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Message-ID: <337596.18969.qm@web86504.mail.ird.yahoo.com>
Date: Fri, 29 Jan 2010 11:33:17 +0000 (GMT)
From: ALAN MELIA <alan.melia@btinternet.com>
To: rsgb_lf_group@blacksheep.org
In-Reply-To: <20100129111449.17892F3863@smtps02.kuleuven.be>
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Subject: Re: LF: Question to the groundwave
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Hi Rik, No I dont know what formulae Reg used but I am guessing he used th=
e proceedures in the ITU Recommendations. I have a paper with a load of gr=
aphs 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 <rik.strobbe@fys.kuleuven.be> wrote:

> From: Rik Strobbe <rik.strobbe@fys.kuleuven.be>
> Subject: Re: LF: Question to the groundwave
> To: "rsgb_lf_group@blacksheep.org" <rsgb_lf_group@blacksheep.org>
> Date: Friday, 29 January, 2010, 11:14
> Hello Alan,
>=20
> 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
> ?
>=20
> 73, Rik  ON7YD
>=20
> PS: including some carriage returns in your mails would be
> nice ;-)
>=20
>=20
> 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 <rik.strobbe@fys.kuleuven.be>
> wrote: > From: Rik Strobbe <rik.strobbe@fys.kuleuven.be>
> > Subject: Re: LF: Question to the groundwave > To:
> "rsgb_lf_group@blacksheep.org"
> <rsgb_lf_group@blacksheep.org>
> > Date: Friday, 29 January, 2010, 9:22 > >=20
> > Hello Stefan, > > > ground waves (surfaces
> waves) are a tricky thing. > > The assumption you made
> (+6dB TX power =3D 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 =3D 55.1dB
> > > 500km =3D 65.3dB > > 750km =3D 74.7dB > >
> 1000km =3D 83.5dB > > 2000km =3D 115.4dB > > 3000km
> =3D 144.5dB > > 4000km =3D 172.2dB > > 5000km =3D
> 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: > owner-rsgb_lf_group@blacksheep.org
> > im Auftrag von ALAN MELIA > > Gesendet: Fr
> 29.01.2010 01:51 > > An: rsgb_lf_group@blacksheep.org
> > > 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 > >  > >
>=20
>=20
>=20