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QRPguys no-tune EFHW?


#1

I have been keeping my eyes open for a small cw-only radio to base a running-ascent kit on for when the wx warms up a bit. My KX2 would probably work, but the idea of it jiggling around in a running rucksack didn’t sit well. Anyway, today I scored an ATS-4, which was high on my list. Now to think about an antenna.

Many/most of our summits around here are tree covered. That means that for an ultralight setup I can usually leave my mast at home if I use some sort of end-fed antenna (let’s make the safe assumption that I am not going to want to try elevating the center of a dipole via tree limb). I am now examining the options which do not require a tuner. I’d rather leave that at home as well (especially since I’d don’t have a tiny one).

So one option is the trapped EFHW a la the one discussed this thread: End Fed 40, 20, 10m resonant antenna. That seems to be one good choice.

I also have this kit that I bought for another purpose:

My question for the group: could such an antenna be made “multi band” simply by attaching a radiator the length required for the lowest band to be used (40m for me) and then simply deploying the appropriate amount for the band in use? i.e. I’d put 61.5’ of wire on for 40m, but when I use it for 20m, I’d only deploy 28’ etc. Those lengths could be marked on the wire. I’d be using it for 40, 30, and 20m.

If it would work, one advantage I’d see over the trapped model might be flexibility in antenna size. If I get to the summit and realize I can only deploy 30’ of wire, I just work 20m etc. Not ideal, but I assume that kind of thing presents more of a challenge to the trapped model which assumes the whole wire will be deployed (from what I understand).

Thanks for any input!

73,
Joe // N0MAP


#2

Joe I am going for the same thing, I have spooled up 100ft of wire on to this and plan to mark out each band, in conjunction with the no tune end fed


#3

Hi
You could unspool a half wave for the band of choice but remember that spool of wire gives end loading…mainly capacitive… so the wire will need to be shorter than nominal. As always with an EFHW without tuner or endpoise say goodbye to 3 dB.

73
Ron
VK3AFW


#4

Please explain - I don’t understand???

73, Barry N1EU


#5

Hi Joe,

The ATS-4 is an awesome radio. I got to do an activation with a friends ATS-4 last Fall and I was impressed!

That said, the KX2 is pretty bullet proof. I have a tight-fitting case for mine, and I don’t worry about it banging around in my ruck. I wouldn’t let that worry stop you from getting one. Sounds like you are set for radio tho, so onward!

I have a 20m QCX… I’ve done 2 activations with it so far. On my first activation I worked Japan from a 2 point summit here in W7W land. Woot! What I use is a super ultra-light dipole. I use a twisted pair from an Ethernet cable for the feedline. The whole setup weighs a few OZ, and I usually have 20 or 30 contacts on 20 CW without even trying. It’s just as light / easy to put up as and end fed, and doesn’t require a tuner. Want more bands? Use some lightweight connectors to make it a linked dipole. My entire antenna probably weighs less than that spool you are planning to use!

I know you said you don’t want to suspend a dipole, but I don’t see how its much different than an end fed. You still have to suspend just ONE point. The ends of my dipole I just tie off to bushes or my hiking poles, depending on the summit.

-Josh WU7H


#6

I’m confused by that as well. The QRP guys antenna is a matching circuit so the antenna is “tuned.”

Very interesting @MM0TAI! I’m going to test this over the weekend if the wx holds and I’ll let you know what I find.

Josh (fellow westy brother!) thanks for the suggestion. A single banded super simple dipole is actually my backup plan if the QRP guys antenna doesn’t work the way I want it to. I like the ethernet twisted pair feedline!

73,
Joe


#7

Josh,
I’ve had the recent experience deploying dipoles on two summits in the Midwest where there are so many branches at all heights that they prevent the ends from being pulled out cleanly, i.e., it’s hard to achieve either a traditional dipole or inverted vee layout. However, I’ll admit that I’m not an experienced dipole deployer, since my main sota antennas are end-fed halfwaves.
Peter KD0YOB


#8

Hi,

I do not believe in magic.

Little cores with a winding with one end connected to a wire and the other end to ??? can’t provide a low loss match to the wire. Your coax braid might help out but that would be magic if completed a low loss match.

This is basic stuff fellas. NO FREE LUNCH.

The original end fed antennas were used on Zeppelins and were fed with open wire line. The mismatch loss was acceptable for the application and it was less that the modern offerings…

I’ve used end fed wires on HF for 50 years, when I could not erect something else. A fair average loss figure for the modern end fed is 3 dB. Yes I have a commercial one, just for evaluation. Not used on QRP, I can’t afford the losses.

You can get back half of the losses by feeding it with 300 ohm ribbon 2 m from the end. And no, a 4:1 balun and coax is not the same.

Just because someone sells stuff with a label on it does not remove the need for some magic to make some offerings work other than as a sub-optimal compromise.

I realize that many EFD users have a religious fervor in relation to their efficacy. Just because you can work people on an EFD does not mean you could not have done better with a better antenna.

Sorry if you feel offended but I was asked to explain.

Any further explanations from me will attract a $200 deposit.

73
Ron
VK3AFW


#9

Joe,

I’ve been really impressed with the QRP Guys triband vertical kit as have others. You can bring the pole with you, or get a line over a tree branch at least 17 feet up. The antenna works on 40, 30, and 20, requires no tuner, and works rather well. It’s also pretty easy to build the kit.

The only change I’d make to the directions would be use more than the recommended number of radials (4).

Evan


#10

As others have said - that design is very lossy.

A true end-fed has a high impedance, about 4k. You generally need a transformer with a 9:1 turns ratio (81:1 impedance ratio) to match it to 50 ohms.

The way they make this design “no-tune” is to put the capacitor across the primary. The better way to do this with much lower losses is to put the capacitor across the secondary. However, it then needs to be tuned to match the exact operating conditions (wire length, counterpoise and environment).

For a definitive explanation of End-fed antennas (including the theory) see the article by Steve Yates AA5TB at http://www.aa5tb.com/efha.html


#11

It’s interesting reading Steve Yates AA5TB’s description and comparing it against Tom Rauch W8JI’s description. Tom does say how you can make an EFHW effective and that is what SOTA activators do as a matter of course.

3db loss Ron! Do you have some figures to back that up? I’d expect a few % loss in the matching unit but is the efficiency that low?

I have no dog in the end fed race. I did use one on 10/12m but it was when we were on the up side of the last solar cycle when 10&12 opened well. I found no problem working SOTA chasers with one but probably conditions were such that a few damp noodles stretched out from the 817 would have enabled WW DX just as easily.


#12

I haven’t been in ham radio long enough for this to be the case. I cannot wait for the next solar max.


#13

Hi Andy
This topic is a dead horse.
I dont flog horses dead or alive. Plenty of data in past whippings.
You need to differentiate between an end fed and a near end feed or even a Zepp feed as in the refetenced articles.
I have worked stations on a piece of string soaked in vinegar. It is not a great antenna. Possibly worked about the same as a magic EF. Dries out quickly. SWR is unstable.

73
Ron
VK3AFW
QRT


#14

…which you have not done! You have made a series of assertions but failed to back them up with anything resembling science. Anyway, even if you are right, 3dB is half an S-point, which will not usually be noticed.


#15

You want me to start with Maxwell’s equations?
NBL
R


#16

Stick with the $200 deposit requirement Ron… your time is your own!

73 Phil


#17

$200 sounds steep, but if we happily end up in the same pub I’ll buy you a beer or two for your thoughts on this matter.

Specifically, what antenna would you opt for if you were me given the constraints of my plan? The pack I use for running is about 5L (one of these https://www.rei.com/product/866607/osprey-rev-6-hydration-pack-51-fl-oz). As Peter notes, summit around here usually look like this but often without any clearing at all. (there’s the pack)

The order of my criteria for antenna selection in this application is: weight, quickness of deployment, ease of deployment in heavy woods, performance. In that order.

73,
Joe


#18

It is very unfortunate that the majority of the statements made regarding to the QRPGuys No Tune End Fed Half Wave Antenna are either completely false, contradictory or often based on the assumptions of others.

As mentioned by Andy@MM0FMF and Brian@G4ADD we - many hundreds/thousands of poor but highly satisfied and successful users of broadband impedance torodial transformers together with true EFHWs do not understand the 3 dB thesis made by Ron@VK3AFW as a killer reason to stop further use.

To be fair, from a technical point of view the QRPGuys No Tune End Fed Half Wave Antenna is nothing more and nothing less than a copy of the many other commercially offered and countless homemade versions - for years!

It’s understandable that newcomers to antennas do not know the full story, but a bit of restraint in grabbing the keys would be appropriate. Thanks.


#19

I have been using EFHW aerials for the last few years with great results on 60m, 30m, 40m, 20m, 17m & 15 m.

I used this design all of the time https://pa3hho.wordpress.com/end-fed-antennes/multiany-band-end-fed-english/ which are easy to build and deploy.

Admittedly I dont activate summits but I do loads of baclpacking style /P operating. I find they perform almost as well as a dedicated dipole or my doublet at home and are far better than any of the commercial ‘Compact’ aerials like the Buddipole and MP1 etc., both of which I have owned and discarded.

I have occasionally used a 58 ft wire with a 13ft counterpoise directly on the KX2 but still prefer the EFHW.

The only other alternative is a ‘Random’ wire using a 9:1 balun but I found it NOT to be as efficient.

For what an EFHW will cost you to make you should give it a try, we cant all be wrong :slight_smile:

73 de G4POP


#20

I would say rather that we do not accept the 3dB thesis made by Ron. Why 3dB? Why not 1dB or 6dB?

I tend to think it is significantly less than 3dB.

Barry N1EU