Using 800mhz mobile antenna as base

kmartin

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I just came across a NMO to N base station converter that i picked found at a pawn shop and i want to mount an 800mhz mobile whip to this for a trunk system in my area. The antenna is a 3 db gain 855 MHz whip 13 inches with a coil towards the bottom and an NMO mount, however the base station converter didn't come with radials..no problem i can make some out of materials i have. My question is how long would i have to make my radials For this 13 inch whip ?
 

trentbob

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You could use a pie pan, cookie sheet, filing cabinet also. Because you got it in a pawn shop and it has the pigtail in it it reminds me of the old mobile installed conventional 800 megahertz phone antennas. I would probably rewire it with coax that is a little less lossy even though it's going to be probably less than 17 or 18 feet so it probably doesn't matter. I'm just a little compulsive. :)
 

trentbob

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I am assuming you were going to use this inside?
 

kmartin

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No. Outside. This adapter has a place to mount on a pole using u bolts or stainless steel hose clamps. It has 4 holes for radials and set screws to secure the radials so they just slide in and secure when tightening the screws. I have strong thin stainless steel wire that will fit into the holes Trentbob. So i was just wondering how long to cut these radials
 

kmartin

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I was thinking 31/2 to 4 inches but with the antenna length being 13 inches i was wondering if the radials would need to be longer and how longer to be effective. It will be 20 ft and don't scold me for the cable i am using but using RG 6 quad shield cable
 

trentbob

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Haha okay, if you are just listening RG6 would be fine as long as you're not going too long. It is 800 megahertz so I'd like something like lmr400 for 800 MHz.

As far as the length of the the radials, I was going to suggest 3 1/2 to 4 inches originally and that is nothing but a flat-out guess. It's somewhat odd as I am sure this antenna is the original analog cell phone antenna that was used in mobile applications back in the late 80s and 90s. 13 inch long with the pigtail.

I don't know how high you're going and how easy it will be to bring down the antenna and make adjustments so a good idea might be is keep it inside for now maybe on a broom handle using Gorilla Tape and just experiment. This is kind of uncharted territory for me but it sounds like a great project.

When you find an improvement and the best results with the proper length then you can go ahead and permanently mount it.
 

kmartin

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Sounds good Trentbob I'll go with that and experiment ! It's just a project I'm trying just for kicks. My main base station set up will remain where it is
 

trentbob

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Yep, good luck with it and have fun!... Bob.
 

trentbob

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Yep, that's why I guessed 3 1/2 to 4 in... I guess you should go with 3in. to 3 1/2 in. then kmartin, thanks Chief... Bob.
 
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