EMI

I often set up an HF receiver to pick up various data transmissions which I decode on a PC. My (CE marked) Epson printer completely trashes all the HF bands while it is printing, and I was certain that I would have no chance whatsoever of receiving anything while the Ormerod was printing, so I didn't even attempt it until today. I was highly surprised to find this morning that the Ormerod caused absolutely no audible or other interference whatsoever to fairly weak weatherfax stations in the 4MHz, 8MHz or 11MHz bands (so far I haven't tried any other frequencies). The receiver is in a different room but not far away from the Ormerod, and the Ormerod is closer to the receiver than the Epson printer.

As an addition, I guess that Kim has shown that it doesn't interfere with the 137MHz marine VHF band either, else his captain would have been up in arms!

Dave
(#106)

Edited 2 time(s). Last edit at 03/02/2014 05:39PM by dmould.

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dmould
I was highly surprised to find this morning that the Ormerod caused absolutely no audible or other interference whatsoever to fairly weak weatherfax stations in the 4MHz, 8MHz or 11MHz bands (so far I haven't tried any other frequencies).

Is that just when the Ormerod is idling, or when it it printing too? Are you deriving the 5V supply from the 12V supply via the on-board switching regulator, or are you supplying 5V from USB or another source?

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

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dc42

Quote
dmould
I was highly surprised to find this morning that the Ormerod caused absolutely no audible or other interference whatsoever to fairly weak weatherfax stations in the 4MHz, 8MHz or 11MHz bands (so far I haven't tried any other frequencies).

Is that just when the Ormerod is idling, or when it it printing too? Are you deriving the 5V supply from the 12V supply via the on-board switching regulator, or are you supplying 5V from USB or another source?

It was while the Ormerod was actively printing. Its 5V is derived from the 12V supply via its on-board regulator, it was connected to a PC via USB as well (not the same PC as used to decode the radio signals). I am not using an ATX power supply, I am using an LED 35 amp 12V PSU (switchmode) - not that that should make a lot of difference. I could not even hear any clicks from the bed or hotend heater switching either - they are frequent enough that it would have been apparent. The radio is however battery powered, so would not pick up mains-borne interference - though a good quality mains HF receiver should be immune to that anyway.

The HF receiver is connected to a simple indoor wire aerial in the same room as the receiver, which is in a room immediately above the room the Ormerod (and Epson printer) are located. I can now also verify that the Ormerod does not interfere with weak satellite signals on 137.1MHz (the marine band I mentioned earlier is on 156Mhz (I got mixed up).

Dave
(#106)