[RTTY] RTTY Now trashy signals

[Al Kozakiewicz]

Don't underestimate the importance of the words "in the sense that"!

While we are all ultimately responsible for operating to a set of acceptable standards, the FSK operator has no choice to make in the matter short of ceasing operation if their transmitter is performing poorly*.  The AFSK operator, on the other hand, makes all kinds of choices in software, soundcard, interface, computer output levels, transmitter gain, compression, ALC, etc. etc.  All have a direct impact on signal quality.

I too would be interested in knowing both how to define and measure the quality of FSK transmissions and how products perform with respect to those metrics.

*-Anyone can plot quality (however you'd like to define that term) of transmitted signals along a line from bad to good.  What I'd like to know is where you draw a line distinguishing acceptable from unacceptable?  If width is king, queen and everything in between with respect to RTTY signals, how many db down do the modulation byproducts have to be how far from the mark/space frequency?  And who gets to decide that?

Al
AB2ZY
 

________________________________________
From: RTTY [rtty-bounces at contesting.com] On Behalf Of aflowers at frontiernet.net [aflowers at frontiernet.net]
Sent: Wednesday, January 09, 2013 10:28 AM
To: rtty at contesting.com
Subject: Re: [RTTY] RTTY Now trashy signals

Al,

I respectfully disagree in small detail (and please forgive me if I misunderstood).  I think everyone owns equal responsibility for his or her signal *regardless of the process creating it*.  We make the decision to either trust that the manufacturer has implemented the feature properly and we choose use it, or we choose to do it by other means.  Contesters are always making decisions like this.  Really capable people will measure the things that matter to them, if they can, and the magazines try to publish product reviews to help us out.  In the final analysis we make a good choice or we make a bad choice based on available information, but either way we make the choice and we are responsible for the signal we put out.  Sometimes getting a new radio may be the only viable option, and that is expensive, and yes, we will be upset at the manufacturer for giving us a raw deal.

I think your main point is that "the transmitter made me do it" isn't a justification for keeping on doing it.  Spot on, in my opinion.

I think that begs a really important question though: is there any meaningful difference among the FSK signals generated by different radios' internal FSK generators.  Forget whether it's done by switching the LO frequency, by magical DSP fairies, or by black and white mice spinning the mark and space wheels next to the flux capacitor:  *among the internal FSK generators in the K3, IC-7800, FT-1000MP, and IC-706, or any radio made in the last 15 years, is there any meaningful difference when it comes to the RF coming out?*

If so, what are the differences?  Anyone have pictures of radios side by side when keyed in their "FSK" mode?

Andy K0SM/2


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Which was basically my point.  Discounting analog FSK implementations from 30 years ago, there is nothing you, Joe Ham,  can do should it be proved that, yes indeed, your 2 year old DSP transceiver is splattering when modulated using FSK.  There are no user accessible adjustments and with the few DSP designs I've looked at there are no internal hardware adjustments either so you can probably safely attribute the problem in that case to bad design.  Which has no cure except to buy a different model radio.

A ham running AFSK owns a lot more responsibility for the cleanliness of his signal than one running FSK in the sense that AFSK performance is more dependent on user configuration.

Al
AB2ZY

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