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Thank you Richard Cook W2RAC 06.20.2008
Transmitter hunting links
TAPE MEASURE BEAM
OPTIMIZED FOR RADIO DIRECTION FINDING
http://home.att.net/~jleggio/projects/rdf/tape_bm.htm
RADIO DIRECTION FINDING PROJECTS
http://home.att.net/~jleggio/projects/rdf/rdf.htm
555 Time-Difference-Of-Arrival RDF
http://home.att.net/~jleggio/projects/rdf/tdoa2.htm
SIMPLE ADJUSTABLE PASSIVE
ATTENUATOR
http://home.att.net/~jleggio/projects/rdf/a_atten.htm
Build An Offset Attenuator
http://www.homingin.com/joek0ov/offatten.html
http://www.users.bigpond.net.au/vk3yng/foxhunt/foxhunt.html
http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=2767
http://utaharc.org/rptr/ark_df_desc.html
http://www.ramseyelectronics.com/cgi-bin/commerce.exe?preadd=action&key=DDF1
Book
TRANSMITTER HUNTING
Radio Direction Finding Simplified
By Joseph D. Moell, KØOV,
and Thomas N. Curlee, WB6UZZ
7 X 9 inches, 323 pages, 235 illustrations
Publication #2701 from TAB Books, division of McGraw-Hill
First edition, 13th printing - - ISBN number 0-8306-2701-4
http://www.homingin.com/THRDFSinfo.html
Thank You Bill Schwartz WS1C
06.22.2008
Multi-Path Problems If you think you are having multi-path problems or reflections. Ignore your Doppler readings and switch to your hand held directional quad or yagi antenna. Same thing goes if you don't hear the signal on one system, switch systems or receivers you could have just "barfed" one or have a broken coaxial cable. 11.21.2006
Tape Measure Beam Builder Tip Want to make nicely rounded ends on your tape measure beam? Sure you do no one wants to have ugly sharp ends on the elements. Try this little trick. Pick yourself up a pair of Venetian blind trimming scissors. They have a nice rounded ends on them and in about six cuts on a scrap and you will have mastered the proper method of aligning them to get really nice rounded corners and square looking ends. The last time I saw them was in the Venetian blind department at a Lowe's or Home Depot and they are relatively inexpensive to purchase. Bob. WA4IDI [Posted on 04.17.2005]
ACTIVE ATTENUATORS
I have had several inquiries about using the active attenuators that hunters have built. Some have had problems getting them to attenuate moderate to strong signals when the hunters close in.
Until recently, I have preferred the 2 MEG OSC because it was easy to get completely out of the ham bad for the receiver. Now I am looking more at the 1 MEG OSC. Of course those with radios that do not RECEIVE outside the band would have a problem with the 2 or even 4 MEG OSC but on the good side they would be prevented from an accidental transmission into the attenuator.
To use the active attenuator some trial and error is needed to determine the best offset to use with your radio. First, try the offset that you OSC runs on. Example, using a 2 MEG OSC and a 146 MEG signal try the receiver and OSC at 148 (+2 MEG) and if this completely nulls a reasonably strong signal then use that step. However, for some odd reasons some receivers and attenuator combinations prefer the second step (third harmonic of the OSC) so using the above example looking at the 146 MHZ signal jump twice the OSC frequency and try the receiver at 150 MHZ. NOTE THAT THESE FREQUENCIES ARE NOT ALWAYS THE BEST TO USE. THE OSC IS AN EVEN VALUE AND MAY CAUSE POOR PERFORMANCE WHEN THE FREQUENCIES ARE VALUES THAT ARE EXACT MULTIPLES OF THE OSC FREQUENCY. If you are not satisfied with the results try changing the frequencies from an exact multiple of the OSC and try again. For example, try the frequency at 200 or 300 above or below the OSC frequency. We seldom (if ever) use 146.000 or other even frequencies in our hunts so this is not a problem.
Another trick is to try receive frequencies above AND BELOW the target frequency. Some setups work better one way or the other.
Another nice feature of the active attenuator is that it will work very well on the 70 cm band. So with your dual band HT, an antenna and the active attenuator you can hunt the 70 cm band.
If this sounds complicated (it really is not) remember that it is a trial and error method to find the BEST combination for your setup.
If you have problems I will be glad to meet with you and help. I have OSC IC's at 1, 2, 4 MHZ and we can test your setup to find the best. When working properly these attenuators will kill 50 watts at 10--20 feet. [Editors note: If you find a better method from your efforts by all means share it with us.] John Munsey, KB3GK
Posted on 04.12.2005
Recently, I have been asked about our hunting style, in particular our technique in Orlando.
First, in general:
NEVER take direction headings while standing still or even moving in a very small area, for example 3 or 4 feet. You may be reading the direct signal but odds are 90% that you will be reading a reflection or multi-path signal.
ALWAYS look for direction and pay little attention to signal strength. The hider may be using a beam or be hidden in a low spot where signal strength will vary. Always look for direction.
IN ORLANDO the signal was weak... very weak. We drove west on RT 50 and noticed that there was a very small change in the background noise pointing to the S/W. As we drove west this "signal" moved to our lest, south, so we turned and retraced our route and observed the same faint noise reduction in the same directions. Of course this could have been anything. RF from other sources but we took a chance (the only chance for that matter) and followed the faint signal. After several minutes we would sometimes hear part of an ID and we knew we were going in the correct direction.
When you can't hear the signal, drive towards any noise reduction you can observe.
ANTENNA.. Vertical or Horizontal?
As soon as you acquire a reasonable signal turn the antenna to horizontal! It doesn't matter if the signal is vertical or horizontal The antenna in the horizontal plane will give you about 15--20% sharper headings. This is especially true in wooded areas or areas with a lot of reflections.
MOBILE: Sniffers are designed for a very fast rise and fall response. For that reason they are not, usually, good for mobile use. An older receiver with slow acting S-METER readings is the best. One reasonable exception to this rule is the Ron Graham 2 meter receiver. It has a nice response time that "can" be use mobile. Most hunters use QUADS for mobile work because, they claim, rightfully, that the Yagi adds height that is a problem... Just try it Horizontal and end that problem. It is then lower than any other antenna.
DUAL BAND ANTENNAS: OK, if you need them but better results will be obtained it you remove unneeded elements.
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