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Author Topic: Emergency Amateur Radio Club Hawaii = END FED 6–40 Meter Multibander  (Read 4457 times)

Offline G0BVZ

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By happy accident, I found this design and I'm glad I did:

http://www.earchi.org/92011endfedfiles/Endfed6_40.pdf


I made one using stuff I had in the junk box and it works fb. There are no new ideas here but the design is a great combination of known principles
Disadvantages
(1) It needs around 5m of coax feed.
(2) It needs a small atu.
Advantages
(1) Fairly compact & stealthy.
(2) Multiband.
(3) Easily configurable in the field.
(4) Light hookup wire works fb at qrp, easy to have different colour coded lengths for various situations.

There is customer feedback, from those who purchased the antenna from the club, at the bottom of the link above which is well worth reading. It is great that the club encourages folk to build the antenna.

'Experts' may grouch that it is not the most efficient antenna and design XYZ... is better: I say that for simplicity and effectiveness it is hard to beat; the best antenna is the one you have when you want to get on the air!!!

Vic

Offline PG4I

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Re: Emergency Amateur Radio Club Hawaii = END FED 6–40 Meter Multibander
« Reply #1 on: January 13, 2014, 11:09:50 UTC »
I know of a dutch company that sell these as a commercial product, see http://www.hyendcompany.com/antenna
Price is around 100 euro. They are very popular over here.
Joop - PG4I/QRP

Offline G0BVZ

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Re: Emergency Amateur Radio Club Hawaii = END FED 6–40 Meter Multibander
« Reply #2 on: January 13, 2014, 11:56:05 UTC »
I know of a dutch company that sell these as a commercial product, see http://www.hyendcompany.com/antenna
Price is around 100 euro. They are very popular over here.


Good morning Joop!!

I checked the link you gave and I see their version is made using absolutely first rate materials but there are some differences. They do not claim such a wide frequency range, probably because they also claim that no tuner is needed.  This Dutch company has an equivalent here in UK: http://www.gwhip.co.uk/widebander.htm but this widebander needs an atu.  You pay your money and you take your choice....    :)

My version probably took 90 minutes to make from junk and a small plastic box.  I find light hookup wire pretty durable.  (In summer 2013 I put up a low 40m horizontal loop of hookup wire for NVIS work and it has survived a VERY windy winter so far.)  I'm MUCH more inclined to experiment with wire antennas when the wire does not cost Euros 1.20/metre!!!  Also, for rigging antennae I use green paracord produced by WebTex and sold on Ebay. It costs around Euro12 for a 100m reel. Lots of experiment potential!! It is fairly hard to see and it lasts well.  I guess I must be cheap: but I'm happy to keep things basic. As many folk say, there is merit in simplicity.  ;D

Vic  / off to make coffee


Offline PD7MAA

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Re: Emergency Amateur Radio Club Hawaii = END FED 6–40 Meter Multibander
« Reply #3 on: January 13, 2014, 14:40:06 UTC »
Hello OM´s

The Hawaiian enfed has nothing more than a 1/9 UNUN transformer . I build several of these antenna´s but the efficiency is pitiable and can not  be compared with the Dutch antenna´s for a unun type antenna is never resonant  on ham bands and gives a lot of stress at your qrp receiver frontend.

BTW a unun should be build on a FT140- 43 type toroid......
Have fun

73 John
73, John
d(-_-)b

Offline G0BVZ

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Re: Emergency Amateur Radio Club Hawaii = END FED 6–40 Meter Multibander
« Reply #4 on: January 13, 2014, 17:30:02 UTC »
The Hawaiian enfed has nothing more than a 1/9 UNUN transformer . I build several of these antenna´s but the efficiency is pitiable and can not  be compared with the Dutch antenna´s for a unun type antenna is never resonant  on ham bands and gives a lot of stress at your qrp receiver frontend.

BTW a unun should be build on a FT140- 43 type toroid......
Have fun

73 John

Hi John,
I guess the best toroid is the one which does the job.
Amidon spec for FT140- 43 "43 Material is used for EMI/RFI suppression in the 20 MHz to 250 MHz range"
Amidon spec for T130-2 is "Frequency Range 2 Mhz - 30 Mhz"

For general QRP HF purposes I'd probably specify T130-2 (That's what I used -Overkill!!); the EARC Hawaii group specifies the smaller T106-2 .  The type 43 material you advise  might be the better choice for upper bands + 6m. I guess it all depends on what you want to achieve, where you want best response to be.

As to resonance, I think maybe it is over rated.  A resonant antenna is only resonant on one frequency. Stray far from that QRG and the antenna is no longer resonant. -But that doesn't make it a bad antenna.  ;D

My wonderful doublet with open feeders isn't resonant on any frequency I can legally transmit on but it really does the business when coupled to a good antenna matcher.  There is great merit in simplicity....

In the days before the military used frequency agile radio systems, they regularly used resonant antennas, but in those days they were also using fixed frequency links!

It was very nice to exchange ideas with you.

Vic

Offline PG4I

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Re: Emergency Amateur Radio Club Hawaii = END FED 6–40 Meter Multibander
« Reply #5 on: January 13, 2014, 18:09:29 UTC »
I have seen a measurement on the Dutch end fed with an antenna analyzer. I was really surprised, it shows resonance on 10, 20 and 40 with a low VSWR. So it is resonant on 3 bands, this is for the short version. I guess the wire is resonant for every half wave that fits. Of course impedance at the end of the wire will be high because current is zero. So with need a transformer with as high ratio as possible.
Joop - PG4I/QRP

Offline G0BVZ

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Re: Emergency Amateur Radio Club Hawaii = END FED 6–40 Meter Multibander
« Reply #6 on: January 13, 2014, 18:59:19 UTC »
I have seen a measurement on the Dutch end fed with an antenna analyzer. I was really surprised, it shows resonance on 10, 20 and 40 with a low VSWR. So it is resonant on 3 bands, this is for the short version. I guess the wire is resonant for every half wave that fits. Of course impedance at the end of the wire will be high because current is zero. So with need a transformer with as high ratio as possible.

Hi Joop!
I've had plenty of surprises with antenna analysers too!  I've 'tuned' an analyser across its entire range and been astonished at how many points of resonance have popped up on one antenna (most of them useless to a ham).  The Dutch outfit you mentioned appear to have done a very good job of optimising their product to make it resonant in three interesting bands: they specify top notch materials too.  Even when the swr creeps high at the band edges there is a good chance a rig's limited internal atu will be able to pull it into line so it's a product with a future. The English GWhip company makes a similar product.

One of my biggest learning experiences was with a 10MHz quarter wave wire vertical with elevated radials. I cut the radiator to size and taped it to a fishing pole. The feed point was about 1.5m above ground. Initially I ran the 4 radials  from the feedpoint down to the ground, just to get an idea of where I was. It was a disaster.  Then I tied cord to the radial ends and pegged them out so the ends were about 30cm above ground.  Things were much better with the first one and by the fourth it was just about perfect. The radiator just needed a little shortening.

I was absolutely shocked.  I would never have believed getting the radials off the ground would make such a difference. It was at that moment I realised that my antenna experiments of the past were more or less blundering about in the dark. I'm still embarrassed when I run over that memory....

Hats off to the old antenna experimenters!!  I remember reading of one such who consumed an unbelievable amount of wire before he hit on the right dimensions for the antenna he was developing.  The antenna analyser is a real boon to us now. Of course, back then vswr hadn't even been invented!!!  ;D

Vic

Online GM0LVI

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Re: Emergency Amateur Radio Club Hawaii = END FED 6–40 Meter Multibander
« Reply #7 on: January 13, 2014, 20:52:43 UTC »
I'm surprised the Hawaiian balun doesn't incorporate a binding post for a counterpoise.
There's an interesting article by VE3EED - sk here >

http://www.hamuniverse.com/randomwireantennalengths.html

Here my cheap and cheerful 9:1 balun -

Dave

Offline PD7MAA

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Re: Emergency Amateur Radio Club Hawaii = END FED 6–40 Meter Multibander
« Reply #8 on: January 13, 2014, 20:55:03 UTC »
Hi Vic

The T200-6 wil give a verry lossy 1:9 transformation for the Al value is to low.
To get you up to date visit http://www.karinya.net/g3txq/unun/
A field strength meter wil show more.

Have a look and learn.....

73 John
73, John
d(-_-)b

Offline G0BVZ

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Re: Emergency Amateur Radio Club Hawaii = END FED 6–40 Meter Multibander
« Reply #9 on: January 14, 2014, 12:23:57 UTC »
Hi Vic

The T200-6 wil give a verry lossy 1:9 transformation for the Al value is to low.
To get you up to date visit http://www.karinya.net/g3txq/unun/
A field strength meter wil show more.

Have a look and learn.....

73 John


Hi John,
I'm a fast learner: many thanks for giving me that link.  It was kind of you to direct me to a site which not only confirms my beliefs, but which also expresses them better than I could.  One interesting quote from it is

"Clearly, introducing any of the UnUns makes a dramatic improvement to the SWR on most of the bands; the exceptions are those bands where the SWR is already low. Choosing between the various UnUn designs is not easy - one does better than the others on a few bands, but is worse on others. Taken overall, with this particular antenna the 9:1 UnUn wound on Type 2 material probably has the edge."

Very wisely, this author cautions "With all the UnUn designs, loss becomes much higher at low frequencies if the antenna is shortened; so be very wary of the power-handling claims for UnUns wound on T200-2 toroids and used with short antennas."  He is right. QRO ops can develop big voltages across UnUns, which can also become kinda warm if the toroid is too small.  Cautious QRO types wrap the toroid in teflon wrap and put the wire into teflon tubing. Precautions like that at QRP are really not necessary. One day I will try smaller and smaller toroids to discover how small (and therefore light) I can go before size becomes an issue.

In terms of overall performance, author G3TXQ concludes "Just because one design of UnUn has slightly more loss than another doesn't necessarily mean that its transmitted signal will be weaker; if that design results in a lower SWR on the feedline - and therefore lower feedline loss - it could still produce the net greater signal. To take account of these factors I measured the signal picked up from the antenna by a local receiver, and swapped between the UnUn designs. The bar chart shows the results referenced to the signal from the vertical without an UnUn. Again, with this particular antenna, the 9:1 UnUn wound on Type 2 iron dust material gives the best overall results."

So... Honolulu Emergency Radio Club,  respected experimenter G3TXO whose work you pointed out, myself and many others agree this design, using the type 2 mix gives best results.

This antenna is not the best in the world: it is not the most efficient either. -But it is cheap, easy to make, fairly compact; it constitutes a fantastic emergency/backup antenna and it allows thousands of hams to get on the air routinely to make satisfying contacts. What's not to like?

In the past I've been shocked by rude, abrupt and dismissive 'experts' who have one way or another told me it can not work/ will not work/ does not work...... I'm no longer shocked.  I simply allow these experts to stand on the sidelines while I -and many, many others- get on with using it happily.

Some say the bumblebee cannot fly, but the bee does not know it can't fly so it continues to do so. Some Victorian experts, when steam trains were being developed, declared that humans could not survive at 30 miles per hour: we're still here...

If you need a holiday antenna, if you have local laws which limit your ability to erect antennas, if you need an emergency/backup antenna, if you just like messing around with antennas then give this design or one of its variants a whirl: you may be surprised, you may have some fun; just don't expect miracles... -and use around 5m coax feeder.


Vic




Offline G0BVZ

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Re: Emergency Amateur Radio Club Hawaii = END FED 6–40 Meter Multibander
« Reply #10 on: January 14, 2014, 12:47:14 UTC »
I'm surprised the Hawaiian balun doesn't incorporate a binding post for a counterpoise.
There's an interesting article by VE3EED - sk here >

http://www.hamuniverse.com/randomwireantennalengths.html

Here my cheap and cheerful 9:1 balun -

Hi Dave,
Nice balun. I'm with you on the counterpoise idea. 

My version does have a binding post for a counterpoise but with the lengths of radiator I've chosen so far and 5m of coax feeder it seems not to need one. When the weather is warm enough to let me take my old bones back out into the garden I intend to discover if using a counterpoise will let me get away with using a shorter length of coax feeder. Light hook up wire is lighter and more compact than coax! :-)

What do you think to using a small croc clip to temporarily attach a counterpoise to the unun's coax connector from the rig, as needed?  Just an idea...

Vic


Online GM0LVI

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Re: Emergency Amateur Radio Club Hawaii = END FED 6–40 Meter Multibander
« Reply #11 on: January 14, 2014, 23:46:57 UTC »
I'm surprised the Hawaiian balun doesn't incorporate a binding post for a counterpoise.
There's an interesting article by VE3EED - sk here >

http://www.hamuniverse.com/randomwireantennalengths.html

Here my cheap and cheerful 9:1 balun -

Hi Dave,
Nice balun. I'm with you on the counterpoise idea. 

My version does have a binding post for a counterpoise but with the lengths of radiator I've chosen so far and 5m of coax feeder it seems not to need one. When the weather is warm enough to let me take my old bones back out into the garden I intend to discover if using a counterpoise will let me get away with using a shorter length of coax feeder. Light hook up wire is lighter and more compact than coax! :-)

What do you think to using a small croc clip to temporarily attach a counterpoise to the unun's coax connector from the rig, as needed?  Just an idea...

Vic


Yes the croc clip should work Vic but a binding post would be easier to manage and possibly more electrically efficient.
Now, and I stand to be corrected on this; if you are using a balun your coax should not  be be part of the antenna system and an end fed antenna works against ground. Most ground is very lossy and therefore a counterpoise or counterpoises ought to make a significant difference regardless of the length of feeder you use.

Dave
Dave

Offline G0BVZ

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Re: Emergency Amateur Radio Club Hawaii = END FED 6–40 Meter Multibander
« Reply #12 on: January 15, 2014, 02:30:54 UTC »
Quote
Yes the croc clip should work Vic but a binding post would be easier to manage and possibly more electrically efficient.
Now, and I stand to be corrected on this; if you are using a balun your coax should not  be be part of the antenna system and an end fed antenna works against ground. Most ground is very lossy and therefore a counterpoise or counterpoises ought to make a significant difference regardless of the length of feeder you use.
Dave
I think you're on pretty safe ground there Dave. Certainly a counterpoise can't do any harm. I reckon the Hawaiian group is relying on the coax screen to be the counterpoise, which is why they suggest it works best with a certain length.  (And I bet it radiates a bit too...) Could be the counterpoise would make a dramatic difference if it was rigged entirely clear of the ground: that may well serve to decouple radiator better from the coax than if laid on the ground. Looks like there's going to be some experimentation when the weather softens...

Vic

Offline K7HB

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Re: Emergency Amateur Radio Club Hawaii = END FED 6–40 Meter Multibander
« Reply #13 on: January 27, 2014, 01:46:44 UTC »
Hi All,
I built several of the Hawaii end feds. The 40 through 6 did require a tuner. Although I tried to cut it to resonance for 40  I must have kept missing the resonant length and decided to keep using a tuner.
However, The single band versions resonate well enough with some trimming. Also, by using known capacitance per foot rg174 and adjusting the toroid turns proportionally I built a great 80 M version. Half waves work on even multiples so, just scale up the 40 M version.
73
de K7HB

Offline KC8AON

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Re: Emergency Amateur Radio Club Hawaii = END FED 6–40 Meter Multibander
« Reply #14 on: November 06, 2014, 21:51:17 UTC »
The Hawaiian enfed has nothing more than a 1/9 UNUN transformer . I build several of these antenna´s but the efficiency is pitiable and can not  be compared with the Dutch antenna´s for a unun type antenna is never resonant  on ham bands and gives a lot of stress at your qrp receiver frontend.

BTW a unun should be build on a FT140- 43 type toroid......
Have fun

73 John

Hi John,
I guess the best toroid is the one which does the job.
Amidon spec for FT140- 43 "43 Material is used for EMI/RFI suppression in the 20 MHz to 250 MHz range"
Amidon spec for T130-2 is "Frequency Range 2 Mhz - 30 Mhz"

For general QRP HF purposes I'd probably specify T130-2 (That's what I used -Overkill!!); the EARC Hawaii group specifies the smaller T106-2 .  The type 43 material you advise  might be the better choice for upper bands + 6m. I guess it all depends on what you want to achieve, where you want best response to be.

As to resonance, I think maybe it is over rated.  A resonant antenna is only resonant on one frequency. Stray far from that QRG and the antenna is no longer resonant. -But that doesn't make it a bad antenna.  ;D

My wonderful doublet with open feeders isn't resonant on any frequency I can legally transmit on but it really does the business when coupled to a good antenna matcher.  There is great merit in simplicity....

In the days before the military used frequency agile radio systems, they regularly used resonant antennas, but in those days they were also using fixed frequency links!

It was very nice to exchange ideas with you.

Vic

John is correct if you want a unun with a flat swr response over a broader frequency range.  Try winding 4:1 baluns on each type, connect a 200 ohm non inductive resistor to them and sweep them with your antenna analyzer.  The mix 2 core will have many peaks and valleys and the mix 43 core will have a low swr  from 160 to 10 meters.