23-08-2015, 12:15 PM
I designed a higher power crystal-controlled MF 'modulator' that appeared in the Autumn 2000 BVWS Bulletin and published it under a pseudonym. That certainly has a far greater range and could be tuned up into a variety of antennas! The circuit isn't much more complex than the MiniMod.
The advantage of crystal control is that it can easily be fine-tuned up to within a few Hz of an MF channel, removing (almost) any co-channel heterodyne. The disadvantage is that a MW frequency crystal can cost up to £30 to have made!
Of course there are various alternatives using synthesizers or mixing, but I think it's debatable whether it's worth the complexity for radiating a few milliwatts.
(There is or was a commercially available 'pantry transmitter' that used a synthesizer circuit first published by the Medium Wave Alliance...)
Anyway, there are many, many designs for these devices, all giving decent results.
Ian
The advantage of crystal control is that it can easily be fine-tuned up to within a few Hz of an MF channel, removing (almost) any co-channel heterodyne. The disadvantage is that a MW frequency crystal can cost up to £30 to have made!
Of course there are various alternatives using synthesizers or mixing, but I think it's debatable whether it's worth the complexity for radiating a few milliwatts.
(There is or was a commercially available 'pantry transmitter' that used a synthesizer circuit first published by the Medium Wave Alliance...)
Anyway, there are many, many designs for these devices, all giving decent results.
Ian
