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Call Sign : 26-CT-3654 Posts : 31 Times Thanked : 0 Join date : 2020-06-14 QTH or Location : Wirral Merseyside Equipment Used : Yaesu Age : 53
Subject: New antenna info for Sirio 2016 Sun Dec 27, 2020 11:51 pm
Hi all,just purchased a Sirio 2016 5/8 vertical and need some info on grounding it.It says that it is DC grounded but do I still need to ground it for the small chance of a lightening strike? I’ve also seen on YouTube people having a few turns of coax at the base of the antenna as some sort of choke,is this necessary ? Many thanks Jerry.
Posts : 38 Times Thanked : 5 Join date : 2019-06-29
Subject: Re: New antenna info for Sirio 2016 Mon Dec 28, 2020 1:09 am
You don't have to have a lightening ground for the antenna to function. Further, most antennas used for CB will not survive a direct strike, or even a near miss. I've seen strikes over 100 meters away vaporize antennas. That being said lightening protection will minimize to eliminate other issues, such as the strike making it to other equipment in the house.
About the choke. You may or may not need one. The way to find out is to add three feed of coax and retest SWR. If it changes noticeably, then you need a choke. If you do need to make a choke, make sure you get your dimensions and number of windings right. More is not better, and in fact can make a problem that requires a choke worse. You can also buy snap on toroid beads as well, this is by far the easiest option, and unlike making an air choke, in this case more snap on beads is better.
Call Sign : M0GVZ / 26CT1760 Posts : 477 Times Thanked : 32 Join date : 2019-11-13 QTH or Location : IO94SA Equipment Used : Icom 7300, TS480, President McKinley, Albrecht AE6110, CRT Mike Age : 52
Subject: Re: New antenna info for Sirio 2016 Fri Jan 01, 2021 10:17 pm
I’ve also seen on YouTube people having a few turns of coax at the base of the antenna as some sort of choke,is this necessary ? Many thanks Jerry.
Yes. It's necessary to use a RF choke on all end fed verticals except ones like the Gainmaster which is actually a centre fed one.
Ideally you'd use a ferrite cored RF choke but if you make one from coax it's 5 turns of diameter 110mm/4.25". Waste pipe, the brown stuff you can buy from builders merchants, is the perfect size to wrap around.