You have already described it yourself. The terminology dates back to the 1960's-70's when offsets were measured using trace oscilloscopes to see the visual representation of the frequency difference between two stations close in frequency. An audible heterodyne was often not present with differences of a few kHz, thus 'subaudible'. Visually, you could 'see' the offset, and sometimes the beat between the two signals which might or more likely not be audible. So you saw the SAH on the scope. You used the same equipment to determine the actual offset value.
You could also manually count the beats - audibly or visually, as applicable - to determine the offset. Russ Edmunds 15 mi NNW of Philadelphia Grid FN20id <[email protected]> FM: Yamaha T-80 & Onkyo T-450RDS w/ APS9B @15'; Grundig G8 AM: Modified Sony ICF 2010's barefoot --- On Fri, 9/7/12, Tim Tromp <[email protected]> wrote: > From: Tim Tromp <[email protected]> > Subject: [IRCA] 738 & SAH's from Michigan - Friday morning 9/7/2012 > To: "[email protected]" <[email protected]> > Cc: "ABDX" <[email protected]> > Date: Friday, September 7, 2012, 6:51 AM > 738 Tahiti is already in this morning > @ 1030 UTC with some audio, but > I'm plagued with t-storm noise right now. I'm also > seeing a carrier > fading in and out on 737.8 - has anyone noticed this > before? It's been > here the last few mornings and always disappears or fades > out completely > by 1100 UTC. The fading would suggest that it isn't > local, but I could > find no reference to anything being so far off frequency > here. > > I see a lot of talk about SAH's (sub-audible hets I > presume?). Can > someone provide good audio demonstrating this phenomena? > > Thanks, > Tim Tromp > West Michigan > > _______________________________________________ > IRCA mailing list > [email protected] > http://montreal.kotalampi.com/mailman/listinfo/irca > > Opinions expressed in messages on this mailing list are > those of the original contributors and do not necessarily > reflect the opinion of the IRCA, its editors, publishing > staff, or officers > > For more information: http://www.ircaonline.org > > To Post a message: [email protected] > > _______________________________________________ IRCA mailing list [email protected] http://montreal.kotalampi.com/mailman/listinfo/irca Opinions expressed in messages on this mailing list are those of the original contributors and do not necessarily reflect the opinion of the IRCA, its editors, publishing staff, or officers For more information: http://www.ircaonline.org To Post a message: [email protected]
