Scanner antenna

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KK4SYW

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Any suggestions for an easy-to-build scanner antenna? I would like it to cover a wide range of frequencies such as the 2 meter ham band, police, fire, and other emergency frequencies. Any help would be greatly appreciated.
 

popnokick

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Search OCFD and/or Off-Center Fed Dipole in this forum for a very detailed thread of messages and building plans. So simple, cheap, and effective you can't afford not to try one of the many varieties described in the thread. For about $8 in parts and 30 minutes of your time you can quickly make the one based on a 75 to 300 ohm twinlead to coax TV transformer.
 

mikesjoint

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want opinion on scanner antenna idea

i live in a house that i can not have an antenna on the outside of the house, my scanner is upstairs, in the 2 story home. i have been seeing stuff on the off center fed dipole made of copper, i admit i like the simplicity of this, i just wonder is there something that would recieve better, my idea is to maybe build a center fed dipole, of twin lead, with 3 or 4 strips of twin lead, si it could be cut for 6 or 8 bands, in my idea i would enclose it in pvc pipe, and stand it in the corner behind the desk,, i question if the layers of twin lead laying on one another will be of issue, and do i need a balun, Should the legs be cut for any particular part of each band,, Thank You for any input, i hope that this will be an efffective antenna, as well as a good build,

Mike Grace
 

nanZor

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my idea is to maybe build a center fed dipole, of twin lead, with 3 or 4 strips of twin lead, si it could be cut for 6 or 8 bands.......
I suggest starting out simpler with just a standard dipole, live with it for a time, and take notes before you start getting too complex - otherwise it would be hard to tell if your multi-twin-lead antenna is doing well.

The formula for a dipole is 468/f mhz = feet. Cut this value in half for each side of the dipole. Run the coax away perpendicularly for at least a few feet. You don't need a balun at this stage of the game.

Simply start like this: make a VHF vertical dipole out of say 18 inches of wire on each side. The length is NOT critical at this time. Live with that for awhile and take notes.

When done living with that, turn it into a UHF dipole with about 6 inches of wire on each side. Make notes again. If you are interested in 800mhz, make the dipole only 3 inches on each side.

These dipoles will work better on the bands they are cut for, but in many instances, reception may be satisfactory for a variety of reasons discussed elsewhere.

The point here is to give yourself a reference of knowing what a standard dipole is like, before going the complex route. Rapid prototyping with just painters tape wrapped around pvc to support the wires will cut down on a lot of material and time before you decide to go a more permanent route.
 

mikesjoint

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i have in the past built a handful of single band center fed dipoles, but had always wondered about the multi-band one i described. i just hadnt had anyplace to get opinion on the idea before building it, i have a couple of twin lead jpoles that i built for 2m packet radio a long time ago ( when i first earned my ticket). i had gotten away from the hobbies, but am coming back around to them. Thank you for the advice.

Mike Grace
KE4PJM
 

LtDoc

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Oklahoma
Maybe the simplest 'scanner' antenna is one that's 'cut' for the lowest band of use/interest. It won't be 'great' on the other bands, but it'd certainly be usable. If you optimize an antenna for one particular band you are also 'un-optomizing' it for other bands. Settle for the 'best' combination you can come up with.
When dealing with VHF/UHF height makes more difference than probably anything else. Higher means that the antenna can 'see' further, 'line of sight' and all that.
There's no single, all-band antenna that's always the best in every set of circumstances. There are just too many variables with things. The 'best' for you is the one that works best in your particular situation. Which one is that? Beats me! Try them all then you tell us, right?
- 'Doc
 
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