TSP #30 - Agilent 53131A Universal Counter Upgrade OPT-030 Analysis and Experiments 

Dave.. It would be great if you and Chris could get Shahriar on to The Amp Hour?

Thanks Dave. Let us know once you upgrade your unit.

Thank you. Yes, there will be more videos of course.

One more coming up tomorrow! With a little surprise. :)

The division ratio is fixed, it does not change. So all the divider does is that in translates the input frequencies of 0.1 to 3GHz to a lower range, for examples, divides everything by 64 which then the instrument can count.

It is shocking how much these companies markup the prices on the OEM parts for these devices. If you look at the BOM+ manufacturing costs of more specialized devices, on sites like electronics360.globalspec.com/teardowns/archive?page=1, you will often see that the closer you get to equipment used in the IT field or by engineers, the higher the pricemarkups get, and with the exception of devices like google glass and portable bluetooth speakers (where the fad has allowed for some truly astronomical price markups), the price markups on this equipment will often put just about any consumer electronic company to shame.

Razor2048 That's how things are unfortunately. Companies make item A for dirt cheap and sell it for 5 trucks worth of gold. Then you ask yourself, where the hell does that money go if it's not in the item i pay?!?!? As i see it, it's a circle jerk of advertisement, research, product, rinse and repeat. And considering the gargantuan prices that the advertisement world requires one can surmise it all goes in to brain washing us to buy more products so we can be brainwashed some more. (brainwashed used in the dark comedy sense). Meh, it's good that people come up with these mods. It bypasses the corner these companies have stuck themselves in to by propagating the same prices from way back when. Today producing a machine whatever might it be will never be as expensive across the entire field of it's existence from incipience to final product, as it was years, decades, ago. It just can't. We know more, we've come up with a s-load of methods of manufacture, testing has become obsolete (in a way) because of mass production and programs that allow us virtual interfacing etc. Rambling.

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Yes, you are right. Junction capacitance of the diode appears in parallel to the input impedance of the amplifier and thus limiting the bandwidth. For this board, expensive diodes were used to ensure the bandwidth exceeds 3GHz.

Not only stray capacitance, but I'm guessing the recovery time of the diode matters too. I'm guessing that if the recovery time is too long, a high frequency signal that overloads the input will not just be clamped to the diode's turn-on voltage, but almost completely attenuated by the diodes.

you beat me to it.! ;)

The diodes at the output of the amplifier chain protect the divider from large signal swings when the last stage is saturated. So adding more stages won't harm the divider. However, at some point, the gain of the path would be too high and various noise sources will start to trigger the divider because they will be amplified. Furthermore, the isolation from the output of the amplifier to the input is limited, and you can actually cause an oscillation if not careful.

From what I've read, crystal aging (frequency change over time) is increased by temperature changes, which would suggest that to avoid aging, you want to leave your reference clock on all the time so that the temperature remains stable. Anyway it needs to be left on for hours (in the case of a high grade OCXO) to stabilise before usage. The heater is just a PID controlled resistor, so I wouldn't worry about it as a point of failure, especially as it's current will decrease as it reaches target temperature.

i have done a little search around i think chip on this board is not MC12079.

You are correct in a sense that if I had an ideal inductor of very large value, I would in theory isolate the Vdd pin of the amplifier from the impedance variation of the Vdd trace. However, the inductor is not ideal and its value is not infinite. Therefore, it is possible to imagine a scenario where it could resonate with the impedance of the Vdd trace at a certain frequency and create some problems. Although, the series resistor to the inductor helps too as it reduces the quality factor of the inductor and thus dampening any resonances.

@@Thesignalpath Thank you so much, I really appreciate your videos, comments and help!