Tuesday, November 18, 2008

909 or 910?

I spent some time before work this morning pondering what to do about M-LMS licensees in the 33 cm band. M-LMS is the Multilateration Location and Monitoring Service. In the 90s, the FCC held an auction to grant nationwide licenses for this service. In the meantime, the growth of GPS has made the whole thing largely moot. Still, we amateurs must not cause harmful interference to them, to the extent that they actually use their licenses. The sooner those licenses are revoked, the better, I think, as there clearly is no public benefit to them.

There is a block of L-MLS allocation that ends at 909.75 MHz. If the last 750 kHz of this grant are in use, then I will have to change from 909-915 to 910-916 MHz. Fortunately, this is still a reasonable choice. On the TVC-9S, it's channel 2 instead of channel 1.

The only issue is the NARCC band plan for 33 cm, such as it exists. That band plan has ATV at 909-915 and a digital allocation at 915-917.

This doesn't really square all that well with the reality on the ground, given that potentially the range between 904 and 909.75 Mhz is the M-LMS block A allocation.

The NARCC plan also has an ATV channel on 922-928 MHz, which means it overlays the repeater output band at 927-928 MHz. That doesn't make sense.

The Mt. Diablo ATV folks have a repeater output from 918-924 MHz. This makes sense.

What would make sense in addition would be for NARCC to move the digital sub band from 915-917 to 916-918 MHz, move the lower ATV channel from 909-915 to 910-916 MHz, and recognize the reality that M-LMS probably denies us access to 904-910 MHz.

What am I going to do?

Well, it rather depends on whether there are current digital users between 915 and 916 MHz here in the Bay Area and/or the M-LMS license holder is actively using 909.0-909.75 MHz.

I can only hope and pray that both aren't true. If they are, then I will have no choice but to operate on 910-916 (since I can't interfere with M-LMS) or share 918-924 with Mt. Diablo. Both of those options would likely suck.

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