Every year I try and listen to the BBC Antarctic Midwinter Broadcast. It’s become a bit of a tradition to sit back with a whisky on the rocks and enjoy this unique program that is broadcast by the BBC World Service.
The broadcast was made on 3 frequencies; 7305 kHz from Ascension, 9505 kHz from Woofferton and 12065 kHz from Woofferton. This year I chose to listen 12065 kHz as it had provided the best reception for me during the recent test transmissions and although 9505 kHz was strong, there was very close co-channel interference for several DX stations.
I also made the effort to record the broadcast using my main HF amatuer radio equipment; an Icom IC-7610 that has an interesting party trick. You can use the 2 separate receivers in the 7610 to listen on the same frequency using 2 completely filtering and antenna paths. In this recording I used a ZS6BKW mounted at 20′ AGL running East to West on the main receiver and a Wellbrook ALA1530LN active loop mounted at 8′ AGL on a rotator adjusted for maximum SNR (running NW to SE) on the sub receiver. The result is a kind of pseudo diversity where you can hear the signal move between the different receivers as the polarization and propagation changes. The left channel in this recording is the main receiver (ZS6BKW) and the right channel is the sub receiver (Wellbrook ALA1530LN). I strongly recommend you listen with headphones to enjoy the full effect.
The only post processing I have done is some normalization on the 2 channels to match the volume as the sub receiver on the IC-7610 is a little quieter than the main receiver. This is not an issue in real time as I just adjust the volume on the receiver to match but the built in recorder takes the audio at a preset level and requires a slight boost in post. The RF gain on the main channel was reduced to match the noise floor of the sub channel as the Wellbrook loop picks up much less noise then the ZS6BKW.
Beware of the tuning tone at the start of the broadcast, it’s loud!
I would be very interested in hearing what you think of the recording. Did you notice the signal moving from one side to the other? Which antenna do you think did a better job of receiving? Leave a comment and let me know!
Matt, fantastic recording. The pseudo diversity was very novel, the rolling shift from left to right & peaking in the centre of the sound field was very noticeable.
In times past I can see how this broadcast brought great cheer to those overwintering & the tradition still has value.
Great comments Ian. As far as I know, the station crew still gather around the AM radio and listen to the broadcast. Hard to imagine spending so long in darkness!
Excellent Matt. Well done mate.
Thanks Nigel. I think it was worth the effort setting it up for recording!
what fun! visiting your site after reading about your recent conversation with the ISS, via the Daily Mail. Best wishes, Cape Cod USA