From: Rik Strobbe <Rik.Strobbe@fys.kuleuven.be>
To: "rsgb_lf_group@blacksheep.org" <rsgb_lf_group@blacksheep.org>
Date: Sun, 29 Aug 2010 10:21:43 +0200
Thread-Topic: CMSK indoor tests
Thread-Index: AQHLR1M2BZKs/USDyECB4maeOROhbw==
Message-ID: <BF4A524700075746A6467658DFC7102C63821D3C87@ICTS-S-EXC2-CA.luna.kuleuven.be>
Accept-Language: nl-NL, nl-BE
Content-Language: nl-BE
acceptlanguage: nl-NL, nl-BE
MIME-Version: 1.0
Subject: LF: CMSK indoor tests
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
Sender: owner-rsgb_lf_group@blacksheep.org
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org


Gary, Marin, LF-group,

after failing to decode Gary's CMSK8 signal last night, despite is was str=
ong, I did some indoor sound tests this morning.=20
I was running the PC in the shack as "transmitter" (on the speaker) and th=
e notebook in the livingroom as "receiver" (via the built in micrphone).
Setting TX and RX frequency both at 1000Hz and loud volume resulted in a=
 audible signal in the livingroom (not so much appreciated by the other fa=
mily members). There was a strong and clear trace on the CMSK waterfall di=
splay, but only partial decodes (estimated about 70%). Only after some fid=
dling with the fine tuning I got a 100% decode.
Once the tuning was optimized I reduced the "TX power" (speaker volume in=
 the shack) and remained to have good decode far beyond the level of an au=
dible signal. Quite impressive.
Leaving the audio levels unchanged I switched to ROS1 mode. I could see so=
me faint traces on the waterfall, but no decodes at all. I had to increase=
 the TX volume a lot before I got decodes on the notebook.
After that I switched back to CMSK and produces a strong 1000Hz "tune sign=
al" in the shack. Using SpecLab I measured the frequency at the notebook:=
 999.2Hz. It seems that the soundcard samplerates betweens both computers=
 differ 0.8% and the frequency difference of 0.8Hz was enough to make deco=
des fail, with weak signals.
At last I tested CMSK63 the same way I tested CMSK8. Setting the frequency=
 at 1kHz at both computers resulted in an immediate 100% decode. I could=
 go 5Hz off frequency before decoding failed. Then I reduced the audio lev=
el in the shack until decoding failed (having the both computers on the co=
rrect frequency). This time ROS1 outperformed CMSK63.

My conclusions of this tests:
1. CMSK8 can decode signals at SNR levels where ROS1 fails. It has the pot=
ential to be a very useful mode at 500kHz (and 137kHz).
2. CMSK8 tuning is very critical (must be better than 1Hz). The lack of an=
y AFC function and the fact that the slightest mouse movement over the wat=
erfall display causes a frequency shift of several Hz makes tuning very di=
fficult.
3. CMSK63 is far more easy to tune (as expected) and can be a very useful=
 mode for stronger signals (although still beyond the CW level).
The above conclusions are not meant to discourage the developers of CMSK,=
 I am impessed by it's possibilities and as I have written some software=
 myself I know that a lot of labor goes into this.=20
My respect and gratitude to ZL2AFP and Zl1BPU for this.
But some features such as AFC (no idea wether this is easy to implement)=
 and the possibility to zoom in at the waterfall display (should be easy=
 to implement) would make it much easier for the user to tune in at CMSK8=
 signals.

73, Rik  ON7YD - OR7T

________________________________________
Van: owner-rsgb_lf_group@blacksheep.org [owner-rsgb_lf_group@blacksheep.or=
g] namens Martin Evans [books@mollies.freeserve.co.uk]
Verzonden: zaterdag 28 augustus 2010 23:01
Aan: rsgb_lf_group@blacksheep.org
Onderwerp: Re: LF: ros -MF 502 K -on now-

I managed a couple of decodes, Gary, but it's much too critical to tune =
 at
CMSK8

Martin.

#######################

>
> I have to QRT now, I will continue tomorrow night & try faster modes.
> Thanks
> for your comments.
>
> 73,
>
> Gary - G4WGT.
>
>
> On 28 August 2010 21:40, Rik Strobbe <Rik.Strobbe@fys.kuleuven.be> wrote=
:
>
>> Gary, Martin,
>>
>> I have some other things to do for the next 30 minutes, I will switch=
 to
>> CMSK63 and see what appears on the screen.
>>
>> 73, Rik
>>
>> ________________________________________
>> Van: owner-rsgb_lf_group@blacksheep.org [
>> owner-rsgb_lf_group@blacksheep.org] namens Martin Evans [
>> books@mollies.freeserve.co.uk]
>> Verzonden: zaterdag 28 augustus 2010 22:33
>> Aan: rsgb_lf_group@blacksheep.org
>> Onderwerp: Re: LF: ros -MF 502 K -on now-
>>
>> Not just you, Rik - me too, and I guess some others, probably!
>>
>> Tell us how to do it when you find out.
>>
>> Martin GW3UCJ.
>>
>> ###########################
>>
>>
>> I had a good visual signal, but no decode. I'll try to figure out what=
 is
>> wrong.
>>
>> 73, Rik  ON7YD - OR7T
>>
>