Using Frequency Translators for Scanners

[turbovectorz]

Hi Folks!

My problem is this: I found a very good digital-controlled preselector (via USB) that works in the lower VHF bands (30MHz) for my homebrew mixed-signal scanner. However, I would like to move a specified band, for example iDEN 851-870, down to the preselector's operating range with the least artifacts, i.e. phase-noise, distortion, etc. Basically, an almost exact replica of the contents of the frequency band translated down to VHF. Theoeretically, this will allow me to dynamically choose the signals of interest with better narrowband selectivity without using too many front-end bandpass filters.

Anyone out there worked with frequency translators in similar matter before?

Thank you all advance for your input!

Sincerely,

TVZ

[FatBoy]

are you using a sdr-14 or similiar? basically you need a high end scanner with an IF out. FatBoy

[turbovectorz]

Fatboy,

Thank you for your response.

Yes, that is correct. I am using SDR front-ends and SCR Preselector to get by for now. Due to it's limited capability, I am designing a new high-performance SDR receiver with a much larger bandwidth of at least 160MHz with an onboard FPGA for DSP with either a Xilinx Virtex 6 or Altera Stratix IV.

Here's my current "bulky" receiver configuration:

Antenna (FWD/REV) --> Bandpass Filters --> (Frequency Translator?) --> SCR Preselector --> LNA --> SDR 14-bit Receiver (limited 7.3MHz Bandwidth, DSP-FPGA) -> USB2.0 to Host Workstation
For now, my target carrier frequencies are 25KHz (iDEN, SMR, LMR), 12.5KHz or 6.25KHz (MotoTRBO), 200KHz (GSM). Eventually, 1.25MHz (CDMA + variants), 3G, 4G, etc.

Here's my "ideal" receiver configuration:

Antenna (FWD/REV) --> LNA (with optional bypass) --> SDR 16-bit 160+ MHz at 1+ Gsps --> 10Gigabit Ethernet to Multiple Hosts for parallel processing (DSP-CUDA with VSIPL++)

All of the onboard preselector processing will be on the SDR receiver with no other external components in the RF analog path.

-- TVZ

[FatBoy]

other than most of that being completely over my head, you may want to sign up for the Hearsat mailing list/IRC channel. I think those guys may be more you speed. Maybe My2cents will be in here shortly to try to sell you something........FatBoy