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ARRL Warns Experimental Licensee to Avoid Interference to HF Ham Activity


The ARRL has asked a Massachusetts company that plans to conduct experimental transmissions over wide portions of the HF spectrum either to avoid Amateur Radio allocations or to announce the times and frequencies of their transmissions in advance. The FCC last fall granted MITRE Corporation of Bedford, Massachusetts, a 2-year Part 5 Experimental License, WH2XCI, to operate 21 transmitters at 10 fixed New York and Massachusetts sites. MITRE plans to test wideband HF communication techniques on a variety of bands between 2.5 MHz and 16 MHz.

“[I]t will not be possible for MITRE to operate these transmitters within the Amateur Radio Service allocations…without causing harmful interference to a large number of Amateur Radio operators on an ongoing basis,” ARRL Chief Counsel Chris Imlay, W3KD, said in a February 12 letter to MITRE.

Imlay said that if MITRE does not agree to avoid ham radio bands or to announce times and frequencies of transmissions ahead of time, it will ask the FCC to rescind the company’s Experimental License or to impose a prior notification requirement “in real time for each and every use of the transmitters authorized at each site.”

The WH2XCI Experimental License authorizes maximum bandwidths of 5 kHz, 500 kHz, and 1 MHz at effective radiated power levels of 6 W, 24 W, or 122 W. MITRE has indicated that most bandwidths would be between 100 and 300 kHz.

“At these power levels with the operating parameters proposed, it will be impossible to conduct your tests at any time within the Amateur Radio allocations and, at the same time, avoid harmful interference,” Imlay said. He noted that MITRE already conceded this point in a technical exhibit submitted to the FCC with respect to its 1 MHz bandwidth mode.

Imlay said that when interference from MITRE’s wide-bandwidth transmitters “inevitably occurs in the narrow-bandwidth, sensitive receivers” hams use, amateur licensees will have no way to determine the source of the interference or know to whom they might complain. “Thus, your assurance of operation on a ‘non-interference basis’ is meaningless under the circumstances, and yet that is both a special condition of operation” of the WH2XCI license and under FCC Part 5 regulations, Imlay told MITRE.

“It is ARRL’s intention to ensure that this experimental authorization, improvidently granted to the extent that it includes heavily used Amateur Radio allocations, is not permitted to cause interference to ongoing Amateur Radio HF communications,” Imlay concluded.

MITRE obtained the Experimental License to investigate high data rate wideband HF communication systems that exploit polarization diversity multiple input, multiple output concepts to expand the bandwidth of the communication channel.




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