[A-DX] Shortwave Radiogram, 6-9 July 2018

[Roger]

Am 06.07.2018 um 15:18 schrieb Shortwave Radiogram:
>
> Hello friends,
> Last weekend’s experiment with 8PSK-125F and 8PSK-250F was generally 
> unsuccessful. This is despite improvements to the encoding and 
> decoding of these 8PSK modes in Fldigi 4.0.17. Most listeners’ reports 
> showed errors in the 8PSK text, while the MFSK 32 and 64 text 
> generally decoded 100%, as usual.
> Videos of last weekend’s Shortwave Radiogram are provided by Ralf in 
> Germany <https://youtu.be/SmIUPutbui0> (Saturday 1600 UTC) and Scott 
> in Ontario <https://youtu.be/0Hnc4-Z20NM> (Sunday 2330 UTC). An audio 
> archive is available from Mark in the UK 
> <https://1drv.ms/f/s%21Ah7fj9CZV0zynm_IejUWLKL2Ye4v>. And analysis of 
> program 54 was prepared by Roger in Germany 
> <http://www.rhci-online.net/radiogram/SW_Radiogram_2018-06-30.htm>(who 
> somehow managed 100% decode of the 8PSK modes).
>

1.) I had (at times) an SNR of over 25 db for MFSK32, which means: very 
strong RF signals.
2.) I receive simultaneously with 2 receivers from two different 
antennas. This antenna diversity is important for fast modes & against 
spacewave fading.
3.) As already stated at an earlier time point: It is more advantageous 
in PSK modes, due to the phase problem, to separately demodulate 
sidebands (SSB).
In the case of AM demodulation, MFSK modes are more advantageous and one 
has redundancies through the sum of both sidebands and no destructive 
interferences.

Presumably you also need hardware, which is suitable for DRM  (via IF 
output). The IC-R75 and the FRG-100 delivered over 34 dB SNR, with 
strong DRM-RF signals.
A Grundig S-650 never made more than 15 db SNR, even with local 
transmitter signals. Something is wrong here with his hardware 
architecture, internal phase noise or whatever.


roger