The *FIRST PLACE* for any common mode choke is at the feedpoint of
the antenna. You want to minimize any RF on the outside of the
feedline so it doesn't couple to any adjacent feedlines/control
cables. The best advice is to start with a choke on every antenna.
*ONCE YOU HAVE DONE THAT* placing a secondary choke (line isolator)
immediately inside the *grounded* entry window helps to clean up
any residual common mode RFI from radiated RF (or coupled from
adjacent feedlines).
Since you have problems specifically with the rotator controller
(probably due to coupling from a parallel coax), I would suggest
winding the rotator cable (from controller to rotator) 10-12 turns
through each of two 2.4" mix 31 ferrite toroids (just like the K9YC
designs). 12 turns will be skewed more toward higher isolation at
the lower end of 40-10 meters while 10 turns will skew more toward
the 15/12/10 meter end of the range but either design maintains a
relatively high choking impedance.
73,
... Joe, W4TV
toggle quoted message
Show quoted text
On 2025-03-04 2:57 PM, Salvatore Besso via groups.io wrote:
hello,
> install a high quality common mode choke ("line isolator")
> right at the antenna
I've also had heavy RFI problems in the past transmitting with high power, that caused the rotor interface (or maybe the USB port to which it was connected) to regularly crash and DXView to hang until I disconnected the interface cable. I have resolved this problem winding all the USB cables into Amidon FT-240-31 toroids, almost filling the whole circumference.
I have also bought a DXEngineering common mode choke that I still have to install. Since I have a remote antenna switch and only one coax that runs down from the roof to my house, the guys at DXEngineering told me that it would be better to install it in the shack, near the radio.
What do you think about? Any hint will be appreciated.
Thank you.
73 de
Salvatore (I4FYV)
