Antenna question on roof of 4Runner

[WRZP383]

Newbie here trying to figure out some antenna stuff.

2021 Toyota 4Runner with an overlanding rack on the roof.  Aluminum side rails with aluminum cross bars 8-12" apart.  Rack is bolted to stock roof luggage rack mounting points

UT-72G magnetic antenna

Laird B4502NR antenna

Melowave 3/8" NMO antenna mount with 14.5' CFD200 cable

Wouxun kg-935+ handheld

I have been using the HT with the Nagoya on the roof of the truck between the bars and it has worked pretty decent.  Bought the Laird 1/2 wave for my SxS since I do not have a good place to put a ground plane.  Saw some threads about that I really should have the antenna in the clear on the truck instead of between the crossbars so I got a piece of 16ga steel 12"x18" and mounted it on top of the crossbars for a ground plane/place for the magnetic base to stick.  I did paint the steel with some Rustoleum.  I also put the Melowave in the middle of the steel thinking I could try the Laird on the truck and potentially move it between the truck and SxS if it worked better.  Reception with the Nagoya now seems to be a little worse on the steel and transmit I can't hit the repeaters as well either.  I checked the SWR with a Surecom 102 (yeah seems people really don't like them) and Nagoya shows 1.4 but with the Laird/Melowave it's 2.4 so I didn't hit transmit to try it.  Is moving the groundplane off the roof itself a bad idea?  Obviously the roof is painted and it worked there but is the type of paint a problem?  What would cause a high SWR with the Laird?  Also saw some threads with a handheld the SWR is not that important/made to handle a high SWR?

[OffRoaderX]

Are you talking with your friends on the trail, or trying to bounce signals off the moon and talk to strangers across the planet?  

If you are using your radio for talking to your friends on the trail then SWR of 1.4 is fine and SWR of 2.4 is good enough. Stop overthinking it and just enjoy the radio.

[kidphc]

That laird is pretty short antenna, is it any of it viewable above the basket?

If anything the basket is probably causing some screwy swr and radiation patterns.

Hence, why I have been eyeballing low profile flat racks or just ditching my roof rack on the landcruiser.

From some anecdotal, both by the butt meter and nano vna, testing I did with 1/4 waves and such even when I had a z71 suburban, the big boy roof rack played havoc on shorter antennas.

If they are mag mounts try to keep about 6-10 of roof underneath the antenna and recheck swr. Then bring it closer to the roof rack you should also try making contacts. The roof rack or other accesories close by will give you grief. If you can clear these obstacles you probably will get better performance.

One landcruiser, owner on expedition portal had a rack made. Company became prinsu, but either case he had it made with ears on the back that were also a bit folded. To mount two 1/4 wave antennas. What he failed to mention is that he had to strap (ground straps) parts of the rack to the interior roof to main continuity between the rack and roof (improving his ground plane). The ground plane size and shape can and will affect performance.

In your case I don't think it is a ground plane issue, but more helps to a degree. I believe you are seeing these results due to where the antennas sit in relation to the basket. I also think you should mount them to the hood and double check swr numbers to make sure all is good.

Another note paint types for antennas are really going to matter on the active element more than the ground plane.

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[WRZP383]

2 minutes ago, OffRoaderX said:

Are you talking with your friends on the trail, or trying to bounce signals off the moon and talk to strangers across the planet?  

If you are using your radio for talking to your friends on the trail then SWR of 1.4 is fine and SWR of 2.4 is good enough. Stop overthinking it and just enjoy the radio.

Just catch some local repeaters currently and later on the trail.  Found it interesting that putting the antenna on what I thought was a good ground plane made it worse from real life can't hear as good and catch the repeater for transmit where I used to.  I just checked SWR to be safe since people said high SWR is hard on radios and saw the big difference between the 2 which I found interesting/wondering how can make better just to know.

[nokones]

The 2.4:1 is less than 3.0:1 so it'll be fine for communicating between people on the trail. It may suck a little if you're trying to communicate with someone at great distances.

One of the reasons why the Laird has a higher VSWR is because the transmitting  frequency is not matching the tune of the antenna. The antenna may need to be trimmed and for GMRS I would tune/trim it for 465 MHz.

[WRZP383]

3 minutes ago, kidphc said:

That laird is pretty short antenna, is it any of it viewable above the basket?

If anything the basket is probably causing some screwy swr and radiation patterns.

Hence, why I have been eyeballing low profile flat racks or just ditching my roof rack on the landcruiser.

From some anecdotal, both by the butt meter and nano vna, testing I did with 1/4 waves and such even when I had a z71 suburban, the big boy roof rack played havoc on shorter antennas.

If they are mag mounts try to keep about 6-10 of roof underneath the antenna and recheck swr. Then bring it closer to the roof rack you should also try making contacts. The roof rack or other accesories close by will give you grief. If you can clear these obstacles you probably will get better performance.

One landcruiser, owner on expedition portal had a rack made. Company became prinsu, but either case he had it made with ears on the back that were also a bit folded. To mount to 1/4 wave antennas. What he failed to mention is that he had to strap (ground straps) parts of the rack to the interior roof to main continuity between the rack and roof (improving his ground plane). The ground plane size and shape can and will affect performance.

In your case I don't think it is a ground plane issue, but more helps to a degree. I believe you are seeing these results due to where the antennas sit in relation to the basket. I also think you should mount them to the hood and double check swr numbers to make sure all is good.

Another note paint types for antennas are really going to matter on the active element more than the ground plane.

Sent from my SM-S901U using Tapatalk
 

The tops of the bars are right under the top of the spring part on the 72g.  It works better on the roof between the bars than on the plate mounted to the top of the bars.  Figured mounting the plate would be a double bonus, maybe better for the Nagoya and also get an NMO mount for other antennas.

5th Gen 4Runner Roof Rack | 2010-2024 4Runner | Sherpa Equipment Co. (sherpaec.com)

[WRZP383]

1 hour ago, nokones said:

The 2.4:1 is less than 3.0:1 so it'll be fine for communicating between people on the trail. It may suck a little if you're trying to communicate with someone at great distances.

One of the reasons why the Laird has a higher VSWR is because the transmitting  frequency is not matching the tune of the antenna. The antenna may need to be trimmed and for GMRS I would tune/trim it for 465 MHz.

The Laird is supposedly 450-470 and adjustable.  Do I try shortening or lengthening and how much should move at a time?  1/8" 1/4" or ?  Looked at NanoVNA but haven't dove down that rabbit hole yet

[nokones]

3 hours ago, WRZP383 said:

The Laird is supposedly 450-470 and adjustable.  Do I try shortening or lengthening and how much should move at a time?  1/8" 1/4" or ?  Looked at NanoVNA but haven't dove down that rabbit hole yet

It would depend on what the resonate freq is for the antenna and cable. An antenna analyzer will give you that info. 

[WRZP383]

1 hour ago, nokones said:

It would depend on what the resonate freq is for the antenna and cable. An antenna analyzer will give you that info. 

So I guess I should figure out which NanoVNA to buy.  Looks like a couple models

[kidphc]

So I guess I should figure out which NanoVNA to buy.  Looks like a couple models

Aliexpress and one other store are the official ones if that matters.

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[WRZP383]

21 hours ago, kidphc said:

Have you thought about hatch or hood mounts.

Or the wanna be... high clearance bumper with antenna mounts....

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Don't want anything on my hood and hatch would be essentially where current antenna is.  Have stayed away from high clearance bumpers, don't want the extra weight.  Rig is used to haul the SxS and more trail type excursions so I don't tear this one up.  Thanks for the ideas though!

To Randy's point I'm gonna slap the antenna on and see how it does.  I can overthink/tune this if it doesn't work.

[WRVR303]

The Laird will be on the long side to start with. That is, a 450 MHz antenna is longer than a 470 MHz antenna, so you will need to cut it shorter. On a Laird 4505 I have the suggested cut lenghts were around 11-5/8" at 450 and 10-1/8" at 470, but per a NANO VNAH4, (and double checked with a Daiwa SWR meter), for 465 I stopped at 10-1/8". Don't cut your antenna based on my numbers, get the antenna cut chart for your exact model from Laird. On mine, there was a cut chart on the package.

But, with your SWR meter, you can start cutting 1/8" at a time, until you make a cut and don't see any more change. 

[kidphc]

The tops of the bars are right under the top of the spring part on the 72g.  It works better on the roof between the bars than on the plate mounted to the top of the bars.  Figured mounting the plate would be a double bonus, maybe better for the Nagoya and also get an NMO mount for other antennas.
5th Gen 4Runner Roof Rack | 2010-2024 4Runner | Sherpa Equipment Co. (sherpaec.com)

Have you thought about hatch or hood mounts.

Or the wanna be... high clearance bumper with antenna mounts....

Sent from my SM-S901U using Tapatalk