It has been twelve days since I made my RF Exposure Calculator available for all to use. I admit that there were a few bugs in it when I first released it. But nothing that didn't get fixed within a day or two. You see, it being open source and all, I figured I should release early and release often. So what you see today is about 26 commits newer than the original.

I just can't believe that it was my own naïveté that expected a warmer reception to the ham world. I mean, there are no other RFE apps that can even come close to how cool mine is. And I am not just saying that to toot my own horn. All the other applications make you type in numbers and information time and time again. For each little change you have to type new stuff in again. And they don't remember what you typed in yesterday. Come on folks, get on the Web 2.0 bandwagon already (or something buzz-wordy like that). I got some positive feedback, for which I am very thankful. (This mad machine runs on props!) But I also got a bunch of "I don't get it," and "Where is the program? - All I see is a tabbed help page!" or "nada". All I have to say to you folks is RTFM!

The grand old story of The Emperor's New Clothes comes to mind. I wrote this awesome RF exposure calculator that only works for smart people. So if it doesn't work for you, well... sorry. Only I am not really that sorry. I mean it would work for you if you could only read. I designed it so it would start with help text showing if there was nothing else to display (thus the tabbed help), which TELLS YOU EXACTLY HOW TO USE IT! GAAAAAHHHHHH!

Okay. That felt good. And really, this post was half therapy for me and half directed right at the anonymous coward who says that "Blogs are the verbal equivalent of vomiting!" with reference to my blog. This barf's for you.

So far in my amateur radio career, I have not been able to offer much that may be of use to other hams. That changes today. A while back, when I was dreaming about where to put my antennas safely, I did a lot of research about radio frequency exposure. I poured over OET Bulletin 65, which details the FCC's limits on human exposure to RF electromagnetic fields. They have formulas and tables and forms to fill out. It is all wonderful and fine, if you live in the 1960s. Welcome to the 21st Century. We live in a world of computers to do all that number crunching for you. I looked around for any web-based things that would help, but the closest I could find was power density calculator written by W4/VP9KF. This is fine if you want to do it for EVERY band on EVERY transmitter each time you make a change to your station. Plus, it means that I have to transmit all that data to his PHP script, which does the calculations and sends them back. We have this great thing in web browsers called JavaScript, which is more than powerful enough to do the work. I set upon creating a JS-only version of his creation. But it still lacked the memory—I would still need to re-enter for each band for every change. And it wouldn't let me view multiple bands at once. Bigger calculator!

This is where my offering steps in. My requirements:

1. Save my data so I don't have to re-enter everything in every time
2. Something I can share with others, without saving their data on my server
3. Let me add, edit, delete at will
4. Something that can show all my transmitter/antenna/connection information at once

Seems easy enough, right? It was the first two that really got me stuck. I whipped up a little JavaScript ditty that fulfilled number four in very little time at all. Number three was dependent upon the first two and was technically the hardest, but once I had the first two figured out, it was only coding, which I enjoy.

And this is what I came up with: N7OH RFE Calculator. Take it for a spin, share it with your friends. Upon your initial visit, it may not look like much, but if you move over to the "Import/Export" tab, you can press the "Reset to sample data" button and see it in action. Please offer suggestions and comments if you find it to be too difficult to use or see something that might make it better.

As for fulfilling my four requirements, the first two were done once I learned about local storage with HTML 5. This means that your web browser is storing the data. Not as a cookie, but similar. Cookies get sent back to the server with each request. Local storage is meant to be persistent data that a web page can access via JavaScript to be used locally. This means I can save my data on my machine and your data on your machine. I can host the page for everyone, yet not save everyone else's data on my server. The add/edit/delete requirement was probably the most fun I have had with jQuery to date. And I hardly scratched the surface of what it can do. Lastly, the glory of the Results tab just makes me weak in the knees. Okay, not really, but it is the crown jewel of the whole application. It shows all the stuff you want to know about your radio setup.

I recently had the itch to change my Amateur Radio callsign because the one I had chosen before (NV2M) is from region 2, and I live in region 7. I didn't think it mattered that much, but it seemed that half the time I would tell someone my callsign, they would question me and ask again. I decided to find a 1x2 or 2x1 in region 7. I found a couple of 2x1 callsigns that were acceptable and then I read about how to 'pan for 1x2 gold' on a couple of websites. Basically if you can find a silent key (a ham who has passed away) that still has an active callsign even though he/she passed away more than 2 years ago, then you can request that the FCC cancel the callsign and you can apply for it.

I did what any programmer would do and downloaded the FCC database and wrote a script that queries the database for the callsigns I am interested in ([KNW]7[A-Z]{2}) and then queried the SSDI (social security death index) to see if that person had a record there. I found several that were immediately available and about twice that many that had passed away less that 2 years ago. I picked my favorite and applied. Then I requested that the FCC cancel the original license. So now I am the proud new owner of N7OH.

I picked N7OH because it is 1x2 in region 7, it has a light phonetic weight (No-vem-ber Se-ven Os-cah Ho-tel), it has a light CW weight (48, the same as NV2M), and it sounds cool in CW (dah-dit dah-dah-dit-dit-dit dah-dah-dah dit-dit-dit-dit). The last item on my list there was just the icing on the cake since I am still trying to learn CW. Beyond the 1x2 in district 7, the biggest deciding factor was whether or not I liked the sound phonetically. Some letters I like better than others. My least favorites are most of the three-syllable letters like juliet, romeo, sierra, uniform. November is okay, but only because it is common as a prefix. I also had a list of favorite and less favorite two-syllable letters. Let's just say that oscah-hotel is not my favorite, but it was loads better than the other options I had. And since 1x2 callsigns are so rare (2,028 for ~14,000 Amateur Extra operators in region 7; 20,280 for ~124,000 Amateur Extra operators nation wide) I figured I should just take what I could and not get to picky. Ideally, I would like K7VM, but that one is taken.

Ramble, ramble, ramble. Enough of that. Now to go order my Oregon Amateur Radio license plates for my car.

A quick test of my SWR meter that I have been working on for the past few weeks told me that something was awry. It is a slight modification of that circuit, adding a couple of capacitors and replacing the two ammeters with an Atmega8 microcontroller's ADC unit. I figured if I could stabilize the voltages sufficiently, the ADC could read them and directly calculate the SWR. So I am sure that at least half the problem is that I made some assumption in SPICE that does not account for or some newbie error like that.

I looked at the DC levels and all the connections. I double checked the schematic. I don't have a low-frequency (<150MHz) signal source, so I just went whole hog and plugged in my radio. Pretty much no matter what I used for the load (short, open, 50 ohms, etc.) I could not get anything other than the full reflection voltage. But my silly multimeter doesn't do 150MHz. I need an oscilloscope. Or whatever they used before oscilloscopes. An RF probe. So I built one.

After poking around on the internet, I found N5ESE's classic RF probe, which seems to have been duplicated in many places, even as as kit from Hendricks QRP Kits. I rounded up the parts and put it together. I had the bright idea of stuffing it into a small bit of 1/4" copper tubing to shield it. I ground down the end of a small allen wrench to be the tip of the probe. I put it all together, added a bit of epoxy and some heat-shrink tubing.

Disappointment must be my lot in life because the RF probe was not working right either. Measuring the voltage across a 50-ohm dummy load (three 3-watt 150-ohm resistors in parallel), yielded 30+ volts when my radio was set to 1/2 watt. Just for reference, 1/2 watt over 50 ohms is 5 volts. If I bumped my radio up to 5 watts, the probe said 250+ volts. My multimeter was not happy about that.

I built another one on a spare breadboard. It worked like a champ. Even with the extra capacitance of the breadboard (or maybe because of it???). And when I say it worked fine, I mean it worked fine at 150MHz. I tore the first probe apart and tested the components. If it really was putting out 250 volts, the diode and capacitor should be dead. The multimeter says they are both fine. I test the probe out of its container. It is fine. I build a new container, this time fitting the copper tubing into a pen tube. No epoxy. I test it again and this time it works. Hooray!!! The picture above is my final product.

Now I need to put it to work debugging my broken SWR meter. Maybe if I can assemble these simple circuits, I can graduate to a real project like the MMR40 transceiver.

A man in Nova Scotia has determined that radiation coming from the proposed nearby high-speed internet tower will mutate his organic garlic crops. Wow. I guess he heard that they were using microwave technology and decided to shut them down. Microwaves are the most deadly kind of radiation, right? 'Cause we use them in our kitchens to cook things. Oooh! I had better instill the proper amount of F.U.D. in all my neighbors so this tower will get shut down before it starts.

Being an engineer, I like to look at things skeptically. There are numbers and calculations to support everything. Do the numbers work out? Do the equations make sense? Is this man a fool? This is one of the beauties of learning more about amateur radio; I got to learn a lot more about electro-magnetic radiation than I ever did before. More specifically, what are the limits of what might hurt people. Now there are still debates going on about whether or not cell phones cause brain cancer and the like, but once again, it all comes down to simple physics. This is the same question as Lenny's garlic: will the radiation cause a "change [in] the DNA of the garlic because it shakes up the molecules" or not?

After much debate, research and saving of greenbacks, I finally went out and bought my first ham radio. I chose the Icom 92AD. It didn't take me much to see that the Icom handheld radios were a lot higher quality than the Yaesu radios. They also cost a bit more. The one I chose was one of the more expensive ones (surprise, surprise), but it should do all the things I want it to do. It is a dual-band radio that also has a digital voice/D-STAR capability built in. I am not sure how much I will use the digital voice part, but D-STAR also allows for data to be transmitted along with the digital voice packets. I think that KK7DS's D-RATS stuff is really a great idea. Plus, Dan's a bit of a Linux geek like myself, so I feel good supporting him.

The radio as a handheld doesn't really have a long range, but it will be great for the ARES and CERT activities that I would like to participate in. There is also a local LDS net that I can participate in as well. So it is a great start to get my radio feet wet.

Like I mentioned in my last ham post, I was not entirely happy with my call sign. I applied for a 'vanity' call sign, NV2M, and my request was granted six days ago. I think it is really nice that the FCC allows you to choose your call sign. They did periodically through amateur radio history, but now it is even easier than ever. You log into the FCC website, list your top 25 choices in order of preference, pay them thirteen dollars and wait for 21 days. There are several websites that maintain lists of call signs that are available so you can find one that suits you. Thirteen dollars is not very vain, especially for a ten-year license.

Now take a look at vanity license plates. Fifty-five dollars for a vanity license plate is vain. And you have to pay that each time you renew your registration. But here in Oregon, they have special amateur radio plates you can get for your car that display your call sign. The best part about this is that they are only five dollars. This is the kind of vanity that I can afford.

So it all comes down to the dollar. How vain are you? And Me? About five bucks. I think I am too practical and too much of a tightwad to be really vain.

I have been meaning to get my ham operators license for some time now. I never really knew what was involved in the process so I always let it slip out of my mind after a very short time. I knew that there was a "test" of some sort involved. And that you had to pay to take the test. Not wanting to pay for a test I might fail and not knowing where to turn to pass, I gave up. Until about 3 weeks ago. Then I heard about a ham class that was being offered locally. I actually heard about it through two channels: my church has been pushing to get people to have ham licenses for emergency preparedness, as has Beaverton CERT (Community Emergency Response Team). So when I heard about it this time, I signed up. The flier for the class had a link to Ham Elmer where you could download a PDF that told you the basics about getting a license.

After reading this booklet and absorbing the info like a sponge, I felt pretty confident. I started to read about ham stuff in my spare time. I learned about HF/VHF/UHF propagation and about RF safety. I found some practice tests online and started to take them. I found that I could ace the Technician test nearly every time. So I think to myself, this was pretty easy, maybe I should shoot for General. See, by now, I realized that there are three levels of licenses, each with increased privileges. I already had my sights set on Amateur Extra, but was not sure how long it would take me to get there. A few years, perhaps.

The first time I took the online General level test, I only failed by one question. It was a 35 question test, like the Technician test, only the questions were a little harder. That really got my hopes up. So I studied up some more on the questions I missed so I could understand what they were talking about. At this time, I recognized a lot of the words and phrases, but was still dredging the depths of my brain to pull of any shred of knowledge about radios and electronics I learned in college. As I read about radio wave propagation, FCC part 97, and the ham culture in general, I began to get slightly better scores. I think on the fourth try, I finally started passing the General tests regularly. I still had a week until the ham course. I was notified that they would be testing all levels and that if you pass one level, they automatically offer you the next level. Hmmmm....