[RTTY] ARRL attack on current RTTY users

[Kok Chen]

On Nov 21, 2013, at 8:26 AM, Jeff Blaine wrote:

> There is a lot of "modernization" and "flexibility" listed - but who, beyond the PACTOR guys, would actually benefit from this change.  Figure that out and we can likely connect the dots from that group to this decision.

Unless the words "modernization" and "flexibility" are synonymous with the phrase "more data bandwidth," the ARRL proposal simply don't make any technical sense.

As I mentioned in an earlier private email to another reflector participant, take a look at all the advancements towards getting the most miles with the lowest power.  You need not look further than Joe Taylor's modes.

http://www.physics.princeton.edu/pulsar/K1JT/index.html

If you include the also widely used PSK31 (very good for folks with small antennas and low power when propagation is good) the focus on narrower bandwidths goes back for at least two and a half decades.

These folks had the freedom to use higher symbol rates and wider bandwidth, but choose not to.

Technically, you can use wider bandwidths to counter selective fades due to multipath in Rayleigh channels (best model for HF that has been used for decades now).  That is addressed in modern modes with good forward error correction (FEC) and longer data frames.  And even when you use simple two tone FSK, it has been known by amateurs since the 1960s that 170 Hz is already wide enough to derive information to apply a good automatic threshold correction to FSK.  As I mentioned in my "RTTY Demodulators" article,

"In a February 1964 article in the RTTY bulletin, Frank Gaudé reported that there is actually no significant difference anyway between the amount of selective fading between a wide shift and a narrow shift signal down to the 170 Hz region."

So, the need for wider bandwidths has nothing to do with finding better modes for HF communications.  It does allow you to push more bits per second through the channel.

BTW, you can include references in your comments to the RM, and the references can include Web links, references to RTTY Bulletins from the 1950s, or email to your kids, if those are pertinent.  Please feel free to do all the web research that you need and include references that you decide are pertinent to include in your own comments.

73
Chen, W7AY