Confirm the resonant frequency of this folded dipole
 

Hi. Can anyone please confirm for me the resonant frequency of the folded
dipole below?

(I calculate abt. 159.025 Mhz).

L1
------------------------------------
| | L2
--------------x L4 x---------------
L3 L5

Tube diameter = 10mm

L1: 90Cm; 35.43"; 2.953'
L2: 70mm; 2.76"; 0.230'
L4: 5.8Cm; 2.28"; 0.190'
L3&L5: 42.1Cm; 16.57"; 1.381'

L4 is fixed at 58mm, that is the distance between the bolts where the
dipole attaches at the feedpoint. I guess I'm ignoring the connections
within the plastic connection box, that would perhaps add 2.54Cm; 1.00"
; 0.083' to L3 and L5, which I suppose might make L3 & L5 44.63Cm;
17.75"; 1.46'. But is that of any real significance with such a
wide-band antenna. Probably not eh.

BTW, Anyone know of an online calculator specifically written for VHF,
tube-made, folded dipoles? TIA. Rich.

P.S. I'm seeking the dipole to be resonant at 159.025 Mhz.

"Richard" wrote in message
...
Hi. Can anyone please confirm for me the resonant frequency of the folded
dipole below?

(I calculate abt. 159.025 Mhz).

L1
------------------------------------
| | L2
--------------x L4 x---------------
L3 L5

Tube diameter = 10mm

BTW 10mm is 0.394"; 0.033'.

"Richard" wrote in message
...
Hi. Can anyone please confirm for me the resonant frequency of the folded
dipole below?

(I calculate abt. 159.025 Mhz).

L1
------------------------------------
| | L2
--------------x L4 x---------------
L3 L5

Tube diameter = 10mm

L1: 90Cm; 35.43"; 2.953'
L2: 70mm; 2.76"; 0.230'
L4: 5.8Cm; 2.28"; 0.190'
L3&L5: 42.1Cm; 16.57"; 1.381'



As to calculators,I found two, but they are confusing to me.

Not very clear to me how to use this one:

http://n-lemma.com/calcs/dipole/fdipole.htm

Or this one:

http://www.optcom.net.au/wireless/folded_dipole.html

Richard wrote:
Hi. Can anyone please confirm for me the resonant frequency of the folded
dipole below?

No, if we all made one, they would all have slightly different
resonant frequencies. If you want one that is right on frequency,
you have to trim it to that frequency and then don't change
anything about it or its environment.
--
73, Cecil http://www.qsl.net/w5dxp



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"Richard" wrote in message
...

"Richard" wrote in message
...
Hi. Can anyone please confirm for me the resonant frequency of the
folded
dipole below?

(I calculate abt. 159.025 Mhz).

L1
------------------------------------
| | L2
--------------x L4 x---------------
L3 L5

Tube diameter = 10mm

L1: 90Cm; 35.43"; 2.953'
L2: 70mm; 2.76"; 0.230'
L4: 5.8Cm; 2.28"; 0.190'
L3&L5: 42.1Cm; 16.57"; 1.381'



As to calculators,I found two, but they are confusing to me.

Not very clear to me how to use this one:

http://n-lemma.com/calcs/dipole/fdipole.htm

Or this one:

http://www.optcom.net.au/wireless/folded_dipole.html


Richard

Thanks for the references to the folded dipole calculator sites. If you
dont have the calculators figured out, you are welcome to E-mail me. They
seem OK to me.
I've been building some dipoles for 137MHz and have 'grid dipped' some
lengths for dipoles that indicate that your dimensions are very close to
correct.
Do you have any doubt that the antenna you describe will radiate well at
159 MHz?

Jerry

If the elements are of different diameters, example 0.5 inches and 0.375
inches there are differences in Zo and slight differences in Fo.

To a first approximation I calculate 158.5 MHz as resonant point. That
may have a 2 to 3 percent error due to endeffects, L/D ratio etc.

Your calculation is a good as mine.

DD, W1MCE

Richard wrote:

"Richard" wrote in message
...

Hi. Can anyone please confirm for me the resonant frequency of the folded
dipole below?

(I calculate abt. 159.025 Mhz).

L1
------------------------------------
| | L2
--------------x L4 x---------------
L3 L5

Tube diameter = 10mm

L1: 90Cm; 35.43"; 2.953'
L2: 70mm; 2.76"; 0.230'
L4: 5.8Cm; 2.28"; 0.190'
L3&L5: 42.1Cm; 16.57"; 1.381'




As to calculators,I found two, but they are confusing to me.

Not very clear to me how to use this one:

http://n-lemma.com/calcs/dipole/fdipole.htm

Or this one:

http://www.optcom.net.au/wireless/folded_dipole.html

Are you deluding yourself about the degree of accuracy required?

An error of 1 MHz in 159 MHz would make no detectable difference in
behaviour or performance.