Ground Plane Issues with 1.0 SWR? PICS.

[amoking]

I'm running an Anytone AT-666 with a Bulletproof Diesel NMO mount and a Laird CB27S 1/4 wave antenna on my 2020 F350. Aluminum body and a panorama roof. SWR is 1.0 on 19 with little increase on either side as 1 and 40 are both 1.2.

I understand that CB usage on the roads is not what it once was but driving from the SF Bay to Los Angeles I was able to Rx perfectly but it seemed like nobody was picking me up. I Tx'd several times and only once got a response from somebody a mile away when I asked for a radio check.

With an aluminum truck and a big glass roof, could ground plane be an issue regardless of a 1.0 SWR with my Laird? Should I swap for a Firestick? I cannot put an NMO in the middle of the roof. @mmckenna can you opine?

Thanks.

KK6FTU

 

[KevinC]

My opinion is your radiation pattern is wonky due to no ground plane under the antenna. While you may have a good match SWR wise that’s only a part of the equation.

 

[mmckenna]

The ground plane is less than ideal, but that's going to be true for any road legal vehicle. Putting it towards the back of the cab with the vehicle dropping down behind the antenna like that isn't going to help things.

But, don't get hung up on it. I ran a Larsen NMO-27 centered towards the rear of an F-350 crew cab and it performed fine for what I needed. SWR was low on mine, also.

I wouldn't put a firestik on there. You've spent a lot on that mount, and you probably won't see much difference by going to a non-ground plane antenna. The lack of ground plane will still impact performance a bit.

My experience on I-5 was always similar to yours. You'd occasionally hear people, but difficult to get an answer. Actually getting a radio check is doing pretty good. CB isn't what it once was. I know about 10 years ago on I-5, running from the bay area up to Mt. Shasta it was the same. Finally heard two guys in trucks around Sacramento, but that was it.

 

[mmckenna]

My opinion is your radiation pattern is wonky due to no ground plane under the antenna. While you may have a good match SWR wise that’s only a part of the equation.

Yeah, ideal would be dead center of the roof, but that ain't an option.
I have a similar truck without the sun roof. Dead center is where the VHF whip went.

 

[amoking]

I agree with both of you. These trucks are less than ideal for mobile stuff but it's the hand we are dealt. Better than nothing but just double checking with guys who know more than I do.

 

[alcahuete]

With 10m hopping lately (and CB), are you sure it wasn't skip you were hearing, and the people you were trying to contact were nowhere near you? If that's the case, they're running a lot of power and you're not. Your chances of being heard are almost zero.

 

[amoking]

With 10m hopping lately (and CB), are you sure it wasn't skip you were hearing, and the people you were trying to contact were nowhere near you? If that's the case, they're running a lot of power and you're not. Your chances of being heard are almost zero.

I'm almost certain it was skip. Wasn't trying to respond to them per se.

 

[alcahuete]

I'm almost certain it was skip.

That would explain why none of them were picking you up. Could have been that there was just nobody local answering your call.

 

[mmckenna]

I agree with both of you. These trucks are less than ideal for mobile stuff but it's the hand we are dealt. Better than nothing but just double checking with guys who know more than I do.

Well, they're great if you don't have the sun roof.
Lots of ground plane to work with.

But I think it's working right. I know SWR isn't the only measure of a good functioning antenna, but you've probably done something right. Ground plane layout is probably making it directional towards the front (might be a good thing), but it sounds like it's all working. One mile radio check might be pretty good if there's a lot of noise on the bands.

Give it a try another time. That dude named Skip sure could be impacting things, but maybe you can try again when he's not being such a little, you know, b!†¢h.

 

[slowmover]

I’ve read several instances of better CB performance with Laird NMO30 or 34 plus 64”’whip trimmed to accommodate. I haven’t read anything says the NMO27 is on par with a Wilson 5000 or SIRIO 5000 much less a President Texas.

I’ll recommend willingness to experiment.

That said, California is dead-air all too often. AM-15, 17 & 19 are what to try. I can get someone on-air usually 70% of the time.

Don’t give up. Get a better antenna (taller). Employ some bonding, (see link; many subjects worth reviewing)

Mobile Install Bible

A Texas atop my Dodge crew cab hasn’t any problem with 7-12/miles from home (bad location due to noise).

Stay with it.

.

 

[amoking]

I’ve read several instances of better CB performance with Laird NMO30 or 34 plus 64”’whip trimmed to accommodate. I haven’t read anything says the NMO27 is on par with a Wilson 5000 or SIRIO 5000 much less a President Texas.

I’ll recommend willingness to experiment.

That said, California is dead-air all too often. AM-15, 17 & 19 are what to try. I can get someone on-air usually 70% of the time.

Don’t give up. Get a better antenna (taller). Employ some bonding, (see link; many subjects worth reviewing)

Mobile Install Bible

A Texas atop my Dodge crew cab hasn’t any problem with 7-12/miles from home (bad location due to noise).

Stay with it.

.

I'm all bonded. I think that it's just CA.

 

[slowmover]

Okay. Good. I’d still want a taller antenna.

CA ain’t a CB paradise down south. Gets better north of SF.

But it sure ain’t Ohio.