49X Series Comparison
This page is an attempt to compare the 49X, 275X, and 279X series spectrum analyzers that share many common hardware features. All data is for the base model without options at the time of introduction. The 491 that number wise fits the 49X-series is an entirely different instrument and consequently not covered here.
The 275X-Series evolved from the original 49X-series by increasing the front panel size to full 19" rack width to allow for more buttons and a more convenient access to features like markers. An inside view still reveals that the extra space inside the 275X-Series cabinets is mostly empty, and the same CRT as for the 49X-series is used.
The 279X-Series is the pinnacle of the 49X-Series development, remaining in the classic smaller form factor but utilizing smaller buttons and rotary encoders, borrowing from the newly developed 278X-Series that was introduced at the same time.
Comparison Table
| Model | 492 | 492A | 492BP | 492PGM | 494 | 494A | 495 | 496 | 497P | 2753P | 2754 | 2755 | 2755AP | 2756P | 2792 | 2794 | 2795 | 2797 | Notes |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Frequency Range | 50 kHz – 21 GHz | 50 kHz – 21 GHz | 10 kHz – 21 GHz | 10 kHz – 21 GHz | 10 kHz – 21 GHz | 10 kHz – 21 GHz | 100 Hz – 1.8 GHz | 1 kHz – 1.8 GHz | 100 Hz – 7.1 GHz | 100 Hz – 1.8 GHz | 50 kHz – 21 GHz | 10 kHz – 21 GHz | 10 kHz – 21 GHz | 10 kHz – 21 GHz | 10 kHz – 21 GHz | 10 kHz – 21 GHz | 100 Hz – 1.8 GHz | 100 Hz – 7.1 GHz | |
| Min. Span | 100 kHz | 200 Hz | 1 kHz | 2 kHz | 500 Hz | 100 Hz | 100 Hz | 500 Hz | 1 kHz | 10 Hz | 200 Hz | 200 Hz | 100 Hz | 10 Hz | 2 kHz | 100 Hz | 100 Hz | 100 Hz | |
| Max. Span | 5 GHz | 10 GHz | 100 GHz | 10 GHz | 5 GHz | 100 GHz | 1 GHz | 1 GHz | 5 GHz | 100 MHz | 1 GHz | 10 GHz | 10 GHz | 10 GHz | 12 GHz | 150 GHz | 1.7 GHz | 4 GHz | |
| Ext. Mix | Yes | Yes | Yes | No | Yes | Yes | No | No | No | No | No | Yes | Yes | Yes | Yes | Yes | No | No | |
| Center Frequency Accuracy | ±5 MHz | ±30 kHz | ±21 kHz | ±30 kHz | Freq.Ref. | ±20 kHz | ±20 kHz | ±5 MHz | ±21 kHz | ±20 kHz | ±30kHz | ±30kHz | ±20 kHz | ±20 kHz | ±30kHz | ±20 kHz | ±20 kHz | ±21 kHz | at 1 GHz, 100 kHz/div span |
| Frequency Reference Accuracy | 1×10-6/year | 1×10-5/year | 1×10-7/year | 1×10-7/year | 1×10-7/year | 1×10-6/year | 1×10-7 /year | ? | ? | 5×10-7 /year | 1×10-7 /year | ? | 1×10-7/year | 1×10-7/year | ? | ||||
| SSB Phase Noise | −105 dBc/Hz | −105 dBc/Hz | −103 dBc/Hz | −90 dBc/Hz | −105 dBc/Hz | −105 dBc/Hz | −105 dBc/Hz | -105 dBc/Hz | -103 dBc/Hz | -105 dBc/Hz | -105 dBc/Hz | -105 dBc/Hz | −103 dBc/Hz | −105 dBc/Hz | −105 dBc/Hz | −105 dBc/Hz | 30kHz offset, N=1 | ||
| Min. Resolution Bandwidth | 1 kHz | 100 Hz | 100 Hz | 1 kHz | 30 Hz | 10 Hz | 10 Hz | 30 Hz | 10 Hz | 10 Hz | 1 kHz | 100 Hz | 100 Hz | 10 Hz | 1 kHz | 10 Hz | 10 Hz | 10 Hz | |
| Max. Resolution Bandwidth | 1 MHz | 1 MHz | 3 MHz | 3 MHz | 1 MHz | 3 MHz | 3 MHz | 1 MHz | 3 MHz | 3 MHz | 1 MHz | 1 MHz | 3 MHz | 3 MHz | 3 MHz | 3 MHz | 3 MHz | 3 MHz | |
| Dynamic Range | 80 dB | 80 dB | 90 dB | 80 dB | 80 dB | 90 dB | 80 dB | 80 dB | 90 dB | 90 dB | 80 dB | 80 dB | 90 dB | 90 dB | 90 dB | 90 dB | 90 dB | 90 dB | |
| GPIB | P model | P model | yes | yes | P model | P model | P model | P model | Yes | Yes | P model | P model | Yes | Yes | Yes | Yes | Yes | Yes | |
| Marker | No | Yes | Yes | Yes | No | Yes | Yes | No | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | |
| Counter | No | No | Yes | No | Yes | Yes | Yes | No | Yes | Yes | No | No | Yes | Yes | Yes | Yes | Yes | Yes | |
| Introduced | 1980 | 1987 | 1989 | 1990 | 1985 | 1988 | 1987 | 1982 | 1990 | 1988 | 1987 | 1987 | 1989 | 1988 | 1993 | 1993 | 1993 | 1993 |
Common Features
The frequency conversion is identical for all models and based on two tunable local oscillators. The frequency coverage is split in several bands, where band 1 is selected with electromechanical switches. Therefore none of the members of the 49X, 275X, and 279X families allow for a span exceeding the band 1 limits, as this would require continuous electromechanical band-switching. As a new feature the 279X-family allows for a multiband sweep mode displaying a sweep over bands 2-5. For bands 4 and higher the mixer is operated as a harmonic mixer, which results in a degradation of the analyzers phase noise performance for frequencies exceeding 7.1 GHz. Bands 6-12 require external mixers of the WM490 family or WM780 family.
| Band | Frequency Range (GHz) | 1st IF | LO Range (MHz) | LO Multiplier |
|---|---|---|---|---|
| 1 | 0 − 1.8 | 2072 | 2072 − 3872 | 1- |
| 2 | 1.7 − 5.5 | 829 | 2529 − 6329 | 1- |
| 3 | 3 − 7.1 | 829 | 2171 − 6276 | 1+ |
| 4 | 5.4 − 18 | 829 | 2076 − 6276 | 3- |
| 5 | 15 - 21 | 2072 | 4309 − 6309 | 3+ |
| 6 | 18 - 27 | 2072 | 2655 − 4155 | 6+ |
| 7 | 26 - 40 | 2072 | 2393 − 3793 | 10+ |
| 8 | 33 - 60 | 2072 | 3093 − 5793 | 10+ |
| 9 | 50 - 90 | 2072 | 3195 − 5862 | 15+ |
| 10 | 75 - 140 | 2072 | 3171 − 5997 | 23+ |
| 11 | 110 - 220 | 2072 | 2917 − 5890 | 37+ |
| 12 | 170 - 325 | 2072 | 2999 − 5767 | 56+ |
Note:
A "−" sign after the LO multiplier indicates that the (multiplied) LO is above the received signal. fif = N×fLO − fRF and fRF = N×fLO − fif
A "+" sign after the LO multiplier indicates that the (multiplied) LO is below the received signal. fif = fRF − N×fLO and fRF = N×fLO + fif
Accessories
- TR503 dc − 1.8 GHz tracking generator
- 1405 sideband adapter
- WM490 external mixer
- WM780 external mixer (individually calibrated)
- 067-1137-99 GPIB to accessory controller (for non-P instruments)