Re: [IRCA] [NRC-AM] 5Khz to 6Khz Sweep Tones and/or Morse Code

["Bob Foxworth" <rfoxwor1@xxxxxxxxxxxxxxx>]

Reply at bottom...

----- Original Message ----- 
From: "Les Rayburn" <les@xxxxxxxxxxxxxxxx>
To: "IRCA" <irca@xxxxxxxxxxxxxxxx>; "NRC AM List" <am@xxxxxxxxxxx>;
"ABDX" <ABDX@xxxxxxxxxxxxxxx>
Sent: Monday, November 06, 2006 13:14
Subject: [NRC-AM] 5Khz to 6Khz Sweep Tones and/or Morse Code


>
> Attached below is a suggestion that I received from noted DX'er Craig
Healy
> that I think has quite a bit of merit. In a nutshell, he suggests
adding
> high frequency sweep tones and/or Morse Code signals to future tests.
>
> Since the tones and code would occur at 5khz or slightly higher, we'd
be
> able to use very narrow bandwidths and avoid the carriers all
together.
> This indeed might make it easier to DX these tests.
>
> My problem is that I currently am limited to using WinMorse for Morse
> Code generation and it maxes out at 1Khz tones. I have no ability to
> generate the sweep tones at any frequency and have simply been
> reusing the ones created by Fred V.
>
> Can someone on the lists point me towards software that would meet
> these needs or offer suggestions?
>
> Also, what do the rest of you think of this technique?
>
>
>
> Les Rayburn, N1LF
> NRC/IRCA Broadcast Test Coordinator
> Please call anytime 24/7 if your transmitter
> will be off the air for maintenance.
> (205) 253-4867


> ----- Original Message ----- 
> From: "Craig Healy" <craig@xxxxxxxxxxxxxx>
> To: "Les Rayburn" <les@xxxxxxxxxxxxxxxx>
> Sent: Monday, November 06, 2006 9:40 AM
> Subject: Tones
>
>
> > Hi Les,
> >
> > I've been thinking about test content that could be broadcast
without
> > disrupting normal programming.  Years ago I used morse code at a
5KHz
> > audio
> > frequency.  Transmitters pass it easily, but most receivers won't.
Also,
> > the success of the sweep tones has been good.  I first used those in
a
> > test
> > at WSYB-1380 in Vermont in the mid-70's.  Worked well, and one DXer
even
> > complained that "someone was trashing the frequency" with them while
he
> > was
> > listening for the test.  (grin)
> >
> > How about a combination of 5KHz morse and a sweep tone that goes
from 4 to
> > 6
> > KHz?  I bet I could put that on a station and no local listener
would
> > really
> > even hear it.
> >
> > Additional bonus:  It puts DXable content on a split channel halfway
> > between
> > the 10KHz North American steps.  Set your receiver with a narrow
filter
> > and
> > BFO to the split, and ignore the carrier completely.
> >
> > Do you have the oscillator that can make those tones?
> >
> > Craig

I think this is an excellent idea and in fact I have been one of
the proponents of doing this, in past years, but it is great that
this idea is being voiced again while we have the technical
means and interest to make it happen.

My thoughts are that using 5 kHz audio, in AM envelope detection
mode, is probably not optimum as the IF bandwidth of many
receivers probably is not great enough to pass both the carrier
and (either) sideband, a necessary step to demodulate 5 kHz
audio. If your receive IF BW is only 3000 Hz you will simply
never hear the 5 kHz sideband tone.

My thinking is that the optimum mode is to transmit the 5000 Hz
tone (at full modulation percentage), tune the receiver to either
the upper or lower sideband (whichever is clearer at the RX
QTH), use the BFO, and use narrow BW as Craig said. This would
allow the audio (keyed audio at the xmtr) to appear as a keyed
CW signal at the receiver 6 dB down from whatever the carrier
would appear as. However it would allow reception on what
would otherwise be a truly "clear channel." (as clear as they
now get, with all the sideband splash).

The philosophical question that arises is this. Present day
testing uses AM detection of modulated CW notes (instead
of detection of voice which contains much less spectral
density). Even hearing a modulated CW note still adheres
to the concept of hearing the desired DX station in AM mode,
which is the manner in which the station is intended to
broadcast. I think this "legitimizes" the logging.

Doing the process - as I outlined it above - is somewhat
of a kludge, as it is no longer hearing an AM station, but
then becomes hearing an _artifact_ of an AM signal, in a
manner not intended by the station operator.

The philosophical divergence splits DXers into two camps.
The technical camp is interested in how well the signal
is propagating. CW detection of sidebands (only) of an
AM station gives a greater degree of indication of how well
the signal is propagating. Hearing the weak CW carrier
of the keyed audio sideband evokes memories of tricks
such as detection of SAH on the AGC buss to infer the
presence of stations too weak to create audio. One could
call this the GPN mode, and I am mainly a subscriber to this
mode. I'd think users of Argo, Spectran enc fit neatly into
this class.

The other camp is the QSL-ing reception camp. WIll these
DXers be willing to accept a QSL from an AM broadcast
station that was heard in CW mode? It would cause me
some uneasiness. Since I gave up collecting QSL's
years ago (I did report WDAB 1580 as a courtesy), it is
not that much of an issue for me.

One final note. The modulating frequency could be dropped
down to say 3000 Hz which could well create detectable
audio, at the edge of all of the sideband energy from all the
other competing signals. Detection of the sideband in CW
mode could serve as a pointer to how well the detection
of the sideband in AM mode is/could be working.

An anecdote from the 1968-1970? era, on a Monday morning
WCBS was doing a proof and was using 7500 Hz, 10000 Hz
tones etc at full power. There was a talk program in progress on
WLS-890. This was shortly after CBS reporter Michele Clark
died in a plane crash, I believe in Chicago, and this accident
was being discussed. The conspiracy theorists -- in CHICAGO --
thought that "WLS was being jammed", and said so on the air.

I was possibly the only person, anywhere, at that time, who
understood the circumstances of what was actually happening.

It was actually sort of annoying as I was wasting a good Monday
DX session to listen to this interesting discussion. There was
a lot of speculation in those days surrounding the circumstances
of the death of Clark.

It was all due to 10 kHz audio sideband energy, manually tuned
on an HP 200C close enough to create a raspy growl on 870 and
890 ... Don't discount the power of a sideband signal.

Tha's my thoughts anyhoo.   - Bob                   1841 est






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