Let's say I get my little 2 meter FM handheld out and make a little sine-wave generator with which I pulse a morse code and if I connect it to headphones a speaker, I hear the dits and dahs of a nice sine wave tone. Now let's say I connect this to the microphone port on my transceiver with the VOX setting turned to detect when I am entering the morse.

Is this allowed, or is it illegal because of the wasted bandwidth when I could just use carrier?

My country is the USA.

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    $\begingroup$ When asking whether something is legal, please specify the locale. Regulations differ wildly by country and an activity that is allowed in one locale may be illegal in another. $\endgroup$
    – user
    Commented Oct 26, 2013 at 15:15

2 Answers 2


Completely legal. In fact, it's common practice to identify repeaters (both in the amateur service and in public safety/commercial) with exactly this method.

That said, you likely won't make many QSOs with it. There aren't many people who would be prepared to immediately respond if they started hearing FM morse on 146.52 (the typical hailing frequency for simplex operators on the 2m band), compared to people down in the CW section of the band.

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    $\begingroup$ It would be helpful (when citing frequencies) to clarify the location. For example, here in the UK, 146.xxMHz is out of band!! $\endgroup$ Commented Oct 26, 2013 at 6:04
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    $\begingroup$ @AndrewM6ADB It would be helpful if questions asking whether something is legal would clarify the location, IMO. $\endgroup$
    – user
    Commented Oct 26, 2013 at 15:14

tl;dr: It's legal on any VHF or above frequency where phone modes are permitted. It is not allowed on HF or below, nor where phone modes are not allowed.

What you have described is called "Modulated Continuous Wave" (MCW), as defined in the US amateur radio rules under 47 CFR §97.3(c)(4), and would have the emission designator F2A. (The usual CW used on HF has emission designator A1A.) In areas regulated by the FCC, it is not legal on frequencies below 50.1 MHz, between 144.0 and 144.1 MHz, or between 219 and 220 MHz. It is legal on any other amateur frequency.

MCW is commonly used for automated identification of FM voice repeaters.

It is worth noting that some software capable of transmitting the many HF digital modes via an SSB transceiver can also generate CW in the same fashion. When transmitted this way through an SSB transceiver, it is technically emission designator J2A, which is still within the definition of proper CW. In areas regulated by the FCC, proper CW is legal on any frequency allocated to the amateur service (subject to certain limitations on the 60m band).


  • $\begingroup$ Can you clarify that last bit about MCW-over-SSB being ‘proper CW?’ Are you saying N-kHz-deviation SSB is legal on the CW-only bands if it's encoding morse, that is, MCW!? Really? $\endgroup$ Commented Nov 9, 2016 at 20:21
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    $\begingroup$ The transmitted signal on SSB only exhibits deviation of the actual bandwidth of the audio input, up to the filtering in the transmitter. Microphone-captured audio, typically containing human speech, will usually exhibit, give or take, the full signal width. But if your input audio is 600-Hz tone, the only actual signal that is leaving the transmitter is that tone, shifted up 600 Hz from the suppressed carrier. This is, essentially, how digital modes work (eg, PSK31 or AFSK). Regardless of the 2.7kHz SSB bandwidth, SSB modulation only carries the actual audio data, at its own width. $\endgroup$
    – James NF8I
    Commented Dec 5, 2016 at 3:46
  • $\begingroup$ @ELLIOTTCABLE what comes out of the radio (so long as everything is tuned up properly) isn't MCW, it's CW. And "deviation" isn't really a proper term to use in relation to SSB. MCW applies to A2A and F2A. $\endgroup$ Commented May 31, 2018 at 0:57

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