Choke or Balun for End Fed Antenna

[AlaskaListener]

Good morning All,
I got my general license last month and I am looking to set up my first HF antenna. I sat through the Tech class and this subject wasn't addressed by the instructor and I wanted to get your input on the subject.

I am looking to install the EFHW-80-10 wire antenna at my house. After reading some forums I see some operators use a balun or choke while the manufactures website says it is not required. I plan to use the Yaesu FT-450D, I like the antenna as it claims to be multi-band. With that said, my main concerns are the RFI problems or even worse, the "hot mic." Can someone point me in the right direction for what I would need to install when I put this antenna up? The manufacture states the antenna doesn't need to be grounded if mounted high, instead ground the coax. I understand that but wanted some advice before doing this for the first time.

Thanks,
Ryan, KC1MWA

 

[belvdr]

I used one of their antennas for several years with no balun and no issues and it was about 25 feet above ground. There's a ground lug on the bottom next to the SO-239 connector that I connected to a ground rod.

 

[popnokick]

Our club has an EFHW 80-10 (MyAntennas) that we set up for Field Day events and other HF operations. We've never put an additional balun on the feed line coax and used only the one supplied with the antenna. We've never had RFI or the "hot mike" problem in multiple different setups.

 

[prcguy]

I've built a few dozen EFHWs and also have a couple from MyAntennas. A good 1:1 choke balun is a good idea for this type antenna and I recommend one. At resonance and in general they don't seem to light up the coax shield with RF but if you get a little ways out of resonance they will. A good choke balun will also help snuff out RFI riding on the coax from the shack up to the antenna and you can sometimes see a lower noise floor when using one. I usually place them closer to the radio so the antenna has some coax shield as a counterpoise if it needs that. I have never found a need to ground the EFHW at the transformer.

My Antennas happens to make the best most effective choke baluns I've seen but you can also make one using a ferrite core wrapping coax through it. A single FT-240-31 core costs about $7 and nine turns of coax through it makes an ok choke that should handle up to a kilowatt. A bunch of coax wound around a PVC form does not make a good choke.

 

[wbswetnam]

Just this afternoon I dug my 9:1 balun out of the junk box, and I connected it to 95' of 20 gauge wire to form an end-fed dipole, about 15' off the ground. It's only good on 40m and 10m, so it needs work obviously. I've gotten away from the hobby in recent years, but now that I'm stuck at home until the CV-19 crisis subsides, I have lots of time on my hands these days.

 

[prcguy]

Your 9:1 is a bit different than the OPs EFHW and the 9:1 types really need a good choke balun in the feedline as the coax is usually a radiating part of the antenna. You don't want any virus on your coax.

Just this afternoon I dug my 9:1 balun out of the junk box, and I connected it to 95' of 20 gauge wire to form an end-fed dipole, about 15' off the ground. It's only good on 40m and 10m, so it needs work obviously. I've gotten away from the hobby in recent years, but now that I'm stuck at home until the CV-19 crisis subsides, I have lots of time on my hands these days.

 

[wbswetnam]

Your 9:1 is a bit different than the OPs EFHW and the 9:1 types really need a good choke balun in the feedline as the coax is usually a radiating part of the antenna. You don't want any virus on your coax.

My feedline will be very short, only 20'. Do you have a choke balun to recommend?

 

[prcguy]

Here is the economy version of the MyAntennas choke. Its not cheap but you can spend more and get less performance. CMC-130S-3K 1-30MHz

These tubular chokes have several multiple wound cores inside targeting different frequency ranges and adding more isolation where other brands just have some ferrite beads stuck over coax inside the tube and at best those reach maybe 20dB of isolation. The MyAntennas esonomy choke hits over 40dB of isolation at some freqs.

With 20ft of feedline and a 9:1 balun type antenna I think a 3ft jumper from the radio to the choke then 20ft of coax to the antenna would be fine. That would be preferred over putting the choke at the antenna since a 9:1 will benefit from using the coax as a counterpoise/radiator.

My feedline will be very short, only 20'. Do you have a choke balun to recommend?

 

[m6fud]

You don't need to spend a lot to make an effective 1:1 choke for an end fed.

Built from instructions from the choke expert K9YC.

This has 10,000 ohms (resistive) at the low end (1.8 mhz) and about 4,000 at 30 mhz.

Materials: 2 cores 240 - 31 purchased from KF7P Metal Werks. 10 foot of RG400 coax from Amazon.

12 turns around each core.

PVC 3/4" pipe optional. I used my grinder to shave it down for a fit. It does not affect the choke.

This will be installed .05 wavelengths ( 13.7 feet @ 3.5 mhz) from the transformer.

(Taken from a post by Steve Ellington who runs an end feds group on Facebook).

or there are also plenty of reasonable kits where you can buy everything needed to build something more portable, for example

Common mode chokes Archieven - HF kits

Common mode chokes

www.hfkits.com

Hope that helps.

 

[prcguy]

That's a great choke for 160 through 40m but its got too many turns for general purpose 80 through 10m use. Roll it back to 9 turns on each core and it will mellow out with less resistive choking on 160 and more on 10m. Or replace one core with a 52 mix and keep the 12 turns on each, that will have one core favoring the low end and one the high end and they will complement each other.

The best prices I've found on FT-240-31 cores is from Pro Audio Engineering at $6 each ($1.95 cheaper than KF7P) but he doesn't carry the 52 mix.

Fair-Rite 2.4″ Toroid Core - Pro Audio Engineering

Fair-Rite 2.4″ Toroid Core(2.4″OD x 1.4″ID x 0.5″L) P/N: 33-430 ——————————————————————————– Quantity: 1, Price: $7.00 ea Shipping Status: Immediate, In Stock ——————————————————————————– Quantity: 4-pack $6.75 ea, Price: $27.00 Shipping Status: Immediate, In Stock...

proaudioeng.com

Even with that I still keep a couple of MyAntennas common mode chokes around because he has the magic formula figured out with a much better distribution of choking resistance across the bands. Yea they are a little pricey but there are other brands that cost the same and only have a fraction of the performance.

You don't need to spend a lot to make an effective 1:1 choke for an end fed.

Built from instructions from the choke expert K9YC.

This has 10,000 ohms (resistive) at the low end (1.8 mhz) and about 4,000 at 30 mhz.

Materials: 2 cores 240 - 31 purchased from KF7P Metal Werks. 10 foot of RG400 coax from Amazon.

12 turns around each core.

PVC 3/4" pipe optional. I used my grinder to shave it down for a fit. It does not affect the choke.

This will be installed .05 wavelengths ( 13.7 feet @ 3.5 mhz) from the transformer.

(Taken from a post by Steve Ellington who runs an end feds group on Facebook).

or there are also plenty of reasonable kits where you can buy everything needed to build something more portable, for example

Common mode chokes Archieven - HF kits

Common mode chokes

www.hfkits.com

Hope that helps.

 

[AlaskaListener]

I purchased the EFHW 8010 and it should arrive tomorrow. I got the choke as well and will see if I end up needing it. With the radiation pattern being broadside along the wire, how close can the feed point be to my shack? If I install the transformer box outside my window and run the wire directly away from me, would I be ok? The coax will be choked and I don’t think the signal will radiate towards me if I’m “in-line” with the antenna wire. Thoughts?

 

[popnokick]

When you install your EFHW 8010 (or any end-fed) it's best to either a) get both ends of the entire antenna as high as you can in the air and run coaxial cable from the feed transformer / balun back to your radio, or b) install the antenna as a "sloper" with the coax feed end at least 10 feet off the ground and the distant end as high in the air as you can get it (but not vertical). The RF pattern of an EFHW antenna varies by the type and height of your installation but generally is omnidirectional... meaning that it is going to radiate in all directions. The feed point can be very close to your shack.... typically on the outside of the building with the coax running down from the point where you've attached the balun to the building or other support into your shack. Installation in this manner is not going to produce direct RF from the radiating element at any significant level in your shack. MyAntennas has an F.A.Q. with info on radiation patterns and installation considerations here -
EFHW antennas F.A.Q

 

[prcguy]

The 8010 EFHW will be broadside on 80m but on 40m it will have a 4 lobe pattern like a clover leaf, on 20m it will have 8 lobes and so on, so you might get a gain lobe into your shack on some band(s). Not a big deal unless you run full legal limit and high duty cycle like RTTY.

I have a MyAntennas 80-10 OCFD running the length of my house right over me and I run lots of power, but SSB is low duty cycle and I don't talk all that long so it doesn't exceed FCC exposure limits. Interesting thing is I get no interference to anything in my house running legal limit.

I purchased the EFHW 8010 and it should arrive tomorrow. I got the choke as well and will see if I end up needing it. With the radiation pattern being broadside along the wire, how close can the feed point be to my shack? If I install the transformer box outside my window and run the wire directly away from me, would I be ok? The coax will be choked and I don’t think the signal will radiate towards me if I’m “in-line” with the antenna wire. Thoughts?

 

[AlaskaListener]

When you install your EFHW 8010 (or any end-fed) it's best to either a) get both ends of the entire antenna as high as you can in the air and run coaxial cable from the feed transformer / balun back to your radio, or b) install the antenna as a "sloper" with the coax feed end at least 10 feet off the ground and the distant end as high in the air as you can get it (but not vertical). The RF pattern of an EFHW antenna varies by the type and height of your installation but generally is omnidirectional... meaning that it is going to radiate in all directions. The feed point can be very close to your shack.... typically on the outside of the building with the coax running down from the point where you've attached the balun to the building or other support into your shack. Installation in this manner is not going to produce direct RF from the radiating element at any significant level in your shack. MyAntennas has an F.A.Q. with info on radiation patterns and installation considerations here -
EFHW antennas F.A.Q

My shack is an upstairs room unfortunately so that would put my transformer about 15ft above ground. I can probably get the other end up 40ft or more and slope it that way. Ill only be running 100watt, no amp now or planned in the near future.

 

[AlaskaListener]

The 8010 EFHW will be broadside on 80m but on 40m it will have a 4 lobe pattern like a clover leaf, on 20m it will have 8 lobes and so on, so you might get a gain lobe into your shack on some band(s). Not a big deal unless you run full legal limit and high duty cycle like RTTY.

I have a MyAntennas 80-10 OCFD running the length of my house right over me and I run lots of power, but SSB is low duty cycle and I don't talk all that long so it doesn't exceed FCC exposure limits. Interesting thing is I get no interference to anything in my house running legal limit.

Thanks for this. I’ll be at 100watt max. Interested in DX, and shack is upstairs. I have a couple plans floating around in my head right now but this one seems to be the easiest. Mostly worried about RFI, I got that choke you recommended too.

 

[popnokick]

My shack is an upstairs room unfortunately so that would put my transformer about 15ft above ground. I can probably get the other end up 40ft or more and slope it that way. Ill only be running 100watt, no amp now or planned in the near future.

Perfect! The higher up you have the ends the better. So I assume you'll be attaching the feed transformer outside the building at 15-20 feet above the ground and running the coax into the shack via a short run through a window or other passthru? Run your ground line from the lug on the transformer in as straight a path as you can to the ground.

 

[AlaskaListener]

Perfect! The higher up you have the ends the better. So I assume you'll be attaching the feed transformer outside the building at 15-20 feet above the ground and running the coax into the shack via a short run through a window or other passthru? Run your ground line from the lug on the transformer in as straight a path as you can to the ground.

Yes, overall that’s the plan. Transformer will mount to the side of the house. It’s aluminum siding but the eave is wood. That transformer would be on the same wall as the radio room just on the exterior side, if that’s not a problem. There is an existing hole in the room too that leads to the outside from an old satellite tv coax. I will use it to pass the antenna coax through. Coax length is 25 feet. I will get a jumper coax for the choke, can the choke be inside the radio room?

 

[prcguy]

I like to have a length of coax before the choke to give the antenna some counterpoise. In general the EFHW antennas do not need a counterpoise or light up the coax with any measurable RF within their resonant areas but if you get out of band where the match is band they will light up the coax. I think giving the antenna 20ft or so of coax as a counterpoise before the choke might help if you ever use the antenna out of band or for receiving SW, etc.

If you got one of the MyAntennas chokes they are very effective and I don't see any reason not to bring the coax inside to the choke then use a short jumper to the radio. I would place the choke downstream of any other cables like computer or power supply, etc, as that can induce noise onto your coax where it can travel up to the antenna. If the choke is placed after any point where noise can get onto the coax then you might get a slightly lower noise floor on receive.

I've used dozens of EFHWs, mostly 40-10m versions and portable where some were only 6ft off the ground and others I could get up at 25-30ft. In all cases they worked very well but higher is better. I think getting it about 1/4 wavelength high on 40m is ideal because that will give you great NVIS coverage on 40m plus it will also do fine on DX then its 1/2 wavelength high on 20m and a full wavelength on 10m giving you a low angle for DX.

There is also a mod for the 80-10 version for SSB/phone operators. These antennas cover all of 40m and up with a good match but 80m resonates down around 3.55Mhz and in the common 3.8 to 4MHz phone band the match is 3 or 4:1. If you cut the antenna 67ft from the end insulator, attach another insulator and bridge that with a several kV rated 250pf capacitor, it moves the 80m resonant point near 3.9MHz and it will cover the phone portion of 80m without a tuner. I used a 7kV rated doorknob cap I got on Ebay cheap and it works great. I can work all bands now 80 through 10m including WARC with no tuner, I just plug the antenna into my amp and talk.

Yes, overall that’s the plan. Transformer will mount to the side of the house. It’s aluminum siding but the eave is wood. That transformer would be on the same wall as the radio room just on the exterior side, if that’s not a problem. There is an existing hole in the room too that leads to the outside from an old satellite tv coax. I will use it to pass the antenna coax through. Coax length is 25 feet. I will get a jumper coax for the choke, can the choke be inside the radio room?

 

[AlaskaListener]

I like to have a length of coax before the choke to give the antenna some counterpoise. In general the EFHW antennas do not need a counterpoise or light up the coax with any measurable RF within their resonant areas but if you get out of band where the match is band they will light up the coax. I think giving the antenna 20ft or so of coax as a counterpoise before the choke might help if you ever use the antenna out of band or for receiving SW, etc.

If you got one of the MyAntennas chokes they are very effective and I don't see any reason not to bring the coax inside to the choke then use a short jumper to the radio. I would place the choke downstream of any other cables like computer or power supply, etc, as that can induce noise onto your coax where it can travel up to the antenna. If the choke is placed after any point where noise can get onto the coax then you might get a slightly lower noise floor on receive.

I've used dozens of EFHWs, mostly 40-10m versions and portable where some were only 6ft off the ground and others I could get up at 25-30ft. In all cases they worked very well but higher is better. I think getting it about 1/4 wavelength high on 40m is ideal because that will give you great NVIS coverage on 40m plus it will also do fine on DX then its 1/2 wavelength high on 20m and a full wavelength on 10m giving you a low angle for DX.

There is also a mod for the 80-10 version for SSB/phone operators. These antennas cover all of 40m and up with a good match but 80m resonates down around 3.55Mhz and in the common 3.8 to 4MHz phone band the match is 3 or 4:1. If you cut the antenna 67ft from the end insulator, attach another insulator and bridge that with a several kV rated 250pf capacitor, it moves the 80m resonant point near 3.9MHz and it will cover the phone portion of 80m without a tuner. I used a 7kV rated doorknob cap I got on Ebay cheap and it works great. I can work all bands now 80 through 10m including WARC with no tuner, I just plug the antenna into my amp and talk.

I just measured the height to the eaves. It’s 19.5ft. So not exactly what I was hoping. My other plan just to put it here for you guys to see was to run the 25ft coax thru the hole to the yard, put the choke in, and then the EFHW is coming with an additional 100ft coax, so I’d connect it and run it to a tree in the yard, transformer up about 10ft so I can stick my copper pole in and connect it and slope the other end as high as possible. Using the eave, I can’t ideally ground the box or coax being on the second floor.

 

[prcguy]

Grounding the transformer or the coax will have no effect on performance and it can sometimes bring noise into the system. However, you should always ground to the NEC.

I just measured the height to the eaves. It’s 19.5ft. So not exactly what I was hoping. My other plan just to put it here for you guys to see was to run the 25ft coax thru the hole to the yard, put the choke in, and then the EFHW is coming with an additional 100ft coax, so I’d connect it and run it to a tree in the yard, transformer up about 10ft so I can stick my copper pole in and connect it and slope the other end as high as possible. Using the eave, I can’t ideally ground the box or coax being on the second floor.