The AM Forum

I was thumbing through some old QST's and handbooks from the 30's last night, and reviewed some of the pre-war subband arrangements.  Interesting.

Prior to 1932, there were no subbands on 160, just as it is now.  On 3.5-4.0 mc/s, there was an 80-metre phone band, 3500-3550.  No phone on 40 or 10.  On 20, with a special licence and permission from the Radio Inspector, you could run phone on 14.1-14.3 mc/s .  The entire 20m band went from 14.0-14.4mc/s.

In 1932, at ARRL's request, the FRC (Federal Radio Commission) approved changes to the phone allocations: Phone operation on 160 (1715-2000 kc/s) would be restricted to 1875-2000.  The reasons given were that the sunspot cycle would be bottoming out within the next couple of years, and much of the regional cw activity on 80m would have to move to 160, due to the expected 80m skip zone, so they wanted to reserve the lower end of the band to cw.  Another reason was BCI.  At that time, BCI from 160m phone was almost as much a headache to amateur radio as TVI was in the 50's.  So the thinking was, move 160m phone up to the top end of the band, and that would increase the frequency space between the broadcast band and 160m phone.  The top end of the BC band ended at 1500 kc/s then.  However, less than a year later, at ARRL's request, the phone subband was extended back to 1800-2000.  1715-1800 remained cw only.

The 80m phone subband was moved from 3500-3550 to 3900-4000.  Canada opened up the 3900-4000 kc/s subband, but Canadian hams could continue to use the old 80m allocation as well.  One of the reasons for moving the US allocation to the top end of the band, was interference to aircraft communition just below 3.5 mc/s.  That wasn't the hams' fault; aircraft receivers of that era were simply too non-selective.

No 40m phone operation was allowed before WW2.  40 was opened up to phone because the foreign broadcast interference was causing amateurs to vacate the top end of the band, and it was hoped that a phone allocation would bring amateurs back to the upper frequencies.  There was fear that the US might also reallocate the top end to broadcasting if it wasn't being used by amateurs.

The phone subband on 20m was reduced from 14.1-14.3, to 14.15-14.25.  Phone operation on 20 back then was kept in the middle of the band to reduce the liklihood of out-of-band spurs from phone stations interfering with other services.

There was no 15m band before WW2.

At first, 10m was cw only, just like 40.  Then a small phone subband at 28.0-28.5 was opened, later to be expanded to 28.0-29.0.  The entire band was 28.0-30.0 mc/s.

The 80m and 20m subbbands were made "class A."  Incentive Licensing 1932 style; hams without the class-A ticket had to vacate 80 and 20, even if they previously had the RI's permission to use those bands.  The class-A licence required no further code test, and the written test was limited to topics directly related to radiotelephone operation.  There was a mandatory one-year waiting period that an operator had to be licensed before he could take the class-A exam.

In addition, there was an "Extra First Class" amateur licence, but it carried few additional privileges, much like the Extra Class before 1968.