by Klaas Robers » Sat Dec 17, 2011 6:28 am
As far as I know, the Medium Wave practice was that there was no guarantee of neighbor channel reception. So if you are transmitting on a certain frequency, the neighbouring channels are not occupied by near by stations. So with a spacing of 10 kHz the AF bandwidth could be 9.5 kHz and the frequency band occupied 19 kHz (two side bands). I don't know in how far the BBC transmitters had that bandwidth available.
That is also the reason that the Baird TV transmissions were after midnight, when most MW stations had closed down. And yes, indeed the AF bandwidth of the Baird signal should have been about 13 kHz, so the dot resolution (vertical) was less than optimal.
Receivers in 1930 were mostly straight receivers, no superhets. So the bandwidth could be small or wide, all influenceable with the antenna coupling and the regeneration control. So square formed MF-filters with steep fall off edges were not common practice