Correction: URL for SM7PNV's products is https://www.zachtek.com. Thanks
N4ZR.
73, Dave K3ZJ
On Sat, Jun 4, 2022 at 12:32 PM K3ZJ David Siddall <davek3zj@gmail.com>
wrote:
> 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@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@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@kkn.net
>> > http://www.kkn.net/~k5tr
>> >
>> >
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>>
>
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