Alan You nailed it!
Thanks! jim ab3cv On Sat, Apr 18, 2020 at 3:46 PM Alan Bloom <[email protected]> wrote: > > Since noise power scales with the square root of the bandwidth > > > > That may be the source of the error. Noise power scales directly with the > bandwidth. (Noise *voltage* scales as the square root of the bandwidth.) > > > Since the P3's effective bandwidth is 11 Hz and the K3 sensitivity is > specified for 500 Hz, the P3 should be showing > > 10 * log (500/11) = 16.5 dB lower than the P3. > > > If the P3 is reading -162 dBm, then that corresponds to -145.5 dBm on the > K3, close to the -145 dBm spec. > > > Alan N1AL > > > > On 2020-04-18 12:33, Jim Miller wrote: > > I'm doing some work on measuring RFI levels on 6m at my QTH. > > One tool I'm using is the P3 with averaging set to 20 to make for easier > reading. > > With the K3s preamp 2 engaged I read -162dbm on the P3 scale when connected > to a 50ohm dummy load. > > I'm trying to correlate that to the MDS numbers for the K3s. > > The K3s specification with Pre2 engaged is -145dbm measured in a 500hz > bandwidth. > > The effective bandwidth of the P3 per the P3 manual is Scale/450 which for > 5K that I'm using is 11hz. > > Since noise power scales with the square root of the bandwidth that > should result in a ratio of SQRT(45) or 6.7. 10*log(6.7) = 8.2 > > Adding -162 to 8.2 only brings me to -153db. > > So it seems I'm missing something. The P3 is telling me the K3s is 8db more > sensitive than its specification. > > What am I missing? > > Thanks > > JIm ab3cv > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [email protected] > > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
