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Re: [TowerTalk] Coax Question

To: "Tower and HF antenna construction topics." <towertalk@contesting.com>
Subject: Re: [TowerTalk] Coax Question
From: Ken Boasi <n2zn@rochester.rr.com>
Reply-to: "Tower and HF antenna construction topics." <towertalk@contesting.com>
Date: Tue, 13 Apr 2010 00:50:14 -0400
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
Steve,

You can find W3LPL's coax attenuation charts here:

http://www.k1ttt.net/technote/coaxloss.html

I have found this to be a handy reference.  You can also add in the  
loss for the LMR series cables by going to Times Microwave's website- 
they have an attenuation calculator to which you enter the type of  
cable, frequency, and length and it will calculate loss.

Ken N2ZN



On Apr 13, 2010, at 12:38 AM, N7KA@comcast.net wrote:

>
>
> Steve
>
>
>
> It that is a foot foot run from rig t ante4nna you have some serious  
> work to do.
>
>
>
> You need t study what loff you will get in 500ft of what ever feed  
> line you use.
>
>
>
> Here is some very basic info on loss, TX power vs power at the antenna
>
> 0.0 db loss = 100% to TX power reaches the antenna
>
> 1.0db loss = 89% of TX power reaches the antenna
>
> 2.0db loss = 79% of TX power reaches the antenna
>
> 3.0db loss = 50% of TX power reaches the antenna
>
> 4.0db loss = 40% of TX power reaches the antenna
>
> 5.0 db loss = 32% of TX power reaches the antenna
>
>
>
> Now look up loss per 100ft of any coax and multply by 5 (for 500ft  
> of coax run) and you will get the loss in that LONG run of coax.   
> Remember this long run also works against you on RX as well.
>
>
>
> Compare coax all coax at same freq, I woul d use highest band.  SO  
> if you plan to have 10M that far away, I would use 30MHz as the  
> comparison frequency.
>
>
>
> Here is some 500ft loss info at 30MHz:
>
>
>
> RG-213   =  5.0db loss
>
> LMR-400 = You find info
>
> 1/2in LDF4-50A = 1.785db loss
>
> 7/8 in LDF5-50A = .975db loss
>
>
>
> \I am too lazy at this point to look up LMR-400 so you look up the  
> 100ft loss at 30MHz and multiply by 5 for the loss.
>
>
>
> I will NOT be cheap to run a coax 500ft and NOTloose a lot of power  
> in the coax (its resistance) so get out the loan application papers,  
> you are gong to need it or else you will be running QRP and NOT by  
> choice. Get the biggest coax you can possibly afford.
>
>
>
> Hope tis provides info and perspective of the issue you face getting  
> the TX power through 500ft of coax to the antenna.
>
>
>
> I would never consider any coax loss greater that 1 db to be  
> acceptable.  I use 1/2 inch 50 ohm hardline on all my antennas above  
> 80M
>
>
>
> Arne N7KA
>
>
> ----- "Steve Bagley" <n2mai@arrl.net> wrote:
>> This may be a little off topic but I would appreciate your input.
>> I am putting up a tower and will need to run about 500 feet of  
>> coax.  Should
>> I go with LMR-400 or 213?  Any comments or input would be greatly
>> appreciated!  I am of course looking for the lowest loss.
>> 73's
>> Steve, N2MAI
>> _______________________________________________
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>
>
>
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