AO-40 Frequency Calculator

By Mirek Kasal, OK2AQK and Pavel Kasal, OK2XGG

E-mail:ok2aqk@amsat.org

The Compact Version

Download: FqCalc.exe

The Excel Version

The calculator has been developed as an aid for AO-40 users. It was done in Microsoft Excel which must be installed in your PC. In tools and options window of Excel you can set a form which looks like in the following figures. All the frequencies are in MHz but the BRX display and RX display are put separately in MHz and kHz (4 digits without decimal point) for practical reason. You can change the values in framed cells. I suggest all the other cells to be locked.


Fig.1. S-band is converted to 2m band and U-band is displayed directly.	Fig.2. S-band is converted to 10m band and for the U-band is used a transverter from 2m.
Beacon > is the beacon frequency (NBF) corrected by Doppler shift in your location. This value should agree with the same one precisely calculated by your tracking program (see RX offset). BRX display is your radio's frequency on which you just listen to the beacon. It should be set first. RX offset is a parameter of your receiving system. It is a difference between nominal and real receiving frequency. If you have not a good calibrator you can use a tracking program which calculates Doppler shift accurately. Then you set RX offset according to right value of the Beacon >. Be careful, usually this value varies a bit, especially if you have not TCXO in your mast mounted down converter.
	Fig.3 S-band is converted to 2m band and L-band is displayed directly.

NBF is the nominal (real) frequency of the beacon.
NRXLO is the nominal frequency of the local oscillator in your down-converter.
Doppler is the actual Doppler shift on the beacon frequency (NBF).
LO is the frequency transposition made by transponder. In principle, it is obtained as a sum of corresponding frequencies for uplink and downlink (5th row). By this way you can correct this value by yourself.
Downlink and Uplink frequencies are the values which are in the satellite transponder passband. These are shown in the graphic window: violet symbol is your uplink frequency, red is the beacon and blue your downlink frequency. Please, do not transmit on the TX freq if the two last symbols are in touch.
Downlink range is shifted like the beacon to the original nominal frequencies. Both values are set manually. Uplink range is calculated by means of the LO.
RX display is the actual frequency you can see on your receiver display.
RX freq is the frequency on which a ground station would like to hear its signal.
TX freq is the frequency of the ground station transmitter which you want to hear.
TXLO is the frequency of the TX transverter local oscillator if a transverter is applied, fig. 2.
TX display is the corresponding frequency of your transmitter as a result of calculation. If TX transverter is not used set TXLO = 0 and TX display will be the same as TX freq, fig. 1 and 3.

Please, do not expect a longer term accuracy better than one kHz. A number of microwave oscillators are in the play. Usually the ground station down converter (RX offset) is a big source of inaccuracy. Any comments would be appreciated.

Download: AO-40Fqcalc.xls
AO-40Fqc95.xls (for Excel 5)

Since 1.9.2003