Thursday, August 27, 2009

Split Transmit

Trying to design a usable UI as the capabilities get more complex is not easy!

I have added the split rx/tx full/half duplex capability. This is using VFO-A for receive and VFO-B for transmit. Now that VFO-B is used for this I have changed the sub receiver to maintain it's own receive frequency.

In the image above the main receiver is receiving on 14.195200 MHz, the sub receiver is receiving on 14.219700 MHz and the transmitter is transmitting on 14.241900 MHz. All running full duplex! Of course, the transmit frequency does not have to be in the displayed passband, but then it would not be visible!

I am also adding transverter support for the split frequency mode mainly to support working cross band on the satellites.

Note that this is currently working with a version of the firmware that is not yet generally released.

Next major UI design issue will be how to support multiple receivers both within one Mercury card and with multiple mercury cards.

Thursday, August 20, 2009

AO-51 Mode-S

Click for full size image

I hooked up my Mode-S down converter and quad patch antenna as I saw that AO-51 was running in Mode-S for the next few days.

Here you can see the Doppler shift as AO-51 approaches my QTH. Running at 4 frames per second for the display update so the waterfall represents 50 seconds. I need to add an interface (CAT?) to allow another program to control the frequency. On a subsequent pass I used the sub-rx to track the doppler manually, leaving the main rx on centre frequency of 2401.200.

The antenna was simply sitting on the window ledge of the shack close to a wireless router, hence the strong qrm.

Wednesday, August 19, 2009


Click for full size image

Here is a screen dump of part of an ISS pass (using a Microwave Modules 2Mtr Transverter) showing the bursts of AX.25 packets.

You can see the doppler shift from high to low frequency as it passes over. I slowed the display update rate to 5 samples per second, so the Waterfall represents about 40 seconds.

The 3 strong signals showing up on the Bandscope at around 20MHz (136MHz) are from Gatwick Airport which is close to my location.

Sunday, August 2, 2009

Video of sub rx

The main rx audio is panned to the left and the sub rx audio is panned to the right.


The video was created using recordmydesktop running on Ubuntu 9.04.