The motivation to get this signal
generator was for testing military radios in the VHF low (30 - 90 MHz)
and UHF (200 - 400 MHz) bands. This series of generators are
available with different upper frequency limits by using modular
construction. This model is also the one used for testing pagers
when option 1EP is installed. This one has the pager option and
in addition to the built in pager modulation formats (POCSAG (512,
1200, 2400), FLEX & FLEX-TD (2 level FSK 1600 & 3200, 4 level
FSK 3200 & 6400)) (5 fixed built-in & 1 user defined message)
it also has an
enhanced audio modulation capability ( 10 Hz to 20 kHz sine, square,
triangle or sawtooth) when compared to a stock HP
8648A (400 Hz or 1 kHz sine).
The 8647 has 1 Hz resolution whereas the 8648 has 0.001 Hz
resolution. The switching speed and phase noise of the 8648 are
also better. These improvements were driven by the specs needed
for pager testing. The output can be adjusted from -136 dBm to +10 dBm in 0.1 dB increments by knob or keypad.
When working on my Precision Clock that accepts 2.5, 5, 10 or 20 MHz as
it's input heartbeat instead of feeding the clock directly from a
frequency standard I use the 8648 with an external reference connection
to either the GPS disciplined
PRS10 Rubidium or the
FTS4060
Cesium standard. The neat thing then is by using the frequency
knob on the left the frequency can be changed easily. This allows
setting the 1 Pulse Per Second edge in a very easy manner. It's
also a great way to test the frequency range that the clock will accept
without problems. When the clock is too slow the program loops
don't have enough time to complete which causes problems. If the
clock is too fast the PIC can not follow it. Both these are easy
to test with a knob for frequency. In a similar manner the power
levels & frequencies where the input circuit will trigger can
easily be checked.
[an error occurred while processing this directive] page created 26 Oct. 2001.
