ThornyI
Member
My sheriffs dept. is on UHF, they break up a lot. Anyone have any recomedations for a homemade antenna? I've heard of them and I figured I'd give it a shot.
UHF Antenna - Homemade?
- Thread starter ThornyI
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merlin-7
Member
A base type antenna?
N
N_Jay
Guest
ThornyI said:
Coaxial Dipole, fed with the best cable you can afford, mounted as high as practical.
ThornyI
Member
yes, base. i cannot put anything on top of my house. subdivision rule, so how could i make an inside antenna?
merlin-7
Member
ditto N_ray
There are plans for coax dipoles on the net. The only big difference between any of them is the length (depends on what frequency you want )
There are plans for coax dipoles on the net. The only big difference between any of them is the length (depends on what frequency you want )
N
N_Jay
Guest
ThornyI said:
You take an outside antenna and put it in the attic.
merlin-7
Member
most dipoles can be placed at the peek of your roof and no one would ever notice it.
It is just coax cable and if it is the same color as your shingles....or if you have a ridge vent. you could place it right behind it.
Rember if no one can see it.....
It is just coax cable and if it is the same color as your shingles....or if you have a ridge vent. you could place it right behind it.
Rember if no one can see it.....
PointMan
Member
- Joined
- Jun 13, 2004
- Messages
- 36
Do you have a condo or a apartment kind of situation? If its something that gives you acess to a yard thats one thing. If you only have a window or a balcony then that steers us in another.
If you have a balcony but cant show antennas, id just go with the vice grips mounted 1/4 wave antenna, you clamp the vice grips to a mettle railing and your in bidness! If you only have a window, you could get a 3 foot piece of strap aluminum from home depot, then drill a 3/4 inch hole through that, and put a NMO mount antenna through the hole. Then close the window on your aluminum strap and the coax (carefully) and theres your window mount.
If you have acess to a yard, can you get to a tree? If so, you could spray paint a 1/4 or 5/8ths wave antenna flat black, or dark brown, and mount that in the tree maybee? Run some low loss RG-8 coax or LMR-400 from there to your scanner?
If its a yard with no trees, then its a little more tough. If there is a cable TV line running to the ceeling, can you deck out in black BDU's and use a ladder one night to run the coax to the roof next to it? This way it would be less obvous, and you could do the wire antenna with coax ground at the point where the cable TV coax dissapears into the wall. If you get caught doing your night time antenna OP, just confess to being a terrorist, i hear they like terrorists more than radio people (professional courtousey) when it comes to homeowners groups.
Some other things I had thought of but never had to do, were things like putting a fake plumbing vent on the roof, which was really a black painted piece of pipe, tuned to the right freq. The large diameter of the pipe should in theory offer broader bandwidth, which is good for scanning. Then run 4 wires under the shingles as a counterpoise and atatch that to the copper braid on the coax. If viewed from the publics point of view, its just one of "Those pipe things" that they have heard has something to do with plumbing.
I hear MFJ enterprises has 10 foot telescoping fiberglass masts. Theyre black, which is good for covert stuff. You could go outside at night, erect that SOB with a 1/4 wave antenna on the top, and run the coax inside. Then knock it down when your done, if its not near a road or a side walk, or passing in front of someones window, they might not notice it.
Attic acess would be a huge help. A dipole cut from thin wire outside a vent would be hard to spot. Same would go for a chimney or an air conditioning unit duct. These offer the highest possible height too, which is what youd really want for UHF.
On the off the wall, WTF is wrong with this guy end of the spectrum, there is another setup that I have done. I made an antenna, that will probably draw flame from someone because its labled a short wave antenna. I was looking to experiment with something other than AWA (Another Whip Antenna) and i stumbled across the half rhombic inverted vee antenna. Imagine a V upside down, each leg of the V at least one wavelength in length. I was going for 151 MHz for MURS use, so I made each leg 6 wavelengths (about 39 feet per leg). I raised the center of the antenna with #550 parachute cord, atatched one end to the BC9000 and simply tied the other end to a plastic tent stake so it wasnt conductive. The antenna pulled signals in from a 154 MHz Pennsylvania fire dept I couldnt recieve on any of my scanner antennas. These were a raio shack discone, a diamond discone, a 1/4 wave MURS antenna cut to length, and a cush craft 3 element MURS beam. The BC900 doesnt have a signal strength meter, so all I can say is it preformed wicked pisser! The signal was above the noise floor, and i could make out street names and the nature of a entrapment call. Would it preform better than the MURS beam up at the 30 foot height like the inverted C's tip was? No probably not, but the beam was hand held. But could we hide a 3 element beam on the eve of a roof? No not easily. See the inverted vee could be hidden under the shingles at the side of a peaked roof, coax running to one end. The number of wavelengths could be increased quite a bit, and it would be lacking real earth underneath it. But its an idea. The V I used was pointed in the east west direction, since these things are fairly bi-directional without a terminating resistor, which was more BS than I wanted to go through. The impedence is probably no 50 ohms, but I bet those end all miracle scanner magnet mounts arent either, especialy when the wind over a car roof blows the coax out of the antenna base like mine did!
Oh did I mention, you could always try putting a miracle end all magnet mount scanner antenna on top of the fridge!
If you have a balcony but cant show antennas, id just go with the vice grips mounted 1/4 wave antenna, you clamp the vice grips to a mettle railing and your in bidness! If you only have a window, you could get a 3 foot piece of strap aluminum from home depot, then drill a 3/4 inch hole through that, and put a NMO mount antenna through the hole. Then close the window on your aluminum strap and the coax (carefully) and theres your window mount.
If you have acess to a yard, can you get to a tree? If so, you could spray paint a 1/4 or 5/8ths wave antenna flat black, or dark brown, and mount that in the tree maybee? Run some low loss RG-8 coax or LMR-400 from there to your scanner?
If its a yard with no trees, then its a little more tough. If there is a cable TV line running to the ceeling, can you deck out in black BDU's and use a ladder one night to run the coax to the roof next to it? This way it would be less obvous, and you could do the wire antenna with coax ground at the point where the cable TV coax dissapears into the wall. If you get caught doing your night time antenna OP, just confess to being a terrorist, i hear they like terrorists more than radio people (professional courtousey) when it comes to homeowners groups.
Some other things I had thought of but never had to do, were things like putting a fake plumbing vent on the roof, which was really a black painted piece of pipe, tuned to the right freq. The large diameter of the pipe should in theory offer broader bandwidth, which is good for scanning. Then run 4 wires under the shingles as a counterpoise and atatch that to the copper braid on the coax. If viewed from the publics point of view, its just one of "Those pipe things" that they have heard has something to do with plumbing.
I hear MFJ enterprises has 10 foot telescoping fiberglass masts. Theyre black, which is good for covert stuff. You could go outside at night, erect that SOB with a 1/4 wave antenna on the top, and run the coax inside. Then knock it down when your done, if its not near a road or a side walk, or passing in front of someones window, they might not notice it.
Attic acess would be a huge help. A dipole cut from thin wire outside a vent would be hard to spot. Same would go for a chimney or an air conditioning unit duct. These offer the highest possible height too, which is what youd really want for UHF.
On the off the wall, WTF is wrong with this guy end of the spectrum, there is another setup that I have done. I made an antenna, that will probably draw flame from someone because its labled a short wave antenna. I was looking to experiment with something other than AWA (Another Whip Antenna) and i stumbled across the half rhombic inverted vee antenna. Imagine a V upside down, each leg of the V at least one wavelength in length. I was going for 151 MHz for MURS use, so I made each leg 6 wavelengths (about 39 feet per leg). I raised the center of the antenna with #550 parachute cord, atatched one end to the BC9000 and simply tied the other end to a plastic tent stake so it wasnt conductive. The antenna pulled signals in from a 154 MHz Pennsylvania fire dept I couldnt recieve on any of my scanner antennas. These were a raio shack discone, a diamond discone, a 1/4 wave MURS antenna cut to length, and a cush craft 3 element MURS beam. The BC900 doesnt have a signal strength meter, so all I can say is it preformed wicked pisser! The signal was above the noise floor, and i could make out street names and the nature of a entrapment call. Would it preform better than the MURS beam up at the 30 foot height like the inverted C's tip was? No probably not, but the beam was hand held. But could we hide a 3 element beam on the eve of a roof? No not easily. See the inverted vee could be hidden under the shingles at the side of a peaked roof, coax running to one end. The number of wavelengths could be increased quite a bit, and it would be lacking real earth underneath it. But its an idea. The V I used was pointed in the east west direction, since these things are fairly bi-directional without a terminating resistor, which was more BS than I wanted to go through. The impedence is probably no 50 ohms, but I bet those end all miracle scanner magnet mounts arent either, especialy when the wind over a car roof blows the coax out of the antenna base like mine did!
Oh did I mention, you could always try putting a miracle end all magnet mount scanner antenna on top of the fridge!
PointMan said:
I had to stop reading after that, too funny :mrgreen: :lol:
PointMan
Member
- Joined
- Jun 13, 2004
- Messages
- 36
Lol yea, I was trying to illustrate that youd have to be sneaky, and then I thought about it and said "Nah, theyle think im serious about the black BDU's and ill get flamed like a WW2 jap machine gunner inside a pillbox"
But then, I have installed a few antennas in black BDU's.... maybee I am a loony toon.... OH crap, I just missed the short bus! Cooooome BACK!
But then, I have installed a few antennas in black BDU's.... maybee I am a loony toon.... OH crap, I just missed the short bus! Cooooome BACK!
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