Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: Prev 1 2 [3]   Go Down
  Print  
Author Topic: Use of Computer Generated CW  (Read 2790 times)
WQ3T
Member

Posts: 209




Ignore
« Reply #30 on: January 29, 2008, 06:35:15 AM »

Computer CW is a great way to go, especially for an experienced operator. Learn to head copy CW and touch type, you've got a great combination. It's great to see the other op's CW speed, then dial it in for sending perfect CW at the exact same speed the other guy is working. Experienced ops tend to merge words es chars together while using paddles at slow speed. The keyboard sends it just fine at any speed. Experienced ops have a hard time copying at slow speed because the words are formed too slowly to head copy. The computer copies slow and fast CW the same way. New ops should continue to use CW the old fashioned way, at least until they have all the letters memorized. I am stressing the computer should be used as an aid, not a crutch. My range of people I can work CW has increased dramatically for both QRS es QRQ operators, using the computer and keyboard. Before spending all that money on an expensive set of paddles, try sending CW with that $10 keyboard already on your desktop. And I do agree, with soundcard CW adjusted properly, there are no key clicks as there may be with the CW key jack.
Logged
N8UZE
Member

Posts: 1524




Ignore
« Reply #31 on: January 29, 2008, 06:42:46 AM »

Also keep in mind that many of the CW generating programs actually key the radio directly by an interface between the serial port and the straight key jack on the radio and then you do not need to worry about the quality of the sound card and/or generated tone.
Logged
WQ3T
Member

Posts: 209




Ignore
« Reply #32 on: January 29, 2008, 07:38:01 AM »

Keying the rig with the CW jack via serial port is a great way to go for full break-in, and perfect for contest use. I will be making several cables for our club to use during contests. This method keeps hands on the keyboard, sidetone at normal frequencies of 800Hz instead of 1500HZ when you send CW via soundcard. I have heard of slight delays when keying via serial port CW jack, where the soundcard keying method is at audio levels with no keying delays. My old windows 98 computer sometimes has trouble sending CW at high speed when running other programs though.
Logged
WA0LYK
Member

Posts: 85




Ignore
« Reply #33 on: January 29, 2008, 08:15:50 AM »

W3LK

I yield. I was taught wrong all these years.

73,

Lon - W3LK
Naugatuck, Connecticut

====================================================

Don't be buffaloed so easily!  You are correct and the others are wrong.

AA4PB says: "The Collins KWM-2 generated CW by applying
an audio tone to the SSB transmitter audio input stage.
The KWM-2 was used by hams and military world wide for
many years.

Here's a quote from THE RADIO HANDBOOK by Bill Orr,
W6SAI, page 5-1: "A single audio tone in a perfect ssb
system remains a sine wave at all points in the system
and cannot be distinguished from a cw signal generated
by more conventional means"."

You'll note the word PERFECT in the quote from Bill ORR.  What does this mean?  Infinite carrier and opposite sideband suppression and zero intermod products!  I would agree that with perfect carrier and opposite sideband suppression and zero intermod products that you can not distinguish an audio cw tone versus a carrier keyed on/off.  However, we don't live in a perfect world.  

Also you'll note Bill Orr said can not distinguish between the two.  This ISN'T the same as saying they are same.

Let's look at the emission designators for the two.  A keyed carrier has a designator of A1A.  For all practical purposes, J1A is useless, therefore what we are talking about is J2A.  This is what the KWM-2 used.

What does A1A mean.  For one thing the "1" means that a modulating sub-carrier is not used.  The first "A" also means double sideband, which a keyed carrier is.  You DO get sidebands at the keying frequency on both sides of the carrier.  You can see these on a spectrum analyzer.

What does J2A mean.  The "2" means that a modulating sub-carrier is used.  This is the tone that is injected into the audio chain.  Do you get "sidebands" around the injected tone equal to the keying frequency.  You bet!  Is this considered a double sideband transmission?  No!  On a spectrum analyzer you can also see the carrier frequency, the opposite sideband, and intermod products, albeit at a low level hopefully.

What does all this mean?  In order to have "good amateur practice" you must understand the difference between the two types of emissions and the problems that can occur.

With A1A there isn't much to go wrong other than key clicks, chirp, and hum.  With J2A, there is a lot of things that can go wrong.  Clicks, chirp, hum, poor carrier suppression, poor opposite sideband suppression, and intermod products.  One needs to know these differences and why they occur in order to properly operate a transmitter on the amateur bands.

One perfect example is running both signals into an amplifier.  What kind of signal gets put out on the air?  I'll guarantee the A1A signal will be cleaner and cause less interference than the J2A emission.  Do folks running J2A reduce their drive until they see no ALC?  If they don't, their signal will look like an overdriven psk31 signal.

Remember, even a milliwatt signal can cause interference under the right conditions.  Does your rig have sufficient carrier and sideband suppression to insure these emissions don't cause interference when conditions are great, especially when running an amplifier?  

If you read the rules, both A1A and J2A are legal cw signals.  However, they are generated differently and have different on the air characteristics.  To say they look the same on a spectrum analyzer is only true if you aren't looking closely.

Jim
WA0LYK
Logged
KG6AF
Member

Posts: 334




Ignore
« Reply #34 on: January 29, 2008, 09:54:43 AM »

WA0LYK writes: "With A1A there isn't much to go wrong other than key clicks, chirp, and hum."

I can assure you, generations of hams have found these defects sufficient to generate truly horrible CW signals.
Logged
AA4PB
Member

Posts: 12669




Ignore
« Reply #35 on: January 29, 2008, 10:40:43 AM »

The original question was is sound card generated CW really MCW and therefore illegal to use on the HF bands. It is CW, not MCW and it is not illegal provided your signal is clean and you don't have poor unwanted sideband or carrier suppression.

It is true that such a method can be difficult to keep clean and I personally would rather use a serial or parallel port control signal to key the radio in its CW mode (plus that allows you to use narrow receive filters in the radio).
Logged
AA4PB
Member

Posts: 12669




Ignore
« Reply #36 on: January 29, 2008, 10:50:52 AM »

If you really want to nit pick I guess you could say that SSB is not really SSB because if you look at the spectrum analyzer close enough you can see that the suppressed carrier and oposite sideband really are present. Does that mean that SSB is really DSB AM?
Logged
WQ3T
Member

Posts: 209




Ignore
« Reply #37 on: January 29, 2008, 12:04:12 PM »

About the narrow filter thing, using an ICOM rig in digtal mode, that is, holding in the SSB button until a "D" appears on the screen, you can narrow the filter down to 50Hz. The computer likes to copy with a much narrower filter than I can use. My ears like a 300-300Hz filter, but the computer can go down to 100Hz and still copy CW just fine. The only thing is, in digital mode, the filters center on 1500Hz. I will need to switch to serial port keyed CW before my ears lose the ability to hear 1500Hz. As long as the drive isn't distorting the signal, there is no problem sending CW with a tone on SSB mode. CW means continuous wave; however this is done, it should be okay.
Logged
WA0LYK
Member

Posts: 85




Ignore
« Reply #38 on: January 29, 2008, 12:47:11 PM »

AA4PB on January 29, 2008:
If you really want to nit pick I guess you could say that SSB is not really SSB because if you look at the spectrum analyzer close enough you can see that the suppressed carrier and oposite sideband really are present. Does that mean that SSB is really DSB AM?

========================================================

Actually, it is not even nit picking.  In a filter type transmitter, short the input and output of the filter and you'll get DSB, suppressed carrier every time, guaranteed!  Unbalance the balanced modulator and you'll get DSB, AM every time, guaranteed!

The carrier is still there, even though it is suppressed.  The opposite sideband is still there even though it is suppressed.  So all ssb signals start life as a DSB, AM signal.  Only through the use of either components or mathematical algorithms in a dsp is the opposite sideband and carrier suppressed.  I guess suppressed is the operative word.

Jim
WA0LYK

Logged
WA0LYK
Member

Posts: 85




Ignore
« Reply #39 on: January 29, 2008, 12:53:11 PM »

WQ3T on January 29, 2008:
About the narrow filter thing, using an ICOM rig in digtal mode, that is, holding in the SSB button until a "D" appears on the screen, you can narrow the filter down to 50Hz.

=======================================================

Not all of us have newer rigs that can do this.  My old Icom 761 needs to be in CW mode in order to use the narrow filters during receive.  However, my homebrew rcvr does not.  But, using 500 Hz on phone makes it tough with that rig, hi hi.  Maybe I'll get around and build up a couple more homebrew crystal filters.

Jim
WA0LYK
Logged
AA4PB
Member

Posts: 12669




Ignore
« Reply #40 on: January 29, 2008, 04:54:27 PM »

I guess my point is that once the carrier and unwanted sideband are supresses below a certain point (30dB below the peak output??) then they are considered to be non-existant and the mode is Single Sideband, Supressed Carrier. By logic I would say that the same applies to audio generated CW. As long as the unwanted sideband, suppressed carrier, and other unwanted signals are below that level then the mode is considered CW rather than MCW. Once the signal is down to a reasonable strength then these other signals are for all practical purposes non-existant.

I think the differentiating thing about MCW is that it requires a carrier (such as in AM or FM) so that you can copy the tones by ear without the use of a BFO in the receiver. I suspect the FCC doesn't allow its use below 6M (with a few exceptions) because MCW is not a narrow bandwidth mode like CW.
Logged
WA0LYK
Member

Posts: 85




Ignore
« Reply #41 on: January 29, 2008, 06:02:02 PM »

I agree that mcw would have a much wider bandwidth than a cw signal.  Even if you used a 500 Hz tone, it would be at least 500 Hz wide with a single sideband, and twice that with both sidebands.

As to carrier suppression and opposite sideband suppression do you ever listen around the band in am mode or on the opposite sideband.  You would be surprised at the number of rigs that aren't clean either through operator error or malfunctions.

Jim
WA0LYK
Logged
WQ3T
Member

Posts: 209




Ignore
« Reply #42 on: February 07, 2008, 07:14:02 AM »

Look into the Winkey USB CW interface. It sends perfect CW the way your rig was meant to send CW. You can still copy code with the sound card interface.
http://k1el.tripod.com/wk2info.html
Logged
KF6IIU
Member

Posts: 293




Ignore
« Reply #43 on: February 14, 2008, 03:16:35 PM »

Well, the proof is in the practice. There are a lot of 200 Hz wide PSK31 signals from ops who either don't know how or don't care to produce a clean signal.

If you send sound card CW and your signal is 200Hz wide you're definitely gonna hear about it!
Logged
Pages: Prev 1 2 [3]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!