[ScanIndiana] talkgroup 13024 active on Lebannon safe-t site
Duane Mantick
wb9omc at nlci.com
Sun Jan 30 15:53:05 EST 2005
Ahhhh, grasshopper, I am glad you asked that question. :-)
Owing to homeowner restrictions and being an Amateur I have
been forced to become someone adept at adapting the old attic
for antenna work.
Basically, you can put just about anything you want up there;
it all depends on your roof truss arrangement and spacing. I
have a multi-element wire dipole that has a 10 meter element
and a 20 meter element. The 10 meter element is about 16 feet
long and the 20 meter element is about 33 feet long if memory
serves correctly. The 20 meter element is the longest *straight*
run of wire I can get up there unless I do some fancy finagling
over the east end of the house. Deadly enemy for in-attic
antenna work: special trusses for a cathedral ceiling.
So that one is long, straight wires. Also have a second 10 meter
only dipole that is perpendicular to the other one and
physically located off the end of the first.
There are three ground planes up there, one that is a stock
Radio Shack scanner antenna - works good for reception from
a bit below 100 Mhz clear up into the 400 Mhz area. Next
GP is close in size - it is transmit for 2 meters but also
makes a good receiving antenna in a similar freq. range.
A more recent addition is a little ground plane to work the
Amateur 440 band; that's 70 cm for those who want to look at
it from the wavelength side of the equation. Also a 220 MHz
band, or 1.25 Meters wavelength. Again, these also make good
receiving antennas and are fairly broadbanded, vertical
polarization which is correct for most mobile and public
service operations.
These little ground planes are cheap and easy to make. They use
brass rod stock, which you can get at many hardware stores,
which also happens to solder very well. The center piece is a
panel mount SO-239 connector. This has a square flange with
four holes in it. You make the antenna by cutting your vertical
element to X length (at 2 meters, it is approx. 19 inches....
in one of my books, I think I have a chart that shows the
correct lengths of both the vertical element and the four radials
for a variety of frequencies. This is not terribly critical
if you're only *receiving*.) Oh, you need to buy a *diameter* of
this brass rod that is small enough to fit into the back
of the SO-239 where you'd normally solder a wire in place. You
may need to fashion some kind of cheap and quick "fixture" to
hold the rod straight while you solder it in place. As for the
4 radials, cut them a bit longer, not much, than the vertical
element. Then use pliers to turn a "loop" on one end of each
radial. Use 4-40 hardware (I strongly suggest stainless steel
here - you can torque it down tightly and it strongly resists
corrosion) and bolt each radial to each of the 4 holes in the
SO-239. They should stick straight out from the center, and
thus be at 90 degree angles from each other in a plane perpendicular
to the vertical element. Then, once having tightened them down
solidly, bend each radial DOWN (AWAY from the vertical element)
at approx. 45 degrees. Some people will say that for reception
only you don't need to do this - I have not compared them for
reception with vs. without. Using them as transmitting antennas,
the "drooped" radials tend to "pull down" your outgoing signal
towards the ground, meaning less of your output power is
wasted in an upward direction and instead, sent more parallel
to the ground and thus, more within "line of sight".
To mount one of these, the easiest way to do it is with plastic pipe.
Use a plumber's PVC pipe that has an inside diameter just slightly
larger than the PL-259 coax connector that you will plug into the
SO-239 that makes up the main body of the antenna. Calling most
of this from memory, I don't remember which size that is but if you
buy a PL-259 and then take it with you you can test fit the PVC
pipe. You use either a motor tool or a hacksaw and cut two slits,
one on each side of the pipe and back from the end about an inch
to inch and a half. Run the coax up through the pipe, attach it
to the SO-239 on the antenna, and then let it slide back down into
the pipe until the body of the SO-239 rests on top. Why the slits?
If you use a hose clamp or heck, even a good stout wire tie around
it, it will then snug up onto the PL259 and hold the antenna in
place. This isn't so critical in the attic where there should be
no wind. :-) You CAN just let it sit on top if you are able to
mount the PVC pipe vertically; no reason why it should fall off.
I also have a "halo-6" for six meters, and on a variation of the
ground plane above, instead of rod stock I used stranded antenna
wire stapled to the trusses to create a ground plane big enough
for CB (11 meters, in the low 27 MHz range) which would make a
dandy receiving antenna for anything from about 5 MHz clear up
to about 50 Mhz. Yup, it does work. :-)
That's about all for now. Please feel free to post back if you
want more details. I'm getting called to eat and need to log off
for now.
Duane
WB9OMC
-----Original Message-----
From: scanindiana-bounces at mailman.qth.net
[mailto:scanindiana-bounces at mailman.qth.net] On Behalf Of Terry Hoover
Sent: Sunday, January 30, 2005 1:54 PM
To: Indiana Scanning
Subject: RE: [ScanIndiana] talkgroup 13024 active on Lebannon safe-t site
Could I benefit from an antenna in the attic of my home? I live in a sub
that has outdoor antenna restrictions I can barely get by with a Satelite
dish, if I can get by with an Ant in the Attic which type of ant. would I
get the most bang for my buck?
-----Original Message-----
From: scanindiana-bounces at mailman.qth.net
[mailto:scanindiana-bounces at mailman.qth.net]On Behalf Of Tim DeLong
Sent: Saturday, January 29, 2005 8:11 PM
To: scanindiana at mailman.qth.net
Subject: [ScanIndiana] talkgroup 13024 active on Lebannon safe-t site
Gentlemen, I am hearing Crawsfordville Police Dispatch on the Lebannon
safe-t site,I have a Bearcat 796D using the back of set antenna that came
with the radio,I live on the northwest side of Indianapolis around 79Th and
Michigan road in a two story home.My radios are up on the second
floor,height wise I am up at 40-50 feet above ground with out a tower.I am
also hearing Dist 14-Laffayette Post ISP Best Requards Tim DeLong W9NES
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