SCARS Weekly Newsletter December 15, 2017

December Club Meeting Remainders  
Winter Field Day
Power Supplies
Dates To Remember
The Doctor Is In,   
This Week’s ARRL Letter,   
ARRL DX Bulletin,   
Amateur Radio Newsline,   
Ham Nation,   
Odds and Ends,   
Upcoming Hamfests within 250 miles  _…_._

December Club Meeting Remainders

December’s meeting started with 56 and ended with about 60. It was the first cold morning and I think some just played hooky because of it.

After KE5JZN, Chris, reminded us of what occured last month (the most notable was awarding of Golden Thumbs!), we moved on to the Treasurer’s report by AG5LB, Jeff. The bottom line is “we ain’t broke”. N5UWY, Peter, reported that there were 2 new Techs and 2 upgrades to Extra at the VE session. Peter also gave us the Tech Committee report which included brief updates on Echolink (Kan/Okla has tower and equipment space located in OKC), and there was discussion of a new noise which has popped-up on the UHF repeater.

Nets are healthy! The Monday night 6m Net averages about 15 and has had good propagation of late. ARES is averaging between 45 and 50, even with the new 7:30PM start! The Gossip Net is still running in the mid to upper 20s, with the 10m Net having checkins from as far away as Choctaw and Marlow last week. And the Siren Net has very reliable numbers, but still needs more folk to cover several locations.

Info on ALL SCARS Nets can be found below the “Meetings” entry here…


AG5DV, Ed. and AG5DB, Peter, with an assist from AD5GG, Gordon did a presentation on WSPR. And there have already been new WSPR nodes put on the air in Norman.

A great meeting for a cold day!


Power Supplies

AD5GG, Gordon, published on his Blog, and later on a new Facebook page, a treatise with a concise overview of the strengths, weaknesses, advantages, and disadvantages of Linear and Switching Power Supplies. I present it here, but he has other great posts on his Blog and Facebook page which I’ll link at the end.

Great work, Gordon!

Switch-Mode vs Linear Supplies

Amateur radio transceivers demand power supplies which have a large current capacity. The average 100 watt radio transceiver requires over 20 Amps when in transmit mode.


A linear power supply uses a large heavy transformer to step down the input high voltage AC to a level close to the desired output. From there, the low voltage AC is rectified to DC, smoothed and regulated, yielding the final output voltage.

A switch-mode (also known as switched-mode, switching mode, and switching) power supply, in its simplest form, takes the high voltage AC, rectifies it to DC, smooths it, then uses circuitry to switch the high voltage DC on and off at a high frequency in the primary of a much smaller transformer. Smaller transformers can be used because generally speaking (although not always), switching at a higher frequency increases the efficiency. From there, this switched waveform is rectified and smoothed. There is a feedback loop which controls the on/off time (duty cycle) of the high voltage switching. This is what sets the final desired output voltage.

On the surface, it’s all about trade-offs in price, size, efficiency, and weight, for a given output rating. Switching power supplies can often be 50-80% smaller for a given output rating.

For example, the Astron RM-60M, (top right) which supplies 50 amps continuous, 55 amps peak. This supply is 5 1/4 x 19 x 12 1/2 inches in size, and weighs in at a cool 60 lbs (27.2 kg). The retail price for this supply at the current time is $559.95.

Compare this with the TekPower TP50SW, (right) which supplies 50 amps (max). This supply is  14 x 10.1 x 5.8 inches in size, and weighs in at 6 lbs (2.7 kg). The retail price for this supply the current time is $149.99.

Switching at a higher frequency than 50/60 Hz brings you a ten-times reduction in weight, and almost a four-times reduction in price.

It’s a contentious subject, especially when it comes to amateur radio, mainly because of one word….


In the examples above, the Astron RM-60M boasts less than 5 mV of ripple at its rated current output, whereas the TekPower TP50SW spec is less than 100 mV of ripple. Switching power supplies generally have more output ripple and create more common mode noise than linear supplies, but how important is this to you in your application? What sort of device are you running which can’t handle 100 mV of ripple? What are the frequencies of this ripple and noise? Any decent ham radio worth its salt will have plenty of supply filtering in place to reduce ripple and noise. There will be chokes in there, capacitors with a low impedance at a wide range of frequencies, helping to lower the negative impact of this DC supply-borne noise.

Switched mode power supplies generate switching noise. This noise is often in the radio spectrum, and can contain discrete frequencies, harmonics, and broadband noise. It is generated primarily via the switched currents in the main switching devices. These switched currents are of a large magnitude, they change rapidly over very short time periods (di/dt), and unfortunately ringing and oscillations occur, which can be a main source of conducted and radiated RF and EM interference.  Other sources of interference can include rectifier diode recovery, and input filter capacitors. Switching noise can be effectively reduced with careful design and PCB layout.

Switching supplies are also notorious for conducting noise onto the AC power supply line. I think this is partly due to a massive influx of cheaply made switching power supplies over the last couple of decades. I’m talking about things like cell phone & tablet chargers, laptop power supplies, battery chargers, and other small DC-powered appliances. The issue is one of cost – these things are manufactured by the million, and must be cheap. Cheap switching power supplies mean that not only does the line input and/or output filtering get slimmed down or removed, and the actual supply itself is made from minimal components, often due to size restrictions. See Ken Shirriff’s teardown blog post on the Apple iPhone charger for an example of such miniaturization. There is a link on that page also to a teardown of a cheap Chinese ripoff iPhone charger. Also see Dave from EEVBlog’s iPhone charger teardown video. The difference is startling. Also, while we’re on the subject of small, cheap Chinese switching supply teardowns, I highly recommend Big Clive and his YouTube channel for some fantastic teardowns of chargers, inverters, etc, some of which are incredibly crap, and/or dangerous.

Back to ham radio… partially what inspired this post was a thread on Facebook (I know, I know) discussing the common mode power supply filter which Icom supply with their IC-7300 radio in the UK and Europe. This filter (OPC-1457R) was investigated nicely by DG1SFJ here (english translation) where he measures the response on a network analyzer. The rejection is rather good, and so I was surprised to read people’s responses on Facebook where they vehemently refuse to connect these filters between their supply and their radios. I think it would be a good move to use this filter, and I’d use it if my IC-7300 came with one. I don’t know about you, but I see having 60 dB+ of rejection across the HF bands as a good thing. Apparently the bone of contention is one of “but the volt drop is too much”. I can’t comment. While this filter should improve things when it comes to conducted emissions from the power supply. It won’t help you when you’re up against a radiated emissionsproblem.

We’ve established that switched mode power supplies generate switching noise, but they do have to comply with the standards in place (FCC, CISPR, etc). A well-designed, good quality switched mode supply will employ heavy line input filtering, preventing any noise generated from appearing back on the mains supply, allowing it to pass compliance testing, but also helping to prevent any similar noise currently on the AC supply from leaking into the switching supply. In a world full of bad quality switch mode supplies (such as detailed above), this is a good thing. On the other hand, generally speaking, line input filters are not used on linear power supplies. The only components the AC sees before it arrives at the transformer primary are maybe a fuse, a PTC, maybe some MOV’s… Depending on the reactance of the main transformer and other circuitry to the frequency of mains-borne interference, there may be little between it and your DC powered devices.

Either way, in the battle against interference, it is useful to acquaint yourself with the standards. This way, you can research any electrical device before purchase, and be confident of its performance as far as interference emission goes. However, in looking at FCC part 15, and EN55022 regulations, the first thing you’ll notice of interest (if you’re into amateur radio) is that there is apparently no restriction on radiated emissions below 30 MHz. Emissions testing below 30 MHz are focused on conducted emissions only.

With that in mind – what do the various regulations look like in regards to the amateur radio HF bands (1-30 MHz) ?

FCC limits are expressed in μV, while CISPR/EN55022 limits are expressed in dBμV, so avoid confusion, we’ll put them all in the same units: dBμV = 20Log(μV).

For example, in the 40 m band (~7 MHz):
FCC Class A limit is 3000 μV, FCC Class B is 250 μV.
CISPR/EN55022 Class A limit is 1000 μV, CISPR Class B is 316 μV (average).

You can see that the European EN55022 standard is more strict compared to the FCC part 15 limit when it comes to the less-restrictive Class A limit, and there’s really not much difference in Class B limits.

What is 316 μV anyway?? It’s nothing, right? Sure, it doesn’t sound like a lot, but if we convert 316 μV into dBm in a 50 ohm system, you’re looking at -57 dBm, which is somewhere between S9+10 dB and S9+20 dB on your S-meter.

FCC part 15 limits

FCC Class A Conducted EMI Limit
Frequency of Emission (MHz) Conducted Limit (μV)
0.45 – 1.6 1000
1.6 – 30.0 3000
FCC Class B Conducted EMI Limit
Frequency of Emission (MHz) Conducted Limit (μV)
0.455 – 1.6 250
1.6 – 30.0 250
FCC Class B 3-Meter Radiated EMI Limit
Frequency of Emission (MHz) Field Strength Limit (μV/m)
30 – 88 100
88 – 216 150
216 – 1000 200
above 1000 200
FCC Class A 10-Meter Radiated EMI Limit
Frequency of Emission (MHz) Field Strength Limit (μV/m)
30 – 88 90
88 – 216 150
216 – 960 210
above 960 300

CISPR (EN55022) limits

CISPR Class A Conducted EMI Limit
Frequency of Emission (MHz) Conducted Limit (dBμV)
Quasi-peak Average
0.15 – 0.50 79 66
0.50 – 30.0 73 60
CISPR Class B Conducted EMI Limit
Frequency of Emission (MHz) Conducted Limit (dBμV)
Quasi-peak Average
0.15 – 0.50 66 to 56* 56 to 46*
0.50 – 5.00 56 46
5.00 – 30.0 60 50
CISPR Class A 10-Meter Radiated EMI Limit
Frequency of Emission (MHz) Field Strength Limit (dBμV/m)
30 – 88 39
88 – 216 43.5
216 – 960 46.5
above 960 49.5
CISPR Class B 3-Meter Radiated EMI Limit
Frequency of Emission (MHz) Field Strength Limit (dBμV/m)
30 – 88 40
88 – 216 43.5
216 – 960 46.0
above 960 54.0

*Decreases with the log of the frequency.


Switched mode power supplies, if designed and made well, contain good shielding, aggressive line input filtering, snubber networks, other EMI/RFI countermeasures, and filtering which make them a totally viable alternative to very heavy and very expensive linear power supplies. Cheap, badly made switching supplies may eliminate some or all of the above in the interest of cost.

Arbitrarily labeling all switched mode power supplies as “bad”, or “noisy” and stonewalling on the subject doesn’t help. Do some research, and most of all – don’t buy a cheap/crap switched mode power supply and complain about noise. You get what you pay for.

A good switched mode power supply from a reputable company is going to be cheaper and lighter than a linear power supply from a reputable company of similar specification.

FCC Class A, Class B Overview

Here’s a good video detailing the FCC conducted & radiated emissions limits.

Combating Conducted Emissions

We should be able to rely on compliance with the emissions standards which are laid out, but we all know the world is full of cheap devices which are polluting the supply. What can you do about this? Here are a few suggestions.

For high quality power cords with built in EMI/RFI filtering, see EMC EUPEN

Palomar Engineers also is a great resource for filtering,

Check out Mouser or Digikey and search for ferrite toroids. Buy some large ones and wind your power cords around them multiple times. Choose carefully, as not all ferrite mixes are the same.

Gordon’s Blog can be found here:

His Facebook Page is here:

Dates To Remember

Some VERY important events are scheduled in the near future which you need to put into your planner:

ARES Net *NEW TIME* – 7:30PM, Each Tuesday, 147.06 repeater

Santa Net – Nightly 7:30 PM through December 24th, 3916 Khz –

January 4 – SCARS VE Testing –

January 13 – SCARS December Meeting –

The Doctor Is In

The Doctor’s Latest Podcast is titled
Listener Mailbag

The Doctor devotes the entire episode to answering listener questions!

Listen to it here-> The Doctor Is In Podcast

The Doctor’s Home page is here: The Doctor Is In

This Week’s ARRL Letter

Most Recent Headlines:

Read it all here: ARRL Letter

ARRL DX Bulletin

DX Bulletin 50 ARLD050
From ARRL Headquarters
Newington CT December 14, 2017
To all radio amateurs

ARLD050 DX news

This week’s bulletin was made possible with information provided by
the OPDX Bulletin, 425 DX News, DXNL, Contest Corral from QST and
the ARRL Contest Calendar and WA7BNM web sites. Thanks to all.

VIET NAM, 3W. Dirk, DF2XG is QRV as 3W9XG from Hai Phong while here
on work assignment. Activity is in his spare time on 40 to 10
meters using CW. His length of stay is unknown. QSL via operator’s

GEORGIA, 4L. Vlad, UA4WHX will soon be QRV as 4L/UA4WHX. Activity
will be on 40 to 17 meters using CW, SSB and RTTY. His length of
stay is unknown. QSL to home call.

CYPRUS, 5B. Alex, 5B4ALX is QRV as special event station 5B4XMAS
until December 31. Activity is on 160 to 10 meters using CW, SSB
and various digital modes. QSL via IZ4AMS.

SENEGAL, 6V. Members of the Amateur Radio Association of Senegal
are QRV as 6V1A from Goree Island, IOTA AF-045, until December 17.
Activity is on the HF bands using CW and SSB. QSL via 6W7JX.

BARBADOS, 8P. Ernest, J69Z is QRV as 8P9JB until January 2, 2018.
Activity is on 80 to 10 meters. QSL direct to home call.

PALESTINE, E4. Elvira, IV3FSG is QRV as E44YL from Bethlehem until
December 18. Activity is on the various HF bands using SSB and
possibly digital modes. QSL via IK3GES.

SOUTH COOK ISLANDS, E5. Mauri, AG1LE is QRV as E51DXX from
Rarotonga, IOTA OC-013, until December 29. Activity is holiday
style on the HF bands using SSB, PSK31 and FT8. QSL to home call.

CANARY ISLANDS, EA8. Rieder, HB9FIH is QRV as EA8/HB9FIH from El
Hierro Island, IOTA AF-004, until the end of March 2018. Activity
is on 80 to 10 meters, and possibly 6 meters, using CW, RTTY, PSK,
and some SSB. QSL to home call.

SOLOMON ISLANDS, H4. Shane, VK4KHZ is QRV as H44DA from Busone,
Malaita Province until early January 2018. Activity is on 80 to 10
meters, and satellite SO-50, but with a primary emphasis on 6
meters. QSL direct to home call.

REPUBLIC OF KOREA, HL. Special event call DT23WOP is QRV until
February 28, 2018 during the Winter Olympic Games that will be held
here. QSL via HL1IWD.

DJIBOUTI, J2. Dane, S53T is QRV as J28ND until December 17.
Activity is in his spare time on the HF bands using CW, SSB and
RTTY. QSL via S57DX.

SVALBARD, JW. Morten, LA4JSA is QRV as JW4JSA from Bear Island,
IOTA EU-027, until June 1, 2018 while on work assignment. Activity
is in his spare time on the various HF bands. QSL to home call.

BELGIUM, ON. Members of the Club Radio Durnal will be QRV as
OT100BCA on December 17 from the Royal Castle of Laeken. QSL via

POLAND, SP. Special event station SN20WHL is QRV until December 20
to draw attention to the city of Torun that was put on the UNESCO
World Heritage List 20 years ago. QSL via SP2TMT.

CORSICA, TK. Georg, NZ1C will be QRV as TK/NZ1C from December 16 to
24. Activity will be holiday style on 40 to 10 meters using mainly
CW, with some SSB, RTTY, PSK and FT8. QSL via DD5ZZ.

UKRAINE, UR. Members of the amateur radio club Band are QRV as
EM25IWW until the end of the year to celebrate the club’s 25th
anniversary. QSL via UR7IWW.

INDIA, VU. Members of the Manipal Institute of Technology radio
club are QRV as AT6MIT until January 7, 2018 to celebrate the
institution’s 60th anniversary. QSL via VU3BUN.

ROMANIA, YO. Special event station YP2018HNY will be QRV from
December 15 to January 15, 2018 to celebrate Christmas and the New
Year 2018. Activity will be on the HF bands. QSL via YO3KPA.

Sprint, 80-Meter QRP CW Fox Hunt, NCCC CW Sprint, UN DIGI Contest,
AGB-Party Contest, Russian 160-Meter Contest, Feld Hell Sprint, OK
DX RTTY Contest, Padang DX Contest and the Croatian CW Contest are
all on tap for this upcoming weekend.

The Run for the Bacon QRP CW Contest is scheduled for December 18.

The CWops Mini-CWT CW Test, Phone Fray and 40-Meter QRP CW Fox Hunt
are scheduled for December 20.

Please see December QST, page 73, and the ARRL and WA7BNM Contest
Web Sites for details.

Always Latest version at the top here:  ARRL DX Bulletin

Amateur Radio Newsline





The “SCRIPT” and “AUDIO” above are hotlinks. Click to either to “read” or “listen”!

Live links, Script, and Audio here:

 Amateur Radio Newsline – Latest News

Ham Nation


Episode 329’s highlights:

“The Geminid meteor shower,
more about balanced/unbalanced audio with George,
DX Files with Val,
and more!

The last half-dozen or so episodes are linked right here: Ham Nation

Go watch!

 Odds and Ends

Upcoming Hamfests within 250 miles

Link below lists all the ARRL-related hamfests within a 250 mile drive of Norman for about the next 5 months. Lots of good ones close to Norman.

As always, News, Links, Repeater Info, Hamfests, Licensing, General Help & more linked from the sidebar at the SCARS Homepage – W5NOR.ORG !!!

73 de Gary, WB5ULK …_._

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