A thread that will never die

So where does the 180' come in?

 

As was already stated, coax length can be very important such as in a NGP antenna system. Coax length matters if its part of the antenna system itself.

Coax length doesn't matter to a point. You do not want to make it too short as you can have issues if you do. If you make it too long you'll lose transmission power at the end.

The 180 degrees has to do with the phase of the radio wave. There is a nice GIF in this thread showing how they go.

 

Yes your correct, I guess at the time I used the word tune since it's what most people relate to when adjusting their antenna. Of course your matching the antenna to the radio.

 

That's interesting... you must have ears like a canine. I don't think I've ever heard of anyone being able to separate or being able to distinguish the difference between peoples voices due to coax length.

 

I think you are mistaken. Since coax is usually modeled after a 1/2 wave length section for SWR, you have to remember to use the velocity factor and frequency too. I don't think you would want a 180 foot of coax in your truck. At least not on the 27mhz band.

 

On coax you have current and voltages that are known as standing waves. Basically you are trying to match the current and voltages at the radio and the antenna ends of the coax, so they have the same impedance. That's roughly the general idea anyway. The thing to remember is, the coax length important for SWR measurements is the electrical length, not the physical length.

Although, some may argue that cutting the coax to the correct electrical length, is technically cutting the physical length to get the correct electrical (velocity factor) length. Oh man, now my head hurts thinking about it. lol.

 

I was referring to electrical degrees not physical distance.

 

There's a lot in that book that you never studied. It shows you how to make quarter wave stubs and all sorts of stuff

 

If you gave me your radio and told me to install it in my vehicle I would not be able to notice the difference by changing cables. However if I gave you my radio and I installed it in your vehicle you would be able to notice the difference if changing between different cables. So the guys that say coaxial length does not matter they are correct that the average person would never notice a difference in the receive. I can still hear very well even with random cables but when multiple stations talk simultaneously I hear a squealing sound that I would not normally hear if I had the right cable connected to my antenna system.

 

Okay, my mistake. Craig posted he was confused about the 180 degree theory, and he said surely you don't mean 180' (feet). You said "yes I do" to his 180' statement with the automated standing wave. That's why I misunderstood.