Amateur radio station since 1993
RA3WDK `s Homepage



























































































Now i use Afedri DDC receiver

100 kHz to 35.00MHz continuous frequency range
DDC - Digital Down-Conversion
12- bit 80 MSPS A/D conversion
Up to 1.85MHz recording and processing bandwidth
Sensitivity - MDS -136 dBm at 500Hz bandwidth

More info look for here ...

My SDR old project

I have started to use SDR on VHF in 2009. My the first SDR - project was Soft-66ADH.
In 2010 I have made the SDR the receiver for IF my XVTR 144/28 MHz. Ideas from YU1LM and US5QBR are used :

Its scheme can be seen here:

For the oscillators I use custom-made oscillators by UA3AOH :

I use them in all my XVTR (144,432,1296,10368 MHz). These are excellent generators with good characteristics.
Phase noise it is better -145 db/Nz


Legendary sound card Creative AWE32. I used it 10 years ago together with DSP program K6STI. Excellent result! But now ISA is rare.

For SDR I have started to use sound card Creative SB Labs. I had to modernise it for stabilisation of transfer of a phase and amplitude I&Q signals. Also i mast set + 1 samples delay for the best suppression of the mirror channel.

Now I use Delta44 soundcard .You can take a lot of interesting in modification Delta-44 for better perfomance from SM5BSZ Link.

You can see : AC74AC + diode mixer = not best result for good image rejection almost in 28-29 MHz bandwith. I have got suppression about 50-55 dB! I have increased voltage to 6,5-6,8 V on the phase shifter 74AC74. Probably, in the future, I will choose 74AC74 other manufacturer for the best work of the phase shifter. Also it is necessary to apply switches 74LVC4066 to the mixer - will enable image rejection better than 55 dB.




Now image rejection in constant value (about 50 db) in all bandwith 96 kHz without set in " Channel Skew Calibration ..." in option of WinRad

You can see much on this problem and a lot of useful on SDR on a link by Tasa`s (YU1LM ) .

I am happy with work SDR of a panorama 96 kHz - the review of a range and function WinRad impress ! I find it very useful to VHF !

Excellent results of application SDR in ESporadik open 1 june 2010 !

I modernised mixer on diodes. Has replaced with the mixer on 74HC4066D (YU1LM DR2G)

I made a lot measurements on my SDR. Of course it is possible always to do some new measurements, but i see better IP1 (1 dB compression point was 0 dbm) and IP3 performance. Now image rejection in NOT constant value (about 45-60 db) in all bandwith 96 kHz with set in " Channel Skew Calibration Phase =1,8 degr " in option of WinRad . But better performance will let me excellent results for use SDR in VHF band !