[FoxHunt] antennas for harmonic sniffing

Kuon & Dale Hunt [email protected]
Thu, 29 Jan 2004 17:57:47 -0800


>... I find that the quad is a near
>perfect antenna for vertical polarized hunting in that the lobe width is
>  good in both planes. Long Yagi's are better than short ones. These
>little short Yagi's are near useless V-pol for anything other than 180
>degree homing. Most any thing has quite useable lobe width in the
>horizontal plane.
>

   I prefer the quad for mobile hunting, but because it doesn't
   stick up as far above the roof.

   How useful an antenna is also depends on how sensitive your
   signal strength indicator is:  I've known a number of folks
   who hunt with 2-element beams, even with vertical polarization.
   The VK3YNG 2m sniffer can easily detect a 0.2dB difference
   in signal strength using the audio S meter.  The 2m mobile
   rigs I have tested have around a 10dB range on their S meter
   with at least 7 steps, so can indicate differences less than
   2 dB.  If you eyeball average between the edges you can still
   get a reasonable bearing - certainly better than the 3dB
   beamwidth of the antenna.

   But that also explains why hunting the pattern null is
   popular (when it is predictable enough) because it is easy
   to get a 10dB variation over a small angular range.



>I have not done much harmonic hunting, but are the harmonics most always
>in the dame pol as the fundamental?

   Not necessarily... it depends on the antenna pattern on that freq.
   a quarter wave whip will act as a long wire on the higher harmonics,
   so it may radiate more upwards.  But in my measurements with
   vertical whips the yagi always gave better response with vertical
   polarization.  With a tilted or horizontal antenna this may not
   be the case, however, so I would recommend always checking both
   and choosing the one that gives the strongest signal.


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