QtRadio - Operation

Tuning the radio

Fixed frequency radio

For crystal locked radios such as the softrock lite II or YU1LM sdr's It is necessary to use subRx. The procedure is to set vfoA to your centre frequency, usually the crystal frequency / 4 and leave it alone as changing it will affect your centre frequency. Using the button on the vfo panel or the 'Receiver' Menu / subRx choice switch on the subRx. You can now tune within the limits of the sample rate of your sound card (48, 96 or 192 KHz) with your centre frequency offset from centre by 9 KHz.

Note there is still a bug in the display where the lower 9 KHz wraps to the upper 9 KHz but the audio doesn't track the spectrum so you lose 9 KHz of possible bandwidth.

Setting the noise floor

The height of the spectrum from the baseline is adjusted by rolling the mouse wheel with the pointer over the level calibration markings on the extreme left hand side of the spectrum window. This will at the same time change the base colour of the waterfall.

The procedure is: After setting the sound-card gain you should remove the antenna and roll the mouse-wheel to give a spectrum display line just above the bottom of the window. When you apply the antenna the spectrum will rise in the window and the waterfall base colour should be dark blue unless the band is particularly noisy.

Calibrating the S meter

To calibrate the S Meter, a signal equal to S9 (-73 dBm) is injected into the sdr and the soundcard gain is adjusted until the S meter reads S9. It will then probably be necessary to adjust the spectrum noise floor level.

A subjective calibration may be performed by tuning into a signal considered S9 and performing the above procedure.

Using subRx

To be constructed

The Menu choices

Receiver

Config > Audio If you are connecting to a public server on the Internet (ie not your own server on your LAN), please set Audio to 8000, aLaw, and 1 channel. If you use other settings, your QtRadio and/or the dspserver/server will hang.