Radio Question

Tue, 05 Apr 2005 16:16:13 GMT, Gunner wrote: Begin


It's such a common old ruse that maybe no one thought to mention it, but the PVC flagpole (wire inside) might be a go if you fly the appropriate flags from it.
--

Bart

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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.
Gunner
Rule #35 "That which does not kill you, has made a huge tactical error"
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Wed, 06 Apr 2005 03:51:35 GMT, Gunner wrote: Begin

How about the UFW flag http://tinyurl.com/5ss7b
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Bart

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I actually have one of them. Long story. <G>
Gunner
Rule #35 "That which does not kill you, has made a huge tactical error"
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said:

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 hanger.
n.
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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. n.
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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.
Gunner
Rule #35 "That which does not kill you, has made a huge tactical error"
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6 mHz in the evenings is good....
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wrote:

2 X 6's laid on their 6" side around th' perimeter with eyebolt standoffs screwed in every couple of feet to string th' wire through. Time to move? Just dismantle and throw 'em inside.
Snarl
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On Thu, 07 Apr 2005 16:52:28 -0700, snipped-for-privacy@trippin.net wrote:

Not bad...not bad at all. Well done!
Gunner
Rule #35 "That which does not kill you, has made a huge tactical error"
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wrote:

Us trailer trash have to help each other out, doncha know <g>.
Snarl
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How about one of the flagpole antennas?
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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.
--

Bart

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Gunner wrote:

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.
--

Tim Wescott
Wescott Design Services
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wrote:

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.
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Gunner wrote:

Make an insulated base for the yagi pole and put insulators in the guy wires. Now you've got a 12' whip antena. Should work pretty good.
Ted
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Hmm. I like that. Could even be loaded at the bottom. The trailer roof now makes a lovely ground plane. Am I allowed to say 'ground plane' now?
Jim
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jim rozen wrote:

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: http://www.chinook-helicopter.com/Jurassic_Park/Ichthyosaur/Ichthyosaur_8.html
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.
Kevin Gallimore
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Ted Edwards wrote:

I was going to suggest this but thought I'd read the rest before doing so. :-) If it was for a specific freq it could even still be grounded at the base and fed with a Gamma match. :-) ...lew...
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wrote:
<snip>

<snip>
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
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