|5MHz Homebrew Oscillator|
Because my intentions is to use it as an external oscillator if it proves to be effective at eliminating the Beacon drift, I have made it as small as my abilities (and keeping with my overall goal of building very small projects).
|Oscillator Schematic via CircuitLab|
The selected circuit is much like the 9volt battery oscillator that I use for Marker Oscillators (see many of my previous posts), except even smaller.
|Oscillator on Six Pin Header|
Initial tests indicate my HB oscillator has little or no "hash", which is much less than that of the attempted use of the Master Clock (see previous post).
|Mast Clock signal on left (with it's Hash)|
My Homebrew Oscillator on the Right
Currently my oscillator is "hanging out" in the air on wire legs, and subjected to air currents and local temperature change that effect frequency (as with most crystals).
I inserted a 60 second delay between test transmissions, similar to a normal Beacon schedules.
|Stability After an Hour|
For this test the room temperature is 72.6F, the HB oscillator is 78.2F, and the Propeller Processor is 81.6F.
Future tests with WSPR will verify short term stability.
I think this proves that the short term stability of the Propeller Beacon during transmit; is due to heating of the internal oscillator from within the Propeller chip.
A low noise external oscillator should provide a stable RF Frequency for use with low band-width Beacons.
I need to find an commercially available Temperature Compensated Oscillator (TCXO). Or, a cheap Oven-Controlled Oscillator (OCXO). Or, package my Homebrew Oscillator for my permanent use with the Propeller.