Hi Graham
At last a man that knows what he is talking about because he has been able
to compare a large antenna as described in a low noise environment ie Big
signal capture and little or no noise. This compares with my findings.
It is unbelievable the difference that a large antenna makes in the right
place for weak signal reception compared to the pocket ferrite rod and
uProbes
The problem is Graham that those critizing the most have never handled large
antennas of the kind I have previously described and especially in a
suitable location away from Urban noise pollution.
Your installation at GB4FPR sounds ideal with the big Delta loop positioned
over sea water at around 100 ft high. My situation is similar but instead of
sea water I have open fields. I can hear the Beacons to which you refer
strong all day long and on 137 can Hear OH1TN to my NNE and IK5ZPV SSE all
day long when active and work them two way on CW. Also when the Russian stns
are active on 137 I can Hear them during the early afternoon time when it
is still daylight.
73 and tnx for yor constructive contributation concerning the antenna
discussion. I have not yet worked a DX station on 160m CW that received me
on a pocket antenna.
mal/g3kev
----- Original Message -----
From: "Graham" <[email protected]>
To: <[email protected]>
Sent: Tuesday, January 03, 2012 3:18 PM
Subject: Re: LF: Antennas
> Have to side with Mal on this one
>
> From my experience with the 600 Ft , balanced, delta loop, 200 ft
per
> side and the 750 foot long wire at GB4FPR , yes Rx signals
where
> significantly higher than at my home qth
>
> The DL beacons 505 could be detected most of the day and Andys
CW
> / PSK beacon was at S7 and caused many 'hush who's calling us'
> incidents , when it keyed after a cq call
>
> But as the sandstone fort is surrounded by sea water most of the
> time and the loop is some 90/100 feet up , the wire stretched over
> the sea to the lighthouse and used the loop as a counterpoise .. yes
> RX noise was very low ..
>
> Now static build up on the arrays from the wind (ozone ?) now that's
> something that has to bee seem rather than experienced ..
>
> HNY Mal
>
> G..
>
> --------------------------------------------------
> From: "mal hamilton" <[email protected]>
> Sent: Tuesday, January 03, 2012 2:40 PM
> To: <[email protected]>
> Subject: Re: LF: Antennas
>
> > You are taking about Military and 007 Bond pocket Zappers, I am talking
> > about Commercial LF/MF/HF installations including Coastal stations.
> >
> > g3kev
> >
> > ----- Original Message -----
> > From: "Andy Talbot" <[email protected]>
> > To: <[email protected]>
> > Sent: Tuesday, January 03, 2012 2:22 PM
> > Subject: Re: LF: Antennas
> >
> >
> > What commercial receiving station is listening to frequencies below
> > 2MHz regularly?. And of course thay have large arrays; they need
> > beam steering, real seripus gain and a capability to generate nulls on
> > jammers.
> >
> > Although, having said that, all modern HF DF / Intercept kit now makes
> > use of phased arrays of multiple small air loops (< 1m square). Which
> > gives better results and is instantly reconfigureable, capaple of
> > adaptive and blind null steering, and can even separate two or more
> > signals on the same frequency.
> >
> > And yes, I have worked on these modern of HF Intercept and DF
> > facilities and know their capabilities. Mostly military, rather than
> > commercial though, and the arrays were rarely bigger than 100m
> > linear dimensions and no higher than head height. Take a look at the
> > Baldock setup. I think its in the public domain, somewhere.
> >
> > Andy
> > www.g4jnt.com
> >
> >
> > On 3 January 2012 14:03, mal hamilton <[email protected]> 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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