I'd suspect either the charger itself or the batteries are going west, if you
didn't have the noise on 20 m. before and now you do and you traced the noise
on 20 m to the charger/computer assembly.
I have two battery chargers going all the time in my garage. One float
charging a Honda emergency generator battery and the other float charging my JD
tractor battery. If I walk up to them with a two meter walkitalki I can hear
noise, but they do not cause noise in my HF equipment, my next door neighbors
dimmer light gizmo does.
In your case, I'd suspect those batteries are failing, but you have the luxury
of unplugging them and no more noise.
73
Dale, k9vuj
On 25, Jan 2013, at 20:15, Greg Troxel <gdt@work.lexort.com> wrote:
> [This is partly observations in case it helps someone else and partly a
> query.]
>
> I have an attic-mounted fan dipole for 40/30/20/17m (which I realize is
> suboptimal). For a long time, 80m has been atrociously noisy and the
> upper bands pretty reasonable. Last week, I noticed S9 noise on all of
> 20m, constantly, but 40m didn't seem any worse. I didn't think I had
> any new devices that would cause trouble, and the nearest neighbor is
> 200m away.
>
> Sniffing around with a portable HF receiver (powered by AA cells) and a
> 2m quarterwave whip, I found some noise near AC power outlets and
> anything connected to them. Interestingly, signals also seemed to come
> up near outlets, apparently from coupling from power lines to the whip.
>
> After not too long, I found the source: I have about 6 batteries on
> float 4, 7 and 12 Ah, connected to rigrunner. The only load is a small
> computer (Soekris net5501) that pulls 0.5A at 12V, and I have a DelTran
> Battery Tender connected to float charge the batteries, which normally
> sit at about 13.3V. The batteries and charger have been there for at
> least 5 years, and the computer for just about 2. Putting the whip in
> the middle of the battery cables over the rigrunner produced the highest
> noise reading I ever saw.
>
> Unplugging the charger silenced the noise. Given that it seems coupled
> to AC wiring elsewhere, it seems pretty clear that this was conducted
> emissions. What isn't clear yet is if it started on the DC side and was
> conducted to AC, or if it was generated in the charger.
>
> I will try out the charger without the computer load. I wonder if this
> is a sign of incipient failure. I saw another instance of this model
> fail and overcharge batteries to 16V, but this one was regulating
> properly.
>
> Has anyone seen similar behavior?
>
> 73 de n1dam
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