Permitted power use on digital modes

[VK4REX]

As a result of the recent discussion about the LCD remake, I was asked by another amateur to explain the terms Px and Py and what they meant for digital modes.

I found a simple but easy to read chart from the WIA that put it into terms of 2 syllables.

Basically for ALL digital modes it's 120 watts for an advanced license and 30 watts for a standard license.

Hope this helps others that may be wondering.

Rex

[VK4WDM]

All Digital Modes 1 Primary Amateur Allocations between 3.5 and 30 MHz only.

Some comments:

AR is a secondary service in the 630 and 30 meter bands. One could read from this statement that other power limits are applicable to those bands, or more extreme that digital modes cannot be used in those bands.

Digital modes are also widely used in VHF. Is there a separate table or should we assume that the same limits apply?

This might be missing something obvious.

73

Wayne VK4WDM

[VK4REX]

As I read it this applies to all frequencies. Your comment relates to point 2 which is applicable for the high power permit that was cancelled due to lack of compliance issues.

Rex

[VK3ALB]

There are currently two limitations for the 2200m and 630m bands.

1. Necessary bandwidth of no more than 2.1kHz - See LCD p28

and

2. 1W pX EIRP for 2200m and 5W pX EIRP for 630m - See LCD p17

30m has no extra or special restrictions in this regard.

[VK3DXE]

And AGAIN I'll say it. It's time we came into line with the rest of the world and did away with the archaic 120w Py power level.

[VK8VTX]

now this is interesting, i have been (and will continue) running 100 watts on "SSB" SSTV ever since standards could use sstv.
it was always my understanding that it's 100 watts ssb regardless of mode and 30 watts max on AM/FM regardless of mode?

why is it not that simple????

another point. when i first got novice in 1996, the first thing and another station did was to do SSTV on 10m.
we did that for about a month before some fullcall came along and said that novice could not do that mode
because it's an ANALOG mode (i for get it's emission designator) but the point i am getting to here is that
in this text this pdf text puts it in the "digital" modes.................so what is it?

also i recall when PSK31 came out, it too was NOT digital mode, but now is?


Joe

VK8VTX

[VK3AUU]

And AGAIN I'll say it. It's time we came into line with the rest of the world and did away with the archaic 120w Py power level.

I agree, but until the LCD is changed, 120 watts for digital and CW is all we are allowed.
David

[VK5ZLR]

Soooo, what the is PEP limit when running a digital mode on SSB ?

[VK3AUU]

Soooo, what the is PEP limit when running a digital mode on SSB ?

!20 watts peak as per LCD
The fact that you are running an SSB transmitter is immaterial.

David

[VK4ADM]

There appears to be a misunderstanding of the term PY by some.
PY refers to the mean or average power output under modulation and normal operating conditions, the chart Rex has supplied clearly shows what pY is allowed for the different classes of license.

Daryl.

[VK4REX]

David you are correct.

If you look at FSK441 for example it is a series of individual tones as per cw transmissions on a slightly frequency one at a time.

Same with P25 it is a series of 4 FSK tones but again only one at a time hence the same as a cw transmission.

This is how they all get lumped together under digital and this I think is the reason I was asked the question initially. The ham who asked was totally confused as to why the different modes were all lumped together and why only SSB attracted the 400 watt power level.

Do I agree - NO - but it's what we have to live with as the LCD is our bible.

[VK2AVR]

Soooo, what the is PEP limit when running a digital mode on SSB ?

Amateur LCD
emission modes

Transmitter output power
(1) Subject to sections 15 and 15C, the licensee must not operate an amateur
advanced station, using a transmitter output power of more than 400 watts
pX, if the emission mode of the station includes:
(a) C3F; or
(b) J3E; or
(c) R3E.
Federal Register of Legislative Instruments F2013C00061
Part 3 Conditions for amateur licence (amateur advanced station)
Section 16
18 Radiocommunications Licence Conditions (Amateur
Licence) Determination No. 1 of 1997
(2) Subject to sections 15 and 15C, the licensee must not operate an amateur
advanced station, with an emission mode not mentioned in subsection (1),
using a transmitter output power of more than 120 watts pY.

C3F is amateur TV. J3E is SSB analog voice. R3E is SSB voice but with reduced (as opposed to suppressed) carrier.

ANY other mode is 120 watts average. So if you are modulating your radio with a digital mode on SSB you are no longer modulating your radio with voice.

Pretty simple really!

[VK3AUU]

!20 watts peak as per LCD
The fact that you are running an SSB transmitter is immaterial. /quote]

David

I was slightly wrong. It says 120 watts Py which is average power. For modes such as FSK441 and JT65 the average power is also the peak power if anyone wishes to argue semantics.

David

[VK7XX]

Out of simple curiosity and because I am confused, and others know more about this than myself, I ask.........

If I use my computer to generate a voice (lets say recordings of my own voice) and play that voice through my computers speaker in to my radio microphone which I have placed near the speaker and then use this "voice" to assist me when calling CQ in contests and to give out reports, on SSB, what mode is that ??

If I then pick up the microphone and instead of using the computer generated voice, use my own, is this a different mode ??

If I then use my computer to generate a series of tones for example PSK tones, or even tones for morse code (audio generated morse code, not CW), and I again have these tones come out of my computer speaker and again put my radio on ssb and the microphone near the speaker and key up the radio to transmit these tones, what mode is that ??

If I directly connect my computers audio output to my radio so that I bypass the speaker/microphone setup, have I changed the 'mode' of transmission ??

yours curiously
John

And added by edit...
To clarify one of my questions in my post above,....... CW is not a mode of communication, it is the method by which that mode, 'morse code', is usually transmitted, eg Continuous Wave. My question is in regard to sending morse code via sounds generated on a computer through a microphone via SSB.

[VK3AUU]

It doesn't matter how you generate the signal. If it is voice on SSB it is allowed 400 watts peak, it doesn't matter if the source of the audio is a microphone, the memory in your rig or your computer.
This applies to Advanced calls, not to other "lesser" calls.

On the other hand, if you are transmitting a digital mode, same deal except 120 watts average is your limit. I presume that if there are any digital modes out there that have less than 100 percent duty cycle then you could increase the peak output to get 120 watts average.

It could be reasonably argued that CW, being an intermittent mode which does have a substantially lesser duty cycle falls into this category, but the duty cycle does vary somewhat with the substance of the text being sent.

David

[VK5ZLR]

I presume that if there are any digital modes out there that have less than 100 percent duty cycle then you could increase the peak output to get 120 watts average.

I would agree. Whilst it may be slightly absurd, if one had, say, some kind of pulsed digital signal with a low duty cycle, one could just keep turning the wick up maintaining the 120w average. (Well I couldn't because I don't have anything capable of making significant power, but others could...)

And what about two tone data (eg DTMF) or multi-tone where the peak power well exceeds average power on SSB.

Can't think why all these power levels are not just specified as peak power and remove the ambiguity.

Anyway interesting topic.

[VK2AVR]

It could be reasonably argued that CW, being an intermittent mode which does have a substantially lesser duty cycle falls into this category, but the duty cycle does vary somewhat with the substance of the text being sent.

I believe a realistic duty cycle for CW is 0.4. That covers dits, dahs and the gaps in between. So 120W / 0.4 -> 300W peak.

You see duty cycle in the EMR regulations too. CW is around 0.4, SSB is around 0.2 (without a speech processor).