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Author Topic: Seeking 220 MHz Repeater Antenna Advice  (Read 318 times)

N4DBM

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Seeking 220 MHz Repeater Antenna Advice
« on: December 31, 2019, 06:54:28 PM »

Hello Group,
I'd like some input in your experiences with 220 MHz antennas in duplex service on FM repeaters. 

I have a Bridgecom BCR-220 repeater, Wacom duplexer.  There's 18 watts out of the duplexer and good RX sensitivity with no desense into a dummy load.

The tower is 150 feet with good 7/8 to the very top.  The antenna will be top-mounted, above everything else.  I live in south-eastern NC where hurricane force winds and mid-summer lightning strikes are prevalent.  The tower is grounded very well and bonded to everything else. 

As with most any other ham repeater, I'm looking for best over-all coverage possible, but reliability is king.  Here are my options.

1.  PD-200 Stationmaster.  It's 40 years old but taken apart the joints look great and it duplexes well with no "crackles" while on the ground.  It's over 20 feet long and by calculations, has over 6 dBd gain.

2.  Hy-Gain V3R antenna.  It's actually a Hy-Gain V2R cut down to 220 specs.  The coil covers from 108-225 MHz so the physical trimming of the pieces worked well.  The match is excellent and the gain is spec at 3 dBd.

3.  Hustler G7-220 - I don't have one, but welcome your thoughts on this.

4.  Decibel DB-201-JJ - this is a folded monopole ground plane.  Naturally it's a zero-dB antenna but it's probably the most robust of everything mentioned above.

I don't have the money for a new Commander PD-220, Telewave, Sinclair, or Comprod variety.  I wouldn't dream of using a Comet or Diamond fiberglass noodle stick out the top of a tower, so I didn't include those either.

What are your thoughts on the four mentioned above, and why? 

Thanks for your input.
N4DBM.


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N2AYM

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Re: Seeking 220 MHz Repeater Antenna Advice
« Reply #1 on: January 01, 2020, 07:43:33 AM »

I have been using a home brew 220mhz 4 bay dipole area for about 15 years
up about 165 feet and am about 5 or 10 miles away from the NJ coast
so i have to believe i have been a bit lucky. In that time it has developed
a slight swr issue which could be either a pigtail connector/cable issue.
Even with the slight swr issue it still radiates well. It is constructed very
much like the uhf models below.

http://wiscointl.com/maxrad/old/LandMobile/300-512MHz/mda4502.htm
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WA8NVW

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Re: Seeking 220 MHz Repeater Antenna Advice
« Reply #2 on: January 02, 2020, 06:32:46 PM »

Seriously consider mounting your PD200 noodlestick antenna slightly lower, so that the top is at least two feet below the tip of the lightning rod at the top of the structure. The result will be about 3 dB of directional offset, but you get all the proven performance of a 50 year old P-D design.
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KE6JZ

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Re: Seeking 220 MHz Repeater Antenna Advice
« Reply #3 on: January 12, 2020, 07:02:01 AM »

Seriously consider mounting your PD200 noodlestick antenna slightly lower, so that the top is at least two feet below the tip of the lightning rod at the top of the structure. The result will be about 3 dB of directional offset, but you get all the proven performance of a 50 year old P-D design.

Ditto the above. This is what we use and has been reliable for 35+ years. We also have a side support on this antenna about 5 feet down from the top to keep it stable during windy weather. Been on a 6000 foot mountain top and really works well. If ever need to replace, may consider something from Telewave.

73,
KE6JZ
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KB8VUL

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Re: Seeking 220 MHz Repeater Antenna Advice
« Reply #4 on: January 13, 2020, 08:02:47 PM »

Station Master is a really good antenna, and would serve you well, but they really don't like lightning much.

The comment on the 4 bay dipole array is a good one, and what I was also thinking.   Finding a 220 4 bay is gonna be impossible on the used market unless there happened to be a lot of 220 commercial in your area.  In my area there was none.  In fact, in over 10 years of being a commercial radio tech, I have only seen one 220 commercial system and it was sitting unhooked in the shop I work for now when I got there  It ended up in a dumpster.
There is a ton of VHF however.  And Andrew / Commscope and Decibel both made 220 4 bay antenna's.
I would try locating some specific design information on them, and then locate a 4 bay high cut VHF 224 and then modify it to operate on 220.

All that being said, I know you said you want to get the best performance possible out of the system. But you if you haven't really considered what that is, it's time to do so.
While I am writing this I have little idea where you are.  So I will say that you need to consider what coverage you want.  Do you want it to talk to the horizon at the cost of not working well in the town that you live?  I am guessing not.  So what is the overall height of the tower.  Meaning the HAAT or height above average terrain? Is it on a big hill right outside of town?  Are there towns on both sides of the hill it's on?  Lots of questions I know. But there are ways of creating downtilt in an antenna electrically that will drive the signal down the side of the hill and into the town, creating great coverage in the town, but at the expense of the coverage into the next town down the road. 

The reason I bring this up is I fight this with my tower. 
Grab a map, and find Johnstown Ohio.  Just east of there is my 240 foot tower.  Sitting on the highest point in the county.  Once you find it, find YOungstown Ohio.  It's Northeast, on the PA / OH border.  I talk into the repeaters there, from antenna's on the ROOF of the building.  That's 220 feet below the top of the tower.  so you can see what I am getting at.  I put a db420 on the top of the tower and talk OVER Johnstown.  I actually have a better signal in Columbus 30 miles away than I do 4 miles away in Johnstown.  The reason is how an omni directional antenna has gain.  The gain of an omni is created by flattening and concentrating the signal in a radial beam pattern. 

So. review the pattern on the antenna that you select or design.  ANd make sure it's a good fit for what you are trying to accomplish.
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WB8VLC

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Re: Seeking 220 MHz Repeater Antenna Advice
« Reply #5 on: January 15, 2020, 11:03:53 AM »

I guess I was lucky when around 15 years ago I came across a 220MHz DB-222 for 75 bucks.

All it needed was a new mounting clamp on the upper folded dipole and it has been in operation for the past 15years without any issues.

But you are correct, they are 1000 times rarer than a politician with integrity and 15 years ago was the first and last time I saw one for sale.


 
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WB5ITT

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Re: Seeking 220 MHz Repeater Antenna Advice
« Reply #6 on: January 28, 2020, 07:28:25 AM »

Top mounted, I go with the folded dipole (DB224, AFM Cushcraft or similar)...I have used a G7-220 on tower top....lost two in two years due to lightning.....last time, mounted a 20ft mast as a lightning rod 5 ft away....never lost a G7 after that...The Celwave versions on top of tower, I would avoid....eventually, you'll get the crackles...and its a PITA to climb and change it...the folded dipole versions is best tower top.

Chris
WB5ITT
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