Wednesday, April 21, 2010

DCS Callsign, MDC in the 80s

Wow, You learn something every day. Apparently at one time DCS would let you transmit an ASCII ID too. Kenwood made a box called CD-10 that would plug into a regular radio to display callsigns received in this way. CD-10 Manual

Looking around I see reference to an HT made in the mid-80s that transmits the IDs. Kenwood TR2600A Very neat stuff. Apparently it sounds like MDC which is a system that is or was used in commercial radios used in police cars to transmit a station ID at the beginning of every transmission.

This is the kind of stuff that is only just recently available again and even then only if you use Dstar. It'd be pretty awesome if the DCS ID thing came back on the analog side I think.

Edit: Kenwood's TM211 had support for transmitting the IDs. Via the TM211 manual (Section 5) I see that it assigned letters and numbers to various DCS numbers.

Wednesday, April 7, 2010

My pixie II kit I built the other day. It's not "Done", I have some work to do on it. I really need a small bit of coax to connect to the antenna jack, which is a RCA jack on this. Frequency is a little off of 7.040. I haven't had a chance to check where it is exactly.

I haven't figured out how to measure it with my oscilloscope I bought a couple months ago. It's an old 60mhz analog scope that I think was formerly used at NASA at one point (Whoa!)

Waveform on receive, measured at antenna. The oscillator in this is always running so there's no chirp when it is keyed up. Measured at .1v/div.

Waveform on transmit, again measured at antenna. 2v/div. Nice clean sinewave. Picture is dark because I set my camera to 1/125s so not much light was collected. More than enough for a nice sharp image of the trace even though I'm holding the camera. :)

Blogger is giving me really annoying problems trying to format this with the pictures in the compose view. >:(

Monday, April 5, 2010

Programmer scanners

You know, I always wonder why noone has brought out programmable scanners. Yes I know there are scanners that are called programmable scanners. Really old scanners used crystals and you had to have one for each frequency you wanted to monitor. Then someone built scanners that had PLLs and digital readouts and direct entry of frequencies and called those programmable scanners.

I want programmable scanners more like my graphing calculator. Is that too much to ask? Give me a nice sized screen, at least a basic interpreter and a computer interface by default. Even if the programs couldn't be built interactively on the radio itself, I could live with that I guess. Even something fairly low power like a z80 level of performance would be better than the fixed, closed systems we have now. Higher power options would add even more uses, albeit possibly at the cost of some battery life. Imagine one with a Cortex A8 ARM processor running Android or Linux doing software decoding of digital communications right on the scanner itself. Add a GPS module and you could have a portable APRS receiver that can show your location compared to others. (I'll admit this idea is nicer if someone would add it to a transceiver instead)

A computer serial interface is just something that every scanner should have by now whether most of its intended audience would use it or not. I'm rather certain all units have some sort of microprocessor built in that could at the very least give serial control and read out with a little programming and probably less than 50 cents worth of parts.

My Icom R3, which is one of the more advanced scanners I've ever owned, doesn't even have computer control. I can read frequencies out of it and write new ones in but I can't control it and even if I could, the interface is the speaker out.

Bluetooth would be nice too. I've seen that the VX8R has an optional addin for bluetooth but it's MSRP is $99. I wonder how much of that is justified or if it's mostly price gouging since pretty much noone else is offering it. From what I've read the bluetooth is exclusively for hands-free operation. Not a bad thing I agree but would it kill them to add some serial protocols to it so that you can pair it with a computer and control the radio and/or use the packet without additional cables? Probably.

Sunday, April 4, 2010

Pixie 2 QRP rig

Recently acquired two of these boards with all components for building the Pixie. I got crystals for 7.040 with them. The documentation says they can work from 10m-160m depending on one inductor and the crystal. From what I've read you really need to make more modifications than that to put on higher up than 40m. I got the kits from HSC electronic supply. The kits include inductors for 40m or 80m but crystals are separate. I built one kit and a friend of mine built the other one. Now all I need to do is learn morse code again! I haven't touched it in 10 years or more and I just barely knew it back in the day.

It was, nonetheless, very satisfying to build the circuit. I also had fun diagnosing and fixing the problems with the other circuit. I put mine in an "astonish-mint" tin (altoids clone from Meijer) and my friend put his in a neat little wooden box that had some drill bits or some such in it at one time.