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Rack mounting and RFI

I'm getting ready to pull the trigger on a 6600 and am considering placement. I have a 4-post open rack which holds a Ubiquiti Dream Machine Pro/24-port POE switch, Synology 820+ NAS and APC power backup. It's located near where the coax lines will enter the house, as well as being close to ground at the breaker box. Would I encounter disruptive RFI/EMI to either the LAN or the Flex in such close proximity to each other? For the most part, I have STP CAT 7 on the long runs. Another approach would be to put the Flex and the eventual transverters in a separate enclosed grounded rack and put a fan in it.

I just got my tech ticket (KE8TBO), though I've been around the hobby all 64 years of my life through my Silent Key father, W8FPO. I'm retired and have the time now to devote to it, and decided to not mess around and just get what I've been looking for; a server oriented SDR that can be accessed over LAN/WAN. At my age, I suspect I'll never need another radio.

Any tips on this subject are welcome, as well as thoughts about linear vs. switching station power supplies in this scenario.

TIA
73 DE KE8TBO
Chuck

Best Answers

  • KD0RC
    KD0RC Broomfield, COMember, Super Elmer Moderator
    Answer ✓

    Hi Chuck, I would guess that the open rack would be fine, but you won't really know until you try it.

    If you have a way to to do a comparison of the two locations without a lot of permanent setup, I think you would get a definitive answer.

    Linear supplies are always quieter, but many of the modern switchers are very acceptable. Some even have a switch to change the switching frequency slightly to move any spurs out of the ham bands.

    I have a big 75 amp Astron that I power my whole shack from. It is big and gets warm, but is completely RF-quiet and I don't have to worry about overloading it.

  • John KB4DU
    John KB4DU Member ✭✭✭✭
    Answer ✓

    Chuck, either ps will work fine with the flex, providing adequate capacity, 30 amps or more. I use the mfj 4230 switching supply. There is no measurable difference in noise with it or a battery. It also has variable voltage, so it provides 13.8 volts measured at the flex during full power output.

Answers

  • DoctorQ
    DoctorQ Member ✭✭
    edited October 2021
    Edit: let’s try this again…
  • DoctorQ
    DoctorQ Member ✭✭
    Thanks for the info, guys. Glad to hear I don’t have to worry about switching supplies that much, as they’re considerably cheaper than linear. Unfortunately, the backlog at the ports seems to have hit the supply of supplies, at least as far as HRO’s inventory is concerned. I’ll probably need two if I decide to get a pair of transverters for satellite work. Big plans.

    @KD0RC, I think I knew the answer to my question as I was typing it. If there’s RFI/EMI, sniff it out and eliminate it, it’s hard to predict this stuff ahead of time. I guess I’m paranoid of all the RF around all that digital circuitry, even though processors are clocked in the GHz range.
    Now for the next step, taking a crowbar to my bank account and buying this radio;-)
    Chuck
  • KD0RC
    KD0RC Broomfield, COMember, Super Elmer Moderator

    Hi Chuck, Well, most RFI will come in via the antenna, although some may be conducted in on power cabling and other cabling connected to the radio. To best see this effect, disconnect the antenna (or on the Flex, choose an unused antenna or XVTR port). Any conducted-in noise will show up.

    With my Flex 6400, all the junk that I see in the bands from my house and around the neighborhood completely disappears when I select RX A with nothing attached. This indicates that all the noise-makers in my shack are being picked up by the antenna and not coming in by some means related to the radio's proximity to them (either conducted or radiated).

    If you are running wire antennas in the attic a few feet from your home electronics, you will likely have significantly more noise to deal with than if your antenna is higher and farther away. Double the distance of the antenna from a noise source and you reduce it by a factor of four (square law...).

    If you decide to get a Flex radio, I think you will be pleasantly surprised by how very clean the RX and TX are. Without an antenna attached, I don't see any birdies on any ham band, so I know that anything that I see is coming in via the antenna.

  • Stan VA7NF
    Stan VA7NF President Surrey Amateur Radio Communications Member ✭✭✭
    edited October 2021

    Suggest, adding a backup battery in the power arrangement. LiFePo3 (Lithium Ferrous Oxide) batteries are great for this purpose. All the higher power units include their own BMS (Battery Management System) which means if you wire it in parallel with your PS (set to 14.4-14.6V) it will always charge to 95% and greatly extend its life. No need for any charge controls etc. The low internal resistance battery, plus a RF type(mica) .01-.1uf bypass capacitor across the battery leads will also reduce any birdies on the power leads. Twisting the PS and battery leads also help.

    Added note: You will still see birdies below 160M on most switching supplies but then if it becomes a problem just switch off the PS and the battery will give you hours of very quiet receive. I use a 100Ah in my shack PLUS a 20Ah one inside my grab-and-go 4U gator case and 6700. That G&G has 40A fanless PS, 120VAC and 14VDC EMI filters, network switch, NUC computer, 20Ah battery, broadcast band band reject filter, front-end RF protector, switched battery backed power-poles for Maestro, and of-course the 6700.

    edit: Phosphate not oxide

  • John KB4DU
    John KB4DU Member ✭✭✭✭

    Some have had RFI in the Ethernet cabling that seems to be more common when using an amplifier. Conversion to fiber cabling has fixed it.

  • DoctorQ
    DoctorQ Member ✭✭
    Well, I guess I'll find out the answers to my questions; I saw a refurbished 6600 for sale last night. Mine now. B)
  • KD0RC
    KD0RC Broomfield, COMember, Super Elmer Moderator

    Congratulations! It is always fun to get new gear.

  • John KB4DU
    John KB4DU Member ✭✭✭✭

    A learning curve, but worth it.

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