Subject:"Re\: \[Elecraft\] Common Mode Chokes" - The Mail Archive

Re: [Elecraft] Common Mode chokes to reduce noise

2021-11-28 Thread Jim Brown

On 11/28/2021 11:05 AM, Ed Cole wrote: K, kind of what I was thinking.  So either go on search for noise source or try reducing the noise at the receiver.  K3 NB does not improve SNR on 6m. The K3 NB has lots of tweaks. Depending on the modes you use, it might help in some situations. On HF noise varies: 80m its S7 from an inverted-V; on 20m its S3 from a yagi (both have baluns). Of course -- noise sources vary widely in their spectral content, and how much we hear will depend on what they are using for TX antennas and how those TX antennas are coupled to the noise sources. Likewise, how we hear them will depend on our antennas -- their location, directivity, and whether they are well choked at the feedpoint. 6m noise at S5-S7 is the most troublesome because I do weak-signal operating (eme, ms, FT8). InnovAntenna 6m baluns are many ferrite beads in series.  6m yagis are LFA7 from InnovAntenna (UK). Is that S5-S7 on a well calibrated S-meter? That's HUGE. Shack is grounded via No. 8 wire to ground post adjacent to shack. Aluminum plate coax thru-wall panel is grounded by it, as well. You need to STUDY N0AX's ARRL book on Grounding and Bonding, to which I contributed, and/or this slide deck pdf. http://k9yc.com/GroundingAndAudio.pdf Also these to chase down and kill the noise sources. The first is text, written for National Contest Journal, the second is a slide deck. http://k9yc.com/KillingReceiveNoise.pdf http://k9yc.com/KillingRXNoiseVisalia.pdf 73, Jim K9YC __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]

Re: [Elecraft] Common Mode chokes to reduce noise

2021-11-28 Thread Ed Cole

OK, kind of what I was thinking. So either go on search for noise source or try reducing the noise at the receiver. K3 NB does not improve SNR on 6m. On HF noise varies: 80m its S7 from an inverted-V; on 20m its S3 from a yagi (both have baluns). 6m noise at S5-S7 is the most troublesome because I do weak-signal operating (eme, ms, FT8). InnovAntenna 6m baluns are many ferrite beads in series. 6m yagis are LFA7 from InnovAntenna (UK). Shack is grounded via No. 8 wire to ground post adjacent to shack. Aluminum plate coax thru-wall panel is grounded by it, as well. ED-KL7UW - If it does, something is very wrong in your shack, like bonding. What DOES matter is having effective common mode chokes at the antenna's feedpoint. See my recommendations at k9yc.com/publish.htm 73, Jim K9YC -- I don't see how a common mode choke would help in that situation. If the noise changes that dramatically depending upon where you have the antenna pointed, that strongly suggests that the noise is being received by the antenna and is not riding on the shield of the coax.? If it is received by the antenna it is differential in nature and a common mode choke won't do anything. It sounds like you are being plagued by either a local noise source, or the atmospheric noise is much stronger in one direction.? In my case, the background noise during the middle of the day is always stronger east versus west even though there isn't any significant housing or businesses within 200 miles east of me. 73, Dave?? AB7E __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]

Re: [Elecraft] Common Mode chokes to reduce noise

2021-11-28 Thread Dave

While it is unlikely to make any difference, if you can source these ferrite sleeves in the USA they are excellent value and perhaps worth a try. A pack of 5 cost about $1.50 plus shipping and tax (£1.15 + tax in the UK). Two packs (10 sleeves) should make an effective choke for 6m and will slip over RG213 size coax. My own measurements of them with a VNA look OK with 10 used on 6m and 4m, 5 are suitable for 2m. https://cpc.farnell.com/unbranded/559-568/emi-sleeves-10-7-x-28-5mm/dp/CBBR6937?ost=559-568 73 Dave G4AON -- Sent from my iPhone SE __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]

Re: [Elecraft] Common Mode chokes to reduce noise

2021-11-27 Thread David Gilbert

I don't see how a common mode choke would help in that situation. If the noise changes that dramatically depending upon where you have the antenna pointed, that strongly suggests that the noise is being received by the antenna and is not riding on the shield of the coax.  If it is received by the antenna it is differential in nature and a common mode choke won't do anything. It sounds like you are being plagued by either a local noise source, or the atmospheric noise is much stronger in one direction.  In my case, the background noise during the middle of the day is always stronger east versus west even though there isn't any significant housing or businesses within 200 miles east of me. 73, Dave   AB7E On 11/27/2021 10:21 AM, Ed Cole wrote: I primarily work eme so band noise is a prime enemy of weak signals. I was reading the comments about combating mic noise and wondered if adding some ferrite beads to my 6m coax at the shack would have any effect on received broad-band noise.  I definitely see the noise peak in one direction of the antenna S5/S7 vs S2 at 180-degrees azimuth rotation, and it also drops with about 13 degrees of antenna elevation. My 6m LFA antenna use ferrite bead baluns.  Transmission coax runs 40-foot vertical and 50-foot horizontal on the ground.  Rx comes from a remote preamp connected thru a TR relay with output thru LMR-240 coax to the Rx antenna port of the K3. 73, Ed - KL7UW __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]

Re: [Elecraft] Common Mode chokes to reduce noise

2021-11-27 Thread Jim Brown

On 11/27/2021 9:21 AM, Ed Cole wrote: I was reading the comments about combating mic noise and wondered if adding some ferrite beads to my 6m coax at the shack would have any effect on received broad-band noise. If it does, something is very wrong in your shack, like bonding. What DOES matter is having effective common mode chokes at the antenna's feedpoint. See my recommendations at k9yc.com/publish.htm 73, Jim K9YC __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]

Re: [Elecraft] Common mode chokes - FS RF meter

2016-08-12 Thread w4grj

FS- I have a RF current meter MFJ 854 purchased for a project now available for sale in perfect condition $80 mailed. Please contact me offline. Jack W4GRJ -Original Message- From: Elecraft [mailto:[email protected]] On Behalf Of EricJ Sent: Tuesday, August 09, 2016 5:38 PM To: [email protected] Subject: Re: [Elecraft] Common mode chokes W8JI also describes one and how to calibrate it. http://w8ji.com/building_a_current_meter.htm Eric KE6US On Tue,8/9/2016 1:56 PM, MaverickNH wrote: >> Just wondering - short of +/- RF Burns and Audible Noice, can one >> readily detect/measure Common Mode Current on a coax antenna >> feedline? > __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected] __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]

Re: [Elecraft] Common mode chokes

2016-08-09 Thread Vic Rosenthal 4X6GP

Here is a device I made to do that: 73, Vic, 4X6GP Rehovot, Israel Formerly K2VCO http://www.qsl.net/k2vco/ On 9 Aug 2016 23:56, MaverickNH wrote: Just wondering - short of +/- RF Burns and Audible Noice, can one readily detect/measure Common Mode Current on a coax antenna feedline? __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]

Re: [Elecraft] Common mode chokes

2016-08-09 Thread Ian White

> >Add another winding to a choke and it magically becomes a transformer! > Unfortunately that doesn't work for RF current measurement. The objective for a choke is to create a high series impedance, but the objective for an RF current transformer is exactly the opposite: to avoid disturbing the situation that is being measured, the impedance inserted into the main line must be as low as possible. To achieve a low impedance in the main line, an RF current transformer requires *ONE* pass of the primary winding (feedline) through the core and typically about 10 turns on the secondary. The secondary must also be terminated in a low load resistance, typically about 50 ohms. With a 1:10 turns ratio the series impedance inserted into the main line is then about 0.5 ohms. That is why a common-mode choke and a common-mode current transformer are two completely different creatures. Don't confuse them. 73 from Ian GM3SEK >-Original Message- >From: Elecraft [mailto:[email protected]] On Behalf Of >Josh Fiden >Sent: 09 August 2016 22:16 >To: [email protected] >Subject: Re: [Elecraft] Common mode chokes > >Add another winding to a choke and it magically becomes a transformer! > >73, >Josh W6XU > >On 8/9/2016 1:56 PM, MaverickNH wrote: >> Just wondering - short of +/- RF Burns and Audible Noice, can one readily >> detect/measure Common Mode Current on a coax antenna feedline? >> >> >> >> -- >> View this message in context: >http://elecraft.365791.n2.nabble.com/Common-mode-chokes- >tp7621305p7621430.html >> Sent from the Elecraft mailing list archive at Nabble.com. >> __ >> Elecraft mailing list >> Home: http://mailman.qth.net/mailman/listinfo/elecraft >> Help: http://mailman.qth.net/mmfaq.htm >> Post: mailto:[email protected] >> >> This list hosted by: http://www.qsl.net >> Please help support this email list: http://www.qsl.net/donate.html >> Message delivered to [email protected] >> > >__ >Elecraft mailing list >Home: http://mailman.qth.net/mailman/listinfo/elecraft >Help: http://mailman.qth.net/mmfaq.htm >Post: mailto:[email protected] > >This list hosted by: http://www.qsl.net >Please help support this email list: http://www.qsl.net/donate.html >Message delivered to [email protected] __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]

Re: [Elecraft] Common mode chokes

2016-08-09 Thread EricJ

W8JI also describes one and how to calibrate it. http://w8ji.com/building_a_current_meter.htm Eric KE6US On Tue,8/9/2016 1:56 PM, MaverickNH wrote: Just wondering - short of +/- RF Burns and Audible Noice, can one readily detect/measure Common Mode Current on a coax antenna feedline? __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]

Re: [Elecraft] Common mode chokes

2016-08-09 Thread Don Wilhelm

Bret, Refer to the K9YC (Jim Brown) paper on RFI, Ferrites, Baluns and Audio Interfacing for "good" baluns. http://www.audiosystemsgroup.com/RFI-Ham.pdf. For common mode chokes (baluns), look particularly at Chapter 7 of that document. A stack of 5 FT240-31 cores and a length of coax sufficient to wind 5 to 7 turns through the cores is generally less expensive (and more effective) than the cost of commercial baluns or "in-line isolators". 73, Don W3FPR On 8/9/2016 5:10 PM, MaverickNH wrote: Further (apologies, I should have thunk it through before posting): Based on http://www.karinya.net/g3txq/chokes/ which may or may not be well-accepted, which choke configuration would you choose for "Best"? I'm actually fond of two chokes in series to address the 1.8-30MHz range, but am still pondering which two? At a hefty pre-made price, one can have 160-40m & 40-10m http://palomar-engineers.com/antenna-products/1-1-balun-kits/super-choker, albeit with no transparency of composition. What cost of of Low SNR? Thousands$$$ spent on Transceivers/Antennas and $100s on chokes? __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]

Re: [Elecraft] Common mode chokes

2016-08-09 Thread Josh Fiden

Add another winding to a choke and it magically becomes a transformer! 73, Josh W6XU On 8/9/2016 1:56 PM, MaverickNH wrote: Just wondering - short of +/- RF Burns and Audible Noice, can one readily detect/measure Common Mode Current on a coax antenna feedline? -- View this message in context: http://elecraft.365791.n2.nabble.com/Common-mode-chokes-tp7621305p7621430.html Sent from the Elecraft mailing list archive at Nabble.com. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected] __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]

Re: [Elecraft] Common mode chokes

2016-08-09 Thread Ian White

> >Just wondering - short of +/- RF Burns and Audible Noice, can one readily >detect/measure Common Mode Current on a coax antenna feedline? > Google for: clamp-on rf current meter http://www.ifwtech.co.uk/g3sek/clamp-on/clamp-on.htm This review of two MFJ products (one good, one awful) may also be useful: http://www.ifwtech.co.uk/g3sek/clamp-on/mfj-reviews.pdf 73 from Ian GM3SEK >-Original Message- >From: Elecraft [mailto:[email protected]] On Behalf Of >MaverickNH >Sent: 09 August 2016 21:56 >To: [email protected] >Subject: Re: [Elecraft] Common mode chokes > >Just wondering - short of +/- RF Burns and Audible Noice, can one readily >detect/measure Common Mode Current on a coax antenna feedline? > > > >-- >View this message in context: >http://elecraft.365791.n2.nabble.com/Common-mode-chokes- >tp7621305p7621430.html >Sent from the Elecraft mailing list archive at Nabble.com. >__ >Elecraft mailing list >Home: http://mailman.qth.net/mailman/listinfo/elecraft >Help: http://mailman.qth.net/mmfaq.htm >Post: mailto:[email protected] > >This list hosted by: http://www.qsl.net >Please help support this email list: http://www.qsl.net/donate.html >Message delivered to [email protected] __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]

Re: [Elecraft] Common mode chokes

2016-08-09 Thread Jim Brown

On Tue,8/9/2016 1:56 PM, MaverickNH wrote: Just wondering - short of +/- RF Burns and Audible Noice, can one readily detect/measure Common Mode Current on a coax antenna feedline? Yes. A calibrated RF current probe coupled to the outside of the coax can easily measure common mode current. Here are a couple of easy ways to do it. http://www.ifwtech.co.uk/g3sek/clamp-on/clamp-on.htm Note that because the coax is acting as part of an antenna for common mode current, the current will vary along the line just as it would for any other antenna. For example, the coax a simple wire dipole in an earth-based station acts as a wire connected between the shield side of the dipole and ground, with the length of the wire equal to the physical length of the coax, and oriented in space as the actual coax is routed. 73, Jim K9YC __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]

Re: [Elecraft] Common mode chokes

2016-08-09 Thread MaverickNH

Further (apologies, I should have thunk it through before posting): Based on http://www.karinya.net/g3txq/chokes/ which may or may not be well-accepted, which choke configuration would you choose for "Best"? I'm actually fond of two chokes in series to address the 1.8-30MHz range, but am still pondering which two? At a hefty pre-made price, one can have 160-40m & 40-10m http://palomar-engineers.com/antenna-products/1-1-balun-kits/super-choker, albeit with no transparency of composition. What cost of of Low SNR? Thousands$$$ spent on Transceivers/Antennas and $100s on chokes? BRET/KC1CJN -- View this message in context: http://elecraft.365791.n2.nabble.com/Common-mode-chokes-tp7621305p7621431.html Sent from the Elecraft mailing list archive at Nabble.com. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]

Re: [Elecraft] Common mode chokes

2016-08-09 Thread MaverickNH

Just wondering - short of +/- RF Burns and Audible Noice, can one readily detect/measure Common Mode Current on a coax antenna feedline? -- View this message in context: http://elecraft.365791.n2.nabble.com/Common-mode-chokes-tp7621305p7621430.html Sent from the Elecraft mailing list archive at Nabble.com. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]

Re: [Elecraft] Common mode chokes

2016-08-07 Thread Mel Farrer via Elecraft

Check Jim's tutorial on RFI.  You will need some clip on #31 cable ferrites, I think. Mel, K6KBE From: Cortland Richmond To: [email protected] Sent: Sunday, August 7, 2016 2:54 PM Subject: Re: [Elecraft] Common mode chokes I had a similar problem in 2005 when noise from a 2kW Honda got into my RV on FD.  Lacking any ferrites etc I borrowed a plastic "milk bottle box" and wound about 30 feet of extension cord around it., which worked well as a temporary fix. Cortland ka5s On 8/7/2016 2:21 PM, [email protected] wrote: > I have an inverter generator producing S9 noise on 3.5Mhz, and S7 noise on > 7Mhz. Higher frequencies are clear. > If I were to use a trifilar wound choke on the lead from the generator, what > would be the best mix...43, 77 or? __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected] __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]

Re: [Elecraft] Common mode chokes

2016-08-07 Thread Cortland Richmond

I had a similar problem in 2005 when noise from a 2kW Honda got into my RV on FD. Lacking any ferrites etc I borrowed a plastic "milk bottle box" and wound about 30 feet of extension cord around it., which worked well as a temporary fix. Cortland ka5s On 8/7/2016 2:21 PM, [email protected] wrote: I have an inverter generator producing S9 noise on 3.5Mhz, and S7 noise on 7Mhz. Higher frequencies are clear. If I were to use a trifilar wound choke on the lead from the generator, what would be the best mix...43, 77 or? __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]

Re: [Elecraft] Common mode chokes

2016-08-07 Thread Dave Cole

On Sun, 2016-08-07 at 15:50 +1000, Gary wrote: > Hi, > I have an inverter generator producing S9 noise on 3.5Mhz, and S7 > noise on 7Mhz. Higher frequencies are clear. > If I were to use a trifilar wound choke on the lead from the > generator, what would be the best mix...43, 77 or? > I can source ferrite cores here in VK, whether I can obtain what I > will need is unknown but likely. Failing that, Mouser? > I spent a lot of time searching the web but unsure still. > If the learned group could help out with advice it will be greatly > appreciated. >  Hello Gary, I have had good luck using mix31 material in the FT-240-31 configuration.   See: http://www.fair-rite.com/design-tools/materials/ For an explanation of what each mix does, also see: http://audiosystemsgroup.com/RFI-Ham.pdf and: http://audiosystemsgroup.com/SAC0305Ferrites.pdf and: http://www.karinya.net/g3txq/chokes/ for more information. -- 73's, and thanks, Dave (NK7Z) For software/hardware reviews see: http://www.nk7z.net __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]

Re: [Elecraft] Common mode chokes

2016-08-06 Thread Jim Brown

On Sat,8/6/2016 10:50 PM, Gary wrote: I spent a lot of time searching the web but unsure still. k9yc.com/RFI-Ham.pdf See the Choke Cookbook and follow the guidelines for the bands where you have noise, and for coax the size of the power cable. Place the choke as close as possible to the generator. Also study this slide show for a talk I did several years ago about this to our local contest club. http://nccc.cc/pdf/CQP-RFI2013-2.pdf 73, Jim K9YC __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]

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