UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV 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.

Closed Thread
 
Thread Tools
Old 23rd Jul 2021, 1:54 pm   #21
Terry_VK5TM
Nonode
 
Terry_VK5TM's Avatar
 
Join Date: Oct 2010
Location: Tintinara, South Australia, Australia
Posts: 2,324
Default Re: What is QRP?

Quote:
Originally Posted by DMcMahon View Post
CW I assume is Continuous Wave but in simple terms what is it in terms of radio reception/transmission operation ?

David
CW is Carrier Wave, not Continuos Wave.

Morse is mostly keyed carrier wave i.e. the rf is on and off for the periods of the morse characters and sometimes it is generated by audio tones.

To get the tone you hear on the receive end, the receiver is tuned around 700 or 800Hz off the transmit frequency.
__________________
Terry VK5TM
https://www.vk5tm.com/
Terry_VK5TM is offline  
Old 23rd Jul 2021, 3:09 pm   #22
Station X
Moderator
 
Station X's Avatar
 
Join Date: Jan 2003
Location: Ipswich, Suffolk, IP4, UK.
Posts: 21,192
Default Re: What is QRP?

Or you set the Beat Frequency Oscillator (BFO) 800Hz from the IF Frequency (sic).
__________________
Graham. Forum Moderator

Reach for your meter before you reach for your soldering iron.
Station X is offline  
Old 23rd Jul 2021, 3:12 pm   #23
G6Tanuki
Dekatron
 
G6Tanuki's Avatar
 
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 13,953
Default Re: What is QRP?

Quote:
Originally Posted by Station X View Post
Or you set the Beat Frequency Oscillator (BFO) 800Hz from the IF Frequency (sic).
Yes, with a decent CW filter in the receiver, if you tuned 800Hz off the carrier it would be all but inaudible!
G6Tanuki is offline  
Old 23rd Jul 2021, 3:17 pm   #24
ms660
Dekatron
 
ms660's Avatar
 
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
Default Re: What is QRP?

In some receivers the frequency of the BFO isn't near the IF.

Lawrence.
ms660 is offline  
Old 23rd Jul 2021, 3:21 pm   #25
G6Tanuki
Dekatron
 
G6Tanuki's Avatar
 
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 13,953
Default Re: What is QRP?

Quote:
Originally Posted by ms660 View Post
In some receivers the frequency of the BFO isn't near the IF.

Lawrence.
True: the R1155 BFO was operated at half the IF, and used the second-harmonic.

This reduced the tendency for the BFO frequency to be 'pulled' by the high level IF signal. Quite a cunning trick!
G6Tanuki is offline  
Old 23rd Jul 2021, 3:26 pm   #26
DMcMahon
Dekatron
 
DMcMahon's Avatar
 
Join Date: Apr 2019
Location: Worthing, West Sussex, UK.
Posts: 6,587
Default Re: What is QRP?

Quote:
Originally Posted by Terry_VK5TM View Post
Quote:
Originally Posted by DMcMahon View Post
CW I assume is Continuous Wave but in simple terms what is it in terms of radio reception/transmission operation ?

David
CW is Carrier Wave, not Continuos Wave.
Thank you Terry, that now makes a lot more sense to me.

David
DMcMahon is offline  
Old 23rd Jul 2021, 3:29 pm   #27
ms660
Dekatron
 
ms660's Avatar
 
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
Default Re: What is QRP?

Then there's MCW.

Lawrence.
ms660 is offline  
Old 23rd Jul 2021, 3:40 pm   #28
Station X
Moderator
 
Station X's Avatar
 
Join Date: Jan 2003
Location: Ipswich, Suffolk, IP4, UK.
Posts: 21,192
Default Re: What is QRP?

I believe the BFO in the Codar T28 operated at half IF frequency. The IF frequency was odd too, the set using a retuned Mullard Module.
__________________
Graham. Forum Moderator

Reach for your meter before you reach for your soldering iron.
Station X is offline  
Old 23rd Jul 2021, 4:56 pm   #29
Aub
Nonode
 
Aub's Avatar
 
Join Date: Mar 2005
Location: Nuneaton, Warwickshire, UK.
Posts: 2,034
Default Re: What is QRP?

And for the romantically inclined, 88 is love and kisses 😄. YL is young lady, XYL is the wife. I wonder what ex wife would be - XXYL ?

73

Aub
__________________
Life's a long song, but the tune ends too soon for us all.
Aub is offline  
Old 23rd Jul 2021, 6:10 pm   #30
Graham G3ZVT
Dekatron
 
Graham G3ZVT's Avatar
 
Join Date: May 2010
Location: Greater Manchester, UK.
Posts: 18,676
Default Re: What is QRP?

Quote:
Originally Posted by DMcMahon View Post
Quote:
Originally Posted by Terry_VK5TM View Post
Quote:
Originally Posted by DMcMahon View Post
CW I assume is Continuous Wave but in simple terms what is it in terms of radio reception/transmission operation ?

David
CW is Carrier Wave, not Continuos Wave.

Thank you Terry, that now makes a lot more sense to me.

David
I think your first guess was right David, it was always "Continuous Wave" in the old books I read. A strange choice to mean Morse, as no information is sent unless you key it then it ceases to be continuous.

It's the same with "Single Sideband" as that term completely ignores the fact that the carrier is suppressed which arguably is the attribute that sets it apart.
__________________
--
Graham.
G3ZVT
Graham G3ZVT is offline  
Old 23rd Jul 2021, 6:13 pm   #31
Radio Wrangler
Moderator
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,801
Default Re: What is QRP?

Quote:
Originally Posted by ms660 View Post
In some receivers the frequency of the BFO isn't near the IF.
Lawrence.
Indeed!

You want the incoming signal to go right down the middle of the IF passband in order to get he best sensitivity and the best rejection of other frequencies.

THEN you want the BFO (or its second harmonic) to be offset from the IF centre by an amount equal to the audio tone you wish to hear the signal as. Different people have different hearing and different preferences, which is one of the reasons for a BFO control (the other one is that on early sets it would have been too costly to try to make it all accurate enough to be fixed)

With modern synthesised sets of high accuracy in frequency control, you get the fun of defining what frequency the display should show when demodulating SSB

With CW you also have the difference between IF centre and zero beat frequency.

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is offline  
Old 23rd Jul 2021, 6:18 pm   #32
ms660
Dekatron
 
ms660's Avatar
 
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
Default Re: What is QRP?

Quote:
Originally Posted by Radio Wrangler View Post
Quote:
Originally Posted by ms660 View Post
In some receivers the frequency of the BFO isn't near the IF.
Lawrence.
Indeed!

You want the incoming signal to go right down the middle of the IF passband in order to get he best sensitivity and the best rejection of other frequencies.

THEN you want the BFO (or its second harmonic) to be offset from the IF centre by an amount equal to the audio tone you wish to hear the signal as. Different people have different hearing and different preferences, which is one of the reasons for a BFO control (the other one is that on early sets it would have been too costly to try to make it all accurate enough to be fixed)

With modern synthesised sets of high accuracy in frequency control, you get the fun of defining what frequency the display should show when demodulating SSB

With CW you also have the difference between IF centre and zero beat frequency.

David
I should have said nowhere near the IF as in hundreds of kHz away like it was in my R1155.

Lawrence.
ms660 is offline  
Old 23rd Jul 2021, 6:22 pm   #33
ms660
Dekatron
 
ms660's Avatar
 
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
Default Re: What is QRP?

Quote:
Originally Posted by Aub View Post
And for the romantically inclined, 88 is love and kisses ��. YL is young lady, XYL is the wife. I wonder what ex wife would be - XXYL ?
If it's a divorce job I would say TSB, which is nothing to do with a well known Bank.

Lawrence.
ms660 is offline  
Old 23rd Jul 2021, 8:55 pm   #34
wireless_john
Heptode
 
wireless_john's Avatar
 
Join Date: Apr 2011
Location: Gosport, Hampshire, UK.
Posts: 597
Default Re: What is QRP?

The military in my time used Z Codes and when it was a question, it was preceded by INT.

So INT ZBA meant 'What is the delay'. I only ever used them on teleprinters but the radio operators used them with Morse code as well.

Sometimes it took so long to work out what was being said that it may as well just have been sent in English!

John
__________________
GQRP Club 4704 - BVWS Member
wireless_john is offline  
Old 23rd Jul 2021, 9:17 pm   #35
G6Tanuki
Dekatron
 
G6Tanuki's Avatar
 
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 13,953
Default Re: What is QRP?

One QRP technique that always fascinated me but alas never caught on was 'coherent CW' - an interesting blend of human and 'digital'.

In essence the idea was to use a clock-signal synchronised between the sender and receiver, but locked to the speed of the [manually generated] CW: this clock was used to only unsquelch the receiver when there was a possibility of a 'dot' [or three dots - a dash] having been sent.

See

https://midnightdesignsolutions.com/ccw/

and

http://www.arrl.org/weak-signal-modes

Philosophically, I don't see that there's much difference between using a valve/semiconductor amplifier or maths-and-a-computer to improve your weak-signal/low-power communications-efficiency.

Last edited by G6Tanuki; 23rd Jul 2021 at 9:31 pm.
G6Tanuki is offline  
Old 23rd Jul 2021, 9:42 pm   #36
Ian - G4JQT
Octode
 
Ian - G4JQT's Avatar
 
Join Date: Jun 2004
Location: Reading/Fakenham, UK.
Posts: 1,320
Default Re: What is QRP?

Quote:
Originally Posted by G6Tanuki View Post
One QRP technique that always fascinated me but alas never caught on was 'coherent CW' - an interesting blend of human and 'digital'.

In essence the idea was to use a clock-signal synchronised between the sender and receiver, but locked to the speed of the [manually generated] CW: this clock was used to only unsquelch the receiver when there was a possibility of a 'dot' [or three dots - a dash] having been sent.

See

https://midnightdesignsolutions.com/ccw/

and

http://www.arrl.org/weak-signal-modes

Philosophically, I don't see that there's much difference between using a valve/semiconductor amplifier or maths-and-a-computer to improve your weak-signal/low-power communications-efficiency.
Drifting off topic, but QRSS (QRS, send more slowly, with an extra S for VERY slowly - 3 second dots are typical) has I think has superseded CCW. Commonly only 200mW or less is used and the PC sound card pulls the signal out of the noise. (QRSS is not an official Q-code, but most amateurs know what it means.)

My 10140 kHz QRSS 200mW into a bit of wet string has been spotted as far as Alaska and New Zealand. It's also a great mode to actually clearly see weird stuff on the traces like aircraft reflection, aurora and meteor pings.
Ian - G4JQT is offline  
Old 24th Jul 2021, 12:32 am   #37
Terry_VK5TM
Nonode
 
Terry_VK5TM's Avatar
 
Join Date: Oct 2010
Location: Tintinara, South Australia, Australia
Posts: 2,324
Default Re: What is QRP?

Quote:
Originally Posted by G6Tanuki View Post
Quote:
Originally Posted by Station X View Post
Or you set the Beat Frequency Oscillator (BFO) 800Hz from the IF Frequency (sic).
Yes, with a decent CW filter in the receiver, if you tuned 800Hz off the carrier it would be all but inaudible!
True, but 'in the very beginning' - in my explanation above, I was keeping it as it was originally done before all the good stuff like narrow filters and BFO's etc arrived.
__________________
Terry VK5TM
https://www.vk5tm.com/
Terry_VK5TM is offline  
Old 24th Jul 2021, 3:32 am   #38
Graham G3ZVT
Dekatron
 
Graham G3ZVT's Avatar
 
Join Date: May 2010
Location: Greater Manchester, UK.
Posts: 18,676
Default Re: What is QRP?

Quote:
Originally Posted by wireless_john View Post
The military in my time used Z Codes and when it was a question, it was preceded by INT.
INTerrogative
The American military liked to use "Interrogative" when using fone.
__________________
--
Graham.
G3ZVT
Graham G3ZVT is offline  
Old 24th Jul 2021, 5:28 am   #39
Radio Wrangler
Moderator
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,801
Default Re: What is QRP?

Quote:
Originally Posted by G6Tanuki View Post
In essence the idea was to use a clock-signal synchronised between the sender and receiver, but locked to the speed of the [manually generated] CW: this clock was used to only unsquelch the receiver when there was a possibility of a 'dot' [or three dots - a dash] having been sent.
Not quite. The receiver has to handle the propagation delay from transmitter to receiver, along with slight disagreement in the settings of local clocks. The clocks have to run in reasonable synchronism, but there may easily be differences in absolute time.

So what's needed for best reception is a cross-correlator looking for dot and dash period pulses as well as for the appropriate space lengths (there is information content in the space lengths and they reinforce the recognition of the pulse periods.

An auto-correlator can be used on ordinary CW, but a cross-correlator offers advantages.

So the receiving station and the transmitting station need access to high stability frequency references. Short of having a rubidium or caesium standard handy, GPS derived frequency standards were just coming available as CCW was getting interesting.

From a communications engineering point of view, Morse sent in A1A at a very regular speed has a comb-like spectrum, and a timing-synchronised receiver can be made to have a comb-like filter characteristic matched to it. A correlator acts as a bank of time-offset filters and tells you which offset best fits the signal. In the end, with the receiver closely matched to the signal, the receiver bandwidth is just enough for the information rate of the message content. Matched filtering is fascinating.

Random jitter in the propagation delay, especially with ionospheric propagation modes becomes a limitation, spreading the comb components and requiring less optimal RX bandwidth.

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is offline  
Old 24th Jul 2021, 5:29 pm   #40
Keith
Heptode
 
Keith's Avatar
 
Join Date: Jan 2003
Location: Tewkesbury, Gloucestershire, UK.
Posts: 690
Default Re: What is QRP?

Quote:
Originally Posted by G6Tanuki View Post
Philosophically, I don't see that there's much difference between using a valve/semiconductor amplifier or maths-and-a-computer to improve your weak-signal/low-power communications-efficiency.

I think the difference is a few billion transistors - 2.6 billion in an Intel I7 alone!
__________________
Keith Yates - G3XGW
VMARS & BVWS member http://www.tibblestone.com/oldradios/Old_Radios.htm
Keith is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 6:20 am.


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 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.