VSWR

[Ramnares P.E.]

Can anyone recommend a good book for a basic understanding of VSWR, what influences it, and mitigation techniques?  Essentially I'm looking for VSWR for dummies.

Thanks in advance!

 

[Bot-Man]

VSWR and impedance matching techniques by Ain Rehman. Not sure if there is a better one but I have this one on the shelf from when I first got started in HAM radio.  Had to google it for the author. Comes up first page on google books. 

 

[Ramnares P.E.]

Thanks for the recommendation @Bot-Man

Picked up a copy and will work my way through it this weekend.

 

[Bot-Man]

Just curious, what kind of transmitter are you setting up? 

 

[Ramnares P.E.]

We have an existing 160MHz antenna around which we installed LMR600 cables for systems that were added to the car.  We have had some problems communication to the on-car radio from handheld radios since the installation and it appears the cables are causing too much interference.  We're going to perform another VSWR/RF study so I'm trying to get a fundamental understanding of this.  Not an excuse but I'm Mechanical so not my area...

 

[Bot-Man]

The systems that were added to the car, are they part of the communications system or unrelated equipment and just causing interference? I ask because normally a high SWR (lower is better) is usually more detrimental to transmission than reception.

Now I’m not electrical either and my knowledge comes strictly from playing with HAM radios. I reached out to a friend who installs, programs and services communications equipment in emergency vehicles. I gave him your problem and asked for his two best diagnostic guesses. Probably won’t get an answer till tomorrow. 

 

[knight1fox3]

This is right up my alley! While working in nuclear, one of the crane systems I designed was picking up interference on the wireless 850MHz controls from an external source. I had to setup a sophisticated monitoring system to look for frequency spikes to prove it to them.

 

[Ramnares P.E.]

This is right up my alley! While working in nuclear, one of the crane systems I designed was picking up interference on the wireless 850MHz controls from an external source. I had to setup a sophisticated monitoring system to look for frequency spikes to prove it to them.

Do you mind if I pick your brain via PM?

 

[Bot-Man]

I heard back from him. He said his best diagnostic is either a bad connection on one of the cables or one of the cables was pinched while installing. He would check the wattage on reflection to verify this. His advice is to pull new cables. He explained that mobiles usually output 30-40 watts and can come through even with a bad cable. A handheld only puts out about 4 watts which would explain why they aren’t able to get through. He said you could call him for assistance if needed.

 

[Bot-Man]

So did you ever get this solved?

 

[Chuk Gleason]

New user, coming late to the party.  

OP, did you get this solved?