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Boxcar
| | Posted on Monday, February 24, 2003 - 10:24 pm: | 
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Okay, let's have it. Gimme some good antenna's to use for scanner use and possibly some web sites. I want to optimize my scanner height too!!! |
bruce
| | Posted on Tuesday, February 25, 2003 - 4:37 am: |
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boxcar THE BEST antenna for a scanner if you want wide range of frequencys is a discone. NOW if you want trunking only and are willing to spend some money look for a gain 800 meg vert and use a mast mounted preamp. 99% of the time the discone will work fine. Want to built one ??? try a J-Pole cut for the frequency you want to hear! |
de
| | Posted on Tuesday, February 25, 2003 - 7:07 am: |
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If you have an old VHF/UHF/FM TV antenna why not try using it as a scanner directional antenna. Put the antenna in vertical rather than a horozontal configuration and see what happens. And you should be able to get some directivity in your receive as well.
For a good omni, broad band receiving antenna I suggest you plug in the words "Discone Antenna" on your browser. You should find many who sell this antenna. Not much gain but omnidirectinal, very broad banded and relatively small in size. |
Tech833
| | Posted on Tuesday, February 25, 2003 - 11:48 am: |
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Do this: Pretend you want to transmit as far as possible on your frequency (or frequencies) of interest. What antenna would you use then?
Remember, the transmit and receive capabilities of two-way antennas are nearly exactly the same. I have seen stacked long boom yagis on 60 foot towers with rotors fed by Heliax cable, all for a scanner. It depends on what you want to hear.
As for all-purpose, all frequency listening, the discone is the best bet. I knew an engineer who used a discone as his sole two-way base station antenna for VHF/UHF and 800 business band. It was about 30 feet above his roof and worked very well. The radiation pattern of a discone is almost identical to a 1/4 wave ground plane vertical. He hit repeaters as well as others in his town with fiberglass base antennas on their homes. |
Wyatt_Earp
| | Posted on Tuesday, February 25, 2003 - 1:24 pm: |
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But remember, by using the discone, you do not have much gain. If you want to pull in the VHF and UHF freq's, try the little $20 antenna at Radio Shack. |
Bulldog
| | Posted on Tuesday, February 25, 2003 - 4:07 pm: |
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How about making a 2 meter j-pole? Costs around $5.00 to build. I built one for my scanners and it just about covers 140 to 440 fairly well. Or if you have a certain freq to listen to, cut one for that area of the band. |
Boxcar
| | Posted on Tuesday, February 25, 2003 - 5:09 pm: |
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Thanks guys. I might try the discone anyway. I've heard a lot of good things about them. I did have a buddy that had one of those from radio shack and his worked great. I believe it was around 429.99 or $39.99 or something like that for that discone antenna. Does the coax make much difference? I'm using up what left of RGmini 8 that I have left in stock. Thanks again guys!!! |
Tech833
| | Posted on Tuesday, February 25, 2003 - 6:06 pm: |
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For UHF and above, your coax is almost more important than your antenna. The Mini-8 will work O.K. for an extremely short run. For anything longer than 20 feet, invest in some LMR-400 or better.
The hams will tell you otherwise, but those of us in the profession with the right test gear know better. We usually just snicker at the hams struggling to make their junk work most of the time. |
bruce
| | Posted on Tuesday, February 25, 2003 - 7:13 pm: |
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HEY 833 I RESEMBLE THAT HAM REMARK! ..... he he he |
DeadlyEyes
| | Posted on Tuesday, February 25, 2003 - 7:18 pm: |
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Re 833,
Tis true what you stated. Hmmmm, perhaps if it is practical the use of Ladder Line. Since he is not considering transmitting, SWR is not a factor that needs considering. And 450 ohm Ladder Line does have a very low loss factor. |
Boxcar
| | Posted on Tuesday, February 25, 2003 - 8:01 pm: |
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I did a little homework on this LMR coax. Frequency loss at 100 feet at 2400MHZ is 6.65 db. Not too bad. What's the difference though between the center stranded wire versus the solid wire? Specs show here that it does fluxuate a little for the same 400 wire. Sounds good though. What's my mini 8 coax rated at for loss per feet when using this coax for scanner use?
Thanks Tech833 |
CM 3885
| | Posted on Tuesday, February 25, 2003 - 9:04 pm: |
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Just use regular TV coax. I use it and have no problems LMR 400 and heliax are wayyyyyyyyyyyyyyyyyyyyyyyyyyy overkill for a lowly old scanner antenna..... LOL> |
bruce
| | Posted on Tuesday, February 25, 2003 - 10:01 pm: |
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use 450 ladder line DARE to be diffrent |
Tech833
| | Posted on Tuesday, February 25, 2003 - 11:38 pm: |
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Overkill for a scanner antenna? How so? ANY antenna installation that you are expecting performance from is worth it. Remember, your coax IS part of your antenna system.
The 'secret' to the LMR cable is not just the center conductor, but it is also double shielded (if that is a word). It is the next step under Heliax (hams call it hardline).
Almost any piece of wire will receive at 450 MHz. and up. Getting that precious small signal to your receiver is the trick to performance.
Case in point- See http://www.popularwireless.com/gmrshomeantenna.html
Here's the Reader's Digest version of that article:
The user was not receiving well on 462 MHz. using a gain antenna and RG-8 cable. In fact, the user could not hit many repeaters out of his local area either. The user replaced the cable with 1/2 inch Heliax and suddenly he could hear things full quieting that he could not pick up at all previously.
Some quotes: "My original installation consisted of an Antenna Specialists gain antenna atop a twenty foot roof-mounted pole, fed with RG-8 coaxial cable. The seventy feet of RG-8 cable had so much signal loss on GMRS UHF frequencies that virtually no received signals reached my receiver and all transmitted energy was used up as heat. RG-8 has about 4.5 dB loss per 100 feet at UHF. "
Then: "... a seventy-foot section of used one-half-inch solid-copper-shield coaxial cable also known as Heliax™. The slang term used to describe it is "hard line." The signal loss from antenna to radio along Heliax™ cable at this length at 460 MHz is less than 1 dB. " "My signal strength into the three local repeaters I use increased significantly. Right away I found that usable direct communication between radios on the repeater outputs (talk around) increased by several miles. My wife and I can use direct communication around town without burdening the rest of the world with our shopping trips. Why use a repeater at 3800 feet that serves most of Northern California if you don't have to. Now our base to mobile communication is incredibly reliable virtually anywhere we need it. This includes base to hand-held radio communication. Prior to installing our antenna the right way we had some difficulty with hand-held direct communication. Now if we can hear it we can pretty much talk to it."
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