EMETest User Manual

Complete Reference — EMETest

This manual covers every control panel and setting in EMETest. For a guided first-use walkthrough, see the Echo SNR Quick Start or the Noise & Y-Factor Quick Start.

Program Overview

EMETest is organized into a top settings area (tabbed), an information bar, and a main measurement area. Settings are stored automatically in an INI file and restored when the program is next launched. Only one instance of EMETest may run at a time; if a second launch is attempted, a warning dialog appears.

At the first launch, a splash screen presents a brief disclaimer. Check Don’t show again to skip it on future launches.

Settings Tabs

Station Tab

The Station tab is visible at all times across the top of the window. It contains the parameters that define your station.

Frequency (MHz)

Your operating frequency in MHz (e.g., 1296.100). This is the actual RF frequency radiated, not the IF. It is used for all ephemeris calculations: moon distance, propagation delay, Doppler shift, and Doppler spreading.

Grid locator

Your Maidenhead grid square (4 or 6 characters, e.g., FN42ab). When Grid → Lat/Lon is checked, latitude and longitude are computed automatically from the grid. Uncheck the box to enter latitude and longitude directly. More precise coordinates give more accurate moon position and Doppler calculations.

Lat (°N) / Lon (°E)

Decimal degrees. Read-only when Grid → Lat/Lon is active; editable when unchecked. West longitudes are negative.

XV offset (MHz)

Transverter IF offset. If your transverter converts a 144 MHz IF to 1296 MHz, enter 1152. Used so that CAT frequency commands sent to the radio correspond to the correct IF frequency.

Elev (m)

Station elevation above sea level in metres. Affects the parallax correction in moon position calculations.

PTT port

The Windows COM port name connected to your PTT interface. Click the drop-down to refresh the list of available ports. Select the correct port before starting any measurement mode. Not required if using CAT PTT.

PTT line

Choose RTS or DTR to match your interface wiring. RTS is standard for most keyer interfaces.

Audio delay (ms)

The time between the PTT signal going active and the first audio sample being transmitted. 200 ms is a safe default. If your PC has a shorter actual audio pipeline latency, you can reduce this value to shorten each echo cycle slightly, but setting it too low will clip the beginning of the transmitted tone.

Audio Rx/Tx (Hz)

The audio frequency of the transmitted tone and the centre of the echo analysis window. Default 1500 Hz. This field highlights amber when changed from 1500 Hz as a reminder. Must match the frequency visible in the receiver passband.

Allow -El

When checked, allows the echo sequence to run even when the Moon is below the geometric horizon. Useful for stations with clear horizons where the Moon is geometrically below 0° but still visible. Normally leave this unchecked.

Audio Devices…

Opens the audio device selection popup. Choose the Windows sound card input and output devices to use. Both default to System Default (whatever Windows has selected). Device names are taken from the WASAPI layer for accurate identification.

CAT Control Tab

CAT (Computer Aided Transceiver) control allows EMETest to read and set the radio frequency and key the transmitter. It is optional but enables automatic Doppler correction and CAT PTT. The tab is available only when cat_control.py is present in the same directory as EMETest.exe.

Rig

Select your radio model. Kenwood, Icom, Yaesu, and several others are supported.

CAT port / Baud

The COM port and baud rate for the CAT connection. Click the port drop-down to refresh the list. Common baud rates are 4800 or 9600 for older radios; 19200 or higher for modern ones. Check your radio manual.

CI-V addr

Icom radios only. Enter the radio’s CI-V address in hexadecimal (e.g., 70 for an IC-9700). Leave blank for Kenwood and Yaesu.

CAT Connect / Disconnect

Establishes or closes the CAT connection. The status label to the right shows whether the connection was successful and which frequency was read from the radio. Measurement controls are locked until a valid frequency response has been received.

Doppler shift RX

When checked, EMETest commands the radio to shift its receive frequency by the calculated Doppler offset before each echo cycle. The radio transmits at the nominal frequency and receives at the Doppler-corrected frequency, keeping the echo centred on the 1500 Hz audio tone. This is similar to WSJT-X’s “Fake It” mode. Requires CAT to be connected and the radio to support split or frequency stepping in 1 Hz increments.

PTT via CAT

When checked, the transmitter is keyed using a CAT command rather than the RTS/DTR serial line. Take care: CAT PTT does not involve any sequencing; the transmitter keys immediately. A hardware sequencer is still required.

Track interval

How often the CAT Doppler frequency is updated (1 s to 5 s). Faster intervals track more accurately but generate more CAT traffic. A warning appears if the interval is shorter than the radio can handle reliably.

Info Tab

Contains buttons that open informational popup windows:

• About — version information and credits.
• Echo Guide — the built-in quick-start guide for echo measurement (same content as this document).
• Links — a list of useful EME resources and web links.
• Noise Guide — the built-in guide for noise measurements (same content as this document).
• Libration — displays an animated GIF illustrating lunar libration and its effect on echo Doppler spreading.

Timing Tab

Contains low-level timing parameters intended for development use. Do not change these values during normal operation.

• FFT start delay — how many milliseconds into the recording window the FFT analysis begins. Default 200 ms.
• FFT end margin — how many milliseconds before the expected echo arrival time the FFT analysis stops. Default 100 ms.
• Mode (Echo1 / Echo2) — Echo1 is the standard operating mode. Echo2 is an experimental mode under development; leave on Echo1 for normal operation.

Moon Information Bar

The Moon bar is visible at all times below the settings tabs. It updates every few seconds and shows the current ephemeris data.

RIT and Audio Tracking Controls

Transfer RIT button

Copies the recommended RIT value into the RIT entry box. You must also set the same value on the radio manually.

RIT (Hz) entry

Enter the RIT offset you have set on the radio. EMETest uses this to compute the actual audio frequency offset and to enable audio tracking within the remaining range.

Audio tracking checkbox

When enabled, EMETest shifts its echo analysis window to track the actual audio frequency of the echo as Doppler changes, without commanding the radio. This is the recommended Doppler correction method for most stations. The checkbox is greyed out when the Doppler offset would place the echo outside the 500–2500 Hz audio band even with the current RIT applied.

SNR Display Panel

The SNR panel shows four readouts updated after each echo:

Last echo SNR

The SNR of the single most recently measured echo, in dB.

Running average SNR

The power-domain accumulated SNR of all echoes since the last reset. This is the statistically most efficient estimate and improves with each echo. It is the primary result to monitor.

SEM

Standard error of the mean of the individual per-echo SNRs, in dB. Gives an indication of the statistical uncertainty of the average.

Perigee equiv SNR

The running average corrected to the SNR that would be measured if the Moon were at perigee (closest approach, approximately 356,400 km). This normalised figure allows fair comparison across sessions observed at different Moon distances. Requires either a valid Moon Y-factor measurement (from the Noise Test) or assumes a default correction based on the distance degradation value.

Echo Spectrum Plot

The plot shows the averaged FFT power spectrum of all echoes accumulated since the last reset. The signal integration band is shown in green; the noise reference flanks are in red. SNR is computed from the ratio of signal power within the green band to noise power in the red flanks, normalised to the 2500 Hz reference bandwidth.

Display Controls (Settings → Display → Avg Echo Spectrum)

Auto Y

When checked, the Y axis scales automatically to the data. Uncheck to set fixed Min and Max values.

Max / Min

Fixed Y-axis limits when Auto Y is unchecked. Adjust with the spinbox controls.

dB scale

When checked, the Y axis is displayed in dB (10 × log10 of normalised power). When unchecked (default), linear normalised power is shown.

Width (Hz)

Manually override the signal integration bandwidth. Check the box and set the value to override the ephemeris-calculated spreading width. Leave unchecked to use the calculated width.

Plot± (Hz)

Half-width of the frequency range shown on the X axis. Default is automatic (based on spreading width). Check the box to set a fixed value (e.g., 200 Hz for a narrow view, 1000 Hz to see interference).

Smooth

Number of spectral bins over which to apply Gaussian smoothing. 0 = no smoothing. Applied to the display only; does not affect SNR calculation.

SNR History Plot

Shows per-echo SNR (individual dots, colored green for valid or red for below-threshold) and the running average (orange line) as a function of echo number. The Y axis range is controlled by the SNR & Echo Number sub-panel of the Settings display area.

Operational Controls

Save Audio Checkbox

When checked, each echo is saved as a WAV file with embedded metadata. Files are written to a dated subdirectory (e.g., save\2025-06-01_180000\echo_001.wav). A red REC indicator appears next to the checkbox during echo and idle modes to confirm that recording is active. The indicator is hidden during Tune, Noise Mon, and Carrier SNR modes since those modes do not produce echo recordings.

Audio Output Level Slider

Controls the amplitude of the transmitted tone, expressed as a fraction of the full-scale audio output (0.0 to 1.0). Works in conjunction with the Windows volume control. Start with a low value and increase gradually while monitoring RF output power. The slider is drawn custom in the theme colors; drag the thumb or click anywhere on the track.

Audio Input Level Meter

Shows the current audio input RMS level as a colored bar. Green is the target range. Yellow means the level is approaching saturation; reduce the PC microphone gain or radio RF gain. Red indicates clipping and will degrade SNR measurements; reduce the level immediately.

Reference Spectrum (Passband Correction)

EMETest can apply a passband correction to the echo spectrum to compensate for non-flat frequency response in the audio chain. The correction divides each FFT bin by the power measured in that bin during a reference recording made with the antenna pointing at a spectrally flat noise source (e.g., cold sky or a 50-ohm load).

Capture Ref button

Records a reference spectrum from the current audio input. Point the antenna at cold sky or terminate the LNA input, then click this button. The reference is captured over several seconds and stored. A note appears when the reference is ready.

Use passband ref checkbox

When checked, the stored reference is applied to the echo FFT before computing SNR. This can improve the accuracy of SNR measurements on systems with significant passband ripple.

Data Files and Logging

EMETest stores all data and configuration in a subdirectory of the Windows AppData folder. You do not need to locate this directory for normal operation, but the paths for the most important files are:

• echo_log.txt — text log of all echo SNR results with timestamps.
• emetest.ini — all GUI settings, restored at startup.
• save\<date>\echo_NNN.wav — recorded echo WAV files (when Save audio is checked).
• noise\Y-factors_<date>.txt — saved noise measurement results.
• crash_report [<timestamp>].txt — created at startup if the previous session ended abnormally. Send these to the developer if problems are encountered.

Log Window

When the "Show Log" checkbox is checked, a log windows will popup to the left of the main windows. Depending on screen resolution the windows may need to be resized or relocated if it desired to view both at the same time. The log text windows shows real-time status and error messages. If the program does not behave as expected, check the log for error messages relating to PTT, CAT, or audio device initialization. If the program is running normally, the log window does not need to be visible. It can be cleared of saved at any time ny clicking on the control buttons at the top of the windows.

Moon Ephemeris Engine

The user does not need to take any action to enable the most accurate ephemeris engine. The program automatically uses the best one available, and the standard installation includes all there engines. A small amount of disk space (maybe 30-40MB) could be freed up by not including the most accurate option, but on most systems disk space is not a problem.

EMETest can use three different engines for moon position and Doppler calculations, selected automatically in order of accuracy:

1. DE440 full — uses the NAIF SPICE toolkit with the DE440 planetary ephemeris kernels for the highest accuracy moon position and Doppler spreading calculations. Requires spiceypy and the kernel files to be present.
2. DE440 spreading — uses DE440 for Doppler spreading width calculation but falls back to PyEphem for moon azimuth, elevation, and Doppler shift. Requires the smaller de440s.bsp kernel only.
3. PyEphem (DE405) — fully self-contained fallback using the PyEphem library. Slightly less accurate than DE440 but adequate for all normal EME purposes.

A notification dialog at startup reports which engine is active and whether any kernel files are missing. Kernel files should be placed in the same directory as EMETest.exe.

Solar Flux Retrieval

EMETest automatically fetches the current 10.7 cm solar flux (F10.7) from the DRAO Penticton data service when the Noise Test window is opened. This value is used for context when interpreting the Sun Y-factor and is included in the saved Y-factor file. An internet connection is required to retrieve this data, but the program operates normally when off-line but the current 10.7cm solar flux data will not be recorded.

Carrier SNR Monitor

The Carrier SNR monitor (the Carrier SNR button) allows measuring the SNR of a received continuous carrier signal. It analyses the audio input in 3-second segments, computing SNR at the Audio Rx/Tx frequency using the same algorithm as the echo measurement. This is useful for measuring the SNR of a weak DX station which might not be decoded using WSJTX, for monitoring the SNR of a distant terrestrial beacon, or for measuring the strength of a "birdie". The averaged carrier spectrum is shown on the main spectrum plot. Click anywhere in the spectrum to re-center the analysis window on a carrier at a different audio frequency.