A recap of yesterday's very interesting presentation on 26 MHz DRM at the SWL Fest in Kulpsville, PA:
The speakers were Ben Kobb (who maintains the 26mhz.us website) and Don Messer (chairman of the DRM Consortium Technical Committee). Main points discussed:
1) The "11 meter" HF segment from 25.67 to 26.10 MHz is already allocated to international shortwave broadcasting in the US, but presently of little interest because the band is usually not open to skywave propagation except during sunspot cycle peaks, and is outside the range of many inexpensive AM shortwave receivers.
2) However, it could be used in a line-of-sight mode for local broadcasting, similar to FM. If 10 kHz bandwidth DRM is used, 43 channels could be made available.
3) Problems with distant skywave interference during sunspot peaks can be minimized if stations install antennas with a special elevation pattern, such as this TCI design: http://www.tcibr.com/26-mhz-local-coverage.html
4) Propagation models predict that the interference situation will not be a major issue if such precautions are taken.
5) Tests conducted in Mexico City and other parts of the world have been encouraging:
http://klixie.textdriven.com/26mhz/index.php?id=9
6) So now, it's a matter of putting some experimental stations on the air in the US, running interference tests, and presenting data to the FCC in hopes of getting the rules changed to permit local service in the 26 MHz band. However, it remains to be seen if the NAB will permit the FCC to act in favor of this proposal.
We also learned that the 26 MHz experimental license request which was denied by the FCC last year was rejected because the application was defective, not because the Commission opposes further testing in this band.
The speakers were Ben Kobb (who maintains the 26mhz.us website) and Don Messer (chairman of the DRM Consortium Technical Committee). Main points discussed:
1) The "11 meter" HF segment from 25.67 to 26.10 MHz is already allocated to international shortwave broadcasting in the US, but presently of little interest because the band is usually not open to skywave propagation except during sunspot cycle peaks, and is outside the range of many inexpensive AM shortwave receivers.
2) However, it could be used in a line-of-sight mode for local broadcasting, similar to FM. If 10 kHz bandwidth DRM is used, 43 channels could be made available.
3) Problems with distant skywave interference during sunspot peaks can be minimized if stations install antennas with a special elevation pattern, such as this TCI design: http://www.tcibr.com/26-mhz-local-coverage.html
4) Propagation models predict that the interference situation will not be a major issue if such precautions are taken.
5) Tests conducted in Mexico City and other parts of the world have been encouraging:
http://klixie.textdriven.com/26mhz/index.php?id=9
6) So now, it's a matter of putting some experimental stations on the air in the US, running interference tests, and presenting data to the FCC in hopes of getting the rules changed to permit local service in the 26 MHz band. However, it remains to be seen if the NAB will permit the FCC to act in favor of this proposal.
We also learned that the 26 MHz experimental license request which was denied by the FCC last year was rejected because the application was defective, not because the Commission opposes further testing in this band.