So cool that Alan did this. Here we see a rigrourous measurement of the MDS of our receiver, with a correction for the bandwith. Very nice.
It can discern signals down to -125 dbm. I think that is pretty good for simple receiver like this.
Alan agrees that another way to do the sensitivity test is to just listen for the band noise when you connect and disconnect the antenna. Especially on the low HF bands, if you can hear it, you have sort of maxed out on receiver sensitivity.
Thanks Alan!
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Alan is a great mentor
ReplyDeleteWN2A
ReplyDeleteWhat Alan refers to is the MDS runs -117dBm in the Soldersmoke DCR by itself, with its BW=3300 Hz. That might be typical of what you might use on voice or a little wider. If we add a 500 Hz BW filter, then we will see MDS ~ -127 dBm. These numbers are right in line with the MDS calculated values. A builder should get results comparable to these.
ReplyDeleteAlan's measurements allows us to calculate the DCR's Noise Figure. At MDS=-117dBm; BW=6600 (it's double-sideband noise); kTo=-173dBm/Hz, that works out to NF ~18.8dB. This is plenty good in a somewhat typical noise enviroment on 40 meters where Fa ~ 40dB(!!) . See ITU-R P.372-13, pg 5, Fig 2 and pick a curve that you think appropriate for your receiving antenna's enviroment .
So, great results!--73 WN2A