006 DIY RF Current Meter to Discover Bad Common Mode Currents

[@thefekete]

There is a strange swiss distortion, but the SNR is still acceptable for clear reception 😉

[@HB9BLA]

Glad to read that ;-)

[@SkipFlem]

what do you want? CW?

[@PhG1961]

Cool video, the effect of the several ferrite coils on the thick antenna cable is amazing.

[@HB9BLA]

Indeed, they work pretty good. I have to mount them at a particular distance from the feed point. But this is work for spring because I have to de-solder the coax connectors and mount the ferrites outside the home.

[@harryhino2267]

Love the new introduction. Now my weekend is spoken for 😀 There was no "bye" at the end 🥺

[@HB9BLA]

Thank you for the feedback about the intro. HAMs do not say bye, they say 73 ;-)

[@rfburns3472]

Excellent video. Just built one of these devices. I have many relative field strength meters but this one is great for running a coaxial feedline through it. Very useful for A/B testing my feedline isolator chokes to reduce RF in the shack. I first pick a frequency and power output. Adjust the meter for 75% deflection, then add the inline choke. I then use the same exact frequency and power output to see what relative reduction of the meter reading might be.

[@HB9BLA]

Exactly as intended!

[@rfburns3472]

@@HB9BLA Here is my new 2 Port current meter that I just put up a video about. kzbin.info/www/bejne/qILVqnppYtugaKs

[@visitslovenija]

Brilliant. So simple and yet so very useful. Thanks a lot for this video.

[@HB9BLA]

You're welcome!

[@w2aew]

Nice build!

[@HB9BLA]

Thank you!

[@DataJanitor]

This design is simple and easily understood. Thank you!

[@HB9BLA]

My pleasure!

[@Linas_LY2H]

Vielen Dank Andreas! Thanks for sharing my project! I like your incarnation of the probe even more than my own! I’m very glad you have started a purely Ham Radio channell, subscribed! 73! Linas LY2H

[@HB9BLA]

Hi Linas, you are welcome! I am a long-time subscriber to your channel and watch every video. I particularly admire your Morse skills. I am still on my way back (I was a radio operator for the Red Cross when I was young but did not use Morse during the last 40 years). 73 de Andreas, HB9BLA

[@acestudioscouk-Ace-G0ACE]

This is going to be very useful, thank-you!

[@DonDegidio]

Hi Andreas, Nice simple RF meter. Great visuals when you tested the cables. Stay safe. 73 WJ3U

[@HB9BLA]

Thank you. KZbin is very visual. That is why I like it :-)

[@TestSpaceMonkey]

This looks like a handy tool to have in the kit. I think there have been questions at my club about issues with common mode induced by adjacent stations during mini field days. The solution is to just preemptively put ferrites on feed lines next to the radio but this would be a good way to tell for sure.

[@HB9BLA]

Often people mount the ferrites close to the feed of the antenna because it seems that the feed point is the source of the common mode currents, not the transmitter. But I am no specialist. Maybe somebody else knows more.

[@TestSpaceMonkey]

@@HB9BLA Could this be tested by hooking up an swr meter to the shield? Seems like that might even be a good test for the effectiveness of added ferrites.

[@AndreasSpiess]

I do not know how you would connect your SWR Meter for such a setup. I think these are two different things.

[@threebadmicefpv]

These are really cool for tuning up an HF dipole '73

[@HB9BLA]

Indeed, the dipole is balanced and, without balun, it creates common mode currents.

[@2e0txe]

Excellent, Id been asking Linus to make that video for some time so I could build one. Good to see you've also taken it on as a project :D

[@HB9BLA]

I was waiting for his video, too ;-)

[@lloydmerrill]

Andreas, first view of your new channel. Great job. I go for many more. 73 Lloyd W1LBM

[@HB9BLA]

Welcome aboard!

[@MartinPDanz]

Well done like always!

[@HB9BLA]

Oh! An unlicensed viewer ;-). Thank you!

[@MartinPDanz]

@@HB9BLA I got the hint 😉

[@gaborungvari784]

thanks Andreas, and 73!

[@HB9BLA]

You are welcome! 73

[@adriancressy8363]

Thank you much....This will be a great tool in my shack..

[@HB9BLA]

Glad you like it!

[@tommihommi1]

Ferrites: A lot helps a lot :D

[@HB9BLA]

Exactly!

[@FesZElectronics]

Quite a nice device! Over what frequency range does it work? I'm thinking if it makes sense to make 2-3 version for different ranges? Like a >1GHz and a

[@HB9BLA]

I did not check because I only have frequencies below 500 MHz in my shack. The 2.4 GHz Transmitter for the satellite is on the roof. I assume the selectivity will go down with frequency. But because we are often interested in relative values this is probably ok. I wonder how such a device for above 1GHz would look like…

[@Alan2E0KVRKing]

Nice useful project, may have to make one!

[@HB9BLA]

Go for it!

[@rollitomp2241]

Great Video. I will build my own one! Thank you 73!

[@HB9BLA]

Have fun with the build! 73

[@JoshuaJayG]

Great! I have a uA meter that I didn't know what I would do with. Maybe a good project for getting RF out of my shack.

[@HB9BLA]

At least you know where it is. Then you probably will need some ferrites...

[@johnwest7993]

A very handy addition to the shack. Thank you. I already have a surplus meter movement in a metal box, so I think for convenience I'll put the split ferrite, diode, and cap together and then run about a meter and a half of RG174 to the pot and meter movement in the box. It's less work for me to construct and I never know when the point I want to measure won't be convenient for me to work from. Are you aware of any concerns I should address with my version of my build? I'll probably also slide a couple of small ferrite sleeves over the RG174 at each end of the coax just in case. Being a tech and not an engineer I tend to over-build instead of over-engineer.

[@HB9BLA]

It will work as long as you stick with the principle of having a transformer and a display.

[@Sochibusi]

Built it and had this issue: the pointer was going below zero applying rf for half scale of the pot. Solved using a Silicon diode in parallel with the instrument. Maybe the rf was "jumping" to the Germanium diode and was getting detected "backwards"? Anyway now it works fine and is a very useful instrument. 73 de IZ1HNY

[@HB9BLA]

Glad you were able to solve the issue!

[@WimDH]

I like your new intro Andreas! :-)

[@HB9BLA]

Thank you for the feedback! I wanted to have it a little different to the one on the main channel.

[@PhilipKubat]

Good stuff thanks! Both your channels are aweome. At 4:21 you mention "fake" germanium doides, how can one tell? Is there a video on it? Thankls

[@HB9BLA]

I have no video. Just look at the picture of a trusted source and you see that it has to contain a visible wire inside the glas.

[@jamesmichener7526]

I built a simple Arduino Project using an Analog Devices AD8307 log amp, and a 2x20 LCD display to make a wide range RF voltmeter. Once calibrated, it actually accurate to about a couple of dB over a > 70dB range. I have a clamp on core with a BNC, that I use with the volt meter... and it is a good RF voltmeter. AD will send you samples for gratis.

[@HB9BLA]

That is also a good solution. Maybe a bit of an overkill because the calibrated values often are not needed in this application. But since you have it anyway ;-) I have a device from China with an AD8318 and a Display. With a switchable attenuators and a few higher power attenuators these are good solutions for power measurements.

[@daveys]

Sorry to hear about your CW speed dropping due to the ferrites. ;-)

[@HB9BLA]

Like that, I have a good excuse if I make mistakes ;-)

[@maximus6884]

You and wireless is awesome

[@HB9BLA]

Thank you!

[@stylerxxl1]

Tolles Video! Ich bin am überlegen, ob ich damit verschiedene Arten von Transformatoren (1:49) pp. in der Form vergleichen kann, dass ich immer im Strombauch auf dem Antennendraht den Strom messe. So könnte man über die Differenz Rückschlüsse auf die Effektivität des Transformators ziehen. Meinst Du es würde damit klappen? 73s de DL9HD

[@HB9BLA]

Damit kannst du nur Mantelwellen messen. Der Hauptteil der Energie bleibt ja innerhalb des Kabels. Bei den Transformatoren interessieren aber hauptsächlich die Transfer-Parameter, die du z.B. mit einem VNA messen kannst.

[@thereare4lights137]

How do you like your end fed antenna? I just recently purchased one and am installing it this spring. Curious to hear about your experience with it. 😊 VE3POZ 73

[@HB9BLA]

It works fine and was easy to mount because of the end-feed. Like that I only have a small wire from my roof to a tree and the coax is close to the house.

[@aerofart]

Does this apply to RECEIVE-ONLY applications? Due to the laws of symmetry, I imagine so, but how would one measure it? Would selective filtering be needed for the band under test?

[@HB9BLA]

The fact is for both directions. However, in receive you pick environmental noise where you produce it during transmit. A filtering is not needed because, for the test, you transmit only on one frequency.

[@aerofart]

@@HB9BLA thanks for the information. I am only concerned with receive and was wondering if this meter would work for receive, but I’m guessing NO because signal levels are extremely low on receive vs transmit. Keep up the great work. Love your channel!

[@HB9BLA]

Thank you! And you are right with the power levels.

[@OG_Zlog]

According to Digikey the BAT85 is a Schottky diode.

[@HB9BLA]

I thought I mentioned the fact in the video (kzbin.info/www/bejne/h2W9dZeGd92NqdEsi=Glee1v2i52oPZmET&t=233)

[@LawpickingLocksmith]

My mate had just build one of these a month ago!

[@HB9BLA]

It is a very simple but valuable tool.

[@GerardWassink]

Thanks! Any ideas of how to test this without having to use the transformer? I.e. using a frequency generator instead, and at what voltage level?

[@HB9BLA]

The transformer is the receiver. The transmitter is the frequency generator.

[@David_11111]

yay please tell use more about the reamer it looks to fit my screwdriver ??? ah found the link in the description .. on order now :)

[@HB9BLA]

Good decision. A really useful tool

[@dxdoctr1]

I have some issues with common mode currents, especially on 20 meters. Do you know of diagnostic videos that show how to use the current meter?

[@HB9BLA]

No, unfortunately not.

[@rfburns3472]

​@@HB9BLA I did a video on how to do that. kzbin.info/www/bejne/qILVqnppYtugaKs

[@reinholdu9909]

OLDSCHOOL ... in pink 👍 ...4 YL 'cause THAT DAY 's comming *88* *!Weiter so!*

[@HB9BLA]

:-)

[@stevenm45]

I'm very disappointed that you didn't put the nuts, with washers of course, on the back of the meter as it's setting a very bad example to us! ;) I'm 'only pulling your leg' (joking) of course!

[@HB9BLA]

Indeed, itis not best practice. But I had no fitting tool for the purpose. But I ordered one and hope to correct the mistake ;-)

[@chuxxsss]

Morning Andreas, looks good.

[@HB9BLA]

Thanks!

[@nigeljohnson9820]

Have you looked at the frequency response of the circuit? I assume dominated by the charistic of the ferrite.

[@HB9BLA]

I did not look at it. The transformer for sure is heavily influenced by the ferrite material. The 31 material is used for chokes up to 500 MHz and more. The test I showed with the Baofeng was on 2m. If I remember right, I also had a signal on 70cm.

[@nigeljohnson9820]

@@HB9BLA it might be worth doing a frequency sweep, as the measurements at the moment are relative for different radio frequencies. I presume the secondary turns represent an inductance that also acts as a low pass filter to some degree, so there must be a trade off in the number of turns for a given load impedance. Are you happy with the Network analysis shown in the video. I ask because I am considering purchasing one, and this one looks a little more rugged than some that are available. I certainly cannot justify buying a mains powered bench version with a greater dynamic range.

[@HB9BLA]

The one I have is the best you can buy for the moment (if I believe other KZbinrs). I added a link to the description. It has a metal case which I like. I did not test its dynamic range. But it seems to be good enough for all our measurements (excluding relay filters). I use this if I have SMA connectors and a second one with N connectors for the rest. The 4-inch display is good. I would not go smaller.

[@nigeljohnson9820]

@@HB9BLA thank you, that was really helpful. This is going to be a very useful channel.

[@peacekeeper7968]

I love u!

[@JayN4GO]

I find with my meter that most of the common mode is running across my ground strap to outside to the earth rod. Is that normal?

[@HB9BLA]

Usually you want to block common mode at the antenna feed point

[@rfburns3472]

@@HB9BLA Besides putting one at the antenna feed point, you may need a additonal choke at the transmitter output.

[@dave_dennis]

Why is it important that the detector diode be a Schottkey diode?

[@HB9BLA]

Schottky diodes a lot faster than normal p-n diodes. And the lower forward voltage can increase sensitivity.

[@dave_dennis]

Thanks so much Andreas.

[@nutsnproud6932]

Thanks Andreas. Do you know a good reliable source of diodes (and other semiconductors) in Europe? Too many Chinese fakes. 73 de France.

[@HB9BLA]

I order parts from Mouser, Digikey, and Reichelt if I need a European source.

[@mickgibson370]

I used to use double shielding on the cable. Even though, I would cut the cable to the frequency that I used.

[@HB9BLA]

Usually, double shielding does not help in the case of a balanced antenna because the current flows on the outside of the outer shield :-)