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Thursday 11 March 2010

New Softrock TXRX kit from Tony Parks

Tony posted info on the design to softrock yahoo group.

OK first things first... public apology to Tony as I hit post not save as this should have waited a while but Tony has said fine to blog this and my build.

The Ensemble combines the V6.3 RXTX, PA/Filter kit and USB Interface on a single 2.5 by 5.0 inch circuit board. The USB interface and USB powered Si570 are opto and transformer isolated from the rest of the RXTX circuits and results in almost no USB noise on the RX function. He has included board mounted connectors along one edge of the board making it convenient to mount the board within a metal box. The builder would select a band group, (160m, 80m/40m, 30m/20m/17m, or 15m/12m/10m), at the time of building the kit.

I will have completed a build and this will be on air at the SHARE rally 11th April near Inneskillen North Ireland where I will have a homebrew display and will also be running Simon Browns SDR-RADIO software with this and other SDR projects. If you have a homebrew SDR project bring it along and lets try it out on air.

For those that also like to lay hands on kits before deciding to buy or not I will also have a pair of V6.3 TXRX and V9.0 RX kits I will have built up and a pair as basic kits.


qrper said...

Good looking and how can I get it?

M1KTA said... and wait until available

Unknown said...

I have had my RXTX6.3 / Tony Parks I2C V1.4 running for about 1 year now (pix on the yahoo group) and would be interested in knowing how the USB port and the audio I-Q are isolated from the rest of the circuits to control noise. Bill K6ACJ

M1KTA said...


These comment refer to the V6.3 and V9.0 softrocks not this new kit.

Usually the noise you get is because of ground loop pickup between the laptop/PC and the SDR. Break the ground connections and the noise 'dissappears'...

In any implementation I build I learnt never share the same ground between the I/Q audio and the USB. If you isolate the board I/Q audio from the input to the sound card (I use external usb cards as well and you can very quickly see the effect.

How? Simple implementation, use a pair of 600ohm isolation transformers and connect one side of each to the Tip/GND and Ring/GND board connectors, connect the other side to the sound card. Obviously zero point in the isolation transformers if you use phono or 3.5mm stereo sockets sharing the chassis ground.

Likewise for the PTT NEVER connect the pin 5 from the serial cable to the RXTX board ground, leave it floating, cut the ground shield short and keep it away from the Softrock.

Another common place problems occur is shared ground with a mains power supply.

BTW having a good ground plane and attaching items to it sharing the ground only makes ground loops MORE effective not less so. The most quiet I have seen a softrock yet, someone else built it and it was housed in a clear perspex case! That said he had no TX nearby!

Tribologist said...

He has a Trifilar transformer between teh Si570 and the fip-flops. Very simple to do as a retrofit on the 6.3 You need a BN 61-2402 core.