[FoxHunt] antennas for harmonic sniffing

[WolfBob]

I got out EZNEC and came up with a 732.875 6 element wide spaced 
Yagi..18 inches plus handle. Tied it into my Yaesu VX-1R and got around 
12 dBi and 20 dB F/B. Rugged thing with a 1/2 inch dowel boom and 1/8 in 
brass welding rod elements (about 7 inches tip to tip). Tried it on a 
micro T (50 mW on 146.565) and got a range of about 50-75 ft. The radio 
doesn't squelch right on this frequency (I tried my second VX-1R and it 
too did the same thing). Another toy in the toybox...Thanx

Bob, WB6JPI


Steve wrote:
> I am interested, and some other CAP hunters too.
> Thanks,
> Steve
> 
> ----- Original Message ----- 
> From: "Kuon & Dale Hunt" <kuon@onlinemac.com>
> To: <foxhunt@mailman.qth.net>
> Sent: Sunday, January 25, 2004 12:16 PM
> Subject: [FoxHunt] antennas for harmonic sniffing
> 
> 
> 
>>With the "DC to daylight" coverage of the newer
>>hand-held receivers and transceivers, sniffing
>>transmitter harmonics for close-in work can
>>easily extend beyond the common 146 -> 438
>>combination.
>>
>>K7FM was interested in hunting ELTs, and sat
>>down with a calculator to determine the options.
>>It turns out that 730 MHz is a good choice:  it
>>is 6 * 121.5 (actually 729 MHz) and 5 * 146 MHz.
>>You can hunt both bands with the same antenna.
>>
>>This sounded promising so I scaled the W4RNL "OWA"
>>6-element yagi design to 730 MHz and built one
>>using PVC pipe and #8 aluminum wire.  The antenna
>>is less than 11" / 28cm long.  Set out my
>>ELT practice beacon and it works great!  Using
>>the frequency knob as an attenuator (the ELT has
>>a VERY WIDE signal - only 40dB down at 100kHz off,
>>which is why the old 121.6 MHz practice frequency
>>could be heard on the emergency channel) I could
>>get clear bearings at 3' / 1m away.  The pattern
>>is very clean, with just one peak above the noise.
>>I could hear the beacon at 250 m / yards away, and
>>could probably stretch it to a quarter mile ( 400m )
>>line of sight.  (Maximum distance was about 100m
>>when the signal passed through a building.)
>>
>>Haven't tried it on 2m yet:  although odd harmonics are
>>generally stronger than even ones, most 2m rigs should
>>have much lower harmonic output than the ELT...
>>
>>...OK, I'm back.  The rain stopped and the temperature
>>warmed up to 36F / 3C so I set out one of my 2m
>>transmitters:  a Hamtronics synthesized kit at about
>>1 watt output.  I could copy the signal on 732.825 MHz
>>from 400m away.  Probably could go further, but the road
>>went over a hill at that point.
>>
>>Receiver in both cases was a VR-500.  The minimum
>>discernable signal is at least 6dB better using CW
>>than AM or FM.
>>
>>If there is interest maybe I can post the dimensions
>>and a photo somewhere.
>>
>>     - Dale WB6BYU
>>
>>
>>---
>>[This E-mail Scanned for viruses by Onlinemac.com]
>>
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