Topics

Links for End Fed Antenna Design / Testing and Ugly Balun Chokes


Brian Gohl - AI6US
 

We had some discussion this morning about the General class lab's end fed antennas not tuning up as expected. I believe that there were three reasons that the antennas tuned up on some bands, but not on others. 
1. No counterpoise - I have found low SWR if using 16' or more feedline provides 
2. No Impedance coil - Have read about the effect on 15/12/10 tuning
3. No choke - Have found the choke is necessary for reliable tuning and RFI elimination

Here are a few links that I have found to be informative.

End Fed Wire Design and Build:
www.infotechcomms.net/downloads/Multi_band_EFHW.pdf
www.hamfest.w7yrc.org/wp-content/uploads/2019/06/EFHWslides.pdf

"Ugly Balun" Choke Build and Examples: 
www.hamuniverse.com/balun.html
--
Brian- AI6US


Dennis - WU6X
 
Edited

Yes, trying to match the approximate 3.3k ohms input impedance of an end fed to 50 ohms is virtually impossible without some kind of matching transformer. A counterpoise will help, but you still need to overcome that input impedance.
 
If you look at the multi-band verticals being produced by several manufacturers, you will find two such toroid transformers in that little box at the bottom. These manufacturers have also figured out how to fool RF into thinking it has a ground plane available, with small radials for each band. A vertical antenna fed at the bottom is pretty much the same thing as a horizontal wire, only vertical. Most manufacturers are recommending these new verticals be mounted at least 10' from the ground as well.

Dennis, WU6X
 
 


From: sfarc@w6ek.groups.io <sfarc@w6ek.groups.io> on behalf of Brian Gohl - AI6US <ai6us@...>
Sent: Sunday, November 15, 2020 11:46 AM
To: sfarc@w6ek.groups.io <sfarc@w6ek.groups.io>
Subject: [from W6EK Groups.io] Links for End Fed Antenna Design / Testing and Ugly Balun Chokes
 
We had some discussion this morning about the General class lab's end fed antennas not tuning up as expected. I believe that there were three reasons that the antennas tuned up on some bands, but not on others. 
1. No counterpoise - I have found low SWR if using 16' or more feedline provides 
2. No Impedance coil - Have read about the effect on 15/12/10 tuning
3. No choke - Have found the choke is necessary for reliable tuning and RFI elimination

Here are a few links that I have found to be informative.

End Fed Wire Design and Build:
www.infotechcomms.net/downloads/Multi_band_EFHW.pdf
www.hamfest.w7yrc.org/wp-content/uploads/2019/06/EFHWslides.pdf

"Ugly Balun" Choke Build and Examples: 
www.hamuniverse.com/balun.html
--
Brian- AI6US

--
Dennis - WU6X


Jef - N5JEF
 

Brian -

I think all of the antennas were verified with excellent to usable SWR on 40, 20, 15 meters, but slightly over 2:1 on 10 meters.

I wasn't directly present for the testing of the first one, but understood that it was confusing at first because the owner had hands near or on the high-impedance tip of the antenna.

I really don't know how good should be expected at 10 meters, with that toroid selection, and with the fudge factor of the capacitor added across the input connector.

What information were you going on?

- Jef


On Sun, Nov 15, 2020 at 11:46 AM Brian Gohl - AI6US <ai6us@...> wrote:
We had some discussion this morning about the General class lab's end fed antennas not tuning up as expected. I believe that there were three reasons that the antennas tuned up on some bands, but not on others. 
1. No counterpoise - I have found low SWR if using 16' or more feedline provides 
2. No Impedance coil - Have read about the effect on 15/12/10 tuning
3. No choke - Have found the choke is necessary for reliable tuning and RFI elimination

Here are a few links that I have found to be informative.

End Fed Wire Design and Build:
www.infotechcomms.net/downloads/Multi_band_EFHW.pdf
www.hamfest.w7yrc.org/wp-content/uploads/2019/06/EFHWslides.pdf

"Ugly Balun" Choke Build and Examples: 
www.hamuniverse.com/balun.html
--
Brian- AI6US


Brian Gohl - AI6US
 

It was mentioned by Orion on the net this morning that the endfed antennas tuned up good on 80/40, Ok on 20 and not so great on 15/10m. 
Orion asked me to post these links onto Groups.io as they provide possible solutions and design changes to the lab design.

Best Regards! 
Brian Gohl - AI6US 
(916) 770-7751 cell


-------- Original message --------
From: Jef - N5JEF <jef@...>
Date: 11/15/20 2:04 PM (GMT-08:00)
To: sfarc@w6ek.groups.io, "Brian Gohl (AI6US)" <ai6us@...>, Orion Endres <ai6jb@...>
Subject: Re: [from W6EK Groups.io] Links for End Fed Antenna Design / Testing and Ugly Balun Chokes

Brian -

I think all of the antennas were verified with excellent to usable SWR on 40, 20, 15 meters, but slightly over 2:1 on 10 meters.

I wasn't directly present for the testing of the first one, but understood that it was confusing at first because the owner had hands near or on the high-impedance tip of the antenna.

I really don't know how good should be expected at 10 meters, with that toroid selection, and with the fudge factor of the capacitor added across the input connector.

What information were you going on?

- Jef


On Sun, Nov 15, 2020 at 11:46 AM Brian Gohl - AI6US <ai6us@...> wrote:
We had some discussion this morning about the General class lab's end fed antennas not tuning up as expected. I believe that there were three reasons that the antennas tuned up on some bands, but not on others. 
1. No counterpoise - I have found low SWR if using 16' or more feedline provides 
2. No Impedance coil - Have read about the effect on 15/12/10 tuning
3. No choke - Have found the choke is necessary for reliable tuning and RFI elimination

Here are a few links that I have found to be informative.

End Fed Wire Design and Build:
www.infotechcomms.net/downloads/Multi_band_EFHW.pdf
www.hamfest.w7yrc.org/wp-content/uploads/2019/06/EFHWslides.pdf

"Ugly Balun" Choke Build and Examples: 
www.hamuniverse.com/balun.html
--
Brian- AI6US


--
Brian- AI6US