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Author Topic: Base station commerical V-U antenna w/ ground plane adapter  (Read 351 times)

N2NJO

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Base station commerical V-U antenna w/ ground plane adapter
« on: March 09, 2021, 10:54:14 AM »

This purpose is NOT for 2m/440m. It's for 155-160 & 455-460 MHz

I have a Diamond X50NA base station antenna, but there is a problem with the female N connector. I don't see a way to remove/replace the fitting. Visually it appears ok, but even after changing fittings on the feedline (N) contact is not good. RLB scans vary and it wasn't acceptable to me. I have to assume the center receptacle is not forward enough (ruling out the name N connectors)

Anyway, I'm looking for a replacement and this combo seem to be the best choice (that I have found so far);
https://baofengtech.com/product/nagoya-nmo-200c/
https://baofengtech.com/product/nagoya-gpk-01/

I did find this review;
https://www.miklor.com/COM/Review_NMO200.php

My question was, what I don't like is the (what I call) outdated use of a SO239 instead of a 'N' connector. I realize at VHF, it's not a big deal,  UHF is another matter. I look around for other choices and I only found the Tram, a 4 element wimpy design (to say the least). The review did mention the ground plane being important.

Between the mini Tram and the Nagoya, input of both?
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KF5LJW

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Re: Base station commerical V-U antenna w/ ground plane adapter
« Reply #1 on: March 09, 2021, 01:26:25 PM »

I have to assume the center receptacle is not forward enough (ruling out the name N connectors)

Before you give up are you sure your N male on the feed line is not the problem? N, BNC, and TNC are very sensitive to cable  strip dimensions with very tight tolerances especially with respect to the center pin. On the commercial side we use a feller gauge to inspect the center pin placement. +0 / -1 mm tolerance. The center pin ideally should be flush with the Outer Contact Sleve, and no further than - 1 mm.

So before you give up check the center pin forward placement. If you find the point flattened, it was too long and possible pushed the female contact back on the antenna. You might get lucky and just find the feed line connector improperly terminated and an easy fix.   
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W1MOW

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Re: Base station commerical V-U antenna w/ ground plane adapter
« Reply #2 on: March 09, 2021, 01:36:13 PM »

Instead of going the route you described try one of Ed Fong's antennas. He offers a dual band antenna the DBJ-1. He will cut it to the commercial bands, and for $5.00 install an "N" connector. (Why you are so hyper about having an "N" when just about all UHF radios have some form of SO-239's?)

We have 3 of these in use for commercial/public safety use on mobile command posts & EOC's where the number of antennas are a concerned. These are not great, but much better solution than what you are proposing.

https://edsantennas.weebly.com/about.html

Gary W1MOW
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The fundamental cause of the trouble is that in the modern world the stupid are cocksure while the intelligent are full of doubt - Bertram Russell (1935)

So not much has changed in almost 90 years!

RADIOPHONE

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Re: Base station commerical V-U antenna w/ ground plane adapter
« Reply #3 on: March 09, 2021, 01:48:51 PM »

"It's for 155-160 & 455-460 MHz"


150-160 and    455-460.   Hmmmm.

Strange things are happening.

  ;D
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N2NJO

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Re: Base station commerical V-U antenna w/ ground plane adapter
« Reply #4 on: March 09, 2021, 09:10:27 PM »

I have to assume the center receptacle is not forward enough (ruling out the name N connectors)

Before you give up are you sure your N male on the feed line is not the problem? N, BNC, and TNC are very sensitive to cable  strip dimensions with very tight tolerances especially with respect to the center pin. On the commercial side we use a feller gauge to inspect the center pin placement. +0 / -1 mm tolerance. The center pin ideally should be flush with the Outer Contact Sleve, and no further than - 1 mm.
So before you give up check the center pin forward placement. If you find the point flattened, it was too long and possible pushed the female contact back on the antenna. You might get lucky and just find the feed line connector improperly terminated and an easy fix.   
I'm going to have to check the model number of that antenna, either it's the wrong model number I posted, or it's the wrong antenna. It's suppose to be the 'commercial' version of the 2m/70cm version that many other companies offer.

I find it hard to believe two N male connectors, both were bad. I substituted a 'discone' for the time being and I see no similar behavior.
What was happening was a fluctuation in the RLB  scan of the antenna. I could loosen, then tighten (by hand) the connector and the pattern would change somewhat.

I did pay special attention to both center pins, the males were not damaged, the points were not flattened.
« Last Edit: March 09, 2021, 09:17:55 PM by N2NJO »
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N2NJO

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Re: Base station commerical V-U antenna w/ ground plane adapter
« Reply #5 on: March 09, 2021, 09:17:03 PM »

Instead of going the route you described try one of Ed Fong's antennas. He offers a dual band antenna the DBJ-1. He will cut it to the commercial bands, and for $5.00 install an "N" connector. (Why you are so hyper about having an "N" when just about all UHF radios have some form of SO-239's?)
I did see what he jas to offer. Two problems; his VHF band is too low and the UHF is too high in frequency.
As to the preference to N connectors, I feel the same way about old school RG58 & RG8 cables. I have replaced most of those to cable with RFC240 & RFC400 from Shireen. Much less loss.
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W1MOW

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Re: Base station commerical V-U antenna w/ ground plane adapter
« Reply #6 on: March 10, 2021, 09:21:13 AM »

Instead of going the route you described try one of Ed Fong's antennas. He offers a dual band antenna the DBJ-1. He will cut it to the commercial bands, and for $5.00 install an "N" connector. (Why you are so hyper about having an "N" when just about all UHF radios have some form of SO-239's?)
I did see what he jas to offer. Two problems; his VHF band is too low and the UHF is too high in frequency.
As to the preference to N connectors, I feel the same way about old school RG58 & RG8 cables. I have replaced most of those to cable with RFC240 & RFC400 from Shireen. Much less loss.

If you contact him, he will cut them to the freqs. that you request. Not that it will matter that much.
« Last Edit: March 10, 2021, 09:38:56 AM by W1MOW »
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The fundamental cause of the trouble is that in the modern world the stupid are cocksure while the intelligent are full of doubt - Bertram Russell (1935)

So not much has changed in almost 90 years!

N2NJO

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Re: Base station commerical V-U antenna w/ ground plane adapter
« Reply #7 on: March 10, 2021, 10:16:21 AM »

Ok, I'll give it a shot.
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N2NJO

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Re: Base station commerical V-U antenna w/ ground plane adapter
« Reply #8 on: March 18, 2021, 03:34:44 PM »

I contacted him and he replied it was a no go, so that killed that.
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KM1H

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Re: Base station commerical V-U antenna w/ ground plane adapter
« Reply #9 on: March 19, 2021, 06:50:06 PM »

A thumb over the N male was the calibration for the center conductor. I learned that from professional 2 way and tower guys in the early 70's. ;D  ::)

Carl
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N2NJO

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Re: Base station commerical V-U antenna w/ ground plane adapter
« Reply #10 on: March 20, 2021, 12:32:46 AM »

Confused about the thumb part and calibration.  ???
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KM1H

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Re: Base station commerical V-U antenna w/ ground plane adapter
« Reply #11 on: March 22, 2021, 06:06:22 PM »

Quote
"It's for 155-160 & 455-460 MHz"

On standard 450-460 UHF Low Band commercial frequencies I cant remember ever seeing a true UHF version (not one for a ham rigs with a mod) with a SO-239.

Around here commercial UHF has been extended to 475 MHz several years ago. I had a few repeaters up on the 450-460 lower frequencies but due to the hilltop location and tall tower it was crunching other stations even down on Cape Cod and up in Maine and some VT. The FCC authorized the move as low power broadcast TV, translators, and school stations were being relocated. The antenna was an 8 bay of folded dipoles at ~ 160' level.

Carl
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