Jim,
Some years ago, I worked with another ham to feed his two HF2Vs in-phase
(broadside) -- the biggest problem was getting the two antennas to have
identical feedpoint impedance. It took plenty of tweaking; each antenna
seemed to have a different shift between independent and mutual coupled
settings.
Once we got the two matched, the pair worked well on 40M (primary band of
interest).
Around that same time I had two 40M ground planes -- full-size verticals fed
30 feet up, with (3) radials that doubled as guys. Spacing was about 160
degrees, and they were very "tame" when it came to phasing.
73, Gary
K9AY
> At 06:25 AM 2007-02-12, Jim Miller KG0KP wrote:
>>I have two Butternut vertical antennas (HF6V and HF9V) now that I
>>have rebuilt the parts one I acquired. I would like to consider
>>phasing them and expect it would work for "any" particular band but
>>wonder what the effect would be on the other bands. Would other
>>bands be degraded or could both antennas be driven with the proper
>>phasing (by band) and be effective? What physical separation
>>distance would be recommended? Same physical distance must serve all
>>bands.
>>
>>I expect this could be modeled separately as monoband verticals but
>>I am new at modeling and do not know how to model phasing.
>
> I'm not too familiar with the specifics of these antennas, but as
> long as they are fairly close to the same size (in wavelengths) and
> similar feedpoint impedance on each band, you shouldn't have too much
> trouble phasing them.
>
> You can obtain either of two bidirectional patterns (90 degrees
> apart) on the band where the antennas are 1/2 wl apart. You can get
> cardioid (unidirectional, endfire)) patterns on the band where they
> are 1/4 wl apart. It is possible to get endfire patterns on a band
> where they are 1/8 wl apart, but the feed impedances can get really
> low due to the mutual coupling and make it hard to get good
> efficiency (unless you like laying lots of radials).
>
> On higher bands where the spacing is 3/4 wl or more, there will be
> several lobes, regardless of the phasing. However, you can steer the
> lobes (and nulls) by adjusting the phasing.
>
> Modeling phasing is easy. Just put a current "source" at the base of
> each antenna and adjust the phasing to get the pattern you
> like. (EZNEC comes with a sample 2-element phased array with 1/4 wl
> spacing and 90 degree phasing in a file called CARDIOID.EZ , plus a
> similar one with a transmission line feed network called CARDTL.EZ).
>
> Getting equal currents and the desired phase in the real world is a
> heck of lot harder than modeling them!
>
> 73, Terry N6RY
>
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