[50mhz] antenna 2m/6m vertical

Thu Aug 18 21:10:58 EDT 2005

Hi Al,

According to Roy Lewallen's EZNEC 4.0 a horizontal dipole 
antenna 20 feet off the ground 7.6 dBi gain with 15 degree take 
off angel and another lobe at 45 degrees and 6.73 dBi gain in 
the direction of maximum radiation and -7dBI at 15 degrees and 
2.4 dBi degrees at 50 degrees elevation.

Compare that to 3.43 dDi out at 10 degrees -4.81 dBi at 50 
degrees for vertical dipole at 20 feet and 4.81 dBi out at 5 
degrees and -1.7 dBi out at 30 degrees for 1/4 ground wave at 20 
feet.

While modeling a 6 meter dipole things get interesting with  45 
degree 9 foot 2 inch center fed dipole canted at 45 degree angle 
with the low end 20 feet off the ground. It gives 5.8 dBI at 10 
degrees and 3.41 dBi at 40 degrees. Dropping the low end to 5 
feet gives reasonably good high angle radiation up to 4.12 dBi 
at 30 degrees and 1.5 dBi at 30 degrees over 180 degrees. Not 
great but much better then a vertical for E layer propagation 
and very easy to do.

I stumbled on the vertical dipole at 45 degrees one new years 
eve in a 2 meter opening when with 20 watts FM on two meters 
from Stillwater, OK I worked the far end of the Panhandle to 
Broken Bow in the far south east, Kansas City, Mo, Little Rock, 
AK, Dallas Texas and a lot inside that circle.

The next day I saw the 6 meter vertical dipole that had a 2 
meter parasitically fed 2 meter dipole made of #9 wire about 1 
inch from  the 6 meter dipole using only capacitive and 
inductive no physical connection to the six meter dipole that 
the low end was 7 foot off the ground. That got me started 
running models of canted antennas. I have not modeled a 1/4 
ground plane because rotating it is a pain but the pattern and 
gain over a vertical should be the similar.

A 6 meter dipole can be tuned to have less than 2 to 1 SWR over 
the range of SSB and FM operation and less than 1 to 3 over from 
50 MHz to the FM usage area. If my rig would handle it I would 
not use a tuner for that. The loss in the tuner is added to  the 
loss in the coax and modern rigs will handle 3 to 1 SWR fine. 
Tuners are OK if the rig reduces power but if the rig is happy 
and cool leave it alone.

SWR matters for  video, weak signal or high speed digital were 
the reflected wave can interferes with the signal. For these the 
match needs to be made at the antenna not the rig.

Gordon W5RED

Schichler, Alfred wrote:
 > Are you guys mostly talking about 6 meter FM, or will those 
vertical
 > antennas work for ssb? I think I heard that most of those 
sigs are
 > horizontally polarized, but I'm not sure. I'm very new to 6.
 >
 > I've been using a G5RV (with a tuner) to listen on 6 meters, 
but I haven't
 > heard much so far. Just an FM repeater around 53.3 MHz. The 
G5RV seems to
 > pull in more than the Butternut HF-6V (with a tuner), and the 
2 meter Ringo
 > Ranger doesn't pull in much at all, but then, it's not very high.
 >
 > Al
 > WA2AS
 >
 > -----Original Message-----
 > From: Chris Boone [mailto:CBoone at earthlink.net]
 > Sent: Wednesday, August 17, 2005 8:24 PM
 > To: '6 Metros Lista D.'
 > Subject: RE: [50mhz] antenna 2m/6m vertical
 >
 >
 > Using a 5/8wave series fed antenna on 2mts as a 6mtr antenna 
makes
 > sense...but going the other way is not a good idea..
 > A 6m whip is 3/4 wave on 2mts, not properly phased and thus 
has a poor angle
 > of radiation and less gain than a regular 1/4 vertical ...the 
5/8w on 2mts
 > acts as a base loaded quarter wave on 6 and works as well as 
a full 1.4wl
 > antenna....Ive been running Larsen NMO150s on six for over 25 
years...(in
 > fact have one on my company van and my Blazer :)
 >
 > Chris
 > WB5ITT
 >
 >
 >>-----Original Message-----
 >>From: 50mhz-bounces at mailman.qth.net
 >>[mailto:50mhz-bounces at mailman.qth.net] On Behalf Of Chris
 >>Williams W6NOB
 >>Sent: Wednesday, August 17, 2005 7:09 PM
 >>To: Jose Manuel EA8EE; 6 Metros Lista D.
 >>Subject: Re: [50mhz] antenna 2m/6m vertical
 >>
 >>Jose,
 >>
 >>Yes, there are a number of dual-band and multi-band antennas
 >>on the market that will work on both 50 MHz & 144 MHz. Also,
 >>there are many stations that have found that a 2 meter 5/8
 >>wavelength whip will act as a "loaded" 1/4 wave whip on 6
 >>meters. A friend of mine has been using a Larsen NMO-150 2
 >>meter 5/8 mobile whip on both 6 & 2 meters for several years
 >>now and is very happy with it. Many years ago another old
 >>friend  used a 6 meter 1/4 wave groundplane on both bands. He
 >>explained that the antenna acted as a 3/4 wavelength
 >>groundplane on 2 meters. Other commercially available
 >>antennas designed to operate on both bands can be found on
 >>the WWW from Comet, Diamond and various others.
 >>
 >>I hope this help's.
 >>
 >>73 de Chris W6NOB
 >
 >
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