Ham Radio - Adding a 1:1 choke to the EFHW antenna.
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- Опубликовано: 20 мар 2022
- How well does a choke reduce noise? Pretty well.
Here's a video on the choke, if you're interested.
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Hi, every time I have a question about something ham radio or shortwave related, I look through your videos and more times than not I find the answer. Thanks for sharing your knowledge, your a great Elmer. Have a good day. 73
I'm glad it was helpful Derek. Thanks for watching.
Fascinating! I accidentally clicked the video, and I got 10 minutes of something I did not understand a word of. For me, a choke is found on older cars to get them to start. So much apparently that I am ignorant of.
There are few of us that understand rf and carburetor chokes
That device on the car chokes (or limits) air flow. This device chokes (or limits) interfering radio signals.
😂😂😂- you got to love You Tube. Even mistakes teach you something new.
Thanks Kevin. Always enjoy watching your videos. The EFHW is close to my heart, it's the only antenna i can put up in my small backyard here in Melbourne Australia. Keep up the good work. - VK3TWC/Trevor
Excellent video - thanks Kevin
Kevin, this is a year after the fact, I had to smile watching your opening. The EFHW/OCF crowd gets pretty rowdy over any perceived slight against their antenna. As Teddy said, walk softly and carry a big stick :)
Tnx Kevin. Appreciate your time.
Great video, solved my problem, thanks Kelvin
Well made choke, works well. 👍🤓
Thank you Kevin that was very informative.
Another well done and said video by you Kevin. I'm glad you are so prolific with your videos, I have a big catalogue to go back on. I find you to be one of the best Elmers on YT. Thanks for all you do. What was the rig software you were using in this video?
Rig software? Can you be more specific?
I like that new Senator Wash Ratt Pack sticker !!!
Great video Kevin! I have an EFHW at my home QTH and love it's performance on 160M-10M (MyAntennas). I have experimented with an RF Choke and it not only reduces SWR, RFI and general noise, but it also helps my 40M EFHW load up on 160/80M (probably not efficiently, but I make QSOs).
Question - I also experimented with a counterpoise on my EFHW and have always found it reduces performance and increases SWR. I tried it as a 'tuned' counterpoise wire and also connected to a ground stake. Either configuration reduced performance. I'm curious why you chose a counterpoise in this case and if you'd be wiling to try your EFHW without a counterpoise wire. 😀 73 KJ6ER
Hey Kevin, when I mount SO-239's inside a [thick] plastic box like this, there're sometimes not enough threads sticking through for say, an Amphenol PL-259 to seat into the teeth, allowing the 259 to spin without a fîrm connection. I now always mount on the outside giving this 259 all the possible threads and seat solidly. I'll use silicone in key spots to assure it's leak proof.
Threw some junk together 4 traps pieces of so makes a double dipole waiting for a 1 to q balun tried it last night on a antenna tuner on my short wave grundig satalite 800 worked very well with the tuner some channel switching tuner on or off very little change think ill build a choke see what it would do with led light bulbs smart battery charger going in the shed nice video
good video Kevin
Thanks Kevin, great video that gets me thinking. 73, K7KS
U read all the comments, because its realy intwresting and usefull lot i got from this
A really nice video. I guess you are an SWL. That might be a great subject for you to do videos on.
Thank you for teaching me by example how to read a waterfall display. This truly has been enlightening. 73 KN6ZVI
When building baluns, of all types I always include a common mode balun . It’s the way to do it properly.
Great info❗️👍🏻
Nice i formative video.i got many new things to know
Great! Thanks!
The half wave end fed ant is voltage fed not current fed so adding anything other than a common mode coax choke is a wast of time. The transmission line you have wound on the core is balanced also the character impedance of this line depends on the diameter of the wire and spacing. Secondly the impedance match allowing the antenna to be fed at its hi voltage point means that it does not require a counter poise as each 1/4 wave end becomes its own counter poise because of there phase diferance to each other. There is a lot of misinformation regarding this.
Yes, your results are the same that I found with my 40 meter EFHW. The choke removes the transmission line as being part of the antenna, ie antenna element. Thanks for sharing.
Excellent video. Thank you for sharing your knowledge! 73 Bret/AC0AE
Also good information, man. Remember not to burn out on the ham videos, your sound stuff was interesting too
This is great! Now I have another question... why does the 1:1 with a type 43 remove noise and the 49:1 with a type 43 NOT remove noise... Interesting video.
@@WECB640 I'd love to talk more. I grok the parallel lines part of the puzzle, I was leaving that out until you brought it up. Thanks!
Common mode noise travels on the outer surface of the feed coax (i.e. the outer ground shield). The signal feed not the shield feed goes through the 49:1 UNUN. So to the common mode noise on the outer shield there is no UNUN. In fact, EFHW antenna often use the outer shield as a counterpoise when an Earth ground is not used at the UNUN. As I recall, the feed coax length needed to be at least 1/8 max wavelength in length and that is where some folks insert the choke. I prefer the choke closer to the transceiver.
@@dreupen that makes a lot of sense. Thank you!!!
Because one is wound as a common mode choke, the other is just an impedance transformer.
Thanks Kevin! I’m thinking about installing them on the hamsticks in my truck to reduce ignition noise. I’ve tried some other techniques but not this yet. 73 de Chris K2CJB
The Noise Blanker on your radio is designed to reduce pulse type noise like ignition noise. Well, most HF radios have a noise blanker anyway.
@@loughkb It definitely does. IC 7100 NB is great. But…getting noise on weaker FM stations on vhf and uhf. So might try it there too. All about experimenting when it comes to antennas.
Great vid! Would a mix 31 core have cleaned up 40 meters a little better? Please forgive if already discussed.
I usually use a 4:1 on a off center fed dip[ole. It works very well..
Hi Kevin hope u are well, good comparison a common mode choke they do help an interesting way you wound that choke can u do a sketch drawing of it please
I have a video on it.
ruclips.net/video/9kY2rz2jizs/видео.html
Impressive results. 50% science, 50% witchcraft!
Good video. Is it necessary to make the wire cross over the diameter of the toroid? Or is it just something constructors do to make the wiring fit the enclosure neatly? Thanks Kevin.
It’s not necessary but it is certainly convenient. You’ll notice that the wires end where they would have if they weren’t wrapped around the big donut.
You seem to be overthinking this. The common mode choke simply stops the outside of the coax from being part of the antenna. So it'll stop picking up vertically polarized noise and weak signal sources close to the coax.
Great video Kevin. Do you have any suggestion as to the preferred location of the 1:1 choke? I currently have an EFHW on 40 meters with my 49:1 outside at the antenna feed point and a 1:1 choke inside my shack about 50 feet from the antenna feed point and 5 feet from my radio. Have you experimented with choke location?
I've used them at both ends with similar results. I had this one at the antenna end, but with about 4 feet of coax between the choke and the 49:1. I also had a short counterpoise wire from the 49:1 that went down to a ground rod.
Apparently my comment was deleted by YT, as I was referring to a link, which I didn't wrote completely as it should, but RUclips is way too clever, hi.
Anyway, (Google) search for 'AA5TB End Fed Half Wave Antenna', and there you will read that the recommended location of the 1:1 balun is 0.05 lambda away from the transformer.
So for the lowest band of that EFHW, let's say 40m, the coax between the 49:1 and the choke is 0.05 lambda = 2m.
Hope this helps, and my comment stays online ;o)
73, Patrick ON4CDJ
Hey Kevin. Do you have the video on how to make the Common Mode Choke you have in this video? Great videos btw!!
Yes. As usual, the link was in the description.
ruclips.net/video/9kY2rz2jizs/видео.html
Curious how type 2 toroid functioned as a choke Using type 2 for 9:1 unun
It is strange for me that antenna like "City Windom" which performs much better than EFHW isn't so popular.
Hi Kevin
Great tutorial!
Questions: What was the reason you replaced the original red toroid in the choke with a type 43 toroid.?
Would it not have worked OK?
Also do you have the wind details for the choke itself?
Thanks
Steve
The type 43 was more effective in the lower HF range, whereas the type 2 was more effective up into 6 meters.
And yes, I have a video on winding the choke. Search my channel for choke and you should find it.
Very interesting clip, cheers Kevin. I only thought a 1:1 choke was to stop RF on the braid of coax feeder and allowing more power to be transmitted ! In future I will always use a 1:1 choke to my antenna system, at home or portable. 73's Andy M6APJ.
You are correct. A common mode choke placed at the antenna does NOTHING to prevent the outer shield of the coax that runs from the balun to the radio from acting as an antenna. The CMC only prevents transmitted RF from looping back down and radiating off that segment of the coax.
How far from the feedpoint did you put the Choke ? I read they have to .05 wl from the feedpoint for the lowest freq of design.
I run a couple of Efhw on 40m my experience has been that adding a common mode choke about 3 meters from the 64:1 makes the antenna quieter decreases rf in the shack and actually improves the swr a hair…..I don’t use a box and fittings I just put the coax through a Toroid 9 times about 3 meters from the unun and tighten and tidy it with some zip ties
There is one potential problem with wrapping the coax through a toroid to make a choke. Those tight bends that you put in the coax can cause the center conductor to push its way through the dielectric insulation and make contact with the outer braid. It can happen over time.
@@loughkb I don’t wrap the coax very tight. …you don’t need to.
Try also putting a choke inline where the coax enters the house.
Think that coax coil you have between the UNUN and the choke will shorten the antenna slightly - have noticed that I have to unwind all coax before adjusting say dipole length
If coiling your coax alters how the antenna works, then the coax shield is working as part of the antenna and you need a choke.
@@stargazer7644 Indeed - and intentional. I made contact from Denmark to the US with a 5 meter vertical (Chameleon MPAS ) - and using the coax as counterpoise with a choke at the rig end. IF I have the coax rolled up - the SWR changes a bit - so I fully un-roll the 22 meters of coax I use
would it make any difference if you put a 1:1 choke at the feed point of a 40/20 link dipole or at the end of the coax just before the radio or both?
I know this is a different antenna than the video but it got me thinking about my link dipole, I have it mounted on the center support and it would be lighter if it was on the coax but I dont want to change the performance too much it works very well and is very portable
The further from the antenna, the higher probability the coax becomes a part of the antenna.
People need to stop assuming that "Hey this is cool, here it is compared to that" automatically means "that sucks"
Great Video! I wonder if using type 31 mix toroids rather than type 43 would produce better results on & below 40m? The specs for the two mixes show 31 mix as the better performance on lower frequency's. I use a bifilar wound design using 240-31 mix for my 1:1 common mode chokes as most common mode interference I have found is on the lower bands. 73, Tom G2NV.
I mentioned that but someone deleted my comment.
I haven't deleted any comments Steve. I've heard from others that comments didn't stay. I think youtube is having problems.
Or, someone else could be using the dot menu to 'report' comments. It's one annoying way a mental juvenile can mess with youtubers.
You might have a nemesis that looks for your comments on other videos.
@@loughkb Oh well. Anyway I wanted to mention that parallel wires have an impedance of around 75 to 100 ohms which can be the cause of the slightly elevated SWR. Using coax, RG8x or RG-400 around the core maintains the 50 ohm impedance. On my EFHW I went crazy and ran the coax through 4 cores about 2 inches apart. I used two 31 mix for the lower bands and 43 mix for the upper bands. There are no issues with weather exposure. Just let the rain keep them clean. I did run a 3/4" pvc pipe through them to make it look neater but not necessary. The impedance is additive when they are in series like that.. It also helps to run the coax from the transformer down to ground level and attach it to a ground rod then into the shack.
@@n4lq Does a coax wound core function just as effectively as a wire wound one like Kevin had? I have an RG8x wound core on my EFHW (only one, type 43 as that's what I had - now thinking of adding a type 31 as well!).
@@paulsengupta971 The wire wound version will cause a bump in the swr because it's not 50 ohms like coax. The best coax is Teflon, RG-400 because tight wrapping and heat won't hurt it. Yes, 31 mix is much better for 160, 80 and 40 meters. 43 mix takes over above 7 mhz. So just put one of each in series. More is better.
I have a DX Commander Classic vertical antenna and have all the elements tuned. I have it connected to a IC-7300 with 50ft of RG8X coax. I get a pulsating line and noise on the whole band that is even across the scope that is consistent about two times a second. It is not present on my ZS6BKW on my FTdx10 radio. Doesn't seem to matter what band I am on. I am going to try another coax cable. Any other ideas?
Probably something in your house is generating the noise. Run the radio off a battery go to your main breaker panel and turn everything off. And then if the noise goes away, turn your breakers on one at a time until the noise comes back then you know what circuit it's on and you can start to narrow down what's causing the noise.
Did you calculate the feed line length between feed point and choke or was it random? Some suggest at least 1/4 wave of coax from end fed before placing a choke. Your thoughts?
If you're not using a counterpoise wire off the ground side of the feed point, then the coax shield becomes your counterpoise and you probably would want at least an eighth wavelength with the end fed half wave design.
Hi iv got a 140 43 mix core spare and want to make a choke . I see you’ve used two wires rather than coax to do the winding can you suggest how you done that and how many turns I would need to cover 80 to 10 meters
I just wrapped the two wires in parallel. I don't like wrapping coax since the bend can cause the center conductor to push through the dialectric insulation and make contact with the outer braid.
At least 8 turns, no more than 12. Needs to be an even number so half will be on each side of the toroid. Syymetry is important.
If one is good, two in series should be even better right?
Can we use ferrous core instead toroid?
Please do a show on QCX+ firmware update using both the ardrundo and other methods. There is not very much on that on RUclips
Sure, send me a QCX+ and I'll get right on it. :-)
Where did you add the choke? Location matters I would think. At the entrance to the house? Antenna? Rig/Amp?
Is there any difference when TX with the common choke?
Thank you. 73
None that I'm aware of.
@@loughkb
Great. 73
hi, greatings from CE zone.
Ome question, which program Is the one that you use to see the NanoVna?
73's
xq6wbm
I don't have a nanoVNA. I have a miniVNA pro and I use their android app on my tablet.
@@loughkb thanks
Does this type of choke suppress the desired signal. Would putting toroids the coax be better 🤔 or worse.
I haven't noticed any insertion loss with this design and signals.
How do the 1 to 1s do with rfi. I have some in the shack and was told to but in a 1 to 1 at the antenna.
It can help to reduce RF on the coax, yes.
It's better to figure out why you're getting RF on the coax and fix that though. If you're using an end fed wire, where this problem is most common, you can add a counterpoise wire to the ground side of the feed point, going off perpendicular or away from the radiating wire. The RF current will go there instead of on the shield of the coax.
Is that suppose to be a common mode choke? Seems to be an odd way wind one, why did you do it that way?
I've seen it published in several places. I also tore down a commercial version once and it was also wound that way.
A mix 31 toroid should do a better job on noise suppression down at 40m.
ABC, Always Be Choke-ing as Professor Ape would say.
So the choke only reduces signals (noise) being picked up on the coax feeder. If these signals get picked up by the antenna, the choke makes no difference. Is that right? Then why is the hash predominantly picked up by the feeder? Why doesn't the wire antenna pick it up if it's there?
Broad hash noise will get picked up by the antenna as well. However, since it doesn't really have a defined waveform, it comes down the feedline in phase and common on both conductors.
Any kind of continuous wave signal, regardless of modulation, will be a wave moving across the wire and have different phase currents on the antenna wires.
Because the antenna is horizontal and the coax is hanging vertical. Most noise sources are vertically polarized and are picked up by the coax shield. The antenna is cross polarized to the noise.
But won't this stop the coax feedline acting as the antenna counterpoise?
yes, and that's a good thing. it prevents RF from getting back into the shack and possibly on to the modulation audio of your radio. of course you'll want to add a counterpoise wire to the ground side of the 49:1 balun.
@@loughkb Yes Ok, but maybe a point worth emphasising most of the 'received wisdom' about EFHW says that a counterpoise isn't needed because the coax outer is used.
@@Naybr1 That's marketing turning a bug into a feature.
What type of wire is used to make the choke?
Solid core, not sure of the gauge. I use solid for winding, it holds it's shape and is easier to work with.
👍👍👍
Phew! 😅
Interesting. Thank you. DE VY2MJ. 73.
👍👍👍👍✌️
You probably would have got better noise rejection by using mix 31 instead of mix 43.
🔴👍🏻🔴