[A-DX] VOA Radiogram, 30-31 May 2015, includes SSTV

[Roger]

Am 16.06.2015 um 14:02 schrieb VOA Radiogram:
> Hello Roger,
> Thank you for this report.
> Attached is the gallery.
> With your IF recordings, you might be able to help us determine if SSB is better than AM for decoding the modes, or if there is no difference.
> All the best,
> Kim


If the radio reception is good, then there is no difference. But, on 
shortwave are interference and fading,.
For each situation, the type of demodulation needs to be adjusted. There 
are many "if" and "but".
The VoA sends in AM - that means two times the same content. This is an 
error protection of 100%.
This redundancy is very good at selective fading, then only one sideband 
is affected. However, the carrier may also be deleted.
Therefore, the answer is quite logical:
Not "AM" or "SSB" is ideal, but "DSB" [simultaneous LSB + USB]
BUT: it is important here: You have to be on the HF frequency 
accurately, so that the two AF sides fit exactly over each other.

If you get QRM from one side, then I change the AF bandpass to one side. 
In "extreme case" then you have pure LSB or USB.
This means: In a QRM situation LSB or USB is superior to normal AM.

In Studio1 I can use with AM signals three different ways of demodulation.
- "AM" - then I use the external carrier.
- " DSB - then I use the internal carrier of the software to demodulate 
both sidebands simultaneously.
-    "S-AM - here the software tries to set the internal carrier with 
the correct frequency and phase abovethe external carrier ..
Usually here you have the best sound - for human ears.
But FLDIGI is irritated by these synchronizations, especially if there 
are a blurred carrier, caused by scattering phenomena.


In STUDIO1 I can make the bandpass variable. This ability makes possible 
"half AM" or half "S-AM ', but also double SSB, DSB called ......

roger


report for 2015-06-13    VoA Radiogram:
http://www.rhci-online.net/radiogram/VoA_Radiogram_2015-06-13.htm#VOA