Why would the ohms on a 102 inch whip be 42 in 27 megahertz and 50 in the 26 megahertz?? confused!!!!:headbang
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ohms
- Thread starter undertaker
- Start date
Mounting location and configuration can affect the resonant frequency. It appears yours has shifted downward a little bit. Still 42 ohms is not bad at all. That is only an SWR of 1.19:1
And that 'ohms' isn't only resistance. It's also reactance which is frequency related. The combination of 'resistance' and reactance makes up impedance, which that 'ohms' is describing. 'AC' resistance and 'DC' resistance aren't the same at all. That's why it's so conf... 'fun'!
- 'Doc
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RatsoW8
Supporting Member, W9WDX ARC Member - WD8T
For any given antenna and transmission line (for CB /Ham radio) R and X are going to be different. I gues the near perfect resonant antenna for our use would be R=50 ohms and X = 0. My dummy load (cantenna) is R=47 ohms and x=2. You're pretty good.
add a spring or something to make it 108" and the ohms will be closer to 50 on 27Mhz...SWR will probably be lower also...pending on mounting location and grounding to tho...
How long is the coaxial you are using to measure ohms? What type of feedpoint are you using? What is the relationship between the hole you drilled to the center conductor passing through the body of the vehicle? Changing the hole size changes your feedpoint impedance. Changing coax length changes perceived impedance at the transmitter, although feedpoint impedance remains the same.
Changing the thickness of your ball mount insulator changes feedpoint impedance also.
Characteristic impedance is determined partially by distance from center conductor to ground. Every install I complete has a feedpoint impedance of 48-52 ohms, same impedance at the amp, and same impedance at the radio.