Sweeperino is dated. The Antuino that I posted a few weeks ago is a far better device. It is almost a spectrum analyzer, a very good antenna analyzer and an SNA rolles into one. It uses ans Si5351 instead.

The sweeperino used the $10 si570, Farhan got it  down to 4mhz, CMOS out version goes up to 160mhz, popular for over a decade.
The si514 is similar to the si570, 100khz-250mhz, came out later and doesn't have much of a following in the hobbyist community.
The si5351 (as used on the Raduino) is 4khz-225mhz, is only $1 and can provide multiple clocks. 
All three of the above operate from 3.3v.  (Probably don't want the 1.8v and 2.5v si570 variants, and be sure it's the CMOS out)

So you could start with a Raduino (already has the si5351) as MMR suggested.
Or start with a Nano, an si5351 breakout board (Adafruit/QRPLabs/Etherkit), and an i2c LCD display with pullups removed.
Then add some sort of detector (either an ad8307 or diode detector) that feeds an ADC input of the Nano..
You may be writing software for this (replace the sweeperino's si570 code with the uBitx's si5351bx routines).
If you don't want to write code, perhaps somebody in this forum already has or is willing to take it on.
Alternately, just follow Farhan's sweeperino recipe using his CMOS 3.3v si570, and use the Nano software he posted. 

Jerry


On Wed, Feb 13, 2019 at 12:22 PM, Michael Hagen wrote:

I looked at the schematic for Sweeperino.

When I go look at Mouser, the SI 517 is only for 3.3V.  And it starts at 10 MHz.

There is a 514?  Goes down to 100Khz.  I wonder if the Library works with that one too?

Both I2C.

Thanks for any info.

Mike, WA6ISP