[Moon] [Moon-net] Question RST vs S/N on EME

[Oene]

Hello All,

Thanks All for your replies on my question and from what I have
read it is indeed a fact that on the higher bands the S meter really
swings up and can get to very strong reports, like Dominique and
Joe mentioned.
On 144 Mhz the situation is somewhat different and a more indicative
situation is used rather then the real S meter readings.
With preamp switched on and noise moving the S meter already o
n S5 is no inication for real reports.
As Gerald stated that -20 dB is a reference as S0 and taking steps
of 3 dB each S unit seems a good solution and is more or less the
same as in the link I got from Dave
http://www.zen70432.zen.co.uk/Initials/g3sek_op_proc.pdf

This PDF by Ian is a result of the Prague 2002 EME meeting and
gives a standard for those RST reports in cw eme.
However it is stated for 70 cm and up, it seems to me very usefull
also in 2m eme.
For real comparision the method used in WSJT and what Russ
mentioned is a good way to compare things, using the dB measurement
report.
But that might be from a technical aspect rather than the use as a
report for communications aspects, in which an indicative report
is sufficient.
That signals off the moon can get very strong I heard on the
recording of Harm in which his own echoes were being heard.
This recording seems to me as a real 559 signal and compared
with some tropo beacons with their S meter readings this is not
far from the thruth.

My conclusion is that using the 2002 guide is a good base and
yesterday I used this guide in sending a report to Ivan RA6AX
when he responded to me in CW.
I gave him a 559 signal because it was for eme sigs very strong
and I think this is the best report I ever can receive with my current
setup.

Thanks for all who responded and their contributions !!

I wish you all a good weekend and GD DX with BIG RST readings :-)

Vy 73 Oene
PA3CWN



----- Original Message ----- 
From: "Oene" <pa3cwn at tele2.nl>
To: "Moonnet" <moon-net at list-serv.davidv.net>; "Moon" <moon at moonbounce.info>
Sent: Wednesday, April 16, 2008 8:22 PM
Subject: [Moon-net] Question RST vs S/N on EME


> Hello All,
>
> I have a question about RST reports and S/N signals in dB.
> Often I hear CW stations giving a RST report to each other
> and always have my doubts about the reports.
> Is it possible to really RX an EME station with 589 in case
> of a moderate 4 yagi array on 144 Mhz ?
> In the article about system temperature by Doug VK3UM I saw
> that the sky temp on the higher bands 70 cm and up were much
> lower and I can imagine that signals can get huge on i.e. 23 cm,
> but I never heard an EME signal than on any other band as 144 Mhz,
> so I have no idea of those higher bands, but maybe one of the
> gentlemen on 23cm can tell me more about signal strenghts on those
> bands.
> When listening to signals in JT65 mode, I never have heard/seen
> a station stronger as -4 dB  except for Graves Radar which was + 3 dB.
> Or in CW I have never heard a station stronger as + 3 dB S/N 2500Hz Bw,
> but more likely sigs get almost never above 0 dB S/N @ 2500 Hz BW
> I used the page by Gaetan ON4KHG as reference linked at
> http://home.versateladsl.be/cesgai00/new_page_1.htm
>
> I did some reading and found that S1 on 30 Mhz and above is stated
> as 0.02 uV at 50 Ohm ,  or -141 dBm ( It is not said what BW is used,
> but I think it is 2500 Hz as reference)
> S0 or noise floor would thus represent -147 dBm.
> If I want to listen to my own echo  and use 1 kW (60dBm) in a 18 dBd
> system and take the EME path loss on 144 Mhz as 251 dB  my calculation
> would be as follow:
> 60 dBm  +  18 dB  -  251dB + 18 dB  =  -155 dBm.
> My signal would be 8 dB below the noise floor  when listening to my own
> echo and all polarization would be perfect off course.
> When listening to the -8 dB file on Gaetan his homepage this is about
> the way I hear my echoes at their best moments.
>
> When I would hear my echoes at 579 which is -105 dBm I would have
> to get an extra 50 dB more !     In case of very large arrays with 30 dBd
> instead of 18 dBd this would give only 24 ( 2 x 12dB) extra, so the rest
> is only possible by raising the power to levels of ......
>
> The JT signals however seem to me quite close to the truth and the
> +3dB I saw on Graves compared to the +3dB sound file of Gaetan
> seems pretty close to my experience.
>
> Off course the signals become a better S/N ratio as BW is narrowed,
> and in case CW in reduced BW this is completely true.
>
> But I always have that strange feeling that 5x9 reports are not real and
> maybe a 519 or 529 would be maximum.
>
> But maybe I overlooked a big deal and made calculations far too easy
> and is it a more complex matter, but therefore I want to know ?
>
> As stated. I took 144 Mhz as base, but I am very interested from higher
> bands operators too what their experiences are, both CW and JT65
>
> One question: Pse respond openly to Moon and Moon-net.  so everyone
> can follow the thread.
>
> Vy 73 Oene
> PA3CWN
> JO33ah
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