[pskmail] Re: STANAG 4285 legal in the US? (was: Re: Re: Server & Hamlib Question....)
- From: Per Crusefalk <per@xxxxxxxxxxxx>
- To: pskmail@xxxxxxxxxxxxx
- Date: Sun, 30 Sep 2007 17:57:30 +0200
On sön, 2007-09-30 at 18:15 +0300, Demetre Valaris - SV1UY wrote:
> On Sun, 30 Sep 2007 16:23:25 +0200, Per Crusefalk wrote
> >
> > Been thinking about the interesting regulations in the US...
> > I noticed something interesting on this page:
> > http://hflink.com/alehamradiousa/
> >
> > I am refering to this part:
> > "Does the ALE RF Signal Meet the FCC "300 Baud Rule" for Data mode?
> > Yes. The ALE (MIL-STD 188-141B or FED-STD-1045) signal is
> > transmitted at 125 symbols per second. It is legal under FCC Rules
> > for use in the Amateur Radio Service for DATA MODE transmission on
> > HF in the DATA sub-bands. Current FCC Rules in USA allow DATA modes
> > up to 300 baud (300 symbols per second) in HF data subbands. Symbol
> > rate (baud) is the number of state changes the transmitted signal
> > makes per second. The ALE signal is 8FSK (8 Frequency Shift Keyed).
> > 8 discrete tone frequencies are spaced 250 Hz apart from 750 Hz to
> > 2500 Hz at audio baseband. A single tone is being transmitted at any
> > given instant on any one of these 8 frequencies. No more than one
> > tone is transmitted at a time. Each symbol represents three bits of
> > data, resulting in an over-the-air data rate of 375 bits per second
> > (375bps) using "125 baud"."
> >
> > STANAG 4285 & MIL-STD 188-110A use 8-PSK to provide up to 2400 bps (not
> > 8-FSK as in the example). The big issue is if they are correct in
> > thinking that its the baud rate that matters (and not the actual data
> > rate)?
> >
> > 73 de Per, sm0rwo
>
> I think that FCC mentions baud (I bet the ones who wrote the rules haven't a
> clue about the difference of baud and bps, or they wrote it in the dark ages
> when baud and bps was indeed the same).
>
> What I'm not sure is true is the following statement:
>
> "Each symbol represents three bits of data, resulting in an over-the-air
> data rate of 375 bits per second (375bps) using "125 baud"."
>
> It could be an innocent white little lie that they might be using to make
> STANAG 4285 sound legal. I do not really know how STANAG 4285 works exactly
> so I could be wrong here. I hope someone can come forward and explain to all
> of us because STANAG 4285 sounds interesting, although it is not robust
> enough for the ham bands. It is cheap to implement though.
Oh, its very robust. I have been thinking abt writing a beginners course
in 188-110A/4285 but at the moment I am working on insulating the radio
schack and I must finish that first (winter is coming).
Well, I'm not an expert on 8-fsk but I do know how 8-psk works.
If you consider 2-fsk, rtty, there you only have 2 tones available and
can only have them represent 0 or 1. Lets say we improve that and
transmit 4 tones instead, that means the first tone can represent 00,
the second 01, the third 10 and the last tone would mean 11. So, we have
doubled the effective data rate but the baud rate, change rate, is still
the same. Lets say we use 8 tones (8-fsk), then we can have the tones
represent 000, 001, 010, 011, 100, 101, 110 and 111. So, using the same
baud rate we have tripled the effective data rate (125 baud gives
375bps). 8-psk works the same way but changes the phase instead, 300
baud would give 2400 bps.
Its also possible to have two amplitude levels at every phase position,
8-psk is then 16 position qam and the data rate is quadrupled (but the
bandwidth is the same). So, 125 baud can indeed provide 375 bps (500
using 16-QAM, 625 bps using 32-QAM).
73 de Per, sm0rwo
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