Macintosh Links
Shortwave Radio
Pirate Radio
Spy Numbers Stations
Science and Electronics
Ham Radio Software
Geiger Counters

In a nutshell, the JRC NRD 545 is a triple conversion receiver. The first IF is 70.455 MHz, the second is 455 kHz and the third is 20.22 kHz. The third IF output is fed into an AK5340 18 bit delta-sigma A/D converter, sampled at 78 kHz as near as I can tell. The output of the DSP is fed into an AK4310 stereo 16 bit D/A converter, producing the audio output, with a 39 kHz update rate.

The JRC NRD 545 D/A outputs are routed through a 74HC4052 analog multiplexer, allowing either the D/A outputs to be sent to the final audio output, or the Wideband FM to be used, which recieves no additional filtering after the CHE-199 unit.

One of the first complaints is that the JRC NRD 545 455 kHz filtering is inadequate. The filter used is a CFK455F. The specs I could find for this device (assuming it is made by muRata) are as follows:

3 dB bandwidth: ±4.2 kHz
6 dB bandwidth: ±6 kHz
70 dB bandwidth: ±12 kHz 

The JRC NRD 545 has two options for the DSP filtering: "loose" and "sharp". I take a look at the differences in each set of tests. (Note that there is no apparent difference in AM mode)

I ran a series of experiments on my JRC NRD 545 to measure the actual bandwidth of the 545 in various modes and filter settings. The results are contained on the series of pages below. I disconnected the antenna inputs into the 545, to get just static, with no signals. The JRC NRD 545 audio was fed into Audio Toolbox, a program that I wrote, which can display audio spectrums. While perhaps not the ideal way to perform these measurements, I believe the general technique does work adequately, in the absence of owning professional measurement equipment.

• AM Mode Test Results
• FM Mode Test Results
• SSB Mode Test Results
• CW Mode Test Results
• RTTY Mode Test Results
• Pass Band Shift Test Results
• Notch Filter Test Results
• Beat Cancellation Test Results
• Noise Reduction Test Results
• Tone Control Tests
• Loose vs Sharp Filter Attenuation Tests

For some comparisons, here are some audio spectrum measurements from other radios of mine:

• Icom IC-735
• Icom R-71A
• Icom R-7000