Build an End-Fed Halfwave antenna and bal-un

prcguy

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Get a PAR quad band resonant EFHW, it will make the Comet look like a dummy load. You can build a similar 40/20/15/10m EFHW for a few $$ and they rock the air waves. I traveled around the country with an Elecraft KX3 and a home brew 40-10 EFHW and most people didn't believe that I was running only 10 watts. I have a Maldol and some other brand tapped vertical similar to the Comet and have made some contacts on 20 and 17m but those antennas haven't been used in years in favor of the vastly superior end fed.

Sitting here working out the antenna lengths and counterpoises for use with a Comet HFJ-350. Doing lot's of SWR sweeps and clips with the dykes.
 

wb4sqi

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Get a PAR quad band resonant EFHW, it will make the Comet look like a dummy load. You can build a similar 40/20/15/10m EFHW for a few $$ and they rock the air waves. I traveled around the country with an Elecraft KX3 and a home brew 40-10 EFHW and most people didn't believe that I was running only 10 watts. I have a Maldol and some other brand tapped vertical similar to the Comet and have made some contacts on 20 and 17m but those antennas haven't been used in years in favor of the vastly superior end fed.
Just received an Unun today at 30:1 ratio but easily changed to 49:1. I have had such good success with the PAR SWL antenna that I want to head that direction. What ratio Unun and length of wire did you use for the home brew PAR quad band?
 

prcguy

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49:1 transformer and about 64ft of wire, which is 1/2 wave on 40m and multiple resonant 1/2 wave on the other bands. The match is great on 40/20/15/10 and I wind up 64ft of 22ga Teflon wire and about 40ft of miniature parachute cord in a plastic chalk line reel. This antenna is very small, deploys in a minute or two and handles up to 100w. I think it would be a perfect companion for an IC-705 or any portable HF rig.

Just received an Unun today at 30:1 ratio but easily changed to 49:1. I have had such good success with the PAR SWL antenna that I want to head that direction. What ratio Unun and length of wire did you use for the home brew PAR quad band?
 

belvdr

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49:1 transformer and about 64ft of wire, which is 1/2 wave on 40m and multiple resonant 1/2 wave on the other bands. The match is great on 40/20/15/10 and I wind up 64ft of 22ga Teflon wire and about 40ft of miniature parachute cord in a plastic chalk line reel. This antenna is very small, deploys in a minute or two and handles up to 100w. I think it would be a perfect companion for an IC-705 or any portable HF rig.
Is this something you have a write up for? I’ve never built an antenna and would like to start with something simple that I can take with me.
 

prcguy

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Here is a picture of a 40/20/15/10m EFHW in a chalk line reel with 100 watt transformer and miniature Teflon feedline with common mode choke. Its very compact. After you pull out the 64ft of wire there is about 40ft of miniature para cord attached and the empty chalk line reel becomes your throw weight to toss over trees, etc.

100w end fed.jpg
 
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belvdr

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Here is a picture of a 40/20/15/10m EFHW in a chalk line reel with 100 watt transformer and miniature Teflon feedline with common mode choke. Its very compact. After you pull out the 64ft of wire there is about 40ft of miniature para cord attached and the empty chalk line reel becomes your throw weight to toss over trees, etc.

View attachment 92624
Since I’ve never built a transformer like that, any pics of the inside? This may be be too much for a first antenna.
 

prcguy

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Here is one of many sites that show how to make the transformer, its quite easy. http://www.infotechcomms.net/downloads/Multi_band_EFHW_spool.pdf

For 100 watts use an Amidon FT-114A-43 ferrite core available here: FT-114A-43
Then you will need a 125pf disc ceramic or dipped silver mica capacitor with a 200v or more rating and a small box that the transformer and capacitor will fit inside. I like to use a BNC connector for low power portable versions since it takes up less space on the box compared to an SO-239.

Just wind the transformer with some 22 to 16ga enameled wire, size not that critical and check the match with an antenna analyzer while placing a resistor about 2,500 ohms from the output to ground. The VSWR should be low across roughly 5Mhz to 30MHz. No need to cover the ferrite core with any tape as some articles show, just wind the wire right onto the core exactly as shown in the article.

Since I’ve never built a transformer like that, any pics of the inside? This may be be too much for a first antenna.
 

vagrant

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Here is a photograph of the one I made using the parts. It's all black box until you build one and realize how easy it is. It works very well. I previously setup a loop and this to do comparisons. The loop requires constant tuning and this just wins. Basically, this end fed has plenty of bandwidth which equals fun. That VSWR result using a RigExpert shows that a 705 will not require an antenna tuner. I use six 43 mix clip on ferrite beads with 25' of LMR-240UF coaxial cable. I may eventually make a pocket sized coax prcguy has with the winding over just one core.

(Never mind the 6m result and if I need to work 80 or 160 meters, I would build a separate antenna.)
EFHWsoto.jpgEFHWnaka.jpgOldDry.jpg

Actually, here are more detailed sweeps of those four bands. Start and stop are at the bottom. Yellow marker is freq at top and to the right of that is the SWR for that freq.
EFHW40m.jpgEFHW20m.jpgEFHW15m.jpgEFHW10m.jpg


Review this thread for details.


Since I’ve never built a transformer like that, any pics of the inside? This may be be too much for a first antenna.
 

belvdr

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Thanks for the tips. I guess my confusion started by reading one guide and it wasn’t really clear. I’ll take a look at these tonight.
 

tweiss3

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Here is a picture of a 40/20/15/10m EFHW in a chalk line reel with 100 watt transformer and miniature Teflon feedline with common mode choke. Its very compact. After you pull out the 64ft of wire there is about 40ft of miniature para cord attached and the empty chalk line reel becomes your throw weight to toss over trees, etc.

View attachment 92624
I really like that method for storage and use. I may have to do something like that as well.

Here is one of many sites that show how to make the transformer, its quite easy. http://www.infotechcomms.net/downloads/Multi_band_EFHW_spool.pdf

For 100 watts use an Amidon FT-114A-43 ferrite core available here: FT-114A-43
Then you will need a 125pf disc ceramic or dipped silver mica capacitor with a 200v or more rating and a small box that the transformer and capacitor will fit inside. I like to use a BNC connector for low power portable versions since it takes up less space on the box compared to an SO-239.

Just wind the transformer with some 22 to 16ga enameled wire, size not that critical and check the match with an antenna analyzer while placing a resistor about 2,500 ohms from the output to ground. The VSWR should be low across roughly 5Mhz to 30MHz. No need to cover the ferrite core with any tape as some articles show, just wind the wire right onto the core exactly as shown in the article.
My understanding of the MyAntennas EFHW offerings is they are the exact same thing, a 49:1 un-un transformer, and the one I have works fantastic. None cover 6m, but having a few different spools of wire length (254', 133' & 64') to toss on the transformer would get just about any coverage you want in a tiny package.

Here is a photograph of the one I made using the parts. It's all black box until you build one and realize how easy it is. It works very well. I previously setup a loop and this to do comparisons. The loop requires constant tuning and this just wins. Basically, this end fed has plenty of bandwidth which equals fun. That VSWR result using a RigExpert shows that a 705 will not require an antenna tuner. I use six 43 mix clip on ferrite beads with 25' of LMR-240UF coaxial cable. I may eventually make a pocket sized coax prcguy has with the winding over just one core.

(Never mind the 6m result and if I need to work 80 or 160 meters, I would build a separate antenna.)
View attachment 92625View attachment 92626View attachment 92627

Actually, here are more detailed sweeps of those four bands. Start and stop are at the bottom. Yellow marker is freq at top and to the right of that is the SWR for that freq.
View attachment 92628View attachment 92629View attachment 92630View attachment 92631


Review this thread for details.
See above. I think you can buy just the transformer from some places as well if you don't want to build your own.

This makes the antenna part of the equation much simpler now that I see it.
 

wb4sqi

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I bought my transformer from "eddieson" on Ebay for $5 plus shipping. configured as 30:1 ratio but can be altered to 49:1 easily. Available with BNC or SO-239 antenna receptacle. Small enough to fit in a large pill bottle or similar container, something that can be made waterproof.


Where is a good source for the teflon wire?
 

prcguy

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tweiss3

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Ebay is the best place to find Teflon wire and sometimes local hamster fest swap meets. I've purchased 1,000ft rolls of 16ga and 22ga Teflon wire for $30 plus shipping. You have to check Ebay often as others will buy it up cheap then try to sell it by the foot for ridiculous prices to the audiophiles.
Ebay seems to be much better priced.

What size paracord do you use? I have a spool of 3/16" sitting in the garage, but that seems way too large for this application. I think I need to make one of these in 40 just to have sitting around. Plus, an inexpensive project is always nice to have when one feels like doing something.
 

belvdr

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I bought my transformer from "eddieson" on Ebay for $5 plus shipping. configured as 30:1 ratio but can be altered to 49:1 easily. Available with BNC or SO-239 antenna receptacle. Small enough to fit in a large pill bottle or similar container, something that can be made waterproof.


Where is a good source for the teflon wire?
How do you modify it to 49:1? I had a MyAntennas setup at one time at the house, but took it down and cannot find it. :/
 

Mikejo

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I am thinking of Building an EFHW for 80m - ? What are your thoughts about using a type 31 Mix for the Torroid?

:unsure:
 

prcguy

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No. For a single large core good for about 400w SSB use an FT-240-43 mix. For two cores stacked good for about 800w SSB use FT-240-61 cores. For three stacked cores and probably 2kW power handling use three FT-240-52 cores.

I am thinking of Building an EFHW for 80m - ? What are your thoughts about using a type 31 Mix for the Torroid?

:unsure:
 

Mikejo

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Too Bad, They are supposed to be good up to 200MHz, I ordered them already.

Why then is the 43 mix better?
 
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