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The HP 8657D Signal Generator was bought as part of a job lot of equipment. This unit has Option 003 Pulse Modulation as standard, Option H12, H35 and includes the π/4 DQPSK I/Q Modulator. It also has the original HP Operation and Calibration Manual for 8657D. The original cost in 1993 was $23,625.

Front view of both units
Rear view of both units
The HP 8657D adds π/4 DQPSK digital modulation capability to conventional AM, FM and pulse modulation. It has the capability to test mobiles for the North American Digital Cellular (NADC) and Japanese Digital Cellular (JDC) radio systems. In the analogue modulation mode, specifications are the same as the HP 8657B Signal Generator up to 1030MHz.

Special bracket and rear inter-connections
The 8657D provides a 800MHz input and output to the separate π/4 DQPSK I/Q Modulator which is housed in a 2U high case underneath. Inter-connections are provided by a rigid N-type to N-type cable at the front and 2 SMA to 3.5mm cables at the rear. The 3U high 8657D is fixed to the Modulator with 5U high front panel handles and rack ears, plus special brackets at the rear.

January 2016

The Signal Generator and DQPSK Modulator were separated and cleaned up.

Signal Generator front view
Signal Generator rear view
The Signal Generator will operate as a 8657B but only up to 1030MHz. It needs a short SMA to SMA cable to loop the 800MHz input and output on the rear panel, otherwise there is no RF output!

Signal Generator top view with cover removed
Signal Generator bottom view with cover removed
The 8657D Signal Generator completed its User Confidence and Adjustment Tests ok. As I already have a working 8657B Signal Generator, the 8657D is for sale.

For details of the Modulator Unit see HP 8657D DQPSK I/Q Modulator Unit.

March 2016 

The 8657D Signal Generator is SOLD.