Northern Utah WebSDR

Salt Lake Metro server


Information page
Northern Utah WebSDR logo

This server is part of the Northern Utah WebSDR system which consists of several Internet-accessible receivers located in rural northern Utah (near the town of Corrinne) that are primarily designed for HF reception and local 2 meter reception.  Because of its location, it does not have good reception of 2 meter and 70 cm activity in the Salt Lake and nearby valleys, so this "metro" system was put online.

This server monitors the two meter band and the top 4 MHz (repeater outputs) of the 70 centimeter amateur radio band from a location in East Mill Creek, Utah along the east benches of the Salt Lake valley at an elevation of 4800 Ft ASL (1460 M), approximately 600 Ft (180 M)) above the valley floor and covers Salt Lake City and surrounding communities in the Salt Lake valley. It has limited visibility into Davis and Weber counties to the north, Tooele county to the west, and only marginal coverage into the western portions of Utah County to the south.

The primary antenna is a discone at about 35 feet (10 meters) above the ground and the receivers are RTL-SDR dongles with their gains set just low enough to avoid overload from local repeaters. This method - even though it results in reduced sensitivity when no other signals are present - is chosen over the use of dongles' AGC to keep the displayed signal levels constant, allowing the S-meter is calibrated (to within a couple dB) to provide readings of absolute signal power levels at the antenna's terminals via the S-meter for purposes of signal comparison.

A receiver with 2 MHz of bandwidth, centered on 122.1 MHz is currently being tested for reception of local air traffic control frequencies. For the time being, this replaces the receive slot that had been under test for "Space-to-Earth" reception.



Configuration of the "Salt Lake Metro" WebSDR server:

This server is configured somewhat differently from those used for HF reception to make its use more appropriate for VHF/UHF reception in the following ways:

Waterfall configuration:

The default is for a large and very slow waterfall, intended to serve as a visual history of activity across the band. Use the "speed" and "size" drop-down tabs in the "Waterfall View" box to adjust it to your liking.

Please note that the waterfall will freeze when your browser's focus is switched away from the WebSDR (minimized, tabs are switched, etc.)

S-Meter squelch:

While the "squelch" button is noise-based and works regardless of the signal level, it can be slow, so there is an S-Meter Squelch that will un-mute audio when the signal exceeds the setting, reacting more quickly than the regular squelch. Because it is signal-level based, it must be adjusted properly for each signal - but setting it 3-6dB above the resting S-meter level (when no signal is pesent) is usually adequate.

Note that it is possible to use BOTH types of squelches at the same time if you have intermittent noise that breaks the squelch.

Deviation meter:

An experimental feature is the deviation indicator, active in FM mode. This indication is updated 10 times/second, showing a running value of the deviation. The "Avg-pk" indicator shows the sliding average of the past 10 deviation readings (over 1 second). The "Min" and "Max" show the detected Min/Max deviation values over the past second and the "Apparent peak SNR" shows the ratio, in dB, of the audio "Min" and "Max" over that same period.

Peak deviation values of 3.5-4.5 kHz are considered normal while values consistently below 3.0 kHz are considered to be "low". Note that any noise or subaudible tones are also measured and this will affect the "Min" and apparent peak values accordingly. These readings will be most accurate if FM-WIDE is selected.


Enhanced URL options:

We've also added a few extra control/configuration options via the URL, allowing users to load the page with specific preset configurations.  These changes include:

Tuning the receiver to agiven frequency using a specified mode:

Invoking this page with a preset frequency and mode, append "/?tune=(freq kHz)(mode)" to the URL and save it as a bookmark,

As in:
http://slc2meters.sdrutah.org:8901/?tune=146620fm
This will load the page and tune to 146.62 MHz, FM.

Loading the page with the noise squelch enabled:

Add "?squelch=1" to load the page with squelch enabled,

As in:
http://slc2meters.sdrutah.org:8901/?tune=146620fm?squelch=1

As in:
http://slc2meters.sdrutah.org:8901/?tune=146620fm?squelch=1

Loading the page with the S-meter squelch enabled:

Add "?smsquelch=N" to enable an S-meter based squelch, where "N" is the signal level in dBm of the threshold. Use the S-meter for determining this setting.

As in:
http://slc2meters.sdrutah.org:8901/?tune=146620fm?smsquelch=-93




For more information about the Northern Utah WebSDR - which has coverage on all amateur bands from 2200 through 2 meters - go to The Northern Utah WebSDR web page.

More information about the WebSDR project, including a list of WebSDRs worldwide, can be found at http://www.websdr.org.


Back to the Northern Utah WebSDR Salt Lake Metro server.