Elecraft

PAR/LNR EFHW antenna

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Lynn W. Taylor, WB6UUT-2

Re: PAR/LNR EFHW antenna

KX2 so not much power. 53 feet of Wireman #534 should tune and radiate
on most bands with a KX2, and fit in a sandwich sized baggie. Another
chunk for a counterpoise.

Simple. Maybe not perfect, but simple.

73 -- Lynn

On 1/9/2018 1:57 PM, Bob McGraw K4TAX wrote:

> I use a switch tapped air inductor with a variable C on one end. It is an L network thus it is reversible and will match either Hi Z or Lo Z loads. This always brings the load to within range the ATU in the radio can resolve a match.
>
> Bob, K4TAX
>
>
> Sent from my iPhone
>
>> On Jan 9, 2018, at 3:48 PM, Lynn W. Taylor, WB6UUT <[hidden email]> wrote:
>>
>> Going way back to the original post, it seems to me that there is a simple answer:
>>
>> The OP wants something that is very portable, that the KX2 will tune.
>>
>> The whole balun discussion comes from trying to match a near-infinite impedance, and chopping the wire down a bit (or making it longer) is going to bring it to an impedance that the tuner can match.
>>
>> Lotta folks doing that.
>>
>> 73 -- Lynn
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K9MA

Re: PAR/LNR EFHW antenna

In reply to this post by Lynn W. Taylor, WB6UUT-2

On 1/9/2018 15:48, Lynn W. Taylor, WB6UUT wrote:
> The whole balun discussion comes from trying to match a near-infinite
> impedance, and chopping the wire down a bit (or making it longer) is
> going to bring it to an impedance that the tuner can match.

That's a trade-off: You can match it without an external tuner designed
for high impedance antennas, but the higher counterpoise current will
waste some of your power. Also, the high current part of the wire,
which does most of the radiating, may be closer to the ground.

73,

Scott K9MA

--
Scott K9MA

[hidden email]

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Lynn W. Taylor, WB6UUT-2

Re: PAR/LNR EFHW antenna

What part of life isn't a trade-off?

Another answer might be "don't feed it at the end."

I'd be thinking about a quarter-wave of ladder line if I was aiming at
one band -- always liked J antennas.

A dipole is a lot closer to 50 ohms.

Lots of answers. All compromises.

73 -- Lynn

On 1/9/2018 2:37 PM, K9MA wrote:

> On 1/9/2018 15:48, Lynn W. Taylor, WB6UUT wrote:
>> The whole balun discussion comes from trying to match a near-infinite
>> impedance, and chopping the wire down a bit (or making it longer) is
>> going to bring it to an impedance that the tuner can match.
>
> That's a trade-off: You can match it without an external tuner designed
> for high impedance antennas, but the higher counterpoise current will
> waste some of your power. Also, the high current part of the wire,
> which does most of the radiating, may be closer to the ground.
>
> 73,
>
> Scott K9MA
>

Don Wilhelm

Re: PAR/LNR EFHW antenna

The end fed dipole is a good solution for a portable antenna - it is
relatively easy to get one wire up in the air - tie a line to a half
filled (or more) water bottle and throw it over whatever support is
available, tie the line to the antenna end and pull it up.

For the home station where there are more options for supporting the
antenna, I prefer center fed dipoles over the end fed.
The center feed maintains balance on the feedline (especially if the
feedline runs perpendicular to the radiator for at least 1/4 wavelength)
and greatly reduces the chances of RF in the shack - yes a balun at the
feedpoint is still necessary to keep RF off the outside of the coax.

So while the end fed antennas will work and radiate effectively, they
can be difficult to tame for RF, but with portable ops, that is usually
not a big problem because low power is typically used.

73,
Don W3FPR

On 1/9/2018 5:51 PM, Lynn W. Taylor, WB6UUT wrote:
> What part of life isn't a trade-off?
>
> Another answer might be "don't feed it at the end."
>
> I'd be thinking about a quarter-wave of ladder line if I was aiming at
> one band -- always liked J antennas.
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Bill K9YEQ

Re: PAR/LNR EFHW antenna

In reply to this post by k6dgw

Fred, I am using the 160 2KWQ version. The coax is not a counterpoise. With a 1/2 wave a counterpoise is not used. You can get 2x the freq from the lowest freq of your wire. Deviating beyond that adds loss and lack of tuning. Use an analyzer to determine the intended freq parameters and you can double . My 160 works great around 1.900 +/- 30 Khz with a tuner, but at the widths I mentioned the efficiency falls off. Use a ground at the xfrmer. This is not a counterpoise, just a method to remove static which a 1/2 wave will collect. As you state, getting a good SWR is not an indication of efficiency. Height, direction, etc., all matter.

73,
Bill
K9YEQ

-----Original Message-----
From: [hidden email] [mailto:[hidden email]] On Behalf Of Fred Jensen
Sent: Tuesday, January 9, 2018 3:26 PM
To: [hidden email]
Subject: Re: [Elecraft] PAR/LNR EFHW antenna

I use an end-fed wire [1/2 wave on 80] from MyAntennas.com run along the top of a wood fence about 1.8 meters high. It has a transformer in a sealed box. The outer surface of the coax seems to serve as the counterpoise. It enters the house through a steel pipe near the ground into a closet and thence to the K3/100.

It works as good as one could expect on 80, 60, 40, 30, and 20. 40 seems to be it's sweet spot. It works on 160 ... not great ... but I make Q's. It's OK on 17 and 15, the SFI has prevented much testing on 12 and
10 although it has SWR minimums [1.3:1 or so] there. It has 1.2:1 SWR on 6 on which I have made exactly zero contacts when the band was open this last summer and could hear lots of stations.

Apparently low SWR does not guarantee low loss, however any antenna is better than no antenna. [:-) I'd have to destroy it to see what's inside the box.

73,

Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County

On 1/9/2018 1:33 AM, Jim Brown wrote:

> On 1/8/2018 8:19 PM, K9MA wrote:
>> I would be cautious about using a transformer above 40 meters, as the
>> stray capacitance may be too large. I haven't tried it, though, so
>> it might work with some transformers.
>
> For years, we've been winding our transformers wrong. The windings
> should be on opposite sides of the core, so that capacitive coupling
> is minimized, NOT laying on top of one another. In a ferrite
> materialthat is SUITABLE for use as a transformer, the mu is high
> enough that a VERY high fraction of the flux in toroid is contained
> within the core, with very little leakage flux. Windings that lay on
> top of each other maximize capacitive coupling, and thus maximize
> common mode current. Windings on opposite sides of the core minimize
> common mode current.
>
> Ferrites are semiconductors, so they act as a dielectric. When we
> place windings on opposite sides of a core, we maximize magnetic
> coupling and minimize capacitive coupling, which is from one winding
> to the core and from the core to the other winding. That capacitance
> is VERY small if the windings are widely spaced.
>
> 73, Jim K9YC

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Bill K9YEQ

Re: PAR/LNR EFHW antenna

In reply to this post by Lynn W. Taylor, WB6UUT-2

FWIW: I believe I answered the question earlier on.

73,
Bill
K9YEQ

-----Original Message-----
From: [hidden email] [mailto:[hidden email]] On Behalf Of Lynn W. Taylor, WB6UUT
Sent: Tuesday, January 9, 2018 3:49 PM
To: [hidden email]
Subject: Re: [Elecraft] PAR/LNR EFHW antenna

Going way back to the original post, it seems to me that there is a simple answer:

The OP wants something that is very portable, that the KX2 will tune.

The whole balun discussion comes from trying to match a near-infinite impedance, and chopping the wire down a bit (or making it longer) is going to bring it to an impedance that the tuner can match.

Lotta folks doing that.

73 -- Lynn
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K9MA

Re: PAR/LNR EFHW antenna

In reply to this post by Bill K9YEQ

On 1/9/2018 19:25, Bill Johnson wrote:
> With a 1/2 wave a counterpoise is not used.

It needs SOME counterpoise, but not much, because the current in it is
very small. If nothing else is available, the coax shield will suffice,
and causes no harm. The small current at the end of the antenna has to
have a return somewhere. I recall old versions of the Handbook showed
an EFHW fed with open wire, with nothing at all connected to the other
conductor, and never could figure out how that worked. I suppose a
little common mode current in the open wire line. Later versions, I
think, showed a short wire opposite the antenna, which at least made
sense to me. The point is that the very small current at the end of the
EFHW will find a return somewhere, and it really doesn't matter.

One way to tell with a QRP radio whether you need a counterpoise is to
watch the SWR as your put your hand on the case of the radio or tuner.
If the SWR doesn't change, you're good to go. I don't recommend this
technique at high power levels.

All of this is true ONLY for an end fed antenna which is a multiple of a
half wave.

73,

Scott K9MA

--
Scott K9MA

[hidden email]

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k6dgw

Re: PAR/LNR EFHW antenna

In reply to this post by VE3GAM Allen McRorie

Thanks Al! Looks like most violate Jim's guidance. Probably explains
why it doesn't work on 6 and may not work or work well on 10 and 12 if I
live to 2021 when we should see spots.

73,

Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County

On 1/9/2018 1:50 PM, VE3GAM wrote:
> here's a video from N4LQ Steve Ellington,
> which shows the inside of the Myantennas box
>
> <https://www.youtube.com/watch?v=xfqlun3bdI0>
>
> Al ve3gam

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k6dgw

Re: PAR/LNR EFHW antenna

In reply to this post by K9MA

Ahhh yes, the End-fed Zepp. Trailing wire out the back of the gasbag,
open wire line to the TX with one end open at the antenna. Every time
someone mentions it, I have Hindenburg dreams.

Yes, it does need a small something for a counterpoise, given the small
current in the high impedance load. One model I tried on 20m needed
about 17 cm of counterpoise, but those little currents seem to use
whatever is available and apparently, there's always something
moderately conductive available.

Sometimes, I think we forget that we are "Amateur" radio operators.
We're not designing antennas for a broadcast station or the VOA.

73,

Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County

On 1/9/2018 5:48 PM, K9MA wrote:

> On 1/9/2018 19:25, Bill Johnson wrote:
>> With a 1/2 wave a counterpoise is not used.
>
> It needs SOME counterpoise, but not much, because the current in it is
> very small. If nothing else is available, the coax shield will
> suffice, and causes no harm. The small current at the end of the
> antenna has to have a return somewhere. I recall old versions of the
> Handbook showed an EFHW fed with open wire, with nothing at all
> connected to the other conductor, and never could figure out how that
> worked. I suppose a little common mode current in the open wire
> line. Later versions, I think, showed a short wire opposite the
> antenna, which at least made sense to me. The point is that the very
> small current at the end of the EFHW will find a return somewhere, and
> it really doesn't matter.