micro UHF transmitter schematic diagram - RF Cafe Forums
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Post subject: micro UHF transmitter schematic diagram
Unread postPosted: Tue Jan 18, 2005 10:10 am
Joined: Tue Jan 18, 2005 9:41 am
I need schematic diagram of micro UHF Long Distance transmitter (bug), frequency near 398Mhz-400Mhz, PLL-quarz controlled, distance near 300m or more, battery life about 5 days, Power: cell tablet CR2032(3V) x 1PCS or CR2450 (3V) Li. SMD design. Could someone help with schematic?
I even find some schematic:
but it requires a some improvement, i.e:
1) Only one AF stage should be enough for this
2) The problem with this setup is that it can't produce wideband FM,
usable at the RM radio band (75KHz swing).
3) The second problem is that to produce UHF signal with this method
you require a large number of multiplying stages which will need to be
aligned (tuned). Alignment can be very touchy mechanically and a fall
on the floor can de-tune the trimmers. It is not a very practical approach,
but it does work.
4) Another problem with a large number of amplifier stages is that
a intermediate signal can feed through to the output stage. This makes
the usual filtering with LPF unpossible (since signal is under the carrier
What I would like is to improve this schematic in view of the mentioned suggestions.