DIY 200MHz analogue spectrum analyzer. Does it worth it to build nowadays?

[neazoi]

Hello, I consider making a small cheap (~ $100) spectrum analyzer for 0-200MHz with -75dB sensitivity. This is a standard superhet design using an opamp sweeper, mini circuits LO, mixer and a helical filter, followed by a chip to perform the rest of the functions. There will be two switched resolution bandwidth filters, one using ceramic filters (wideband) and one using crystal filters (narrowband). I believe this should give enough resolution at slow sweep rates, to monitor the transients of an ssb signal.

Note that it is intended for the radio amateur, not the proffessional.
I already own a 500MHz SA (FFT function of my scope), but the analogue SA seems very straight forward. Just to mention that my Tektronix 491 is not capable of below 10MHz, which is not good for radio amateur purposes.
Looking at ebay, for prices comparison, I could not find a 200MHz or so SA and some similar products use FFT (as expected) and whereas they combine a scope with the SA, they cost more. On the other side these TV tuner based SAs are useless since they begin from 40MHz and up.

You may have more experience in this topic so I would like to ask if such a project is worth to build nowadays if it can be done at ~ $100.

It seems that the SA, even the simpler ones, is still an expensive instrument, despite the advance in technology. So it is worth it to build a simple one?

 

[Kripton2035]

take a loot at the rf explorer. it should suit your needs and price.
https://rfexplorer.com/

 

[neazoi]

take a loot at the rf explorer. it should suit your needs and price.
https://rfexplorer.com/

Thank you for the link

15 MHz up to 2700 MHz, not good for amateur use, they usually require form 137KHz and up.
Price starts at $119 but the frequency range is very limited. For 15 MHz up to 2700 MHz price is much more.

Do not take me wrong, my purpose is not to compare products, but to see if it is worth it today to build an analogue SA with the specs mentioned in post #1 at about $100.

 

[davenn]

take a loot at the rf explorer. it should suit your needs and price.
https://rfexplorer.com/

hey Kripton

what a neat little unit and such an affordable price, thanks for the link

cheers
Dave

 

[jiripolivka]

If you want and enjoy building such SA, OK. I have bought a Chinese USB SA covering 200-900 MHz for $120, and it is calibrated from 0 dBm to -100 dBm. I doubt you can make it cheaper, and soon more low-cost devices are coming to the market.

 

[davenn]

If you want and enjoy building such SA, OK. I have bought a Chinese USB SA covering 200-900 MHz for $120, and it is calibrated from 0 dBm to -100 dBm. I doubt you can make it cheaper, and soon more low-cost devices are coming to the market.

he would still have the problem of it not covering the freqs he's interested in and would have to mess around with mixers etc

Dave

 

[neazoi]

he would still have the problem of it not covering the freqs he's interested in and would have to mess around with mixers etc

Dave

Indeed! That is why I am asking about this, because I have not seen such an SA on the market cheap.