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Author Topic: counterpoise and binder post?  (Read 413 times)

KG6WNG

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counterpoise and binder post?
« on: August 18, 2022, 10:33:52 AM »

I have an Elecraft KX2 and want to use a 29' random wire antenna for 20 and 40 meters. How long should the counterpoise be, and can I connect it to one terminal of my double binder post/BNC connector, or should I attach the counterpoise to another part of my tranceiver?

Thanks,
Kim
KG6WNG
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K5LXP

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Re: counterpoise and binder post?
« Reply #1 on: August 18, 2022, 11:00:47 AM »

If you have the built in tuner, it's good for a 10:1 mismatch.  So the length of counterpoise you need will depend on the band(s) you want to run.  For the higher bands 10' will probably do, but for 30M and below you may have to experiment to find a length the tuner can match.  Orientation in relation to the elevated wire will affect match as well, so there's no hard answer.

Mark K5LXP
Albuquerque, NM
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W1VT

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Re: counterpoise and binder post?
« Reply #2 on: August 18, 2022, 11:33:14 AM »

https://www.eznec.com/
This excellent antenna modeling program is now free!
It can be used to look at different antenna options.

Zak W1VT
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KG6WNG

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Re: counterpoise and binder post?
« Reply #3 on: August 18, 2022, 12:01:00 PM »

Thanks Mark and Zak. Though I'm still unclear as too whether the double binding post/BNC connector is the appropriate place to connect the random wire and counterpoise.

Kim
KG6WNG
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AE5X

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Re: counterpoise and binder post?
« Reply #4 on: August 18, 2022, 12:23:35 PM »

Though I'm still unclear as too whether the double binding post/BNC connector is the appropriate place to connect the random wire and counterpoise.

Yes, it is.
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K5LXP

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Re: counterpoise and binder post?
« Reply #5 on: August 18, 2022, 12:41:35 PM »

Ideally it would be at the antenna feedpoint and cut to optimum length to achieve a match to the feedline.  It's implied that with a KX2 you'll be operating portable and effectively the feedpoint is right at the radio.  You'd still benefit from optimizing the length based on frequency but again being portable it's not like you'll be swapping wires every time you changed bands.  You hook up what you got, run it best you can and from there the tuner takes care of the rest.  If the goal of making whatever contacts is met, then the details of the antenna and match are secondary.

Mark K5LXP
Albuquerque, NM
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KG6WNG

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Re: counterpoise and binder post?
« Reply #6 on: August 18, 2022, 12:58:33 PM »

Thanks John and Mark. Everything I needed to know.

Kim
KG6WNG
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KM0U

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Re: counterpoise and binder post?
« Reply #7 on: August 18, 2022, 05:32:55 PM »

Check page 10 of the KX2 Owner's Manual.  There is a graphic that shows a BNC binding post adapter with counterpoise and antenna wire on the adapter.  On the same page is reference to using two 25 foot wires (one for counterpoise, the other as radiator) for "good performance" on 40 - 10m.
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KG6WNG

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Re: counterpoise and binder post?
« Reply #8 on: August 19, 2022, 05:50:00 AM »

Thanks KM0U. Don't know how I missed those pages.

Kim
KG6WNG
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KE6VG

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Re: counterpoise and binder post?
« Reply #9 on: August 20, 2022, 08:23:52 AM »

I'm a big fan of resonant antennas, especially at QRP. I know the random wire and tuner is quick to deploy, just not as efficient as a tuned dipole or EFHW.
It will make you plenty of contacts, but consider adding additional antennas to your QRP arsenal.
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KU3X

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Re: counterpoise and binder post?
« Reply #10 on: August 21, 2022, 05:43:54 AM »

I'm a big fan of resonant antennas, especially at QRP. I know the random wire and tuner is quick to deploy, just not as efficient as a tuned dipole or EFHW.
It will make you plenty of contacts, but consider adding additional antennas to your QRP arsenal.

"But I work everything I hear with my crappy antenna !".......True, but it's the stations you don't hear with your crappy antenna you miss out on.
I once worked a station using a leaky dummy load. So.....I worked everything I heard ! Would you use a dummy load for an antenna?

Bob, I could not agree with you more.

From day one I was always a firm believer in using a matched resonant antenna. I want to maximize my ERP and feed my RF in phase with the antenna, not out of phase.
I operate portable QRP all summer long and I would not dream of using anything less.

Barry, KU3X/QRP
« Last Edit: August 21, 2022, 05:47:48 AM by KU3X »
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WB6BYU

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Re: counterpoise and binder post?
« Reply #11 on: August 21, 2022, 03:17:17 PM »

Quote from: KE6VG

I'm a big fan of resonant antennas, especially at QRP. I know the random wire and tuner is quick to deploy, just not as efficient as a tuned dipole or EFHW...




Quote from: KU3X

...From day one I was always a firm believer in using a matched resonant antenna. I want to maximize my ERP and feed my RF in phase with the antenna...




Resonance, or even being matched, does not guarantee efficiency.
Non-resonant doesn't guarantee inefficiency.

Here's an example:  is a 1/4 wave ground mounted vertical with a
feedpoint impedance of 50 ohms "more efficient" than a 5/8 wave
vertical mounted in the same place?

Why?
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