Make an antenna with RG-58 for a Repeater

[zz0468]

So what should I do? I am looking to get a high gain antenna and the LDF4-50A feedline and hook it into my 25 watt repeater. Then with high gain it will help to improve siginal and ERP?

You started the thread asking about building an antenna out of RG-58. You can go here:

Omni-Gain Vertical Collinear Antenna by WA6SVT

and here:

Build A 9dB, 70cm Collinear Antenna

The parent web page for both of those articles is here:

Antenna Systems Information from www.repeater-builder.com

Read those to answer your original question.

Also, you need to learn about Effective Radiated Power (ERP), coax loss, duplexers, and understand how all the gains and losses add up and equate to ERP. And then you have to understand how ERP translates to effective range.

If you're looking to cover just a couple of miles, a few watts would be more than enough, provided you're not losing it all in a lousy antenna system.

 

[centuryvrproductions]

You started the thread asking about building an antenna out of RG-58. You can go here:

Omni-Gain Vertical Collinear Antenna by WA6SVT

and here:

Build A 9dB, 70cm Collinear Antenna

The parent web page for both of those articles is here:

Antenna Systems Information from www.repeater-builder.com

Read those to answer your original question.

Also, you need to learn about Effective Radiated Power (ERP), coax loss, duplexers, and understand how all the gains and losses add up and equate to ERP. And then you have to understand how ERP translates to effective range.

If you're looking to cover just a couple of miles, a few watts would be more than enough, provided you're not losing it all in a lousy antenna system.

Yes I am not looking to have a good repeater, I know I need to actually learn about all of this. This is sort of a project. and i want it to work for a few miles or so.
The reason I went from RG-58 to this discution is that I learned a lot from the last posts... But any suggestions for my setup using 25 watts and LDF4-50A feed line? I was looking for a 5-9db gain antenna or something like that

 

[zz0468]

Yes I am not looking to have a good repeater

Then you should stop right there.

If your repeater is operating poorly, is heard over a wide area because you're running far too much power, is contributing to intermod, or otherwise causing problems because it's NOT a good repeater, you stand to make yourself a pariah within your local ham community. As a new ham, that's NOT how to start out. Once you attain that status among other nearby hams, it can take years to outgrow it.

I know I need to actually learn about all of this. This is sort of a project. and i want it to work for a few miles or so.

Then go back to your original plan of running just a few watts. That's PLENTY enough power to experiment with, although even that has potential to bother other systems.

The reason I went from RG-58 to this discution is that I learned a lot from the last posts... But any suggestions for my setup using 25 watts and LDF4-50A feed line? I was looking for a 5-9db gain antenna or something like that

Yes, I have a suggestion. Go to the Repeater Builder web site and read EVERYTHING there. Once you have digested all the pertinent articles, THEN turn on your soldering iron and start building.

 

[centuryvrproductions]

Do you think if I were to tune my Maxtrac down to say like 2 or 5 watts, will it cover a few miles if i use the LDF4-50A feedline and a High gain antenna?

 

[zz0468]

Do you think if I were to tune my Maxtrac down to say like 2 or 5 watts, will it cover a few miles if i use the LDF4-50A feedline and a High gain antenna?

The answer to that question is subject to more variables than we have to work with. You should run it at as low a power level as you can, just to be courteous to the people who are running properly constructed, coordinated repeaters. You really don't want to piss those people off - trust me.

There is a lot more to range than just power levels. Is your house on a hill? In a canyon? At the bottom of a 200' sinkhole?

I'm aware of repeaters that have run just a few watts and could be used 50 miles away, because they're at a high elevation.

You could run some quick easy tests with your friends by talking to them simplex and see how far out they get before they run out of range.

 

[kayn1n32008]

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250 watts...wtf? I dont know of any commercial or ham repeaters in our county with anywhere near that power. You don't need that kind of power.

If you go that route you absolutely will not be able to skimp on anything. It will need to be top notch components from end to end.

I never said that. My comment was about ERP. 36w x 9db gain = 288w ERP. I was showing our young ham what the difference between RG-58 and low loss hardline.

 

[kayn1n32008]

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ERP: power times gain = ERP value into an isotropic radiator

 

[jim202]

Let me jump in here and make a comment about LMR cable. Many people use it for receiving and maybe transmitting on a base radio.

The big no no for the LMR cable is the use of it in duplex operation. That means repeater use. The double shield made up of the copper braid and the aluminum foil will cause problems and desense over time. It absorbs moisture over time that causes the intermod noise source of the problems. Those that have installed this type of cable for their repeaters have ended up replacing it with hard line and the problems with the noise go away.

Just thought I would throw this out so you don't end up having to purchase your feed line twice.

 

[prcguy]

I had a 5w UHF repeater with a 10dBD gain antenna on a two story building at sea level and it saturated anything and everything for a few miles around with handhelds and got out to about 35mi in some directions to 25w mobiles.That repeater had about 25ft of 1/2" hardline and everything in the system was peaked to perfection.

I also had a similar repeater at my current location with an elevation of around 350ft and could get into it with handhelds from about 100mi away in one direction.You will not get that kind of range cobbling things together and using RG-58 cable.
prcguy

Do you think if I were to tune my Maxtrac down to say like 2 or 5 watts, will it cover a few miles if i use the LDF4-50A feedline and a High gain antenna?

 

[zz0468]

I never said that. My comment was about ERP. 36w x 9db gain = 288w ERP. I was showing our young ham what the difference between RG-58 and low loss hardline.

ERP: power times gain = ERP value into an isotropic radiator

Right answer, but the way you're showing it could be misleading.

ERP is essentially adding up all the gains and losses. "power times gain" is correct, but in the case of 9db gain, that's a power gain of 8. Confused yet?

One way to calculate ERP is to convert the power out value to Dbm. 36 watts is about 45.5 Dbm. Now add the 9 db gain. that's 54.4 DBm. Convert to watts, and you get about 288 watts. In reality, you would also subtract the cable loss. so, in example, 45.5 Dbm transmitter power out minus, say, 3 db loss on the feedline, so you have 51.4 Dbm ERP. That translates to about 140 watts.

In other words, convert all values to Db. Add and subtract the Db gains and losses, then reconvert back to watts.

 

[zz0468]

Let me jump in here and make a comment about LMR cable...

I emphatically agree with this. LMR cable is BAD BAD BAD for repeater usage.

 

[kayn1n32008]

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I never said that. My comment was about ERP. 36w x 9db gain = 288w ERP. I was showing our young ham what the difference between RG-58 and low loss hardline.

ERP: power times gain = ERP value into an isotropic radiator

Right answer, but the way you're showing it could be misleading.

ERP is essentially adding up all the gains and losses. "power times gain" is correct, but in the case of 9db gain, that's a power gain of 8. Confused yet?

One way to calculate ERP is to convert the power out value to Dbm. 36 watts is about 45.5 Dbm. Now add the 9 db gain. that's 54.4 DBm. Convert to watts, and you get about 288 watts. In reality, you would also subtract the cable loss. so, in example, 45.5 Dbm transmitter power out minus, say, 3 db loss on the feedline, so you have 51.4 Dbm ERP. That translates to about 140 watts.

In other words, convert all values to Db. Add and subtract the Db gains and losses, then reconvert back to watts.

Makes sense, zz, thanks for clearing it up. I think that who ever said he needs an elmer hit it on the head! I love the enthusam that he has, and with the help of someone with some advanced knowlege he will have sucess in his endevor

 

[OCO]

I'll contribute my Heath Cantenna to the cause ..Perfect for the desired ERP from his setup. .Also - I need to run out and get more popcorn, this show may be on for a while...Very selective listening filters in use, kinda like maybe CW filters in use in the middle of 20 meter SSB??

 

[kayn1n32008]

Yes, Befor I just thought if i was using 25 watts, i can run feedlin to an antenna and get 25 watts.

I have learned a great deal of things on this forum by asking questions. Thanks everyone for the great information and i now have saved time and money.

There has never been nor will there ever be a feedline that will have 0 loss. you will always lose some power. The amount of power depends on 1. Frequency, and 2. Quality of coax.

25watts is plenty of power. Where the problem lays is how you get it to the antenna. If you use RG-58 or some other crap cable then most of the power is going to be absorbed in it and it will not matter one iota what kind of antenna you have. OTOH if you use hardline most of that power will make it to your antenna.


Just putting an amp and a preamp using 100' of RG-58 will only have a marginal effect.

 

[centuryvrproductions]

OK well if I am running 25Watts from the duplexer and I run LDF4-50A cable from the duplexer up to a 6db antenna at about 50ft, what problems will I run into?

Also, What type of connections should be made between the Line and antenna, and Duplexer.

And yes i realize that I cannot use RG-58. It is crap at 440Mhz, Thats why i use LDF4-50A, has the least ammount of loss at 440

 

[zz0468]

OK well if I am running 25Watts from the duplexer and I run LDF4-50A cable from the duplexer up to a 6db antenna at about 50ft, what problems will I run into?

Also, What type of connections should be made between the Line and antenna, and Duplexer.

And yes i realize that I cannot use RG-58. It is crap at 440Mhz, Thats why i use LDF4-50A, has the least ammount of loss at 440

Have you looked at the repeater builder web site? The answers you seek are there, not in vague, open-ended questions asked here.

 

[centuryvrproductions]

Have you looked at the repeater builder web site? The answers you seek are there, not in vague, open-ended questions asked here.

Ok, I will read the entire page of antenna information. I think I have everything else covered. Just antennas is what I need to learn more about

My repeater is already setup I just need to get an antenna system so I will Read up on this topic...

 

[RadioDaze]

I'll say one thing for the OP - he's enthusiastic; same day his license was issued, he's asking about putting up a repeater: http://forums.radioreference.com/am...ion/203169-owning-repeater-3.html#post1537106

 

[centuryvrproductions]

I'll say one thing for the OP - he's enthusiastic; same day his license was issued, he's asking about putting up a repeater: http://forums.radioreference.com/am...ion/203169-owning-repeater-3.html#post1537106

I have spent a majority of my time during school summer vacation working on how to improve my radio setup and my Repeater. I love the hobby. I think a hobby like this can get me a great job as i also go to a tech school for Electronics. I still have much to learn

 

[RadioDaze]

I have spent a majority of my time during school summer vacation working on how to improve my radio setup and my Repeater. I love the hobby. I think a hobby like this can get me a great job as i also go to a tech school for Electronics. I still have much to learn

A lot of new hams never get past learning how to recharge the battery on their new HT.