SWR High on DB25-G

[WRMD235]

Hello experts!

I am new to GMRS and having some issues with tuning my SWR on the Radioddity DB25-G radio and Rugged Radios UHF Stealth antenna on a 1997 Jeep Wrangler.  I have the antenna mounted on the cowl by the driver door using the Rugged Radio mount.  I ran the coax into the windshield channel, drilled into the frame to route the coax up by the rear view mirror.  Currently getting a SWR of 5.8 using a new Surecom SW-33 VSWR meter.  Tested ground on antenna mount to battery negative and saw .5 ohms.  Also tested from ground connection on PL-259 at the radio and got the same reading.  I do not have another antenna to swap out at the moment.

Also as a reference point, I also have a Radioddity GM-30 HT.  I put the SW-33 between the radio and the factory antenna to get a baseline.  SWR was 3.6 for this configuration.  Using GMRS channel 16 for all tests.  

Any help would be greatly appreciated!

[aa7jc]

 Is that antenna is next to the body of the vehicle?  

Ken WQXQ522

[aa7jc]

So.. I was unfamiliar with the antenna and thought maybe I wasn't seeing what I was seeing..  That is why I asked. But, I googled the antenna to see what it looks like in the catalog .. Yes. I am thinking that chief suspect for the high SWR is most likely the interaction of the car body with the antenna.  Thanks for the pics!  

Ken WQXQ522

 

[aa7jc]

So,  I just had another look at the manufacturers web site and wow! They have a photo of the exact mounting arrangement that you used with the antenna hugging the side of the vehicle...  That makes no sense to me but who knows the product like the manufacturer?  Still I would reach out to them and ask about why the SWR.  

[hfd376]

I would suspect the close proximity to the Jeep's body as reflecting the rf power back into the antenna/coax. You could try a different mount in another location to test.

[gortex2]

So either order a UHF 1/4 wave or move the antenna. Those antenna's are junk anyway. You can grab a 1/4 wave on amazon for $15 that will screw right on the mount.

[WRQD721]

Yes, cute gimmick antenna. Get yourself a 5/8ths wave antenna. A 1/4 wave whip would be just as buried against the body.

[KAF6045]

Concur on mount location... I'd suggest trying to find some way to put it above the hood (at least to test). (I also note the "factory" example image has it mounted above the door hinge but that may just reflect model changes). The main thing that "stealth" antenna seems to provide is a 1) small size which may reduce chances of getting snagged by branches, 2) sturdy shell to resist damage when it is snagged by branches.

Possibly you can find a mount (what is the base? NMO? SO-239?) that can clamp to the side of the hood that may lift it up higher, away from the body coverage.  Examples: https://www.hamradio.com/detail.cfm?pid=H0-009011 https://www.hamradio.com/detail.cfm?pid=H0-013386 https://www.hamradio.com/detail.cfm?pid=H0-013622  https://www.hamradio.com/detail.cfm?pid=H0-009009

[wayoverthere]

24 minutes ago, KAF6045 said:

Concur on mount location... I'd suggest trying to find some way to put it above the hood (at least to test). (I also note the "factory" example image has it mounted above the door hinge but that may just reflect model changes).

Possibly you can find a mount (what is the base? NMO? SO-239?) that can clamp to the side of the hood that may lift it up higher, away from the body coverage.  

I think the difference in relation to hinge is just hinge location changes between models, the height in relation to the cowl seems pretty similar.

That said, I also agree that the proximity of the body is probably the biggest issue. Tried a base setup clamped to a metal rack (about halfway up, to clear the ceiling...3.5:1 swr. Moved it to a tripod in the closet, away from the rack and anything else metal...1.1:1 on the same frequencies.

I believe @marcspaziis using lip mounts on the edge of his jeeps' hoods with good results

[WRMD235]

Thanks all for the comments.  I will try to use a different mount location and see how that changes the SWR.  May also try a different antenna that might get the reflection away from the body.  I had thought of using a trunk lip mount and putting that on the hood of the Jeep.  The top is fiberglass so would not provide any real benefit (other than perhaps getting the antenna away from anything on the Jeep!).  This antenna is on a NMO mount so changing out the antenna would be rather easy.  Relocating will be a bit more work, but I have a spare cable to work with too.

 

Appreciate all the help and advice.  Now to get working!

[KAF6045]

21 minutes ago, wayoverthere said:

That said, I also agree that the proximity of the body is probably the biggest issue. Tried a base setup clamped to a metal rack (about halfway up, to clear the ceiling...3.5:1 swr. Moved it to a tripod in the closet, away from the rack and anything else metal...1.1:1 on the same frequencies.

That's (proximity) is one reason I didn't try to install my old FT100 in my current vehicle (besides the fact that my brother lost the small screws used by the remote mount extension cable). My Jeep Cherokee (1999) tailgate had a "bent" profile -- the portion with the window was sloped \, and then the lower half was vertical | -- putting a lip mount just at the transition point meant the antenna  and body distance increased as one went up. Pity I rolled it on a wet off-ramp having practically no approach lane (go from 65-70mph with trucks roaring up one's tail to a tight cloverleaf ramp with a 35mph recommended speed). Went a quarter of the ramp with my headlights 3 feet from inside guardrail before it overcorrected and dived into the outside grassy slope. I suspect the radio itself is okay, but the ATAS screwdriver antenna may not be. At the least I would need to find a whip for the top, mine looks like Zorro used it for fencing. The top of the screwdriver/coil section was just at the roof line, and may have stripped threads (would have been worse if I didn't have it all the way down).

Replacement vehicle is a rust bucket Jeep Liberty bought from an in-law (bad mistake, by the time I get all the noticeable faults repaired I could have made a 25% down payment on a new Jeep Cherokee Trailhawk) has a vertical tailgate. No clearance for an antenna. It now sports a glass-mount 2m/70cm antenna (on tinted glass... against mounting instructions... The only clear glass is windshield -- too thick for antenna coupling; and front row windows -- good bye to opening window...

GMRS is a the puny mag-mount whip that came with the MXT-115. Cobra CB with its mag-mount whip. Both on the roof (and I have to tilt over the CB, and remove dual-band whip, to get in/out of garage)

 

[KAF6045]

15 minutes ago, WRMD235 said:

Thanks all for the comments.  I will try to use a different mount location and see how that changes the SWR.  May also try a different antenna that might get the reflection away from the body.  I had thought of using a trunk lip mount and putting that on the hood of the Jeep.  The top is fiberglass so would not provide any real benefit (other than perhaps getting the antenna away from anything on the Jeep!).  This antenna is on a NMO mount so changing out the antenna would be rather easy.  Relocating will be a bit more work, but I have a spare cable to work with too.

Make sure the lip-mount offers full tilt/swivel features. A pure/simple "trunk-lip" mount expects a horizontal lip. Your hood lip is vertical, so the mount has to swivel  so the antenna is not sticking out the side. The MFJ I'd linked to https://www.hamradio.com/detail.cfm?pid=H0-013622 comes with coax (though I'm not thrilled at the RG-58 losses at UHF). You'd swivel the bottom to put the hinge parallel with the other edge of the lip-mount, then tilt it up to get a vertical antenna.

[WRMD235]

Thanks KAF6045.  I was actually thinking about using the trunk mount on the top of the hood near the cowl in the center of the hood lip.  Might also think about mounting some sort of metal ground plane to the fiberglass roof and getting it up there.  Depends on if I want to take off the top some day or not.

[marcspaz]

I'm out with my wife and grand daughter right now... so I haven't read everything yet. I apologize if I'm missing something. I'll swing back and read the thread in detail when I'm home.

 

I did glance through and I can tell you with 100% certainty that there is no chance for that antenna to work well were it is located. 

 

I have owned Jeeps most of my life. Every Wrangler I have owned since 2010, I have used a Diamond or Comet lip mount and it is always adjusted to its highest point and at least 7 to 8 inches away from the A Pillar.  JL and JT vehicles have a plastic corner cap, so the mount should be a touch further forward than on the JK models. 

 

The one I have been using with great success for the past 4-5 years is the CP-5NMO from Comet. 

 

My previous Jeep...

[KAF6045]

17 minutes ago, WRMD235 said:

Thanks KAF6045.  I was actually thinking about using the trunk mount on the top of the hood near the cowl in the center of the hood lip.  Might also think about mounting some sort of metal ground plane to the fiberglass roof and getting it up there.  Depends on if I want to take off the top some day or not.

I was concerned about clearance when opening the hood -- but the Wrangler series maybe has enough (considering they also [used to] support folding down the windshield).