DMR Hotspot from SharkRF

Amateur adoption of Digital Mobile Radio (DMR) continues to increase, with a number of new innovations playing out. It was way back in 2012 when I wrote this article about DMR for CQ VHF Magazine: TRBO Hits the Amateur Bands. 

A few years ago, I picked up some used MOTOTRBO gear to use on our local DMR repeater system (MOTOTRBO is Motorola’s version of DMR). Here in Colorado, the Rocky Mountain Ham Radio group has been instrumental in establishing a great network of DMR repeaters, a real asset for Colorado radio amateurs. See Rocky Mountain Ham Radio TRBO/DMR Network.  Worldwide, the DMR-MARC organization has created a robust network of MOTOTRBO repeaters in over 60 countries.

A more recent development is the establishment of the BrandMeister Network, which promotes more of a homebrew approach to DMR. This evening, the BrandMeister dashboard shows 634 industrial repeaters (commercial equipment), 263 homebrew repeaters and over 1300 hotspots of various types.  A variety of DMR hotspots are available, including the DV4mini. I’m not going try to list all of the hotspots available as I’m sure I’ll miss something.  The SharkRF openSPOT caught my attention because of this excellent review by John ‘Miklor’ K3NXU. Because of its popularity, the openSPOT is on backorder (price: 182.5 Euro).

This HamRadioConcepts video walks through the setup and basic operation.

I thought the openSPOT would be a good widget to have around the shack. It is a standalone hotspot, so I don’t have to dedicate a computer to it. Also, it is very turnkey…no assembly required…but some configuration to work out. Its user interface is a web page that you access via your local network…nicely done. I got it working in less than one hour and have been fiddling around with it ever since.

Hotspots are a funny item. They have very limited RF range, so their main purpose is to provide local RF access into the network (just like your Wi-Fi hotspot). One role they play is to provide fill-in coverage when no repeater is available. Another role they fill is being a personal device that can be connected to your favorite reflector or talk group.

I should point out that the openSPOT also operates as a D-STAR and Yaesu Fusion (YSF) hotspot. You just change the configuration of the modem and it starts speaking the selected modulation. More surprising is that I was able to use a YSF handheld radio to talk to the openSPOT which routed me to a DMR talkgroup. Yes, a Yaesu YSF radio talking on DMR.

The first thing I noticed when listening to some of the more active talk groups is that it seems like every person getting on the system said “I just got this Tytera MD-380 radio and you are my first DMR contact.” OK, sometimes it was a Connect Systems or Motorola radio but the MD-380 at around $100 is having a big impact. I picked up an MD-380 and while its not quite as nice as my Motorola, I really do like the radio. (Note that there are other low cost DMR radios that have serious technical issues.) There will be other radios on the market…the technology will keep improving and improved models will hit the market. Right now, everyone is wondering who will create a good dualband 2m / 70cm transceiver for DMR.

I see some very strong technology and market trends in play here that are going to impact the ham radio world. First off, DMR is a true industry standard (ETSI),  well designed and documented. Second, we are seeing multiple radio vendors offering competitive, low cost transceivers. Third, there is high quality commercial repeater gear available from land mobile providers such as Motorola and Hytera. But there’s one more thing that really tops this off: the number of ham-built products emerging that are focused on DMR. This is classic ham radio adaptation and innovation that leverages commercial gear for ham radio use.

Stay tuned…this is going to be interesting!

73, Bob K0NR

The Cacophony of Digital Voice Continues (Part 2)

Digital transmissionThis post is a continuation of The Cacophony of Digital Voice Continues (Part 1), so you probably should read that one first.

All of the popular amateur digital voice (DV) systems (D-STAR, DMR and YSF) use the AMBE vocoder (voice codec) technology. This technology was developed by Digital Voice Systems, Inc. and is proprietary technology covered by various patents. The use of proprietary technology on the ham bands causes some folks to get worked up about it, especially proponents of an open source world. See my blog posting: Digital Voice at Pacificon and this presentation by Bruce Parens K6BP: AMBE Exposed. Codec2 is an alternative open voice codec developed by David Rowe, VK5DGR. David is doing some excellent work in this space, which has already produced an open codec that is being used on the ham bands. FreeDV is an umbrella term for this open codec work. Here’s a recent video of a presentation on FreeDV by VK5DGR.

It will be interesting to see if and how Codec2 gets adopted in a DV world already dominated by AMBE. After all, a new codec is another contributor to the digital cacophony. On the HF bands, it is easier to adopt a new mode if it can be implemented via a soundcard interface (which FreeDV can do). Any two hams can load up the right software and start having a QSO. The same is true for weak-signal VHF/UHF via simplex. (Note that Flexradio also supports FreeDV, showing how Software Defined Radio (SDR) has an advantage with adopting new technology.)  VHF/UHF repeaters are trickier because you must have a solution for both the infrastructure (repeaters and networks) as well as the user radios.

The vast majority of digital repeaters support just one digital format. For example, a D-STAR repeater does not usually repeat DMR or YSF transmissions. Interestingly, DMR and YSF repeaters often support analog FM via mixed mode operation for backward compatibility. It is definitely possible to support multiple digital formats in one repeater, but the question is will large numbers of repeater owners/operators choose to do that? With existing DV systems, the networking of repeaters is unique to each format which represents another barrier to interchangeability. In particular, most of the DMR infrastructure in the US is MOTOTRBO, which won’t ever support D-STAR or YSF.

In the case of a new vocoder, we can think of that as just a new format of bits being transported by the existing DV protocol. DMR, for example, does not actually specify a particular vocoder, it’s just that the manufacturers developing DMR equipment have chosen to use AMBE technology. So from a technical viewpoint, it is easy to imagine dropping in a new vocoder into the user radio and having it work with other identical radios. Of course, these radios would be incompatible with the existing installed base. Or would they? Perhaps we’d have a backwards compatibility mode that supports communication with the older radios. This is another example of putting more flexibility into the user radio to compensate for DV incompatibilities.

One objection to AMBE is the cost of the technology, especially when compared to free. When D-STAR radios first started using AMBE codec chips, the chip cost was rumored to be $25 to $50, but I don’t have a solid source on that. Now, I see that Tytera is selling a DMR handheld at around $100, including AMBE technology inside, so the codec can’t be very expensive. If a free codec starts to be a credible threat, it will put additional pricing pressure on the AMBE solution.

A potential advantage of Codec2 is superior performance at very low signal-to-noise ratio. We’ve all experienced the not-too-graceful breakup of existing DV transmissions when signals get weak. Some of the Codec2 implementations have shown significant improvement over AMBE at low signal levels.

Conclusions

Repeating a key conclusion from Part 1:

  • For the foreseeable future, we will have D-STAR, DMR and YSF technologies being used in amateur radio. I don’t see one of them dominating or any of them disappearing any time soon.

Adding in these conclusions for Part 2:

  • Codec2 will struggle to displace the proprietary AMBE vocoder, which is well-established and works. The open source folks will promote codec2 but it will take more than that to get it into widespread use. Perhaps superior performance at low signal levels will make the difference.
  • Repeater owner/operators will continue to deploy single-DV-format repeaters. This will make multiformat radios such as the DV4mobile be very attractive. In other words, we will deal with the digital cacophony by having more flexible user radios. This will come at a higher price initially but should drop over time.

Repeating this one from Part 1:

  • A wild card here is DMR. It benefits from being a commercial land mobile standard, so high quality infrastructure equipment is available (both new and used gear). And DMR is being embraced by both land mobile providers (i.e., Motorola, Hytera) and suppliers of low cost radios (i.e., Tytera, Connect Systems). This combination may prove to be very powerful.

Well, those are my thoughts on the topic. I wish the DV world was less fragmented but I don’t see that changing any time soon. What do you think is going to happen?

73, Bob KØNR

Rehab for the KØNR Repeater

My UHF repeater has been operating on 447.725 MHz here in Monument for a couple of decades now. It started out as a classic “pet repeater” project and has been operating from my basement all this time. Over time it has picked up additional users and has turned into the de facto hangout for our local radio club.

The repeater system has gone through a number of revisions over the years, including the RF transmitter and receiver. I wanted to retire the pair of Motorola Mitrek mobile radios I have been using when they started to exhibit a few lose connections. Really though, I thought it was time for some synthesized, modern RF gear in a compact package.

k0nr-repeater3When Yaesu offered an attractive price on their DR-1X Fusion repeater, I jumped at the chance. Initially, I put it on the air in mixed analog-digital mode with the repeater automatically switching modes to handle either analog FM or C4FM digital. I used the internal controller of the DR-1X which is quite simple and has limited functionality. (The SCOM 7K controller got put on the shelf for a while.) The DR-1X supports using an external controller but implementing the mixed analog-digital mode is…well…challenging. (Various people have figured out ways to do it with modifications to the DR-1X or using additional hardware.)  After 10 months of operation, I decided to reinstall the full-featured SCOM 7K controller, enabling quite a few features including a 2m remote base, synthesized speech, automatic scheduling and weather alerts. This does mean giving up the C4FM mode but usage was minimal anyway.

The SCOM 7K repeater controller has been in service for decades, handling multiple receivers and transmitters, very configurable with programmable macros. SCOM has long since moved on to a newer, improved model but my 7K just keeps on ticking. The 7K has the voice synthesis and autopatch options installed, so, yes the repeater has an autopatch (not that anyone cares). A Yaesu FT-7800R is used as a 2m remote base and the duplexer is a classic Decibel Products. Not shown in the photo is a Bearcat WX100 weather receiver that is used to transmit weather information when an alert occurs in our area.

I’ve documented the wiring diagram and configuration used here: k0nr-repeater-construction-notes

This was a good opportunity to clean up some of the cabling and physical mounting that had degraded over time. (A kluge here, a kluge there and entropy takes over.) I am happy with the result.

73, Bob K0NR

Digital Voice Balkanization

Digital transmissionWouldn’t it be cool if we had one digital communications format for the VHF/UHF amateur bands with all equipment manufacturers offering compatible products? The basic modulation and transport protocol would be standard with manufacturers and experimenters  able to innovate on top of that basic capability. There would be plenty of room to compete based on special features but all radios would interoperate at a basic level. You know, kind of like analog FM.

Yeah, we don’t have that. 🙁

73, Bob K0NR

Graphic: Adapted from HamRadioSchool.com

Hey, My Yaesu Beeps When I Transmit!

FT-8800R_thumbI own a variety of Yaesu ham radio transceivers and like them a lot. Except for that one little annoying feature that the FM rigs have: WIRES.

About once every two weeks, one of the local radio hams gets on the repeater with a DTMF beep at the start of every transmission. We’ve come to expect it now, so the first question to the ham is “are you by chance using a Yaesu radio?” They always say “yes” and then we talk them through the process of turning off the WIRES “feature.”

The WIRES function sends a DTMF signal at the start of every transmission for use with Yaesu’s version of internet repeater linking (which is not used much in the US).  The problem is that it is very easy to bump the wrong button on your radio and accidently get it into this mode. This means that this is mostly a nuisance feature in the US.

I recently came across a way to disable this feature on your Yaesu radio so that it won’t sent the DTMF tone even if you activate it by accident. Basically, you set the WIRES tone to be empty, so nothing is transmitted if you accidentally turn on WIRES. I did not come up with this clever hack…in fact, I am not sure who put this together. (If you do, let me know and I’ll give them credit.) Take a look at this pdf file and follow the instructions to de-WIRES your radio: Turn Off Wires

73, Bob K0NR

 

This Spewed Out of the Internet #25

0511-0701-3118-0930Here’s another update of interesting important stuff spewing forth from the internet.

I put my two presentations from HamCon Colorado out on the web:  Practical Amateur Radio Measurements and Mountaintop VHF in the Colorado High Country . Also, check out Kelly N0VD’s blog posting on the event.

Having trouble finding a repeater to use on VHF? Check out my Shack Talk article on HamRadioSchool.com

KB5WIA provides some good tips on EME operating.

Hans PD0AC addresses the question: What’s the Best Chinese Dual-band HT? For best price/performance, he selected Baofeng UV-B5/UV-B6 (and I agree).

The Noise Blankers continue to publish their Ham Hijinks. Remember: Do Not Take These Guys Seriously. Seriously. Do not do this. Seriously.

There’s lots of great ham radio events coming up this summer. This weekend is the CQ Worldwide VHF Contest, the only “true VHF contest” out there since only the 50 MHz and 144 MHz bands are used. Then there’s the Colorado 14er Event, which includes Summits On The Air (SOTA) activations, on August 4th. (Don’t forget to check out the great new Colorado 14er Shirts!)  The Colorado QSO Party is another great operating event, on August 31st.

Remember: There is no such thing as ground.

Think about it: an infinitely large electrical node with zero impedance able to sink an infinite current. Not likely.

73, Bob K0NR

FCC Grants Waiver on TDMA

fcc-1From the That Took A Long Time department, the FCC granted a waiver requested by the ARRL that clarifies the rules concerning the use of TDMA (i.e., MOTOTRBO or DMR) on the ham bands. I posted on this topic way back in March 2011, so refer to that article for the background. Update: ARRL article posted here.

I was surprised to find that the FCC quoted my comments that I filed on this proceeding:

Some commenters state the proposed rule change “removes an ambiguity in Part 97 concerning the use of single slot TDMA technology” and it “enable[s] and encourage[s] the adoption of spectrally efficient narrowband technology.”  Comments of Robert Witte at 1.

OK, fine, it was buried in the footnotes but I appreciate the mention. I can now die in peace knowing that my name is in the FCC record and not associated with a rules violation 🙂

Thanks to Jeff K0RM, for pointing this out.

73, Bob K0NR

Proper Kerchunking

Recently, on one of the email reflectors associated with repeater owners, someone asked how to deal with kerchunkers on the repeater. The term kerchunk means to key up the repeater to see if it is there. It just takes a quick push of the Push-to-Talk (PTT) button on the transceiver to bring up most repeaters, resulting in a kerchunk sound.

It seems that this repeater owner had someone that was kerchunking his repeater on a regular basis and it was making him looney. This led to the usual discussion of whether kerchunking is acceptable, legal or  moral and whether it should or should not be considered a capital offense.

Clearly, some radio amateurs have not been schooled in the proper way to kerchunk a repeater. The proper method for kerchunking is to key the transmitter and say your callsign, followed by the word “kerchunking”. This simultaneously identifies your station and indicates the purpose of your transmission.

To make the practice of repeater kerchunking even more efficient, I am proposing the adoption of these new Q signals:

QKC: I am kerchunking the repeater

QKC?: Are you kerchunking the repeater?

Thank you for your attention to this important topic concerning good amateur practice.

73, Bob K0NR

Seventy Three

Like many technical activities, amateur radio has its own set of jargon and protocols used both on and off the airwaves. As part of our Technician license course, we cover basic jargon but also encourage the use of plain language. A new Technician recently asked about the use of the term “73” on the local FM repeater, so I am posting this short piece.

Much of amateur radio history and practice is rooted in Morse Code, which traces back to the electrical telegraph. Two shorthand codes you’ll hear on both voice and Morse Code communications are:

73 means Best Regards

88 means Love and Kisses (sometimes Hugs and Kisses)

These codes originated with telegraph operating and are listed in the Western Union 92 Code, a set of numerical shorthand codes. On voice (phone) transmissions, you often hear something like this:

“Great to talk to you, Joe. Thanks and Seventy Three. This is K0NR, clear.”

Since 73 is often used at the end of a radio contact, it almost takes on the meaning of “best regards and goodbye.” “Eighty Eight” is used in a similar manner but is heard much less frequently on the ham bands.

Sometimes you’ll hear 73 expressed as “Seven Three”, which corresponds to how the Morse characters were sent. It is incorrect to say “Seventy-Three’s” since this would literally mean “Best Regards’s”. Of course, most of us have made this error from time to time, very similar to grammatical errors in the English language. (“Somes time we forget to talk good.”)

QRP operators often use 72 instead of 73 because low power operating is all about getting by with less. See W2LJ’s blog.

And I normally use 73 at the end of most ham radio related email messages.

73, Bob K0NR

TechDay 2012 – Your Start in Amateur Radio

Come join us on Saturday, September 15th, 2012 (9:00 AM to 2:00 PM) at the Tri-Lakes Monument Fire Administration Complex at 166 Second St. in beautiful Monument, CO for a half day workshop aimed primarily at the new Technician Licensees to help them get started in ham radio. While you’re here you’ll learn what it takes to be a ham radio operator, brush up on your DXing skills, test  your own ham radio equipment, check out some sweet mobile radio installations, and ask an Elmer “What’s so cool about 10 meters?”

Getting started in ham radio has never been so much fun!

Presentations

9:30 am – Youth DXpedition to Costa Rica
by Anna Veal WØANT

10:30 am – Mountaintop Operating
by Steve Galchutt WGØAT

11:30 am – Home Station Setup
by Anna Veal WØANT

12:30 pm – Getting On the Air
by Brandon Hippe KDØPWF

1:30 pm – Radio Equipment 101
by Shel KFØUR

* Each presentation is approximately 15 minutes with 5 minutes of Q&A at the end.  Events subject to change

Booths – Open 9AM to 2PM

Get Your Radio Programmed with Local Repeater Freqs by RT Systems
hosted by Kyle Hippe KYØHIP & Cole Turner WØCOL

Check Your Radio Performance
hosted by Bob Witte KØNR

See an HF Station
hosted by Dan Scott WØRO & Stu Turner WØSTU

Ask Any Question – The Elmer Booth
hosted by Paul Swanson AAØK & Shel KFØUR

Understand Mobile Installations
hosted by James Bucknall KDØMFO & Ethan Bucknall KDØMFP

Getting Your Ham Radio License
hosted by Brandon Hippe KDØPWF & Eric Hippe NØHIP

Ham Radio & Public Service
hosted by Randy Meadows KNØTPC

Sponsors

Tech Day 2012 is proudly sponsored by the WØTLM Amateur Radio Club and the  Pikes  Peak Radio Amateur Association.

Get the one page flyer in pdf format here.

Direct any questions to Bob KØNR

The World’s First Disposable HT

Baofeng UV-5RA few weeks back, I was wasting time doing important research on the internetz when I came across the Baofeng UV-5R Dualband Handheld Transceiver.  This radio seemed to have a boat load of features but the sale price was $65. So I am thinking to myself, just how good is a $65 radio?

The last time I went out to a nice restaurant, I blew through $65 pretty quickly so this was not going to be a large purchase. In fact, I realized that we now have HT’s priced low enough to be an impulse buy. As one of my ham buds told me, “filling up the gas tank of my truck costs more than this radio!”

So, of course, I soon broke down and ordered one and it showed up on my doorstep a few days later. I’ve been using it off and on for a few weeks now. I’ve also noticed that there is a real buzz on the interwebz about this little radio. There is usual Yahoo Group (baofeng_uv5r) and youtube videos.

Here’s the short story:

While not perfect, for $65, this radio is impressive.

Besides using the radio and receiving good signal reports, I did check the receive sensitivity, transmit power and frequency — all good. There are quite a few reviews out there, so take a look at articles by W0HC, PD0AC and OE1RFC. Also, there have been quite a few reports of quality problems with this radio…probably more defects than equipment from the more established ham equipment vendors. See the Yahoo Group discussion to understand this better.

Similar to other radios from China, this radio has a quirky user interface…not as easy to use as my Yaesu FT-60. This means that the programming software is a necessity to get the radio set up correctly, which is the major downfall of the rig. The free software program is crapware, with many people reporting a variety of problems with installation and operation. I did finally get it to work, but it was very frustrating.

I find myself grabbing this HT when I head out the door and leaving my other radios sitting in the desk charger. Someone pointed out to me that the low price of this radio makes it an easy choice — if it gets dropped, broken, lost or stolen, I am only out a tank of gas. While I am kidding about the “disposable radio” idea, the low cost does affect how I use it.

73, Bob K0NR

Don’t Get Stuck On 2 Meters

When I first got started in amateur radio (many years ago), one of the engineers that I was working with at a summer job told me “Don’t get stuck on 2 Meter FM”. At the time I was a college student and felt lucky enough to have 1) found time to pass my Novice exam, including Morse Code test, 2) found time to travel 150 miles to the regional FCC office and pass my Technician exam, and 3) scraped up enough money to buy a basic 2 Meter FM mobile rig. I was in Technician ham heaven, playing around on 2 Meter FM, both simplex and repeaters. Oh, and we had this cool thing called autopatch that let you make actual phone calls from your car. I really wasn’t worried about getting “stuck on two”.

Even though my discussions with this Old Fart Experienced Radio Amateur revealed that he didn’t see 2 Meter FM as Real Ham Radio, I could see that he had a point. Two meter FM is only small part of the ham radio universe and it would be easy to just hang out there and miss out on a lot of other things. I was reminded of this recently by K3NG’s post: Things I Wish I Knew When I Was A Young Radio Artisan. I agree with most of his comments with the exception of this one:

Don’t get your start on 2 meter repeaters.

This took me back to the comments from the Experienced Radio Amateur from years ago. I get the point — starting out on 2 Meter FM and Repeaters can give you a limited view of ham radio — but I see it as the perfect platform for getting started. Here’s what is working in my area with new Techs: get them started with a dualband FM rig (usually an HT) so they have some on-the-air success. This also puts them in touch with the local ham community, where we not-so-subtlely expose them to other bands, modes and activities. They hear the other guys talking on the repeater about working DX on 10 Meters and start thinking about how to pursue that as a Tech. From there, it just expands out to all kinds of bands and modes.

Just for the record, I guess I did follow the advice of the Experienced Radio Amateur and managed to not “get stuck on two” (i.e., I’ve worked all of the bands from 80M to 10 GHz, earning WAS, WAC, DXCC and VUCC.)

73, Bob K0NR

The Incomplete List of Ham Radio iPhone Apps

It was time to upgrade my Verizon Wireless phone, so I decided to move to a smartphone. After pondering whether to go with Android or Apple, I finally settled on the iPhone 4. I still miss the The Real Keyboard on my old LG EnV3, as it is nearly impossible to type on a shrunken touchscreen. But then there’s those apps…

I have been trying out some of the ham radio related applications on the iPhone, so I thought I’d report out what I have found.

Here are a few utilities that I found. These apps doing something relatively simple:

CallBook (Author: Dog Park Software, Cost: $1.99) Simple ham radio callbook lookup that accesses the WM7D database (or QRZ and Ham Call databases if you are a subscriber).

Maidenhead Converter (Author: Donald Hays, Cost: Free) Handy app that displays your grid locator, uses maps and does lat/lon to grid locator conversions.

Q Codes Reference (Author: fiddlemeragged, Cost: Free) This app displays the definition of the common Q Signals (QRZ, QSL, QTH, …)

UTC Time (Author: Michael Wells, Cost: Free) A simple app that displays UTC time and local time.

Sunspot (Author: Jeff Smith, Cost: Free) A simple app that displays solar data from WWV.

Ham I Am (Author: Storke Brothers, Cost: Free) A handy app that covers some basic amateur radio reference material (Phonetic alphabet, Q Signals, Ham Jargon, Morse Code, RST System, etc.) Although I find the name to be silly, I like the app!

There are a few repeater directory apps out there:

QSL.FM Mobile (Author: Robert Abraham, Cost: $2.99) Geolocation repeater directory and call sign lookup.

iHAM Repeater Database (Author: Garry Gerossie, Cost: $4.99) Geolocation repeater directory. This seems to work a lot better than the QSL.FM app.

If you are an EchoLink user, then you’ll want this app:

EchoLink (Author: Synergenics, Cost: Free) The EchoLink app for the iPhone.

There are quite a few APRS apps out there. I have tried these:

iBCNU (Author: Luceon, Cost: $1.99) The first APRS app I was able to get running. It just turned on and worked. It integrates the aprs.fi mapping into the app, so it is easy to use. I recommend this one for most casual APRS users.

OpenAPRS (Author: Gregory Carter, Cost: $3.99) This APRS app integrates into the openaprs.net server. A bit more complicated to set up but looks to be more flexible, too. You might want to check out openaprs.net before buying this app.

PocketPacket (Author: Koomasi, Cost: $4.99) another APRS app. Seems to work fine but I find the previous 2 apps more useful. Note: This app can function as a packet modem connected to a transceiver (no internet required).

Ham Tracker (Author: Kram, Cost: $2.99) APRS app, works OK, uses external maps such as Google and aprs.fi. “Share” feature allows you to send an SMS or email with your location information.

Satellite tracking is another useful app for a smartphone:

ISS Lite (Author: Craig Vosburgh, Cost: Free) A free satellite tracking app for just the International Space Station

ProSat Satellite Tracker (Author: Craig Vosburgh, Cost: $9.99) This app is by the same author as ISS Lite, but is the full-featured “pro” version. Although it is a pricey compared to other apps, I recommend it.

Well, that’s what I have found so far. Any other suggestions?

– 73, Bob K0NR

This is an older posting, see my updated list here

Hacking Away at D-STAR Hardware

dstarWe’ve been looking at optimizing the performance of the D-STAR repeater here in Monument (W0TLM, 446.8875 MHz), so I’ve been searching the web for information on what other groups have uncovered. Not surprisingly, there has been some creative reverse-engineering and re-engineering of the ICOM D-STAR repeaters.

Here’s a summary of some Good Stuff that I found:

1. NU5D paper on DSTAR Repeater Modifications & Interference Testing

2. A good overview of the ICOM D-STAR repeater block diagram and a few modifications to the ICOM repeaters on the dstar.ca web site

3. The N5EBW LED Board – a drop in board to add transmit/receive LEDs to the ICOM D-STAR repeaters

4. The Utah VHF Society D-STAR page — some of the best technical information and practical evaluation of D-STAR technology

5. A Look Inside D-STAR Modulation – an article I wrote for CQ VHF magazine that explains the vocoder and modulation scheme in D-STAR.

If you come across other D-STAR resources, please let me know.

73, Bob K0NR

Update on the Crossband Repeater Project

In a previous blog posting, I wrote about the construction of a portable VHF/UHF crossband repeater. I published the results of this project in my FM/Repeater column for the Fall 2008 issue of CQ VHF Magzine. I’ve adapted portions of the article to provide an update here.

To deal with the issues of identification and control, I decided to use a repeater controller to control two independent 2M/70 cm transceivers. Most repeater controllers are set up for conventional repeater control with a fixed receiver and fixed transmitter. What I needed was a controller that incorporated the concept of two independent transceivers that could be linked together, independently controlled and independently identified. The NRHC-6 Bridging Repeater Controller is designed to handle this specific case of connecting two transceivers. The block diagram of this crossband repeater system is shown in Figure 1.

Figure 1. Repeater system block diagram
Figure 1. Repeater system block diagram

I used a pair of FT-7800R transceivers which have a packet port on the rear panel that provides a convenient interface point for the repeater controller. This port has the required transmit audio, receive audio, PTT line and squelch line. The squelch line indicates the condition of the receive squelch, including the effects of CTCSS decode if enabled in the transceiver. (Not all transceivers behave this way… some only provide carrier squelch even if CTCSS decode is enabled.) Table 1 shows the signals available from the packet port and how they are used in the repeater interface.

Table 1. FT-7800R Packet Port

Pin

Label

Description

Repeater Interface

1

PKD (Data In)

Packet Data Input

Transmit Audio

2

GND

Signal Ground

Ground

3

PTT

Ground to Transmit

PTT

4

RX9600

9600 bps Packet Data Output

5

RX1200

1200 bps Packet Data Output

Receive Audio

6

PKS (SQL)

Squelch Control

CAS

The NHRC-6 controller has a versatile feature set that requires some programming to make it work. It supports two radio ports which can be configured to handle two back-to-back simplex radios. The controller has DTMF control, which can be accessed from either radio port. The five saved setups are handy for storing away specific repeater configurations. Each radio port can have its own courtesy tone and CW identifier, along with the usual set of hang timer, ID timer, timeout timer, etc. The crossband repeater can be turned on and off remotely using DTMF on either band.

Figure 1 shows two separate antennas, one for 2 Meters and one for 70 cm. In most cases, I use one dualband antenna and a 2M/70 cm duplexer to allow the two radios to feed the antenna. I also keep the radios set at less than full power to minimize the heat dissipation problem.

figure-5-crossband-repeater-system
Figure 2. The crossband repeater in a 19-inch rack mount case.

This crossband repeater is housed in a portable case that has standard 19-inch rack hardware (Figure 2). The two transceivers are mounted to a 19-inch shelf using their normal mobile mounts. The NHRC-6 controller has its own 19-inch rack mountable chassis. The case has a front and rear panel covers that snap on, protecting the equipment during transit. The system runs off of 12 VDC. I did not include an AC power supply inside the case. Depending on the location, I simply connect the repeater to a 12 volt car battery or a compact AC switching power supply.

I’ve used this repeater as a standalone UHF repeater by adding a small mobile duplexer to provide transmit/receive isolation. Of course, in this case, the two transceivers both operate on the 440 MHz band with 5 MHz offset. I’ve also used it as a crossband repeater, usually to extend the range of a 2 Meter repeater.

– 73, Bob K0NR

Portable VHF/UHF Repeater Project

My latest ham radio project is assembling a portable repeater for VHF and UHF operation. The basic idea is to package two VHF/UHF transceivers and a repeater controller into a rack mount box that can be easily transported and powered from a 12 VDC source.

I chose the Yaesu FT-7800R for the transceivers since it covers the 2M and 70 cm bands and has a data/packet port for easy access to the required control signals. Specifically, the data port has transmit audio in, receive audio out, squelch signal and PTT (Push To Talk). The repeater controller used is the NHRC-6, which is designed for use as a bridging controller between two transceivers. Most repeater controllers are set up for a conventional repeater configuration, always receiving on one frequency and always transmitting on another. I plan to use the repeater in this mode (on the 70 cm band, with a small UHF duplexer) but also wanted to run the transceivers in a crossband repeat mode. The NHRC-6 handles this quite well, able to route audio in both directions between two transceivers and with identification support for both rigs.

I’ve got the system assembled and I am playing around with the configuration. More to follow, probably in a CQ VHF article.
73 Bob K0NR