Hi Graham, ah but yes it will!!. The skip you talk about is due to the
ground wave fading below the noise qrm at ranges before the skywave starts
to come in at good strength. This is well known in the Lowfer (160 to 180kHz
1 Watt DC) fraternity in the States. the higher power Part 5 stations dont
get this problem. On the commercial station power levels the ground wave
equals the skywave strength at somewhere around 700 km (CCIR reccs), and if
you plug the figures into to the late Reg Edwards GRNDWAV4 program you will
see how the ground wave fades with decreasing power level. Those of us that
live in domestic areas have to put up with a higher level of blanketing
noise than John, which make the situation far worse.
A little bit more power could enable us to achieve better groundwave ranges
in daytime than are possible on top-band. Then add to that the possibility
of daytime skywave at longer distances and it could well help. There will
always be a rapid fading at shortish distances (100 to300km) but more power
would give some fade margin so the signals didnt go right out.
On the data, a "locked" signal should be somewhere around at least 6dB
better under fading but it has to flywheel its parameters through the fade,
not suddenly start hunting for them again when the signal disappears. Much
data software is not written for these LF type conditions, Amtor ARQ would
be good with some error correction and longer bursts than 3 chars....
possibly adaptive to match the fading conditions. The origin SITOR was
designed for HF conditions which have different problems. Selective fading
is not really an issue at LF. I was involved (at work) in a kite fly about
a Marine Radio data protocol that would have used an (A)X25 type of
protocol with narrow bandwidth and a packet handshake that would have been
very effective. The ultimate is GPS locked and that is very effective. If
you want to see the the effectiveness of a locked system look at WOLF. This
is not designed for "conditions adaptive" operation though, but I have
copies signals way below the level QRSS can be seen on 136kHz. Even the "QSO
mode" Wolf B put in does not make it friendy for qso work. A good system
should go quickly when conditions are good and slow down, integrating the
repeats, in bad spells, until the packet checksums agree.
Alan G3NYK
----- Original Message -----
From: "Graham" <[email protected]>
To: <[email protected]>
Sent: Thursday, November 01, 2007 9:01 PM
Subject: Re: LF: RE: 500 kHz report / Great expectations
> Good point's john .
>
>
>
>
>
> >>>My point was that Dave has said more than once that he struggles to be
> > heard, despite receiving other more distant stations with seeming
ease<<<
>
>
>
> But that's the point, this band demonstrates the concept of 'skip
> distance' quite elegantly, second only to 6 mtrs, The transmission
losses
> at this frequency seen to be quite low, but if your out of the skip
distance
> , then even more power will not resolve the situation for semi local
> stations
>
>
>
> 'We' who live close to each other either get everything or nothing at
all,
> those who live a little further a field ,no pun intended, will receive
> nearly all stations on a regular basis..
>
>
>
> 'water water everywhere and not a drop to drink'
>
>
>
>
>
> >>>However...on 500kHz the receiving stations are where they are! If you
> want to work what you hear you must approach reciprocity of ERP,
> considerations of local noise floors aside.<<<
>
>
>
>
>
> The transmission losses at this frequency seen to be quite low, however,
> domestic generated noise levels appear to be distortional high, which is
> unfortunate, as the adage goes 'if you can here them, you can work them'
> may not actually stand up to investigation , path losses may not be
> reciprocal , and the noise floor at the distant station may well be
> significantly higher
>
>
>
> For example, the s-meter on my R5003 , is calibrated in sinpo units , 0 >
5
> , connected to my atu the receiver when in 'usb' (2.4 khz) reads a
> constant '3' on the meter uniform background noise. The same setup 0.5 / 1
> on 80 mtrs . It would take a significant increase to address this
situation,
> which I fear will exist at any 'urban' location.
>
>
>
> >>>>We shouldn't be afraid of the engineering needed to generate highish
> powers, nor feel that it's against the spirit of QRP to do so.<<<
>
>
>
>
>
> 25 watts looks to be a reasonable feed to a small system to reach
> something in the region of 100mW , For a lift of 'one' s-point @ 6dB
that's
> up to 100 watts and as can be observed during the many cw qso's signal
> outages look to be in the ratio of approx 3:1 20 seconds good signal in
> every 60 , one s-point is not going to decrease that by very much ! dx
> reports have been quite consistent , with good copy , , flutter replacing
> the deep qsb observed at 'close' range.
>
>
>
> May be we should regard this as a 'Digital band' in the true sense of the
> word ..
>
>
>
> G ..
>
>
>
>
>
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