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HP 8657B SIGNAL GENERATOR
The HP 8657B Signal Generator was bought on eBay USA as untested so was taking a risk, but even with shipping and import VAT it was still significantly less expensive than buying in the UK.  It arrived very well packed and undamaged. This 8657B was made in the UK so it has been across the 'Pond' twice. 

The original cost was $13,660 in 1993, plus $1,040 for the Option 001 High Stability Timebase (not fitted), $270 Option 002 Rear Panel Connectors (not fitted) and $890 Option 003 Pulse Modulation (fitted).

The 8657B has a frequency range from 100kHz to 2060MHz with 1Hz resolution.  Output level is +13dBm to -143.5dBm with 0.1dB resolution.  Amplitude, Frequency and Phase Modulation available. HP-IB programmable.

The Operation & Calibration Manual and the Service Manual (2 volumes) were all available for download.

Front Panel
Conventional front panel with connectors for AM/FM Modulation In/Out, Pulse Input, RF Output.

Rear Panel
Conventional rear panel with connectors for HP-IB, Timebase Input and Output, Sequential Trigger and Power.  The power supply is built in the rear section.

Top view with cover removed
Bottom view with cover removed
June 2015

The 8657B is a heavy unit at 18.5kg and also big at 425mm wide x 135mm high x 600mm deep including N-type connector.  Cleaned up the panels and case.  The covers are unusual in that they are only secured by 4 screws holding the handle straps on each side.  The 8657B did not have any feet fitted, so I fitted some spare feet.  The rear feet have 3 fixing holes but the front feet only have 2 fixing holes, so I sawed off a fixing lug on each front foot. 

Changed the line voltage selector to 240V and checked the fuse, these are a bit tricky to get to.  Powered-up on a Variac and all ok, fan running and all the LEDs are on for 5 seconds, then reverts to last known state.

Front Panel at power-up
A quick check shows all functions working normally, able to set frequency, amplitude, modulation ok.  Pressing SHIFT and PRESET sets the 8657B to its default conditions.  Fortunate that this unit is working ok after all its travels.

Front Panel showing typical display
Now need to work through the Operating and Calibrating Manual.


July 2015 

The User Confidence Tests show a low output at frequencies around 1030MHz so some repair work is required.  For details see Repair HP 8657B Signal Generator.


November 2015 

Bought another HP 8657B Signal Generator as part of a job lot of equipment. This unit has Option 003 Pulse Modulation and Option 022 GMSK Modulation.  It also has the original HP Operation and Calibration Manual for 8656B, 8657A & 8657B.  The original cost in 1993 of Option 022 was $7,345 making $21,895 in total.

Front view with Modulator underneath
Rear view with Modulator underneath
December 2015 

HP Technical Data describes Option 022 "For European digital communications systems, generates 0.3 Gaussian Minimum Shift Keying (0.3 GMSK).  100kHz to 2060MHz AM & FM.  0.3 GMSK 520 to 2060MHz, 10 to 130MHz data inverted. Baseband I/Q outputs.  With 0.3 GMSK modulation turned off, performs as standard 8657B". 

The 8657B is modified to provide a 800MHz input and output to the separate 0.3 GMSK Modulator which is housed in a 1U high case underneath.   Interconnections are provided by 2 SMA to 3.5mm cables.  The 3U high 8657B is fixed to the Modulator with 4U high front panel handles and rack ears, plus special brackets at the rear. 

Special fixings at rear
As the reported fault was "smoking!", separated the 2 units and cleaned them up.  For repair details, see Repair HP 8657B Signal Generator.


January 2016

Rear Panel 800MHz SMA Connectors
As the second 8657B with Option 003 & Option 022 tested ok, it will be kept as my Bench Unit.  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!

As I have no need for the 0.3 GMSK Modulator unit, this is FOR SALE, see HP 8657B Option 022 0.3 GMSK Modulator Unit for details.


February 2016

Completed some further repair work on the first 8657B, see Repair HP 8657B Signal Generator.  All the User Confidence Tests (except HP-IB) completed ok.

My first 8657B with Option 003 is now for sale. SOLD
 

 HP 8656/7 Comparison  
Model 8656A
8656B 8657A 8657B
Frequency
Range
100kHz to
990MHz
100kHz to
990MHz
100kHz to
1040MHz
100kHz to
2060MHz
Resolution 100Hz 10Hz 10Hz 1Hz
LED Display

7 Digit
Red
8 Digit
Red
8 Digit
Green
10 Digit
Green 
Attenuator

+10dBm
to
-127dBm
+13dBm
to
-127dBm
+13dBm
to
-127dBm
+13dBm
to
-143.5dBm
Resolution 0.1dB 0.1dB 0.1dB 0.1dB
LED Display

3½ Digit
Red
3½ Digit
Red
3½ Digit
Green
3½ Digit
Green
Modulation

Int/Ext
AM/FM
Int/Ext
AM/FM
Int/Ext
AM/FM
Int/Ext
AM/FM
Ext Pulse
Misc     RF Off/On RF Off/On
See also HP 8657D Signal Generator which is a similar unit to the 8657B.

Battery B1
November 2016

Checking all the specialist batteries in my test equipment, see Batteries In Test Equipment. The 8657B has a 2.8V 0.35AHr Lithium Battery on A13 Assembly, Reference B1, Part No 1420-0281. Made by GE Co Insulating Materials Products Part No 2763WT. An alternative is Catalyst Research Corp Part No 2736 3 Pin. 
 
The 8657B settings and storage register contents are saved in RAM. When the 8657B is switched on, it displays the last settings. If power up displays "Clearing" the battery needs recharging or changing. The 8657B needs powering up occasionally to charge the battery.