On 12/25/2020 7:49 PM, Bob Turner wrote:
The metal case looked promising for keeping RF inside the unit.
Shielding (or the lack thereof) is a poor predictor of RFI performance,
especially at HF. Rather, noise is coupled to wiring to the noise source
and radiated by it. Likewise, RFI to victim equipment is received on
wiring connected to it. In cases, coupling to/from that external wiring
is the result of simple (and serious) mistakes right at the point where
the external wiring is connected.
In this situation, the victim's external wiring are our intended antennas.
So far its quiet on HF. I have not tuned from 6m to 23cm. The leads
from the source/ps to the load and LED light are 6 inches long at the
moment. No noised noticed on HF with a cursory tune up the bands.
Of course it's quiet on HF -- that external wiring isn't close to being
long enough to be an antenna at HF!
Next step is longer leads to the load.
Yes. AND to connect it to something that draws rated current with wiring
long enough to be at least an electrically "short" antenna on the bands
where you're listening. AND at a QTH where there's little noise from
sources in your home and in the homes of your neighbors. In most cities,
suburbs, and even small towns, it's common for there to be several dozen
noise sources -- I live in the mountains with nearest neighbors about
500 ft from my antennas, but I often have very strong noise from homes
in three different directions that clobber fairly strong signals.
My RFI tutorial has lots of detailed advice for learning whether a piece
of equipment is noisy.
http://k9yc.com/KillingReceiveNoise.pdf
http://k9yc.com/KillingRXNoiseVisalia.pdf
NK7Z's website has a lot more.
73, Jim K9YC
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