Hi Rik, No I dont know what formulae Reg used but I am guessing he used the
proceedures in the ITU Recommendations. I have a paper with a load of graphs
and I think formula it you would like it. I picked it up off the web but I am
not sure where. I checked his results on DCF39 and HGA22 and get senible
agreememt for ground condition "7". Lakihegy is more difficult to judge here in
daytime (the skywave is stronger than the groundwave) but I took the minimum of
the morning and evening dips to the pure groundwave.
Best wishes
ALan G3NYK
--- On Fri, 29/1/10, Rik Strobbe <[email protected]> wrote:
> From: Rik Strobbe <[email protected]>
> Subject: Re: LF: Question to the groundwave
> To: "[email protected]" <[email protected]>
> Date: Friday, 29 January, 2010, 11:14
> Hello Alan,
>
> I agree that the typical 500kHz QSB is indeed ionospheric
> multipath causing interference. I surface wave was involved
> I would only notice it with stations I can also hear during
> daytime.
> About Reg's program: any idea what formula's are behind it
> ?
>
> 73, Rik ON7YD
>
> PS: including some carriage returns in your mails would be
> nice ;-)
>
>
> At 11:57 29/01/2010, you wrote:
> > Hi Stephan and Rik, yes Rik I was meaning to mention
> the late Reg's program. Your estimate is probably right and
> the thing is complicated further by even in daytime the
> skywave being stronger than the ground wave beyond 1000km
> (see my plots of Brian CT1DRP's data on DCF39 to Oporto
> route) On the longer paths you cannot rely on the skywave
> only consisting of one hop(whereas I believe this may be
> true at short distances) there is some evidence that at
> night on 500kHz there are two different paths even at quite
> short distances (cf the reported very deep fading on
> stations that cannot be heard in daytime....i.e the fading
> is probably between two skywave path rather than ground and
> skywave. Some of Graham's work suggests thes may be
> reflection from two different heights on 500kHz rather than
> two hop.....not a phenomena that exists on 136kHz) Great
> Fun.....much better than boring HF :-)) Alan G3NYK --- On
> Fri, 29/1/10, Rik Strobbe <[email protected]>
> wrote: > From: Rik Strobbe <[email protected]>
> > Subject: Re: LF: Question to the groundwave > To:
> "[email protected]"
> <[email protected]>
> > Date: Friday, 29 January, 2010, 9:22 > >
> > Hello Stefan, > > > ground waves (surfaces
> waves) are a tricky thing. > > The assumption you made
> (+6dB TX power = double distance) > takes only the >
> 2D spreading loss into account. This would be correct if
> > the ground would > be a perfect conductor and if the
> earth would be flat. > > In reality you have 2
> additional losses: diffraction loss > (due to the >
> earth curve) and ground loss. > > The bad message is
> that these losses both have a more or > less 1D >
> behavior, and thus their attenuation is more or less linear
> > to the > distance. > > The late G4FGQ wrote a
> very good DOS application (named > GRNDWAVE3) where >
> you can put in a lot of parameters (distance, antenna >
> efficiency, > frequency, ground type, TX power) and it
> gives you the path > attenuation, > field strength at
> RX end and RX antenna voltage. > > It must be on the
> web on several places (google it), but in > case you >
> cannot find it I can send it to you. > > Just as an
> example the path loss this programme gives > for
> 137kHz > and an average ground: > > 250km = 55.1dB
> > > 500km = 65.3dB > > 750km = 74.7dB > >
> 1000km = 83.5dB > > 2000km = 115.4dB > > 3000km
> = 144.5dB > > 4000km = 172.2dB > > 5000km =
> 199.0dB > > As you can see doubling the distance
> "costs" far > more that 6dB > (by surface wave, sky
> wave is a different story). > > I haven't kept any
> records by I think that the surface > wave limit for >
> most amateur stations is 1000-1200km (on 137kHz), maybe a
> > bit more in > QRSS. Beyond that you are far better
> of with sky waves. > > > 73, Rik ON7YD - OR7T
> > > > At 02:51 29/01/2010, you wrote: > > Hi
> Alan and LF, > > > > > I know there are
> some of you who can easily > answer my > question that
> follows :-) > > > > The maximum distance
> of the groundwave at a > specific > fieldstrength E is
> (about) linear increasing with the > antenna current of
> > the TX antenna, right? > > So, if i have an
> antenna current of 0,5A and get a maximum > distance of
> > 1000km, i would reach 2000km with 1A (same RX, same
> > surrounding noise > level, same average ground
> properties, same OP ;-) > )?. > > > > I
> expect, that the groundwave does not > immediately stop
> > beyond this 2000km border but rather decreases with
> 1/r, > just as > before. > > > > So,
> if we assume one is increasing the antenna current in >
> the above > example to 7A, is then a distance of 14000km
> possible? > Sure, thats a very > theoretical question
> since there will not be the same > ground conductivity
> > on the whole distance but anyway. > > >
> > And it is said that the groundwave is (nearly) not
> affected > by the > daytime, by the season and so on.
> There must be > interferences with the > sky wave, so
> QSB, but this does not affect the groundwave > at an
> other RX > QTH, where no sky wave is present!? >
> > > > If there is so much sea water between a
> transatlantic > distance, why is it > so difficult to
> do it with the groundwave? On HF or MF it > is clear but
> on > LF? > > > > Tnx for enlightning
> answers... > > > > Stefan/DK7FC >
> > > > > Von: > [email protected]
> > im Auftrag von ALAN MELIA > > Gesendet: Fr
> 29.01.2010 01:51 > > An: [email protected]
> > > Betreff: Re: LF: Ok its a sea path .. but this is
> > getting > silly > > > > Ah this 500k
> stuff is too easy Graham :-)) > oh for 73kHz > again !
> > > > Alan G3NYK > > > >
>
>
>
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