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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