Very High SWR

[rfradioconsult]

Sadly most folks put too much stock in their SWR meter, if you see a high SWR reading, then back up get your DVM out and check for continuity where it should read correctly and where it should indicate an open. Once you have eliminated the connectors, coax and you have continuity from the tip of the connector to the actual antenna mast, then start by looking out how the antenna is mounted. As others have posted a CB antenna require a large ground plane to work against; a ground wire from the mount to the vehicle body will not work. You can cut or add to the antenna length and may find a low SWR point but you are just fooling the radio you haven't fixed the problem. A low SWR is no measure of an antennas overall efficency!

 

[Ohio_359]

You can cut or add to the antenna length and may find a low SWR point but you are just fooling the radio you haven't fixed the problem. A low SWR is no measure of an antennas overall efficency!

Yes, the length has everything to do with the resonant frequency. Here is my W1000 thru-hole mount on my Dodge. I can lengthen/shorten the stinger and move the SWR up/down the band which is directly related to the reactance of the antenna.

If he is seeing higher SWR on 40 than 1, he needs to shorten it until he finds a "dip" and can move that dip to19.

Also, the mount will work. It's not my antenna or location of choice, but if the rack, bed, cab and chassis are bonded together, it'll work.

 

[Ohio_359]

Adding/removing cable length is a placebo when it comes to antenna installs and SWR.

Nobody said anything about cable length did they? I missed it.

 

[UberGeek]

Nobody said anything about cable length did they? I missed it.

Nope, you didn't miss it. I mis-read the OP, I think. He said "adding length to it", and I thought he meant cable... Later posts showed he meant "antenna".

My bad. Please ignore my diatribe on coax length

 

[wyomingmedic]

Yes, the length has everything to do with the resonant frequency.

But resonant frequency has nothing to do with efficiency. A dummy load has a GREAT SWR and therfore a resonant frequency of everywhere? But it radiates for crap.

The problem with adjusting his WHIP (not stinger, a stinger is another part of an antenna) is he MAY not be able to find a point of low SWR. Because of his mounting location, the SWR may never be that great.

He needs to NOT cut randomly on his whip. He needs to determine if the mount is the problem. Understand what you are doing BEFORE you do it.

WM

 

[Speedy78]

I have a friend with a wilson 1000. I'm goin to try that in the center of the cab because that will be the easiest to do first.

 

[Ohio_359]

But resonant frequency has nothing to do with efficiency. A dummy load has a GREAT SWR and therfore a resonant frequency of everywhere? But it radiates for crap.

A dummy load is a 50 ohm load with no reactance, apple to oranges.

 

[rfradioconsult]

An antenna at resonance the Xc and Xl cancel each other and the resistive component is left. I say again SWR is not a measure of antenna efficiency; also a further hint a 1/4 wave antenna over a good groundplane is not 50 Ohms.

 

[Ohio_359]

Okay, but how did you guys get off on the efficiency tangent anyway? A full 1/4 wave and a center loaded antenna can both have an SWR of 1.5:1, but the 1/4 wave is going to be more efficient. But what does that have to do with the price of eggs?

We are looking for resonance, not efficiency.

 

[LtDoc]

"We are looking for resonance, not efficiency."

Yes, I'd agree with that in general. But there's a "but" in there. An SWR meter can't tell you anything about resonance, only the impedance matching. In fact, an SWR meter can't 'honestly' tell you much about impedance matching unless there's some additional 'knowledge' thrown at it. How many "R +/- J"s are there that will make an SWR meter read '1:1' ?
- 'Doc

 

[Ohio_359]

How many "R +/- J"s are there that will make an SWR meter read '1:1' ?
- 'Doc

Many, many combinations.

 

[Speedy78]

Put a mag mount antenna on the roof and got SWR of around 1.6. Put the Monkey Made in the mag mount (barely held it standing up haha) and got a SWR of around 1.4-1.5. I believe that means I had a bad ground plane on the previous mounting location. Am I correct in this assumption?

 

[rfradioconsult]

From your description of your elevated mount you had no groundplane. A sngle piece of wire does not a groundplane create.

 

[marconi949]

From your description of your elevated mount you had no groundplane. A sngle piece of wire does not a groundplane create.

My A99 didn't come with a groundplane,but i see i can get one for it.
I read it helps radiate my signal equally in all directions,if anything else what else does it improve.

Marconi949

 

[Ohio_359]

My A99 didn't come with a groundplane,but i see i can get one for it.
I read it helps radiate my signal equally in all directions,if anything else what else does it improve.

Marconi949

The A99, Imax2000 etc are different. A mobile antenna not only needs grounded, it needs to be completely bonded together so the cab, bed, fenders etc appear to be a single unit (ground plane) to the antenna.

 

[kf7yn]

Please read up and not rely on opinions posted here that may or may not be accurate. These websites have good info: KØBG.COM and The Ultimate Guide to 11 Meter CB Antennas and of course the ARRL handbook is always a good source.

73's

 

[wlightning36]

High swr,s

Hello i,m white lightning, most all the time you have high swr,s start with grounding issues, and length of coax,and mounted area for ant,..! what type of coax do you have and what type of system are you trying too set up ! 11 meter 10 meter or what?

 

[LtDoc]

That "bad ground" thingy is very, very misunderstood, and not what you think it is to start with. A "ground" has more than one meaning, and when you get into RF thingys, that meaning is usually incorrect. Think of that 'ground' as the other half of the antenna, it's a better way of describing what you are talking about.
For a mobile antenna that 'ground', or the other half of the antenna is typically the vehicle's metal body. You have to adjust the vertical part of the antenna so that it "matches"/'equals'/is compatible with it's 'other half'. If there isn't a 'balance' struck, it just isn't going to behave as you would expect. If the tire doesn't fit the rim, you got a wheel that doesn't work so good. You can make an out-of-round rim work with an out-of-round tire if you put them together correctly, and -if- that out-or-roundness isn't too drastic. May not be easy, but it can be done. Same with most antennas if they are 'close enough'. The hard part is finding out why that antenna isn't as "round" as it could be, then correcting that if possible.
- 'Doc

(SWR is the worst means of 'measuring' an antenna's worth. It's so over rated that it's really unbelievable.)

 

[pjtnascar]

Either get a large magnet mount to support the big antenna, or drill the hole in the roof and make sure the antenna has good contact with the body. Forget all of the other nonsense here. The guy just bought an antenna, so unless he can return it, I doubt he's gonna blow more money on a new one. He wants what he has to work, not suggestions for what he should have bought.

 

[wlightning36]

Hello all, Ok i,m aparently not understanding the purpose for this site! I replied too someones post about them asking how they could get a better standing wave ratio(swr) because they where having problems getting them adjust too safe range!
I answered them with different suggestions and possiblities and i feel like i got replie by someone basicly telling me i didn,t know what i,m talkin about! Now granted i do not know all and or everything there is too know about anything but radios and there intire systems as far as 11 meter i do know a bunch! ( but i still learn everyday) and i,m not afraid too learn either!

I have been rebuilding repairing and tuning radios for several years with great reviews from various people so i guess i,ll just be quiet and watch and learn what this site is really for for a while too understand better before i post anything else!