[TowerTalk] Adding an RF choke

[Michael Tope]

Mark,

What is the impedance of the feed lines that connect your array 
controller/hybrid to the individual elements?

If, for instance, those feed lines are 75 ohms, then you should use 75 
ohm coax for the chokes and then shorten the feed lines by 
18*Vfeed/Vchoke inches, where Vfeed is the velocity factor of the coax 
used for the feed lines and Vchoke is the velocity factor of the coax 
used to make the choke. If the choke impedance is different than the 
element feed line impedance, then you are going to upset to some extent 
the impedance transformation provided by the feed line. The higher in 
frequency the greater the impact (e.g. 18 inches at 1.8 MHz is much less 
of an impact than 18 inches at 7 MHz).

73, Mike W4EF..................

On 12/2/2024 8:26 AM, Mpridesti via TowerTalk wrote:
> Building a set of phased verticals and the phasing lines are critical (of course) so my question here:  by adding 18 inches of cable length (choke length) does the phasing line length need to be shortened by 18 inches?
>
> Or should I consider the choke as part of the antenna and not make any adjustments?
>
> Regards,
>
> Mark, K1RX
>
>
>