining when to start foot search

Other stuff I've tried:
KerberosSDR - great idea, probably the future tech of RDF. Software too cumbersome for real-word use. Wish they'd update/simplify it.
RTL-SDR - great addition for precise (relative) signal strength checks
Handheld Scanner with AGC voltage-to-frequency (tone) circuit - extremely effective (homebrew)
Ramsey Doppler - seems very good, but I don't have many hours on it, awkward mobile mounting
(old) Doppler Systems DDF-500x - excellent if you can find one that hasn't been transmitted into
(old) Regency (for external Marine radio) with Adcock antenna - maybe fine over water, horrible for mobile, avoid
(old) Agrelo DF Jr. - only tried once, OK but rare
(old) Dick Smith - OK but very quirky, needs mods that can be found on the web
APRS DF reporting - great, but few platforms support displaying these reports properly

Wish I could:
Buy/build a flat, multiband (fractal?) doppler antenna for stealth DFing
Build an automated APRS DF network
Try a Datong DF2 (favorite of DF guru W8VR, SK)

Doppler - "don't leave home without it" (but don't believe it standing still, and if you hook it to a transceiver you will fry it!)

Happy hunting!
 

AK9R

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Central Indiana
I've been thinking about buying a KN2C DDF2020T doppler. I know people who swear by it. Other than the price and the need for careful antenna installation and calibration, what are the pitfalls?

A few guys around here are also using the VK3YNG "sniffer" for fox hunting on foot. It seems like an easy way to home in on a fox without having to deal with attenuators.
 

vagrant

ker-muhj-uhn
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That VK3YNG sniffer is a pretty good tool. Two hunters I know use them and one let me try it out. With the auto adjustments and using a headset it does simplify things. Using one seems like the transmitter is pulling you toward itself due to the ease of use. Still, I learned more tricks of the trade, so to speak, by using whatever receivers along the way.

As the fox I have various Byonics items like their controller and several of their MicroFox transmitters. Over the years, this also helped me to appreciate the range 15mW of power can have depending on the antenna and terrain. Myself and others have been very creative after disassembling these micro transmitters and disguising them into something else for close-in on foot hunts. One guy would even bury one from time to time. A favorite spot is hanging one off a tree limb, or securing it to a branch. It takes people a while to look up.

There is another very small transmitter about the size of a half dollar. I don't recall the name/model now, or if it is still made, but the fox hid it one time under one of those plastic dog poop gag items.
 

N8RDF

(vanity call, "Radio Direction Finding")
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Brighton, MI
The DDF2020T (and I assume the MFJ-5005 twin) is very solid, you'll pay much more for anything potentially better. The pc software is ancient, not required and a little tough to hit the buttons when mobile but VERY helpul. I removed the top cover to just fit it in a standard 2-DIN dash mount along with the BCD996XT. In one car I replaced the factory stereo to put these in the dash for full-time use. I also hacked the cal pot so it would face out a small hole in the front panel for easier calibration (but re-cal is not an issue unless you change radios). Don't forget they also provide ready-to-go antenna mounts instead of the DIY necessary for cheaper units.
Regarding antenna setup, don't believe the hype about precise positioning. Sure, exact may be better, but I used dual-band duckies with 460mhz spacing for daily use and get great results on VHF and UHF, including non-ham stuff. Maybe for a formal hunt I'll adjust spacing for 2m, but I don't consider it critical. Maybe my DF style is more "seat of the pants" (turn here or don't turn here) than compass, map & bearing, but I've found ANY ham doppler to be very useful until you have to go on foot. Remember, real-world VHF/UHF hunting is like finding a flashlight in a house of mirrors. Having good clubs doesn't make you an expert golfer and doppler is the same. It takes some practice to know the quality of your readings. Don't wait for hunts to go out DFing (with any equipment).
The VK3YNG is also GREAT, but limited to 2m (and some old aero band) and I need a manual review before each use LOL. Nothings faster for 2m hunting on foot.
Regarding the Byonics PicCon Fox, I tried using a couple with HTs and couldn't keep the RF from messing them up (toroids, caps, DB9 RF isolators). The feature set is great, maybe just takes a little more finesse with the antenna setup.
 

N8RDF

(vanity call, "Radio Direction Finding")
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Forgot to mention another mod on the DDF 2020T. I like to hear the doppler tone, but not all the time. I used the scanner line out to feed the doppler but the level was a little less than the doppler needs. I hacked a small audio amp board from a Radio Shack battery powered external speaker into the doppler input. Now the scanner volume knob doesn’t affect the doppler. Not required but very useful.
 

dlwtrunked

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I am curious how many RR members have actually participated in a transmitter hunt and if so, how many. If you have had to do this in a professional capacity, please provide some details on the equipment you used.
I have done it many times. Although I have a Doppler unit, I prefer to use Arrow VHF/UHF DF loops with an SDR radio (with AGC turned off of course) and a good compass.
 

N8IAA

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Dec 19, 2002
Messages
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Fortunately, GA
Back in northern Ohio, we had a monthly club fox hunt. Whoever found the fox first, was the next fox. Used to a four element beam and a HT. Lots of fun. Also did it with a private group to find those who caused interference on our repeater.
 

vagrant

ker-muhj-uhn
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I have made and used a directional tape measure / PVC antenna for T-Hunts. While it worked, I prefer the Elk Log Periodic. I also tried the Arrow and found the difference between it and the Elk, side-by-side, is that the Arrow had a more narrow focus. To make up for that I just used more attenuation on the Elk, which was easy. Still, I prefer the Elk as I also use it for satellites and that wide beam width makes it easy to capture and hold satellites.
 

tweiss3

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Apr 24, 2020
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Ohio
I have not had the pleasure of participating in a foxhunt yet; however, I am gearing up for what is essentially a foxhunt. I'm trying to track down some 80m interference that is a mixture of the two AM radio stations that my house is between. I've narrowed down my equipment to a TinySA and a Airspy YouLoop magnetic loop antenna doubled up (two loops of the coax with the crossover connector taped to the "T"). I tried using a normal tranceiver (FT817 & D74a) but even in the null it was S6-S8 and very clear, but with the TinySA, I can see a solid difference in db (-92 in peak to -102 in null). I'll map direction at a dozen intersections and go from there to try and narrow it down.
 

PA8W

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Joined
Nov 14, 2017
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7
Many times...The annual BalloonFoxhunt in the Netherlands is a must here, and I often participated in local Foxhunts.
But you can have your own foxhunt event: Every day hundreds of weather balloons with radiosondes are launched worldwide.
In the past 10 or so years I recovered about 130 of them.
Great target practice!
Cheers,
Wil.
 

dickie541

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Apr 25, 2017
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3

Thought the participants in this thread would like this. I am a KerberosSDR user.

And, I've done one jammer finding exercise.
 

vagrant

ker-muhj-uhn
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@dickie541 Participate in more of them. Use different methods/gear as well. The combined experience will improve your skill. Also, many of the hunts I enjoy have an on foot hunt aspect for secondary and tertiary very low power transmitters, once the main transmitter is found by vehicle. Also, the Yagi transmitter mentioned in the video, those can be difficult to locate due to multi-path/reflection.
 

dlwtrunked

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A couple things people miss knowing of fox hunting
1. You need to practice the skill--it is a skill you can lose by forgetting things learned. Pick a signal you do not know where is (do not research it on the web) and try to locate it.
2. Learn compass/map skills (like "magnetic declination").
3. As vagrant said, use different methods/gear. Find something that works best for you. In my case, Arrow antenna VHF/UHF loop antennas designed for fox hunting and then used with an SDR with the AGC turn *off* (extremely important). (With a loop, go for the null, then do the arithmetic for the 90 degree difference and magnetic declination.)
4. Get high and clear when you go for a measurement on a not close station. You will be surprised at the difference this makes.
5. You need to practice the skillYou need to practice the skill (worth saying a second time).

With my loop and another ham with his beam, by going atop mountains and DF'ing, we nailed a location that was interfering with a repeater input although it was about 50 miles away.
 

joehawth

KB1RRG
Joined
Oct 31, 2008
Messages
99
Location
Morrisville, Vermont
One of our local ham clubs in Vermont has been holding (or trying to) a monthly fox hunt since last year. It is lots of fun. I found it first once and had the pleasure of getting to hide it the next time. It transmits a series of beeps and identifies in morse code on 2m. Depending on where it is, it hasnt been to hard to find, even without a directional antenna. I use a mobile rig and a 2m ht with a tape measure yagi.

The transmitter was built by KC1DPM out of spare parts.
more info including transmitter schematics:

 
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