[G0HZU_JMR]

I mentioned earlier that I might try the MMIC on a heatsink to see if it improves the warmup. I tried this today when listening to the football and the initial results are quite good I think. I changed the MMIC to a low noise low power device that runs at about 15mA. I also used an air cored inductor and I mounted the MMIC direct onto a fairly thick tinned plate and this was screwed onto a heatsink.

On a thermal camera the MMIC warms up and stabilises in just a few seconds now. Before, when it was fitted to a regular/skinny PCB, it would take ages to thermally settle on the camera. With the current setup with the heatsink I've mounted it as if it is a high power device so it achieves thermal stability really quickly at just 15mA at 4.5V.

I left it a long time to cool off and the plot below is a warmup plot and the scale is 50Hzdiv and the x axis is time in seconds. The plot misses the first 1 or 2 seconds because the counter has to be gated before I can start my logging SW. However, the oscillator drifts down maybe 400Hz in just over 1 second from cold and then stabilises as in the plot below. I think I can get it better than this and the slow drift upwards can be improved with a better heatsink. As it stands I suspect that this would be useable in a receiver as it is very stable after maybe 5 or 6 seconds. At 5MHz instead of 10MHz the gradual upwards drift would hopefully be halved.