FWIW, I have done PN measurements at 144 MHz with the TimePod and a
Frankenstein's laboratory lashup of 80 MHz ULN, HP doubler to 160 MHz,
HP mixer, and several amp and filter blocks. As far as I can tell, it
worked pretty well; at least, I could discern the PN difference among
several sources, some of them quite good.
Not sure why you are doing two oscillators/mixers, though. I used a 5
or 10 MHz reference directly into the TimePod, and the DUT fed through
the mixer. No need to increase the frequency of the reference to match
the DUT. But if you do want to mix both the REF and DUT channels,
wouldn't it be better to use a single source to drive both mixers?
John
----
On 10/17/20 8:59 AM, Gerhard Hoffmann wrote:
I'm trying to make a quick frequency extender for a timepod.
MCL PSC2-1 power divider, 2* SRA-1 7 dBm ring mixer, 2 DIL 80
MHz-oscillators
The oscillators can drive the ring mixers with just a coupling capacitor
and 50 Ohm
load limiting resistor. It is still a square wave at the LO port, but
the diodes in the mixer
would square it up on their own.
When there is no 5V-power, the oscillators are off and the LO inputs are
connected
to SMA connectors via the normally closed contacts of two reed relays.
Then the whole thing is passive and needs two external synthesizers.
Before I continue with the material I had in the junkbox, a quick
question to those
of you who have done that already:
Are 7 dBm mixers like SRA-1 good enough or is 17 dBm an advantage worth the
driver amplifiers? The usual signal generators max out at 13 dBm.
I have 2 17 dBm SRA1-WH, but it would require slaughtering something
unimportant.
How close must the oscillators be in frequency?
Have a nice weekend,
Gerhard, DK4XP
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