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Author Topic: Folded dipole for satellite operation.  (Read 255 times)

VE2LG

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Folded dipole for satellite operation.
« on: August 08, 2022, 10:49:37 AM »

I plan to build a folded dipole for satellite operation. (432Mhz)

 I also planning using balun formula for ~50 ohms matching made with coax.
 If I'm correct, 200 or 300 ohms is the aprox Z of that type of driven element.
 Should be (4:1) or (6:1) balun?
  Any idea...    Real VE2LG
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WA3SKN

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Re: Folded dipole for satellite operation.
« Reply #1 on: August 08, 2022, 11:56:14 AM »

Is this for the transmit side, receive side, or both? What power are you planning?

-Mike.
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K5LXP

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Re: Folded dipole for satellite operation.
« Reply #2 on: August 08, 2022, 01:03:47 PM »

You can plan on it, but I wouldn't expect to make many contacts with it.  There's just not enough downlink strength to make that a useful solution.

Mark K5LXP
Albuquerque, NM
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WB6BYU

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    • Practical Antennas
Re: Folded dipole for satellite operation.
« Reply #3 on: August 08, 2022, 01:27:53 PM »

The 4 : 1 coax balun is the simplest.  Make sure your
balun designs are specifically for 70cm, rather than
trying to adapt HF designs.

The impedance of the folded dipole depends on the
environment, as well as the ratio of the diameters of
the two conductors.  If you are backing it up with a
reflector to get more gain, then adjust the spacing
to get a 200 ohm Same if the antenna is mounted
beside a metal mast.

As the driven element of a yagi, design the yagi for a
12.5 ohm impedance, and the folded dipole will step
that up to 50 ohms so you can use a 1 : 1 balun.


So the rest of your antenna system and environment
will affect the feedpoint impedance of a folded dipole.
And, if it still ends up with an inconvenient impedance,
then you can use a thicker conductor for one side of
the folded dipole to improve the match.

VE2LG

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  • Posts: 6
Re: Folded dipole for satellite operation.
« Reply #4 on: August 09, 2022, 09:38:44 AM »

Is this for the transmit side, receive side, or both? What power are you planning?
-Mike.

It should be for both application..
 I already have satellite antenna made with "gamma" match. (home made)
   (QSO made in Europe in 2016 with FO29)    VE2LG
 
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WA3SKN

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Re: Folded dipole for satellite operation.
« Reply #5 on: August 11, 2022, 09:34:05 AM »

"Is this for the transmit side, receive side, or both?"
I asked this because the question involved impedance.  The "load" determines the impedance... in transmit the load is the antenna, however... in receive the load is the receiver.  And the 4:1 ratio is only when using the same diameter wire.  Most don't know you can vary the ratio up to about 25:1 just by changing wire diameters.
And I try and use a quarter wave stub so I can tune the antenna a bit for matching.  There is no real gain to the folded dipole, but it can be grounded for "plumbers delight" construction.  Not much of a target for lightning at 432 MHz though!

-Mike.
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