[TowerTalk] Coax Question

[N7KA at comcast.net]

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 at 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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