PA3CLQ's Leuke Linken Nr. 379


When was the abbreviation "SK" introduced into the vocabulary, as a short form for "Silent Key" ?
I never recall having heard it from the people who taught me Telegraphy, or during my years on the Philadelphia Leased Wire.
I think it is something from the radio-side of our little fraternity.
Warren McFarland would probably the best source of information about this.
abram burnett


Despite almost 75 years as a telegrapher, I never heard of "SK" as an abbreviation for Silent Key until a few years ago, probably on this forum.

It may have come from the wireless group as suggested, but my guess would be that it is a homegrown abbreviation which somebody used trying to lessen his/her typing burden, and it caught on.

Who that person is, is anybody's guess.

They might not even know themselves what they started.
73 - Warren McFarland


SK has been used for Silent Key in amateur radio circles for at least 40 years, probably much longer.

Many of our abbreviations and pro-signals can be traced back to American Morse and the telegraph.

SK in International Morse is almost the same as 30 in American Morse.

It's interesting to look at the stories behind these things!
73, Mike SV W0VTT

The writer is a УCanuckФ Ц 85 yrs old in Feby Ц2015- been on landline- Commercial and Railway since 1948 and УSKФ Ц is NOT known in our HOUSE of УglossaryФ of abbreviations Ц in Canada! Never heard it used on landline, the CANADIAN HUB - nor amateur radio nets!

gs@OA   G.Schrader

Former ORT & VE3GLS ( Advance license)


I concur.

I just examined some of the earliest copies of Dots & Dashes I've acquired from the early 1980's and the column listing recently deceased members was titled "Silent Keys 30" The number 30 is of course from the Western Union 92 code and means "no more - the end" and apparently was particularly used by press telegraphers when they were done transmitting whatever material they had.

It is well known that the International Morse prosign SK came from American Morse use of 30 as SK and 30 share the same code pattern (except with 30, the last dash is longer) and SK also means "end" whether "end of contact", "end of work", "end of transmission", no more to send.

So at least back to the early 80's, land line telegraphers or at least those who were members of the MTC used "30" to mean "deceased" so it follows that SK would mean the same thing as it is the same thing...

Just my two cents...

73, Chris Hausler


SK is one of many amateur radio prosigns that had its roots in landline telegraphy.

The prosigns are usually written with a bar across the letters to indicate that they are sent with no character space between the letters.

Prosigns are used in CW and are really important in message handling (the original ARRL format from the early 1920's, not the new-fangled e-mail format that is popular on the newer digital modes).

SK means the same as 30 and has the same dot/dash pattern.

Before electronic keyers became common, the last dash of the K was often elongated a bit - probably a hold over from telegraphers that became hams.
    I don't know when or if "Silent Key" was used in telegraphy, but in ham radio it was around back to at least the 40's (I've seen the Silent Key column in back issues of the ARRL's QST at least that far back).

It was probably in use much earlier.

Since the prosign for "no more" was SK, I wouldn't think it would take long before someone equated "Silent Key" with "SK".

I would say that the prosign existed before the "Silent Key" term came into being, but probably not by much.

It would be easy to see how far back that went by searching the QST back issues.

As I noted in the past, the Armed Forces Communications and Electronics Association's journal still puts ". . . _ . _" at the end of each article.

I would wager that very few members of AFCEA know what that means or where it comes from.
    It is an interesting study to note the parallels between telegram format/handling as described in the old reference and instruction books and the CW message procedures outlined in the ARRL Operating Manual (at least those prior to 1980 - I don't have any of the newer editions).

There are some differences, but it doesn't take long to understand one if you know the other.
73, Chip Morgan


I just finished reading a novel by Michael Connelly, a crime fiction author who had been a reporter for the LA Times.

The novel was about a .... crime reporter working at the LA Times, of course.

The story revolved partially about the reporter getting "downsized" as the paper was cutting back.

The layoff list is called "The Thirty List."
"I just heard," he said.
"How? I just found out myself five minutes ago."
"Jack, you know I can't reveal.

But I've got the whole place wired.

You just walked out of Kramer's office.

You made the thirty list."
"The thirty list was a reference to those who had been lost over the years in the downsizing of the paper.

Thirty was old-time newspaper code for 'end of story.' "
From "The Scarecrow" by Michael Connelly.
Not hard for me to see how it would transfer to losing one of our borhters of the wire.

Of course, it did start with telegraphy.
It was a good read, too, by the way.
73, Skip


Largest Radio Transmitter Is Dedicated 1953-11-18 Universal Newsreel; VLF Submarine Communication

The conversation reminded me of an old newsreel I ran across a long time ago.

Found it again on "Youtube."
Check out this video on YouTube:

James Wades


Hello SKCC members, (and others)

We have talked many times about long lever keys.

Amplidan / MP and the Marconi keys from PS-213 to Marconi 365 series, the long NATO type keys, the so called ITT/Oslo key with the clear plastic case and the Lennart Pettersson that has no bearings, it uses a torsion suspension which can be controlled by a screw to adjust the spring tension, a key that was sold for many years by Swedish Radio Supply store at:

There is one more that has an interesting history, first built for the Great Northern Telegraph Company, made in Denmark, then made in England where it was made until the company went out of business.

One is up for auction:

The earlier models were heavier but the later models with the plastic construction kept the fast keying action of the older keys, so operationallly they were the same.
I have one of the plastic base ones and I like it very much.
I do not know the seller, I have no interest in the auction, I just know I don't see these keys every day and they are a good key.
73, DR, D.J.J. Ring, Jr."


CW QSO signal reporting.

(A part of)

Following up on the recent ''Out & About'' newsletter item regarding signal reporting, I thought I would share feedback from the International CWSideswiper Net of this morning.

A 2-2-9 report was given for one of the alternative frequencies used, as well as this 1-1-9 report from 20m.

Information is still able to be exchanged, albeit with some difficulty, in such cases.

This may be a regular occurrence due to prevailing conditions at the time, but simply highlights the supremacy of CW as a communciation mode, & a century of that ought not to be blurred by decision-makers with modern mindsets that happen to be SSB-aligned.

de Doc/VK5BUG


(A part of)

Greetings from Down Under

Following a recent VK5 & national SOTA/WWFF etc newsletter item which identified a signal report of 1-1 or 1-1-9 being ''impossible'', I compared the descriptions attached to each of the RST & QRK/QSA reporting mechanisms.

73 de Doc, Dr. David Wescombe-Down VK5BUG, "Beethoven of the Cootie Key",


R part of RST.


  1. Unreadable
  2. Barely readable, occasional words distinguishable
  3. Readable with considerable difficulty
  4. Readable with practically no difficulty
  5. Perfectly readable

73, DR, D.J.J. Ring, Jr."


Now, is it true.........

that sounders and resonators sound different down there in AU and NZ .....

because the sounder's lever has to pull up against gravity instead of dropping down? 
73, Skip


Skip, get outta here with that.

What a laugh!

We have a name for guys like you down this way, a "card". (a rather complimentary term meaning an amusing or entertaining guy).
73, Maurie

Appendix D: Sounder driver in the MorseKOB 2.5 Tutorial...............  

gives a schematic for attaching a sounder to a computer.

I assume that the value of the battery is that for the impedance of the particular sounder.
There seems to be some differences of opinion as to the proper value of voltage to use with the different impedances. Any suggestions?
I may purchase a sounder from eBay. Any suggestions?

I don't want to put a bunch of money in it since I'm not a collector.

I just want one that will work.
73, George


Hello George -
Yes, you select the voltage to provide the proper current through the sounder.

Generally, the 120 ohm sounders like about 60 mA and the 4 ohm sounders like 240 mA.

Ohm's Law is your friend.

You should also put a series resistor in line with the sounder of about the same resistance; this is to prevent ALL of your resistance from being inductive.

More info here:  (URL 1)

Chip Morgan offers a very nice ready-made interface circuit: 

There are plenty of sounders available, don't pay too much for one!
73, Mike W0VTT


As Mike mentioned, the loop current is really the parameter that you want to control and it varies depending on the instrument resistance.

The table at:

is a very handy reference.

That being said, there are a few other considerations that might affect your choice of loop supply voltage.
    As I don't know your background in DC electrical theory, I apologize if I am covering things you know.

Mike mentioned something called Ohm's Law.

This is an equation that governs the relationship of voltage, current, and resistance in an electrical path (for telegraphy, it is a DC, or direct current, path).

That's where the numbers come from in the table above.

Other than the recommended operating current for each type of sounder or relay, the voltage drop column is important in that it basically gives you the minimum power supply voltage that will generate the recommended current for each resistance.

For example, a 4 Ohm sounder has a voltage drop of 0.96 Vdc at its operating current of 240 mA.

So, this sounder could be run with a AA battery (1.2V) if you wish, but the battery would not last very long.

But, a 6V or 9V battery would have too much voltage for the sounder and that would mean the current would be too high.

This would likely result in the coils of the sounder being damaged.

On the other hand, a 400 Ohm sounder would need a 12 Vdc supply.

These are the values for a SINGLE instrument only.

If you used 2 instruments in the loop, there would be more voltage drop and you need a higher supply voltage - six 4 Ohm sounders in series can be safely run with a 6V battery.
    If I understand you correctly, you are desiring to hook up just a single sounder in your loop.

This makes your choices of sounder much easier - if you use multiple sounders, you want them to use the same current, ie. they all have the same resistance.

In your case, you can use whatever sounder you find that is in good shape and fits your budget.

Many of the later sounders can be found at very reasonable prices.

They can generally be identified by having screw terminals for the connections as opposed to the brass binding posts of earlier models.

You will want to make sure that the coils have continuity to avoid having to repair or re-wind them.

Unless you really know what you're getting into, you'll want to get some advice from folks on this list as well as on the slowspeedwire list. I can give you some folks to start with if you wish to contact me off list.

I'm sure many others on the list also will have some good recommendations.

I have had some good luck getting later sounders for very reasonable cost from E-Bay, but I have also gotten some that i've wanted just for parts, so you have to be careful and try to ask questions of the seller if you aren't sure.

Most of them probably won't know the answers, but some do.

I judge my risk based on how well the photos show the pertinent details of the sounder.

But as with anything on E-Bay, it's buyer beware.

I would start with folks on the lists and members of MTC if you don't know what you want.

Here is an example of an item on E-Bay that might be something that would work for you:

The seller refurbished it and in so doing, ruined any patina and also took the black coloring off the brass coil covers.

Essentially, it's pretty, but it's not collectible in that condition.

What I would worry about are the coil connections and whether those are still good.

The connecting wires underneath look OK, but did the seller mess up the coils when they cleaned it up?

It's also missing the small wooden feet that go under the recesses for the mounting screws.

These are commonly missing on many sounders and can be replicated with a piece of dowel that has a hole drilled in it.

You want to have the feet for the sounder to resonate properly.

If you got it cheap enough, it might be worth trying it.

I wouldn't pay more than $20 - $25 for it and would certainly want to know what they did with the coils.

Others may have a different opinion, but it's an example of the later screw terminals.
    You may want to wait to get a sounder before you determine your power supply voltage, but it's not absolutely necessary because Ohm's Law will let you add a dropping resistor to a higher voltage supply to get the desired operating current.

Many folks use small "wall wart" types of supplies that they may have laying around or you can find many places for very reasonable prices.

Almost any of them will have enough capability to provide the currents needed for a small telegraph loop.

If you are not familiar with choosing appropriate dropping resistors, I or others can help you select one that is non-inductive and has a high enough power rating. If you have an old wall wart or even an old laptop power supply, they might work out just fine for you.
    You'll also want a key of some sort if you want to fully simulate the operation of a telegraph circuit.

There are many reasonable straight keys available and even some cheap AMECO-type keys will work.

The most important part of the key is the shorting lever.

Telegraph circuits are a closed-circuit system so when you aren't sending, the key must be closed to receive and allow others to send.

If you are familiar with semi-automatic keys ("bugs"), like Vibroplex and others, they can also be used if they have a circuit closer lever.

If you have never used a bug, I would suggest starting with a straight key.

Like sounders, the later ones are less expensive and are readily available.

You'll see some referred to as having legs or being "legless".

The keys with legs are usually earlier and more expensive and they were meant to be mounted to a table/desk top by drilling holes for the long "legs" to be attached through the top.

Legless keys can be attached to a top by 2 mounting screws or fastened to a small mounting board and then moved around for comfort or convenience.

For your purposes, you most likely would like a legless key.
    The other important thing you will want to consider, especially for use with a computer, is a "snubber."

The snubber was originally used at the key to prevent the sparking that occurred when the key was opened.

The sparking would eventually eat away at the key contacts they would have to be constantly maintained for reliable operation.

The snubber killed the spark thus prolonging key contact life.

The spark would arise from something called "back EMF" which refers to a voltage generated by a coil when the DC circuit is interrupted (such as by opening a key).

I won't get into the theory of why this occurs other than to say it is generated at the sounder coils since they are very large inductors.

While we are concerned about our key contacts, the bigger concern is that the computer and USB adapter really don't like to see these high voltage spikes (they can be hundreds of volts)!

You can see various methods of snubbing the circuit at:

I prefer to use the transorb (TVS Diode) attached directly across the sounder terminals.

This puts the snubber right where the problem starts and takes care of both the key contact and computer/interface issues.
    As far as an interface, you can build your own from the diagrams on Les Kerr's website or, as Mike mentioned, I have developed a turnkey interface that is an improved version of Les' original circuit. Information of that interface is found at:

I also have some bare PC boards available if you have a large junkbox and like building things.

All of the information about the interface is on the web site, but I do need to get the board files and schematics updated soon.

No major changes, but I do want to keep the info updated.

I also try to keep boards and material on hand so that I can send out an interface within a reasonably short time after getting an order.

The turnkey interface can be used with or without a key in the loop and will handle voltages of 50Vdc or less.
    I hope that I haven't confused you.

I've gone into much more detail than you really need to just hook up a sounder to an interface, but I wanted to give you some idea of all the options you have for getting on the wire with MorseKOB.

Please feel free to ask me more questions either here or off list. I'd be happy to help you out or refer you to someone that might have a better answer than I.
73, Chip Morgan


Nothing to do with Railways,,,,,,,

but see my key on a tobacco can.................hi

Nice smell and sound when they are together in action.

73, Henk PA0HTT Ommen NL



73, your editor PA3CLQ



My simple website about Gigantic DF-Antennas

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