On Thu, Jan 10, 2019 at 12:07 PM, Jerry Gaffke wrote:
Something like PX1002 SAW filters at 86.85mhz might be a better choice than 10.7mhz for a second IF, avoid image trouble.
Now I'm using 110MHz as second IF and 10.7MHz as 3rd IF (for the resolution filters)
Or just mix down from 915mhz to I/Q baseband and use SDR techniques?
I did this for my own build VNA that can run in SA mode with switchable DSP resolution filters
The W7ZOI spectrum analyzer front end uses the mixer's IF port for the incoming signal,
RF port is outgoing, because the IF port can get down to lower frequencies.
Doing the same
Here's the entire line of MiniCircuits mixers:??
On the ADE-1+,? LO/RF ports are 0.5-500mhz, the IF port is good from DC-500mhz.
The ADE-11X is suitable for higher frequencies, but your minimum signal into the SA will be the 10mhz limitation imposed by the IF port.
The limit actually does not exist. I'm using the ADE-11X in another project and it goes down to audio frequencies
The ADE-5+ might be a better choice,? LO/RF ports are 5-1500mhz, the IF is good from DC-1000mhz, so our SA could see from 0mhz to 1500-915=585mhz
And could perhaps press further than 1500mhz on the LO port.
Cheap as I might be, spending the extra buck on an ADE-5+ to be able to see the bottom 10mhz seems like a good deal.
.
All diode double balanced mixers will go down to DC on their IF port
I'm curious how well behaved that ADF4351 local oscillator of yours is.
Ah, indeed, not so easy to get rid of the spurs, low noise AND have a fast sweep. Lots of register tweaking. SI5351 are much simpler to use!!!!.
The new si549 (like an si570, but solid coverage up to 1500mhz) would also work, with much finer resolution in selecting the frequency.
Or an si5340 (4 channels, up to 1024mhz) followed by a clock doubler, cheaper and get multiple LO's for 2'ed IF, tracking generator, ...
?
Mostly armchair engineering here, but I am trying to build a simple single conversion SA?
using the ADE-1+, two PX1002's, and an AD8307.? (Also a couple MMIC's, front end LPF, si5351, Arduino Nano clone, etc)
How would you do the resolution filters?
Those PX1002's are $12 quantity one, but otherwise this is throw-away cheap to play with.
AD8307's can be had on ebay for down to $0.30 each, reportedly work well enough? Factory seconds, slightly out of calibration?
Suggest to look at the AD8307 data sheet and consider adding a AD603 as shown in one of the examples in the datasheet. I did and it gives you 130dB measurement range, even when build in dead-bug style!!!!
Success with your build
