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High SWR
- Thread starter Nick hatz
- Start date
Yes it is. Now I'm going to give you some good news. The reason the SWR is high is because you've actually got a good RF ground. I'm betting that the SWR is lower on Ch1 than Ch40. If so that's definitely the case and you'll need to cut the whip. I have a very good RF ground on my vehicle and I typically end up having to shorten the whips by 2-3" with a Dremel as mine usually end up resonant out of the box just below 26MHz. Manufacturers make mobile antennas assuming a poor ground, i.e magmounts or bumper mounts. The more efficient the RF ground the shorter the antenna needs to be for any given frequency. With an excellent one you end up needing to shorten it more than the adjustment in the antenna allows.
If you want some verification then borrow an antenna analyser from someone or buy one of the cheap Nano-VNAs. Do a sweep from 24MHz to 27MHz and I'm betting you'll find a 1:1 SWR or very close to it below the CB frequencies, maybe around 26MHz or so.
I’ve never done any bonding on any vehicle other than two straps on the hood of my pickups. Have a roll of braid sitting here...but every time I get the ambition to do something there’s some propagation that gets in the way.
I wish I had the experience on the topic to quantify the value in thoroughly bonding a vehicle, but I simply don’t.
For the OP, I’d probably add exploring that topic to my short list.
But, I’d be working on the antenna match first, even if ultimately related. He should be able to get a better match than he is seeing without much effort.
The biggest issue in my eyes is deciding whether to tune for SWR or resonance. The topic of many discussions on this board, and with info very plentiful.
I remain of the mindset that tuning for SWR on a mobile CB antenna is more than adequate. If the OP wants that, he needs only shorten then antenna.
But if wants to tune for resonance, then he needs an analyzer or VNA. I suspect this will also require shortening the antenna.
With a 1/4 wave mobile antenna, I have a hard time believing that either method would produce results different enough to be detectable on the receiving end.
My install with a whip turned out to where zero reactance is also very close to 50ohms. So, we know I don’t have a “perfect” ground plane, which would be what...37ohms at resonance?
But I don’t except to have a perfect ground plane...it’s shaped like a pickup truck, after all.
I wish I had the experience on the topic to quantify the value in thoroughly bonding a vehicle, but I simply don’t.
For the OP, I’d probably add exploring that topic to my short list.
But, I’d be working on the antenna match first, even if ultimately related. He should be able to get a better match than he is seeing without much effort.
The biggest issue in my eyes is deciding whether to tune for SWR or resonance. The topic of many discussions on this board, and with info very plentiful.
I remain of the mindset that tuning for SWR on a mobile CB antenna is more than adequate. If the OP wants that, he needs only shorten then antenna.
But if wants to tune for resonance, then he needs an analyzer or VNA. I suspect this will also require shortening the antenna.
With a 1/4 wave mobile antenna, I have a hard time believing that either method would produce results different enough to be detectable on the receiving end.
My install with a whip turned out to where zero reactance is also very close to 50ohms. So, we know I don’t have a “perfect” ground plane, which would be what...37ohms at resonance?
But I don’t except to have a perfect ground plane...it’s shaped like a pickup truck, after all.
I’m going to get the Analyzer.
Removed all the paint from under the mount bare metal. Grounding strap was added earlier,And bonded the frame to the bed in four corners. No change.
without an analyzer or decent equipment I’m at a standstill. I don’t want to cut the antenna until I have the analyzer.
like I said I can transmit and receive people all over the country today.
Removed all the paint from under the mount bare metal. Grounding strap was added earlier,And bonded the frame to the bed in four corners. No change.
without an analyzer or decent equipment I’m at a standstill. I don’t want to cut the antenna until I have the analyzer.
like I said I can transmit and receive people all over the country today.
BJ radionut
Supporting Member and 6m addict
ALL the bonding in the world will NOT change the VSWR if the antenna is too long.
I am not sure what analyzer you are going to get, but if it's one of those Chinese clones..you do realize those must be programmed and calibrated with a computer and dummy load before using. At least most of the ones I have seen for like less than $100 are that way. Could be I have misread info, but my understanding they are not plugged and play ready.
I am not sure what analyzer you are going to get, but if it's one of those Chinese clones..you do realize those must be programmed and calibrated with a computer and dummy load before using. At least most of the ones I have seen for like less than $100 are that way. Could be I have misread info, but my understanding they are not plugged and play ready.
My NanoVNA came with calibration plugs...an open, a short, and a 50ohm.
Calibrate AFTER setting the range you plan to use it...and not across DC to daylight.
There is a finite number of test points on the sweep, you don’t want them spread across 800Mhz.
Calibrate AFTER setting the range you plan to use it...and not across DC to daylight.
There is a finite number of test points on the sweep, you don’t want them spread across 800Mhz.
The Dark Side can alter your perception of things sometimes but aren’t truck beds bolted directly to the frame without bushings? All of them I’ve did installs on were this way, maybe I need to remove this helmet and look upon it with my own eyes.
Good point, beds aren’t cabs. Fortunately we don’t have to crawl under our pickups and replace “bed mounts” like we do cab mounts.
Though, the latter problem seems to be mostly a FORD thing. Lol.
BJ radionut
Supporting Member and 6m addict
My Silverado has rubber bushings and spring bolts. They started that (GM) think 91...as it helps reduce noise...The bed does not float but frame/bolts and bed are all coated/painted also before install.
Maybe mine have all had that noise reduction package, the cab is done that way also...Yes correct, I guess???
Maybe mine have all had that noise reduction package, the cab is done that way also...Yes correct, I guess???
BJ radionut
Supporting Member and 6m addict
Could be! I know my XYL made comment when we drove it home couple years ago, that even with a V8 and Z85 Sport suspension that it was quieter on the interstate at 70+mph than her fancy Ford Escape.
Just went and looked The rubber "bushings" look like a flat square pad much like under a large 3 phase transformer we used at work to keep them from vibrating the whole room and pre-cast floors!
DUH...I am dizzy now from crawly under that thing, my balance all messed up from that nerve pinched in my neck!!!
Just went and looked
The rubber "bushings" look like a flat square pad much like under a large 3 phase transformer we used at work to keep them from vibrating the whole room and pre-cast floors!DUH...I am dizzy now from crawly under that thing, my balance all messed up from that nerve pinched in my neck!!!
New (newer, newish, late model and etc) pickups all seem to be a nice ride. Features in cars today blow my mind. Stuff that was only on the top end models is standard in the lowest of low “work trucks” now.
Im a fan of manual stuff. The ‘05 Dodge has crank windows (still haven’t failed). But the manual stuff is getting hard to come by. Even when I bought that truck, in Sep ‘05, they laughed that I wanted a manual trans. Lol...couldn’t make me one if they tried (so they said).
Funny, when I pull up to the base and they approach from the pass side wanting the window down for an ID check...these young guards have never seen a car with manual windows.
Only major component that has failed on the ‘05 Dodge so far: the original auto trans. There was a reason I wanted a shifter on the floor.
Here’s the first ball joint job....15 years and 180k miles. Did a whole front end job while in there.
My 2004 2500 Dodge pickup bed rests on (6) rubber bushings. (3rd Generation model; 2NC995 is 4th or 5th Generation).
I’ll have to look at the ‘05 1500, next time my son allows me to see MY truck.
My Silverado has rubber bushings and spring bolts. They started that (GM) think 91...as it helps reduce noise...The bed does not float but frame/bolts and bed are all coated/painted also before install.
Maybe mine have all had that noise reduction package, the cab is done that way also...Yes correct, I guess???
Bed & Cab are isolation-mounted on every pickup ever made. The frame rail torsion would otherwise quickly destroy them.
Frame Twist is a feature of CLASS 8 as well.