"What news from Plymouth?"

Well, so far as I am aware, Plymouth continues to be in Massachusetts. If this situation should change, I hope one of you, Dear Readers, will be so good as to tell me.

News in my neck of the woods has nothing to do with Plymouth at all. However, if you're stuck on Plymouth, I suggest this brief riveting look at the court of Elizabeth I (Plymouth was an English colony during her reign).

Now, the news of your humble polymath-in-the-making. To begin with, Dear Reader, you might be wondering why the promised posts from NAB never materialized. This is because I did not go to NAB, and I will not be going to the Radio Ink Convergence Conference either. In fact, I have been disqualified altogether from the Technology Apprenticeship Program, and that's because I got a job at KTBG and KMOS, the public broadcasting service of the University of Central Missouri. I'm an engineer! This is a very exciting time for me - so much to learn! Interning at KCUR taught me a bit about radio (though here we have to worry about a thing called "short-spacing" which means we have to have a cardioid antenna pattern - more on that as I learn about it) but I know nothing (yet) about TV.

One of the things I'll be doing at KTBG/KMOS is applying my IT experience and knowledge to our setup in broadcasting. So there will be some software development for various projects in between my regular engineering duties. For example, a short-term project I have is to take the output from KTBG's automation system and feed it into our new Inovonics RDS encoder. The encoder isn't installed yet - maybe John (the chief engineer for KMOS/KTBG) will let me do that too. If this encoder is anything like the unit at KCUR (also an Inovonics) I don't foresee a lot of difficulty; Inovonics uses RS-232 to feed data to the encoder, and the command syntax should be documented in the manual. So it's just a matter of parsing out the data from the automation system and presenting it in the proper format to the RDS encoder. No sweat.

This past Thursday, I made a presentation to the local SBE chapter on IP security. You can view it here, and maybe I'll make a blog post that elaborates on these points a little more.

Today, at the Ararat Hambash, I took the test to upgrade my amateur radio operator's license from General to Extra (I had previously upgraded from Technician to General at the end of March) and passed! This means I now have authorization to operate on all bands and modes available to the Amateur Radio Service (certain bands and modes are reserved for operators with a given license class). Of course, I still don't have any equipment, but that will come in time.

Adventures in ham radio

In my quest to become a broadcast engineer and general polymath, I've started getting into ham radio.¹. I got my Technician-class license in August of last year, and started operating on EchoLink, which provides VoIP connections to other ham operators and those repeaters connected to EchoLink. I made a couple of "Slim Jim"-type antennas, one out of twin-lead, the other out of ladder-line, but didn't actually get a radio until fairly recently.

My current radios are a Midland 13-505 that I bought at the last hamfest, and a pair of EF Johnson 9800 series radios that were given to me by a fellow ham. The Midland radio operates on the 2 meter band, which covers (for hams) 144 - 148 MHz. The Johnson radios operate on the 70 cm band, 420 - 450 MHz.

Neither of these radios is exactly ideal. The Midland is locked (unless I can find or build a synthesizer) to those frequencies for which it has crystals installed. As the Midland dates to the early 1970s, crystals to fit it are fairly rare. The Johnson covers the entire 70 cm band, but requires a special programming cable which I do not currently possess. I have, however, found two sets of plans on the Internet for building such a cable (here and here), so I think that I shall soon have that problem sorted.

As of yet, I have not been able to make a QSL (a contact) with either radio. Several times I have heard traffic on the Midland radio, but I have yet to be heard. I have heard nothing on the Johnson. I'm hoping all that will change soon, though, as I'm building a new antenna. It's another J-Pole (note that the "Slim Jim" is a special case of the J-Pole), but this time, I'm making it out of 1/2" copper tubing.

I used plans by G.E. "Buck" Rogers, K4ABT to get the proper lengths of copper tubing. I went to Westlake Hardware in Westport to buy the tubing, caps, tee, and elbow, and they were kind enough to cut the pipe in the lengths I needed at no charge. I haven't assembled it yet, as I don't know how to solder copper pipe together, but once I have, I plan to mount it on the railing to the stairs at the back of my house. That will give me a reasonable amount of height, especially compared to where I have my antenna now - hanging on the wall above a window in the rear of my house.

That's all for now, Dear Readers. I'll keep you posted (sporadically, of course) on my further adventures in ham radio. And I've still got all manner of things to talk about at KCUR. :)

¹Before you ask, Dear Reader, no, I still haven't learned where the "ham" in "ham radio" comes from. I'm sure it's on the Internet somewhere.

Recently at KCUR

Even though I haven't been posting as much of late, I'm still active at KCUR. Two weeks ago Robin and I installed a fix to the HD transmitter to prevent RF interference from the power supply. I'll note that Robin never mentioned noticing any kind of RF interference coming from the HD transmitter, but it's still a good precautionary measure to take.

This fix involved putting a ferrite choke around an internal power cable¹. The linked article discusses chokes in depth, but basically the point of a choke is to present a high impedance to RF currents. Any such currents that are generated along the cable will either be reflected up the cable or will be absorbed by the ferrite choke and dissipated as a negligible amount of heat. Also, we attached a grounding strap (a braided strip of wire) to the outside of the crossover pipe (rigid coax - where the generated RF signal comes out). Since the outside of the crossover pipe acts as a shield, I think this means that any stray currents on the outside of the pipe will be shorted to ground and won't get outside the transmitter cabinet.

This whole business took something like 15 - 20 minutes. The rest of the day was spent helping Robin out with various things around the station, including installing a T-1 surge protector in the TOC. Last week I did the same thing at the transmitter.

¹ Looking at the manual, the purpose of the cable is "current share", and I'm not sure what that means. If there's the potential for RF interference, I think it must have AC on it.

Setting up a little SMTP server to interface to another

I'd say, "Look, a non-radio post!", but this post is an elaboration of a reply I made to someone on Pubtech, so... :)

By way of background, someone on Pubtech was asking a Nautel rep when their VS Series transmitters would support SMTP servers that require login. I replied that until such a time, you could set up your own little SMTP server and use the server that requires login as a smarthost. Here's how you do it:

Step 1: get yourself a Linux box of some sort. Since this is (presumably) going to live at a transmitter site, and it would sure be nice if you could just "set it and forget it", as it were, I would recommend something like EMAC's Server-in-a-Box (SiB). With the SiB, It's not clear from their website whether or not it an SMTP server included in the Linux distribution it ships with, so contact the manufacturer to make sure. If it doesn't, I'm certain they can install the requisite software.

Step 2: configure the SiB's SMTP server to log in to your other SMTP server. There are a variety of SMTP server software packages out there, and I can't cover them all. I'm going to use Postfix for this example; if you need another example, comment on this post and I'll see what I can do.

This example is based heavily on the example posted here. Whenever you see mail.myserver.com, you should replace it with the host name of the mail server that requires login. Replace myusername with the username to log in to the SMTP server, and myPassword with the password associated with that username.

Create a text file on your server called "/etc/postfix/password". This file should look like so:


# server username:password
mail.myisp.com myusername:myPassword


Now, execute the following commands (note the '#' is used to indicate a command prompt):


# chown root:root /etc/postfix/password
# chmod 0600 /etc/postfix/password
# postmap hash:/etc/postfix/password


Then append the following lines to /etc/postfix/main.cf:


relayhost = mail.myserver.com
smtp_sasl_auth_enable = yes
smtp_sasl_password_maps = hash:/etc/postfix/password
smtp_sasl_security_options =


Finally, restart postfix:


# /etc/init.d/postfix reload


Give the SiB a static IP address (how this is done is outside the scope of this post), connect it to the network, rack it up, and give the Nautel the SiB's IP address for a mail server.

EDIT: The original poster on Pubtech replied that he couldn't have an open SMTP relay floating around. I'm not sure that I'd have my transmitter with a publicly (or semi-publicly) accessible IP, but then again, I'm not sure that I wouldn't. There are benefits and drawbacks to each, but that's a topic for another post. In his situation, I would lock down Postfix to only relay from the Nautel's IP. To do this, add these line to /etc/postfix/main.cf:


mynetworks = 127.0.0.0/8 192.168.1.23
smtpd_client_restrictions = permit_mynetworks, reject


Substitute 192.168.1.23 with the IP of the Nautel, of course. Reload Postfix again when you've added those lines.


And then

Watching the KCUR TX

Day 3 of the barnraising will come in due course, but I want to talk about something more recent first.

Recently, Robin took a well-deserved vacation - in fact, he went on vacation at the same time as I was at the barn raising, though he was gone for longer. At any rate, while he was gone (and I was in town) I got to take care of the transmitter. This involved putting my number as the first one in the transmitter remote's call list, getting the password to the remote control, and a set of keys. I also received a spreadsheet of what monitors were connected to the individual channels on the remote (a Burk ARC-16), so that I knew which channels did what.

In the time that Robin was gone, the transmitter did not blow up, and KCUR did not go off the air. Thus I am counting my first time as being the person in charge of the transmitter a success. However, I could have done a fair sight better, I think, and I plan to do better next time. First of all, voltage. A couple of times I got calls from the transmitter saying that the voltage was low. I cleared the alarm, and figured that since the transmitter didn't call me again after I cleared the alarm, the problem was transient and nothing to worry about. In fact, it was not a transient problem, and when Robin got back he had to call KCP&L to get the voltage back to where it should be. Additionally, this low voltage situation was causing the transmitter to operate inefficiently, causing the room to be overly warm. There was also a problem with the HVAC - the air conditioning wasn't blowing cold air. I got calls from the transmitter once or twice warning that the temperature was above the set level, but again, since the transmitter didn't call again after I had cleared the alarm, I figured it was a transient problem. Ultimately, it was an error in my thinking: these "transient" problems were still problems that warranted investigation.

I also went over to the TX last Saturday, while Robin was gone, to try and get VINA, an organization that leases a 92kHz subcarrier from KCUR, back on the air. They had sent a box of equipment to the station for us to install at the transmitter in place of the equipment they had been using. During the week I had been out to the TX to replace the satellite (they get their signal via a Ku band satellite downlink) receiver they were using, but that wasn't enough to get them back on-air, so I went to replace the LNB on the satellite dish located on the roof of the transmitter hut. I got the LNB replaced, and I got some signal on the air, but it wasn't very strong, and it sounded distorted. It wasn't until this past Monday, when Robin came back, that we were able to get VINA on the air properly. I ended up having to rotate the LNB almost 50° from the 0° mark on the bracket, and there was some damaged wiring that needed replaced as well.

So all in all, I'm treating my first time watching the transmitter as a lesson in proper thinking. As Robin says, you do all you can do until the job is done. If you can't do it, there's no shame in calling another engineer to assist. I'll remember that next time.

Barnraising: Day 2

(Posted *way* late. Sorry, I got busy. *g*)

Day 2 of the barnraising began with me trying to find all the web streaming equipment that had been scavenged to do the stream from the Cannonball Room. This did not go very quickly, so the streaming for some of the workshops got started late. The streaming happened, though, so I must count that as a success. :)

By the time I'd finished getting all the streaming going, I'd missed most of the morning workshop session, so I didn't get to finish the tiny transmitter I'd been working on the day before. That's all right, though - I can build my own when I get home. I bet I can even adapt the design to broadcast on ham frequencies - maybe have my own little 70-centimeter or 2-meter transceiver.

I was going to go over to the station and help out there after the morning workshop session. Instead I spent some time checking on the web streaming. When I went in to check on the streaming in the workshop about recruiting volunteers and preventing burnout, I was immediately handed a slip of paper informing me that I was an octogenerian stockbroker who loved to dance. This was a role-playing exercise, you see, where some of us were potential volunteers and some of us were people trying to recruit volunteers. I played along, stayed for a bit of discussion, then wandered off to see what else was going on.

One interesting feature of the barnraising was the interview booth. The idea is that two people go into the booth and one of them interviews the other. The other then returns the favor. A volunteer staffer is also in the booth, and they record the interview, along with a couple of station ID's, for later broadcast. So I and a pretty girl named Meghan went in, and she interviewed me. I talked about why I'd come to the barnraising, and how I was trying to move away from IT and into broadcast engineering, and what got me into radio in the first place (a subject that I should perhaps elaborate upon in another post). I even briefly mentioned my days as Uncle Squishy, the host of the WEFT children's music show. (Uncle Squishy later reappeared as the occasional host of one of my WEFT overnight shows).

What with one thing and another, I didn't get over to the station until after lunch. I helped Sakura from Prometheus set the levels on the board, hung out while a carpenter was drilling holes for cables, and helped design a set of shelves to hold equipment until such time as a rack was obtained for said equipment.

Let me briefly describe the way we set the levels on the board. This may well not be industry standard, but once WGXC goes on the air, they can always adjust them again.

To start with, all the faders on the board were set to the same point. The reason we did that was to try and make sure that two given pieces of equipment would have roughly the same perceived volume when the faders on their respective channels were at the same point. When you've got a radio station, you don't want to have to remember that having the fader, say, halfway up on the CD player is fine, but having the fader halfway up on a microphone is *way* too quiet.

Using a Behringer cable tester, we generated a test signal. This signal could be set at three preset levels (i.e. volume) - one for microphones, one for consumer-grade equipment, and one for professional-grade equipment. For each channel on the board, then, we chose the appropriate level and ran it into the board. We then adjusted the trim pots - which are these tiny potentiometers (i.e. a variable resistor, often used to control volume) that you use to adjust the levels on a particular channel. Remember what I said above about having all the equipment being at the same volume for the same fader position? The trim pots are what you use to make that happen. In the case of the six (there are three physical mic modules, but each module on that board takes an "A" and a "B" input that you can switch between) microphone channels on the board, we only adjusted one pot each, because microphones are mono devices. For everything else, we adjusted the left and right pots separately. We set each channel so that with the fader about a quarter of the way up, the VU meter was near +1¹.

I left for dinner, and when I came back, I made a couple of XLR cables and helped run wiring in the studio. I really like the way their board does things - it's an Arrakis MARC-15. The neat thing about the MARC-15 is that the A & B inputs on each channel are RJ45. They're not Ethernet, though - it's not an IP console. Instead, the pins on the RJ45 are wired such that you can fit two balanced audio channels and a contact closure relay (a dingus that shorts two electrical wires, often used for start/stop control of attached audio devices) onto one jack. I like this idea. If you do it right - only have the wires going to your connectors be a few inches long, and the rest of the wires be contained in the Cat5 sleeve - it keeps the wiring very clean and compact. I'm on a plane right now, otherwise I'd post a picture.

Once things wrapped up at the studio, I made my way back to St. Mary's Academy and helped clean up, then went back to the Youth Center to sleep.

¹ A VU meter (VU for "Volume Unit") is a thing on a console that tells you, effectively, how loud your broadcast is. It's an analog thing with a needle. The ranges vary from meter to meter, I expect, but I think the one on the WGXC board went from -10 to +3. That's probably a logarithmic scale.

Barnraising: Day 1

I got up this morning around 0700, hit the shower, and went to "Debbie's Lil' Restaurant" in Hudson for breakfast with a couple of other barnraising folks. One of them grew up in the Champaign-Urbana area - a place I spent several years - which was pretty cool. He was a WEFTie for several years - another connection we share.

After breakfast I volunteered to help out with the web streaming of the various workshops. There are four web streaming kits, but they don't all have the same hardware. Three of them are using Behringer UB1202 mixers and a PC or Mac laptop to stream to an Icecast (or Live365 in one case) server. One of them is using a Marantz digital recorder where the line out goes to a PC streaming to the Icecast server. Every session was recorded with a single condenser mic.

The barnraising is largely a DIY thing when it comes to equipment. People bring what they have. So it's only to be expected that there will be a serious diversity of equipment. That doesn't make it easy, though. I had to run around to try and find 1/8" to 1/4" headphone adapters that I could plug into the headphone output of the board, for example, as none were supplied. Later, I realized that it was better to start up the media player on each laptop - that way whoever was monitoring could hear the audio as a listener would hear. Of course, it ended up that no-one was monitoring, because there was only me to do it, but it's good practice for tomorrow's and Sunday's sessions.

After I had the web streaming set up, I went to Pete Tridish's workshop on building tiny transmitters. The transmitters were based on the designs of Tetsuo Kogawa. There weren't enough materials to go around, so I worked with a group of two other folks. We got as far as getting the resistors soldered on. :)

After dinner I went over to the Cannonball Factory to hear the spoken word performers. There was a Finnish girl there who read a poem entitled "The Brothers-in-Law". The poem itself I don't remember enough of to comment on. However, she read it first in Swedish (she's a member of the Finnnish minority who are native Swedophones) and I was struck by the almost musical quality of the words.

There were two sets of spoken word performers. I left in the middle of the second set and walked over to the station to see if they needed any help over there. They were wrapping up for the night, so I went into the studio to hang out for a bit. At first I thought I was hearing some weird experimental music, but in fact it was the feed from the Cannonball Factory - the third set was a set of hip-hop performers, and the volume levels were considerably higher than the previous sets. This caused the broadcast (well, webcast) to sound like shit, so I went back and turned down the gain on the streaming PC.

After that, I went back to the crash space and went to sleep.

WGXC Barnraising!

http://prometheusradio.org/WGXC_barnraising

I heard about this on pubtech. They're putting up a full-power FM community radio station the last weekend in September. I totally want to go to this, but the registration alone is $100 at minimum (it's a sliding scale type of thing). Still, that's valuable experience, and I've got a couple of months to make arrangements...