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Author Topic: CW telemetry beacon, 28.570 MHz -- VVV de UTAHSDR  (Read 1310 times)

Offline stendec

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CW telemetry beacon, 28.570 MHz -- VVV de UTAHSDR
« on: February 10, 2022, 0358 UTC »
OK this was a surprise for me...and my apologies if this beacon is already well-known, or if this is not the correct forum. But is is an HF beacon, and is not sending an FCC-licensed callsign -  so it is an 'unlicensed HF beacon'... but one that is not exactly clandestine either.

This CW beacon is on 28.570 MHz and sends telemetry data that includes (as near as I can decipher) local temperature, humidity, AC mains voltages, plus a few other pieces of data/readings that are more obscure. The beacon can *only* be heard on the Utah SDR (by design I'm sure), and probably is very low power - a few milliwatts. Its purpose seems to be to facilitate remote monitoring of the local environmental and electrical conditions at the Utah SDR site by simply tuning into the web-based SDR. Very clever! Here's what was being sent at 0300 UTC:

VVV VVV VVV (x3) DE UTAHSDR
TMP F   47      32       57
HUM     28      25       47
VAC     123.8  121.1  125.9
LCT 0
HCT 0
PF DUR0/0SEC AGO

The TMP and HUM numbers are likely temp and humidity readings. The 3 numbers are for current, low and high readings respectively?

VAC also has 3 numbers and all are in the 120 range. They are probably for the AC mains voltage - again current, low and high readings like the temp & humidity.

Just what the LCT, HCT and PF numbers represent are still a mystery.

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Offline Teotwaki

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Re: CW telemetry beacon, 28.570 MHz -- VVV de UTAHSDR
« Reply #1 on: February 11, 2022, 1555 UTC »
That's quite the discovery! I will agree that the three sets of readings are current/lowest/highest and PF might be measured Power Factor so that they can keep tabs on AC power consumption. Maybe LCT/HCT were to be Low Current and High Current at some time mark?
Jim
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Offline Rob.

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Re: CW telemetry beacon, 28.570 MHz -- VVV de UTAHSDR
« Reply #2 on: February 11, 2022, 1628 UTC »
http://ka7oei.blogspot.com/2020/06/an-esp8266-based-temperature-humidity.html


From https://www.sdrutah.org/info/faq.html

"What's with the 10 meter CW beacon?"

On June 25, 2020, a CW telemetry beacon was added to the site, transmitting on approximately 28.570 MHz, +/- 1 kHz.  This beacon's antenna is (literally) just a few inches of wire - just enough to get from the equipment rack, into the receive antennas - not nearly enough for anyone more than a few hundred feet away from the receive site to hear it.  As such, it falls under FCC part 15 meaning that it does not need a license or "official" callsign of its own which it why it signs "UTAHSDR".

This device also has a web server, not accessible outside the local network, that allows these parameters to be conveyed via a web page.  This information is used to allow logging of the measure conditions and the temperature readings will be used to slightly adjust the local oscillator frequency of some of the receivers to compensate for temperature-induced drift.  For more information about this device, visit the KA7OEI Blogspot entry about it.

This beacon telemeters the following information:

Indoor temperature.  The current temperature - in Fahrenheit - is followed by the recorded minimum and maximum. 
For outside weather conditions please follow the link in the upper-left corner of the WebSDR pages themselves.  The min/max values are reset at local midnight.

Indoor humidity.  The current relative humidity is followed by the recorded minimum and maximum.  The min/max values are reset at local midnight.

Line voltage.  The current mains voltage is followed by the recorded minimum and maximum.  The voltage is across only one phase, so it reads around 120 volts rather than the full 240 volts.  The min/max values are reset at local midnight.

Low voltage count.  The parameter "LCT" is followed by a number indicating the number of times that the mains voltage was recorded as being below 100 volts.  The value is reset at local midnight.

High voltage count.  The parameter "HCT" is followed by a number indicating the number of times that the mains voltage was recorded as being above 135 volts.  The value is reset at local midnight.

Power failure duration and time.  The parameter "PF DUR" is followed by a number indicating the duration of the most recent power failure (mains <100 volts) and another parameter indicating how many seconds ago it occurred.  Only the most recent mains failure is recorded in this manner.  The value is reset at local midnight.

If the WiFi is not connected for some reason there will be an error message that says "WIFI NC" at the end of the telemetry.  This message is omitted entirely if the connection is good.

Hum on CW note:  It is possible that you may hear a bit of AC/mains hum modulated on the CW signal - but this is not really being transmitted.  What is likely happening is a bit of "space modulation" in the local environment causing a slight amount of amplitude modulation at the mains frequency:  Listening on a different receiver/antenna combination may reveal that this hum is absent - or at least different in amplitude.
« Last Edit: February 11, 2022, 1639 UTC by Σ »
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Offline stendec

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Re: CW telemetry beacon, 28.570 MHz -- VVV de UTAHSDR
« Reply #3 on: February 11, 2022, 1932 UTC »
Rob -- Excellent, thanks for the info! Direct from the source.

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