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Wednesday, 1 April 2009

SDR RXTX






After BERU operating with a 80m/40m Softrock RXTX on cw I will build up the SDR kits for the others bands that I have had for a while. The 40m/80m setup is one of the projects I took to HOGCON (http://www.hogcon.com/) show and tell. I have started the next which is a 20m/30m rig. These are discontinued now but I have several of the kits. I will step through them until I have all the HF bands covered.


I have an internal PCI Creative SBLive! 24bit sound card and another external USB card so I intend to make the SDR setup CW/PSK and SSB.


At the same time I will complete the builds of the two kits Jan G0BBL sent me a while back http://m1kta-qrp.blogspot.com/2009/01/usb-controlled-synthesizer-si570.html


As it might be interesting to see a multiband RX setup.




I might also take a stab at adding 5W pa to each. Like here:

http://valdez.bz/wordpress/?p=167








SM0VPO says:






This is a rather unusual QRP Power Amplifier design, with a wide frequency response; within three dB's from 300KHz to 30MHz. Overall gain is in the region of 16dB and the final output power may be well over four watts.
The wide bandwidth is a result of the construction of the RF transformers, T1 and T2. These are wound on 2-hole ferrite balun cores as commonly found in the old fashioned valve TV sets (e.g. Phillips 4322-020-31520). Twist 2 lengths of 22 SWG enamelled wire together and wind as shown. Connect the end of the "A" winding to the start of the "B" winding. Use this junction as the centre-tap of the transformer.
This PA will deliver 4 watts continuously (with a suitable heatsink), and may be loaded into a short-circuit or open circuit without causing damage. This makes it almost the ideal PA for outdoor/field use. Above is the full circuit diagram of the RFPA and the coil winding pattern. This PA may be used for for SSB, as well as CW (and AM?).
Set RV1 to MINIMUM resistance and apply 12volt power with NO DRIVE. Adjust RV1 for about 250mA DC total supply current. This may be be reduced to a much smaller current if lower output powers (reduced drive) is used.



I might just build a single PA and switch it in to line for each.









Funny how the current situation is encouraging me to finish projects off!





I just finshed the daughter card and here I am testing it, two small videos :

First crystal
video

2nd Crystal

video

The rest of the build images:



All the caps and resistors installed.

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