17 December 2017

Antenna Work

Yesterday my local Amateur radio club, KK4GQ, did some extensive repair and replacement work on our antennas on our flagship tower in Fayetteville, Georgia. The club or its members own an extensive network of 2 meter and 70 centimeter-band Amateur radio repeaters around the south metro Atlanta area, and we support a wide variety of public events and emergency response activities with this network, including supporting the National Weather Service office in Peachtree City, GA. So it's important to keep this radio infrastructure as healthy as possible.

About 10 years ago we got permission to put several repeaters on a public service tower in Fayetteville. We even got permission to take our antennas all the way to the top of the tower, to the 300 foot level. While this affords outstanding signal coverage, being the top guy on the totem pole also means you are the prime target for whatever Mother Nature throws at the tower. Over the years our antennas developed problems related to wind, rain and (we suspect) lightning damage. After almost a decade we decided it was time to put some money and effort into rehabbing the antennas and replacing what couldn't be fixed.

So we found a climbing crew that gave us a price break, bought a new Andrew DB420 antenna for the 70 cm repeater, gathered at the base of the tower, and got to work.

Five hours later we had the new antenna in place and the climbing crew performed maintenance on the still serviceable antennas on the tower. They straightened up the tower stand-off brackets, re-secured the mounts for many of the antennas, checked cable connections and wiring harness condition and generally got things back in good operating order.

Our primary 2 meter and 70 cm antennas are back up at the 300' level and we're getting great signal reports from around the metro Atlanta area. Hopefully we're good for another decade!

Tower crew at the 300' level taking down
the damaged 70 cm antenna

Andrew DB420 antenna being prepped

DB420 close-up

DB420 being hoisted to the 300' level

At the very top (300'), 70 cm (444.600 mHz) antenna on
the left, 2 meter (145.210 mHz) on the right.
Perfect targets for Mother Nature, but we made
sure everything was well bonded 

Tower crew working to straighten & tighten down the
stand-offs and re-tighten some of the antenna mounts.
The two antennas on this stand-off are part of the remote base
 system that supports the National Weather Service

W8BYH out

16 December 2017

Amateur Radio Repeaters in Georgia

When I'm not playing radio I'm making maps for a living (yes Virginia, you can make a living making maps). Most of the maps are very esoteric and tightly tied to the needs of people who do things like inventory utilities or inspect retail operations. But every so often I get to indulge myself and put together a map that is fun to work on, presents a challenge and provides what I hope is real value to folks who share my interests.

Earlier this year, as the spring storm season approached, I put together a web map that depicted all the Amateur Radio repeaters in the State of Georgia. The map is built using a system called ArcGIS Online, a service provided by ESRI, and is hosted in ESRI's cloud environment.

Compiling this map presented some interesting challenges, the biggest being the collection and aggregation of location information for the repeaters. At first I thought it would be an easy task to just go to the FCC's radio license database (ULS), do a search on Amateur service repeaters in Georgia, download the data, geocode it and publish it. Simple, straightforward, easy. Hah! Silly me. The FCC either doesn't have, or doesn't make public, Amateur radio repeater information.

To throw together the repeater information I went out to multiple on-line sources that held the bits and pieces I was looking for - regular repeater data from this source, digital repeater data from that source, and some 'insider knowledge' of the actual locations of repeaters near me. It was an inexact, tedious and error prone process, but I wanted to get it done so I had something to use and share with the local Amateur radio community. The map was completed and published, but I knew there were a lot of problems with the repeater data.

Amateur Radio Repeaters in Georgia

Fast forward to a few weeks ago and I figured it was time to try to update the repeater listings in the  map and present complete and authoritative information on each repeater. With accurate repeater locations you can do lots of interesting things like line-of-sight analysis, terrain masking studies, RF coverage polygons, and more. This has the potential to help visualize the repeater infrastructure in Georgia in entirely new ways.

After some emails and phone calls I found out that the actual repeater locations (and all other information about the repeaters) are held by the  Southeastern Repeater Association (SERA). SERA is the recognized repeater coordination group for the southeastern US. The term 'coordination' refers to the process of having a regional coordinating organization like SERA assign a frequency pair (input/output) and PL tone to your repeater. If a repeater is coordinated then it assures that the repeater will not cause interference with other repeaters in the region (and vice-versa) and that the FCC will resolve any interference issues between a coordinated and uncoordinated repeater in favor of the coordinated repeater. Repeater coordination in places like the Atlanta metro area is absolutely essential to keep the repeaters from stepping all over each other. In fact, I've been told that there are so many Amateur radio repeaters in the Atlanta area that there are no more 2 meter frequency pairs available above a line that runs from Columbus to Macon. That's a LOT of repeaters! If you live in the Atlanta area or are visiting you can be assured of finding at least one (and usually several) repeaters that you can hit with just a handheld radio. The fact that these repeaters are not stepping all over each other and causing interference is due to the hard efforts of SERA.

SERA considers the locations of its coordinated repeaters to be proprietary information. Part of the issue is security - a lot of repeater owners are uncomfortable with the idea of their repeater/tower locations being made public. The other issue is that SERA makes a small profit by selling repeater guides and journals that contain this proprietary information. Since SERA is a non-profit organization they see this as a way to help cover their operating costs. I can understand and respect that.

So this has me facing my original challenge - how to collect accurate repeater data? I still have the old method to fall back on - scrape the data out of a number of different sites on the web that hold the data and do not put any restrictions on its use. However, I'd also like to take this opportunity to invite individual repeater owners/trustees to review their repeater data in this web map and provide me any necessary updates or corrections. I'll respect your wishes and show only the data you want displayed.

If you are a repeater owner or trustee and would like to help keep this data up-to-date please contact me at w8byh@arrl.net.



12 December 2017

Early History of the PRC-25 and -77

Very few things in this world are a wholly original idea. So it is with the AN/PRC-77. The PRC-77 is actually a product improved AN/PRC-25, a radio that was revolutionary it its design.

The PRC-25 was introduced in the early 1960's and was the right radio at the right time. In 1965 General Creighton Abrams called the PRC-25 "The most important tactical item in Vietnam today". More important than the M-16 rifle, more important than the UH-1 'Huey' helicopter. In fact, it was the light weight, rugged design, ease of use and wide fielding of the PRC-25 that allowed the US Army to successfully implement the new tactic of vertical envelopment by helicopter. Vertical envelopment requires close communication between ground and aviation elements, and the PRC-25 filled this role perfectly.

The early history of both the PRC-25 and PRC-77 is not well known. The PRC-25 and -77 series radios were the most widely produced military communications systems ever fielded (estimates are that over a half million units were eventually produced in the US alone) and the PRC-77 is still in use with militaries around the world. They are also immensely popular with collectors. But the history of these radios, particularly the developmental history, is a bit foggy.

Back in 1999, Mr. Dennis Starks, a military radio collector and former editor of the Military Collector Group Post, put together an article that was, and remains, the the most comprehensive history of the PRC-25 & -77 series radios. The article, titled 'PRC-25, Forgotten Legend', was published on-line and is still referenced as a link from a number of collector and military history websites. Sadly, the hosting site Mr. Starks used was closed down several years ago and since then his article existed only as partial extracts on various discussion forums.

In December 2017 I was able to contact Mr. Starks and obtain an original copy of his article. With his permission I edited the article and re-created it as a PDF document. The article is a great read, with lots of important information on the early design and fielding of the PRC-25 and -77 radios. It is an important historical and collector's resource and it deserves a wider audience. Towards that end I have added a link to 'PRC-25, Forgotten Legend' (as a PDF) in the 'Links' section of this blog.

PRC-25, Forgotten Legend by Dennis Starks


W8BYH out

10 December 2017


In case you hadn't heard, the Atlanta area got a rare treat this weekend - snow! The VX-6 begged to go out and play.

It had a tough time making snow angels, though.

These radios are tough little buggers!

W8BYH out

08 December 2017

Amateur Radio and GPS - We Need A Better Mash-Up

Radio is my hobby. My daytime job has me working with GPS-based high precision navigation and positioning systems at a very busy commercial airport. It is fascinating work and it often exposes me to leading edge of GPS-based developments. GPS and the entire global navigation satellite system (GNSS*) infrastructure has fundamentally changed the way we think about location and navigation, and is directly responsible for saving hundreds of lives. Not just since the systems were introduced, but every single year.

GPS receiver technology gets smaller, cheaper, more accurate and more robust every year. GPS technology is becoming ubiquitous and is already embedded in a huge variety of systems, many the consumer isn't even aware of. I often joke that in the not-too-distant future we'll have GPS-enabled toasters, and I'm only half joking. GPS receivers are everywhere - in your smartphones and tablets, in your car, in airplanes and ships, on the periscopes of submarines, in emergency responder trackers, on the collars of grizzly bears, in self-driving cars, on cellphone towers, on the ankles of criminals released on parole and on the backs of individual Soldiers so they can be tracked on the battlefield.

More and more, GPS receivers are making their way into Amateur radio handheld transceivers, but the integration is only half baked. GPS receivers are making their way into these radios merely as an adjunct to digital modes of operation. Radios like the Icom ID-51Plus, the Kenwood TH-D72 & 74 and the Yaesu FT2DR all have built-in GPS receivers to support either D-STAR, APRS or System Fusion. These modes leverage GPS to provide position information as part of the digital signal. And little else. Of course you can access the GPS status screen as part of the overall radio feature set, and most radios have rudimentary waypoint logging and navigation, but it is all little advanced beyond what a basic Garmin or Magellan unit offered 20 years ago.

Continuing with this 'stuck in the 90's' theme, the transceivers I've used (the ID-51 and both of the Kenwoods) have very limited offerings for both map datums and coordinate systems. For datums many offer just two options - the Tokyo Datum and WGS84. The Tokyo datum offering reflects the country of origin. WGS84 is a world-wide datum, and the 'native' datum of the GPS system. WGS84 is a pretty good datum and works equally well (or equally poorly, depending on your perspective) just about anywhere across the globe. But the lack of coordinate system options is what really stops these transceivers from serving as general purpose GPS units. A coordinate system is built on top of the datum and is what provides the x, y positional values (lat/long, easting/northing, etc.).

Many Amateur radio operators get into the hobby because the emergency response aspect captures their interest. They offer their communications training, expertise and equipment free of charge when disaster strikes. Many are put out on remote sites or made part of mobile response teams and asked to provide regular updates that include a location component.

Other radio Amateurs simply enjoy the outdoors and see Amateur radio as an ideal adjunct to their hiking and backpacking activities. Again, there is a location component to this activity and most outdoors men and women carry a GPS receiver as part of their back country kit.

In both of these instances the GPS-enabled handheld transceiver could fill the bill as a general purpose GPS unit, but the GPS interfaces in these radios work against the user. In each of these radios the only two coordinate systems provided are latitude/longitude and the Maidenhead grid. Great for Amateur radio, but lousy for general location identification. First, nobody but Amateur radio operators use the Maidenhead grid. It's great for identifying your location to other hams, but that's about all. Second, passing latitude and longitude coordinates by voice communications is difficult and easy to mess up. There are multiple latitude and longitude formats - degrees/minutes/seconds, degrees/decimal minutes, decimal degrees - and various callouts for longitude (+/- or east/west) and latitude (+/- or north/south). It is very easy to get confused and mis-call a number.

Three modern (and high end) Amateur radio HTs. From left to right, the Icom ID-51Plus, the Kenwood TH-D72
and the Kenwood TH-D74. All three are extremely capable radios  with built-in GPS. All three make lousy general
purpose GPS receivers. Note the difference in the lat/long coordinate system readouts between the the ID-51
and the TH-D74 and the TH-D72. Which one is right? Which one is wrong? Here's the issue - all are right
The ID-51 and the TH-D74 are presenting the lat/long in degrees/decimal minutes. The TH-D72 in the middle
is presenting the coordinate values in degrees, minutes, seconds

The US Army and NATO recognized this problem in the late 1940's and came up with the world-wide Military Grid Reference System (MGRS). It simplifies location identification by providing a unique set of grid zone identifiers and coordinates for every location on earth, down to a single square meter. MGRS has been continuously updated and is now based on the WGS84 datum to improve world-wide accuracy. Over 20 years ago GPS receiver manufacturers figured out how to program MGRS capability into their products, and virtually every receiver made since 2000 has included MGRS as a coordinate system option.

In 1999 I bought a Magellan GPS 315. This 18+ year-old GPS receiver
had a better feature set than you find in current production Amateur
radio handhelds with built-in GPS, including the ability to display locations
using MGRS (USNG). Integrating many of the Magellan's basic functions into
an Amateur radio transceiver, with its improved GPS receiver technology and
better processors, should be an easy task

I understand the political sensitivity of putting a coordinate system titled 'military grid reference system' in a civilian ham radio, particularly one that is marketed around the world. But the US is the single biggest market for Amateur radios and the manufacturers already build market-specific units that match the local or regional band plans. It should be an easy decision for the manufacturers to include a US-specific coordinate system readout for units sold in North America.

But we can make it even easier for them to decide. In the United States our emergency response, search and rescue and other public services have adopted a variation of MGRS called the US National Grid. The US National Grid (USNG) is simply a version of the MGRS system that is based on the North American Datum of 1983. Its use has been mandated across local, state and federal response agencies. For at least the last five years all standard topo maps produced by the US Geological Survey have a USNG overprint. Most GPS receivers marketed in the US have USNG as a coordinate system option, and a wide variety of smartphone navigation apps provide USNG readouts. The code for translating latitude/longitude into USNG is open source and there are plenty of developers in the market with deep experience integrating USNG readouts into various applications. It should be a 'no-brainer' for Icom, Yaesu and Kenwood to bring on some programming expertise, clean up their GPS functionality and provide a better general GPS interface option.

An example of a USNG readout provided by a simple
smartphone app (USNGApp by SharedGeo).
There is no reason Amateur radio manufacturers can't
incorporate USNG as an available coordinate system
option. It greatly reduces confusion when passing
location information via voice, and first
responders are trained in its use

What should this improved GPS interface provide? Let's start with simple one touch (or button push) access to a GPS window that provides:
  • A large, clear and easy to read main display showing current location in a user selectable format (USNG, lat/long, UTM, Maidenhead, etc.)
  • A sub-display showing location in a second user selectable format
  • The current frequency or repeater ID the transciever is tuned to
From this top page, quick navigation to sub-pages showing waypoint listings, distance and direction to selected waypoints, an easy to use waypoint management screen, and a GPS/GNSS satellite status screen. This is dead easy to achieve with the GPS receivers and CPUs in current radios. The biggest restriction today is screen size and resolution. 

When keying to transmit from the top GPS menu page the primary location ID (USNG, lat/long, etc.) remains in the display so the operator can quickly and easily read off his/her location information to the other station.

Yes, I know that D-STAR, System Fusion and APRS can pass location information, it's a core part of their functionality. The problem is, each of these systems has heavy infrastructure dependencies unless you are working digital simplex. D-Star and System Fusion require you to be hitting a system compatible repeater, and APRS requires you to be able to hit a digipeater. What about simplex? It's doable - all these modes support some level of digital simplex operations. However, few hams practice working voice simplex over VHF & UHF frequencies. Expecting them to be able to configure their radio for digital simplex under stressful circumstances is too much of a stretch.

My argument calls for a GPS interfaces to be embedded in digital and non-digital radios. In this day and age why should GPS technology be restricted to just digital mode applications? It's time to marry up analog Amateur radio with GPS. The use case is well established and the technology is mature and easy to implement. It just makes sense.

So come on Icom, Kenwood and Yaesu - give us a robust, waterproof and shock-proof dual receive analog handheld with a properly integrated GPS capability. When you do I'll be standing at HRO with cash in-hand, and I'm pretty sure I won't be the only one.

W8BYH out

(*Definition time - the term Global Positioning System or GPS refers to the American system of navigation satellites and supporting infrastructure. The accepted term for all satellite navigation systems - GPS, the Russian GLONASS system, the EU's Galileo system, the Chinese Beidou system and others are collectively referred to as the Global Navigation Satellite System, or GNSS)

05 December 2017

The Spectrum Monitor

I got notification a few days ago that the December issue of the on-line magazine The Spectrum Monitor was ready to download. The email also included a reminder that subscriptions run January to December, and it was time to renew.

So without hesitation I went out and renewed. It was a no-brainer; The Spectrum Monitor is the best general interest radio publication available today. The Spectrum Monitor, as an on-line publication, grew out of the old Monitoring Times magazine. Monitoring Times was founded in the early 1980's by Bob Grove. Bob retired in 2014 and ceased publishing Monitoring Times after 33 years. A few of his former staff and writers decided to create a similar publication in digital format, and the first issue of The Spectrum Monitor was published in 2015.

Monitoring Times was a niche publication that appealed to folks with an interest in scanning and monitoring the airwaves for any interesting activity. It wasn't just about shortwave listening - Monitoring Times had contributors that specialized in tracking military communications, public service communications, air traffic communications, you name it. Bob would also toss in some ham radio topics and product evaluations to keep things interesting, but the magazine was mainly focused on what is happening on the airwaves, from 'daylight to DC' as they used to say.

Because Monitoring Times offered a rich overview of what was happening on different parts of the radio spectrum it was one of the few general interest publications that developed a strong military following. In the 1980's and 90's you could walk into any US Army communications or intelligence office and find well worn copies of Monitoring Times laying around.

When Ken Reitz, the old Monitoring Times managing editor, decided to try to take the publication to the web as The Spectrum Monitor he managed to bring along a number of Monitoring Times' experienced staff and copy the tried and true format of the old magazine. It works! Ken has managed to keep the quality of the content high and the editing is first rate. The Spectrum Monitor is a worthy successor to Monitoring Times, and I really hope it succeeds in the market. You can subscribe or purchase individual copies at The Spectrum Monitor website.

I mark this as Highly Recommended!

W8BYH out

02 December 2017

Testing the Yaesu VX-6R

Over the past few months I've become a huge fan of the Yaesu VX-6R handheld transceiver (HT). It is one of Yaesu's line of tough little handhelds designed for outdoor use. Yaesu's VX line has had a long run, and they are very popular. Sadly, the VX-6R seems to be the last survivor of that line - Yaesu recently killed off its sole surviving sibling, the VX-8DR. This has me wondering just what Yaesu intends to do with the line.

The VX-6R isn't a very sophisticated radio by today's standards, but the chunky little handheld (it's smaller than a pack of cigarettes, if anyone remembers how big those are) offers a lot of technology stuffed into a small package. It offers a tri-band transceiver (2 meters, 1.25 meters and 70 centimeters), wide band receive including FM, air band and shortwave (!), a full backlit keypad and a fairly large display for such a small radio. That's about where the bells and whistles stop - no digital modes, no GPS, no color display. It's an honest radio, one that would meet the needs of about 90% of American hams.

But the real reason I like the VX-6R is that it's a tough little bugger. In its advertising Yaesu seems to be targeting this radio at the outdoors crowd, with glossy shots of the radio being used by someone obviously too close to water to be holding an electronic device. In Yaesu's parlance the radio is 'submersible'. Heck, it's even printed on the face of the radio.

Not one to shy away from a challenge, I decided to put Yaesu's claim to the test. Back in October, Tropical Storm Nate paid a visit to the Atlanta area and dumped a few inches of rain on us. OK, more than a few. I figured this was the perfect test environment for the little radio.

After a few hours of sitting on the tailgate of my truck it was time to test. 

I have to admit I was half expecting the little radio to fail!

Since this test I acquired a second (used) VX-6R as a back-up and put it through the same test during a heavy rainstorm. This radio also passed the water resistance test with flying colors. It appears Yaesu's advertising isn't hype - these little buggers really can stand up to being dunked or left out in the rain.

The VX-6R has become my 'take everywhere' HT - on dog walks, on fishing trips, to the shooting range. Although I don't abuse my communications gear it's good to know this is a radio I don't have to baby. It can easily survive a tumble from the tailgate of my truck or shrug off being left out in a drizzle. It is convenient to carry and easy to operate. When paired up with a decent tri-band antenna like the Diamond SRH320A it makes a tough, capable little communications package.  

If you've been thinking about getting a VX-6R I recommend you pick one up soon. Yaesu may well kill it off in the upcoming year to make more market space for something more modern but less capable than this little winner.

Highly recommended.

W8BYH out