30-12-2016, 10:06 PM
(30-12-2016, 08:26 PM)Crackle Wrote: My initial thoughts were, did it matter too much if the fundamental frequency was not a multiple of 9, so long as one was not using a synthesised tuner which has the channel separation fixed.
Nothing to do with synthesised tuners, Mike.
Let's say you have a crystal which is 1kHz off a multiple of 9. You set up your little transmitter and all is fine. But there is a 200kW transmitter on the authorised channel. You are well beyond the ground wave coverage, so not a problem - until night time, when you start to receive the sky wave.
Your receivers will now see two signals and mix them together to generate the sum and difference products: f1 + f2 and f1 - f2.
The sum, we aren't interested in, but the difference, 1kHz will appear in the output of your receiver(s) in addition to the programme material you wish to listen to.
Obviously, being an exact multiple of 9 is not all that is important as it mustn't be a channel used by a local transmitter!
Crystal harmonics are perfectly OK. In which case is the multiple that should be a multiple of 9.
