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i (,~ · ~ ., / ...~ Ie. (\. d ve ," H f ",l ., .. I <- /', . T, th Re;) From: "Tomas E. Gergely" To: J4.J4{JREED) Date: 7/28/973:32pm Subject: and medical telemetry in Channel 37

Hi John:

Here are some answers to the questions raised this morning:

1) In the U.S., the following radio astronomy observatories should be protected in the 608~614 MHz (channel 37) band

1) 2) Green Bank, W. VA, in the NRQZ 3) The VLA, near Socorro, and 4) the 10 Very Long Baseline Array (VLBA) stations (8 in the continental USA, and one in and US Virgin islands, respectively) .

All sites are listed in footnote US 311, with coordinates.

There should be provisions for adding new sites. There is a lot of planning in expanding the VLA, by adding stations at a few U.S. sites, and radio astronomy should not be boxed into the existing locations in this important band.

2) Level of protection required.

Exclusion zones of 50 mile radii should be established around the first three of the above, and 20 mile radii around the 10 VLBA sites, which, because of their nature, are less SUbject to interference.

The distances are based on the following considerations; , , , j According to our conversation, the transmitters are going to operate at 200mV/m at a distance of 3 meters. This works out to (about) 10 milliwatts delivered to an isotropic antenna. Since I don't know the channel width, I assume 100 kHz, which works out to be about ~60 dBW/Hz. Alternately, one may consider the full 6 MHz width, to get ~75 dBW/Hz, or so. These figures are comparable to what an MES in the MSS was considered to put out in the 1610.6~1613.8 MHz band (-55--65 dBW/Hz) in the Big LEO Proceedings. We don't know the propagation characteristics at 610 MHz, but at L-band we are requiring 100 miles and 30 miles, respectively, based on available propagation models for single dish and VLBA telescopes. So, the numbers mentioned are not unreasonable.

It is also possible that, due to local terrain attenuation hospitals that are found closer than these distances could use the devices, but they should request permission from, and be willing to coordinate with the affected observatory.

Let me know if I can be of any further help before Thursday, when I leave on vacation, and business. I will be back on September 1.

Regards

Tom

J.".