Well I only tried (yesterday) with the distribution amp, which is the highest, that's why I find it strange, do you think it's still not enough ?
I'm still reading on harmonics. I don't fully understand everything, can you give me a one or two line explanation about your last suggestion please ?
And yes, the switch felt a bit wonky. But I could clearly see two states, either the normal internal ref, or that 'all segment lighted up' state. Maybe I need to give it more time ? Usually, when there's something that I don't expect, I quickly shut it off and research more, to be sure that I'm not damaging stuff !
Ok. first thing, the 5345A ext ref input accepts not only 10MHz, but sub harmonics like 1MHz, 2, 2.5, and 5MHz. The PLL of the internal OCXO can lock in to all of these frequencies.
Please allow your instrument more time to lock-in on the external signal, obviously the PLL needs some time, but I have no clue how long, as this is not described in a detailed manner in the manual. To shut off when something odd happens, in this case is not necessary, as you can't damage anything.
You're seeing a working state, obviously when on internal, the display is updated and everything is running well.
The other state with all segments lit up (that is the LAMP TEST mode) is a non-functional state, very obviously, so the OCXO can not properly lock to the external frequency, either because the PLL is not working properly, or because the external signal is too weak, or simply is not connected properly via switch S9. The detection and behavior of the display is described in paragraphs 4-127 .. 4-131.
My 5370B has some similarities with the 5345A, they both share the same input front end, for example.
The external switch on my unit does not work properly any more, so I have to push a bit harder to the external position, until the ext. 10MHz is fed through.
That might be similar on your unit, so also try to wiggle this switch.
Frank
Edit: I just successfully tested the TALK ONLY mode on my 5370B, this probably works on the 5345A identically. Flip the switch on the rear to TALK ONLY.
On the counter, set up the measurement mode like frequency, T.I., the gate time/ resolution.
Set the parameters in TimeLab accordingly, then press MONITOR, and you may see the incoming samples like in the picture.
If you press START, TimeLab will acquire the samples, and inside MEASUREMENT you can chose which mode you want to get analysed, i.e. T.I. ADEV, or frequency difference