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IS A DIPOLE ANTENNA GOOD FOR SHORTWAVE/SCANNERS???

a place to talk about and ask for help for them shortwave radio's & Scanners

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Eagleman
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IS A DIPOLE ANTENNA GOOD FOR SHORTWAVE/SCANNERS???

Post by Eagleman » Tuesday, 01 December 2009, 17:47 PM

Is there a certain length of wire to use best for a shortwave or scanner antenna??? I've heard a 102 feet wire is excellent for this, Whats your opinion??? Dave :bigsmurf:


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Re: IS A DIPOLE ANTENNA GOOD FOR SHORTWAVE/SCANNERS???

Post by drdx » Tuesday, 01 December 2009, 17:54 PM

The length of the antenna depends on the frequency. For a scanner, a very short antenna is needed, depending on the band, while short wave listening needs much more length. The dipole formula is 468 divided by the frequency. On cb, it is about 17 feet. For lower shortwave bands much longer. Let's say you want an antenna for 7 mhz. Take the 468 and divide that by 7, and you'll have your total dipole length. Cut that in half and that is the length of each leg, one connected to coax center, one to shield. Or, just see it as 234 divided by 7 for each side. You can also use one antenna for several bands. For best reception you'd want an antenna tuner or preselector to make it work better, or just use it as is. Loops are also nice shortwave antennas. Look up Loop Skywire sometime when you're bored.

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Re: IS A DIPOLE ANTENNA GOOD FOR SHORTWAVE/SCANNERS???

Post by 'Doc » Tuesday, 01 December 2009, 19:39 PM

A dipole, or some other horizontally polarized antenna can work fine for a scanner antenna. Figuring what polarization is typically used for whatever band you want to listen to is a pretty good idea, and matching that polarization is a good idea too.
Having an antenna resonant (or sort of close to resonant) for whatever you intend listening to is certainly nice. It's not absolutely necessary, it's just nice. Using an antenna longer than necessary is a fairly good way of doing it too. Receivers are not as 'picky' about resonant antennas as transmitters. Not to mention that having a resonant (or close) length of antenna for every band is going to get sort of 'porcupine-ish' and big pretty quick.
Since most scanners cover VHF/UHF a lot, antenna height is as important, if not more so, than antenna length.
There's a huge number of "if's" in all this so getting close is usually good enough. If there are particular frequencies that you want to listen to, optimizing the antenna system for those ain't a bad idea, sort of let the 'other's fend for themselves, sort of. Nothing says you can't change things.
- 'Doc

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Re: IS A DIPOLE ANTENNA GOOD FOR SHORTWAVE/SCANNERS???

Post by Eagleman » Tuesday, 01 December 2009, 21:31 PM

'Doc wrote:A dipole, or some other horizontally polarized antenna can work fine for a scanner antenna. Figuring what polarization is typically used for whatever band you want to listen to is a pretty good idea, and matching that polarization is a good idea too.
Having an antenna resonant (or sort of close to resonant) for whatever you intend listening to is certainly nice. It's not absolutely necessary, it's just nice. Using an antenna longer than necessary is a fairly good way of doing it too. Receivers are not as 'picky' about resonant antennas as transmitters. Not to mention that having a resonant (or close) length of antenna for every band is going to get sort of 'porcupine-ish' and big pretty quick.
Since most scanners cover VHF/UHF a lot, antenna height is as important, if not more so, than antenna length.
There's a huge number of "if's" in all this so getting close is usually good enough. If there are particular frequencies that you want to listen to, optimizing the antenna system for those ain't a bad idea, sort of let the 'other's fend for themselves, sort of. Nothing says you can't change things.
- 'Doc
THANKS DOC FOR THE REPLY & IMFO. GREATLY APPRECIATED..... DAVE :bigsmurf:

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Re: IS A DIPOLE ANTENNA GOOD FOR SHORTWAVE/SCANNERS???

Post by barhopper 1 » Sunday, 13 February 2011, 19:00 PM

Thats going to be one of my summer time projects string up 75-100ft. longwire from the house to one of the trees in backyard gotta wait till the snow melts and I hope its real soon!!!!!!!!!!!!!! :drunken:


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Re: IS A DIPOLE ANTENNA GOOD FOR SHORTWAVE/SCANNERS???

Post by Bad Clams » Friday, 18 February 2011, 19:39 PM

I made a J pole antenna from an artical I found in an old Popular Electronics rag. I dont have it in front of me but it's just a section of that old stereo antenna wire probally 15' maby soldered to a piece of RG-58. it runs in the range of 140.00 mhz to 160.00, it works really well considering I can pick up baby monitors on it from time to time and back in the day the old cordless phones. way better than the duckie antenna by far.
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Re: IS A DIPOLE ANTENNA GOOD FOR SHORTWAVE/SCANNERS???

Post by genesbro » Sunday, 01 May 2011, 16:13 PM

I have a vertical dipole for CB and when I don't have the base hooked up to it I put it on the scanner and it works great. I can pick up mobile and base signals from around 50 miles away or more, plus I can get all kinds of aircraft stuff. I have it mounted with the feed point at 35 feet with vertical polarization.
Radio, still the most fun way to communicate!




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