[RFI] led bulb test

[Greg Troxel]

Jim Brown <jim at audiosystemsgroup.com> writes:

> Thanks for posting this work. Several comments. First, the use of an
> SDR to look at spectra of the noise is a really good idea. I'm
> currently working on updates to the ARRL Handbook, and this is
> something I'm suggesting. The SDRPlay ($130) is a particularly good
> choice, because it has a very wide tuning range and can display a
> large chunk of spectrum at one time.

I have also been trying to make measurements, but so far just looking at
a PX3 hooked up to either an attic dipole or a proper outside antenna.
Operationally for me, if I can't hear the difference between on/off on
any band on either antenna, with a desk lamp in the shack, it's good
enough.  But I'm starting to try to do this listening on closed bands;
my 80m noise level is vastly lower midday than evening, which I suspect
is typical for relatively quiet locations.

It seems that for repeatable quantitative measuremnts, one wants a Line
Impedance Stabilization Network and a spectrum analyzer, but this is at
best $2K.  I have borrowed a LISN (which is large and heavy) and intend
to hook it up (with at least a 20 dB pad) to a KX3/PX3.  That's not a
proper SA, but should be pretty good within the ham bands.

So I wonder if you are able to suggest (for the Handbook) how to
approach repeatability without buying or homebrewing a proper LISN.
Also, it would be good to discuss rough calibration of things like the
SDrplay to get measurements that are plausibly close to using real lab
equipment.

I say all this realizing that the audience includes people with varying
technical backgrounds and budgets.

But overall, with some repeatability and rough calibration, it should
then be reasonable to build up a web database of results.   It seems
like the hard part is the LISN equivalent.  Perhaps that would make a
good kit, or perhaps I'm overestimating the parts cost/hassle.

73 de n1dam