Thursday, December 17, 2015

Transmitter Hunting Loop

Finally a directional antenna for RDFing that fits in the car.
"A Uniquely Tuned 2-Meter Transmitter Hunting Loop" - by W6NBC, QST Jan 2013

The attenuator is from May 1998 QST.  "A Rugged Compact Attenuator" by N9SFX.

Saturday, November 14, 2015

DMR Likes and Dislikes

I recently eluded to that I have been playing with DMR.

I helped get one going locally.  And the only real reason I did that was to learn a bit about it.  Heck I don't even own a radio.  But a friend was nice enough to give me a Motorola XPR-6550 loaner.

I like the TDMA part.  To me it's truly digital.  Everything else that I have played with seems like digital audio on a FM modulator.

The XPR has nice loud digital audio out of it.  You'd expect this from a Motorola.  The audio coming out of my IC-92 for D-Star was never loud enough unless you were in a quite room.   The digital audio out of the XPR sounds really good.  This is because it uses the AMBE+2 vocoder, and a better sample rate than D-Star.   Motorola products do post vocoder DSP.  I have a recent DSP firmware in the radio (and yeah that is upgradable).  It sounds better than D-Star on the IC-92, and sounds better than P25 that I was doing with an old mid-90's Motorola Astro Saber (old DSP firmware in that).  I have an XTS-2500 that I listen to the County Police on, and while this XPR DMR radio is close in quality, I still say the XTS-2500 sounds better. The XPR doesn't go R2D2 like the IC-92 when people get into a crappy signal situation.  It mutes.

I like that you don't have to buy Motorola to use it, there are plenty of DMR radio options, like Connect Systems, and a very reasonable option at that.  Which is good because while I like Motorola, their software and customer service is a night mare on all accounts.

DMR wasn't custom made for ham radio, so you can't put your callsign into the radio like D-Star.  Each DMR radio uses a numerical identifier.  You can create alias/contact lists in your radio, so that when my DMR- MARC id of 3155089 is transmit, it shows as KB9MWR on your radio.  So the contact list thing can get to be big on a network.

When my friend was first trying to get my interest in DMR he kind of emphasized the DMR apps.   There are several ham DMR projects on github, but all of them are for the infrastructure.  In all honesty I am not sure what one would write for the end user app wise.  Maybe extend D-Rats support to DMR?  There are number of application development documents available to developers from Motorola, if you can get your hands on them.

Programming the radio's is pretty confusing  There are pre-made code plugs however.  I do like how when you connect the XPR-6550 programming cable to your PC it comes up as an ethernet interface.  And yes you can run wireshark on it.

Texting (sadly the DMR networks don't really do much with this part) is much better than with the IC-92.  On the IC-92, you had to dial in each character (possible 26+ dial clicks) and hit select when the character was the one you want... rinse, repeat, etc.  With the XPR-6550 and CSI radios, its like a T9 telephone keypad.

You can have a private call on DMR.  (Though discouraged on the network) This is unlike most of ham radio where you have a carrier squelch receive option.  With DMR, there is no listen to all traffic on the channel.  You have to specifically program talkgroups you want to hear, etc.  I never really figured out how to callsign squelch on D-Star.  So at least on DMR, you don't have to listen to everyone just to keep an ear out for your buddy, etc.

The repeater (XPR-8300/8400) is still basically two mobiles in a box like D-Star.   The engineering is better however. The repeater has a network jack in the back.  I like that I don't have to be the Linux systems admin or have a computer at a remote site.  Though hack/adaptability is more likely with the latter.  Network connectivity to the repeater is stateful, so it doesn't require any port forwarding.

Repeaters can be had for next to nothing on a promotional/regional basis like how D-Star got started.  In this case, there are two Motorola engineers that are competing to build networks, that don't appear to have any real backing a higher level.  One network is DMR-MARC, the other DCI.  Both have restrictive rules like the main D-Star network about linking to other things, etc.  Like with D-Star people grew tired of the network rules and began to roll their own network that is more friendly to experimenters, for DMR it appears to be DMRX/BrandMeister.

Even with two time slots, with all the remote/linked talkgroups you some times wonder if two slot TDMA is enough. When things get busy a radio "Bonk" is common to come back when you go to transmit, indicating that time slot is busy.

The XPR-6550 has a GPS built in.  In my other DMR post, I show how this can be bridged to the APRS network.  I like that.  I never did buy the uber expensive GPS microphone for the IC-92.  So far I haven't spotted a cheap non Motorola DMR radio with GPS. 

So what is the lure to the end user?  I guess that would be radio manufacture choice, and less R2D2.  The radio options are commercial, and some (CSI ones) are somewhat field programmable.  There are no-dual band ones yet.  The other lure might be that you use DMR at work as its pretty common, so you are used to it etc.

So far I haven't heard more interesting conversations than I have else where.  Call me strange but I really don't give a crap about having some over priced toys that lets you talk to other people. I can do that with analog, or no gear at all. I am here to try and learn something.

I am not sure if I'll buy a radio.  It's really a matter of if it actually takes off in my area.

Saturday, October 3, 2015

Research an Old License or Callsign

Recently my local ham club celebrated its 75th anniversary.  I took up a small project of trying to trace some of the clubs history.  A large portion of that entailed looking up old callsigns, to help piece things together.

QRZ's notes give the history of FCC records and the dilemma.  Basically they didn't start to use computers for keeping records till the 1980's.  Prior everything was kept on paper.  The only publicly searchable database is the 1993 one that QRZ has. has obviously been transcribing old flying horse callbooks. They have a reasonably priced subscription service that will give you electronic access to an archive of of old callsign data; 1921, 1954, 1957, 1960, 1969, 1977, 1983, and 1995 to present.

If you are looking for some really old data for free, there is a pretty good guide at  These are Google Book and Hathi Trust scans of government publications mostly prior to the creation of the FCC in 1934.  They can be downloaded in whole if you have a University login (Net ID).   Please contact me if you can help with this.

When researching a call its good to know, how long there were issued for:
In the 1920's - 2 year terms
In the 1930's - 3 year term for all classes.
In 1945, all except the novice (1 yr) are now 5 years
In 1967, the novice is now good for 2 years, all others 3 years.
In 1976, all license classes went to a 5 year term, including novice
In 1984, all license classes became ten years, as they are now.

At some point, apparently in the 1930's, the U.S. Government stopped publishing call books. Instead, this task was taken up by private publishers.

For many-many years the resource to have was a printed callbook.

The Citizen's Radio Service Bureau (508 South Dearborn St., Chicago IL) published the first issue of Citizen's Radio Call Book 1921 to 1932.

Then in about 1926; The "Radio Amateur Call Book Magazine" were published by Radio Amateur Call Book, Inc., Chicago, IL.  These are commonly referred to as the "Flying Horse Call Books"  because of the distinctive artwork always appearing on the cover.

Anyway I decided to scan the ones I had access to when I was researching my clubs history.   You can view them on the internet archive here:

I scanned them the best I could, in case someone really wants a project, of trying to convert it all to text and possibly put the info into a database.  Because printed call books were only organized by callsign, not by name.

One of the problems with converting to text (besides possible OCR errors is that the data was on multiple lines.  So you have to script something to look for a possible callsign match to indicate the start of a new record.

Anyway if anyone has any scans or of old printed books they would like to get to me, I'll see to it they get posted for all.

If anyone wants to try converting these to a CSV text file, go for it.

Thanks to the out pouring of hams donating scans and old call books.  There are about 60 now loaded on from 1909-1997.

Friday, September 4, 2015

Text to Speech and Ham Radio

I use text to speech engines (TTS) in a number of ham radio applications.  When you are dealing with voice communications and repeaters, it is handy to announce the time, IRLP, EchoLink, Allstar connection status etc.

Heck even as things move digital, I use them.  Lets face it, when mobile listening to your radio is a lot safer and convenient than looking down at the display.

Linux comes with the Festival speech synthesis system, but by today's standards it really doesn't sound very professional.  Sadly Festvox, Flite, and Espeak all sound about the same.

Cepstral was founded in 2000 by leading scientists from Carnegie Mellon University, where Festvox/Flite was developed.  And it sounds quite a bit better.

Cepstral isn't open source, but they have Linux builds available.  Early on, the cost for a license of Cepstral was only $30.  In 2013, when version 6 came out, they started using the new licensing scheme which made it impractical for hobbyists.

About this time some people figured out how to use the Google Translate tool to generate instant text to speech.  Many people switched to this.

Sadly just recently Google deprecated free access to the language translate api. (There may be ways around this, but for how long?)

I wish someone would create a kickstarter campaign or something like that to take up a collection to get someone to contribute an updated open source TTS voice as part of the standard Linux distributions. Festival/flite are all pretty rudimentary sounding.

Recently our local National Weather Service Office announced "that for the first time in over 15 years, the NOAA Weather Radio system is getting an upgrade. A new computer system will be used to generate audio recordings of the forecasts, observations, watches, and warnings which are routinely heard over the air. The actual broadcast programming will remain unchanged, and there is nothing you need to change on your radio to continue receiving warnings, watches, and forecasts from the National Weather Service.  But listeners may notice that messages are being read in a different voice."

Wouldn't it be nice that when the government spends money on software, they would put those software projects out to bid and tack on an open source requirement?  That way the taxpayers would benefit in more than once way from how their money is spent.

I read a while back that Russian Prime Minister Vladimir Putin ordered government agencies there to transition to open-source software.  And something about a government funded national repository for open-source software.

Monday, August 3, 2015

DMR <-> SIP Translation

When I first got interested in D-Star, there were some discussions on building a D-Star to SIP bridge.

This was back in 2011, now DMR seems to be taking off as I just wrote in my last blog entry titled AMBE proxy.  Once again that nasty AMBE problem?

However Trbonet ( software dispatch thingy does allow you to dispatch from a PC.  So unless this software has some DVSI/AMBE licenseed code in it, there must be a way to address both sides of the AMBE vocoder in the Mototrbo repeater and or radio.  If there is a way to address the input side of the AMBE+2 vocoder in the radio, then you can jack the audio in that way, instead of through a bastardized speaker mic (as an analog hack)

There are a number of interesting DMR related projects on gihub.    The first we stated to play with locally was KD8EYF's TRBO-NET perl scripts:

Showing some interactive text based commands sent from a DMR portable, and the replies from the KD8EYF powered information gateway. Weather reports, sending APRS messages, last heard status of a station, etc.

DMR does actually seem more well suited for a SIP to private call bridge.  D-Star really has no way to know when the call ended to be able to tear down the SIP connection.  It also has no real way to know if a particular D-Star radio is even on.  DMR on the other hand can do all this.

Other ideas:   When mobile it might be nice to have the various responses to the quick texted queries  actually spoken with a text to speech engine.  And since your radio affiliates when you turn it on, maybe even custom repeater greetings/reminders.

When you try and send a text to someone who doesn't have their radio on, obliviously that times out.  In theory it should be possible to see there isn't a reply happening and have server accept the message on their behalf, and when that server sees the user next affiliate, send the message to them then.  (Much like how it works in the cellular world)

The same could apply to a private call that isn't being acknowledged.  The server recognizes this and asks using a text to speech voice if you'd like to leave them a message.  Again playing the message to the user it was original intended for when they next turn on their radio and it phones home to the repeater.

This one seems to incorporate some audio related things: As of this writing, a large multi-national ham radio group has deployed this on TGID 9998 and dubbed it the "parrot". This application can listen to group and/or private voice transmissions and if you trasmit to the group and/or private IDs it's programmed to use, it will record the digital packet stream and then re-play it back. Handy for listening to your audio to see what you actually sound like on the air


Tutorial for Setup of Hytera Phone Patch via SIP: