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Horizontal Loop question

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n7tb

Horizontal Loop question

I currently have a horizontal loop at my QTH being matched by an Icom AH-4 Tuner. It is interfaced with my Icom 756. I will be running a new-to-me K2 with the auto tuner installed. Right now, the loop is connected at its end points to 450 ohm ladder that has one leg attached to the tuner's antenna connector and the other leg to the ground lug. Coax comes from the tuner to my rig and works great on my Icom 756. Now for the several questions.

1. the AH-4 interfaces with the 756 via a four conductor molex connector. Is there some way to take those 4 wires and interface them to my K2 and let the AH-4 tune the loop instead of the internal K2 tuner?

2. I presume it possible to take the coax feed from the A-4 off my 756, or have an antenna switch do that, and attach the loop coax feed to my K2, then turn on the 756 to the same frequency that I want to transmit on the K2, and press the tune button on the 756 to tune the loop?

3. I could manually take 450 ohm loop antenna connection off the Ah4, attach it to a balun attached to another length of coax that attaches to the K2, but this is very cumbersome. Perhaps an antenna switch is available that has two balanced feedpoints and a coax feedpoint that would allow me to switch remotely? Does anyone know of such a thing?

4. If I decide to feed the 450 ohm twin lead to coax to my rig, what type of balun do I need? 4:1 or 1:1?

Thanks so much for all you help.

Very 73's
Terry Brown, N7TB

Don Wilhelm-4

Re: Horizontal Loop question

Terry,

I do not really intend to answer your questions about the switching the
feedline, that is up to you In the old days, we did that with a knife
switch, or more 'rich and sophisticated' hams used a DPDT relay.

For the balun, the impedance at the shack end will determine whether a
4:1 or a 1:1 will be a better choice. Measure the impedance on all
bands of interest with an antenna analyzer and use the results to figure
out which will be the better compromise.
The antenna feedpoint impedance will change from band to band, and the
length of the feedline will transform that impedance to something else.
If you have trouble matching it on any one band, try adding or
subtracting 1/8 wavelength of feedline for that particular band and
measure again.

73,
Don W3FPR

On 11/29/2015 10:17 PM, n7tb wrote:

> I currently have a horizontal loop at my QTH being matched by an Icom AH-4
> Tuner. It is interfaced with my Icom 756. I will be running a new-to-me K2
> with the auto tuner installed. Right now, the loop is connected at its end
> points to 450 ohm ladder that has one leg attached to the tuner's antenna
> connector and the other leg to the ground lug. Coax comes from the tuner to
> my rig and works great on my Icom 756. Now for the several questions.
>
> 1. the AH-4 interfaces with the 756 via a four conductor molex connector.
> Is there some way to take those 4 wires and interface them to my K2 and let
> the AH-4 tune the loop instead of the internal K2 tuner?
>
> 2. I presume it possible to take the coax feed from the A-4 off my 756, or
> have an antenna switch do that, and attach the loop coax feed to my K2, then
> turn on the 756 to the same frequency that I want to transmit on the K2, and
> press the tune button on the 756 to tune the loop?
>
> 3. I could manually take 450 ohm loop antenna connection off the Ah4,
> attach it to a balun attached to another length of coax that attaches to the
> K2, but this is very cumbersome. Perhaps an antenna switch is available
> that has two balanced feedpoints and a coax feedpoint that would allow me to
> switch remotely? Does anyone know of such a thing?
>
> 4. If I decide to feed the 450 ohm twin lead to coax to my rig, what type of
> balun do I need? 4:1 or 1:1?
>
>

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DC-3

Re: Horizontal Loop question

I use a 80 meter vertical loop with about 124' of 450 ladder line to a 1
to 1 current balun right outside the window. A 3 foot piece of coax
goes to the tuner (this coax should be as short as possible). You will
find that the Elecraft tuners will cover a broad range. Mine covers all
bands excluding 160. Actually it will tune 160 but with an amplifier, I
expect extremely high voltages at the balun. On 160 you could tune it
against ground if so inclined...

The antenna is a delta loop with the top at 120' in a pine tree. The
bottom wire is at about 50' and it is fed about 1/3rd up a vertical
side. It is an excellent performer and depending on where the lobes are
on the higher bands, it sometimes beat my 3 element tribander. On 40 it
really shines.

There is much written on the net on current baluns vs voltage baluns and
1 to 1 vs. 1 to 4. Also, much is written on common mode current.

Richard
K7SD

> On 11/29/2015 10:17 PM, n7tb wrote:
>> I currently have a horizontal loop at my QTH being matched by an Icom
>> AH-4
>> Tuner. It is interfaced with my Icom 756. I will be running a
>> new-to-me K2
>> with the auto tuner installed. Right now, the loop is connected at
>> its end
>> points to 450 ohm ladder that has one leg attached to the tuner's
>> antenna
>> connector and the other leg to the ground lug. Coax comes from the
>> tuner to
>> my rig and works great on my Icom 756. Now for the several questions.
>>
>> 1. the AH-4 interfaces with the 756 via a four conductor molex
>> connector.
>> Is there some way to take those 4 wires and interface them to my K2
>> and let
>> the AH-4 tune the loop instead of the internal K2 tuner?
>>
>> 2. I presume it possible to take the coax feed from the A-4 off my
>> 756, or
>> have an antenna switch do that, and attach the loop coax feed to my
>> K2, then
>> turn on the 756 to the same frequency that I want to transmit on the
>> K2, and
>> press the tune button on the 756 to tune the loop?
>>
>> 3. I could manually take 450 ohm loop antenna connection off the Ah4,
>> attach it to a balun attached to another length of coax that attaches
>> to the
>> K2, but this is very cumbersome. Perhaps an antenna switch is available
>> that has two balanced feedpoints and a coax feedpoint that would
>> allow me to
>> switch remotely? Does anyone know of such a thing?
>>
>> 4. If I decide to feed the 450 ohm twin lead to coax to my rig, what
>> type of
>> balun do I need? 4:1 or 1:1?
>>
>>
>
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>
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> Please help support this email list: http://www.qsl.net/donate.html
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n7tb

Re: Horizontal Loop question

In reply to this post by n7tb

First, let me say "thank you" to all of you who wrote me very thoughtful and helpful responses to my question. I received many directly to my email address. I came away many great ideas. One is to get ELNEC and use it! I am sorry I did not elaborate about the size of my loop. It is 60 feet on a side, fed on a lower corner (the other three are in trees) with 450 ohm ladder to my AH-4.

I was given the following information for finding an interface for the AH-4 that will interface with any radio. I thought others who may be feeding antennas with this tuner and wanting to interface a non-Icom rig to it might find the link helpful.

http://www.ebay.com/itm/ArtCraft-Electronics-AEAH-4-Icom-AH-4-Antenna-Tuner-Interface-/291613533877?hash=item43e58566b5.

ArtCraft Electronics sells them directly on their website. I think they build to order mostly.

Using the interface is the simplest solution for me, so I ordered one.

Very 73's,

Terry de N7TB

n7tb

Re: Horizontal Loop question

Correction, get the EZNEC software.

sp2bpd

Re: Horizontal Loop question

In reply to this post by n7tb

n7tb wrote

... the loop is connected at its end points to 450 ohm ladder that has one leg attached to the tuner's antenna connector and the other leg to the ground lug. Coax comes from the tuner to my rig ...

Terry, I'm using similar setup.

To avoid radiation from ladder line and keep the antena-line system as close to balanced as possible I've put balun on the tuner end of ladder line. Balun is wound (bifilar) on the toroid.

Regards,

Piotr SP2BPD