HP 5087A replacement card design changes

[HalFoster]

All-

I have recently designed replacement boards for my HP 5087A frequency distribution amplifier – the input preamplifier and pretty much an exact copy of the original, a combined (selectable at build) 10MHz to either 5MHz or 1MHz board and a single wideband amplifier for the outputs.

Everything works fine and within the original specifications but before ordering parts for more boards I started rethinking my approach to the whole thing. Originally, I tried to duplicate the original functionality but updating to modern components and streamlining somewhat; after building and testing the trial cards, however, I realized that a different approach might make sense.

The signal source will always be 10MHz from a Spectracom 8195A GPS receiver so instead of the general-purpose input amplifier I think it would be better to have it targeted to the input signal with heavy bandpass filtering at 10MHz. The current divider cards mirror the filtering of the original but could have stronger BP filtering as well. Then the output amplifiers could be simplified to just be amplifiers with no targeted filtering. As there are twelve of them that saves considerably on the part cost for a fully populated chassis.

So, is there something that I’m missing? From a performance standpoint my feeling is that nothing will be worse and will probably improve. Another consideration that I have is that I currently have a total of 5 of the 5087A units – I’ll probably replace my Brandywine FDA1050 with one of them and possibly keep a second for backup. That leaves at least three that I will sell, and I don’t have enough cards to fully populate all of them. My thought was to include enough of the amplifier cards for free to complete the full twelve slots (blank cards – all through hole construction) so the purchaser could build them or not as they desire. Maybe offer built ones for a profit if anyone wants that, but the designs and the Gerbers I’ll post on the HP groups.io sites file area so I would like to make sure the cards meet the needs of those other than myself as well.

Comments?

Hal