Base station- how much coax is too much?

[Dart]

I am finally getting ready to put up my tower and get a base antenna up in the air. I have chosen LMR-400 as my coax of choice, based on performance and cost factors.

I can put the Rohn 25G tower next to my house, using the standard concrete installation and a roof support bracket, but I really don't want to bolt anything to my house.

I have a Rohn self supported tower also, and the spot where I'd like to place it in my backyard would require a good 200' of coax (50' coming down the tower and 150' to get it in the house).

Is this 200' run of coax a bad idea? I have several buddies that are screaming about loss in the coax, but I always run with a little help watt-wise.

Any advice or thoughts would be greatly appreciated.

 

[222DBFL]

You could use LMR400. It has about 2db of loss at 100 meters on 27mhz. At 30mhz it's 2.2db of loss at 100 meters. Here is the chart below.
Also you could look at LDF4-50A, which will have about 1db of loss at 100 meters. Or about 7.db of loss at 200ft on 27mhz. Here is the chart for that coax as well. Either will work. Hope this helps.
1st pic is of for the LMR400. 2nd pic for the LDF4-50A. This is the loss of these coaxs at different freqs. Again, hope it helps. Have a good one.

 

[sp5it]

If you have more than 6dB loss at desired freq it is too much imo.
Mike

 

[Dart]

If you are going to make a run that long, being 200ft, I would look into a coax type like LDF4-50A or larger. The loss is much less then even LMR400, being about .3db or so at 100ft.

Thanks for the tip. Do you think that coax is suitable for burial, or would I have to end up putting it underground in PVC pipe?

The list of things to do keeps getting longer.

 

[222DBFL]

Commscope or Andrew will give you all the specs for both their LMR400 type coax which is CNT400, and the LDF4-50A and larger coax. Just go to commscope.com and you'll see their line of coaxs. And all the specs and uses. Don't skimp out here if you intend to make a long run. Get good coax and connectors as well. It will pay in the long run!!! As well as a good antenna setup!!

 

[RatsoW8]

I know everyone seems to use LMR400 but I went with Davis RF Bury-Flex low loss. It's direct bury coax similar to LMR400 and at 200 ft. loss is about 2.2db. I ran about 125 feet to my antenna switch. Dug a shallow ditch and pushed it into the ground - very easy and much easier that burying pvc IMO.

 

[222DBFL]

Yep. Not dissing them kne bit Ratso. There are a few other companies that make great coax. I was just giving him some info to go by. Commscope has a good attenuation/loss chart for most coax types. And there are other sites that do as well. LMR400 should be plenty fine. Just make sure it's direct burial!!

 

[222DBFL]

If you are planning on burying it that is LOL!!

 

[Xitami]

I am finally getting ready to put up my tower and get a base antenna up in the air. I have chosen LMR-400 as my coax of choice, based on performance and cost factors.

I can put the Rohn 25G tower next to my house, using the standard concrete installation and a roof support bracket, but I really don't want to bolt anything to my house.

I have a Rohn self supported tower also, and the spot where I'd like to place it in my backyard would require a good 200' of coax (50' coming down the tower and 150' to get it in the house).

Is this 200' run of coax a bad idea? I have several buddies that are screaming about loss in the coax, but I always run with a little help watt-wise.

Any advice or thoughts would be greatly appreciated.

200ft of lmr400 is fine, i run 300ft of lmr400(100m) cant notice the loss, minimal, gotta be a pin pricker to think 200ft is to long for lmr400

 

[RatsoW8]

Yep. Not dissing them kne bit Ratso. There are a few other companies that make great coax. I was just giving him some info to go by. Commscope has a good attenuation/loss chart for most coax types. And there are other sites that do as well. LMR400 should be plenty fine. Just make sure it's direct burial!!

Honestly at the last place I lived I had 2 75 ft. runs of plain old RG8X buried in the yard. One in PVC that filled with water and the other directly in the ground. When I pulled it all out when we moved in 2015 neither had water incursion. Go figure.

I was just tossing out the Davis as an option.

 

[Captain Kilowatt]

If you have more than 6dB loss at desired freq it is too much imo.
Mike

6dB??? 3dB is too much IMHO. I am not a stickler for losses but below 30 Mhz there is no reason to have even 3 dB losses. VHF/UHF may be a different story but there are options for that too.

 

[fourstringburn]

You could go with a remote tuner installed at the antenna feedpoint. This typically negates coax losses between the tuner and radio. They come with bias Tees that tap power from the coax line so no additional wiring needed. Just deadkey your radio(barefoot) and auto-tune will commence.

At 200 ft. Or more, losses do add up but as others have said, it's not a lot to make much difference.


These outdoor remote tuners come in 200, 600, and 1500 watt models.

CaptainKilowatt will probably chime in and give his opinion whether these will be worth the expense for your station.

I would like to read his or anyone's opinion on this.

 

[543_Dallas]

You can play with this calculator to decide what you want to use. http://www.qsl.net/co8tw/Coax_Calculator.htm

I can't see the benefit of a remote tuner or any tuner for a CB antenna. If he were using multiple bands and coaxial feedline the remote tuner would be a great idea.

If he had a 1.3 swr at the antenna the lmr 400 would have 1.2 db loss. With 100 watts in 74 watts makes it to the antenna. I believe that's acceptable but LMR 600 would only have .8 db loss. Don't skimp on the coax because it will affect your RX too.

If I were in this situation I would use the Jefa Tech brand LMR600. Not sure if it's rated for direct burial but with such a long run I'd look into that and use something that is.

If you use an amplifier consider the possibility of putting it closer to the antenna than the radio. Sounds crazy at first but it keeps loss down and heat out of the shack. Maybe in a garage or shed located closer to the tower.

 

[Captain Kilowatt]

You could go with a remote tuner installed at the antenna feedpoint. This typically negates coax losses between the tuner and radio. They come with bias Tees that tap power from the coax line so no additional wiring needed. Just deadkey your radio(barefoot) and auto-tune will commence.

At 200 ft. Or more, losses do add up but as others have said, it's not a lot to make much difference.


These outdoor remote tuners come in 200, 600, and 1500 watt models.

CaptainKilowatt will probably chime in and give his opinion whether these will be worth the expense for your station.

I would like to read his or anyone's opinion on this.

543_Dallas pretty much said it. A remote tuner will not do anything for this case. The coax is still there. It would only minimize losses due to SWR which will already be minimal if the antenna is tuned anywhere near properly. I ran a remote tuner at one time but it was for a multiband antenna fed with ladderline which was hard to get into the shack so I ran coax out to the far end of thee house and fed the remote tuner with it. With SWR as high as 25:1 (yes twenty-five to one) on some bands it was necessary in order to keep losses low.

 

[Robb]

LMR-600?
Ouch!