The HP / Agilent 8753A, 8753B, 8753C, 8753D, 8753E, 8753ES and 8753ET vector network analyzers (VNA)

The HP/Agilent 8753 series are a range of vector network analyzers (VNAs) made by HP/Agilent that are very popular. Despite all of the 8753 series are discontinued and most are beyond support by Keysight, the 8753 is still an extremely popular VNA, mainly among commercial companies, but some are owned by radio amateurs or other hobbyists, as 8753 prices have fallen dramatically from their new cost. We don't know how many HP or Agilent 8753s were sold, but we find that around 30% of the customers of Kirkby Microwave SMA and N calibration kits are using 8753 series VNAs. All the HP 8753 series instruments can be used with the Kirkby Microwave coaxial calibration kits.

This page has a number of sections, which will hopefully give you all the information you ever wanted about 8753s.

Hardware and software options.
Add or enable software options 002, 006 and 010 on an HP or Agilent 8753.
Differences between the various 8753 models
Loading VNA calibration kit coefficients into the different 8753 models
- 4.1 Loading the coefficients from a kit in the instruments firmware.
- 4.2 Loading the coefficients using by other methods
Calibrating the 8753

1. Hardware and software options for the HP / Agilent 8753 series VNAs

These instruments have a number of hardware and/or software options. Some options such as rack mount handles, extra manuals etc are not that important when buying a used instrument, as but others are. The main options are:

Option 1D5. This improves the frequency stability by changing the standard 10 MHz frequency reference to an oven controlled crystal oscillator (OCXO). The oscillator boards often come up on eBay, but given that the frequency stability of the ovens is quite poor by the standards of ovens, it is probably worth using an external reference and feeding that into the 8753. This option is applicable to the 8753D and later.
Option 002. Adds harmonic analysis. Applicable to the 8753B and later.
Option 006. This changes the frequency range, and is available on all models except the 8753A. In some instances this just increases the upper frequency limit to 6 GHz, but on some models it always reduces the lower frequency limit from 300 kHz to 30 kHz. On the 8753B and 8753C this is just a software option to enable the receiver to receive to 6 GHz. The required 85047A has the necessary frequency doubler to generate up to 6 GHz from the 3 GHz source. But on 6 GHz versions of the later models, the source goes to 6 GHz, so the frequency doubler in the 85047A is not used.
Option 010. This add time-domain analysis to an 8753. This is just a software option.
Option 011. This option removes the internal test set from the VNA, which means an external test set such as the 85046A, 85047B, 85047A is required, rather than it being built in. This can be an advantage, because with direct access to the receivers it is possible to do some things that are impossible if the test set is built in, and there are no direct access to the receivers. (Kirkby Microwave are in the process of developing a frequency extender for the 8753 series, but this will only be applicable to models with direct receiver access, which generally means those that have an external test set. But see note about option 014 below.)
Option 014. This is a rare option, and very few 8753s have it. This give direct receiver access to models which have an internal test set.

2. Add or enable software options 002, 006 and 010 on an HP or Agilent 8753.

If you have an 8753A, then it is only possible to add the time domain option (010). But on the 8753B, 8753C, 8753D, 8753E, 8753ES and 8753ET, it is possible to add options 002 (harmonic analysis), 006 (6 GHz) and 010 (time domain). Do not waste your time copying EEPROMs, as there's a much easier and safer way. Just email caesarv@email.com, with the serial number of your instrument, and what options you require. He will email you back some codes, which will unlock the options. You will need to search your service manual of your instrument to find out how to use the codes. On an 8753ES the procedure was:

Open the HP 8753 VNA.
Move a jumper on the CPU board that allows the EEPROM to be written to.
Enter the service menu, pressing some buttons listed in the service manual.
Set the title of the display to the same as the unlock code.
Press some more buttons, which are again detailed in the service menu.
Repeat steps 2-5 above for any other options required.
Put back the jumper that allowed the EEPROM to be written to. This will prevent accidental changes in future.
Put the instrument back together.

Be aware that whilst option 006 (6 GHz) will work without any hardware changes on the 8753B and 8753C, this option requires a new source assembly and recalibration on an 8753D, 8753E, 8753ES or 8753ET. It is probably not economically viable to add option 006 to a 3 GHz 8753D, 8753E, 8753ES, or 8753ET.

Adding software option 002 (harmonic analysis) or 010 (time domain), do not require calibration on any 8753 series instrument.

3. Differences between the HP/Agilent 8753 series VNAs - only 50 Ω models are listed.

There are a large number of differences between the different models, although all can be used with our calibration kits. Some of the key differences are listed in the following table. If anyone finds any errors, or can add any comments, please contact us and we will correct it. The system dynamic range figures only relate to the A and B receiver inputs, not the R receiver input, which has a much lower dynamic range than the A and B inputs. Some instruments have slightly different specifications over some frequency ranges due to spurs or other odd reasons. Please check the manuals for full details.

Feature	8753A	8753B	8753C	8753D	8753D (option 011)	8753E	8753E (option 011)	8753ES	8753ES (option 011)	8753ET
A photo			8753C		8753D option 011	8753E	8753E option 011	option 011 option 014	8753ES option 011	8753ET
Display	Mono CRT	Mono CRT	Color CRT	Color CRT	Color CRT	Color LCD	Color LCD	Color LCD	Color LCD	Color LCD
Lower frequency limit (without option 006)	300 kHz	300 kHz	300 kHz	300 kHz	300 kHz	30 kHz	300 kHz	30 kHz	300 kHz	300 kHz
Lower frequency limit (with option 006)	N/A	300 kHz	300 kHz	30 kHz	30 kHz	30 kHz	300 kHz	30 kHz	300 kHz	300 kHz
Upper frequency limit (without option 006)	3 GHz	3 GHz	3 GHz	3 GHz	3 GHz	3 GHz	3 GHz	3 GHz	3 GHz	3 GHz
Upper frequency limit (with option 006)	N/A	6 GHz	6 GHz	6 GHz	6 GHz	6 GHz	6 GHz	6 GHz	6 GHz	6 GHz
Is option 006 just software?	N/A	Yes	Yes	No	No	No	No	No	No	No
Integrated S-parameter test set	No	No	No	Yes	No	Yes	No	Yes	No	No
Integrated T/R test set	No	No	No	No	No	No	No	No	No	Yes
Floppy disk drive	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Time domain measurements (Option 010)	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Harmonic measurements (Option 002)	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Precision frequency reference (Option 1D5)	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Maximum measurement points	801	1601	1601	1601	1601	1601	1601	1601	1601	1601
Frequency offset mode (for mixers)	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
System dynamic range (30 kHz-50 kHz)	N/A	N/A	N/A	90 dB	100 dB	?	?
System dynamic range (50 kHz-300 kHz)	N/A	N/A	N/A	100 dB	100 dB		?
System dynamic range (300 kHz-16 MHz)	100 dB	100 dB	100 dB	100 dB	110 dB	?	100 dB
System dynamic range (16 MHz -1.3 GHz)	100 dB	100 dB	100 dB	110 dB	110 dB	?	110 dB
System dynamic range (1.3 GHz-3 GHz)	100 dB	100 dB	100 dB	110 dB	110 dB	?	110 dB
System dynamic range (3 GHz-6 GHz)	N/A	80 dB	95 dB	105 dB	105 dB	?	105 dB
Real time clock	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes
User defined preset	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Latest firmware	1.01	3.00	4.13	6.14/7.14	7.74	7.74	7.74	7.74	7.74	7.74

4. Loading the calibration kit coefficients - necessary unless you are using the 8753's default APC7 kit

An 8753 when switched on will default to one of the internal calibration kits - probably the 85031 7mm (APC7) calibration kit. If you are not going to use that kit, then you must load the coefficients for the kit. Lots of people fail to do this, and get poor results because of it, although they don't often known this, as they don't know how to check the results properly. The complexity of the process of loading the correct calibration kit coefficients depends on whether the kit is built into the firmware of the VNA or not. If built into the firmware it is very easy. If not built into the firmware, it is not hard to do, but is easier on the more recent models (8753D, 8753E, 8753ES and 8753ET) as these have floppy disks drives, whereas the old 8753A, 8753B and 8753C do not.

4.1 Loading the calibration kit coefficients for a kit in the firmware of the VNA

This is the easiest option, but a typical 8753 had about 6-12 kits in its firmware. HP, Agilent and Keysight have produced considerably more kits than this, so even using kits from HP, Agilent or Keysight, you will often find the kit is not in the firmware. We have in fact needed to load the coefficients for both the Agilent 85054B (type-N) and 85050B (APC7) kits we process, as neither are in the firmware of our 8753ES with the latest (7.74) firmware.

Power on, or press "Preset" if the 8753 is already powered on.
Press the CAL button on the front panel.
Press the CAL KIT softkey.
Press the SELECT CAL KIT softkey.
Press the softkey for the particular kit.

The coefficients for that inbuilt kit are loaded. You are ready to perform the calibration, as described in section 5 below.

4.2 Loading the calibration kit coefficients using other methods

There are a number of other ways to load the calibration kit coefficients into an 8753. Kirkby Microwave have a page that details how to set up and use calibration kits on an 8753

5. Calibration

There are many forms of calibration an 8753 supports, but the most commonly used, and most accurate are:

S11 1 port. Used for reflection measurements on port 1. Transmission measurements will not be accurate, nor will any measurements you make on port 2. Calibration requires 3 connections
- Short on port 1
- Open on port 1
- Load on port 1
S22 1 port. Used for reflection measurements on port 2. Transmission measurements will not be accurate, nor will any measurements you make on port 1. This requires 3 connections.
- Short on port 2
- Open on port 2
- Load on port 2
Full 2 port.Used for reflection measurements at either port, as well as transmission measurements. The full 2-port calibration provides everything that the other calibration provide, but requires 7 or 9 connections.
- Short on port 1
- Open on port 1
- Load on port 1
- Short on port 2
- Open on port 2
- Load on port 2
- Thru measurement, where the cable on port 1 is connected to the cable on port 2.
- Isolation measurement, where loads are connected on ports 1 and 2. (The isolation measurement is usually omitted, as it often leads to poorer results, whilst adding complexity)

Kirkby Microwave Ltd is registered in England and Wales, company number 08914892. Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Essex, CM3 6DT.