ka7oei

About

Username
ka7oei
Joined
Visits
1,210
Last Active
Roles
Member
Points
1
  • Remote Battery Voltage Monitoring

    Although intended for monitoring mains voltage, I did a somewhat similar thing using the ESP8266, described here:

    The source code is linked, and making it read supply voltage rather than mains voltage would be trivial. The '8266 has only a single A/D input, but the addition of a simple analog MUX chip like the 4051 would easily expand this to 8 inputs - although one would probably want to level-convert the MUX drive to 5 volt logic (e.g. an NPN and two diodes).

    * * *

    If a network connection isn't in the cards (the ESP8266 has 2.4 GHz WiFi only) this also includes a Morse beacon that telemeters the information - in this case, on 10 meters: This was added so that telemetry could be seen by anyone interested, but also so that we could still receive it should the WiFi connection drop for some reason.

    * * *

    Finally, the same, basic low-power TX could be driven by a PIC or Arduino, of course to produce Morse telemetry.

    To get back to an aspect of your question: I suppose that a BBG GPIO pin with an A/D input would be available, but I chose to leave the KiwiSDR unit unmodified - both for practical reasons (a spare could be swapped out) and also to avoid the possibility of conducting undesired signals in/out of the chassis (e.g. static, RFI, lightning, etc.)

    73,

    Clint, KA7OEI

    KU4BY
  • Problem with massive RFI after changing router

    I have seen several situations where the "old" router/switch was replaced with one that happened to support POE (Power Over Ethernet) - and the world of MW/HF/SW reception ended at that point.

    In all cases where I was involved, that new, noisy device had to be (for all practical purposes) scrapped as no amount of CM filtering seemed to be able to return the noise floor to its previous level - although placing a cheap, name-brand, non-POE switch immediately after it and running all cables through it, instead, may be able to break things up sufficiently: This was used as a stop-gap/diagnostic measure rather than a permanent solution. For those instances where a POE device had to be used (a wireless access point, a camera, etc.) a bit of flailing around had to be done to either find a "quieter" POE switch or to simply apply the POE supply at the far end, near as possible to the device being powered to avoid the LAN cable being an antenna.

    It may be that the (rather expensive) DX Engineering Ethernet isolators may do the trick - but they are damn expensive (about $50 each) for a pair of bog-standard Ethernet PHY magnetics simply wired back-to-back: An example of "What the market will bear", I guess...

    * * *

    While standard Ethernet is, by definition, a balanced transmission system with a good CM ratio, in most cases the "P" part of POE is not balanced at all - often connected to the butt-end of a noisy-@$$ switch-mode power supply via filtering that may, if the device is reputable, just barely meet Part 15 conducted noise standards on each individual cable. As we all know, however, Part 15 (even the more strict "Subpart B" for home devices) is nowhere clean enough to preserve the LF/HF or even VHF bands if a fairly low noise floor is to be maintained - and this is even less-so when multiple conductors emerge from the switch, acting as several, independent antennas, running around the house, spreading the joys of QRM far and wide.

    In the cases where the router/switch was involved, I have generally found that the use of a cheap, no-name Chinese device, in terms of HF reception - at least without taking extraordinary measures to quash noise - means that you will be doomed: I have seen "20 over" noise from these devices on multiple bands which, assuming a standard 6 dB/S unit calibration factor, implies that 40-50 dB increase from the original noise floor - and I only wish that this were an exaggeration.

    If you are *really* lucky, it may be the unit's power supply that is the main culprit - but it's often the case that most people aren't able to swap such things out to determine if it's the cause. The good news is that such a power supply will probably fail after 12-24 months, anyway!

    A better-known name (Belkin, SMC, D-Link, etc.) that does *NOT* support POE is more likely not to be a spread-spectrum transmitter in its own right.

    Good luck!
    W9SPY
  • Kiwi BBAI software Alpha test instructions

    I have one of the Newark fan capes and at nominal room temperature (70F) it is barely capable of keeping the CPU at an acceptable temperature when it's running at 1.5 Gig.

    The main problem with it - like many similar fans - is that it just can't push the warm air away from the vicinity of the heat producing devices. Adding some additional headers (Adafruit) to add more spacing between the fan and the Kiwi helped a bit, but more help is needed in the form of even a modest fan pulling in "outside" air and pushing it past, between the boards.

    Clint
    PowernumptyWA2TP
  • first fan died... how long do these things last- what other cooling alternatives ?

    I have four KiwiSDRs that I maintain and I had a 100% failure rate after 9-12 months of the fans supplied with the case: Three of these Kiwis were operating in a harsh environment (below freezing to >130F/54C) and one was not: The one in the temperature-controlled room did not last any longer than the other three - but beware statistics with n=1!

    In a posting about this same issue here a year or so ago I specified a cost-effective, good quality, known-brand ball-bearing alternate from a surplus source that I and others have used - in this case, the forum's search will probably be your friend.

    73,
    Clint
    KA7OEI
    k5mo
  • Kiwi BBAI software Alpha test instructions

    I have one of the Newark fan capes and at nominal room temperature (70F) it is barely capable of keeping the CPU at an acceptable temperature when it's running at 1.5 Gig.

    The main problem with it - like many similar fans - is that it just can't push the warm air away from the vicinity of the heat producing devices. Adding some additional headers (Adafruit) to add more spacing between the fan and the Kiwi helped a bit, but more help is needed in the form of even a modest fan pulling in "outside" air and pushing it past, between the boards.

    Clint
    PowernumptyWA2TP