[GreenKeys] Fwd: OT -- sneak peek -- oops, forgot the pics

[Ralph Irish]

Forgot to add the Greenkeys group to this message earlier:



> From: Ralph Irish <w8roi at wowway.com>
> Date: May 18, 2017 8:17:55 AM EDT
> To: Jim Haynes <jhhaynes at earthlink.net>
> Subject: Re: [GreenKeys] OT -- sneak peek -- oops, forgot the pics
> 
> And, for those appliance operators out there we have the National RF Inc direction
> finding system.  Hook it to a simple HT and go hunting.  The photo in the link
> shows the device in its 'resting' or storage position.  
> 
> 	http://www.nationalrf.com/vector-finder-145.htm
> 
> When in the operating position the four adjustable antennas are extended as needed,
> and the 'wings' fold flat to put the two 'dipole' assemblies a little over 17" apart.
> 
> There is a compass on the top that will give you reasonable 'bearings' on the signal
> and a few such bearings on a map will put you very close to the source of the RF.
> 
> I have a VF 142.  The one in the photo looks identical but has a new Model number,
> VF-145.  Probably a few refinements since I bought mine around 15 years back.
> 
> There are "LEFT" and "RIGHT LEDs that help you to zero in on the signal.  I've never
> won a 'Fox Hunt' but I've certainly located the "Fox" a time or two.  There is also
> a small speaker inside, and a volume control.  The "TONE" mentioned below occurs in
> the speaker when you are just a bit off.  It goes to a very low level, theoretically
> to zero, when you are 'right on' the bearing.
> 
> The "DOPPLER" device described below sounds a lot like my VF-142.  All of the Doppler
> units I've seen have an 'array' of antennas, similar to the photo put up by Gil.
> 
> National RF Devices has a wide array of products which show at:
> 
> 	http://www.nationalrf.com/products.htm
> 
> Ralph - W8ROI
> 
> - - - - - - - -
> 
> 
> On May 17, 2017, at 10:34 PM, Jim Haynes wrote:
> 
>> Some guys here made a Doppler direction finder for hidden transmitter
>> hunting.  Consists of a pair of 2-meter dipoles spaced a foot or two
>> apart, and in the middle is a tiny little circuit that switches between
>> them to a cable that goes to a handheld transceiver.  When both antennas
>> are broadside to the signal source you hear nothing, but when they
>> are at different distances from the source you hear a tone.  I haven't
>> got my head around how this works, but the transceiver is FM, so if you
>> hear a tone I guess it's because there is a difference in apparent
>> frequency between the signal from the two antennas.
>> 
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