Upstairs 1st LO only has Khz resolution
12jun15
The 2-20 Ghz synths:
There are 2 hp83712 (10Mhz to 20GHz)
synthesizers that are used in the upstairs if/lo. They normally
have 1 hz resolution.
- hp1: this is the LO for the rf to if1 mixing (1st lo)
- hp2: this is used to generate the 2130 Mhz signal for the
sband. 250 Mhz from downstairs gets added to this to generate
2380 Mhz which then drives the sband exciter.
We own 3 of the hp32712 synths . A
few years back, (i think) the sband hp2 synth lost its ability to
maintain a constant output level (agc unlocked). That synth is now
down in the lab. It with replaced with the 3rd hp83712 synth.
We recently purchased an anritsu mg6392c synth (10Mhz to 20Ghz) as a
spare.
When the problem appeared:
On 28may15 we were looking for a narrow
tone from the stereob satellite (more
info). To check our setup, we generated a birdie at
8446.231359 Mhz (with the hp83712 synth downstairs).
When looking on the spectrum analyzer downstairs, and with the mock
spectrometers, the tone did not appear at the expected frequency. We
verified that the frequency generated downstairs was correct. At
first i thought i had messed up the if/lo setup (in the rush to get
things done).
On 06jun15 dana and i attempted to look at the
stereoA satellite. We again transmitted a tone to check that the
setup was correct. Looking at it through the if/lo it was again off
frequency. This time we checked everything carefully. We decided
that something must be unlocked upstairs (the received signal
downstairs was also bad).
On 08jun15 during test time, i looked at the hp1
synth more carefully. What i found was that it was only changing the
frequency in units of khz. Any part of the frequency below
1Khz would come out as 0
- eg: request 8446.231359 Mhz and it would output
8446.231000 Mhz
- The synth is supposed to have 1 Hz resolution.. The current
state had 1KHz resolution.
Felix verified upstairs that it only had KHz resolution when
inputting frequencies manually.
We aren't sure how long this problem has been
present. I know we had 1 hz resolution when we did the isee3
satellite tests in jul14..
On 12jun15 we replaced the hp83712 hp1 synthesizer with the anritsu
mg6392c .
Felix also found that the hp2 (sband synth) had its screen
covered with lint. It was not getting much air flow through it. He
cleaned the screens.
There also seemed to be a problem with the power switch for both hp1
and hp2 synthesizers. the switch wouldn't always turn on or
off.
The current state is:
- anritsu mg6392c synth as if/lo first lo
- hp83712 hp2 as sband synth
- hp83712: downstairs with auto gain control not working, but
frequencies ok
- hp83712: downstairs, agc works, but only has KHz resolution
- We do not have a working spare for the 2 upstairs
synthesizers.
- We could use the 1KHz resolution hp synth for the sband as
long as the transmitter offsets are done in the 250Mhz signal
downstairs, and not the 2130 Mhz signal upstairs (i think mike
has changed it so this is true for most regular (non-saturn)
runs.
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