Wally,
What you seem to be describing is a:
1/4 wave Inverted-L antenna for 80 meters.
1/8 wave Inverted-L antenna for 160 meters.
The radiation pattern should be both vertical and horizontal to produce a
dome over the antenna.
On 80 meters the impedance should be around 12 Ohms.
On 160 meters the impedance should be around 5 to 7 Ohms and very capacitive
or short.
You didn't mention what type of tuner you are using to couple into the
antenna. If it is the tuner built into the radio it will not be able to
match this antenna to 160 meters. Since the antenna is working for you on 80
meters leave well enough alone and enjoy it.
To get the antenna to play on 160 meters you will need to build another
tuning unit. The L network should do the job. I would place this unit
outside at the base of the antenna.
You will need something like a 50 uh coil and 1000 pf to 1200 pf worth of
capacitance. 1000 pf can be fixed with a 200 pf variable.
One end of the coil goes to the antenna element. The other end of the coil
goes to the coax center wire. At the tie point between the coax center wire
and coil attach one end of the capacitor. The other end of the capacitor to
the coax shield the radial system and ground rod if being used. Make a
jumper to short out windings on the coil.
With your MFJ-259 find the combination of inductance and capacitance for a
1:1 SWR . The bandwidth will be very small. The L-network will need to be
readjusted many times to go across the 160 meter band.
Good Luck, see you on Top Band.
Rich AA2MF
----- Original Message -----
From: "Wally Klinger" <wklinn@hotmail.com>
To: <TowerTalk@contesting.com>
Sent: Saturday, November 20, 2004 10:18 PM
Subject: [TowerTalk] 80 meter vertical
> Good Afternoon,
>
> I am in the process of reworking my 80 meter ground mounted vertical. It
> started out life as an HF2V. Last year I put a capacity hat on it and saw
> some improvement. This fall, I decided to rebuild it. I made it into a
33
> foot vertical, sans the coils and cap that are normally 3 or 4 feet above
> the base. I took a 33 foot piece of wire and attached it to the top of
the
> vertical. I ran the wire up to the top of my 70 foot tower on a 35-40
> degree angle about 50 feet east of the vertical. There is an insulator
and
> about 40 feet of rope separating the tip of this "bent vertical" from the
> top of the tower. The vertical is sitting on 55-60 radials from 33 to 135
> feet in length tacked below my sod.
>
> The antenna is not resonent as I hoped. I get an SWR of 1.1 at 3.7 Mhz,
but
> with my tuner I can flatten it out where I want it. I can not get it to
> load on 160 at all even with the tuner...... I get down to 8.0 to 1 on the
> 259 at the lowest point on 160.
>
> Has anyone ever done something like this before? A "bent" 66 foot
> vertical? Should it exhibit a low angle of radiation, or did I build a
> cloudwarmer? Any ideas on improving it? Theoretically, will it be
> directional or lobed in a particular direction? Any ideas on capacitive
or
> inductive loading at the base to gain a little 160 use? I simply strapped
> over the fiberglass insulator that formerly separated the coil. Heck, I
can
> even come up with a vacuum variable at this point.... What do I gain?
>
> Yup, it is still noisy, but I will take Phil's advice and mitigate this
with
> a K9AY loop that I am working on in the garage. That is tomorrow's
> project..... Ran outta daylight :)
>
> Any ideas you guys might have would be appreciated.
>
> 73--Wally Klinger W9BEA
>
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>
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_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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