[TowerTalk] Improving my dipole

[Buck - N4PGW]

> -----Original Message-----
> From: towertalk-bounces at contesting.com [mailto:towertalk-
> 
> One thing that I've never seen mentioned anywhere is a multiple-band
> dipole fed with ladder line. The reason I'm curious about it is that I
> used to have an 80-Meter Inverted Vee fed with ladder line, and the
> performance was great on 80M. For 160M contests, etc. I would add about 65
> feet to each leg so that it became a full-sized Inverted Vee for 160.
> However, in doing that, even though the tuner matched it just fine on 80M,
> my great 80-Meter performance went away until I removed the 160M
> extensions. I always wondered if I could have had both, if I had built up
> a combination 160 and 80M Inverted vee with both sets of elements off of
> the same ladder line feeder, like may people do with coax-fed multiple
> dipoles. Anyone ever try something like this?
> 
> LJ

If you are running several hundred feet, maybe you could save some loss, but
if you are running RG-8U on 160 and 80 meters, I think the loss is
negligible on 100 feet to a matched antenna.  You might need to trim the
band edges with a tuner, but I don't think the losses in the coax are
serious for a minor trim.  However, if you are planning to use the inverted
vee antenna to tune other bands as well with a tuner, you might well need
that ladder line.  

I have used the multi-band parallel element dipoles for 28 years on coax.
They have always worked very well.  Also, when you run the multi-band wires,
the bandwidth of the antennas is increased.  My 20 meter mono-band dipole
was cut for 14.336, the spot for the lowest dip on the SWR meter. It was
running 2:1 in the extra portion of the CW band.  When I added a 6 meter
dipole hung 8 inches below it, the minimum dip frequency dropped to <1.3:1
from 14.000 to 14.252.  From there it goes up to 1.3:1 at 14.350. (Using the
internal SWR meter in the Ic-706 which is a bar graph registering only 1.3,
1.5 + SWR steps.)

I have never had a 160 meter antenna.  I don't know how wide the bandwidth
of that antenna will be, but on 75/80, I have always had a bandwidth that
allowed me to operate from at least 3.975 through the general class CW
portion of the band with less than 2:1 swr.  (I don't have one up right now
so I can't be more specific.)  I suspect you won't need a tuner if you make
your multi-band Inverted Vee for 160/80 and feed it with coax.  

Good luck.

Buck
N4PGW