The concept of software defined radios (SDR’s) is becoming increasing popular in both commercial, military and Amateur Radio circles. In their basic form, the use simple front end filtering followed by a Quadrature Sampling Detector (QSD) with the post detection processing done in software using the sound card found in PC’s. Several popular kits have been developed to introduce Amateurs to the concept.
One such product kit, which we have fun experimenting with, is called the Softrock. Using it, or its many variants, and one of several free software programs, one can build a simple receiver capable of receiving many forms of analog and digital modulation. But being simple, the low cost quadrature sampling detector devices (like the Softrock) typically operate below 30 Mhz.
So now we have this interesting new receiving (and transmitting) technology and we want to use it to receive VHF and higher “stuff”. But most current VHF/UHF converter products have IF’s which are 28 MHz and above.
Well, since the design of our frequency converters is very flexible, it took very little effort to produce VHF/UHF converters with “SDR Friendly” IF’s below 30 Mhz, while still maintaining all the great features of our “standard” VHF/UHF converter line.
So if you want to add the VHF/UHF Amateur Radio spectrum to your experimentation with SDR’s, look over our “SDR Friendly” offerings.
Our “high performance converters” are characterized by their use of an external 10 MHz reference. The local oscillator is phase locked to the external, customer supplied, 10 MHz reference. The use of a highly accurate, frequency stable and low phase noise 10 MHz reference permits the converters use in EME, weak signal WSJT, over the horizon, meteor scatter communications and satellite communication modes.
Borrowing from our commercial PLL signal source capability, the local oscillator also exhibits exceptional phase noise and spurious performance.
Using SAW filters and combline filters, we can achieve excellent image rejection which will provide optimum performance in high out of band signal environments.
The use of pHEMT MMICs offer sub-1dB noise figures. With their superior P1dB performance, in-band intermodulation performance is improved.
The 10 MHz input circuit also includes a sharp 10 MHz crystal filter which acts to clean up spurious signals and improve phase noise of the external reference.