Hello,
On Thu, Oct 22, 2015 at 12:30 PM, Alan Ibbetson alan@...
[hp_agilent_equipment] <hp_agilent_equipment@...> wrote:
I'm new to this group. I've diligently searched the archives but can
find no mention of early 8640B models seemingly intended to produce
+10dBm maximum output instead of the more usual +20dBm.
I have a pair of these 8640B signal generators, the early-model one
having been recently purchased so I can make IMD measurements on my
homebrew ham radio receivers. The other one I've had for some years has
the common fault with broken plastic gears and Paul K is helping me out
with this, hence in the meantime me putting the later purchase into
service and being "surprised" at the lower output.
The serial number is 1434U00265, so it's a 1974 model. The output range
switch has a scale marking at -140dBm and also one at +20dBm, but the
switch does not rotate beyond +10dBm. Does anyone know when HP increased
the power output? Does it mean this example doesn't contain the dreaded
monolithic output amplifier? Although the range/deviation switches use
proper wafers instead of microscopic spring fingers on plastic discs the
mechanically mad plastic gears are there so I suspect there will be
service work to do in the future.
I have both models, the output level range is basicly the same on
both, but the one with the amplitude dial with the -140 dBm mark can
go to +20 dBm too using the fine level knob. You'll notice that the
level full scale will change as you move the fine level knob and a
small mark under the large dBm marks moves to indicate the actual
output power.
HTH
Frank IZ8DWF
