Questions for antenna gurus.....

[stealth6]

........or at least for anyone more knowledgeable about them than I am.

First issue - See this mockup:


"A" is a standard BRB 70cm tracker with a wire whip antenna (attached via SMA). If, due to space issues, I wanted to hook up the antenna with a small connector cable as in "B" or "C" (the red line would be the connector), I'm assuming this is doable, yes? What are the problems I need to be aware of before doing this? More importantly, what EXACTLY do I need for the connector cable? What should I avoid? Would there be a significant advantage/disadvantage between configurations "B" and "C"? I'm assuming that any answers here would apply the same way if I was using a "rubber duck" antenna instead of the wire whip, yes?

Second issue:
This is concerning a standard RDF system (non-GPS). The cable I have between my radio/HT and my yagi is too long - 48" in fact. In use, I have to make two or three coils to take up the slack. Is this causing problems other than just the extra length being unwieldy? Meaning, is this cable acting as an antenna in itself, and a non-directional one at that? Do the coils add to the problem? I do want some length and flexibility between the HT and the yagi due to the fact that sometimes I'm holding the antenna in an odd position/orientation that would make it difficult to see the S-meter on the radio if the two were attached solidly - but how much (if any) is too much?

thanks for your help and advice,
s6

 

[zanfar]

"A" is a standard BRB 70cm tracker with a wire whip antenna (attached via SMA). If, due to space issues, I wanted to hook up the antenna with a small connector cable as in "B" or "C" (the red line would be the connector), I'm assuming this is doable, yes? What are the problems I need to be aware of before doing this? More importantly, what EXACTLY do I need for the connector cable? What should I avoid? Would there be a significant advantage/disadvantage between configurations "B" and "C"? I'm assuming that any answers here would apply the same way if I was using a "rubber duck" antenna instead of the wire whip, yes?

Yes, this is very doable.
You should look for a cable with matching connectors, and a Characteristic Impedence that matches the tracker / antenna (probably 50 Ohms). The tracker manufacturer is probably the best resource for this question.
As a monopole antenna, you will get roughly the same performance pointing up as down, with maybe a little better signal in the direction the antenna is pointing (my emag is failing me bit here on a monopole without a ground plane).
A rubber duck should respond the same way to the extension cable.

In use, I have to make two or three coils to take up the slack. Is this causing problems other than just the extra length being unwieldy? Meaning, is this cable acting as an antenna in itself, and a non-directional one at that? Do the coils add to the problem? I do want some length and flexibility between the HT and the yagi due to the fact that sometimes I'm holding the antenna in an odd position/orientation that would make it difficult to see the S-meter on the radio if the two were attached solidly - but how much (if any) is too much?

If the cable is coax, and your receiver and antenna are well-designed, the cable should not be acting as an antenna itself.
The coils will act as an inductor, which, depending upon the number and size, might affect the performance. However, probably not much. Best case is no coils, but if necessary, make the loops large and try to "flatten" so they are more of a back-and-forth (without stressing or kinking the cable, of course).
The correct length of extension cable is exactly the amount you need.

There's your E-Mag I and II in a nutshell

 

[RocketDestroyer]

If the cable is coax, and your receiver and antenna are well-designed, the cable should not be acting as an antenna itself.
The coils will act as an inductor, which, depending upon the number and size, might affect the performance. However, probably not much. Best case is no coils, but if necessary, make the loops large and try to "flatten" so they are more of a back-and-forth (without stressing or kinking the cable, of course).
The correct length of extension cable is exactly the amount you need.

I would just wind it up into a coil and not try to flatten it. Any inductance in the turns of coax will not be an problem and under some conditions might actually be a benefit. Otherwise agree with everything zanfar told you.