DIY Simple & Effective HF RF Choke

A ferrite choke design based on the research of G3TXQ (SK). See www.karinya.net/g3txq/chokes/
Takes around an hour to build. You will need 1m of RG58 coax which leaves a bit spare.
Ferrite purchased from www.mouser.co.uk
ps. I did notice some condensation on the choke at the end of the video, so I added a vent.
Hope you find this video useful!
There are other amateur/ham radio related videos on this ianxfs channel. Feel free to browse and subscribe 👍🏻
Ian.

[@r7eagle_]

K9FS here. You have one of the best explained videos on making the 1:1 RF choke. Nice work.

[@ianxfs]

Thanks! Hope it’s of use 👍🏻

[@saa8488]

Thank you for the informative how-to. Your exquisite back yard is the unsung hero in this video. Very serene.

[@ianxfs]

S Aa Thanks! Yes the garden is starting to look good again after winter, so soon be a lush green again like in the video 👍🏻

[@garyclark1000]

Best example and explanation of toroid choice regarding frequency coverage and practical examples of how to build ! excellent, thank you very much.

[@ianxfs]

Thanks Gary!

[@julianrobertson3303]

Thank you for sharing . I have made the same choke , except for the connectors I have used PL259 plugs with SO239 inline bulkhead connectors , this method insulates the internal coax conductor & the entire coax connections eliminating any signal loss , this method requires a slightly larger enclosure to allow for the two SO239 bulkhead chassis connectors & the PL259 plugs , this provides a totally isolated system with no exposed inner core .

[@ianxfs]

Great 👍🏻

[@acestudioscouk-Ace-G0ACE]

Nicely explained demonstration and a sturdy job. Interesting to see that you had some condensation in the box on the wall. It's really good to see a video which is "real world" rather than "TV perfect". Thanks Ian.

[@ianxfs]

Thanks! Yes, I think I put in the description (🤔) I subsequently drilled a small vent hole in the base and protect the hole with a very small piece of net curtain (to stop insects). It seems the air trapped in the weather-proof box still heats/cools and condenses as a result. I guess it can’t be large amounts, but I’ve done the same on another choke too 👍🏻 Thanks for watching 😀

[@acestudioscouk-Ace-G0ACE]

@@ianxfs Thanks for the reply Ian. I had seen that you mentioned drilling a hole in your notes...seeing the condensation was a good practical reason to see why you need a hole. As you say the box is sealed so in theory, if you included some silicon chips to absorb the moisture from the air in the sealed chamber...you wouldn't need to drill a hole. Theory always sounds great, I bet the practic3 is different! LOL I enjoy your videos and that of the Callum Crew. Keep up the good work! 73s Ace G6XIB

[@gsansoucie]

Thanks for the link, I found a box of 4 FT240-43 toroids in my shack and happen to need a decent choke where I feed my coax (rig-58) in through a window for a temp setup. When I am sending on 80m, my wife’s hobby light keeps flashing. I’d say I have some RF coming in on my Random Wire antenna.

[@ianxfs]

gsansoucie ok good luck!

[@ScientistPrepper]

Really a great video. Thank you for showing how to do this practically.

[@ianxfs]

Thanks!

[@marklowe7431]

Why anyone would buy and not not make the effort to learn and build is beyond me. There's so many people willing to help.

[@ianxfs]

Thanks!

[@svtelos4726]

Thanks Ian. BTW...love the garden and the Koi. :)

[@ianxfs]

Thanks! Yes, looking forward to spring/summer again 🌺👍🏻

[@James_Bowie]

Excellent presentation. Many thanks!

[@ianxfs]

James Bowie Thanks James.

[@MM3KZD]

Excellent presentation many thanks. Stuart

[@ianxfs]

Stuart Corstorphine Thanks Stuart. Hope it helps!

[@Joe-KN4IFI]

Great vid Ian. Going to have to give it a try. 73 Joe

[@ianxfs]

Joseph Rostochak KN4IFI Great! Have fun Joe! 😀

[@donalfinn4205]

Nice garden too! Subbed.👍🇨🇮

[@ianxfs]

Great! Thank you 👍🏻

[@twong689]

I did mine with a RG-58 cable assembly without the box. I used heat shrink to protect the choke.

[@ianxfs]

Yes good point Tim! Mine was to insert into an existing set-up, so I went for the box.

[@twong689]

@@ianxfs I go for the simple solution. Once it is installed, no more PC freezes.

[@MrBanzoid]

Great instructions Ian. 73 Malcolm

[@ianxfs]

MrBanzoid Thanks Malcolm! Built this morning 👍🏻

[@Songdisciple]

Thank you, for this example.

[@ianxfs]

Tahoma No problem. Glad it was of use 👍🏻

[@paulsharp5473]

Excellent video. Why did you choose 12 turns and not 8? 8 turns on the chart shows more of a resistance result over the HF bands which was recommended.

[@ianxfs]

Hi Paul. If you’re on Steve’s webpage, go to the specific ferrite links below the main tables. There’s one for type 31 and these differ from the main summary table. Based on the spread of resistive properties as well as the green impedance I thought 12T looked a better spread. I’ve had no CMC issues on my OCFD at 200w over 40-6m since install 3 years ago. Happy with that. Good luck if you’re building your own 👍🏻

[@brianneal2207]

Hi Ian great little project replicated it and putting it to work in the antenna system thanks for all your videos just great and inspiring. Brian 2e0tcu

[@ianxfs]

Good one Brian! Glad it was of use 😀

[@g0fvt]

Hi, fwiw in theory RG58 can suffer from the centre conductor migrating when wound like this round a tight radius, I must admit that it does not seem to have bothered a common mode choke I put together decades ago. I have bought RG142 for a new QRO balun, it is teflon dielectric and jacket, not terribly easy to strip the ends but it will not melt with a soldering iron. FWIW my observations suggest that power handling is hugely affected by the level of imbalance that the balun has to deal with. Very clear description of the construction in your video 73

[@ianxfs]

Thanks! Yes, seems to be ok as now been in use on two antennas for about 1.5 years, with 200w RF 👍🏻

[@g0fvt]

@@ianxfs thanks for the reply, fwiw I have checked the bending radius in the datasheets, RG58CU marginally wins over RG142 although RG142 has a tiny bit less loss.

[@ianxfs]

g0fvt ah right...worth checking then 👍🏻

[@jfrphoto01]

@@g0fvt For the length of coax that you are using to make these 1:1 Ununs, loss is not a factor.

[@g0fvt]

@@jfrphoto01 not normally no.

[@russozard2626]

Thanks for a well demonstrate vlog I will be making one soon 73

[@ianxfs]

Great Russ!

[@shizzle666440]

Great video mate do you remember where you purchased the so239 connectors from.

[@ianxfs]

Hi James, no sorry. All online ham/amateur radio retailers will stock them and also the outside four-screw ones as well. You’ll easily source them. Have fun!

[@davidrobinson2573]

Hi Ian great tutorial just want verifcation Did you use RG8 or RG58 and would it make much difference thank you Dave M3xie

[@ianxfs]

David Robinson Thanks David! RG58. As long as it’s 50 Ohms and you can wind it around the toroid and it is spec’d for the power you’re using, then you’ll be fine. 73. Ian.

[@whamni]

Great video, I thought you would have put the choke near the antenna feed point !

[@ianxfs]

Alec M Yes Alec, but the OCFD already has a 4:1 balun at its centre, so a choke as well would be too much sag. It’s at the closest point where the coax meets the wall. I have another on my ground mounted vertical, but again, a few feet away from the base in the centre of the lawn so as not to be obtrusive or a trip hazard. All still work fine 👍🏻

[@whamni]

@@ianxfs As long as it works that's what matters lol thanks for the reply

[@sergio47934]

Hi fron CHILE, EXCELENT VIDEO, one cuestion. what powes is max. ???? thank

[@ianxfs]

Sergio Del Gaudio Hi Sergio! I don’t know what the max is for sure. It will manage 400w which is the UK maximum, but looking around at other websites I think it will go to 1Kw. You could also stack 2 of the ferrite cores on top of each other and wrap coax round them both together for an even higher power, which increases the choking effect too. As long as you don’t exceed the coax limits 👍🏻 Note: I did drill a small vent hole at the bottom to let it breath. Hope this helps! 73 Ian.

[@ur5gcl90]

Карпы понравились!

[@ianxfs]

🐟👍🏻

[@mrtablet4662]

Good video and explanation. After fitting did you notice much difference on the bands?

[@ianxfs]

Thanks. Yes it removed the common mode current on my off-centre fed dipole coax. I also fitted one to my ground mounted multi-band vertical, but there wasn’t a problem with than antenna to start with. Just for good measure. All good 👍🏻

[@mrtablet4662]

@@ianxfs thanks Ian, I might have to investigate one of these.

[@chrisbartlett6022]

Hi Ian, just watched this again. Wondering if I wind the ferrite on the end of my RG58 cable to the antenna if I actually need an enclosure? Have you any opinion as to the power handling for this choke, you say you regularly use 200w, would it be OK for 400w I wonder. Thanks for the videos :-)

[@ianxfs]

Yes & yes Chris. If you can avoid the box and additional connections then all the better 👍🏻 From what I’ve researched, 400W on that core and coax is fine 😀

[@chrisbartlett6022]

@@ianxfs Thanks very much. I have ordered type 43 for mine. Have some silicone wire too so going to try 2 ways of doing it.

[@ralph9987]

thanks for making the video did you check to see if there was a 50 ohm impedance match for your choke? cheers

[@ianxfs]

Ralph Kluge Hi Ralph. I used the club’s MFJ analyser with the choke inline with the antenna and the SWR etc. was all ok if I remember correctly. Anyway, it’s been fine in operation for over a year now and this model is in use on two antennas without ill effect. Ian.

[@ralph9987]

ianxfs I just tried it with a #43 instead and the swr is flat until 16mhz then shoots up. I wouldn’t have thought there would be such a difference. So think I may need to try another piece of rg58

[@ianxfs]

Ralph Kluge Sorry Ralph. KZbin didn’t inform me of this message, so I missed it! Hope you got sorted ok? I’m not sure why the swr changed? Seems odd... Ian

[@pu4mksmarkussalustianosalu783]

Parabéns muito bom Pará antenas liminar retorno rf

[@ianxfs]

Obrigada!

[@dennisspender402]

I've struggled soldering the coax to the SO 239. I see yours have "tabs" to solder to. Where did you get those SO 239s?

[@ianxfs]

Hi Dennis. I can’t recall, but the shield part of the socket should have the disk with solder tab attached otherwise you’ve got nowhere to attach to. Mine will have been online from one of the few online uk stores. Good luck!

[@sreekumarUSA]

Sir, Thanks much for the educative and informational Video on Chokes. I'm new to SWL, and not into transmission.(Basically interested in SWL ONLY) My equipments are YAESU FRG-7 and FRG-7700, both satisfactory functional. My antenna is "Random Wire" flung out of the window. My signals are quite good on 160 Meter Band to 41 Meter Bands. The Antenna Balance device has not been connected, as yet. That'd take place at the later part of May. The question is, since I'm only into SWL; is there separate Choke for Receivers; or can I use this Choke in my antenna circuit? Thanks in advance and an acknowledgement will be highly appreciated. Stay safe, Sir and Bless you. 73s

[@ianxfs]

Sree Kumar Thanks for the nice comments Sree! I don’t think it’s a necessity to have an rf choke when you’re just listening, but they do block common mode currents on the shield of the coax, so they may help. It depends on each person’s situation. If you’re not having interference or noise problems, then you’re probably fine. You can always add a choke and see if things improve. It won’t hurt, so for a little cost and effort, it may be worth a try. Enjoy your SWLing 👍🏻

[@sreekumarUSA]

Sir, Thank you for the rapid response. Presently the Random flung wire antenna on the Oak trees do a commendable reception on both the receivers. But, at times, I get a great amount of noise ( disturbance ) on lower Bands , distant and far away transmissions. But it’s not constant and I traced the source to our upright Freezer and Fridge. These units have their own inverters working when the compressor kicks in. Toby, my Canadian friend, therefore suggested implementation of ‘Choke’ in Antenna input. I’m like, I ordered a 9:1 unun and now a Choke? When’re am I gonna install all this? Then I saw your KZbin, that gave me a lot of info. My questions; therefore, are:- 1) Is your Choke suitable for my receivers? 2) Should go for type 52 toroid ferrite Core? ( One is available in France ) 3) What is the Toroid Ferrite Core OD 50mm? 4) What is the Coaxial Cable OD? I see your Coaxial cable to be thinner. 5) Thanks. I’d be gratefully, thankful to your advice, as always. Please stay safe. 73s

[@ianxfs]

Sree Kumar Hi Sree, here’s my thoughts... 1. Yes 2. Types 31 & 42 are good for HF. I’m not sure about a 52? You might have to research that mix on the internet. I think it works better at the higher HF frequencies? 3. 2.4 inches/61mm 4. Coax is RG58 approx 5mm Good luck!

[@sreekumarUSA]

ianxfs

[@christopherdcorran]

Where do you get such a big ferrite toroid? JayCar only have small ones.

[@ianxfs]

Christopher D Corran Mouser Christopher.

[@rangerbud]

I don't know that you are supposed to wrap RG-58 that tightly; you may get migration of the center conductor within the insulating foam.....it's non-repetitive turning radius is .98 inch (24.89mm).

[@ianxfs]

Hi Michael. Yes you could make the turns more loose I guess. So far, no problems nearly two years on with two of these running 200w 👍🏻

[@user-sw7oh9oy6f]

Hi - will my RG8 coax be too different to the RG58 that is used for the tests - or will I have to find a length of RG58 to create the Choke - cheers

[@ianxfs]

chilli sauce RG8 is 50 Ohms, but a larger diameter than RG58 I think? You may find it too wide to go round the toroid without risking crushing the interior?

[@user-sw7oh9oy6f]

@@ianxfs Hi- the RG8 is 6mm diameter - RG58 is 5mm !!! Ill have to stretch the hole wider then !!!! RF - drug of choice

[@ianxfs]

Ah right. Should be ok then 👍🏻

[@paulsengupta971]

I guess this is RG8X or Mini-8. I have some of this. :-)

[@ianxfs]

@@paulsengupta971 It's RG58 Paul.

[@jmitsch44827]

You had the RG58 wire cut and did not tell us the length of the cable needed for all the turns of the transformer common mode choke .

[@ianxfs]

Hi, I put it in the video description. 1m 👍🏻

[@paulhotson5820]

What frequencies will this cover?

[@ianxfs]

Hi Paul. If you pause the video at the point where I show the frequency charts, you can see the choking performance across the HF bands. This type 31 ferrite is better for the lower-mid bands whereas a type 43 is better mid-high.

[@AngelMartinez-qn9od]

in which link did you get the box

[@ianxfs]

Hi Angel, it was just from eBay. It is a 100x100x50mm weather-proof box. You’ll see some when you search. Hope this helps.

[@thomastammaro693]

Nice!!

[@ianxfs]

Thanks!

[@thomastammaro693]

I just recently got my General class license here in the USA. The electrical theory and mathematics was the most challenging if not interesting part of the study. Fascinating to watch some one build a choke and for me to be able to grasp the concepts behind it.👊 Do you have any videos on multi band HF antennas ?

[@ianxfs]

@@thomastammaro693 Hi Thomas. Congratulations on your licence! Multibands, depending upon you house/garden, I would say off-centre fed dipole, vertical and/or doublet? Have fun! 😁

[@thomastammaro693]

@@ianxfs , Thank you sir. I have actually got an inverted V cut to be resonant for 10-80 meters. The trick for me is going to be getting it up over all the tree and tying it off . Hence my question regarding the Diamond vertical ( it's referred to as a garden antenna, I just can't remember the exact model number).I still have much to learn. But I'm trading ( in theory at least) for price and simplicity in being able to get up and running

[@andrelemelin4666]

How much power this RF Choke will stand ?

[@ianxfs]

Hi Andre, I think one large core will cope with UK 400w limits. Beyond that I’d stack two cores and review Steve’s winding chart 👍🏻

[@andrelemelin4666]

@@ianxfs Yes thats exactly what I was thinking. I will test one with cores stacked for 2Kw. Will see ..lol

[@Lindomar850]

Muito bom mesmo! 73 pu5rsl !

[@ianxfs]

Obrigado!

[@revadan]

what particular RG58 are you using?

[@ianxfs]

It’s RG58 C/U, but I don’t think it really matters, so long as it’s the general RG58 family spec. Hope this helps. Ian.

[@revadan]

@@ianxfs thanks finished mine. now attached to my hustler 6BTV vertical.

[@ianxfs]

revadan Brilliant!

[@revadan]

How much power can it handle?

[@ianxfs]

revadan I don’t know what the max is for sure. It will manage 400w which is the UK maximum, but looking around at other websites I think it will go to 1Kw. You could also stack 2 of the ferrite cores on top of each other and wrap coax round them both together for an even higher power, which increases the choking effect too. As long as you don’t exceed the coax limits 👍🏻 Note: I did drill a small vent hole at the bottom to let it breath. Hope this helps! 73 Ian.

[@wntu4]

OMG I didn't know Steve passed. :(

[@ianxfs]

David I didn’t know him myself David, but some great work done for the rest of us to follow...

[@matthewmaxcy1574]

What is it? And for

[@ianxfs]

HF RF Choke. Stops transmitted RF coming back down the coax shield/braid into the shack and causing interference to other devices as it radiates.

[@closeoutsaleusa5322]

That's a 1:1 Balun... not an RF Choke.

[@ianxfs]

Hi, it’s unbalanced in and unbalanced out (as it’s one run of coax) and designed to attenuate unwanted frequencies using the properties of the ferrite and is therefore a choke. There is are further videos in relation to an off-centre fed dipole on the channel which show the build of a 50 Ohm balun which also benefits as a choke (& the build of a 4:1 transformer). The balun is designed to achieve compatibility between different systems (& can choke too). Hope this helps 😀