Paul, I am just starting to be aware of SDR etc and wonder if you would share what equipment you used on this great video? All i have is a 30 old transceiver and would love to update, THANKS. Ray D.
Seeing is believing! Reducing noise while demostrating the results on SDR is amazing. Thank you for this quality video. It’d be great if u can show the effect of inserting a bifilar on the 60hz harmonics as well
The short whip antenna attenuates the signal being further from the resonant frequency at VLF and the choke attenuates the long feed line which is nearer the resonant frequency. Well the result seems to improve clarity of the signal.
Paul, what is the Inductance value that you measured? I mostly use Type 31 material below 2 mHz to construct chokes. Had no succes with galvanic isolators on vlf. They compromised the signal levels below the MW band.
I've been reading about chokes everyday for about a month now and Ive found so much conflicting results and mathematical calculations. I've a 1/4 wave inverted tee dipole for NOAA apt satellite imagery but without a way to measure the antenna swr ect how can I find with ferrite core to use and the turnes to wrap? I'm only getting into Rf and there's much to learn I'm blown away. It seems to be a science! Do you recommend getting an antenna tester? If so doesanything cheap one to mind? I know cheap isn't always best but at least it would give me a ballpark figure to start by???..... Thankful the video 👍
What SDR software is that? I'd like to get into this listening stuff. Thinking about just improvising and using T.V antenna to receive! 😂 (can always upgrade along the way) Cheers!
Hello Paul,congratulations for your videos, very interesting. I am a SWL and I am writing to you from Italy, I would like to make the CMC you describe in this video, the ferrites you use have an abbreviation, and how many turns of cable you have to do inside. I would like to use it with an amplified miniwhip antenna and an RSP1A from SDRpaly. You would be kind enough to give me the directions. Thanks and best 73.
Interesting video, thanks ! I have one question. As far as I understand, e-probes need a good grounding. How would I place chokes and grounding point along a coax ?
Ground the coax at the base of the non-metallic mast. Then connect the CMC on the rx side of the coax. You may want to place another CMC before the coax enters your house & maybe at the rx. Everyone's situation is different so you may want to experiment.
Why a common mode choke for VLF reception? For reception (but not for transmission) it's gong to be much easier to implement an unun isolation transformer. It won't really matter if the signal gets reduced since the noise levels received on any antenna no matter how isolated are large.
Hello .. It certainly cant hurt to use a well designed CMC. They are most useful in MF LF VLF bands because thats where the the strongest noise sources are.
Your diagram left out an important circuit element in the system, the ground at the SDR end, however sloppy. I would suggest for VLF work a large number if bifilar turns on a large low loss toroid core. This will effectively break the ground loop for 60 Hz and its harmonics. The combination of CMC and transformer should provide some significant help at lower frequencies. If you design the transformer for 3 kHz as a 3 dB down point you might clear out that stuff at the low end of your monitoring spectrum. The formal citation of Joanne's Ground Law is simple, "Ground isn't." This is mnemonic for the detail that ground is always a circuit element. Even if you use single point ground you have the lead inductance and even its antenna-like characteristics plaguing your best efforts. Break the ground loop, a nice large magnetic loop. Your CMCs do this nicely at the upper end of the video's frequency range. But, you dismissed the lower end as "can't do anything about." You surely can. That's what the transformer does. I'd experiment with both bifilar turns and isolated turns on opposite sides of a large toroid core to find the optimum solution. At the couple hundred turn level I suspect bifilar would serve a little better at the high end of the frequency range. {^_^}
Hi Paul. I'm just starting this years 630m band activities. Before I install it I will make sure to include a couple of common mode chokes. I've also seen people provide an earth connection at the base of mast used for the e-field probe. I guess this has not made any improvement over your 2 x CMC installation. 73 and tnks for the video. David G0MRF
@@davidbowman1828 Hello David.. I am am making a how to video even as we speak.. Hope to be done by tonight. If you would be so kind as to subscribe I would be honored
@@davidbowman1828 Sorry I missed this part of your question.. Yes I provide an earth ground at the base of the antenna, active or loop. I have not experimented enough to see if the ground is more effective at the antenna itself, or on the CMC feeding it. Work to be done there.
What you have is a single coil, not a common mode choke. Stop using wrong words for what you are doing. Google common mode choke design and se what you got wrong.
That is incorrect... what is needed to choke off common mode signals is a high inductive reactance at the frequency of operation, in this case VLF frequencies and above. A few turns of coax such as used in HF operations would be woefully ineffective at VLF. Hence the cores designed for those frequencies and the multiple turns.
+1 Group W Bench reference! That made me smile. Thank you!
It was very easy to see the "noise floor" drop when you added the chokes.
Paul, I am just starting to be aware of SDR etc and wonder if you would share what equipment you used on this great video? All i have is a 30 old transceiver and would love to update, THANKS. Ray D.
Hi Paul. I really enjoyed your video.
from Australia
VBQ543 / 43HS2456
Seeing is believing! Reducing noise while demostrating the results on SDR is amazing. Thank you for this quality video. It’d be great if u can show the effect of inserting a bifilar on the 60hz harmonics as well
Nice! Informative as well!
Very interesting, best regards from France
73’s From F4JWQ
Thank you very much I appreciate you watching! W1VLF
The short whip antenna attenuates the signal being further from the resonant frequency at VLF and the choke attenuates the long feed line which is nearer the resonant frequency. Well the result seems to improve clarity of the signal.
What a great demo for using CMC ! TNX for the video !
73 N8AUM
Hi Vidas, Thank you for the comment. Its good to know the video was helpful. W1VLF
Cool! Never seen Console before. Downloading. Thanks!
nice: i regularly check vlf and lf and my problems is the noise. I will build a choke and check what happend. Tks for exelent video. XE2EJ
Cutler Maine an interesting place. I have been there a few times.
Brilliant! just Brilliant
Hi Paul. Could you post a schematic (or link) to your e-field antenna? Thanks
Paul, what is the Inductance value that you measured? I mostly use Type 31 material below 2 mHz to construct chokes. Had no succes with galvanic isolators on vlf. They compromised the signal levels below the MW band.
I don't understand a word your saying but I like to listen to you
I've been reading about chokes everyday for about a month now and Ive found so much conflicting results and mathematical calculations.
I've a 1/4 wave inverted tee dipole for NOAA apt satellite imagery but without a way to measure the antenna swr ect how can I find with ferrite core to use and the turnes to wrap?
I'm only getting into Rf and there's much to learn I'm blown away. It seems to be a science! Do you recommend getting an antenna tester? If so doesanything cheap one to mind? I know cheap isn't always best but at least it would give me a ballpark figure to start by???.....
Thankful the video 👍
NanoVNA
What SDR software is that?
I'd like to get into this listening stuff.
Thinking about just improvising and using T.V antenna to receive! 😂
(can always upgrade along the way)
Cheers!
What modulation scheme were you listening with?
I love your Callsign mate ⚡🙏⚡
Hello Paul,congratulations for your videos, very interesting. I am a SWL and I am writing to you from Italy, I would like to make the CMC you describe in this video, the ferrites you use have an abbreviation, and how many turns of cable you have to do inside. I would like to use it with an amplified miniwhip antenna and an RSP1A from SDRpaly. You would be kind enough to give me the directions. Thanks and best 73.
Do you think this could work for frequencies above the VLF range?
Yes it would I would use the correct core type for the region of interest. My problems were mostly at LF and VLF hence the use of that particular core
Great filter, thanks! But what good is VLF? I haven't found out yet, but I enjoy experimenting.
Interesting video, thanks !
I have one question. As far as I understand, e-probes need a good grounding. How would I place chokes and grounding point along a coax ?
Ground the coax at the base of the non-metallic mast. Then connect the CMC on the rx side of the coax. You may want to place another CMC before the coax enters your house & maybe at the rx. Everyone's situation is different so you may want to experiment.
Why a common mode choke for VLF reception? For reception (but not for transmission) it's gong to be much easier to implement an unun isolation transformer. It won't really matter if the signal gets reduced since the noise levels received on any antenna no matter how isolated are large.
Hi,
Do you also recommend the common mode choke noise reduction for SWL/HF? Or only VLF?
Thank you
Hello .. It certainly cant hurt to use a well designed CMC. They are most useful in MF LF VLF bands because thats where the the strongest noise sources are.
@@W1VLF Many thanks for the clear reply, much appreciated.
Hi Great video. Have you tried on 160 or 90m HF bands?
Muito boa mesmo sua explanação, colega, 73 pu5rsl
muito obrigado por comentar. W1VLF
Is there a way I can tell if my coax is picking up interference?
Was that "slide" from an actual measurement you did ?
Which "slide" are you referring to?
I am baffled that a 3ft whip is picking up such low freqs
"Group W bench". 😂
Yea.. A lot of people don' t get that!! LOL
@@W1VLF You should refer to the tools and equipment in your shack as, "shovels and rakes and other impliments of destruction".
@@Swervin309 *" x 10 color glossy photographs
@@W1VLF With circles and arrows and description on the back of each one.
Your diagram left out an important circuit element in the system, the ground at the SDR end, however sloppy. I would suggest for VLF work a large number if bifilar turns on a large low loss toroid core. This will effectively break the ground loop for 60 Hz and its harmonics. The combination of CMC and transformer should provide some significant help at lower frequencies. If you design the transformer for 3 kHz as a 3 dB down point you might clear out that stuff at the low end of your monitoring spectrum.
The formal citation of Joanne's Ground Law is simple, "Ground isn't." This is mnemonic for the detail that ground is always a circuit element. Even if you use single point ground you have the lead inductance and even its antenna-like characteristics plaguing your best efforts. Break the ground loop, a nice large magnetic loop. Your CMCs do this nicely at the upper end of the video's frequency range. But, you dismissed the lower end as "can't do anything about." You surely can. That's what the transformer does. I'd experiment with both bifilar turns and isolated turns on opposite sides of a large toroid core to find the optimum solution. At the couple hundred turn level I suspect bifilar would serve a little better at the high end of the frequency range.
{^_^}
Hello .. Can you possible send me a direct email?
Hi Paul. I'm just starting this years 630m band activities. Before I install it I will make sure to include a couple of common mode chokes. I've also seen people provide an earth connection at the base of mast used for the e-field probe. I guess this has not made any improvement over your 2 x CMC installation. 73 and tnks for the video. David G0MRF
@@davidbowman1828 Hello David.. I am am making a how to video even as we speak.. Hope to be done by tonight. If you would be so kind as to subscribe I would be honored
@@davidbowman1828 Sorry I missed this part of your question.. Yes I provide an earth ground at the base of the antenna, active or loop. I have not experimented enough to see if the ground is more effective at the antenna itself, or on the CMC feeding it. Work to be done there.
What you have is a single coil, not a common mode choke. Stop using wrong words for what you are doing. Google common mode choke design and se what you got wrong.
Seems to me a more expensive and time consuming project in comparison to a coax air coil called by some an "ugly balun".
That is incorrect... what is needed to choke off common mode signals is a high inductive reactance at the frequency of operation, in this case VLF frequencies and above. A few turns of coax such as used in HF operations would be woefully ineffective at VLF. Hence the cores designed for those frequencies and the multiple turns.