[TowerTalk] Remote Antenna Relay

[n4kg@juno.com]

Look at the basics.

What frequencies do you plan to send down the coax?

Capacitive and Inductive reactance are frequency dependent.

Xc = 1 /(2*pi* F*C)       XL = 2* pi*F*L

With  reactances of 3X 50 ohms, you WILL see a change in SWR.
At 10X 50 ohms, a slight change will be observable.
At 30X 50 ohms and above,  the effects will be miniscule.

With appropriately chosen values, you should be able to 
cover a 4:1 frequency range (10 thru 40M or 40 thru 160M)
but covering 10 through 160M is a bit much to ask for one
set of values.  Watch out for high frequency self resonances
in LARGE inductors.

Remember that your inductors and capacitors will need to
be able to withstand the associated RF Voltages and Currents.

de  Tom  N4KG


On Thu, 28 Dec 2000  "Allen Jones" <aejones4@home.com> writes:

> I want to control an antenna relay at the base of my tower by feeding
> control voltage down the coax instead of running a separate control 
> cable.
> I know this is usually done by putting blocking caps at each end of 
> the coax
> cable and using chokes to isolate the power supply and relay coil 
> from the
> RF.  Anyone know what value choke I should use?  Is the value of the 
> caps at
> all critical?  I was planning on using 1000 pf.  I know I've seen a 
> project
> like this in print but can't recall where.
> 
> Thanks
> 
> Allen Jones, W9DZ
> w9dz@arrl.net
> 
 

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