The second graph shows 4 kHz as the worst. This is the dip between Mode 0 and
Mode 1 in the waveguide.
15 kHz range is the best for Mode 1 Earth Ionosphere Waveguide Propagation. The
antenna efficiency is the main reason navy transmitters have all moved up to 19
- 25 kHz. It is a trade off between antenna efficiency and frequency of best
propagation.
Naval communications use VLF Mode 1 and ELF Mode 0 at around 80Hz. Not much use
in between because it doesn't really work. Poor antenna efficiency combined
with high propagation loss.
73 John VA3VVV
--------------------------------------------
On Mon, 10/23/17, DK7FC <[email protected]> wrote:
Subject: Re: VLF: Using resonance effects of earth-ionosphere for radio
experiments
To: [email protected]
Received: Monday, October 23, 2017, 10:50 AM
PS: I don't want to say that
15 kHz is trivial, not at all. It is all
interesting (except skype!!), 20m, 80, 630m,
2200m, 36km, 46km, 58km,
101km, 309 km and
of course also 20 km! :-)
73 and good luck on the mid VLF!!!!!
Stefan
Am
23.10.2017 16:40, schrieb DK7FC:
> Hi
John,
>
> Yes, like on
HF it is a different league to work on 15 kHz or 8.27 kHz
> or 2.97 kHz. Working VK from DL in SSB
is usually easier on 20m than
> on 80m,
same for WSPR of course. So one may ask "Why are you
trying to
> work VK on 80m, 20m is much
easier?!"
> Some youngsters may even
ask "Why are you using radio at all, there is
> skype!!?!" :-)
>
> 73, Stefan
>
> Am 23.10.2017 16:17,
schrieb John Fisher:
>> Hi Stefan,
>>
>> Actually, 1 -
4 kHz is the worst frequency range as it is right
>> between the two waveguide Modes 0 and
1.
>>
>> ELF
around 100 Hz is good for Mode 0 and Mode 1 peaks around 15
kHz.
>>
>> 73
John VA3VVV
>>
>>
>>
--------------------------------------------
>> On Mon, 10/23/17, DK7FC<[email protected]>
wrote:
>>
>>
Subject: Re: VLF: Using resonance effects of
earth-ionosphere for
>> radio
experiments
>> To: "[email protected]"<[email protected]>
>> Received: Monday, October 23, 2017,
9:05 AM
>>
>>
Hi John,
>>
>>
Thank you.
>> The large image
is
>> well known meanwhile but i
did see the other one so
>> far.
Where did you take it from and are there
>> more informations?
>> What means ||Tn| ? I
>> guess n is the numer of hops. But T
= Tesla? Not
>> really. It should
be |B(n)|. So maybe something
>>
else. But it would make
>> sense
that is is
>> something that has to
do with the field strength. Odd...
>> Assuming it is actually the
fieldstrength, then
>> 1 kHz looks
most
>> interesting again. I
need
>> to continue to work in that
range!!
>>
>>
73, Stefan
>>
>> Am
>>
23.10.2017 14:21, schrieb John Fisher:
>> >
>> Hi
Stefan,
>> >
>> >
>>
Attached re two graphs on this subject you might find
>> interesting.
>> >
>> >
73
>> John VA3VVV
>> >
>> >
>> >
>> >
>>
--------------------------------------------
>> > On Mon, 10/23/17, DK7FC<[email protected]>
wrote:
>> >
>> > Subject:
>> VLF: Using resonance effects of
earth-ionosphere for radio
>>
experiments
>> > To: [email protected]
>> > Received: Monday, October
23, 2017,
>> 7:15 AM
>> >
>> >
Paul,
>> Markus, VLF,
>> >
>> >
Some days ago there have been
>>
> local
>> thunderstorms
near DL0AO in JN59.
>> >
Two
>> > images in
attachemnt.
>> > The distance
is about
>> > 225 km. The
thunderstorms were on a
>> small
spot only.
>> >
>> > The sferics are clearly
>> > pronounced
>> with an SNR increase of 10 dB
and
>> > more, quite a sharp
peak/trace. That's not
>> >
a new observation but now we
>>
> are operating
>> >
just in that frequency range!
>>
> The
>> effect
>> > seems to appear in
integer
>> multiples of about 1.7
kHz, which
>> >
>> > is roughly a wavelength of a
180 km,
>> and
>> > the earth-ionosphere
height
>> is
>> > just
>> > lambda/2.
>> >
>> >
It
>> would be most
>> > interesting to see how
>> a similar spectrogram looks from
>> > Pauls site (time and date
given in the images).
>> > Is
the effect still
>> > there in
881 km? How
>> > strong is it
expressed. Are the
>> frequencies
the same?
>> > If so, we
>> should try to find that region
of
>> > enhanced propagation,
by
>> > using a
>> 2-tone or
>>
> 3-tone carrier signal. No
>> problem to provide that from
>> > here.
>> >
>> >
The
>> > effect is less
expressed on 3.4 kHz in
>> this
event. Recently
>> > we
>> > discussed about a
geometric
>> single-hop
>> > path difference between
>> DK7FC and
>>
> DL0AO
>> > (Markus
calculated 63.3 km difference
>>
between groundwave and
>> >
>> > skywave). 5.17 is at a 1.09
lambda
>> > difference on that
path, so
>> > groundwave
and
>> > skywave will add
constructively. The 3rd order trace of
>> > the sferic resonance effect
is also at
>> 5.1
>> > kHz!
>> > 3.4
>> kHz, or the 88.2 km wave, is
then
>> > at
>> 1.4 lambda difference, so
>> > skyway
>> and
>> >
groundwave do not add so
>>
constructive. Maybe this explains
>>
>
>> > the lower expressed
resonance
>> effect?
>> >
>> >
It
>> looks like there can be
SNR
>> > difference of several
dB when changing
>> > the
>> > frequency
>> by just a few 10 Hz, at least
arround 5.1 kHz and
>> > on
the
>> > path to
>> DL0AO. We should try to
>> > check
>> that!
>>
>
>> > Could
>> there be
>>
> a frequency with an
>>
advantage on the way to RN3AUS? On a
>> > 2000 km path the effects
will be less
>> > expressed.
But worth to think about...
>> >
>> > 73, Stefan
>>
>>
>>
>
|
