Monday, October 19, 2009

ARRL Approves Study Committee to Research & Develop Plan for Narrowband


Minutes of the 2009 Second Meeting
ARRL Board of Directors

Teleconference July 17-18, 2009

29. On motion of Mr. Sarratt, seconded by Mr. Frenaye, the following resolution was ADOPTED:

WHEREAS, there is current substantial amateur radio movement, activity, and innovation in the digital narrowband area; and

WHEREAS, the FCC has mandated that by 2013 commercial radio move to narrowband channels and Amateur Radio manufacturers normally follow commercial practices; and

WHEREAS, the VHF/UHF Amateur Radio band plan currently uses 15 and 20 kHz FM channels; and

WHEREAS, with the increasing use of narrowband across the country amateurs are placing and using narrowband equipment outside the repeater subband because there is no real place to fit the narrowband pairs; and

WHEREAS, for ARRL to remain a respected leader in technology, we must be actively involved in innovative solutions to problems by bringing about a productive discussion on a technical paradigm shift; now

THEREFORE, the President shall appoint a study committee for the purpose of research and to consider developing a plan to move the US amateur community to narrowband channel spacing.

I would be in favor of this IF it meant there was some thought behind it. It would be nice to clear a few ~50 KHz wide channels on 2 meters for higher speed data applications. This of course should go hand in hand with some other modernized regulations.

Promoting narrow band just so we can accommodate more repeaters (more of the same) is a poor reason. Perhaps if there was less effort to squeeze in more repeaters, this would promote exploration of other bands.

Tuesday, October 6, 2009

FCC ferrets around for spare spectrum


FCC ferrets around for spare spectrum -Got any ideas?
By Bill Ray

The FCC is asking for suggestions in the hunt for more radio spectrum, having established that there's not going to be enough to support the next generation of broadband requirements.

The US regulator wants ideas for making better use of all the spectrum below 3.7GHz, and it wants them by 13 November 13. It's asking (pdf) for suggestions on what spectrum should be used for what and how to get hold of it.

The consultation is part of the National Broadband Plan, which has been inviting the industry to say how much radio spectrum it needs. Surprising as it may seem, the industry thinks it needs lots and lots more radio spectrum if it's going to serve customers with the sort of quantities of data it thinks they would like, as the FCC explains:

"According to Wireless Communications Association International (WCAI), a traditional handheld device, with average customer usage patterns, will consume about 30 megabytes of data in a month, a single smart phone consumes 30 times that amount, and a single connected notebook or laptop computer is consuming 450 times that amount."

So you smartphone users out there are already burning through 900MB of data a month, while laptop users are consuming more than 13GB every 30 days or so. That seems like an awful lot to use, though that includes voice traffic.

Still, the FCC is taking those numbers seriously, and it wants to know how much bandwidth you think the wireless industry is going to need. It also wants to know where that spectrum should sit, both for fixed and mobile wireless services, and suggestions to encourage existing users to hand it over for reallocation to wireless broadband.

The FCC has the same problems as the rest of the western world: Huge swathes of the radio spectrum were allocated to governmental and military operations that have no incentive to make use of it or even to keep track of which bits they are actually using.

UK regulator Ofcom's solution is to charge everyone for spectrum usage. Though calculated rates if it can't get the spectrum onto the auction block. But that's not always a good idea (billing lifeboats for radio frequencies is not good PR), so the FCC is hoping the general public can come up with something better.

The regulator is open to suggestions from 23 October until 13 November, and we look forward to hearing what the American on the street has to say on the matter.

All of 900MHz, 1.2GHz, 2.4GHz ,3.4GHzand 5.8 GHz don't even total 800 MHz of spectrum! Can you list the times the ARRL has encouraged life above 902 MHz in QST in the last 5 years?

.. oh yeah priorities... 4 MHz of HF spectrum, my bad!

Thursday, October 1, 2009

The range of D-Star

Several Digital Voice operators have reported hands down, absolutely no question, tested it for months, the D-Star is usable for reliable (non-garbled communications) for mobiles about 10% or less of the coverage area of the Analog FM and for base stations about 80%. This is largely due to the picket fencing of a mobile signal, multipath for non line of sight, etc. On a high peak in the desert with line of sight, one can imagine them being comparable, but not in the real world of trees and buildings.

Yes the R2D2, digital garble on P25 and D-Star transmissions is due to multipath. Experience is that 2 meters is more prone to R2D2 issues than 70cm Partially because 70 centimeters penetrates buildings better. So yes analog copies with some conditions better than D-STAR. Mobile, multipath for one.

Here is a sample for those curious but not actively experimenting:

Digital voice should in theory get out further as a narrow band mode advantage. Some hams have noticed that their radios specifications it takes a stronger signal to decode.

The Icom repeaters have poor receive sensitivity and poor adjacent channel
rejection compared to Motorola/Kenwood repeaters. The spec's on the RP-2000V are
12dB sinad at .45uv and only 65db isolation from adjacent channels.

The D-Star user radios spec. worse sensitivity in DV mode than FM.... However in theory with proper implementation:

The DV Advantage Per Mark, N5RFX:

The DV signal has a steady noise level to –119 dBm and drops off at –120 dBm. The analog FM signal SINAD begins to drop at –102 dBm. Between –102 and –119 dBm DV has a SINAD advantage over analog FM. The advantage occurs over a 17 to 18 dB range. When noise free signals are desirable, DStar digital voice can meet this requirement with a 17dB to 18dB increase in the range that noise free operation can occur. For weak signal work, the analog FM signal will prevail.


Trading 2 dB of sensitivity for a 17dB increase in nearly noise free reception is an advantage of DStar over analog FM. When weak signal reception is necessary, the analog signal will provide better performance.

D-STAR isn't perfect, but it's here and it's being used, so we should familiarize ourselves with it. Besides, it's fun to play with a new mode. :)

One method to combat multipath it is found in the IC-2820H mobile, with its diversity receive. Another possible combatant might be to put circular polarization at the repeater site.


There is an article on circular polarization antennas in August 2007 QST. It might be interesting to do some research in this area. Bases could use horizontally polarized antennas to cut down interference from man made sources and be 20 db down from adjacent vertically polarized FM repeaters and mobiles. Using slot antenna designs horizontal might also be practical on 23-cm mobiles. (John, K7VE mentioned this back in 2007.)

I still haven't found any reports of any D-Star repeaters trying circular polarization at the repeater site. But I would be curious to read about it.