Not new, but need a little SWR help

[Colin9690]

Hey there guys, finally installed my Uniden 980 SSB into my 2010 Honda Civic coupe. Not the most install-friendly vehicle by any measure, but I made it work and it looks good/clean. I know what SWR is, how to measure it, and how my specific environment can influence my readings. Since this particular radio has a built-in SWR meter, I'll say that I am using a "proper" external/traditional SWR meter for these readings.

Using a trunk-mounted Lil Wil magnet mount antenna, I am getting 2.4 SWR on Channel 1 and 3.5 SWR on Channel 40. If I'm understanding correctly, I need to shorten the antenna. Problem is, the antenna whip is all the way inserted into the base (as far as it will go). So does that mean I need to cut it slightly, like with a saw?

Later tonight I'll park my car in the middle of nowhere and re-test the SWR, so I can feel confident on those numbers before I go cutting anything. I just wanted to make sure my brain is on the proper page and that it's not the other way around. What do you guys think?

 

[RFI-EMI-GUY]

If it is trending 2.4 on Ch 1 to 3.5 on Ch 2 without any significant dip between it does seem to be a bit long. Be sure your tests are done with doors, trunk, hood closed up. Being a mag mount, the coax cable routing can screw with things, and the trunk mount is worse than roof mount. You might check VSWR on center of the roof to confirm you get same trend.

 

[Colin9690]

If it is trending 2.4 on Ch 1 to 3.5 on Ch 2 without any significant dip between it does seem to be a bit long. Be sure your tests are done with doors, trunk, hood closed up. Being a mag mount, the coax cable routing can screw with things, and the trunk mount is worse than roof mount. You might check VSWR on center of the roof to confirm you get same trend.

Thank you for the reply, I will keep all that in mind later when I drive out to a wide open, empty lot later to confirm. Will try it on the roof there as well, and see what I get.

I did this in my driveway after the install, with my 2 other vehicles blocking the CB vehicle in. And, there's several trees in the immediate area, so definitely not the best conditions for any sort of legit experiment, haha. Thanks again for the help.

 

[ko6jw_2]

I would suggest that before cutting you look at a different mount. Mag mounts sometimes work well, but other times no amount of cutting will get a good match. The mag mount may not couple to the car body well enough to get a good ground plane. Try to get hold of an antenna analyzer. That will show you where (if anywhere) there is a lower SWR. I have had situations where there was no good match because of the mount. Don't cut up your antenna until you know for sure what's causing the mismatch.

 

[MisterLongwire]

Do not rely on the SWR meter on the unit. Spend the $10 or so and get a separate set meter with patch cord. More accurate

 

[Colin9690]

Like I said off the bat, I'm using a proper external meter (not using the radio's built-in meter.)

Just an update, I did indeed have to take off about 3/4" with my boltcutters. After that, 1.1 SWR on Channel 19, and less than 1.3 everywhere else. Just talked to a guy on SSB who's in Nevada. I'm in Ohio, parked in my driveway. Pretty darn cool. Thanks all!

 

[MisterLongwire]

Good job. Too bad the skip totally sux out here.

 

[FiveFilter]

Congratulations on your tuning success!

I've got a magnet-mount K30 antenna which is about the same size as the Lil Will, and I had to take about 3 inches off the top to get it in tune SWR-wise. Although they work well and allow one to get into relatively low parking spaces, these "shorty" antennas are not as flexible in regards to SWR tuning as are the tall boys.

 

[Ravenkeeper]

Congratulations on your tuning success!

I've got a magnet-mount K30 antenna which is about the same size as the Lil Will, and I had to take about 3 inches off the top to get it in tune SWR-wise. Although they work well and allow one to get into relatively low parking spaces, these "shorty" antennas are not as flexible in regards to SWR tuning as are the tall boys.

You took "3 inches off the top?"

I use to own a couple of K40s, and never trimmed the top.

 

[W5lz]

Just for grins, try moving the magmount to various places on the trunk, see if it makes any significant differences. Just depending on a lot of things, weather, what color socks you're wearing, etc, a couple/few inches can make a big difference. Since you've gotten things 'good' now, remember where the thing was!

 

[FiveFilter]

You took "3 inches off the top?"

I use to own a couple of K40s, and never trimmed the top.

Yeah, I always trim from the top, down.

The reason is those tiny set screws that are depended upon to hold the stinger in the base. Those little screws look mighty tinder to me, so I want to work them as little as I need to. I figure if I just need to tighten them once, that's about as little work as I can get by with.

So, I plant the stinger into the base, tighten those little screws, and get to tuning.

It sometimes takes a lot of trial-and-error when trimming an antenna to resonance. One time I bought an antenna that was 62 inches long from the factory, and I wound up trimming it to 55 inches to achieve resonance.

That's a lot of putting-in-and-taking-out of the base if the trimming is done from the bottom.

So, I trim it from the top, the specified fractional inch at a time, with the antenna firmly planted in the base.

Works every time. And the stinger don't seem to care either way.

Addendum: If there is a corona ball on the stinger's tip, it will have to be sacrificed if trimming from the top. I make the sacrifice if there is one, because I can't tell the difference with or without the ball. Most of my antennas didn't come with one anyway.

 

[W5lz]

I do it the other way around, bottom rather than the top. The top part is usually 'whippy-er' so keep it. Once you get it tuned (right length) put a dab of nail polish/glue/whatever to keep the setscrews from backing out.

 

[DJ11DLN]

I do it the other way around, bottom rather than the top. The top part is usually 'whippy-er' so keep it. Once you get it tuned (right length) put a dab of nail polish/glue/whatever to keep the setscrews from backing out.

Loctite Blue. It will hold the set screw and also keep it from corroding, so if it ever has to be removed for whatever reason, you have a good chance of coaxing it loose.