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

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

Ken Bessler wrote:
Any ideas?

Put a large enough top hat on a ten foot aluminum pole
to cause the system to resonate on 20m. No coil required.
--
73, Cecil http://www.qsl.net/w5dxp



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Another option. I use a 17 meter hamstick and a remote auto tune Tuner,
ICOM AH-4, in my mobile and cover 6 through 40 meters with it. Forty
meters is down about 1 S unit from a 40 meter Hamstick but it works.

So, solution would be to use a mobile antenna, eg Hamstick; a remote
tuner, AH-4 or equivalent; and a counterpoise.

If you need everything from scratch it should cost about $250 [mostly
for the AH-4]. If the LDGZ100 is remotable then you have a $50 solution.

Deacon Dave, W1MCE

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.
SNIP

"Richard Clark" wrote in message
...

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

After thinking a bit I'm leaning on the idea of just putting up a
10' mast and using it to support a Van Gordon all bander. My
building is 54x40 and 25' tall so by my math the 135 foot all
bander would overhang on the ground just a bit. There are trees
on the corners of the building so that's where the ends of the
antenna would go.

My current antenna would stay for comparison reasons.

Now - on my 153'2" dipole, I feed it with 12' of rg58 and a
9 turn, 2-5/8" dia coax loop at the feedpoint. Should I
duplicate this feedpoint for the 450 ohm ladder line of the
Van Gordon antenna or should I buy a balun? And if I buy
a balun, what ratio?

Thanks for your help, OM!

73's de Ken KG0WX

Hello,

Put a 10ft pole up and take a wire off each side of the building to form a
giant inverted V. Miniature aerials give tiny performance.

On Sat, 3 Jan 2004 18:06:34 -0700, "Ken Bessler"
wrote:


After thinking a bit I'm leaning on the idea of just putting up a
10' mast and using it to support a Van Gordon all bander. My
building is 54x40 and 25' tall so by my math the 135 foot all
bander would overhang on the ground just a bit. There are trees
on the corners of the building so that's where the ends of the
antenna would go.

My current antenna would stay for comparison reasons.

Now - on my 153'2" dipole, I feed it with 12' of rg58 and a
9 turn, 2-5/8" dia coax loop at the feedpoint. Should I
duplicate this feedpoint for the 450 ohm ladder line of the
Van Gordon antenna or should I buy a balun? And if I buy
a balun, what ratio?

Hi Ken,

I don't see much advantage of one over the other, much less getting
into the benefits of BalUns and ladder line.

Any particular ratio only works if you actually observe that ratio
between line and load or source. This is unlikely if you are using
the antenna as an all bander (a distinction that is suspect in spite
of testimonials). A true all bander comes with issues, and knowing
those issues and responding to them allows all band operation.
However, you can achieve that status with a simple hank of wire, less
the appelation. In other words, you already have an all bander in
your dipole. It couldn't possibly work worse (or better) than the Van
Gordon except through choice of placement. In that regard, higher is
better, and it would seem you have plenty of length already.

IF it doesn't work (because it is whole wave on one band or the other)
you simply pair up a second in parallel (literally at the feed point)
and move on. The sad fact of it is, once you have a decent dipole up
(yours comes close enough), you have to invest many, many more dollars
and step up to a tower and beam to get to the next tier of
performance. Let's face it, few if any have towers supporting 80M
beams (and not many more with full-sized 40M beams).

On the other hand, 12 feet away from the feed point is awfully close.
This means you are literally part of the loss of the system (like a
hamster in a microwave). On the plus side, any high SWR would hardly
offer much loss over such a small run. However, such proximity often
leads to Common Mode issues (does your system refuse to tune some
bands? Even to folding back power?).

73's
Richard Clark, KB7QHC

"Richard Clark" wrote in message
...

Hi Ken,

I don't see much advantage of one over the other, much less getting
into the benefits of BalUns and ladder line.

Any particular ratio only works if you actually observe that ratio
between line and load or source. This is unlikely if you are using
the antenna as an all bander (a distinction that is suspect in spite
of testimonials). A true all bander comes with issues, and knowing
those issues and responding to them allows all band operation.
However, you can achieve that status with a simple hank of wire, less
the appelation. In other words, you already have an all bander in
your dipole. It couldn't possibly work worse (or better) than the Van
Gordon except through choice of placement. In that regard, higher is
better, and it would seem you have plenty of length already.

IF it doesn't work (because it is whole wave on one band or the other)
you simply pair up a second in parallel (literally at the feed point)
and move on. The sad fact of it is, once you have a decent dipole up
(yours comes close enough), you have to invest many, many more dollars
and step up to a tower and beam to get to the next tier of
performance. Let's face it, few if any have towers supporting 80M
beams (and not many more with full-sized 40M beams).

On the other hand, 12 feet away from the feed point is awfully close.
This means you are literally part of the loss of the system (like a
hamster in a microwave). On the plus side, any high SWR would hardly
offer much loss over such a small run. However, such proximity often
leads to Common Mode issues (does your system refuse to tune some
bands? Even to folding back power?).

73's
Richard Clark, KB7QHC

The current antenna will tune up quickly and easily on all bands
from 160-6 meters. I was having some instability problems untill
I tied all equipment grounds to the copper baseboard heater pipe.

Before I did that I would see SWR changes when touching my
rig, my SWR meter, my tuner etc. Not now. I know the hot water
pipe is not supposed to be a good ground but this is working
extremely well.

So, how do you suggest I handle the transition between my coax
run from the tuner and the 450 ohm ladder line?

73's de Ken KG0WX

On Sat, 3 Jan 2004 23:08:16 -0700, "Ken Bessler"
wrote:


The current antenna will tune up quickly and easily on all bands
from 160-6 meters. I was having some instability problems untill
I tied all equipment grounds to the copper baseboard heater pipe.

Before I did that I would see SWR changes when touching my
rig, my SWR meter, my tuner etc. Not now. I know the hot water
pipe is not supposed to be a good ground but this is working
extremely well.

So, how do you suggest I handle the transition between my coax
run from the tuner and the 450 ohm ladder line?

73's de Ken KG0WX

Hi Ken,

Well, gee, I don't know how to put this, but I'd leave things alone.
There is almost nothing you can do that would be
measureable/noticeable from the other end in all likelihood -- unless
everything worked only because your antenna was nothing more than an
aircooled resistor. You could double your output and it would barely
nudge their S-meter.

Use an ordinary 1:1 Current BalUn (to answer your last question). Any
other value (one feels compelled to suggest 1:9) would be just as bad
over much of those frequencies as the 1:1 (except different
frequencies). The upshot of using a Current BalUn is the benefit of
its choking action and a 1:9 may not exhibit that as well; especially
if it is a Voltage BalUn construction.

73's
Richard Clark, KB7QHC

"Richard Clark" wrote in message
...

Hi Ken,

Well, gee, I don't know how to put this, but I'd leave things alone.
There is almost nothing you can do that would be
measureable/noticeable from the other end in all likelihood -- unless
everything worked only because your antenna was nothing more than an
aircooled resistor. You could double your output and it would barely
nudge their S-meter.

Use an ordinary 1:1 Current BalUn (to answer your last question). Any
other value (one feels compelled to suggest 1:9) would be just as bad
over much of those frequencies as the 1:1 (except different
frequencies). The upshot of using a Current BalUn is the benefit of
its choking action and a 1:9 may not exhibit that as well; especially
if it is a Voltage BalUn construction.

73's
Richard Clark, KB7QHC

Thanks for the info, Richard - I went to Eham.net and read the
reviews on the all bander. Not all were good so I started looking
at the other reviews for ideas. Found the MFJ-1788 G5RV
antenna. I'm usually a bit suspicious about MFJ products but
this one got good reviews.

So, what do you think about the G5RV for my situation? The
apex would be at 35' and the ends would be about 20' The 34'
of ladder line would reach my window feedpoint just fine then
I could make a coax choke (MFJ says 10 turns @ 4-6" dia) and
then feed it to my LDG tuner. the coax run would be about 8'.

A note on choke construction - I use plastic forms to wind the
coax then glue the turns together with superglue and baking
soda. I only have two smooth plastic forms avaiable - a 2-5/8"
and a 5 inch. So, I could make a 10 turn, 5" dia choke for this
new antenna.

Your thoughts?

Ken KG0WX