[time-nuts] T-Bolt output harmonics
John Ackermann N8UR
jra at febo.com
Sun Aug 12 11:46:56 UTC 2012
Hi Grant --
I'd say you're doing OK; most frequency standards don't put a lot of emphasis on harmonic purity in the specs. Better than 45dB down is pretty good, and not much T&F gear is highly sensitive to harmonics.
I would *not* add a bandpass filter unless you really need to. Every tuned circuit is a thermometer, and inserting a BPF will increase the tempco of your system. If you absolutely need to reduce the harmonics further, it's better to do that with shunt traps at the harmonic frequencies. That way their tempco will have much less impact on the phase of the fundamental.
On Aug 12, 2012, at 12:25 AM, Grant Saviers <grants2 at pacbell.net> wrote:
> First post as a new owner & participant.
> I tamed the provided switching power supply noise with some L's and C's, and am now looking at the 10MHz output on a spectrum analyzer. Here is what I measured:
> 10MHz +9dbm
> 20MHz -50dbm
> 30 MHz -37dbm
> no obvious higher harmonics
> broad noise envelope at 60 > 75MHz @ -60dbm peak
> Are these results typical or might I have an adjustment or other problem?
> I've looked back about 6 months through the posts (is there a search function I've missed?) and not found anything except some 10MHz filter designs which I intend to try.
> Grant KZ1W
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