Ok, I think I finally got it tuned about as well as I’m gonna get it without an antenna upgrade. I got the new whip I had ordered but I decided to try to tune the old one first. Figured I had nothing to lose by cutting on it before I start cutting the new one. Also, I found out how much of a difference moving the antenna can make.
I went back to the same field I’ve been going to so I could be sure there is nothing around me for at least 200 feet in all directions. Then I tested channels 1-20-40 again with the antenna where it has been up until now, to establish a base. SWR readings below.
1 - 1.8
20 - 1.5
40 - 2.66 and rising
I began moving the antenna towards the rear of the truck and tested again, and I noticed the SWR was beginning to drop a little. Finally I tried it all the way back at the end of the cab and that was the lowest SWR I had seen prior to cutting. It is behind my shark fin AM/FM radio antenna there so there is just enough room for the CB antenna magnet base to sit on before it would be off the end of the cab. The sheet metal is not completely flat right there but the magnet seems stable enough. I’d prefer it dead flat but after I finished my setup I now believe I’m gonna have to accept it where it is. The antenna SWR was the lowest it had been so far right in that spot. Precut reading below.
1 - 1.6
20 - 1.4
40 - 2.6 and rising
I have noticed the SWR on 40 seems to continue rising instead of stabilizing when I key up to check it. I don’t know why that is, but anyway, I began to trim the antenna to try to bring the SWR down on channel 40. That was a slow process taking 1/8 or less off at a time and then rechecking it each time. I cut it three times in total and then checked SWR on 1-20-40, and sometimes even on 1-10-20-30-40 to get a broader view of the SWR across the whole band. After the first cut, I checked it with the antenna in three different locations, and it was again best at the very rear, so I continued testing and cutting with it in this location from there onward.
I took off a little over 1/4 inch in total and got the SWR down until finally I noticed that channel 1 was now higher than it was on 40.
1 - 2
20 - 1.3
40 - 1.8 and rising
So I very slightly raised it again, probably only 1/16, and checked it again. It seemed good now so I checked it across the entire band every 10 channels. For some reason even channel 40 didn’t rise that time. Here’s what I got.
1 - 1.9
10 - 1.45
20 - 1.25
30 - 1.42 (just barely above the mark)
40 - 1.8 stabilized, no longer rising.
I stopped with that. But before I drove away I wanted to at least see if the Micronta meter would also indicate field strength. The Surecom SW-114 had just barely responded when I had held it out and keyed the mic. This Micronta does far better than that. The needle jumped up into the 3-4 range (out of 5) on the gauge. So now I’m very curious to set up a 25 foot circle perimeter around the truck and get someone to key it while I record the field strength readings around it to see what kind of propagation pattern I’m getting.
A couple more things to add. In all this tuning, I stripped the hex head depression out of the set screw. So I ordered some stainless steel 3/16 set screws on Amazon, thread size 10-32, and they fit perfect to replace it. Also, a Wilson Little Wil antenna whip will fit the K30 base. The whip seems more limber, the K30 whip is definitely stiffer. I’m also noticing that the conical nut at the base of the K30 that the whip sits in keeps loosening. I’ve had to tighten it twice. Overall, I’m not totally wowed by the K30. It does receive very well, and apparently even with bad SWR I was able to get out to people for a few words here and there, but I believe I could probably do better with another antenna. I might even have to just pucker up and drill a hole through the roof for a stud and put on a solid one of a much nicer type down the road.
