April 2014 Inbox
Wednesday, April 09, 2014 | Comments

Following are comments we’ve received from readers about recent online and print news and articles. If you’d like to comment on an article, email edit@RRMediaGroup.com.

In response to “How Time Delay Interference Affects P25 Coverage,” from the April issue of MissionCritical Communications


This is one of the best articles that I've ever seen on the subject. For years, we (a federal government agency with lots of aircraft) have operated in our conventional Project 25 (P25) system, where there are multicast clusters of repeaters that include several towers within each cluster that are simulcast (tower transmit frequency reutilized). When first seeing this effect, we termed it "digital blanking" and learned that the only way to mitigate it was to go to a lower altitude, an action which is counter to all beliefs that higher was always better to establish communications.

Now when operating in those areas, we specifically don’t program any tower that is simulcast within that given cluster. This keeps unknowing pilots and operators from accidentally selecting one of the problematic towers.

Also, we have learned that even operating on the direct side of a P25 conventional digital repeater can cause issues when the repeater lights up during the time that we are trying to talk simplex to a user on the ground. With network registration, including over the air reprogramming (OTAR), and position tracking happening all the time, the repeater is very active, and the result has been to go to dedicated simplex channels and avoid the direct/talkaround capability altogether.

To make the aircraft work in a P25 trunked environment such as the Integrated Wireless Network (IWN) system in the Pacific Northwest, we had to specifically limit those radios to only register with control channels that were unique in the system. This was the only way to avoid the problem where the aircraft receiver was listening to two (or more) control channels on the same frequency at the same time. Works well now!

Thanks again for a great article! Good to know up front that the issue only becomes more acute in a Phase 2 system.

Dennis Del Grosso
Organizational Strategies
Supporting U.S. Customs & Border Protection
Office of Air and Marine
Tactical Communications SME



In response to “The SMR Revival” from the March issue of MissionCritical Communications


Your article, “The SMR Revival,” was a good read this morning. I was quite interested in your comments on Page 30 middle column concerning states beginning to enforce the federal mandate in January 2015 or they lose their funding. This means there probably is some planning going on that has to be submitted to the feds as proof.

Just a few comments about what is going on in Texas. Most SMR analog or digital operators in Texas operate standalone networks, however, there is a movement taking place to begin cooperating more between SMR operators in our state, especially those of us that have NEXEDGE or have plans to upgrade to the same technology. Our SMR is currently analog serving approximately 40 counties in east Texas, the I-45 corridor between Dallas Forth Worth (DFW) and Houston, DFW to Shreveport, La., and to our west to Bryan/College Station. We are working with a small group of operators in an effort to determine how we might combine or link our systems for a larger SMR footprint in the state.

Thanks again for promoting our industry. SMR is not dead … it’s just changing!

Bill Parker
Sales Manager
Nalcom Wireless Communications
Palestine, Texas



In response to “NPSTC Releases Position Paper on Non-P25 Digital Technology” from April 17


As the news outlet reporting this information can you provide the actual link to the position paper?

This article states that "NPSTC strongly urges public-safety and critical infrastructure agencies contemplating the purchase or use of LMR equipment to opt for P25 Phase 1 (12.5 kilohertz conventional FDMA) and/or analog modes for interoperability.”

Yet the following article, “Maryland Governor Signs Bill with Joint Governance for Statewide P25 System” indicates that the new network is a Project 25 (P25) Phase 2 network from Motorola.

So would NPSTC come out publicly against the Maryland network because it is not interoperable? P25 Phase 2 doesn’t provide analog functionality and is two-slot TDMA, which is used as an argument against selecting anything but P25.

Do your reporters ask these questions?

David Torres


Editor’s Note: The link to the paper is:


The paper includes the following footnote: “This does not preclude system infrastructure which is Phase 2 compatible.”



In response to “Maryland Governor Signs Bill with Joint Governance for Statewide P25 System from April 17


This is very useful information. I am looking for more information from states that are doing the same thing regarding radio service governance. Please forward if you have any information that I may have missed.

Ben Gherezgiher
Director of Information Technology
Public Safety Business Segment
Office of Management and Enterprise Services – ISD
Oklahoma City


In response to “Crosby Makes List of Top 100 Wireless Technology Experts” from April 14


You could not be more correct about Mark Crosby being one of the top 100 wireless technology experts. He is a true professional in the wireless world and an advocate for responsible spectrum sharing and technology.

Ann Rita Ditmore
General Manager
Central Communications and Electronics



In response to “P25 Radio Programming Spreadsheet Approved, Set to be Released to Public” from April 1


It would be very helpful if the spreadsheet only allowed Project 25 (P25) encryption and no proprietary features of any kind.  

Phil Bartmann



In response to “2 Los Angeles TV Stations Conduct Channel-Sharing Pilot” from March 28


I look forward to joining the first class action suit against the broadcast industry and the FCC for duping the American public into the mass change over to high-definition TV (HDTV) and then diluting the promise of HD down to standard definition (SD).

The last I looked, the airwaves belong to the people and now there's a move to channel share, which will result in lots of SD (aka low resolution) signals being broadcast, which will look terrible on our new digital flat screens. The American citizen gets screwed again!

David Kling



Click here for the February 2014 Inbox.
Click here for the January 2014 Inbox.
Click here for the November 2013 Inbox.



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