Re: Topband: 160 GP Choke
And --as I remembered a few milliseconds after I replied-- only ONE core. :-) 73, Mike www.w0btu.com On Mon, Oct 6, 2014 at 3:29 AM, Jim Brown wrote: > On Fri,10/3/2014 12:58 AM, Mike Waters wrote: > >> That is the design that I was originally going to use, except that I would >> change it slightly because I use all 75 ohm coax. Anyway, what is the >> advantage over one made with coax? Better bandwidth, I suppose? >> > > Yes, the advantages of THHN are better bandwidth, and a closer Zo match to > a high dipole > _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 160 GP Choke
On Fri,10/3/2014 12:58 AM, Mike Waters wrote: That is the design that I was originally going to use, except that I would change it slightly because I use all 75 ohm coax. Anyway, what is the advantage over one made with coax? Better bandwidth, I suppose? Yes, the advantages of THHN are better bandwidth, and a closer Zo match to a high dipole. Jerry Sevick wrote about Zo of parallel wire line chokes, and had established the Zo values I noted. Many years later, I wound some chokes and confirmed these values within the range of experimental error. 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 160 GP Choke
That is the design that I was originally going to use, except that I would change it slightly because I use all 75 ohm coax. Anyway, what is the advantage over one made with coax? Better bandwidth, I suppose? I have your PDF printed and bound. I suppose that I should study it again. 73, Mike www.w0btu.com On Tue, Sep 30, 2014 at 11:44 AM, Jim Brown wrote: > ... Measure out two 5 feet lengths of enameled wire. Tape them together > (a single wrap of tape every 5 inches or so) and wind that pair of wires 16 > turns around a single core. Connect it at each end as a two-wire > transmission line. > > 73, Jim K9YC > > On Tue,9/30/2014 3:42 AM, Mark van Wijk wrote: > >> >> Using 2x4 pcs FT240-31 it might look something like this: >> https://www.flickr.com/photos/pa5mw/7870640836/in/set-72157640001358005 >> > _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 160 GP Choke
No. I wrote badly. Measure out two 5 feet lengths of enameled wire. Tape them together (a single wrap of tape every 5 inches or so) and wind that pair of wires 16 turns around a single core. Connect it at each end as a two-wire transmission line. 73, Jim K9YC On Tue,9/30/2014 3:42 AM, Mark van Wijk wrote: Using 2x4 pcs FT240-31 it might look something like this: https://www.flickr.com/photos/pa5mw/7870640836/in/set-72157640001358005 _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 160 GP Choke
On Mon,9/29/2014 7:00 PM, Mike Waters wrote: >From p. 33: "With RG-6, RG-8X, and RG-59, use 7 turns through five 2.4" o.d. #31 toroidal cores." Looks like it could stand one more core and one more turn, if I only used it on 160 and 80. You must have an old version of it -- the latest is summer 2010, and that sentence is on page 35. Yes, one more core and one more turn. In private email, I recommended one of the bifilar chokes wound on a single core with enameled wire. See measured data on page 34, and recommendations in the "Cookbook." As Tom has noted, with resonant radials, there's not much common mode, so power handling is not a big deal. I suggested 16 turns (x2) of enameled #12 connected as parallel wire line. I'm using #12 THHN on my 120 ft high 80/40 dipoles. The soil here is very poor, so my VNA measurements translated up the line to the antenna yield Z of about 85 ohms at resonance, and that's the approximate Zo of the THHN chokes. The enameled are close to 50 ohms. 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 160 GP Choke
W0BTU was kind enough to include a link to his inverted-L EZNEC model so I added that to a thread over on eHam which discusses using a "dual-band autopilot" matching network, in this case using the inverted-L on 160 and 80 with no tweaking or switching of the matching network needed: http://www.eham.net/ehamforum/smf/index.php/topic,99152.0.html Nothing to do with chokes, just thought it might be of interest. Dan, AC6LA _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 160 GP Choke
>From p. 33: "With RG-6, RG-8X, and RG-59, use 7 turns through five 2.4" o.d. #31 toroidal cores." Looks like it could stand one more core and one more turn, if I only used it on 160 and 80. 73, Mike www.w0btu.com On Mon, Sep 29, 2014 at 5:44 PM, Jim Brown wrote: > On Mon,9/29/2014 2:31 PM, Mike Waters wrote: > >> It's 6 turns of F-6 coax through four 2.4" OD Fair-rite #31 cores ($7 each >> from Mouser), per K9YC's PDF. >> > > My pdf calls for a lot more turns than that for 160M, but it ain't broke, > don't fix it. :) > > 73, Jim > _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 160 GP Choke
On Mon,9/29/2014 2:31 PM, Mike Waters wrote: It's 6 turns of F-6 coax through four 2.4" OD Fair-rite #31 cores ($7 each from Mouser), per K9YC's PDF. My pdf calls for a lot more turns than that for 160M, but it ain't broke, don't fix it. :) 73, Jim _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 160 GP Choke
Bill, Photos of the common-mode choke at the base of mine ( http://www.w0btu.com/160_meters.html#inv-l_antenna) are at http://www.w0btu.com/files/antenna/160m_inv-L It's 6 turns of F-6 coax through four 2.4" OD Fair-rite #31 cores ($7 each from Mouser), per K9YC's PDF. 73, Mike www.w0btu.com _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 160 GP Choke
If it were my system, I would use an air core choke like you posted and ground the feedline where it reaches earth. The nice thing is you can install the choke right at ground level with no ill effects at all. Cheap, simple, and clean. It will work as well as anything else you can do and be very reliable. 73 Tom - Original Message - From: "Cqtestk4xs--- via Topband" To: Sent: Monday, September 29, 2014 12:49 PM Subject: Topband: 160 GP Choke Thanks to all who responded. One of the suggestions was to wrap about 40-45 turns of RG8X mini on a PVC core with a diameter of 4 incheslightweight and easy. Part two was to ground the braid of the feeder line coax at the point where it reaches ground level. What do you think? Bill K4XS _ Topband Reflector Archives - http://www.contesting.com/_topband - No virus found in this message. Checked by AVG - www.avg.com Version: 2014.0.4765 / Virus Database: 4025/8293 - Release Date: 09/29/14 _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 160 GP Choke
On Mon,9/29/2014 10:43 AM, wb6r...@mac.com wrote: Bill - An effective common-mode choke can be made with 17 turns of RG58-coax wound on to an Amidon FT240-31 core. It's not an Amidon core, it's a Fair-Rite core. It's a LOT cheaper when you buy from a Fair-Rite distributor. See Appendix One of k9yc.com/RFI-Ham.pdf 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 160 GP Choke
Bill - An effective common-mode choke can be made with 17 turns of RG58-coax wound on to an Amidon FT240-31 core. See: www.karinya.net/g3txq/chokes/ GL - Steve WB6RSE On Sep 29, 2014, at 9:49 AM, Cqtestk4xs--- via Topband wrote: What do you think? Bill K4XS _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: 160 GP Choke
Thanks to all who responded. One of the suggestions was to wrap about 40-45 turns of RG8X mini on a PVC core with a diameter of 4 incheslightweight and easy. Part two was to ground the braid of the feeder line coax at the point where it reaches ground level. What do you think? Bill K4XS _ Topband Reflector Archives - http://www.contesting.com/_topband
