[CQ-Contest] Is better antenna isolation also diminishing antenna azimutal pattern distorsion?

Sat Jun 4 12:32:53 EDT 2022

Kari,

To compare antennas (or combinations of antennas) etc. in real time, WISPR
is far superior to any other method I have ever used.  Two or more WISPR
transmitters, started simultaneously, will give you as close to
simultaneous signal strengths from near and far as you will ever be able to
get.  For comparing more antennas than available WISPR transmitters, or
with filters, etc., compare against a reference antenna system.

I described this method with some basic examples in the June, 2020 CQ
Contesting column, posted with permission of CQ Magazine here:
https://tinyurl.com/55kunn2j.  While at that time I found SOTABeams
WISPRlite units to be ideal for this purpose, they do require constructing
filters (kits for which are available) for use on the multiple contest
bands.  I changed to using multiband units for 80-10 meters that also
include GPS, and coincidentally come from your country.  These are
 Zachtech WSPR desktop transmitters from SM7PNV (www.zachtech.com).

Analyses based on the resulting data are almost unlimited and always
interesting.

73, Dave K3ZJ

On Sat, Jun 4, 2022 at 7:58 AM SM0HRP <kari at sm0hrp.se> wrote:

> Hi George,
> Thanks for the inputs. I was a little unclear with "150 km" to other RBN
> stations. I meant RBN spots readings from dx stations (USA, Japan..) of my
> station and nearby stations.
> I agree with what you say about things getting complicated. It is a
> difficult issue.
> One thing I thougt, not so difficult to do, was to compare RBN sigs in EU
> and US when I switch between no Bandpass filters (= 25-40 dB isolation) to
> Bandpass filters in (= 85-95 dB isolation). Assuming stable signal
> conditions of course.
> Unfortunately I cannot measure antenna plot signals further away than some
> 100 meters. My QTH is an old island.
> A great thing to do would be to measure the vertucal antenna plot pattern
> with a drone like Tom N6BT did in measuring the vertical antenna pattern on
> sloping terrain.
> Wishing you all a good weekend.
> 73s Kari SM0HRP
>
> Skickat från min iPhone
>
> > 3 juni 2022 kl. 18:52 skrev George Fremin III <geoiii at kkn.net>:
> >
> > On Fri, Jun 03, 2022 at 02:30:52PM +0200, SM0HRP Kari Gustafsson wrote:
> >>
> >> Issue: Antenna isolation measures reveal that my antennas couple
> strongly
> >> about - 30-40 dB without any filtering. But I have invested in high
> power
> >> bandpass filters to get down the harmonics under S7 on all bands.
> Comparing
> >> my RBN spots with nearby "smaller antennas" close to my QTH (some 150 km
> >> away) I have experienced worse antenna strength signals into many
> >> directions.
> >
> >
> > RBN data with stations 150 km (or even closer) will likley not produce
> > very good data.
> >
> > At any distance from your station - and even different height antennas
> > at your location can produce very differnt signal levels second to
> > second.  The ionosphere changes all the time and signals generated an
> > different locations or even at diffrent arrival / takeoff angles will
> > vary in signal level a great deal over time.
> >
> > You would need to run these tests for some much longer periods of time
> > with a lot more data than any RBN system will give you.
> >
> > I have seen wild variations even on what I would think is a short line
> > of sight path.  I have a nearby ham that is about 5 miles or so away.
> > This path is line of sight.  So I thought I could compaire my two 40
> > meter yagis.  During the day I tired to do this with him.  But just a
> > steady carrier out of one of my antennas had fairly large QSB at his
> > reciever.  I was very surprised. I am guessing that there were
> > multiple modes of propagation between us that was causing this QSB.
> >
> >
> >> How do you contesters perceive these kind of antenna isolations issues
> on
> >> big Christmas Tree stacks? Anyone been trying to solve antenna patten
> >> distortion issues like this and what are the lessons learned?
> >
> > I am sure you could try to measure all of the interactions between
> > antennas but I would think that in many cases it would be hard.
> > Sometimes they are obvious and I suspect that many times it would be
> > very hard.  I know some station owners try to do all sorts of little
> > things to get the last little bit of perfromace out of their systems
> > (ie. K3LR).  It would be interesting to know if he has tried to figure
> > out the things you are talking about at all or even a little bit at
> > this station.
> >
> > For me - I try to do some things - like not have antennas / towers
> > directly in front of other antennas for key beam headings.  The tower
> > locations were thought about a long time before holes were dug.  For
> > most of us - you can not solve this for all beam headings unless you
> > were to put up arrays that all point away from eachother for most or
> > all beam headings.
> >
> > I guess you could take it all down - including the towers and put up
> > one system at a time and figure out how to do signal measurements that
> > you can prove you can repeat excatly every time you do them and then
> > redo them wiht each change in your station.
> >
> > I think for most if not all of us this is impractal.
> >
> > Computer models have gotten good but I suspect that modeling an entire
> > station such as mine or enen yours might be very hard to do.  The
> > variables get out of hand quickly.
> >
> > As a result, I and many others make choices that are compromises.
> >
> > For me, they are things I know could or might be better - but due to
> > cost constrants or space constrants the only way I could have the
> > 'perfect' is not have the 'good'.
> >
> > I recall years ago a ham posting on Tower Talk or maybe here on
> > CQ-Contest something to the effect of:
> >
> > "I have a 2 element 40m yagi, but I can only get it up 50 ft.  Since I
> > know that is too low to be any good on 40 meters I have not put it up
> > and it is in the box in my garage. And, no it is not for sale."
> >
> > And all I could think is - that is silly.  It will work at 50 ft.
> > Maybe not as well as say 150 ft but it will work much better at 50 ft
> > than it will sitting in the box in the garage.
> >
> > YMMV
> >
> > --
> > George Fremin III - K5TR
> > geoiii at kkn.net
> > http://www.kkn.net/~k5tr
> >
> >
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