Our local fire station would like us to provide an HF station to be
operated by hams during an emergencies. They have offered to pay the
cost of this. We already have an VHF station there. The problem is the
antenna. It cannot be visible (or at least not be at all obvious; they
are allowing the VHF antenna on the roof now.). The most likely needed
band is 75/80 meters, for in-state communications. So we need high-angle
radiation, and a vertical does not seem to be a good choice.

The roof is metal, so putting an antenna in the attic will not work.
The building is a fairly large 2 or 3 story structure, and in the
country with no other buildings nearby.

Here are some ideas I have:

1, A horizontal loop, running all around the building up near the top,
but somewhat below the metal roof. Would likely be non-resonant,
although perhaps we could choose the length. Mount it on stand-off
insulators just off the wooden siding. Use white insulated wire and
paint all hardware white, to blend in with the white siding. Feed it at
some convenient point, perhaps with a 4:1 balun and then coax into the
building. Open wire feed would be better, but we cannot get that into
the building and down to the station. Use a coax antenna tuner in the
station. The SWR would not be good, but the losses of RG/8 at 75M are
not that high. Maybe we could use some kind of outdoor automatic tuner
directly connected to the antenna, but I don't know of any offhand.

2. Use the rain gutters as an antenna. I did this long ago in a house
and it worked fairly well on 40M. Bridge all the joints with copper
braid, painted white, to endure reliable connections. At one of the
corner downspouts near the ground, connect the center conductor of a
coax cable to the downspout. Bury radials extending out from the
building an appropriate length, in a 270 degree sector, and connect to
the shield.
I don't know if the gutters are connected to the metal roof, but if so
that might or might not rule out this approach. Use a coax antenna
tuner in the station. I know this is basically a top-loaded vertical
antenna, but the choices are limited.

Comments on both these ideas, and other alternative suggestions, would
be greatly appreciated.

73,

Bob W8ERD

Do they have a flagpole?

"Bob Dixon" wrote in message
...
Our local fire station would like us to provide an HF station to be
operated by hams during an emergencies. They have offered to pay the
cost of this. We already have an VHF station there. The problem is the
antenna. It cannot be visible (or at least not be at all obvious; they
are allowing the VHF antenna on the roof now.). The most likely needed
band is 75/80 meters, for in-state communications. So we need high-angle
radiation, and a vertical does not seem to be a good choice.

The roof is metal, so putting an antenna in the attic will not work.
The building is a fairly large 2 or 3 story structure, and in the
country with no other buildings nearby.

Here are some ideas I have:

1, A horizontal loop, running all around the building up near the top,
but somewhat below the metal roof. Would likely be non-resonant,
although perhaps we could choose the length. Mount it on stand-off
insulators just off the wooden siding. Use white insulated wire and
paint all hardware white, to blend in with the white siding. Feed it at
some convenient point, perhaps with a 4:1 balun and then coax into the
building. Open wire feed would be better, but we cannot get that into
the building and down to the station. Use a coax antenna tuner in the
station. The SWR would not be good, but the losses of RG/8 at 75M are
not that high. Maybe we could use some kind of outdoor automatic tuner
directly connected to the antenna, but I don't know of any offhand.

2. Use the rain gutters as an antenna. I did this long ago in a house
and it worked fairly well on 40M. Bridge all the joints with copper
braid, painted white, to endure reliable connections. At one of the
corner downspouts near the ground, connect the center conductor of a
coax cable to the downspout. Bury radials extending out from the
building an appropriate length, in a 270 degree sector, and connect to
the shield.
I don't know if the gutters are connected to the metal roof, but if so
that might or might not rule out this approach. Use a coax antenna
tuner in the station. I know this is basically a top-loaded vertical
antenna, but the choices are limited.

Comments on both these ideas, and other alternative suggestions, would
be greatly appreciated.

73,

Bob W8ERD

"Bob Dixon" wrote in message
...
Our local fire station would like us to provide an HF station to be
operated by hams during an emergencies. They have offered to pay the
cost of this. We already have an VHF station there. The problem is the
antenna. It cannot be visible (or at least not be at all obvious; they
are allowing the VHF antenna on the roof now.). The most likely needed
band is 75/80 meters, for in-state communications. So we need high-angle
radiation, and a vertical does not seem to be a good choice.

The roof is metal, so putting an antenna in the attic will not work.
The building is a fairly large 2 or 3 story structure, and in the
country with no other buildings nearby.

**********************
How about a 1/4 wave radiator, sloping down from the roof, with the shield
of the coax connected to the metal roof. It would take some trimming. If you
use black insulated wire, it will be almost invisible.

Tam

Hi Bob

I guess one should ask how big the roof is... Be handy for modeling the
thing.

Since you probably want a set and forget installation with no tuning
needed across the 80m (or other) bands, it may be worthwhile looking to
a resistive terminated antenna rather than trying to make it
resonant/low Z by its size. Kind of like a TFDP but maybe a loop
construction using very thin (say) stainless steel wire. I would guess
that a balun would still be needed but by playing with a terminating
resistor you may be able to make it multiband. Perhaps running around
the edges of the roof above the gutter line wont be very visible.

Does the fire station have one of those hose drying towers? I realize
you want NVIS rather than vertical pol low angle but it may be worth
considering that avenue.

I guess a roof mounted DDRR would be too visible..

A magloop can be small but there might be an efficiency issue there.

A balloon lifted antenna only for use during emergencies or exercises?

If the building is indeed way out in the country are there any trees
within a few 100 yards? Perhaps some underground coax to an antenna
structure would do it. Cecil has this interesting design at
http://www.w5dxp.com/notuner.htm that uses ribbon cable switched in and
out for the bands you want to use. This switching could be remoted with
the use of relays.

Apologies for not being too specific..

Cheers Bob W5/VK2YQA

Bob Dixon wrote:
Our local fire station would like us to provide an HF station to be
operated by hams during an emergencies.

How about running a `Zep out to the flagpole or telephone pole? All
but invisible and if it's seen, not too many people would even think
twice about it.

FFF

On Fri, 09 Feb 2007 15:59:46 -0500, Bob Dixon wrote:

Our local fire station would like us to provide an HF station to be
operated by hams during an emergencies. They have offered to pay the
cost of this. We already have an VHF station there. The problem is the
antenna. It cannot be visible (or at least not be at all obvious; they
are allowing the VHF antenna on the roof now.). The most likely needed
band is 75/80 meters, for in-state communications. So we need high-angle
radiation, and a vertical does not seem to be a good choice.

The roof is metal, so putting an antenna in the attic will not work.
The building is a fairly large 2 or 3 story structure, and in the
country with no other buildings nearby.

Here are some ideas I have:

1, A horizontal loop, running all around the building up near the top,
but somewhat below the metal roof. Would likely be non-resonant,
although perhaps we could choose the length. Mount it on stand-off
insulators just off the wooden siding. Use white insulated wire and
paint all hardware white, to blend in with the white siding. Feed it at
some convenient point, perhaps with a 4:1 balun and then coax into the
building. Open wire feed would be better, but we cannot get that into
the building and down to the station. Use a coax antenna tuner in the
station. The SWR would not be good, but the losses of RG/8 at 75M are
not that high. Maybe we could use some kind of outdoor automatic tuner
directly connected to the antenna, but I don't know of any offhand.

2. Use the rain gutters as an antenna. I did this long ago in a house
and it worked fairly well on 40M. Bridge all the joints with copper
braid, painted white, to endure reliable connections. At one of the
corner downspouts near the ground, connect the center conductor of a
coax cable to the downspout. Bury radials extending out from the
building an appropriate length, in a 270 degree sector, and connect to
the shield.
I don't know if the gutters are connected to the metal roof, but if so
that might or might not rule out this approach. Use a coax antenna
tuner in the station. I know this is basically a top-loaded vertical
antenna, but the choices are limited.

Comments on both these ideas, and other alternative suggestions, would
be greatly appreciated.

73,

Bob W8ERD

It seems to me that a simple dipole would work fine or an inverted V. All
the fire stations I know of already have a tower of some kind to place the
feed point.
All you would need is about 66' of wire off each side slopeing toward the
ground at the ends (to make it more omnidirectional )
Black stealth wire comes to mind. The wireman sells it online (just google
thewireman) It is very hard to see.
Or you could buy a pre-made dipole for 75 / 80 meters.

My 2 cents.

Joe

Our local fire station would like us to provide an HF station to be
operated by hams during an emergencies.

Emergencies? You mean like in the case of a disaster such as a tornado in
your community , you might be called upon to provide communications that could
save peoples lives and property? You mean, you may be able to provide a
communications link to other government agencies in your state when all other
ones fail? This is impressive, and this is a great responsibility and you are
to be commended for accepting such a responsibility, and providing such a
service to your fellow citizens.
Now you need to lay the law down to your fellow
citizens/politicians/firefighters. You need an antenna. It requires a
support, such as a 30-40 ft tower, one that will survive whatever disasters
you forsee, such as wind storms, floods, snow/ice storms (no, it will not
survive a direct tornado hit, we all know that). It needs to be vandal-proof,
not climbable by kids, etc. You can tell them it will have 2 simple wires
running off of it and will look like an letter vee upside down. You can tell
them not to waste your time because they are not serious about saving peoples
lives if they expect you to do such Mickey Mouse things as loading up the rain
gutters, disguising wire antennas around the roof of the building, or any
other such foolishness. An antenna that will do what they expect is 2 simple
pieces of wire 65 feet long connected to some coax cable suspended 30-40 feet
in the air. Tell them if they handcuff you into doing anything else they
really weren't serious in the first place. Aesthetics have no place when we
are talking about saving peoples lives. Imagine if you were ever called to
put into action your ham station, and firefighters were standing behind you
looking over your shoulder, and you couldn't be heard because the the friggin
rain gutter wouldn't load up. Give me a break.

Rick K2XT

"Rick" wrote in message
...

Our local fire station would like us to provide an HF station to be
operated by hams during an emergencies.

Emergencies? You mean like in the case of a disaster such as a tornado in
your community , you might be called upon to provide communications that
could
save peoples lives and property? You mean, you may be able to provide a
communications link to other government agencies in your state when all
other
ones fail? This is impressive, and this is a great responsibility and you
are
to be commended for accepting such a responsibility, and providing such a
service to your fellow citizens.
Now you need to lay the law down to your fellow
citizens/politicians/firefighters. You need an antenna. It requires a
support, such as a 30-40 ft tower, one that will survive whatever
disasters
you forsee, such as wind storms, floods, snow/ice storms (no, it will not
survive a direct tornado hit, we all know that). It needs to be
vandal-proof,
not climbable by kids, etc. You can tell them it will have 2 simple wires
running off of it and will look like an letter vee upside down. You can
tell
them not to waste your time because they are not serious about saving
peoples
lives if they expect you to do such Mickey Mouse things as loading up the
rain
gutters, disguising wire antennas around the roof of the building, or any
other such foolishness. An antenna that will do what they expect is 2
simple
pieces of wire 65 feet long connected to some coax cable suspended 30-40
feet
in the air. Tell them if they handcuff you into doing anything else they
really weren't serious in the first place. Aesthetics have no place when
we
are talking about saving peoples lives. Imagine if you were ever called
to
put into action your ham station, and firefighters were standing behind
you
looking over your shoulder, and you couldn't be heard because the the
friggin
rain gutter wouldn't load up. Give me a break.

Rick K2XT


That was my exect thoughts. If they want to save lives and be prepared for
an emergency thye should provide a way to support a wire abotu 130 feet long
fed in the middle with a piece of rg-8 type coax. If not tell them to
forget it and take your VHF antenna and equipment with you.

Someone mentioned a DDRR on the roof. That may work ok, but the bandwidth
is very narrow on 75 meters and can cause problems when you may need to
change frequencies.

What type of antenna system are they using for the fire trucks ?
It may be like it is here, there is not much communications gear at the
station, but a central dispatch point for several stations. You may need to
do something like that and put the HF station at another location.

On Fri, 09 Feb 2007 15:59:46 -0500, Bob Dixon wrote:

The problem is the antenna.

Not ready for prime-time.

Mission defines the requirements, unless this is to be designed to the
standards of Homeland Insecurity.

If push comes to shove, the troops of Desert Storm used wire on the
ground (sand actually). It had the form of a capital H, fed in the
middle of the cross bar.

73's
Richard Clark, KB7QHC

You could mount a SCREWDRIVER antenna either to the roof or maybe on a leg
of the antenna support structure if they have one for the regular FD
antenna!

"Bob Dixon" wrote in message
...
Our local fire station would like us to provide an HF station to be
operated by hams during an emergencies. They have offered to pay the
cost of this. We already have an VHF station there. The problem is the
antenna. It cannot be visible (or at least not be at all obvious; they
are allowing the VHF antenna on the roof now.). The most likely needed
band is 75/80 meters, for in-state communications. So we need high-angle
radiation, and a vertical does not seem to be a good choice.

The roof is metal, so putting an antenna in the attic will not work.
The building is a fairly large 2 or 3 story structure, and in the
country with no other buildings nearby.

Here are some ideas I have:

1, A horizontal loop, running all around the building up near the top,
but somewhat below the metal roof. Would likely be non-resonant,
although perhaps we could choose the length. Mount it on stand-off
insulators just off the wooden siding. Use white insulated wire and
paint all hardware white, to blend in with the white siding. Feed it at
some convenient point, perhaps with a 4:1 balun and then coax into the
building. Open wire feed would be better, but we cannot get that into
the building and down to the station. Use a coax antenna tuner in the
station. The SWR would not be good, but the losses of RG/8 at 75M are
not that high. Maybe we could use some kind of outdoor automatic tuner
directly connected to the antenna, but I don't know of any offhand.

2. Use the rain gutters as an antenna. I did this long ago in a house
and it worked fairly well on 40M. Bridge all the joints with copper
braid, painted white, to endure reliable connections. At one of the
corner downspouts near the ground, connect the center conductor of a
coax cable to the downspout. Bury radials extending out from the
building an appropriate length, in a 270 degree sector, and connect to
the shield.
I don't know if the gutters are connected to the metal roof, but if so
that might or might not rule out this approach. Use a coax antenna
tuner in the station. I know this is basically a top-loaded vertical
antenna, but the choices are limited.

Comments on both these ideas, and other alternative suggestions, would
be greatly appreciated.

73,

Bob W8ERD