Coax length?

[Tallman]

I love the assumptions being made...

Here, let me put your mind at east as you have clearly not seen the many times I have talked about such things in the past.

No, I not only not not think, but I know that a receiving station won't notice this difference. But then, that wasn't the goal or point of my post to begin with...

I was simply trying to show a potential difference in a way that someone who is not as technically minded as some of us could understand, and use that as a springboard to ask for more information so we can provide better guidance.


The DB

Would the receive be affected more than transmit? Weak signals lost in the noise?

 

[The DB]

Would the receive be affected more than transmit? Weak signals lost in the noise?

The thing is, while the weak signal is affected by coax length, so is the static level, and as long as they are on the same frequency they are affected equally. So if a signal is lost in noise, for that antenna that signal will always be lost in noise, unless you do something about the noise itself (grounding, remove QRM via filters or turning something off, changing the antenna to one that is naturally more resistant to noise, ect).


The DB

 

[El Kabong]

I was just swapping out the crappy RG58 coax on my Wilson 1000 mag mount with 8X when I thought I would test something. I measured the stock cable's length and did the math with the velocity factor. It matched. So, Wilson believes in the old coax length thing too.

 

[543_Dallas]

I was just swapping out the crappy RG58 coax on my Wilson 1000 mag mount with 8X when I thought I would test something. I measured the stock cable's length and did the math with the velocity factor. It matched. So, Wilson believes in the old coax length thing too.

This coax length thread was more about how much can I use instead of how much should I use. Wilson probably used an electrical half wavelength of coax. The benefit to this is that it reproduces the feed point impedance of the antenna at the swr meter. That doesn't make the antenna work any better but takes away one variable for a novice trying to tune an antenna.

You could have a very badly matched antenna and find a sweet length of coax that shows you a low swr reading. You still have a poor antenna with a happy meter. The idea of using the electrical half wavelength of coax is to prevent this from happening.

Once you have the antenna tuned and the feed point impedance is close to 50 ohms you will not see different swr readings by changing coax lengths. Common mode current can complicate things but that's another topic.

 

[Martian]

Buy @543_Dallas a beer.