Antenna from GI JOES

[Master Chief]

Its a good thing I have a 269 then. Believe it or not, I actually know how to use and read it too!

However, you make a good point about my use of the word, "resonance". You like picking apart my posts for some reason.

But, the antenna IS resonant and works great. The SWR is flat right at 27.205 which is where I TUNE the antenna. The 2:1 SWR points are equal (in relation to bandwidth) at both ends of the spectrum and the people I do this for couldn't be happier.

Thanks for your continued support.

 

[Captain Kilowatt]

Freecell's just being a picky perfectionist again The rest of us understand what you meant. Having said that however Freecell is correct. I had an antenna for 80m that was perfectly resonant at 3760 and the SWR was 3:1.The reactance was zero but the R was around 145 ohms.I also had a mobile antenna that had an SWR of around 2:1 but it was near 50 ohms but it was also reactive.Perfect SWR and resonance are not necessarily coincident.

P.S. I love my MFJ-269

 

[radioreddz]

Got the antenna from gi joes and yes it is a maco v5/8. But you know the price was right and all i have heard about these antennas are they are very good...

is the box actualy marked from maco mfg. i know that H & Y electronics sells an antenna they say is just like the Maco V58 with a picture that looks like the Maco for $54.95 they also have the V58 @ 71.95 & the V5000 @ $109.95. sounds like a great deal for a maco. you will love it.

 

[freecell]

"But, the antenna IS resonant and works great. The SWR is flat right at 27.205 which is where I TUNE the antenna."

if vswr = 1:1 @ 27.205 then it's matched.

if X = 0 @ 27.205 then it's resonant.

 

[Master Chief]

10-4

 

[Robalo]

so let me see if I got it

27.205

R = 0

X = 0

Z = 50

Bingo i have perfect CB antenna . Right !

 

[freecell]

wrong.

 

[Robalo]

so please quote me numbers. 27.205 R = ? X = ? Z = ?
for perfect antenna. and i will do my homework. i have a new mfj-259b Thank you. Robalo 73's

 

[freecell]

Z = sqrt( (R^2) + (X^2) )
if R = 50 and X = 0 then Z = 50

here's a sample: let's suppose that R = 32 ohms and X = -15 ohms, solve for Z....

R is Resistance
X is Reactance, - is capacitive and + or no sign is inductive
Z is Impedance
all values are expressed in ohms

R = 32 and X = -15, solve for Z

Z = sqrt( (R^2) + (X^2) )

Z = sqrt( (32^2) + (-15^2) )

Z = sqrt( (1024) + (225) )

Z = sqrt(1249)

Z = 36.341

when R = 32 ohms and X = -15 ohms then Z = 36.341 ohms.

 

[W5LZ]

Maybe a different perspective would be of benefit.

There are always two 'steps' in tuning an antenna, making it resonant and matching it's input impedance. Resonance is done by fiddling with the antenna's length (mechanical or electrical). Matching impedances can be done several ways, but it's basically by using an impedance matching 'device' of some kind.
Some times, one of those two steps is already done, or is so close that it doesn't much matter. Some times, even both are 'close enough' and you hit it lucky! But both steps are required for tuning an antenna.
- 'Doc

 

[freecell]

then you're missing two........
any questions about the math Robalo?

 

[W5LZ]

Pray tell... which two am I missing?
- 'Doc

 

[Robalo]

this is the way i'm seeing it:
z= sqrt [ (r^2) + (x^2) ]

R=50 & x=0

Z= sqrt [ (50^2) + (0^2) ]
Z= sqrt [ (50^2) + (0) ]
Z= sqrt (50^2)

(sqrt) and (^2) cancel each other out so Z=50

so a perfect antenna
SWR=1.0
R=50
X=0
Z=50

 

[W5LZ]