Friday, October 29, 2010

What is wrong with operating FM simplex between 145.8 and 146 MHz? ...

Q What is wrong with operating FM simplex between 145.8 and 146 MHz? I hardly ever hear signals in that part of the band.

A This touches on the issue of voluntary band planning, which was addressed in “Washington Mailbox” in the December 2000 QST. You might want to take a look at that column.

The problem with operating in the 145.8 to 146 MHz segment is that the amateur satellite community uses this portion of the spectrum. There are several FM repeater satellites that operate with uplinks in this segment. If you’re chatting with a local friend on 145.85 MHz, for example, there is a chance that OSCAR 27 will hear you and relay your conversation over thousands of miles without you even realizing it! The FM satellites are crowded already, so they don’t need “unintentional signals.” Other SSB and digital satellites have uplinks here as well, and your signals could make it impossible for these birds to hear the signals intended for them.

SO-35 and AO-10 have downlinks in this portion of the band. These signals are often weak and your terrestrial FM QSOs will obliterate them.

Just because you can’t hear the satellite signals, doesn’t mean that they are not there. With the typical FM setup, you’re not likely to hear satellites in this portion of 2 meters at all.

Voluntary band planning allows everyone to enjoy Amateur Radio in all of its various forms, but it only works if we all respect the plans. It isn’t so much a legal issue as it is one of common courtesy. 

From QST February 2001