All,

I have been using an 80 meter loaded vertical for a couple of years with
moderate success. The ground system is a dozen 'untuned' radials 40 or so feet
laying on the ground. The feed line is about 100 feet of RG-8 coax. The SWR in
the shack is about 1.1 to 1.

I have done some research on the antenna and based on it parameters it should
have a radiation resistance of about 4 Ohms. This says that the coil and ground
are absorbing on the order of 45 Ohms. This is 10db performance loss.

I have limited space and the most common solutions are not available to me. From
a practical perspective it would seem to me that building a 40 foot center feed
loaded dipole and putting it in the attic or on the roof would probably perform
somewhat better.

Is this a reasonable assumption?

Would burying the radials and connecting them to several 4 square foot buried
screens substantially help the ground system?

Thanks,
Dan kb0qil

Put a capacity hat on the top of the antenna. This will give you the most
performance increase with the least effort.


"dansawyeror" wrote in message
...
All,

I have been using an 80 meter loaded vertical for a couple of years with
moderate success. The ground system is a dozen 'untuned' radials 40 or so
feet

Burying the radials will make zero difference in performance.

"dansawyeror" wrote in message
...
All,

I have been using an 80 meter loaded vertical for a couple of years with
moderate success. The ground system is a dozen 'untuned' radials 40 or so
feet laying on the ground. The feed line is about 100 feet of RG-8 coax.
The SWR in the shack is about 1.1 to 1.
[stuff]

Would burying the radials and connecting them to several 4 square foot
buried screens substantially help the ground system?

Thanks,
Dan kb0qil

I have been using an 80 meter loaded vertical for a couple of years with
moderate success. The ground system is a dozen 'untuned' radials 40 or so
feet laying on the ground. The feed line is about 100 feet of RG-8 coax.
The SWR in the shack is about 1.1 to 1.

I have done some research on the antenna and based on it parameters it
should have a radiation resistance of about 4 Ohms. This says that the
coil and ground are absorbing on the order of 45 Ohms. This is 10db
performance loss.

I have limited space and the most common solutions are not available to
me. From a practical perspective it would seem to me that building a 40
foot center feed loaded dipole and putting it in the attic or on the roof
would probably perform somewhat better.

Is this a reasonable assumption?

Would burying the radials and connecting them to several 4 square foot
buried screens substantially help the ground system?

Thanks,
Dan kb0qil

How high is the antenna, where is the loading coil placed, what is its
value, and Q?

Frank

I have limited space and the most common solutions are not available to
me. From
a practical perspective it would seem to me that building a 40 foot
center feed
loaded dipole and putting it in the attic or on the roof would probably
perform
somewhat better. ..............

Probably so for short/med haul. Will be a toss for long haul.
Even a semi lossy vertical can outdo a low dipole to dx if the
path is long enough. But for talking 200 miles away, the dipole
will blow the vertical away.
12 radials is not many for a ground mount. If you were to add
more radials or screen, I'd do it at the base of the antenna.
IE: add 50 10 ft radials for 500 ft of wire... Should be better
than a few full size radials. Some say screen can cause problems
after a while do to corrosion. I'd probably just stick with wire
radials myself... How far you want to talk on that band should
determine what antenna is best. For most general use within
1000 miles, I'd rather be on a dipole than a vertical.
But dx, I'd go vertical, and improve it. Loaded does not have
to mean crippled. But loading/short verticals do make the ground
system more critical. My mobile is better than my home dipole
late at night on 40m if I'm talking over 1000 miles away...
And if it ain't loaded, I dunno what is...What power it radiates
is at the perfect fairly low angle for that path/time of night.
BTW, I'd install the dipole outside if at all possible. Less noise
from the house, and will generally work better. Won't hurt it to
be close to the roof, unless metal is underneath to detune.
I've layed dipoles directly on composition shingles with no
problems at all. Or at least when dry anyway... But elevated a
bit would be better.
MK

Hello Dan,

Some thoughts:

The 10 dB loss is, of course, referenced to a "perfect ground." Even
with a full length (quarter-wave) vertical and your ground system,
performance would improve by about 3 dB. Not a blockbuster.

Improving the radial system, as noted by others, is a more realistic
course. You ought to be able to get the ground resistance closer to 20
ohms with more radials close in. Then you will be only 6 dB worse than
if your ground were perfect.

Putting up an indoor dipole is cheap and quick. Put it up and compare it
with the vertical. But don't hold your breath. You will probably find
that with some paths, the dipole is better. you may want to keep both.

I assume you've ruled out a capacity hat, center loading, and a coil
with lower losses, as suggested by others. But with these changes and an
improved ground system, you might get a full (6 dB) S-unit improvement.

Good luck.

73,

Chuck





dansawyeror wrote:
All,

I have been using an 80 meter loaded vertical for a couple of years with
moderate success. The ground system is a dozen 'untuned' radials 40 or
so feet laying on the ground. The feed line is about 100 feet of RG-8
coax. The SWR in the shack is about 1.1 to 1.

I have done some research on the antenna and based on it parameters it
should have a radiation resistance of about 4 Ohms. This says that the
coil and ground are absorbing on the order of 45 Ohms. This is 10db
performance loss.

I have limited space and the most common solutions are not available to
me. From a practical perspective it would seem to me that building a 40
foot center feed loaded dipole and putting it in the attic or on the
roof would probably perform somewhat better.

Is this a reasonable assumption?

Would burying the radials and connecting them to several 4 square foot
buried screens substantially help the ground system?

Thanks,
Dan kb0qil

MK,

Thank you for your reply. I will defiantly try adding radials. It may be easier
to lay down screen mesh then 50 10 foot radials.

Have you measured the impedance of your mobile vertical? Is it a simple loaded
vertical or is there a matching network?

Thanks,
Dan kb0qil

wrote:
I have limited space and the most common solutions are not available to
me. From
a practical perspective it would seem to me that building a 40 foot
center feed
loaded dipole and putting it in the attic or on the roof would probably
perform
somewhat better. ..............

Probably so for short/med haul. Will be a toss for long haul.
Even a semi lossy vertical can outdo a low dipole to dx if the
path is long enough. But for talking 200 miles away, the dipole
will blow the vertical away.
12 radials is not many for a ground mount. If you were to add
more radials or screen, I'd do it at the base of the antenna.
IE: add 50 10 ft radials for 500 ft of wire... Should be better
than a few full size radials. Some say screen can cause problems
after a while do to corrosion. I'd probably just stick with wire
radials myself... How far you want to talk on that band should
determine what antenna is best. For most general use within
1000 miles, I'd rather be on a dipole than a vertical.
But dx, I'd go vertical, and improve it. Loaded does not have
to mean crippled. But loading/short verticals do make the ground
system more critical. My mobile is better than my home dipole
late at night on 40m if I'm talking over 1000 miles away...
And if it ain't loaded, I dunno what is...What power it radiates
is at the perfect fairly low angle for that path/time of night.
BTW, I'd install the dipole outside if at all possible. Less noise
from the house, and will generally work better. Won't hurt it to
be close to the roof, unless metal is underneath to detune.
I've layed dipoles directly on composition shingles with no
problems at all. Or at least when dry anyway... But elevated a
bit would be better.
MK

dansawyeror wrote:
I will defiantly try adding radials.

Who are you defying?

----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----

On Sat, 20 Aug 2005 13:34:36 -0500, Cecil Moore wrote:
dansawyeror wrote:
I will defiantly try adding radials.

Who are you defying?

Lawn gnomes, probably.

Frank,

The coil measures about 60 uH. The antenna is elevated about 3 feet on a short
tripod. The radials angle down the tripod legs and then out.

The coil is about 4 inchs in diameter, number 12, wound on a fiberglass form. It
is centerloaded. I am looking at it accross the yard, it is about 6 inches long.
It is would with about a point .5 pitch. Calculations for a 1:1 pitch predict a
Q of about 450.

Thanks,
Dan

Frank wrote:
I have been using an 80 meter loaded vertical for a couple of years with
moderate success. The ground system is a dozen 'untuned' radials 40 or so
feet laying on the ground. The feed line is about 100 feet of RG-8 coax.
The SWR in the shack is about 1.1 to 1.

I have done some research on the antenna and based on it parameters it
should have a radiation resistance of about 4 Ohms. This says that the
coil and ground are absorbing on the order of 45 Ohms. This is 10db
performance loss.

I have limited space and the most common solutions are not available to
me. From a practical perspective it would seem to me that building a 40
foot center feed loaded dipole and putting it in the attic or on the roof
would probably perform somewhat better.

Is this a reasonable assumption?

Would burying the radials and connecting them to several 4 square foot
buried screens substantially help the ground system?

Thanks,
Dan kb0qil


How high is the antenna, where is the loading coil placed, what is its
value, and Q?

Frank