"VK3XL" wrote in message
...

Hi all, I am currently building a new 2 meter beam for SSB. I am using
the DL6WU design on a 6 meter boom. While working on the antenna last
night a thought struck me "why not interlace a 70 cm beam on the same
boom"?
so here is the question, does any one have any data on interaced beams
in particular the degredation of performance of the equivelent monoband
yagis.
There are a number of reasons that this interlaced beam idea is
appealing to me (mostly mechanical) but I am not sure how badly the
gain may be effected. Does anyone have real data on the issue?
many thanks
Mike
VK3XL

Some help: I saw one for sale at HRO a few years ago. Might have been this
one:

http://www.eham.net/reviews/detail/3297

Note also that many VHF TV antennas are this way; the low-band elements for
55 - 88 MHz share the boom with the high band elements for 172 - 216 MHz.

These two bands are approximately in a 1 : 3 ratio, as are 2M & 70cm.

Thanks for the reply. All very interesting, but I am thinking of something a bit bigger ie 12 elements on 2 meters on a 6 meter long boom and up to 27 elements on 70 cm on the same boom. I fear that because 70 cm is almost exactly the 3 rd harmonic of 2 that the 2meter elements will act as unwanted directors in the 70 cm beam, any thoughts welcome.....
Mike
VK3XL

"VK3XL" wrote:
Thanks for the reply. All very interesting, but I am thinking of
something a bit bigger ie 12 elements on 2 meters on a 6 meter long
boom and up to 27 elements on 70 cm on the same boom. I fear that
because 70 cm is almost exactly the 3 rd harmonic of 2 that the 2meter
elements will act as unwanted directors in the 70 cm beam, any thoughts
welcome.....

One method of solving that problem is to orient the 2m elements
at right angles to the 70cm elements. Of course, if you don't
rotate the antenna by 90 degrees between bands, you would
lose 3 dB on both bands (assuming you want horizontal
polarization on both bands).
--
73, Cecil http://www.qsl.net/w5dxp