On Sat, 3 Jan 2004 11:29:29 -0700, "Ken Bessler"
wrote:

I live on the 3rd floor of an apartment building. I just got permission
to put up a vertical antenna on the roof with 1 restriction - the antenna
can't be more than 10 feet tall.

I can put radials on the roof. Another problem (maybe) - I can't have
a key to access the roof so once the antenna is up, it needs to be a
"set it and forget it" type. Cost is an issue.

Also, the building is VERY passive to RF - I get good performance
with a 10 meter mag mount on the inside of my A/C wall unit. I also
have a 2m/440 mag mount there and it works well. I also have a
GPS unit (Garmin Vista) which works quite well indoors, despite
it's patch antenna (low gain). For low banding I have a 153'2" dipole
wrapped around the building. It's a good performer on 20 and
lower but performance falls off above 15 megs. On 10 m, my mag
mount antenna indoors performs better.

I'll be running a Yaesu FT-817 with a homebrew 40w amp and a
LDG Z100 tuner. My main requirements as far as operating bands
are 20 meters. I'd like to get 17m too if I could.

I'm thinking a Hustler 20m mobile antenna with a long base rod. I
considered a screwdriver antenna but cost & maintenance rules
that out.

Here's my parts list:

Hustler RM-20S 20 meter super resonator $28.99
Hustler MO-3 54" rigid base mast $23.99
Hustler RVM Mount $20.99
--------
Total $73.97

Any ideas?

73's de Ken KG0WX


Hi Ken,

Research the experience of Mobile HF designs. You will need to invest
in the equivalent metal presented by a car (reasonably done through a
ground mat of similar foot print) to act as the ground/reference which
allows these antennas to work.

It has been long established that a resonating coil about 8 feet up
this permitted 10 feet, with a large top hat built out at the top
would be the most efficient. This is the optimal solution to the
restrictions you have been placed in.

As for your wrap around antenna; you show a clever intuition, and you
may wish to use this 10 foot allowance to build it out, at that height
instead of snug against the building. My hunch is that it won't make
much difference (don't take down the original), but it gives you room
to experiment if the building super will allow you 3 or 4 points
elevated that same 10 feet. A smaller loop may aid in those bands
that are just not performing. If you can get away with 2 points, you
can look to top loaded verticals that go beyond the top hat (in other
words, a top hat that requires extensive mechanical support).

73's
Richard Clark, KB7QHC