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Run ROS, Go Directly To Jail (Do Not Collect QSL Card)????
25 February 2010 | by There's been a ruckus over the new ROS digital mode going on in radio amateur blogademia and on radio ramateur reflectors. (Rut-ro!) Apparently ARRL has advised someone that ROS is spread spectrum and therefore is illegal below 222 Mhz in the US. The manual for ROS describes it as "a digital communications software based on a FSK modulation of 144 tones".
Anthony Good, K3NG, is a regular contributor to AmateurRadio.com and writes from Pennsylvania, USA. Contact him at [email protected].I haven't been able to find any ARRL article or official statement on it, however this supposed communication from ARRL was posted on the digitalradio reflector:
"From: Henderson, Dan N1NDSubject: RE: Spread SpectrumTo: [deleted for privacy]Date: Tuesday, February 23, 2010, 7:13 AMHi Fred:I ran this by our technical experts. They concur that ROS is a spread spectrum mode and as such is not allowed by the FCC on bands below 222 MHz. Remember that approved emissions vary from IARU Region at times as well as between countries. So while the IARU Band Plan for Region 2 would allow it, SS is not permitted on the HF bands by the FCC/Thanks and 73Dan Henderson, N1NDRegulatory Information ManagerARRL, the national association for Amateur Radio™ "
But is ROS really spread spectrum? Just what is spread spectrum? Let's ask our friend, Part 97.
§97.3(c)(8) SS. Spread-spectrum emissions using bandwidth-expansion modulation emissions having designators with A, C, D, F, G, H, J or R as the first symbol; X as the second symbol; X as the third symbol
That's incredibly vague, but basically spread spectrum is taking a signal and spreading out its bandwidth in order to improve interference immunity and/or obscure the intelligence. There are two primary methods, direct sequence and frequency hopping. With direct sequence the intelligence is mixed with a pseudo-random bit sequence at transmit and demodulated in the receiver with the same pseudo-random sequence. With frequency hopping, the signal simply rapidly hops around a predetermined band. Apparently it's assumed that ROS is frequency hopping spread spectrum.
One key difference I see between ROS and commonly accepted frequency hopping spread spectrum systems is that there's no modulation on the ROS carriers. The intelligence in a frequency hopping spread spectrum system is not determined by the frequency of the carrier at any given moment, it's determined by the modulation on the carrier itself. (OK, if you're using QAM modulation there is a frequency modulation component, but that's totally independent of the frequency hopping.) In ROS the intelligence is carried by the frequency of the carrier in time. The only difference between ROS and MKSK, besides the symbol rate and bandwidth is that ROS has only one tone on at a time and MFSK can have multiple. But let's assume for a moment that ROS is frequency hopping spread spectrum. RTTY also frequency hops. It hops between two frequencies. This hopping does expand the bandwidth, so therefore using this same interpretation that has been applied to ROS, RTTY is also spread spectrum and therefore it is illegal below 222 Mhz.
I hope ARRL realizes that ROS is frequency shift keying and not spread spectrum and reverses this initial finding. We need to have common sense prevail and not turn this into another unnecessary rule interpretation quagmire like the whole emcomm and employers issue has become. If ROS stays within the bandwidth allowed for other HF digital signals, what does it matter? Let's use it and move on.
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