Topband: ARRL Request for Comments on Digital Modes
merlebone at charter.net
Sun Mar 9 14:54:11 EDT 2014
I was interested in the comments on this reflector about the request for
“amateur radio operator’s” comments on digital modes. I personally believe
the ARRL proposal was a poor attempt to provide some opportunity for
high speed data on the Ham Bands. There are a lot of issues associated with
the introduction of high speed wide-band data on the ham bands.
1. Amateur radio equipment is not designed to create or transmit 2.8KHz
data signals .... single carrier or multi-carrier ..... without creating significant
“out of band” distortion products.
2. I seriously doubt anyone will be trying to transmit a 2.8KHz data
signal on “relatively low power.” That means we will be opening the bands
up to “internet type traffic” using full power amateur signals. Few of todays
linear amplifiers are designed to “faithfully reproduce” multi carrier data
signals (I have spoken with an ARRL leader, who told me they expect to
see multicarrier high speed data signals introduced).
3. “Identifying” wideband data signals will be very very difficult. Most of
todays wideband data modems operate over 5 or 6 modes – depending
on receive signal quality – making it very hard to know what mode the signal
is operating with at any given time. Further, imbedded coding – to optimize
signal detection can have the effect of “encrypting” the clear data.
4. People don’t “talk” over high speed data circuits – unless they are using
digitized voice signals. What people do is “move data” from one machine to another.
So what is going to happen is “machine to machine” band usage will begin to
replace “people to people” band usage. Machines can send “virtually unlimited”
data to other machines. Link holding times can go from minutes to hours. This
can be especially desirable in countries without “ubiquitous” internet service.
5. Radio Amateurs have almost no equipment to understand their transmitted
signals. Wideband data signals will have to be “monitored” to allow the operator
to know that they are actually limiting their bandwidth to 2.8 KHZ and to know that
they are using the maximum bandwidth required by their signaling mode.
6. The League has proposed all current “data bandwidth allocation” be opened
to wideband data. The ARRL “bandplan” has no standing in the law and is not
enforceable – just look at band operations during any major RTTY contest. People
will operate wideband data signals wherever it is legal.
If the League leadership wants to introduce wideband data to the Amateur Bands,
it should be done very carefully, in a limited way, in order to understand the
interaction of wideband data modes with current signal modes. This is about the
third attempt at this kind of band restructuring. I am really glad that some of the
Board members – for the first time I remember in over 10 years – have opened this
issue to comment by radio amateurs. I hope everyone will think about this and
submit their comments. This could have a very significant effect on how our
ham bands operate.
More information about the Topband