This is very interesting to me as I've posed an earlier, as yet unanswered,
question about potential RFI in a Bosch inverter-driven compressor heat pump,.
I am considering this as an alternative to a two-speed conventional compressor
unit. The Bosch is addition to the government mandated ECM blower also uses
variable speed condenser fan. The schematic shows a couple of toroid chokes on
the line input, so they've made some attempt at suppression but how effective,
who knows.
Bosch has given me the equivalent of the mechanic's shrug when I asked
questions. Steve, W1EMI, at ARRL has no direct experience, but passed along a
couple of links.
https://www.youtube.com/watch?v=vj-14H-HpFU ; and
https://viennawireless.net/wp/wp-content/uploads/2021/09/HILLSON_RFI_PDF_3SEP2021.pdf
My contractor, although sympathetic, has no input other than to send me one of
the links above.
As much as I would like to embrace the new technology, I think I'm going to
have to opt for the old (Trane), even though it too uses an ECM blower.
Wes N7WS
On Tuesday, November 15, 2022 at 06:57:51 PM MST, Don Kirk
<wd8dsb@gmail.com> wrote:
Today I tracked down new RFI at my QTH on 160 meters. I was able to hear
the RFI from my driveway using my portable flag with the DX Engineering
preamp and it indicated the RFI was arriving from the SW (similar to what
my stationary pennants indicated). Using the portable flag I was able to
quickly track the RFI down to a variable speed drive located at a Living
Historical Museum located 1.1 miles from my house and it was pretty amazing
how strong the signal was at my QTH considering the distance.
This case was very interesting because the variable speed drive is for a
fan that blows air into the bottom chamber of a 105 foot tall tethered
Helium balloon that takes passengers to a height of 377 feet. The air is
blown into the bottom chamber of the Helium balloon to maintain a constant
pressure in the balloon regardless of the outside temperature.
I had never encountered this RFI before and it turns out their old variable
speed drive system was recently replaced with a new variable speed drive
system. We replaced the new system with their old one and this stopped the
RFI. They will now follow up with the manufacturer of their system to
investigate a solution, and I will help support their troubleshooting as
needed and until then they will use their old system. It does appear a 3
phase powerline filter has been installed on the input of the variable
speed drive on both their old and new systems.
For those interested here is a link to a youtube video I just uploaded that
documents this case. https://youtu.be/Qnz4E9r5vj0
Note: the more I use my portable flag which is unidirectional the more I
appreciate how much time it saves me compared with my bidirectional tuned
loops as I instantly know the direction the RFI is arriving. It often
saves me hours if not days locating the source of RFI.
Just FYI and 73,
Don (wd8dsb)
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