Build an End-Fed Halfwave antenna and bal-un

palmerjrusa

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For the PAR and home made versions I like to get the entire length of wire horizonal and as high as possible but thats limited to about 15-25ft due to available trees, etc. On the home made versions with chalk line reel the empty chalk line reel is your throw weight to get the far end up in a tree. I usually carry a second chalk line reel with about 80ft of miniature parachute cord to toss over another tree and pull up the transformer end. If a second tree is not available I will sometimes use the antenna with the transformer lower and the wire sloping up to the only tree or high point.

In all cases I get signal reports similar to other 100 watt stations on the band and I'm usually running about 10 watts into the end fed.
Thanks, I want to use having an IC-705 as an opportunity to learn more about getting the max out of a QRP rig using effective antennas and learn more about the technical/theory side of that rather than just cranking up the transmission wattage.
 

prcguy

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This is more for the IC-705 thread but you can also maximize your QRP power by careful adjustment of mic gain, EQ and compression. I have very similar settings in my IC-7300 and IC-7610 that punch through much better than the stock settings. I can post these settings in the 705 thread after I get a 705 and play with it.

Thanks, I want to use having an IC-705 as an opportunity to learn more about getting the max out of a QRP rig using effective antennas and learn more about the technical/theory side of that rather than just cranking up the transmission wattage.
 

wa8pyr

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Do you use some catapult arrangement to get the antenna high up in a tree branch or limb?
I usually find a tree where the limbs aren't too close together and then do an overhand lob, similar to throwing a hand grenade, aiming as high in the tree as I can get. Usually takes a couple of tries; a major league pitcher I ain't. I've also used a wrist rocket slingshot, which is a tried-and-true ham radio standby.

It's limited pretty much only by your imagination; if it gets the end of the wire up in the tree, it's good. I know a couple of guys who've used potato guns as a gag, although lugging one out to the woods isn't exactly practical. Sure was funny, though.
 

palmerjrusa

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This is more for the IC-705 thread but you can also maximize your QRP power by careful adjustment of mic gain, EQ and compression. I have very similar settings in my IC-7300 and IC-7610 that punch through much better than the stock settings. I can post these settings in the 705 thread after I get a 705 and play with it.
Please do that, that would be great.
Thanks!
 

belvdr

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I have a spool of 22ga Teflon wire for the antenna. Is that large enough to support 10 watts on SSB and CW?

I ran 14 gauge on 100w and never had an issue but this wire seems tiny in comparison.
 

tweiss3

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So I have a comment and a question, directly related to a 49:1 transformer.

I have a MyAntennas EFHW in 8010P (200W-ICAS max.), which from my understanding is a 49:1 similar, if not identical to the one described in this thread. I have found, when running FT8 on 80m at 100w, it does get hot after a while, and will start to drift/raise in SWR, so just keep that in mind.

The question I have is about the discussion of counterpoise. A counterpoise is required, or does the coax act as the counterpoise? The documentation for the MyAntennas version says there is a grounding lug, but if its over 10' above the ground to not worry about it. Would I get increase performance hanging 10' of wire from the ground lug as counterpoise? And is a counterpoise required if I were to build one based on the directions here.
 

prcguy

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According to some studies, a counterpoise of a minimal size is required, something like 1/20 of a wavelength, but the coax exiting the transformer easily meets this requirement. I good common mode choke is also recommended and I usually place those 20ft down the coax from the transformer to leave some coax as a counterpoise. I've tested many of these end feds, some with no common mode chokes, some with chokes right at the transformer and some with a length of coax between the transformer and choke. I've never found any difference in performance but I do see the some RF on the coax if you try to use the antenna way out of band and without a common mode choke.

I've also seen some people in ham groups state you have to do this or that otherwise the EFHW will never work. Danny at MyAntennas has chimed in with the facts, thousands and thousands of these are in service with and without common mode chokes or grounds and they all simply work.


So I have a comment and a question, directly related to a 49:1 transformer.

I have a MyAntennas EFHW in 8010P (200W-ICAS max.), which from my understanding is a 49:1 similar, if not identical to the one described in this thread. I have found, when running FT8 on 80m at 100w, it does get hot after a while, and will start to drift/raise in SWR, so just keep that in mind.

The question I have is about the discussion of counterpoise. A counterpoise is required, or does the coax act as the counterpoise? The documentation for the MyAntennas version says there is a grounding lug, but if its over 10' above the ground to not worry about it. Would I get increase performance hanging 10' of wire from the ground lug as counterpoise? And is a counterpoise required if I were to build one based on the directions here.
 

belvdr

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I used a MyAntennas 8010 here for awhile but I have a very high noise floor here, on the order of S7-8 on 80m. Now I am just going to work portable; I’ve given up a home shack except 2m.
 

belvdr

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@prcguy How did you attach the antenna wire and mini paracord, and keep it small enough that it didn't bunch up the reel? I was thinking of twisting them together tightly, possibly with some glue and then heat shrink over top of that.
 

prcguy

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I used a bowline knot on the wire and string and had to enlarge the hole in the reel a little to pass the knot through. Some chalk line reels have felt pads inside and others have a rivet that the string passes through. I usually remove all that so the string and wire pass freely without catching on anything.

@prcguy How did you attach the antenna wire and mini paracord, and keep it small enough that it didn't bunch up the reel? I was thinking of twisting them together tightly, possibly with some glue and then heat shrink over top of that.
 

belvdr

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I used a bowline knot on the wire and string and had to enlarge the hole in the reel a little to pass the knot through. Some chalk line reels have felt pads inside and others have a rivet that the string passes through. I usually remove all that so the string and wire pass freely without catching on anything.
Thanks for the info. These have the felt pad.
 

tweiss3

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According to some studies, a counterpoise of a minimal size is required, something like 1/20 of a wavelength, but the coax exiting the transformer easily meets this requirement. I good common mode choke is also recommended and I usually place those 20ft down the coax from the transformer to leave some coax as a counterpoise. I've tested many of these end feds, some with no common mode chokes, some with chokes right at the transformer and some with a length of coax between the transformer and choke. I've never found any difference in performance but I do see the some RF on the coax if you try to use the antenna way out of band and without a common mode choke.

I've also seen some people in ham groups state you have to do this or that otherwise the EFHW will never work. Danny at MyAntennas has chimed in with the facts, thousands and thousands of these are in service with and without common mode chokes or grounds and they all simply work.
My wife informed me that I "ruined" her movie night last night as the surround sound picked up noise when I transmitted from my radio. I suspect RFI on the feed line. Can you recommend a good choke to use on 400Max feed line?
 

wa8pyr

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My wife informed me that I "ruined" her movie night last night as the surround sound picked up noise when I transmitted from my radio. I suspect RFI on the feed line. Can you recommend a good choke to use on 400Max feed line?
Any of these should do the trick; install at a point before the coax enters the house, but at least 20 feet from the antenna if possible.


The jumper choke would probably be your best bet. I've found that you generally need quite a few of the snap-on variety (anywhere from 7 to 10) for them to be really effective.

Update: Here's a good tutorial on rolling your own... https://w6nbc.com/articles/2020-TBDcoaxchokebalun.pdf
 
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