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40-80 EFHW - Help!


#1

I’d like to make a lightweight EFHW for SOTA that will operate on 40, 60 and 80m with just one simple matching device. Has anyone any experience of this? Plans for 15-40m set ups are plentiful, and also a few for 80m set ups, but I found nothing for a 40 through to 80 multiband. Thanks.

73 John MW0XOT


#2

Try this: http://lmgtfy.com/?q=half+wave+end+fed+antenna

http://www.spirat.com.au/vk5zvs/pic54.htm


#3

EFHW for 80m is how long?


#4

The best resource for EFHWs is probably this
http://www.aa5tb.com/efha.html

I don’t currently do 80m but operate a EFHW on 60.
I use just a simple L match.

Highly recommend the EFHW, in fact a fail to understand the folks who go for he complexity of a centre fed :slight_smile:

Pete


#5

~40 metres :smile:


#6

I suppose Pete it boils down to what you have to hand. I had coax and some PVC wire and that seemed easier to put together than a matching unit. I did have an EFHW for 10m till I left the matching unit on Torlum Hill :frowning:

It would be interesting to compare and contrast a selection of antennas sometime. Maybe a joint SOTA antenna shoot out activation where you could get a group of activators to set up dipoles, EFHW, verticals, etc. and compare them live. Or perhaps you’d end up more confused.

EFHW on 80 seems huge. I keep thinking I should try 80m more when the Winter comes. I never used 80m much when I was regularly using 60m partly because the antenna was so big. It felt massively bigger than the 60m dipole. I should try adding some loading coils to the ends of that. The ability to attache a couple of coils and be on 80m in seconds is appealing.

I must have words with Mrs. FMF. Someone let some frozen peas escape from the bag in the freezer and a loose pea ended up in the ice tray. I’ve just discovered it floating in my Martini now! I thought it was a bit of an Olive at first. I’ll have to screen the rest of the cubes before use in case there’s sweetcorn or green beens or who knows what embedded in them :smile:


#7

That really is taking the pea :wink:


#8

I recommend the W3EDP antenna. This venerable design has stood the test of time. The one I made covers 80, 60, 40 and 20 with a simple tuner, it resembles an EFHW in the way it is set up and the design of the tuner but has a fixed length of 84 feet and a variable counterpoise. Much more convenient on 80 than a 132 foot wire!

Brian


#9

Hi John,
Why an end fed antenna? Yes they work but the matching is always lossy and you always get some common mode rf meaning the feed line and rig and mike cord/key cord are part of the radiator.

I understand that in some circumstances a mobile whip/buddypole/buddystick/loop/wetstring or an end fed antenna is the only configuration that is practical. The Zeppelins had no choice for example.

Assuming you have your heart set on an EFD may I suggest you make up an antenna with a 21 m wire. Feed it 2 m from the end with 6 to 8 m of 300 ohm ribbon. Use a 4:1 CURRENT balun at the end of the ribbon - keep the weight off the wire/mast. And of course you need an ATU. It will tune from 3.5 to 30 MHz. On 5 MHz and 3.5 MHz the feed line provides the extra length a la G5RV. We don’t have 5 MHz allocated here so not used there but I have used this antenna a couple of times and it is comparable to an OCFD on 80 and 40 in spite of being half the length and I’ve made good contacts on 30, 20 and 15 m with it. If you must use a voltage balun follow it up with a current choke or be prepared to use a counterpoise to get rid of RF on the mike cord. A balanced Hi Z ATU could be used and the balun dispensed with.

Advertising has a lot to answer for, selling product that isn’t the most efficient. I can go back to the Joystick all band all mode dx antenna that you sat in the corner of the flat and worked the world with. No shortage of testimonials. A complete scam. 52 years later I’m still cross at being taken in.

73
Ron
VK3AFW
Dedicated link dipole user.


#10

Er… Am I missing something here… Surely that would be three EFHW’s? Or perhaps a link EFHW :wink:

If it’s an end-fed antenna you’re after, I can heartily recommend the W3EDP I have used one from home locations for many years and found it very simple to set up and effective. One tuner covers 80/60/40m for me with an 84’ top and a 16’ counterpoise.

Still prefer centre fed for portable though

73 de Paul G4MD


#11

You can make the EFHW for the highest frequency (shortest antenna) and design your match unit so that it has sufficient range to accommodate the same length of wire on lower frequencies. I did this when I used one, designed for 10m so 5m of wire.There should minimal current at the feed point and you could get away with 2m of RG58 between the match unit and the 817 as a counterpoise. I always attached a 2m piece of PVC hookup wire anyway to the earthy side “just in case”.

My match unit had sufficient range that it would match the same antenna on 12 and 15m. What happens to currents on the counterpoise, coax braid, radiation pattern, efficiency is left for interested parties to analyse. Suffice to say it worked, with the EFHW 5m vertical and fed at the bottom but using 15m not 10m, I did have a successful CW QSOs on it and managed to cross the pond once.


#12

Thanks for that. Yes it would, in effect, be 3 EFHWs, although I was considering a linked wire and a tune-able match that would do all three bands. I understand that this can be tricky on the lower frequencies, hence my question. I was hoping I could avoid too much trial and error!

73 John MW0XOT


#13

Hi Brian, Thanks for your input. I was attracted to the EFHW by its simplicity and the avoidance of a length of coax! Up to now I’ve used Inverted V dipoles. The W3EDF might be worth investigating, and I’d forgotten about them . I have one here but very heavy-weight so not really any good for SOTA. Could you give me, or direct me to, more details of your design please, especially the “simple tuner”. There are so many pages on the internet about the W3EDP, all presenting different designs (and opinions!). Thanks.

73 John MW0XOT


#14

The tuner is simplicity itself. Twenty turns of wire on a 35mm film container, tuned with a polyvaricon (for the 817) or an air-spaced capacitor for higher powers (I have a 100 watt version for the 857) and the antenna comes off the top and the counterpoise off the bottom. It can be fed with either a tap about three turns up, or a link of about three turns at the “earth end”. However I have a homebrew Z-match that works equally well. I have about a metre of coax to the rig.

The thing to remember is that the counterpoise is part of the radiating system so it needs to be off the ground for best results, two or three feet is adequate. The counterpoise is 16.5 feet on most bands but needs to be shorter on 20 metres, about 7 feet. If you use a grp tent pole to hold the counterpoise end then you can just twirl it to wind on the surplus wire for 20 metres.

The joy of this antenna is that on a rocky or boggy summit or in bad weather you are spared the necessity to leave the operating position when changing bands except for the counterpoise twirling on twenty.

Brian


#15

You stole that solution from me! :wink:


#16

Guilty as charged! Actually my counterpoise is wound on a bobbin and I unwind it to a piece of electrical tape marking the length, but I find your way more elegant!

Brian


#17

Hi Brian

Thanks for details. I have all the materials and parts so I’ll just have to make one and try it for myself. 73 John MW0XOT


#18

Hi John,
Just come across these and wondered if they may be of interest?


Regards,
Colin G8JSM


#19

Have a looksee here for what goes inside those end-fedz.

73 de David vk2dmh

Some even use a fixed capacitor soldered across the toroid for QRP work. Then they tune each endfed wire to minimise VSWR. Done once, then no more mucking around. Here I am quoting from the SOTA group in Yahoo Groups:

"I use a T50-43 core, and I fit it into my MTR 3 band, or into a dental floss case (total weight 10 grams) with an RCA male on one end, a 2mm female on the other for my ATS4. In both cases, then, I plug the end of the #28 gauge teflon wire directly into the radio. The built-in internal version, homebrew effort, I can not assert that it is delivering a perfect match, because I don’t actually know if it is or not. The external version in the floss case I know does.

The EFHW wire has mini-traps each weighs in the order of a few grams made using T50-6 cores. This is most important when using #28 wire to minimize stress on the wire. Mine has never broken (yet) even in 50 mph winds.

73 Fred KT5X (WS0TA)"
(Quoted and passed on by David vk2dmh)


#20

Hi Coiln, I just built that match unit. It works great on resistive loads, but I can’t get less than a SWR of 6.8 on my 40m wire on 7.100 MHz.Something strange going on I guess. Thanks for pointing out the links.

73 John MW0XOT