CB antenna resistance issue

[chr0nik]

Hi,

I'm relocating some of the antennas that I have and I came across the Gainmaster that I have on a 6m aluminium pole (on a 2m high extension roof) and I plugged it to my meter and it shows as having between 15 to 25 omhs across the 11m band. The coax used is 3m long RG213 cable and the antenna is isolated from the pole.

I'm sure this is not normal as it should be 50omhs but I'm unsure of what might the issue be as I would need to take it all down and re-test.

Also, I have an EFHW for 11m and I'd like to know if this would perform better than a GM if positioned horizontally at around 6m high.

Thanks!

 

[arudlang]

I'm not an expert but I'm looking forward to learning from the much smarter answer that someone else will probably post in here soon.

There is a difference between resistance and impedance, although both are measured in ohms, the average multimeter does not measure impedance so far as I know.

Different antennas may have different measures of resistance but it doesn't mean much unless you know a spec given specifically for resistance for that antenna. My Hy-gain CLR2 measures as a dead short on my standard multimeter and that is how it should look on a cheap meter when reading resistance, it is working perfectly.

A multimeter won't usually tell you much about an antenna. An inexpensive nanoVNA can, if you can put in the time to learn how to use it.

 

[k7ng]

DC resistance is different from RF (high frequency AC) impedance. The only real value a DC meter has for antenna work is to make sure you have installed connectors properly (shield to center not shorted, ground shield continuity, etc.)

Many antennas are a DC short, many are DC open. Any discussion of impedance is too complicated to put here.

 

[bharvey2]

low DC resistance isn't uncommon on some antennas. Don't let that alone worry you. As k7ng mentioned, some will even show a DC short. With regard to the horizontal end fed, keep in mind that it will be horizontally polarized whereas most CB antennas are vertically polarized so there will be some signal loss due to variation in antenna polarization. I know some 11M guys run horizontal antennas looking for long haul communications. If this is your thing, then the caveat doesn't apply.