Looking For a very simple Antenna Design for my Repeater (440)

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I have a UHF Repeater on 444.5/449.5 and i am running radios with approximately 15 watts at the duplexer, from a 25 watt radio (With losses). What is a good antenna i can Build that has some gain to bring up the power?

Also, i need to run a feed line from the repeater about 15 feet to the antenna, What is a low loss line i should use? (Im Thinking LDF450A)
 

zz0468

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I would second that suggestion. You received lots of good advice before, and didn't seem to take any of it. What's changed?
 
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its all great advice and all but its just i built a few types and nothing works for me. i get a range of about 5,000 feet at 15Watts
 

AA1LL

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coaxian colinear (CoCo) antenna

You may have been through this already, but the default repeater antenna would be a coaxial colinear array, first described by Harold Wheeler in 1956. He simply made, "A vertical antenna made of transposed sections of coaxial cable" which is the title of the paper. There is a step by step fabrication and assembly procedure at Omni-Gain Vertical Collinear Antenna by WA6SVT with good directions but poor graphics. The attached figure should give you some idea as to what it is. You could start out with 4 elements and get 6dBi gain with a pancake shaped pattern. I have never built one but it looks low materials risk and pretty foolproof. Let us know how you make out!
 

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davedaver1

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its all great advice and all but its just i built a few types and nothing works for me. i get a range of about 5,000 feet at 15Watts
You've been banging away at this since last May. You've been given several TONS of good information that you seem to ignore. Your question has been answered multiple times in the threads you've posted.

You are not going to be able to run the repeater you want, because you are not going about it properly. It's not about how many watts goes how many miles and how many dbs multiplies how many watts into ERPs. It's WAY more technical than that. You are NOT going to get there until you put all the pieces together in the proper order.

You need to either get a lot better at absorbing what is being said to you, or you need to get some help from some local hams to accomplish what it is that you are trying to do. It's like you want to drive a car, but you are trying to learn by going in reverse all the time. You're frustrating a lot of technical talent by driving them away from you too.

We love to have a young ham in the ranks, but you have to LISTEN to your teachers here. I admire that you are as young as you are and are attempting to do this, but you can't invent how to go about it, you need to follow the pretty much standard track to get a repeater up and running and maintained properly. It's been laid out to you multiple times in your threads. Go back and review them!

Good luck - I really hope you do succeed at making a good setup.
 

zz0468

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its all great advice and all but its just i built a few types and nothing works for me. i get a range of about 5,000 feet at 15Watts
Then build a quarter wave ground plane out of a PL-259 connector and use that as a reference antenna. If you only get 5000 feet out of that, then your feedline or transmitter is broken. If you get much better range with the ground plane than you do out of your home made "gain" antennas, then your antennas are the problem. It's also not unlikely that you're dealing with several problems. Be prepared to deal with that, too.

Once you have the system working good on a unity gain reference antenna, then you can begin to think about building a gain antenna. And btw, when you do that, you need to actually follow the directions, including recommended cable types. RG-58 is going to make a piss poor colinear antenna. It's a pretty lousy feedline at UHF as well.

We're not going to be able to fix your troubles by remote control. You're going to have to learn some basic trouble shooting skills. If you have questions, by all means, ask. If we give you suggestions of things to try, and we'd like to get your results, then you're going to have to do that if you expect people to help. We're not going to keep answering the same questions over and over if you give no indication that you're following advice, and there is no magic antenna that's going to solve all of your problems.

You have something broken there, and YOU are going to have to figure it out yourself. Good luck! =)
 
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OCO

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....and has the T/R pair you're using been coordinated with CSMA yet, or are you just plopping down where you think it's quiet?
 
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kb0nly

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I haven't read through all the other threads but i can agree with what they are saying here.

Why don't you just go out and spend the money on some good feedline and antenna?

Only fifteen feet of feedline? I wish i could say that about every install i do. Go with some 1/2" hardline, you can get a length of it off ebay with connectors for cheap, i saw some 20ft jumpers on there with N connectors installed for $30. Put $50-$60 into a decent fiberglass dual band base antenna, i would try the Jetstream JTB2, we have been using them with great success here for digipeaters and repeaters. All the antenna system problems solved for under $100.

If your range still sucks... You got a transmit or receive problem, could be a poorly tuned duplexer, a bad receiver, or a weak transmit even.. It could be ANYTHING. That's why everyone is saying work on it one piece at a time to troubleshoot it!
 

Skypilot007

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I am going to attempt to use RG174 as repeater jumper cables and some 1/2 inch LDF450A line to a homemade colinear antenna. ill see how it works... i will spend the money
 
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zz0468

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I am going to attempt to use RG174 as repeater jumper cables and some 1/2 inch LDF450A line to a homemade colinear antenna. ill see how it works... i will spend the money
No no no no no no and NO! No you're not. Jeeze... go back and re-read EVERYTHING that we've told you. Cripes... RG-174 is the WORST possible cable to use for a repeater. It's only supposed to carry low power RF a couple of inches INSIDE a radio. That's like, from one circuit board to another.

Use RG-214 for your jumpers. Don't have any? Get some. Don't use RG-58, either. It's a repeater, so it HAS to be double shielded cable or it'll never work right.

Use RG-214 or RG-213 for the collinear elements as the barest minimum. You need to cut the lengths to about 1/10 of an inch accuracy if you expect it to work. You can't half-*** these things or they just don't work. I still think you should get the repeater working properly with a quarter wave ground plane, THEN you can think about a gain antenna.

Now, for crying out loud, LISTEN to the advice people are giving you. :roll:
 
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kayn1n32008

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And only use silver connecters, NOTHING about repeaters is cheap, if you cut corners it WILL NOT work. One cheap nickle connecter will screw it up. If tyour going to use something of the diameter of RG-58 for jumpers it MUST be double shielded. Also stay away from double shielded coax that has copper braid/aluminium foil, dissimilar metals will have you chasing problems all over. Why does it feel like I'm repeating myself?

Yes RG-214 is expensive but again nothing about putting up a repeater is cheap.
 
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kb0nly

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RG-174 are you serious??? You might as well box up the repeater, send it to me, and i will make use of it.

There is nothing cheap about a repeater, i keep telling people that all the time, you want a good repeater with good range you have to spend some money!
 

rescue161

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If you're dead set on making a colinear antenna, your best bet is to use Quad-Shield RG6. You'll have to make sure you "gob" the solder onto the foil, 'cause if you don't, the dielectric starts to melt, which causes a short. Use a "melt the solder over the project" approach and it will drip onto the target area just fine. RG6 makes the best antennas for repeaters because it is QUAD shielded. No sense in wasting your time with dual sheiled coax or hard-line for that matter.

Also, make sure to use the "PL-259 to BNC" and then the "BNC to F" connectors. These type of connectors get the best transfer of signal. The old saying goes, "The more threads on the connectors, the better the signal." The "gold" plated ones are the best, which you can get at Radio Shack. For transmission line, RG-59 will probably net the best signal... The old stuff is the best, because it has more copper in it. You can probably find it in older houses.
 
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W2NJS

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To the OP. For Pete's sake, get a coax catalog sheet and read it. No one uses 174 for anything if they can avoid it. If you're concerned about RF loss on a 15-foot UHF coax run you need to go back to the catalog sheets and read about how tiny the loss would be at that length for a cable such as RG=8U. And one additional thing; you do not troubleshoot a system; you troubleshoot components of the system, one at a time. It's called "isolate and test."
 
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