[RTTY] RTTY Now trashy signals

Wed Jan 9 12:56:41 EST 2013

Al,

You have a great point.  And I think it's worse because you are assuming 
that once some "standard" is established, then guys will be able to measure 
it the same way, and as we can see in the PSK case, it's not at all a safe 
assumption.

In fact, one of the reasons I hate to run PSK is the amount of busy-body 
signal police on the band.  I got tired of guys calling me out for having a 
wide signal when the actual issue was their improper receive setup.  I have 
the KK7 PSK IMD meter here on the shelf and could send those guys shots 
of -28 db readings.  At the same time, they would swear I was 5 db only.

We have the same issue here with RTTY.  If you are going to critique 
someone's signal, you had better make sure that your setup is IMD product 
generation free.  And that is not a simple task considering things in the 
environment beyond the antenna are potential contributors in the case of 
strong signals.

My guess is most FSK installations are fine.  And most AFSK installations 
are fine.  And that the cases where guys have trouble is at it's root either 
AF feeds with some clipping due to improperly set AF levels.  Or that they 
have their antennas close to their gear and are not properly controlling the 
RFI.

73/jeff/ac0c
www.ac0c.com
alpha-charlie-zero-charlie

-----Original Message----- 
From: aflowers at frontiernet.net
Sent: Wednesday, January 09, 2013 11:03 AM
To: Al Kozakiewicz ; rtty at contesting.com
Subject: Re: [RTTY] RTTY Now trashy signals

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

Fair enough, Al!  I've had my coffee now...

Here's a very simple way that might get at the crux of the issue.  Let's say 
that signal number #3 was your signal (yes, this was recorded off the air 
this weekend, and no, I'm not going to identify him or her publicly):

http://www.frontiernet.net/~aflowers/rtty_examples/

Would knowing that was was being heard up and down the East (and probably 
West) coast bother your conscience enough to look for ways to change 
something?  Does anyone want to say 'no'?

We all (well, most of the big contesters) managed to modify our early model 
MPs to reduce the nasty CW  key clicks without some objective standard from 
on high.  The problem was identified and people came up with solutions 
pretty quickly.  Hams have historically been able to make many changes for 
the better without big brother drawing a line in the sand.

Andy K0SM/2

________________________________
From: Al Kozakiewicz <akozak at hourglass.com>
To: "aflowers at frontiernet.net" <aflowers at frontiernet.net>; 
"rtty at contesting.com" <rtty at contesting.com>
Sent: Wednesday, January 9, 2013 11:08 AM
Subject: RE: [RTTY] RTTY Now trashy signals

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

----------------------------------------------------------------------

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

------------------------------
_______________________________________________
RTTY mailing list
RTTY at contesting.com
http://lists.contesting.com/mailman/listinfo/rtty
_______________________________________________
RTTY mailing list
RTTY at contesting.com
http://lists.contesting.com/mailman/listinfo/rtty 