Date: Fri, 29 Jan 2010 12:14:58 +0100
To: "rsgb_lf_group@blacksheep.org" <rsgb_lf_group@blacksheep.org>
From: Rik Strobbe <rik.strobbe@fys.kuleuven.be>
In-Reply-To: <301460.22362.qm@web86506.mail.ird.yahoo.com>
References: <20100129092211.3507031E702@smtps01.kuleuven.be>
 <301460.22362.qm@web86506.mail.ird.yahoo.com>
Mime-Version: 1.0
Message-Id: <20100129111449.17892F3863@smtps02.kuleuven.be>
Subject: Re: LF: Question to the groundwave
Content-Type: text/plain; charset="us-ascii"; format=flowed
Sender: owner-rsgb_lf_group@blacksheep.org
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org


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 <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 > >  > 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: > 
>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 > >  > >