Merry Christmas! SAQ Grimeton Christmas Eve Transmission
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Jonathan
Dec 24, 2021, 1:56:50 PM12/24/21
to Unknown, TangerineSDR Listserv, emum...@gmail.com
Merry Christmas All!
SAQ at Grimeton, Sweden transmitted their annual Christmas Eve message
on 17.2 kHz CW using the Alexanderson alternator.
Recently, Nathaniel and I finished installing conduit and cable for a
VLF SDR and the PSWS ground magnetometer. We installed the VLF SDR and
active VLF antenna as well as the ground magnetometer and got both up
and running.
For many years, I wanted to be able to receive the SAQ Christmas Eve
transmission, but here in the US, it can be difficult. The
transmission was scheduled to occur at around 3AM EST or 8 UT. My VLF
SDR was recording the VLF band this snowy morning and captured the
spectrum. Unfortunately, the propagation conditions weren't the best,
but I was able to hear it, but just barely, and I mean just barely!
Here is a link to the mp3 file:
https://drive.google.com/file/d/1DhiKg9azAJzBZkv6rqFCXZQh1VZnhiSy/view?usp=sharing
Only at 14:40 into the recording can you just barely make out the 500
Hz downmixed carrier. I can maybe copy a few characters. If anyone is
interested how I created the file, here is a long pipe using
vlfrx-tools to read data from the data store, bandpass filter at 17.2
kHz center with 1 kHz bandwidth. Comments are added for description:
vtread -T 2021-12-24_07:41:30,+24m /data/vlf_96k | # read from data
store starting at 12/24/2021 7:41:30 UT for a duration of 24 minutes.
vtfilter -h bp,f=17200,w=1000 -g50 | # Insert a bandpass filter
with fc=17200 Hz, 1000 Hz wide with a gain of 50.
vtmult -f 16700 | # downmix carrier to 500 Hz using 16700 Hz local oscillator
vtmix -c 1,-j | # select the upper sideband
vtraw -ow | # convert to wav
lame -b64 -m m - SAQ122421.mp3 # encode pipe output to mp3
All is not entirely lost. The author of vlfrx-tools was able to
capture it at his location in the UK. Here is a link to his recording
where the whole message can be copied. At the very beginning of the
recording, there is a test transmission. Here is the link:
https://drive.google.com/file/d/1ruY291-G4sKk4DKJMUmTkSJaFjcvrkUC/view?usp=sharing
Credit to the author of vlfrx-tools for assistance on extracting the
recording and processing it. Much gratitude to Paul, the author of
vlfrx-tools, for his help, expertise, patience, and guidance
throughout the years and now, as well as his software and
documentation. Much gratitude to Nathaniel as well. For a recorded
live stream at SAQ in Grimeton and more information about the
transmitter, please see the Alexander Association's web site:
https://alexander.n.se/en/
Jonathan
KC3EEY
SAQ at Grimeton, Sweden transmitted their annual Christmas Eve message
on 17.2 kHz CW using the Alexanderson alternator.
Recently, Nathaniel and I finished installing conduit and cable for a
VLF SDR and the PSWS ground magnetometer. We installed the VLF SDR and
active VLF antenna as well as the ground magnetometer and got both up
and running.
For many years, I wanted to be able to receive the SAQ Christmas Eve
transmission, but here in the US, it can be difficult. The
transmission was scheduled to occur at around 3AM EST or 8 UT. My VLF
SDR was recording the VLF band this snowy morning and captured the
spectrum. Unfortunately, the propagation conditions weren't the best,
but I was able to hear it, but just barely, and I mean just barely!
Here is a link to the mp3 file:
https://drive.google.com/file/d/1DhiKg9azAJzBZkv6rqFCXZQh1VZnhiSy/view?usp=sharing
Only at 14:40 into the recording can you just barely make out the 500
Hz downmixed carrier. I can maybe copy a few characters. If anyone is
interested how I created the file, here is a long pipe using
vlfrx-tools to read data from the data store, bandpass filter at 17.2
kHz center with 1 kHz bandwidth. Comments are added for description:
vtread -T 2021-12-24_07:41:30,+24m /data/vlf_96k | # read from data
store starting at 12/24/2021 7:41:30 UT for a duration of 24 minutes.
vtfilter -h bp,f=17200,w=1000 -g50 | # Insert a bandpass filter
with fc=17200 Hz, 1000 Hz wide with a gain of 50.
vtmult -f 16700 | # downmix carrier to 500 Hz using 16700 Hz local oscillator
vtmix -c 1,-j | # select the upper sideband
vtraw -ow | # convert to wav
lame -b64 -m m - SAQ122421.mp3 # encode pipe output to mp3
All is not entirely lost. The author of vlfrx-tools was able to
capture it at his location in the UK. Here is a link to his recording
where the whole message can be copied. At the very beginning of the
recording, there is a test transmission. Here is the link:
https://drive.google.com/file/d/1ruY291-G4sKk4DKJMUmTkSJaFjcvrkUC/view?usp=sharing
Credit to the author of vlfrx-tools for assistance on extracting the
recording and processing it. Much gratitude to Paul, the author of
vlfrx-tools, for his help, expertise, patience, and guidance
throughout the years and now, as well as his software and
documentation. Much gratitude to Nathaniel as well. For a recorded
live stream at SAQ in Grimeton and more information about the
transmitter, please see the Alexander Association's web site:
https://alexander.n.se/en/
Jonathan
KC3EEY
John Magliacane
Dec 24, 2021, 3:08:03 PM12/24/21
to Unknown, TangerineSDR Listserv, emum...@gmail.com
Jonathan,
I have made several attempts to copy SAQ in the past from New Jersey over the years, but the best I could do was see a weak trace buried under the noise using "baudline" spectrum analysis software. Still, this was enough to earn several QSL cards. :-)
I used baudline on your recording and could see a trace of SAQ at around 492 Hz, in between a lot of powerline harmonics spaced every 120 Hz.
Based on that success, I performed some additional bandpass filtering using the "play" feature of SoX, and I could clearly hear CW about 2 minutes into the recording! (VVV DE SAQ). I used a 20 Hz bandpass filter centered on 493 Hz (play -v 20 SAQ122421.mp3 bandpass 493 20).
You did it! Congratulations!
73 de John, KD2BD
I have made several attempts to copy SAQ in the past from New Jersey over the years, but the best I could do was see a weak trace buried under the noise using "baudline" spectrum analysis software. Still, this was enough to earn several QSL cards. :-)
I used baudline on your recording and could see a trace of SAQ at around 492 Hz, in between a lot of powerline harmonics spaced every 120 Hz.
Based on that success, I performed some additional bandpass filtering using the "play" feature of SoX, and I could clearly hear CW about 2 minutes into the recording! (VVV DE SAQ). I used a 20 Hz bandpass filter centered on 493 Hz (play -v 20 SAQ122421.mp3 bandpass 493 20).
You did it! Congratulations!
73 de John, KD2BD
Peter Laws
Dec 24, 2021, 3:08:54 PM12/24/21
to ham...@googlegroups.com
On Fri, Dec 24, 2021 at 12:56 PM Jonathan <emum...@gmail.com> wrote:
>
> Merry Christmas All!
>
> SAQ at Grimeton, Sweden transmitted their annual Christmas Eve message
> on 17.2 kHz CW using the Alexanderson alternator.
>
> Recently, Nathaniel and I finished installing conduit and cable for a
> VLF SDR and the PSWS ground magnetometer. We installed the VLF SDR and
> active VLF antenna as well as the ground magnetometer and got both up
> and running.
Very cool.
>
> Merry Christmas All!
>
> SAQ at Grimeton, Sweden transmitted their annual Christmas Eve message
> on 17.2 kHz CW using the Alexanderson alternator.
>
> Recently, Nathaniel and I finished installing conduit and cable for a
> VLF SDR and the PSWS ground magnetometer. We installed the VLF SDR and
> active VLF antenna as well as the ground magnetometer and got both up
> and running.
Numerous videos on YouTube showing the startup and operation of the
alternator and you really need to go find one (they seem to post one
for every activation). Go find some!
IIRC, Alexanderson himself was Swedish born and educated but crossed
the ocean to work for GE ... and it was GE that built these
alternators, presumably at Schenectady, including the one at SAQ.
Congress' 1912 radio act said "No private or commercial station not
engaged in the transaction of bona fide commercial business by radio
communication or in experimentation in connection with the development
and manufacture of radio apparatus for commercial purposes shall use a
transmitting wave length exceeding two hundred meters, or a
transformer input exceeding one kilowatt, except by special authority
of the Secretary of Commerce and Labor contained in the license of the
station [etc etc]. IOW, if you weren't passing radiogram traffic for
money, or doing radio R&D, you had to stay above 1500 kHz and use less
than 1000 W.
The law also says "Every station shall be required to designate a
certain definite wave length as the normal sending and receiving wave
length of the station. This wave length shall not exceed six hundred
meters or it shall exceed one thousand six hundred meters." IOW, most
stations not described above could operate anywhere except between
1600 and 600 m (187 - 500 kHz or so)
There are also regulations about operations at 600 m which was the
main distress wave.
SAQ, were it a US station, would meet the spec as its wave is 17430 m.
Really interesting stuff to dig into! Grimeton itself lasted so long,
well past the era of intercontinental radiogram traffic, because VLF
is a great for talking to submarines. :)
--
Peter Laws | N5UWY | plaws plaws net | Travel by Train!
Gary Mikitin, AF8A
Dec 24, 2021, 4:09:55 PM12/24/21
to HamSCI
Speaking of VLF…I was excited to hear ‘whistlers’ mentioned on the Dec 24th edition of the Science Friday radio program, from NPR (host Ira Flatow).
https://www.sciencefriday.com/radio/
Today’s segment was primarily about visible auroras…but the physicist (from a university in Wheaton IL, US), while discussing some of the details on how auroras occur, mentioned that they can be heard via radio reception. Ira Flatow said “ham radio operators are known to listen to whistlers” <paraphrased, as my memory is less than perfect>.
I always find it exciting when our geeky pursuits receive coverage in the mainstream media.
73 de Gary, AF8A
P.S. A few hours earlier, ham radio was the subject of yet another NPR story: Santa, direct from the Norh Pole, communicating over SSB to bring Christmas joy to children lucky enough or have a ham in their life.
Khan Tran
Dec 24, 2021, 4:15:50 PM12/24/21
to ham...@googlegroups.com, TangerineSDR Listserv, Jonathan Rizzo
Merry Christmas to you, your family and all of Hamsci and Tangerine group.
73, Khan KE8QWB
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Peter Laws
Dec 24, 2021, 5:39:59 PM12/24/21
to ham...@googlegroups.com
On Fri, Dec 24, 2021 at 3:09 PM Gary Mikitin, AF8A
<gmikit...@gmail.com> wrote:
> I always find it exciting when our geeky pursuits receive coverage in the mainstream media.
Shameless plug: A little out of the mainstream, but the Longwave Club
<gmikit...@gmail.com> wrote:
> I always find it exciting when our geeky pursuits receive coverage in the mainstream media.
of America's media, The Lowdown, has a Natural Radio column. Every
other month, US$15/year for e-version (upcharge for printed version
mailed). https://www.lwca.net/about.html
Part 97. Part 15, Part 5, Part 87, and all the ships at sea (Part
80!). Not limited to the USA, of course, and we do have a
correspondent in the UK that keeps us up to date with goings on over
there.
Peter
Gerald Creager
Dec 24, 2021, 7:48:08 PM12/24/21
to Unknown
Fascinating reading. A question: What impact will the Rocky Mountains have on VLF propagation and reception? Or, do I need to move in a month and investigate that myself?
73, and Happy Holidays to all!
gerry
Capt Gerry Creager, CAP
SWR Health Services OfficerWeather and Environmental Support Officer -- Incident Management Team
OKWG Asst Dir Communications Planning
(C) 979.229.5301
Civil Air Patrol, U.S. Air Force Auxiliary
gocivilairpatrol.com
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Jonathan
Dec 25, 2021, 7:32:12 PM12/25/21
to John Magliacane, Jonathan CCFL_Man, TangerineSDR Listserv, Unknown
Hi John,
Thank you! I cannot thank you enough for this great idea to filter it further. There is a lot of local interference. vtfilter’s bandpass filter is a brick wall filter and when I tried to filter the spectrum further, I didn’t get a good enough result. The bandpass filter that sox uses is a two-pole Butterworth filter and worked much better! I used “sox -v 20 SAQ122421.wav SAQ122421_20Hz.wav bandpass 493 20” and encoded to mp3. The file can be downloaded at https://drive.google.com/file/d/1KgLsOCMnkfhC5yBDN0bz8N0WOLn5uXZa/view
vlfrx-tools has a a few spectrum analyzing utilities and I was able to look at the non-coherent spectrum integrated over the duration of the transmission. It generated a plot with a little peak about 3 magnitudes above the noise floor. Plot below:
Thank you! I cannot thank you enough for this great idea to filter it further. There is a lot of local interference. vtfilter’s bandpass filter is a brick wall filter and when I tried to filter the spectrum further, I didn’t get a good enough result. The bandpass filter that sox uses is a two-pole Butterworth filter and worked much better! I used “sox -v 20 SAQ122421.wav SAQ122421_20Hz.wav bandpass 493 20” and encoded to mp3. The file can be downloaded at https://drive.google.com/file/d/1KgLsOCMnkfhC5yBDN0bz8N0WOLn5uXZa/view
vlfrx-tools has a a few spectrum analyzing utilities and I was able to look at the non-coherent spectrum integrated over the duration of the transmission. It generated a plot with a little peak about 3 magnitudes above the noise floor. Plot below:
I compared it to another plot created by Paul that shows a similar peak at the same frequency. My spectrum plot is attached showing the peak of SAQ’s carrier. To generate the plot: vtread -T 2021-12-24_07:46:00,+16m /data/vlf_96k > SAQ122421_96k_spec.vt and plotted 1:2 in gnuplot.
Thank you again for your confirmation!!
Jonathan
KC3EEY
Thank you again for your confirmation!!
Jonathan
KC3EEY
John Magliacane
Dec 25, 2021, 9:03:36 PM12/25/21
to ham...@googlegroups.com, Jonathan CCFL_Man, TangerineSDR Listserv
Hi Jonathan.
When you see stations giving 549 and 339 RST signal reports from EUROPE, you know copying SAQ from across the Atlantic isn't going to be easy...
I'm glad the SoX filtering worked out well. It's a fantastic tool that I use quite often for all sorts of things.
Incidentally, Baudline can also plot spectrum averaged over any region of a recording (see attached plots), and SoX can make spectrogram plots as well.
It may not improve matters much, but you can measure the frequency of those powerline harmonics and notch them out with SoX using multiple "bandreject" filters. That might clean up some the background "growl".
I think the slow QSB phenomenon that can heard in your recording (especially due to the low SNR) is normal consequence of nighttime propagation at VLF and LF. I have seen it in both amplitude and phase with WWVB at 60 kHz, and it appears in the daily 24 kHz NAA plots taken at the University of Louisville (http://moondog.astro.louisville.edu/naa/archive/plots/20211224.png).
73 de John, KD2BD
When you see stations giving 549 and 339 RST signal reports from EUROPE, you know copying SAQ from across the Atlantic isn't going to be easy...
I'm glad the SoX filtering worked out well. It's a fantastic tool that I use quite often for all sorts of things.
Incidentally, Baudline can also plot spectrum averaged over any region of a recording (see attached plots), and SoX can make spectrogram plots as well.
It may not improve matters much, but you can measure the frequency of those powerline harmonics and notch them out with SoX using multiple "bandreject" filters. That might clean up some the background "growl".
I think the slow QSB phenomenon that can heard in your recording (especially due to the low SNR) is normal consequence of nighttime propagation at VLF and LF. I have seen it in both amplitude and phase with WWVB at 60 kHz, and it appears in the daily 24 kHz NAA plots taken at the University of Louisville (http://moondog.astro.louisville.edu/naa/archive/plots/20211224.png).
73 de John, KD2BD
Jonathan
Dec 28, 2021, 7:54:36 AM12/28/21
to John Magliacane, ham...@googlegroups.com, TangerineSDR Listserv
Hi John,
I believe 329 is accurate to what you were able to squeeze out from my recording. I use sox quite a bit, but I wasn’t aware of the benefit of the filter in this case. The brick wall filter of vtfilter isn’t always the best choice. In sox, the bandpass filter is a 2-pole Butterworth and worked much better.
I’ll definitely give Baudline a try, especially with the autonotch feature. I’m in the process of trying to identify the source of those harmonics and mitigate them in my receiver. Unfortunately, they raise the noise floor, so weak signals can easily be missed.
Thank you again for all of your help and contributing to a successful copy! I submitted the information for an eQSL card.
Jonathan
KC3EEY
> <spectrum.png>
> <spectrum_average.png>
I believe 329 is accurate to what you were able to squeeze out from my recording. I use sox quite a bit, but I wasn’t aware of the benefit of the filter in this case. The brick wall filter of vtfilter isn’t always the best choice. In sox, the bandpass filter is a 2-pole Butterworth and worked much better.
I’ll definitely give Baudline a try, especially with the autonotch feature. I’m in the process of trying to identify the source of those harmonics and mitigate them in my receiver. Unfortunately, they raise the noise floor, so weak signals can easily be missed.
Thank you again for all of your help and contributing to a successful copy! I submitted the information for an eQSL card.
Jonathan
KC3EEY
> <spectrum_average.png>
Jonathan
Dec 29, 2021, 10:43:27 AM12/29/21
to ham...@googlegroups.com, tanger...@lists.tapr.org
Peter,
Thanks for the background and history! I watched this year’s recording of the live stream and really enjoyed it! Based on LWPC modeling, the carrier power was 3.1kW! LWCA’s The Lowdown is a great read! I’ll have to subscribe.
Gary,
I really enjoyed that radio program! He was speaking about auroral/dawn chorus as they are ducted, whistler-mode emissions. It was really cool to hear a conversation like that in the main stream.
Gerry,
I do believe LWPC (Long Wave Propagation Capability) modeling software takes into account terrain in making its predictions. My guess is that the mountainous terrain would only effect the ground wave, but minimally. According to the reception reports so far, SAQ was increasingly harder to copy the more west you went, and I believe the ground wave component was more prominent.
Jonathan
KC3EEY
Thanks for the background and history! I watched this year’s recording of the live stream and really enjoyed it! Based on LWPC modeling, the carrier power was 3.1kW! LWCA’s The Lowdown is a great read! I’ll have to subscribe.
Gary,
I really enjoyed that radio program! He was speaking about auroral/dawn chorus as they are ducted, whistler-mode emissions. It was really cool to hear a conversation like that in the main stream.
Gerry,
I do believe LWPC (Long Wave Propagation Capability) modeling software takes into account terrain in making its predictions. My guess is that the mountainous terrain would only effect the ground wave, but minimally. According to the reception reports so far, SAQ was increasingly harder to copy the more west you went, and I believe the ground wave component was more prominent.
Jonathan
KC3EEY
John Magliacane
Dec 29, 2021, 3:05:46 PM12/29/21
to ham...@googlegroups.com
Hi Jonathan.
On Wednesday, December 29, 2021, 10:50:30 AM EST, Jonathan <emum...@gmail.com> wrote:
> According to the reception reports so far, SAQ was increasingly harder to copy the more west you went, and I believe the ground
> wave component was more prominent.
We see this effect in the WWVB signal strength contours as well. Although the transmitter is located on Colorado, WWVB reaches the west and east coast of the USA with about equal signal strength levels despite their dissimilar distances.
Maybe it's terrain... Maybe it's ground conductivity... Maybe it's something else. The First Edition of the "Electronics Engineers' Handbook" edited by Donald G. Fink (1975, McGraw-Hill) states in Section 18-95 under "Propagation at Frequencies Below 150 kHz" that the Earth's magnetic field causes greater attenuation for propagation to the magnetic west than for propagation to the magnetic east.
See attachment.
73 de John, KD2BD
On Wednesday, December 29, 2021, 10:50:30 AM EST, Jonathan <emum...@gmail.com> wrote:
> According to the reception reports so far, SAQ was increasingly harder to copy the more west you went, and I believe the ground
> wave component was more prominent.
Maybe it's terrain... Maybe it's ground conductivity... Maybe it's something else. The First Edition of the "Electronics Engineers' Handbook" edited by Donald G. Fink (1975, McGraw-Hill) states in Section 18-95 under "Propagation at Frequencies Below 150 kHz" that the Earth's magnetic field causes greater attenuation for propagation to the magnetic west than for propagation to the magnetic east.
See attachment.
73 de John, KD2BD
Jonathan
Jan 2, 2022, 12:27:10 AM1/2/22
to ham...@googlegroups.com
Hi John,
Thanks for jogging my memory! I remember reading this somewhere. I’ll have to look at the LWPC documentation to see if it takes this into effect when it produces a result.
This book looks like a great read. I’ll be sure to get it. Thank you so much for sharing this!
Jonathan
KC3EEY
> <e-w_propagation.png>
Thanks for jogging my memory! I remember reading this somewhere. I’ll have to look at the LWPC documentation to see if it takes this into effect when it produces a result.
This book looks like a great read. I’ll be sure to get it. Thank you so much for sharing this!
Jonathan
KC3EEY
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> <e-w_propagation.png>
Bill Liles
Jan 2, 2022, 1:26:52 AM1/2/22
to ham...@googlegroups.com
John, thank you for the text from "Electronics Engineers' Handbook.” It gives a reference to reference number 125. Would you please be so kind as supply the information on that reference?
Thank you,
Bill
NQ6Z
To view this discussion on the web visit https://groups.google.com/d/msgid/hamsci/C3EFAD49-985A-40F0-BA3E-5227806AEC79%40gmail.com.
John Magliacane
Jan 2, 2022, 11:57:01 AM1/2/22
to ham...@googlegroups.com
Hi Bill.
On Sunday, January 2, 2022, 01:26:53 AM EST, Bill Liles <lil...@gmail.com> wrote:
> John, thank you for the text from "Electronics Engineers' Handbook.” It gives a reference to reference number 125. Would you
> please be so kind as supply the information on that reference?
Absolutely!
Bickel, J. E., J. A. Ferguson, and G. V. Stanley Experimental Observation of Magnetic Field Effects on VLF Propagation at Night, Radio Sci. Vol. 5, No. 1, pp. 19-25
A quick Google search returned a PDF of the article, which is attached for your convenience.
73 de John, KD2BD
On Sunday, January 2, 2022, 01:26:53 AM EST, Bill Liles <lil...@gmail.com> wrote:
> John, thank you for the text from "Electronics Engineers' Handbook.” It gives a reference to reference number 125. Would you
> please be so kind as supply the information on that reference?
Bickel, J. E., J. A. Ferguson, and G. V. Stanley Experimental Observation of Magnetic Field Effects on VLF Propagation at Night, Radio Sci. Vol. 5, No. 1, pp. 19-25
A quick Google search returned a PDF of the article, which is attached for your convenience.
73 de John, KD2BD
Jonathan
Jan 2, 2022, 12:10:19 PM1/2/22
to ham...@googlegroups.com
Hi John,
Thank you for providing this as well!
Jonathan
KC3EEY
> <rs005i001p00019.pdf>
Thank you for providing this as well!
Jonathan
KC3EEY
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> <rs005i001p00019.pdf>
Bill Liles
Jan 2, 2022, 1:01:15 PM1/2/22
to ham...@googlegroups.com
Thank you, John.
Bill
NQ6Z
To view this discussion on the web visit https://groups.google.com/d/msgid/hamsci/3547A834-71D2-4FD2-B59B-810667F85962%40gmail.com.
Julius Madey
Jan 2, 2022, 2:04:34 PM1/2/22
to Jonathan, hamsci
Happened across this in a google search...
https://www.sciencedirect.com/science/article/abs/pii/0021916971900754
73,
Jules-K2KGJ
https://www.sciencedirect.com/science/article/abs/pii/0021916971900754
73,
Jules-K2KGJ
Jonathan
Jan 3, 2022, 7:49:37 PM1/3/22
to Julius Madey, hamsci
Thanks Jules! I was able to obtain it through the University's online library.
Jonathan
KC3EEY
>>> athttp://hamsci.org/hamsci-community-participation-guidelines.
Jonathan
KC3EEY
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Julius Madey
Jan 4, 2022, 8:57:36 AM1/4/22
to Jonathan, hamsci
Jonathan,
My go-to guide for ferrites and noise suppression techniques is K9YC, Jim Brown, who wrote the book on RFI and audio system noise and interference problems.
http://www.k9yc.com/
"RF Interference in Audio Systems" is a good piece to start with
Jules-K2KGJ
My go-to guide for ferrites and noise suppression techniques is K9YC, Jim Brown, who wrote the book on RFI and audio system noise and interference problems.
http://www.k9yc.com/
"RF Interference in Audio Systems" is a good piece to start with
Jules-K2KGJ
Jonathan
Jan 4, 2022, 9:45:13 PM1/4/22
to Julius Madey, hamsci
Phil Erickson
Jan 4, 2022, 10:01:40 PM1/4/22
to Unknown, Julius Madey
Hi Jonathan,
I highly second Jules' recommendation for K9YC's work. Extremely comprehensive, he's been doing it for years. His "Choke Cookbook" is standard reading for anyone trying to make common mode suppression chokes at HF, for example, to avoid your feed line inadvertently becoming part of the antenna (short answer: you want > 5 kOhm resistance for the common mode). Since he comes from a professional audio background, you can also take that advice to the bank.
Since Ward is on this list, I'll let him comment on why one of the music groups he played with was named the "Pin 1 Problem" (read K9YC's work to see why).
73
Phil W1PJE
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