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 Post subject: Length of wire antennas
PostPosted: May Sun 05, 2019 5:43 am 
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Joined: Jul Sat 09, 2011 7:49 pm
Posts: 44
Location: Santa Cruz,ca
Hello. Have a question regarding wire antennas for general coverage. Was wondering if lets say I have an antenna of fifty feet on each leg, and, you attach 3 lengths of ten feet each just hanging down from each half of the dipole spaced equally will it become an eighty foot wire antenna on that half of the antenna electrically? Am thinking of doing this just for fun! Any ideas??? Thanks.
Jerry


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 Post subject: Re: Length of wire antennas
PostPosted: May Sun 05, 2019 5:59 am 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: SoCal, 91387
Why not just do it, and post your results?

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 Post subject: Re: Length of wire antennas
PostPosted: May Sun 05, 2019 9:57 am 
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Location: Annapolis, MD
Over-simplifying a bit, a basic "long-wire" antenna produces a signal in proportion to its length. Adding extra wire that is not in the same direction might not do anything at all.
As suggested, sometimes you have to just try it and see....

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 Post subject: Re: Length of wire antennas
PostPosted: May Sun 05, 2019 10:41 am 
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Joined: Mar Tue 27, 2012 1:24 pm
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It might affect your signal strengths, because more wire can equal more signal, but it probably won't change the electrical length of the antenna.

But it's been a long since I studied the Amateur Radio Antenna Handbook, so I could be mistaken.


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 Post subject: Re: Length of wire antennas
PostPosted: May Sun 05, 2019 10:48 am 
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Renton481 wrote:
It might affect your signal strengths, because more wire can equal more signal, but it probably won't change the electrical length of the antenna.

What is the significance of changing the electrical length if it does not change the signal?

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 Post subject: Re: Length of wire antennas
PostPosted: May Sun 05, 2019 9:18 pm 
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Joined: May Sat 12, 2012 1:33 pm
Posts: 1690
Location: Rochester, NY.
A copy of the ARRL antenna handbook may be available at your local public library, but you can't beat experimentation. I have an inverted-L longwire, partly because of horizontal space limitations and partly because of the desire for some omni-directional reception.
Vertical and/or horizontal polarization and lead direction/orientation may be an important consideration for what you are trying to listen to. It may also help reduce any bothersome ambient RFI noise.
http://nationalradioclub.org/catalog/books/books.html


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 Post subject: Re: Length of wire antennas
PostPosted: May Mon 06, 2019 1:09 pm 
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Joined: Mar Tue 27, 2012 1:24 pm
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pixellany wrote:
Renton481 wrote:
It might affect your signal strengths, because more wire can equal more signal, but it probably won't change the electrical length of the antenna.

What is the significance of changing the electrical length if it does not change the signal?


You can get tons of signal, but an antenna -- no matter the length -- is generally optimized at its electrical length. This applies more for transmitting than receiving, but it can affect reception if you are aiming at hearing a specific band more than others.

A 31 meter wire will bring in tons of signal on the MW broadcast band, for example, but it is optimized for the 31 meter SW band.

You can have a super long antenna and it will be more efficient at longer wavelengths (lower frequencies), but it will still slam most radios on SW with plenty of signal.

So, your adding wire to your antenna might have added some signal to your radio, but the antenna is tuned for the actual length of it, which seems to be 100 feet, which would make it optimal at 30 meters, but it will still work on other frequencies for receiving.


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 Post subject: Re: Length of wire antennas
PostPosted: May Tue 07, 2019 1:55 am 
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Joined: Jan Fri 27, 2017 8:41 pm
Posts: 110
Location: Springwater, NY
Fayal7 wrote:
Am thinking of doing this just for fun! Any ideas??? Thanks. Jerry


To add to your fun, you can generate a model for your antenna using this free tool:

https://www.qsl.net/4nec2/

The software is free, powerful and provides accurate results.


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 Post subject: Re: Length of wire antennas
PostPosted: May Tue 07, 2019 3:09 pm 
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A random wire antenna will produce random results. Too many variables to give you an honest answer.

As the wire length is changed, the antenna "pattern" will also change. The antenna will have more gain in certain directions and less in others. All of this depends on the antenna wavelength at the frequency you are listening too.

If you just connect the random wire antenna directly to the receiver antenna jack it will probably do fine for casual listening across the BCB and SW bands.

if you add any coax or balanced line the feedline can introduce significant losses if the impedance at the antenna feedpoint is too high at a particular frequency.

Put up the antenna, and see how well it works.

Pete

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 Post subject: Re: Length of wire antennas
PostPosted: May Wed 08, 2019 6:01 pm 
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If you had the wires hanging off the end of the wire it would add to the electrical length. Just attaching random lengths at random places to a random antenna does not accomplish anything. Basically will result in unpredictable random results. If you attach shorter wires to the termination point(receiver end) then it can act like a multi frequency antenna. Fifty feet is a bit long for the shorter shortwave lengths but with the sunspots being absent, your shortwave listening results above about 15 MHz will be virtually nil these days anyway. So your antenna ought to be be something that will function from 3-15 MHz these days. The frequencies below about 7 best at night, the higher ones are more daylight active but that is variable and some signals up to 12 or so ought to be heard at night. You could maybe add a wire about 16-20 feet long at the origin point of your 50 foot wire and that would maybe enhance the reception up at the top of that range.

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