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tonyhemet
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Join Date: Oct 2014
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Scanner Antenna 25-1300 mhz Full Band

12/19/2017 9:18 PM

I went to an estate sale this past weekend and found a realistic pro 47 scanner # 20-142

Range 30-50 mhz, 144-174 mhz, 450-512 mhz . Made in Japan. Uses crystals. All the slots are used.

It's was only 2usd. I turned it on and I could hear local ems & pd. The antenna that came with it is a center loaded telescoping. On the back of the scanner are 2 antenna ports, they look like rca Jack's. One is for vhf , the other is uhf.

I thought if I like using this, I might get a newer radio and explore the hobby. Here are some questions : a. Would two separate antennas be required to use the uhf & the vhf or is there an adapter to plug into both using a common antenna. b. What type of adapters would I need to solder on to one side of rg58 ( to plug into the radio ) and the other to plug into a modern antenna.

I was looking at this equation : ( numbers from example ) to find for 2.4ghz. 2832 / f mhz = 2832/2400 = 2.4

My understanding is that the radials have to be the same length as the center conductor and by bending down the radials downward you will increase the ohm's, to create a dipole. (?) I saw a video on YouTube about this. It said if you increase the length of the radials you get lower frequencies. I understand that the radials provide reflection.

I went to scanmasters website and they have a full band outdoor antenna, ( 25-1300 mhz ) it has a center conductor and 45* radials as well as 90* horizontal radials. The 45's and the 90's are in the same vertical plane with each other. Is this a double dipole ? Is there an equation showing how to determine the length of the horizontals ? If I have to use two antennas, how to I determine height ( other than legal fcc rules ) and separation.

Thanks.
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SolarEagle
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#1

Re: Scanner antenna 25-1300 mhz full band

12/19/2017 9:30 PM

I have an app for that....

https://itunes.apple.com/us/app/scanner-radio-deluxe/id498405045?mt=8

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lyn
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Join Date: Oct 2008
Posts: 42355
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#2

Re: Scanner antenna 25-1300 mhz full band

12/19/2017 10:21 PM

I recommend ARRL :: Antennas :: ARRL Antenna Book (23rd Softcover Edition) if you really want to learn about antennas.

It is very interesting.

On a lark, I matched my patio umbrella to the CB (I know turn up your nose) transceiver one weekend. People came over to see that.

I never tried to use it for anything but a joke, but it worked well.

Radio Shack has everything you will need.

CQ
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phoenix911
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Hobbies - CNC - New Member Hobbies - DIY Welding - New Member Engineering Fields - Electromechanical Engineering - New Member

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#3

Re: Scanner antenna 25-1300 mhz full band

12/19/2017 10:34 PM

I always thought that fractals antennas were pretty cool,... history of it goes back to WWII.

I thought I heard that the early iphones, were recalled because of the poor reception and upgraded with a adhesive fractal antenna. But couldn’t find anything about it.

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Tom_Consulting
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Location: Maine, USA
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#4

Re: Scanner Antenna 25-1300 mhz Full Band

12/20/2017 2:20 PM

Since scanners can receive on multiple bands, you really want a Discone antenna. Google it.

Be aware that most police and a lot of EMS have switched to something called trunk systems and cannot be heard on those old scanners.

Since it's just a receiver, string a long wire and you'll probably get as good a result without much cost.

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RAMConsult
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Location: NYC metropolitan area.
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#5

Re: Scanner Antenna 25-1300 mhz Full Band

12/20/2017 9:05 PM

The dimensions of an antenna for receiving PS (Public Service) band broadcasts aren't as critical as those for transmission. The antenna should have omnidirectional characteristics because the transceivers tend to be in motion all the time, and broad bandwidth to accommodate the wide frequency range of transmission.

That said, one of the reasons for the two jacks is to allow for the use of highly directional antennas that are aimed at the repeaters that are usually used in sophisticated systems.

Another reason is that the receiver also receives on the 10, 6, 2M, and 70CM ham bands, and amateurs generally use highly tuned directional antennas for DX (long distance) reception, where "one size fits all" is less than optimal.

For your use, the center-loaded telescoping antenna should work fine; plus you can tweak it by adjusting its length. Enjoy!

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tonyhemet
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Join Date: Oct 2014
Location: Hemet, Land of milk and honey.
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#6
In reply to #5

Re: Scanner Antenna 25-1300 mhz Full Band

12/21/2017 12:54 AM

Thanks for the answer. I ordered a procomm disconne antenna from Amazon. For $58 it comes with 50' of rg cable, mount, and connector, I just need to get an rca adapter.

Now if I can just get the rest of my radios hooked up,,,
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lyn (1); phoenix911 (1); RAMConsult (1); SolarEagle (1); Tom_Consulting (1); tonyhemet (1)

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