In this RV park..the only flag that wouldnt get stolen is the Mexican
flag. Few of my neighbors are english speakers.
But its an idea.
"That which does not kill you,
has made a huge tactical error"
LOL...Yeah Gunner, I know you google, etc...
Which leads me to believe that you posted this as a spark (some on
topic for a change), there are a half a dozen site with plans for
simple magnetic (Ferrit bar and magnitic wire, you know the crap they
call an antenna inside an el-cheapo transister radio) which is most
likely what you'll end upmaking in the long run with your requirements
for 'low profile' Hell Gunner, just whip up one of those damn magnetic
antenns, make sure you've got plenty of lead wire, and simply set the
damn thing in which ever window works best for the station you are
tuning to. You can't get no lower profile then that and expect to
actually pick up anything., Heck, with a say 24 inch piece of ferrit,
wrap it with around 30 feet or so of magnetic wire. You can even add a
tuning cap if you want to get fancy, but as a general coverage antenna
you don't need all that for just receiving, YMMV. You can mount this
type of antenna in the window(s) either flat or top side.
If you need to be lower profile then the above, might I suggest a coat
Forgot a couple of things about ferrit rod antennas. Since you might
be using this antenna indoors (like inside of a window) simply connect
the "Antenna" wire to one end of the coated magnetic wire (remove
coating where required), the magnitic wire should be wound around the
ferrit rod leaving an inch or two or rod unwrapped and each end. You
can tape up this whole mess or stick it inside of a piece of PVC or
whatever (plastic) to make hanging the antenna easier. Because your in
a metal RV, if you ground the radio to the frame, you will increase
the shielding effect of the Rv's body, so I suggest using some plain
old speaker wire cut to the same lenth as the magnetic wire in your
antenna, and lay this wire out on the floor, behind shit, out of the
way, but stretched out. Use this for your antenna ground.
If you place the antenna "outside" then none of this shit matters and
ground away...Anyways, it's not coat hanger and tin foil, but it ought
to work just as well.
I really want to listen to the SW bands. I think Ill dig into my
Stuff when finally go home this weekend and see what Ive got stashed
in my comm gear bins. I like the idea of the wire on standoffs around
the edge of the roof. Attaching them is going to be problematic.
"That which does not kill you,
has made a huge tactical error"
Tue, 05 Apr 2005 10:01:20 GMT, Gunner wrote: Begin
For the antenna: Sony AN-1 (looks innocuous like a car antenna)
For the noise: Timewave ANC-4
Not sure what your ambient RF level (KNX etc.) is at that location, but
maybe a pre-selector would allow for weaker DX stations. I have an old
Grove TUN-4 but I don't' think he still markets it. Some active antennas
include a pre-selector.
Antenna matching is only for extremely challenging receiving (which this
is not), or for transmitting.
Unless your radio is real crap you'll be receiving atmospheric noise in
excess of the receiver's internal noise with even a moderate antenna.
Atmospheric noise drops off at the higher frequencies, but the antenna
effectiveness will increase for a moderately - sized antenna. If you
really want to disguise what you're doing then mount the TV mast with
insulators, put in a good radial grounding system, and use the whole TV
mast as an antenna.
This scheme requires that you either build a diplexer to isolate the TV
coax outer shield from ground at the lower frequencies or disconnect the
TV when you want to listen to SW. The former will be moderately
difficult but not insurmountable -- I think you could do this with a 1:1
RF transformer and some dinking. The latter will be easy but
inconvenient -- but you can always start with the connection method and
build the transformer later.
The ARRL sells a book on low-profile and hidden antennas. You can go to
http://www.arrl.org for more information, or see if there's an amateur
radio supply store near you. They also sell books on reducing EMI,
which may help with the computer.
Stealth antennae are very site and situation specific. Think camou:
use your ingenuity to devise a conductor of some extent that looks
like something the rules don't forbid or is invisible because it looks
like something familiar. Flagpoles, cutesie picket fences,
clotheslines, a rabbit hutch made of chickenwire, decorative
low-voltage lighting as is often used on RV's, etc etc.
Electrically short antennae have very very low radiation resistance,
so a tuned matching network can make a big difference. I disagree
with the poster that said they are only suitable for transmitting,
though I will agree that once you reach atmospheric noise threshold
then further gain t without directionality is of little benefit.
The matchbox would need to be tuned along with the rcvr. Tune for max
noise from the radio at the freq of interest. A simple JFET preamp
may help, or not, depending on the sensitivity of the radio. If the
radio has a 3-gang tuning cap then it already has a tuned RF stage.
If it doesn't, then a preamp will help.
If the mast is wood, you could wind a helix around it. If it has guy
wires, you could insulate at the top and bottom and make a sloping V
with multiple feeds to change direction.
Sure.... assume an infinite trailer roof. :)
Gunner may want to look at a grounded horizontal loop running around the
perimeter of the trailer roof, far enough from the edge that the antenna
isn't visible from the ground. Bring the end down the side of the
trailer a couple of inches and put the tuning capacitor inside.
Look at the HF antenna on the Chinook as an example.
Third picture down:
Among the disadvantages are non-portability and the need to rip it off
when you move the trailer.
You don't want to get too wrapped around the antenna. Down at those
frequencies it takes a real big directional antenna- like a Beverage or
a Rhombic- to make a big difference. (The one at work that was used to
talk around the world is about the size of perhaps six football fields)
Otherwise you are sucking in as much noise as signal.
Make sure you use Monster cable for good reception.
How about a "telephone wire" or "intercom wire" from your RV to
another one? You can decouple the RF with capacitors so that the wire
can also be used as an antenna as well as its official purpose.
"A Springfield woman who began lobbying against gun violence after
her son was shot to death in 2002 was arrested last week when
Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here.
All logos and trade names are the property of their respective owners.