 |
 |
|
|
|
|
|
|
||||||||||||||||||
|
|
|||||||||||||||||||
|
|
|||||||||||||||||||
|
|||||
|
|
 Previous: Inspection and Test of Donated Used Batteries for ARES |  Next: H&K LiteHelpful hints from other amateurs |
By Rick Lindquist, N1RL, Senior News Editor
December 1, 1998
SWLs and BCLs take note! Japan Radio Company has introduced a new receiver that does all of its filtering in its DSP IF. Here's a snapshot look at the new NRD-545 DSP Receiver from JRC.
Rick Lindquist, N1RL, checks out the Japan Radio Company's NRD-545 DSP receiver. [Photo by Joe Bottiglieri, AA1GW] |
The NRD-545 comes from a long heritage of fine JRC SWL/BCL receivers. We reviewed the most immediate predecessor, the NRD-535 HF receiver, in May 1997 (see "Product Review," QST, May 1997, page 68). The NRD-545 is the fifth generation in the JRC general-coverage line. It's the first to offer DSP, and it takes the DSP concept through to full execution in this unit: There are no optional crystal filters available for the NRD-545. All filtering is done in the DSP IF (20.2 kHz).
The first thing that struck me about the NRD-545 was its physical resemblance to the '535. While the design might have been updated, the styling definitely has not been, but that was fine with me. I found the sizeable knobs and display comfortable and easy to manage. (Besides, it reminded me of my Kenwood TS-850S, and it's approximately the same size, too.)
In addition to the flexibility afforded by DSP, the basic receiver covers from LF (100 kHz) through HF (30 MHz). You can get an optional CHE-199 wideband converter unit to expand the tuning range up through UHF (2 GHz). This board did not become available until after we'd ordered our unit, so we haven't looked at it yet. Curiously, the CHE-199 converter limits reception to AM, FM, and wideband FM.
The '545 uses one-chip DDS to yield 1-Hz step frequency selection. Tuning is done by a varactor diode-based electronic tuning system. This is a triple-conversion receiver, with IFs at 70.455 MHz and 455 kHz plus the DSP IF at 20.2 kHz. AGC is looped back to the first IF amp from a digital/analog converter that follows the DSP IF. There's an RTTY demodulator built in for several standard shift rates. You can display demodulated output on a PC using the built-in serial (RS-232) interface. You also can control the radio with a PC using optional, Windows 95-based software. This receiver has a built-in 120 V ac power supply.
The '545 has 1000 channels of memory--up from 200 in the '535. One note here is in order, however. We were not able to figure out how to enter a frequency into memory without referring to the Instruction Manual. Even then it was confusing because the instructions in the book did not match the controls on the radio's front panel (for example, the manual persists in calling the control labeled AGC T/BWC the "FINE" control, although this legend does not appear anywhere on the front panel.)
A lot of AM BC and SW listeners prefer to have synchronous detection. As in the '535, the NRD-545 offers its "exalted carrier, selectable sideband" (ECSS) feature. This reduces the distortion caused by selective fading in AM signals (where the carrrier fades and leaves only the sidebands) by providing a local, synchronously locked "carrier" signal. You then are free to pick upper or lower sideband, if you desire. This works quite nicely and makes AM BC reception a real pleasure, especially for distant, nighttime signals. The built-in speaker and front-panel tone control also help. There's also an AMS mode for enhanced AM listening. We thought this might be AM stereo, but it's not. The manual says it permits you to "listen to AM broadcasts in hi-fi," and it does sound better.
Speaking of AM, via the "user setup" (menu), you can select 10-kHz or 9-kHz tuning steps to accommodate Standard Broadcast band tuning, as well as a variety of other possible settings, timer relay operation, BFO offset, RTTY parameters, and noise reduction.
In addition to large fluorescent numerals on the display, there's an analog-style S meter that's really comprised of fluorescent segments. The S meter is not tied to the AGC.
The pass band shift (PBS) control operates at IF to shift the DSP filter ± 2.3 kHz. It worked very well, and it would have been hard to detect that it was operating in the DSP IF as opposed to a conventional IF strip.
Adjusting bandwidth is simple but a bit perplexing too. There are three overall FILTER settings, WIDE, INTER, and NARROW. Big buttons adjacent to the large, conventional-style tuning knob (it reminded me a bit of the one on the old TS-520 with its analog apron). But then you have a bandwidth control (it's a function of the multifunction AGC T/BWC knob). This overrides the "primary" filter setting, but if you change the "primary" filter (say, from WIDE to INTER), it goes back to a default bandwidth for the mode you're in. Bandwidth is displayed on the front panel. In addition, you can adjust the time constant of the AGC from a very rapid 0.04 to a torpid 5.1. You also can turn the AGC off altogether, but that's another button and it's not anywhere near the knob you use to adjust the AGC time constant.
The DSP noise reduction is great. The only complaint is that JRC makes you go into the menu to adjust the effect beyond the default setting. Most modern receivers let you do this with a front-panel control.
There's a front-panel mini-phone jack for hooking up a recorder or feeding your PC sound card. The NRD-545 also has DSP autonotch and variable notching.
This is, overall, a sensitive receiver. It also does not apply huge amounts of attenuation in the Standard Broadcast band or LF segments. Sensitivity numbers we measured were less than 1 m V in any given filter setting at 1 MHz in the AM mode. It also had good sensitivity down in the nether regions (we measured -127 dBm at 100 kHz). By the way, this receiver has an attenuator but not a specific preamp.
Blocking dynamic range at 3.5 MHz came in at 128 dB (noise-limited), which is excellent performance. Two-tone, third-order IMD dynamic range topped 90 dB in the HF spectrum. Also terrific!
The NRD-545 appears to be a worthy successor to the popular and enduring NRD-535 and offers improved performance with the flexibility of DSP. Look for a more in-depth review of this receiver in a future issue of QST.
| Previous: Inspection and Test of Donated Used Batteries for ARES | Next: H&K Lite Helpful hints from other amateurs |
