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Reviews For: Dick Smith Radio Direction Finder

Category: Direction Finding equipment

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Review Summary For : Dick Smith Radio Direction Finder
Reviews: 1MSRP:
Description:
"Roanoke"-type "Doppler" Direction Finding unit
Product is in production
More Info: http://
# last 180 days Avg. Rating last 180 days Total reviews Avg. overall rating
0013
KA7OEI Rating: 2006-01-13
Works fine - *IF* you modify it first! Time Owned: more than 12 months.
This unit appeared in the Mid-80's (an article appeared in the July 1986 issue of 73 magazine) and was sold as a kit in the U.S. by Dick Smith Electronics during the (brief) time that it was present in the U.S. These units were (briefly) popular and they occasionally appear for sale at swapmeets, etc. Its model number was either "K-6345" or "K-8345" (I have printed material showing it both ways, but it seems to describe exactly the same unit.)

Unfortunately, as originally designed, it is nearly unusable in all but the most multipath-free locations - not the usual environment found in or around any city.

Fortunately, the modifications aren't too difficult: K0OV spells out the necessary modifications on the "Homing In" web site (a google search will locate this quickly.) These modifications involve modification of the audio filter as well as the antenna switching unit and are fairly easy to do.

An optional modification not mentioned in the above article has to do with replacing the free-running 1 MHz R/C oscillator (using IC2) with a crystal-based one, either using a "Crystal Can" oscillator or rewiring IC2 using a 1 MHz crystal. While not absolutely necessary, a stable reference is nice to have if you are having trouble with the 1 MHz oscillator's harmonic(s) "sweep" past the frequencies on which you are listening: With a crystal-based oscillator, one can tune if off frequency - and expect it to stay there. (Not normally a problem, however...)

Once the above modifications are done, it seems to work as well as any other Radio Direction finding unit based on the original "Roanoke" design, such as the Ramsey DF-1 or the similar kits available from FAR circuits.

This unit, like some others, use the now-obsolete MF-5 switched capacitor filter. While the one that I have still works fine, it is worth mentioning that an MF-10 is really two MF-5's in one package and an MF-10 (or the newer, better LMF-100) can replace it if one wires up a small "daughter" board to accomodate the wiring difference.

As with any direction finding equipment, it should be expected that multipath (such as that found amongst buildings or hills/mountains) will tend to scramble readings that you get. As with any skill, the operator can quickly learn to recognize these sorts of situations and know which readings to believe - and which ones you should not. While more complex computer-based units can better-recognize and help filter out some of the more "bogus" readings, none are immune and experience is, by far, the best tool in your arsenal!

Performance-wise, this unit gets a 4, but because it had to be modified to do so, it gets a 3...