and the results are in...

Well.... 3 hours of ten minutely data gathering done.


Results are.... interesting!


First the graphs:

And now the raw data:

time	ambient C	xtal C	diff C	10 min change C	freq Hz	relative drift over 10mins	total drift from power-on
09:30	23.4	27.6	4.2		0	0
09:40	23.8	28.2	4.4	0.2	727	0
09:50	23.9	29.8	5.9	1.5	737	10	10
10:00	23.9	31.1	7.2	1.3	754	17	27
10:10	24	32.1	8.1	0.9	761	7	34
10:20	23.9	33.1	9.2	1.1	771	10	44
10:30	24	33.8	9.8	0.6	777	6	50
10:40	24	34.4	10.4	0.6	784	7	57
10:50	23.7	35	11.3	0.9	790	6	63
11:00	23.6	35.3	11.7	0.4	793	3	66
11:10	23.5	35.8	12.3	0.6	797	4	70
11:20	23.4	36	12.6	0.3	801	4	74
11:30	23.4	36.2	12.8	0.2	802	1	75
11:40	23.3	36.3	13	0.2	804	2	77
11:50	23.3	36.5	13.2	0.2	807	3	80
12:00	23.3	36.6	13.3	0.1	808	1	81
12:10	23.3	36.7	13.4	0.1	810	2	83
12:20	23.3	36.8	13.5	0.1	810	0	83
12:30	23.3	36.8	13.5	0.0	810	0	83

So...

After 3 hours the temp seems to have stabilised out as does the freq, and the temp is lower than in previous tests.

Its still however showing better part of 100Hz drift over 3 hours from power on until it settles down.

Thats fine if you are going to be leaving the beacon running for days at a time, but if you are going to be turning on and off for  a few hours at a time thats going to get somewhat annoying. It also means that during warm up you could potentially end up crashing into someone elses signal.

Based on this, as I was discussing with G0CER yesterday, I think the trick here is NOT to switch off the beacon. (Duh!)   Yes I realise the licensing implications here, what I suggest is leaving it running 24:7, but when not present in the QTH to switch the output into a dummy load - that way no (in theory!) RF radiates beyond the boundary of the property whilst the beacon is unattended.


Im also now looking at active cooling - ie popping a heatsink onto the lid of the box and then running some PWM proportional to the temp into a fan to try and hold the temp at a lower constant temp - though as others have commented on the GQRP list - it would be better to address the electronic design first with negative co-efficient caps etc.


I think Ive gone about as far as Im going to go for now with thermal tests. The bottom end of 10m isnt exactly crowded with QRSS sigs, so I guess I can afford to let it wander a bit for now.

Next priority is actually getting a signal out - so Im just cutting a very hurried 10m Zepp to sling out for now. It will be horizontal pola and be strung up roughly north south. Expected main lobes should (fingers crossed!) be heading in roughly the right directions.


More later.
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