Amateur (Ham) Radio BS and Callsign Thread!

W5BSC/BOSS?

 

Hams I need your help! I just completed my mobile install and SWR check. It’s a dual band radio/antenna and the SWR readings were higher on the low end of each band than at the high end indicating I need to lengthen my antenna. I have reached the extent of adjustment on the antenna and still having same issue. What possible options do I have to continue tuning?

Current readings:
Bottom of 2m ~3.1 SWR
Top of 2m ~1.6 SWR

Bottom of 70cm ~2.0 SWR
Top of 70cm ~1.2 SWR

Ideally I’d like to get both bands completely under 2.0, but I use 2m more frequently so I care more about that band.

Radio: Kenwood D710
Antenna: Comet SS680SBNMO

Based on the relatively good SWR reading at the top of each band my thought is the rest of the radio install/location of the antenna is ok and the length of the antenna is the defining factor. Thoughts? If I do need a new antenna do you have recommendations? Current antenna is about 27” tall I think and would like to keep a similar height if possible. Thanks for your help!

 

Can you post some photos of how your antenna is installed? What frequency is your SWR the lowest? Is this a new or used antenna?

 

The antenna is used, but I am the only owner. I removed it from a truck I sold and installed it on my new truck. I never did measure the SWR when it was installed on the old truck so I have no data to compare to. See below for a picture of the install. Right now it has the lowest measured SWR at 450MHz.

 

Is it bonded to the bed? Hard to tell from the photo. I see the plastic cap on the edge of the bed.

 

There is no extra bonding strap/wire, but the mount makes metal on metal contact with the bed underneath the plastic cap.

Here’s a photo of the mount so you can see what I mean.

 

Best Freq for antenna based on Phone Use
160m - 1.9Mhz
80m - 3.9Mhz
60m as per Channel I dont go here
40m - 7.215Mhz
30m - 10.125Mhz per Data Use
20m - 14.250Mhz
17m - 18.135Mhz
15m - 21.300Mhz
12m - 24.960Mhz
10m - 28.500Mhz
6m - 51.0Mhz
2m - 147.0Mhz
1.25m - 223.0Mhz
70cm - 440.0Mhz

 

it might be isolated after the bed. Can you get a continuity check? The composite bed plays games for conductivity and grounding. You might be against metal but that’s against plastic again.

 

The leads of my multimeter can’t reach from the mount to the negative terminal of the battery to get a continuity check. This is on a full size pickup with a metal bed, but I suppose the bed could still be isolated from the chassis. I’ll have to poke around some more tomorrow with the multimeter. It’s been difficult to find unpainted surfaces to check continuity with.

 

That is a suboptimal place to put an antenna. Looks like it's linear loaded so might be ground independent. What are you measuring SWR with?

 

....I now see that is not a Tacoma. I saw the antenna and thought it was

see if you can run a strap or something maybe? I think even with a steel or aluminum bed, the conductivity from bed to frame is pretty mediocre. Is it an HD with mounts for a goose neck?

 

Yeah it’s definitely not an optimal location, but I’m not going to be drilling the roof and I really don’t like fender mounts. I’m measuring SWR with the below meter. Based on the readings I am getting, and the improvement I saw as I lengthened the antenna, I believe I could get plenty acceptable SWR across both bands if the antenna just had more adjustment allowing further lengthening.

No gooseneck mount, it’s just a half ton pickup.

 

That looks like a CB SWR meter. I wouldn't trust what it does on VHF/UHF. Check the SWR with your radio. It would also be beneficial to check SWR mounted to something else. Cab metal that close is likely to alter tuning.

 

I didn’t realize the kenwood had the ability to check SWR natively. I checked the manual and I’m not seeing anything about it. Have a link showing me how to get that done? Much appreciated!

 

The bed doesn't really need bonded to everything else to give you a good ground plane. You should be fine if that clamp is making good contact with metal. Just make sure it isn't clamped to paint or primer.

I agree with the meter comments though. Is it for 11 meters or 2 meters?

 

The meter doesn’t specify what band it is intended for, only that it is designed for 50 ohm impedance. Based on this I’d assume it would be accurate in this use case. Especially since it has a calibration knob that you set based on forward power measurement before each reading of reflected power.

I’ll have to verify there is no paint/primer between the clamp and bed. I assumed it was raw metal since it’s on the inside of the bed but I could be wrong.

 

Nope, you cannot use an HF watt/swr meter to obtain a useful reading on vhf/uhf.

If this was possible, Bird wouldn't make as many different slugs as they do :^)

https://www.martinrfsupply.com/bird-43-wattmeter-elements.aspx

 

Well alrighty then. I guess I have no earthly idea what kind of SWR my current setup has haha. Thanks for the help gents. Guess I ended up more questions than answers. Down the rabbit hole I go!

 

I would just try transmitting with it. If your rig doesn't fold back power and you can hear stuff, use it like it is.

Although if you already altered lengths of the radiators, it may now be out of whack....

In 25 years of ham radio, I've never adjusted tuning of a store bought VHF/UHF antenna.

 

Just buy a nano VNA. Great investment.