Ham Radio - Modulated CW with FLdigi, not A2A. How it works, and is it wider than regular CW?

Ham Radio - Modulated CW with FLdigi, not A2A. How it works, and is it wider than regular CW?

 

Unfortunately MCW (Modulated CW) is only permitted on VHF, UHF, and SHF. Part 97 FCC rules say it's not allowed on the HF bands in the U.S. See 47CFR §97.305 Authorized emission types + any notes specified in the right margin beside of each band in the tables in 97.305, then refer to 97.307 Emission standards to interpret the notes. What KB9RLW is doing is illegal according to Part 97 FCC rules & regulations since he's transmitting MCW on the 20 meter HF band. That's what I interpret from reading the rules anyway. Please correct me if I'm mistaken and if so tell or show me how. Just trying to play it safe! http://www.arrl.org/part-97-text

 

Just because you can, doesn't mean you should.

 

It's unfortunate that in the video the presenter used the term "modulated CW", which is incorrect. An audio tone inserted into an SSB transmitter produces regular CW, by definition. Modulated CW is where an AM or FM transmitter is fed an audio morse code stream. It produces a carrier and sidebands, which is much wider than regular CW.

From the definition of CW in part 97:

(1) CW. International Morse code telegraphy
emissions having designators
with A, C, H, J or R as the first symbol;
1 as the second symbol; A or B as the
third symbol; and emissions J2A and
J2B.

FLDIGI produces J2B when attached to an SSB transmitter. If you took a code practice oscillator with a key attached, and fed that into an SSB transmitter, you would have J2A. Both of those are defined as CW, and are the same, for all practical purposes.

 

@K7JEM is quite correct - there is certainly nothing wrong with using a tone to modulate an SSB transmitter to produce CW. In fact, this method has some advantages if done properly, because the modulating wave shape can be very precisely controlled to minimize key clicks, etc. To emit a clean signal, one does need to be careful not to overdrive the transmitter audio stages, avoid compressors, etc.

If you want to operate CW from fldigi, there is a simpler way to do so that is almost certainly guaranteed to be cleaner for most newer radios. The fldigi manual describes a simple circuit that allows the sound card to hard-key the CW input of your transmitter. I updated this circuit to use more current parts, but either way, using a keying circuit allows one to use one's radio in the dedicated "CW" mode, which lets you use CW-specific filters and features, while still using fldigi for both transmission and reception.

If you use a radio that has a dedicated hard-key input for RTTY, this circuit can be used for RTTY, too. Just like with CW, this has the benefit of allowing you to use the dedicated RTTY features of your radio, like special RX filters, etc.

 

and my HT (non HF version of course) is:
http://www.whiskeytangohotel.com/2019/05/hamradio-ht-turns-cw-morse-transceiver.html

 

I think he is running 0.5 watts into a dummyload.

 

I also agree with K7JEM. If you're on frequency with another station sending CW over SSB using an audio tone (from FLDigi in this case,) you would never know the difference. There is no carrier being sent, just the audio signal which you can zero beat like any other CW station.

I was experimenting with this back in 2012 when I used to run PSK31 with FLDigi. I decided to try the CW mode through the sound card interface.

When set up PROPERLY (not triggering ALC whatsoever,) I could drive the radio from QRPp levels to full power output by simply keeping radio set to full power output and varying the audio input through the sound card interface. And the reports of my CW "note" were outstanding since, as KK5YJ mentions, "the modulating wave shape can be very precisely controlled to minimize key clicks, etc." And if you listen to the CW audio coming from FLDigi, it sounds just great.

The only problem I have with typing CW is that I just can't seem to type as fast as I can key LOL!

 

Thanks for the info Joe!

Very 73 & Happy Thanksgiving!

 

why not just learn cw and use a key if you need a computer to run cw mmm something not right about that

 

It is my understanding that keying a pure tone into the SSB circuit is exactly how Elecraft produces their CW signal on the K3 rigs. (I assume also on the newer rigs but that's just an assumption.) As noted by a few people above, it allows an improved contour of the signal.

Besides, what is the real difference between mixing a 5.1 MHz signal with a 9.0 MHz VFO or a 14.1 signal with a 600 Hz signal? Nothing as far as I can see.

 

The hazard is if the newby misunderstands the difference, uses AM or FM mode (with carrier), and modulates that. Then, the bandwidth will be too wide (legally) for the CW portion of each band.

THAT'S true MCW at least in the military WWII sense.

It's probably okay in the phone portion, because it is phone. It's probably okay as long as it fits in allocated bandwidth and mode requirements, e.g. FM starting at the top of 10 meters and above; AM's okay in any wide-enough phone band with appropriate license level.

It's probably better to stick with the rules and reg's mentioned previously, however.

On 75 meters you'd be slapping a hornet's nest, so why do it?

As a purist CW op, I'd use the VOX circuit in the FLdigi manual to key the transmitter instead, or use an app that keys the transmitter through the RS-232/COM port or USB port. It's on-off circuit grounding instead of BEEP-BEEP tone output.

Modulation of the SSB signal produces an ambiguity in center frequency, because the output of the rig is a combo of the dial setting(s), menu settings (carrier insertion point, Hz), and tone modulation frequencies.

I'm just too lazy to use the (easy) math involved. Two-bit (on/off) keying is much simpler.

 

Please explain.

 

I have done it in the past and I darn well knew CW: I cannot send manually at 35 to 40 wpm. So when I broke the barrier (29 wpm printing) and started copying in my head, I did use a TNC and keyboard for sending. In my experience, CW takes on a totally new feeling at those speeds and becomes more like a regular conversation.

I know there are folks who can send 40-60 wpm with a bug or keyer, but I'm not one of them.

 

This isn't MCW. This method has been widely used since forever (legally). As with the Collins KWM-2.