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Does anyone know if it is possible to retrofit EFC to an 8662A? It
was offered with the option 003 (absolute phase noise limit on the
640MHz output at rear), but the service manuals available to me only
appear to show terminals 5 linked to 6 on the 10811 10MHz reference
oscillator which is the configuration for not using EFC.

(A cable can clearly be added, but as with everything on the 8662A
keeping the phase noise down is critical and I could imaging doing
this in a suboptimal way might simply be adding undesirable
modulation).

I'd like to be able to use EFC in a phase noise measuring setup rather
than FM modulation.

Alan

Alan,

I equipped my HP8662 with an EFC-Input for phase-noise measurements
with a HP11848 Phase Noise Interface. On the attached image with an extract
of plate 18 of the service manual you can see my modification (blue).

The green curve in the small graph shows the resulting frequency deviation with
a variation of the input tuning voltage over a range of +10.0 ... -10.0 Volts.
One can see that the resulting frequency deviation covers a range of
approximately 25.0E-08
The purple curve is a comparison with a HP8644B which is by default equipped
with an EFC-Input.

I hope that this helps.

Kurt

Thanks very much for this! That is exactly the information I needed and I am glad to know someone has been this way before me and it worked. I also want to use this with a 11848 interface.? It's working at the moment but using the FM input which let me test my software (I'm not using a 3561 so the official HP software isn't much help here), but for measuring low PN sources the manual is suggesting moving to EFC and I couldn't find the jack and then realised it was an option!

Alan?

On November 22, 2023 3:18:40 PM "Alan Bain" <alan.bain@...> wrote:

Thanks very much for this! That is exactly the information I needed and I am glad to know someone has been this way before me and it worked. I also want to use this with a 11848 interface. It's working at the moment but using the FM input which let me test my software (I'm not using a 3561 so the official HP software isn't much help here), but for measuring low PN sources the manual is suggesting moving to EFC and I couldn't find the jack and then realised it was an option!

Are you writing new PN software for the 11848A?

- Dave

--
Dave McGuire, AK4HZ
New Kensington, PA

Not in the sense of rewriting all the original basic software in its entirety. I'm only interested in the PLL mode of measurement and am particularly interested in doing cross correlation measurements with a pair of 11848s and separate references to reduce the influence of reference source noise.? This needs a 2ch DSA (like the 3563) and the original HP software was very tightly bound to the 3561 (given how different the HPIB command sets are for these DSAs it is hard somertimes to believe the same company made them).? But obviously the first step in this is to do 1ch standard measurements, so I have C++ software that replicates most of the functions of the PLL measuring mode + calibration + PLL characterisation.