| Author |
Message |
    
Dale
Senior Member
Username: Dale
Post Number: 1916
Registered: 12-2002
| | Posted on Thursday, January 03, 2013 - 3:00 pm: | 
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been playing around with this. think i understand it now
x=reactance
r=ohms
so on my mobile setup is wilson 1000 with longer stinger x=0-1 r= 80 ?? , swr 1.5-1.7
this was the best i could get the standard 62 inch whip lowered the ohms close to 50 ohms.BUT raised my ohms R to R=79-80.when i first got it my understand was to tune the antenna to get a 50 ohm load or R=50 or close.but after talking to some locals here i wanna tune out the reactance or X
so now im back to confused and why did my ohms
jump so far outta wack.
dale/a.k.a.hotrod
cef426
cvc#64
454 [dx numbers]
38lsb
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Tech833
Moderator
Username: Tech833
Post Number: 2233
Registered: 8-2002
| | Posted on Sunday, January 06, 2013 - 2:41 pm: |
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Reactance should be j0 and resistance should be 50 ohms for a 1:1 SWR.
Reactance is actually more important to an antenna's performance than impedance (ohms). You see, ohms is a measurement of the load the transmitter expects to see and the load it does see. We know that most CB radios expect to see a resistive load of 50 ohms, therefore we want to match our cable and antenna to the same value.
Reactance is actually a way of seeing the resonance of the antenna feedpoint (simplified answer). An antenna that shows 0 ohms reactance is neither capacitive nor inductive. So, the antenna with 0 ohms reactance is considered resonant at the measurement frequency since the inductive and capacitive components cancel each other out.
You can have an antenna with 20 ohms resistance and zero ohms reactance that still works very well as an antenna. You can have an antenna with a 50 ohms resistance but a large reactance component that works crummy as an antenna, even with an antenna tuner.
For optimum bandwidth and performance, strive for a low reactance ("X") and get the resistance ("R") in the ballpark.
Your radio 'Mythbuster' since 1998
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Dale
Senior Member
Username: Dale
Post Number: 1918
Registered: 12-2002
| | Posted on Sunday, January 06, 2013 - 8:15 pm: |
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thanks tech 833. that helped me very much
just to see if i understand ya corrctly
its better to tune for 0 reactance or X
and have the ohms R in the ball park.as i
posted above i do do have 0 reactance X
and ohm is 75-80little higher than 50 ohms
does this sound ok to you
dale/a.k.a.hotrod
cef426
cvc#64
454 [dx numbers]
38lsb
|
Tech833
Moderator
Username: Tech833
Post Number: 2234
Registered: 8-2002
| | Posted on Tuesday, January 08, 2013 - 1:41 am: |
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If you could get your resistance down to at least 60 ohms, I'd be a lot happier, but you'll still get great performance at 75 ohms as long as reactance is zero.
Your radio 'Mythbuster' since 1998
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Dale
Senior Member
Username: Dale
Post Number: 1921
Registered: 12-2002
| | Posted on Thursday, January 10, 2013 - 8:32 am: |
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i can get the resistance down but as i do
the reactance goes up quickly.i tried to
[balance] the both of them but niether
was close. seems i got one or the other
dale/a.k.a.hotrod
cef426
cvc#64
454 [dx numbers]
38lsb
|
Tech833
Moderator
Username: Tech833
Post Number: 2235
Registered: 8-2002
| | Posted on Monday, January 14, 2013 - 7:13 pm: |
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There must be something in the near field affecting the antenna.
Your radio 'Mythbuster' since 1998
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