UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Amateur and Military Radio

Notices

Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment.

Reply
 
Thread Tools
Old 17th May 2020, 11:05 am   #1
toshiba tony
Heptode
 
toshiba tony's Avatar
 
Join Date: May 2006
Location: Accrington, Lancashire, UK.
Posts: 680
Default Morse Pitch

This lock down is certainly exposing the odd-balls, I'm getting to be one too, there's a guy elsewhere on here asking about a full wave rectifier in a single envelope, very ingenious thinking. It has set me off with this one, before the days of frequency synthesis etc, how was the the pitch chosen that you transmitted Morse. And was the reason for different frequencies to help ID senders? On the old spark gap transmitters how was the tone generated, thank you anybody. As a mere tv engineer for fifty years I never got into Amateur Radio.
toshiba tony is offline   Reply With Quote
Old 17th May 2020, 11:40 am   #2
Dave757
Hexode
 
Join Date: Apr 2009
Location: Scratby, Norfolk, UK.
Posts: 457
Default Re: Morse Pitch

Hi Tony,

Morse is normally transmitted by Amateurs by simply keying a carrier wave.
The tone is selected by the receiving station by the use of a beat oscillator to
create the tone of their choice.

There is another method whereby the sender can superimpose a keyed tone on
the carrier wave. This is often used for on air morse classes typically on VHF
FM.

With Spark, I guess you could just call this a rasping tone, which could be detected
easily using most types of receiver, including the crystal receivers of the time.

There was another mode used before and during WW11 called ICW, where the
carrier was keyed as in CW morse, but a 'tone' was provided by an interruptor
in the anode circuit of the PA valve.

Kind regards
Dave
Dave757 is offline   Reply With Quote
Old 17th May 2020, 11:48 am   #3
SiriusHardware
Dekatron
 
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 4,055
Default Re: Morse Pitch

When you're transmitting CW ('Continuous Wave') on a modern transmitter you aren't actually transmitting a tone.

The sending transmitter sends an unmodulated RF signal - short transmissions are 'dots', long transmissions are 'dashes'.

The tone heard when CW is being received is locally generated within the receiver, by the incoming signal being mixed with an internal RF oscillator. The tone you hear is the audio frequency difference between the frequency of the incoming signal and the frequency of the internal oscillator. If this mixing is done in the IF stage of the receiver, the internal oscillator is sometimes called a Beat Frequency Oscillator (B.F.O.)

Spark gap transmitters -were- tone modulated, in the sense that the because the transmission was being continually interrupted, the RF carrier was crudely 'amplitude modulated' during the transmitter 'on' phase. This meant that the transmissions could be received on / demodulated by a simple A.M receiver. The received tones would sound like a very rough buzz or tone.

Edit: As Dave pointed out, Morse is sometimes transmitted as an audio tone via 'phone' methods of modulation such as FM. (As it is for repeater idents, for example). The tone can be any audio frequency you like in that case.

Last edited by SiriusHardware; 17th May 2020 at 12:15 pm.
SiriusHardware is online now   Reply With Quote
Old 17th May 2020, 12:06 pm   #4
GMB
Nonode
 
GMB's Avatar
 
Join Date: Aug 2003
Location: near Reading (and sometimes Torquay)
Posts: 2,338
Default Re: Morse Pitch

As previously said, Morse is usually CW so only the carrier is transmitted.

But some transmitters did offer MCW where the carrier did indeed have a tone modulated on it, this being for the situation where the receiver was not going to be a communications receiver, i.e. did not have a BFO, or maybe the transmitter VFO was going to drift a lot.

When MCW was used it was typically modulated 800-1000Hz, which is similar to the typical BFO offset commonly used.
GMB is offline   Reply With Quote
Old 17th May 2020, 2:20 pm   #5
Radio Wrangler
Dekatron
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 14,097
Default Re: Morse Pitch

Different people have different hearing, so there is a spread in preferences for the tone presented to the lug 'ole.

Considering how ears work, it would seem sensible to move the tone around a bit from time to time to have a bit of variety.

Most serious Morsistas I know seem to like wider receiver bandwidth for less ringing, and they listen to several stations at once with their tones spread across a range. They grew up doing so while supping at a pot of tea, smoking a ciggy and holding conversation with anyone who dropped into the radio room!

With straight forward A1A keying of the carrier, the tone heard, as already described, is set by adjustment of receiver tuning and BFO, so the operator just tunes to their liking.

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is online now   Reply With Quote
Old 17th May 2020, 3:00 pm   #6
Tyso_Bl
Hexode
 
Tyso_Bl's Avatar
 
Join Date: Jul 2014
Location: Magor, Monmouthshire, Wales, UK.
Posts: 384
Default Re: Morse Pitch

So, do you have a preferred pitch? Mine is around 400 / 500Hz, but with the bandwidth still fairly wide, so I can hear what's around me, seems to prevent ear fatigue too.
__________________
Adapt, Improvise, Oh Bother.....

G-QRP ~ 14233

Last edited by Tyso_Bl; 17th May 2020 at 3:15 pm. Reason: Tipo
Tyso_Bl is offline   Reply With Quote
Old 17th May 2020, 3:01 pm   #7
toshiba tony
Heptode
 
toshiba tony's Avatar
 
Join Date: May 2006
Location: Accrington, Lancashire, UK.
Posts: 680
Default Re: Morse Pitch

Exc. and thank you all of you, now I was one Sony's whizzkids in the 70\80s and I was rarely flummaxed (spell checker refused it) Must be a Yorkshire thing. But perfectly explained.
toshiba tony is offline   Reply With Quote
Old 17th May 2020, 3:58 pm   #8
Colinaps
Pentode
 
Colinaps's Avatar
 
Join Date: Jul 2009
Location: Roxburghshire, UK.
Posts: 167
Default Re: Morse Pitch

Some spark transmitters had an arc sustained by a spinning commutator. They must have generated a modulated tone - to any receiver capable of demodulating it..

73,

Colin.
Colinaps is offline   Reply With Quote
Old 17th May 2020, 4:06 pm   #9
Jon_G4MDC
Heptode
 
Jon_G4MDC's Avatar
 
Join Date: Nov 2015
Location: Welwyn Garden City, Hertfordshire, UK.
Posts: 884
Default Re: Morse Pitch

Flummoxed should be accepted.
Jon_G4MDC is offline   Reply With Quote
Old 19th May 2020, 2:03 pm   #10
rambo1152
Octode
 
rambo1152's Avatar
 
Join Date: May 2010
Location: Manchester, UK.
Posts: 1,853
Default Re: Morse Pitch

Quote:
Originally Posted by Colinaps View Post
Some spark transmitters had an arc sustained by a spinning commutator. They must have generated a modulated tone - to any receiver capable of demodulating it..

73,

Colin.
ICW (Interrupted Continuous Wave).
Also called "Tonic Train", you see that expression in some early wireless telegraphy legislation. Think about "tonic" in musical rather than a pharmaceutical terms, and it makes more sense.

I see Google is swamped with a couple of radio hams, an electronic music ensemble called Tonic Train. last time I researched it there were only a few hits.
__________________
--
Graham.
G3ZVT
rambo1152 is online now   Reply With Quote
Old 19th May 2020, 2:21 pm   #11
rambo1152
Octode
 
rambo1152's Avatar
 
Join Date: May 2010
Location: Manchester, UK.
Posts: 1,853
Default Re: Morse Pitch

Quote:
Originally Posted by Tyso_Bl View Post
So, do you have a preferred pitch? Mine is around 400 / 500Hz, but with the bandwidth still fairly wide, so I can hear what's around me, seems to prevent ear fatigue too.
I used to listen with a 900Hz beat, not because of a particular preference, but because the lumped L-C audio filter in my R107 was fixed at that frequency.


Did anyone use a stereo processor like this one on page 674?

https://www.americanradiohistory.com...om-1975-09.pdf

I build it.
__________________
--
Graham.
G3ZVT
rambo1152 is online now   Reply With Quote
Old 19th May 2020, 6:08 pm   #12
dodgy-dxer
Hexode
 
dodgy-dxer's Avatar
 
Join Date: Mar 2008
Location: Newmarket, Suffolk, UK.
Posts: 327
Default Re: Morse Pitch

No but I collected all the parts! G4BJM had made one we used at NFD

A couple of modern rigs (eg TT Orion, Elecraft K3) have this built into them that can be switched in and out

73 Fred
G4BWP
dodgy-dxer is online now   Reply With Quote
Old 19th May 2020, 6:27 pm   #13
Radio Wrangler
Dekatron
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 14,097
Default Re: Morse Pitch

Many toroidal 88mH inductors were removed from long phone lines when digital PCM took over. These went to the amateur world and got turned into many an audio filter.

They were 'build-out' chokes to fix an inconvenient issue of the line inductance/capacitance ratio per unit length being wrong for the impedance they were operated with.

Have a shufti at some of the many articles on using these and a quick sim will tell you the frequency if the article does not. It'll give an idea of the beat tones being chosen.


David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is online now   Reply With Quote
Old 20th May 2020, 3:57 am   #14
CarbonMike
Triode
 
Join Date: Apr 2017
Location: Wellington, New Zealand.
Posts: 23
Default Re: Morse Pitch

I have noticed that as I get older I prefer a lower pitch for reading CW, and yes, a wider filter.
Makes sense I suppose, my ears aren't what they used to be.
CarbonMike is offline   Reply With Quote
Old 20th May 2020, 3:25 pm   #15
G6Tanuki
Dekatron
 
G6Tanuki's Avatar
 
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 8,534
Default Re: Morse Pitch

Though not a CW-type, one now-deceased friend who was seriously into CW would often set his receiver to produce what were some seriously-strange tones.

Like about 300Hz!

His argument was that if you set your BFO so a 'wanted' station produced a 1KHz tone, but there was an interfering station that produced a 0.9KHz tone, you had a bit of a problem, the relative difference between the two tones being small.

Setting the BFO so the 'wanted' station produced a 300Hz tone now meant that the interfering station was producing a 200Hz tone.

The effective difference between the wanted and unwanted tones has therefore been increased rather dramatically!

As to MCW, provision for it was standard on a lot of WWII transmitters/receivers (WS19 for example). It had the advantage that it could be received on a receiver without a BFO (if you were a clandestine operator in occupied territory being caught with a 'communocations' receiver with a BFO would be likely to get you shot without further wuestioning, whereas getting caught with a broadcast-receiver without a BFO might give greater chance for you to talk your way out of the situation). MCW also benefits from the presence of a continuous carrier, so 'traditional' broadcast-receiver AGC works as expected.
G6Tanuki is online now   Reply With Quote
Old 21st May 2020, 12:02 pm   #16
SiriusHardware
Dekatron
 
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 4,055
Default Re: Morse Pitch

Much easier for the enemy to DF, though , I would have thought.
SiriusHardware is online now   Reply With Quote
Old 23rd May 2020, 5:23 am   #17
FrankB
Hexode
 
Join Date: Oct 2005
Location: Olympia, Washington, USA.
Posts: 458
Default Re: Morse Pitch

The tone and the station of a transmitter could be identified by the frequency of the rotary gap transmitter. You could change the tone of the transmitted tone by varying the speed of the motor.
I was told this by my Elmer- W7SS SK, Bill Ward CWO USN.
(He was a Pearl Harbor survivor, WIA there.)
FrankB is offline   Reply With Quote
Old 23rd May 2020, 10:06 pm   #18
Colinaps
Pentode
 
Colinaps's Avatar
 
Join Date: Jul 2009
Location: Roxburghshire, UK.
Posts: 167
Default Re: Morse Pitch

Quote:
Originally Posted by SiriusHardware View Post
Much easier for the enemy to DF, though , I would have thought.
Yes, but that's ok if the transmitter is in another country, probably one of many fed by GPO line according to availability and skip distance.

Colin.
Colinaps is offline   Reply With Quote
Old 26th May 2020, 3:39 pm   #19
Granitehill
Triode
 
Join Date: Mar 2019
Location: York, North Yorkshire, UK.
Posts: 49
Default Re: Morse Pitch

Quote:
Originally Posted by Radio Wrangler View Post
Many toroidal 88mH inductors were removed from long phone lines when digital PCM took over. These went to the amateur world and got turned into many an audio filter.

They were 'build-out' chokes to fix an inconvenient issue of the line inductance/capacitance ratio per unit length being wrong for the impedance they were operated with.

Have a shufti at some of the many articles on using these and a quick sim will tell you the frequency if the article does not. It'll give an idea of the beat tones being chosen.


David
The ones I came across on the job were actually pot cores, rather than toroids. The outer crimped aluminium sheet case formed the clamp holding the two halves together (not glued, in my experience). The winding is in two halves - actually 22+22mH. It's easy to cut off the can and rewind the coils - I don't know the ferrite grade, though.
I suspect the "Toroid" description came from early US-made inductors, and possibly early UK ones also. The pot cores are more recent, I think.
__________________
John G4FDD
G-QRP 431
Granitehill is offline   Reply With Quote
Reply

Thread Tools



All times are GMT +1. The time now is 8:08 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
Copyright ©2002 - 2020, Paul Stenning.