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Does different coax affect swr?

rabbiporkchop said:
Since purely resistive 50 ohm mobile quarter wave antenna doesn't really exist, how are you getting 50 ohms to the transmitter with the quarter wave impedance Transformer ?
Are you using a tuner or some other matching method?
Click to expand...

A 1/4 wave length transmission line will invert the antenna impedance a d not repeat it so using a 1/4 wavelength line is wrong to begin with. Secondly a 50 ohm mobile antenne certainly does exist. That's what the base coils are for....impedance matching. In the case of a 1/4 wave antenna the radiaton impedance PLUS ground losses can add to 50 ohms. In fact most people think that is the ultimate natch for a 1/4 wave mobile antenna when in reality it is not. In the end it is quite possible to have a mobile antenna that measures a perfect 50 ohms at the feedpoint.
 
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Captain Kilowatt said:
A 1/4 wave length transmission line will invert the antenna impedance a d not repeat it so using a 1/4 wavelength line is wrong to begin with. Secondly a 50 ohm mobile antenne certainly does exist. That's what the base coils are for....impedance matching. In the case of a 1/4 wave antenna the radiaton impedance PLUS ground losses can add to 50 ohms. In fact most people think that is the ultimate natch for a 1/4 wave mobile antenna when in reality it is not. In the end it is quite possible to have a mobile antenna that measures a perfect 50 ohms at the feedpoint.
Click to expand...
I'd love to see some examples.
with my Wilson 5000 roof mount x equals zero and R equals 50 do not occur at the same time.
R equals 42 and x equals zero is the best I can get
 
rabbiporkchop said:
I'd love to see some examples.
with my Wilson 5000 roof mount x equals zero and R equals 50 do not occur at the same time.
R equals 42 and x equals zero is the best I can get
Click to expand...

Just become YOU don't have that result does not mean others have not nor does it mean it is not possible. Every mobile installation is unique as ground losses are extremely variable.
 
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I was having a lot of problems with picket fencing and oscillation. I put LMR 240 for my jumpers and mini 8 for my coax from my antenna. I also put a shorter jumper from the radio to the amp and made the coax to the antenna longer. No issues now, steady signal and 1.2 swr's with the box on or off. I can go close to 12 meters and close to 10 meters before there is any significant changes. So if you have any problems with swr's, picket fencing (signal wobble) or trouble getting your carrier right, try changing the coax length before and after the amp. Also don't mess with RG58, it is crap and causes things like stray RF and unwanted interference.
 
rabbiporkchop said:
Since purely resistive 50 ohm mobile quarter wave antenna doesn't really exist, how are you getting 50 ohms to the transmitter with the quarter wave impedance Transformer ?
Are you using a tuner or some other matching method?
Click to expand...
Its not perfect, there is some mismatch. Captain nailed it.

Captain Kilowatt said:
A 1/4 wave length transmission line will invert the antenna impedance a d not repeat it so using a 1/4 wavelength line is wrong to begin with.
Click to expand...
 
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tba02 said:
Oh, I understood. I wasn't aware that Wilson was so precise with regard to coax length and velocity factor such that a perfect 180* phase shift for "that" specific frequency was possible out of the box.
Click to expand...
180° of times microwave LMR 240 does not come directly from Wilson.
It was added after I made the purchase.
 
Hey RPC can you tell me a little about your installation?

What was wrong with the antenna and how was the antenna working before you had the coax changed?

What frequency was your antenna tuned for?

How long was the stock Wilson cable, the type of coax, and VF?

How long was the LMR that you had installed on your Wilson?

What happened that was different...after you had the coax changed to LMR?
 
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