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From: "Markus Vester" <markusvester@aol.com>
To: <rsgb_lf_group@blacksheep.org>
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In-Reply-To: <52EEA4EF.8070307@iup.uni-heidelberg.de>
Date: Mon, 3 Feb 2014 00:52:20 +0100
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Subject: Re: LF: DX VLF experiments in 3HD
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Stefan,

technically this is an intruiging experiment. Doubling the frequency =
from 8.3 to around 17 kHz would allow you to bring the same antenna to =
16-fold radiated power. An intercontinental detection of a 20 mW signal =
on that QRG seems quite feasible.=20

But I have my doubt that transmitting a low-level "fundamental" along =
with the signal would render it legal. You argue that in theory you =
might radiate arbitrary power on 1f, thus allowing you some moderate =
output at 3f. Then how would one measure harmonic suppression - =
presumably with a calibrated receive antenna somewhere in the radiation =
field. So you'd really (and not only hypothetically) have to physically =
radiate 60 dB more on 5.75 kHz, or not?

But wait a minute, who says 60 dB? Formally there are no rules for =
transmitters below 8.3 kHz, neither for output power nor for spectral =
properties. So you can claim the harmonic may be allowed to radiate even =
stronger than the fundamental. The catch may be transmitters below 8.3 =
are not licensed radio transmitters. One could argue that they are thus =
not elegible to produce any specified amount of harmonics (at least not =
beyond what general EMC limits for electrical equipment would =
prescribe).

There may be another pitfall regarding the "wanted" signal versus the =
"undesired" harmonics. By the context of the experiments, it is quite =
obvious that  the 3f signal is the intended transmission, and the 1f =
subharmonic is no more than an alibi. Taking it further, one could claim =
to transmit legally anywhere on HF, just because his TX contains a =
switched mode power supply which happens to leak some low-level junk =
below 8 kHz.

Stafan, don't get me wrong, I'm in no way against you or anyone =
conducting this kind of experiment. I find it novel and interesting, and =
I don't believe anyone else will have a good reason to complain about =
interference. I just dont believe that someone would really buy the =
legal cover story.

73, Markus (DF6NM)


----- Original Message -----=20
From: Stefan Sch=E4fer=20
To: rsgb_lf_group@blacksheep.org=20
Sent: Sunday, February 02, 2014 9:05 PM
Subject: Re: LF: DX VLF experiments in 3HD


VLF,=20

That 3rd harmonic is on the 17 km band. Do we have any experiences about =
local diurnal propagation?

Sooner or later there will be misunderstandings and some will say i am =
transmitting on 17.265 kHz although the TX runs on 5.755 kHz!

I had a thought about that. 3rd harmonics are generated by all HF =
amateurs, but we all ignore them. We actually can ignore them if they =
are well attenuated but that doesn't mean that they do not exist! BTW =
has someone ever tried to decode a 3HD signal (that name, 3HD, is just =
for fun, like the Dreamers band, a shortcut for 3rd harmonic detection, =
reminds on HD quality movies or 3D glasses ;-) ) in OPERA mode?=20

Example: When someone transmits a legal (!) QRO signal of 750W (in DL) =
on the 160m band using a typical lambda/4 vertical (which is radiating =
the 3HD signal because there it is lambda 3/4 and thus low impedant =
too), using a 60 dB attenuating low pass filter, which is quite a good =
supression, then there should be a 750uW signal on the 53m band, which =
could be detected in some distance, probably several 10km when using =
slow modes like OPERA-4 (WSPR will not work so easily here). Receiving =
this 3HD signal is certainly not absolutely strictly forbidden :-) So =
actually the amateurs can do legal QRPP tests in slow modes on 53m, =
can't they? Would you think that it is ethical unjustifiable to try to =
receive such a signal if it is there anyway and legally generated?

Example2: PA0WMR is often TXing OP8 on 478.x kHz, making 2000km =
distance. If someone in say 30 km distance can receive him on 1434 kHz =
(if there would be no AM BCD stn), close to the decode limit, would =
something be wrong with this test?

I know from WSPR QRP transmissions from DL to VK on 15m with 0.1 W TX =
power!! So i assume a 3HD signal could be detected in a few 100 km, =
maybe?

Below 8.3 kHz there is no TX power limitation and we can certainly =
assume that no interference is caused to anyone at 3HD, just like in the =
above example (53m band ( i never tried it)).So why not trying to do =
tests like these today? The noise floor is much lower there which =
improves the situation :-)

73, Stefan/DK7FC

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http-equiv=3DContent-Type>
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<BODY bgColor=3D#ffffff text=3D#000000>
<DIV><FONT size=3D2 face=3DArial>Stefan,</FONT></DIV>
<DIV><FONT size=3D2 face=3DArial></FONT>&nbsp;</DIV>
<DIV><FONT size=3D2 face=3DArial>technically this is an intruiging =
experiment.=20
Doubling the frequency from 8.3 to around 17 kHz would allow you to =
bring the=20
same antenna to 16-fold radiated power. An intercontinental detection of =
a 20 mW=20
signal on that QRG seems quite feasible. </FONT></DIV>
<DIV><FONT size=3D2 face=3DArial></FONT>&nbsp;</DIV>
<DIV><FONT size=3D2 face=3DArial>But I have my doubt that transmitting a =
low-level=20
"fundamental" along with the signal would render it legal. You argue =
that in=20
theory you might radiate arbitrary power on 1f, thus allowing you some =
moderate=20
output at 3f. Then how would one measure harmonic suppression - =
presumably with=20
a calibrated receive antenna somewhere in the radiation field. So you'd =
really=20
(and not only hypothetically) have to physically radiate 60 dB more on =
5.75 kHz,=20
or not?</FONT></DIV>
<DIV><FONT size=3D2 face=3DArial></FONT>&nbsp;</DIV>
<DIV><FONT size=3D2 face=3DArial>But wait a minute, who says 60 dB? =
Formally there=20
are no rules for transmitters below 8.3 kHz, neither for output power =
nor for=20
spectral properties. So you can claim the harmonic may be allowed to =
radiate=20
even stronger than the fundamental. The catch may be transmitters below =
8.3 are=20
not licensed radio transmitters. One could argue that they are thus not =
elegible=20
to produce any specified amount of harmonics (at least not beyond what =
general=20
EMC limits for electrical equipment would prescribe).</FONT></DIV>
<DIV><FONT size=3D2 face=3DArial></FONT>&nbsp;</DIV>
<DIV><FONT size=3D2 face=3DArial>There may be another pitfall regarding =
the "wanted"=20
signal versus the "undesired" harmonics. By the context of the =
experiments, it=20
is quite obvious that&nbsp; the 3f signal is the intended transmission, =
and the=20
1f subharmonic is no more than an alibi. Taking it further, one could =
claim to=20
transmit legally anywhere on HF, just because his TX contains a switched =
mode=20
power supply which happens to leak some low-level junk below 8 =
kHz.</FONT></DIV>
<DIV><FONT size=3D2 face=3DArial></FONT>&nbsp;</DIV>
<DIV><FONT size=3D2 face=3DArial>Stafan, don't get me wrong, I'm in no =
way against=20
you or anyone conducting this kind of experiment. I find it novel and=20
interesting, and I don't believe anyone else will have a good reason to =
complain=20
about interference. I just dont believe that someone would really buy =
the legal=20
cover story.</FONT></DIV>
<DIV><FONT size=3D2 face=3DArial></FONT>&nbsp;</DIV>
<DIV><FONT size=3D2 face=3DArial>73, Markus (DF6NM)<BR></FONT></DIV>
<DIV><FONT size=3D2 face=3DArial></FONT>&nbsp;</DIV>
<DIV style=3D"FONT: 10pt arial">----- Original Message -----=20
<DIV style=3D"BACKGROUND: #e4e4e4; font-color: black"><B>From:</B> <A=20
title=3DStefan.Schaefer@iup.uni-heidelberg.de=20
href=3D"mailto:Stefan.Schaefer@iup.uni-heidelberg.de">Stefan =
Sch=E4fer</A> </DIV>
<DIV><B>To:</B> <A title=3Drsgb_lf_group@blacksheep.org=20
href=3D"mailto:rsgb_lf_group@blacksheep.org">rsgb_lf_group@blacksheep.org=
</A>=20
</DIV>
<DIV><B>Sent:</B> Sunday, February 02, 2014 9:05 PM</DIV>
<DIV><B>Subject:</B> Re: LF: DX VLF experiments in 3HD</DIV></DIV>
<DIV><FONT size=3D2 face=3DArial></FONT><BR></DIV>
<DIV>VLF, <BR><BR>That 3rd harmonic is on the 17 km band. Do we have any =

experiences about local diurnal propagation?<BR><BR>Sooner or later =
there will=20
be misunderstandings and some will say i am transmitting on 17.265 kHz =
although=20
the TX runs on 5.755 kHz!<BR><BR>I had a thought about that. 3rd =
harmonics are=20
generated by all HF amateurs, but we all ignore them. We actually can =
ignore=20
them if they are well attenuated but that doesn't mean that they do not =
exist!=20
BTW has someone ever tried to decode a 3HD signal (that name, 3HD, is =
just for=20
fun, like the Dreamers band, a shortcut for 3rd harmonic detection, =
reminds on=20
HD quality movies or 3D glasses ;-) ) in OPERA mode? =
<BR><BR><U>Example:</U>=20
When someone transmits a legal (!) QRO signal of 750W (in DL) on the =
160m band=20
using a typical lambda/4 vertical (which is radiating the 3HD signal =
because=20
there it is lambda 3/4 and thus low impedant too), using a 60 dB =
attenuating low=20
pass filter, which is quite a good supression, then there should be a =
750uW=20
signal on the 53m band, which could be detected in some distance, =
probably=20
several 10km when using slow modes like OPERA-4 (WSPR will not work so =
easily=20
here). Receiving this 3HD signal is certainly not absolutely strictly =
forbidden=20
:-) So actually the amateurs can do legal QRPP tests in slow modes on =
53m, can't=20
they? Would you think that it is ethical unjustifiable to try to receive =
such a=20
signal if it is there anyway and legally =
generated?<BR><BR><U>Example2</U>:=20
PA0WMR is often TXing OP8 on 478.x kHz, making 2000km distance. If =
someone in=20
say 30 km distance can receive him on 1434 kHz (if there would be no AM =
BCD=20
stn), close to the decode limit, would something be wrong with this=20
test?<BR><BR>I know from WSPR QRP transmissions from DL to VK on 15m =
with 0.1 W=20
TX power!! So i assume a 3HD signal could be detected in a few 100 km,=20
maybe?<BR><BR>Below 8.3 kHz there is no TX power limitation and we can =
certainly=20
assume that no interference is caused to anyone at 3HD, just like in the =
above=20
example (53m band ( i never tried it)).So why not trying to do tests =
like these=20
today? The noise floor is much lower there which improves the situation=20
:-)<BR><BR>73, Stefan/DK7FC</DIV>
<DIV><FONT size=3D2 face=3DArial></FONT>&nbsp;</DIV>
<DIV>...</DIV></BODY></HTML>

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