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Call Sign : 2-CT-198 Posts : 5 Times Thanked : 0 Join date : 2021-05-17 QTH or Location : Baton Rouge, Louisiana Equipment Used : President Walker 2 Age : 57
Subject: SWR Issues Wed Nov 03, 2021 8:45 pm
I guess let me emphasize That I have a number 8 copper insulated wire going from antenna bracket to chassis. Isn't there some sort of "rule of thumb" about cb/ham grounds?
Used CB's frequently back in the day yada yada... Recently installed a President Walker 2 using with a Wilson 5000 trucker antenna. This is all set up in my 2019 Ram 1500 Classic (antenna is mounted to rear of truck box via bracket). Bracket grounded to chassis and of course oil can is insulated from bracket.
I can't get below 2.6 SWR on 1, 20, 40. I did shorten antenna from 52" to 51" and that helped. Is it true what they say about "grounding in between everything"? Instead of running ground directly to chassis? My antenna (rear of tool box) is centered. Coax is minimal and only looped once under drivers seat. All connections tight. Radio has a built in meter (which comes in handy!) but I also have a separate RF meter.
Let me know if you need more info! TIA
Last edited by dieselhorses on Sun Nov 07, 2021 11:19 pm; edited 1 time in total
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: SWR Issues Thu Nov 04, 2021 8:29 pm
www.k0bg.com and the sections on mounting, grounding and most importantly, bonding.
CB antennas are manufactured at a length assuming they're going to be installed badly with a poor RF ground as many are - we're talking about RF grounds, not DC grounds and you can't measure a RF ground with a multimeter/ohm-meter as those are DC. The more efficient the RF ground the shorter the radiating element needs to be for a given frequency, this is covered in the ARRL Antenna Book. What that means for those of us who have vehicles, mounting method and location that provide a good RF ground is that the antenna is usually too long, even on it's lowest adjustment. For me I tend to find that out of the box antennas like the Sirio 5000 I have are resonant around 26MHz and there's not enough adjustment. With my Sirio I had to cut 3 inches off to get it up to 27.500. I have an antenna analyser I use to both check what's happening before I start to alter anything and to see what's happening as I do it.
You can't really do it with a CB and a SWR meter because the range of frequencies between the lowest and highest channels aren't wide enough, you really need something that can sweep a couple of MHz so either an antenna analyser or a widebanded amateur HF set/something like widebanded President Lincoln etc that cover 26-30MHz.
glenn dog, SangueG and Chickenfoot@1987 like this post