Surely, the whole point of all this, is that WE ARE Amateur Radio
experimenters. Few of us are in an ideal situation to carry out
laboratory standard experimentation or even with professional resources
and real estate at our disposal. However, this may also be said to be
true of the early experimenters who also did not have these resources.
They suffered under the handicap also that there were no rules to refer
to and little reference material upon which to build their knowledge.
Yet, they did achieve remarkable results and adapted their techniques
and technology to reflect the constraints. I don't remember my earlier
education or later experience ever defining an amateur radio QSO as
being one that had to be conducted in a particular mode or by way of a
particular signalling system for technical rather than licensing
reasons. Without the development of new and novel technology whether it
be software or hardware we have great difficulty in justifying our
occupation of valuable spectrum. Or, is it all just a frivolous sport in
which grown men shout into microphones or press switches just for the
sake of collecting more coloured postcards than the next man?
I wonder if we might start, conduct and enjoy 2012 as a year of
tolerance and understanding. This is a HOBBY. Happy New Year.
73
On Tue, 2012-01-03 at 14:03 +0000, mal hamilton wrote:
> This is NOT the case at my QTH. The signal over noise is excellent
> because I live in a QUIET location S9 signal with virtually no NOISE
> from the large antenna.
> Why do commercial receiving stations use large antenna farms out in
> the countryside ?? They do not use ferrite sticks or micro probes
> If you have always lived in an Urban environment with lots of noise
> then you do not understand what I am talking about.
> Go out into the countryside, put up a large antenna array and compare
> it against pocket size antennas, then you will be in a position to
> comment.
> If International commercial and coastal receiving radio stations could
> use Ferrite sticks, micro probes they would not go to the vast expense
> of installing large wire arrays.
> Out in Rural areas large antennas equals big gain and very little
> noise whereas in Urban areas what ever sort of antenna you use there
> is likely to be a noise problem.
> One other point at my QTH there are no overhead wires in the immediate
> vicinity nor as far as I can see looking for miles across the
> countryside to cause noise pollution.
> A large antenna at your qth might capture more noise than signal,
> hardly the place to live for a LF experimenter!!
> g3kev
>
>
>
> ----- Original Message -----
> From: Stefan Schäfer
> To: [email protected]
> Sent: Tuesday, January 03, 2012 12:51 PM
> Subject: Re: LF: Antennas
>
>
> Hi Rik,
>
> Am 03.01.2012 13:38, schrieb Rik Strobbe:
> > Depends on how "gain" is defined. Larges antennas pick up
> > more signal, but also more noise.
> > It is the signal to noise ratio that is important, and this
> > is no better than with smaller antennas.
> > With a large antenna a signal will be S9 and noise at
> > S7. With a small antenna
> > the same signal will be S3 with noise at S1. In both
> > cases SNR is the same.
>
> This is exactly the thing that he never will understand. Often
> discussed and somehow logical, anyway. This is why he says
> that a small antenna is worse, since he runs a RX that needs a
> high signal input level. Thus a small antenna, e.g. a ferrite
> antenna without a suitable preamp, gives poor results....
>
> 73, Stefan
>
>
>
> >
> >
> > 73, Rik ON7YD - OR7T
> >
> >
> > ____________________________________________________________
> > Van: [email protected]
> > [[email protected]] namens mal hamilton
> > [[email protected]]
> > Verzonden: dinsdag 3 januari 2012 11:57
> > Aan: [email protected]
> > Onderwerp: Re: LF: Antennas
> >
> >
> > Like you say with the larger antennas Attenuation is needed
> > there is so much more gain over the smaller variety.
> > My antennas both on LF es MF have attenuation control to
> > reduce the gain, a good position to be in I suppose.
> > g3kev
> >
> > ----- Original Message -----
> > From: Rik Strobbe
> > To: [email protected]
> > Sent: Tuesday, January 03, 2012 10:48 AM
> > Subject: RE: LF: Antennas
> >
> >
> > Hello Doug,
> >
> > over the past decade I have tested small loop
> > antennas, a miniwhip (PA0RDT) and a
> > "big" transmitting antenna for receiving purposes
> > and found that each of them has its own
> > advantages, as well on 137kHz as on 500kHz.
> >
> > Loop antenna
> > Advantages:
> > - very frequency selective, can be useful
> > to attenuate broadcast
> > - 8-shaped pattern can be useful to null out QRM
> > sources
> > - if large enough you don't need a pre-amp
> > - you can move the loop around your property to find
> > the best (now noise) location
> > Disadvantages:
> > - not omnidirectional, so you might need to rotate
> > the loop
> > - single band antenna
> >
> > Miniwhip:
> > Advantages:
> > - broadband, can be used from (V)LF to HF
> > - omnidirectional
> > - you can move the loop around your property to find
> > the best (now noise) location
> > Disadvantages:
> > - pre-amp (built in), so you need to feed it with
> > a DC voltage. This has to be done with some care
> > as it can introduce QRM.
> > - broadband so your RX needs to be able to handle
> > the all signals. Can be solved by a BPF in front of
> > the RX.
> >
> > "Big" TX antenna (Marconi):
> > Advantes:
> > - readily available if you also TX on 137/500kHz
> > - no TX/RX antenna switching if you also TX on
> > 137/500kHz
> > - no pre-amp needed (in
> > contradiction, often you will need an attenuator).
> > - some frequency selectivity, but not as good as a
> > loop
> > Disadvantages:
> > - big, often not worth the effort if you only want
> > to RX
> > - cannot be moved around to minimize QRM
> >
> > Conclusion:
> > If you have a TX antenna and the local QRM
> > is not too bad you can use it as RX
> > antenna, so no need for an additional RX
> > antenna. If you use a loop RX antenna it should be
> > at sufficient distance from your TX
> > antenna, otherwise it will pick up all the QRM from
> > the TX antenna. I did not notice that effect with
> > the miniwhip.
> > If you want to RX only a loop or miniwhip seems the
> > best (most economical) option.
> > I compared the miniwhip and my TX antenna on many
> > occasions and could not notice a
> > significant difference (as RX antenna).
> > During the winter 2010-2011 Canadian and
> > US beacons were copied regulary with good
> > (audible) signals on 500kHz.
> >
> > 73, Rik ON7YD - OR7T
> >
> > ____________________________________________________
> > Van: [email protected]
> > [[email protected]] namens Douglas
> > D. Williams [[email protected]]
> > Verzonden: maandag 2 januari 2012 22:53
> > Aan: [email protected]
> > Onderwerp: Re: LF: Antennas
> >
> >
> > Mal, you lost me on this one. Are you suggesting I
> > (or we.....here in North America) erect large
> > verticals, inv L systems, Rhombics, and V beams in
> > order to receive EU LF signals?
> >
> >
> > I thought I was doing pretty well with my micro RX
> > antenna!
> >
> >
> > Doug KB4OEr
> >
> >
> >
> >
> > On Mon, Jan 2, 2012 at 6:28 PM, mal hamilton
> > <[email protected]> wrote:
> > LF es MF
> > Reports from across the pond
> > and other DX locations as far as Tenneesee
> > and Kansas using micro probe antennas
> > are great for QRSS speeds but not suitable for
> audio reception.
> > Take 160 metres for example where it
> > is normal
> > to work world wide on cw but antennas in use
> > are large verticals, inv L systems, Rhombics
> > and V beams, therefore to have any chance
> > of receiving signals at audio
> > level on LF or MF large antennas of
> > the calibre used on 160 metres are
> > necessary.
> > As well as TX at this QTH
> > I also use large arrays for RX
> > and often hear signals from
> > NA that would not be audible with small
> > loops, micro probes or ferrite sticks
> > Recently on 500 I was able to copy a W stn
> > 579 but a DL stn copied only on screen, when
> > I asked what strength the signal was
> > I got no reply!!!!!!!!!!!!! using a
> > micro probe antenna.
> > If a proper large antenna system
> > is not used on LF es MF then there
> > is virtually NIL chance of an audio
> > report from across the pond for EU stns
> > es vice versa
> > Back some years ago I had audio reports from
> > the Boston area but the antennas were
> > proper wire arrays as used on 160 metres
> > Small hand held antennas are fine for High
> > Power BC strength signals but not for low
> > power amateur signals to be heard
> > No commercial LF/MF station would
> > even consider an antenna of the micro
> > variety.
> > When I was in the business some years ago on
> > LF/MF Rhombics and V-Beams were the norm
> > de mal/g3kev
> >
> >
> >
> >
> >
> >
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