Saturday, February 27, 2016

Lehigh ARKnet Site Install

Today was a big day. After nearly a year of searching for a radio site, we were finally able to move forward on the Cupertino ARKnet project, which I last blogged about last January.

The Cupertino ARKnet is a project that my friend Marcel and I decided to support with the city of Cupertino to build a point to multi-point microwave network across the city to provide resilient network connectivity between the city Emergency Operations Center (EOC) and various critical sites around the city. This network is designed to stay up in the event of a major disaster and still provide a suite of useful services, even if Internet connectivity is entirely cut off.

What has proven to be the largest challenge so far has been getting access to a site where we have line of sight for most of our sites of interest. This challenge was finally overcome when we signed a site agreement with Lehigh Southwest Cement to build a sector site on an abandoned water tower on the northern edge of their property, which is on the western edge of Cupertino.
The day started off bright and early at 8:30am. We all met up at Marcel's apartment and loaded up all the staged equipment and supplies between Marcel's car and my pickup. This radio site isn't the most difficult site to get to, but there are dirt roads involved, which are normally only used by heavy quarry equipment.
The site is an abandoned water tank on the side of the waste pile for the Permanente Quarry. Lehigh Cement wasn't able to provide us power this far from their plant, so it looks like we need to run the site off-grid.
The first order of business for the day was clearing and leveling a location for the solar panels. Lehigh was not able to provide us with power and our site agreement didn't include pouring concrete (the irony was not lost, considering that this is a cement plant), so the site is powered by a free-standing solar panel array on pavers.
Marcel did an amazing job designing and building the panel frame out of unistrut. You'll notice that we've got the panels angled unusually high. For angling solar panels, the rule of thumb is that for maximum power generation across the year you want to match your panel angle to your latitude. This is technically correct, but is only true for power generation averaged across the entire year. This is fine for grid-tied solar systems since any excess generation during the summer can be dumped onto the grid, and shortfalls in the winter can be covered by buying energy from the local utility company.
Since our system is off-grid and only has 100Ah of batteries, we're much more concerned with the minimum daily power generation (in the middle of winter) than the total available power across the whole year. During the summer, there's going to be so much power available that our battery bank is going to be fully charged half way through the morning, and then the rest of the power for the day is going to do nothing but keep the batteries topped up.  Instead of the 37 degrees elevation based on our latitude, we built the frame to hold the panels at 50 degrees elevation. Now our winter power is as high as possible, at the expense that we're leaving a bunch of power on the table during the summer, which wouldn't be put to any use anyways.
Once we got a good start on the solar panel install, I turned to the issue of mounting the access point on the top of the water tank. For our initial roll-out, we're only using a single 10MHz wide channel in the 5.8GHz unlicensed band. As our network grows and we find needs for greater bandwidth, we plan to add additional sector antennas here or at additional sector sites (the network routing has been designed with multiple sites/antennas per sector in mind).

As for the hardware up the tower, we're using a Mikrotik SXT SAr2. (Yes, it's really there; it's tiny!) This gives us a relatively wide 90 degree beam width, which for this site covers all of Cupertino with a single radio. All wisdom about deploying point-to-multi-point says that trying to cover this much of this area is going to be a bad time. Frankly, I'm going to be relatively shocked if we make it very far with just this one sector antenna, but getting to the site and adding more radios is so easy that I figured we would give this a wag and see how far it gets us. We're not looking for a huge amount of bandwidth (~5Mbps), so we can tolerate lower levels of quality than if we were trying to operate a consumer WISP.
While I was up the tower playing around with hose clamps and zip ties, the rest of the team installed the solar panels and electrical system.  The solar panels are four 80W CdTe thin film solar panels (BP Solar 980L). You might say 320W of solar panels for a single 5W router might be a little over-kill, and I wouldn't disagree with you. We are going to have a very comfortable power budget (which is going to keep our batteries really happy), and this leaves us plenty of room for growth as this site gains additional sectors, point-to-point links, etc over time without us needing to revisit the power system.

I deeply, deeply regret having gotten frameless thin film solar panels for this project. It's the timeless story: guy finds guy on Craigslist. Guy offers guy solar panels at $0.75/W. Guy gets great deal on solar panels before entirely appreciating what a pain it is sourcing 6mm frameless panel clamps.  Getting the edge clamps for these panels to mount them to the unistrut was a huge pain, and I'm never dealing with it again.
The electrical cabinet for this site was graciously donated to us by the Cupertino maintenance department (synergistically transferred, really?), and again is set up for growth. The bottom shelf holds two 100Ah 12V deep cycle lead-acid batteries, wired in series to make a 100Ah 24V bank for the solar charge controller.

The middle shelf holds an EPSolar Tracer 2215BN solar charge controller, a 24V-12V DC-DC regulator to provide some 12V power for the network switch and fan, and an unmanaged workgroup switch with a PoE injector for the access point on the tower.  The solar controller warrants some particular attention: this is by far the least expensive solar controller I've seen which actually uses Maximum Power Point Tracking (MPPT), which is a big deal. Lots of $20 charge controllers on eBay will claim that they are MPPT, but they simply aren't. MPPT means that the controller is going to make an effort to hold the panel array at the correct voltage/current to extract the maximum amount of power available from it given the current solar conditions, which isn't a trivial task since this magic point moves throughout the day based on the amount of sunlight and temperature, and the fact that the panels are wired as an 80V array while trying to charge a 24V battery bank. This takes a serious DC-DC buck converter, which is why MPPT controllers need such a beefy heat sink compared to the cheaper PWM controllers.

The top shelf is currently mostly empty, waiting for more equipment or a second battery bank. The only thing there now is an MT-50 control head for the solar controller. This is another feature of the EPSolar Tracer series controllers that I absolutely love: their user interface is over RS-485 MODBUS, so you can mount your controller as close as possible to your batteriy bank and load, and all you need to do is run CAT-5e to wherever you want your nice user interface to the controller. The control head lets you set the battery charge mode, etc, as well as review all the collected statistics like current panel/battery/load voltage/current and cumulative power generated/consumed in kWh.

SHAMELESS PLUG: I'm giving a talk on solar panels and designing these sorts of solar power systems next month in San Jose on April 13th, 2016 at the West Valley Amateur Radio Association. If you're in the Silicon Valley and interested, I encourage you to come see.
Last points of order for the day were fit and finish on the cabling and adding weights to the array frame.
I will freely admit that it is possible that two T-posts, three cinder blocks, and 20 sandbags are maybe overkill for keeping this panel array from blowing away, but we really don't want it to blow away, and the sandbags were free (thanks city of Cupertino!). In an ideal world, we'd have poured concrete and/or had a much better idea what our worst case weather conditions would be on this hill. Barring both of those, we decided to just make a good wag at "really heavy."
As for the question of how well the site is working, that's a question I can't answer yet. The next step in the project now that we have the first access point up is deploying client sites to connect to this one. The first 90% of the work is done, so now we just need to get the next 90% done and see where it takes us.

Of course, a huge thanks again to our great team of volunteers, the city of Cupertino for supporting us on this project, and a HUGE thanks to Lehigh Southwest Cement for entertaining some random group of volunteers setting up some equipment on their property. The Cupertino ARKnet wouldn't be possible without everyone's help.

(Thanks to Marcel AI6MS and Jim KN6PE for letting me use their photos in this blog post)

Tuesday, February 23, 2016

Thursday, February 18, 2016

UHF RICK Repeater with Auto ID and Teardown

I had previously mentioned that the RICK doesn't meet FCC requirements on its own due to its lack of automatic identification. What it does have is an accessory port where you can plug in some other device which can generate the ID for you. In this case, I used an Argent Data simplex repeater controller with the actual repeating feature turned off. (I covered using it as a simplex repeater previously)


Things I missed in the video:

  • The CallAlert signalling on the MaxTrac isn't a built-in feature. You need an optional DTMF decoder board which I was recently gifted by one of my friends. It's a relatively rare part, and I should have emphasized that more.
  • Even though the simplex repeat feature is turned off on the ADS-SR1, it does still retain all of its other features like voicemail and stored voice beacons. This is actually a remarkably featureful repeater now, considering it's built around a RICK.

Tuesday, February 16, 2016

Sandpaper Cutting Jig

I was out working in my father's woodshop this evening, and realized that I've never written about this simple tool that I use practically every time I'm using sandpaper for a project.  It's a simple jig for tearing sandpaper into strips that are the correct size for half sheet and quarter sheet electric sanders.
Sandpaper comes in sheaves of 9"x11" sheets, and many electric sanders are designed to accept either halves or quarters of these standard sheets. This jig consists of a 1/4" piece of plywood nailed to two pieces of 1x2 as feet (shown in the second photo), with three lines drawn on the top and a hacksaw blade screwed down with some shims underneath the screws.

The hacksaw blade is shimmed up with very thin pieces of wood just enough that you can easily slide coarse sandpaper underneath the blade. The teeth are pointed out, or to the right in the first photo.

The first line is drawn 4.5" away from the cutting edge of the blade, and is used to place the sandpaper so you can tear it into two parts longwise.
The second vertical line is drawn 5.5" away from the blade, so the halves can be easily quartered for the smaller electric palm sanders. Here's a photo showing how I fold the sandpaper over before tearing it against the hacksaw teeth.

The third line is drawn perpendicular to the blade so I can easily tear off odd-sized rectangles while keeping the cut square to the sheet. If I'm only doing a small amount of touch-up work, I'll only tear off a gum stick sized piece. If I later pick up the odd-sized leftover and want to use it in my palm sander, all I need to do is line it up with the 5.5" line and tear off whatever's left.

The pencil lines aren't ideal, and tend to wear off after heavy use. Making more permanent markings with a deep cut + black ink or burning the lines with a soldering iron or wood burning pencil would be a possible improvement if you make one yourself.

Saturday, February 13, 2016

I Got a New Callsign! WQXE668

As you likely know from reading my blog, I'm an active and very dedicated amateur radio operator (under the callsign W6KWF). Amateur radio has been a huge educational experience giving me opportunities to learn about RF communications, DC power systems, OSHA tower climbing, event and crisis management, the list goes on.  The amateur venue is an absolutely huge venue for exploring the facets that you're interested in, and I will never discourage someone from at least getting their technician level license (Link to ARRL site)

One of the tenets of the amateur radio license is in its name: it is a license specifically designed for interested individuals who may not be paid or compensated for their work using this license. There are tons of advantages to this limitation, and I will always adamantly defend the unpaid nature of amateur radio activities.

That being said, there comes a point when I can no longer work within the limitations of the amateur ticket, so I decided to spend the time and money and get myself a part 90 commercial license, which was just granted to me this week! WQXE668 (It doesn't really roll off the tongue, does it?)


Let us start with the what. The part 97 amateur radio licenses granted me the privileges to operate radio stations under my control on lots of little slices of frequencies. A little around 4MHz, a little around 7MHz, a little around 146MHz, a little around 440MHz, etc. As I passed the tests for higher level licenses (technician to general to extra) the FCC allowed me access to larger slices of frequencies to do with as I pleased.

This new part 90 license is a "commercial itinerant" license, which lists a specific set of frequencies and modes which I am allowed to use in a designated area. Being a commercial license means these privileges don't come with the strings attached preventing me from getting paid. Being itinerant means I'm limited to a subset of the business pool frequencies which are uncoordinated, so the FCC makes no guarantees that I won't have to deal with other stations on the same frequencies. I opted to get some frequencies in the VHF highband around 150MHz, some up in the UHF band around 460MHz, and even some VHF low-band frequencies around 30MHz, because who knows which ones I'll ever want?

This license also no longer only covers me. I am ultimately legally responsible for this license, but when I applied for it, I asked to be licensed for two repeaters and 500 mobile stations on every repeater pair. 500. This license doesn't just cover me, but myself and 499 of my closest friends.


It's not that I mind volunteering my time on weekends providing communications support to events, but there's some problems with trying to provide a strictly amateur communications network for an event:

  • Everyone HAS to be volunteers. It gets hard getting enough volunteers when the deployments aren't pleasant or convenient. Using a commercial license, payment is now an option for event staff. I've been paid as much as $1400 for working a weekend as a communications volunteer, and that's specifically disallowed using my W6KWF license.
  • Everyone HAS to be licensed. The amateur radio license isn't hard. It's 35 multiple choice questions. The thing is, it's a barrier that limits who can pick up a radio and talk into it. Using a commercial license frees us from having to have two sets of volunteers; those who need to run the radios, and those who need to run the event. It is a common complaint from event organizers that amateurs show up to play with their radios and little else. With a commercial license, we can now hand radios to our regular volunteers, and communications doesn't need to be the focus of their responsibilities.
This second point can be controversial. There are those who will argue that hams have spent more time practicing using radios and passing information through them, so hams should be more effective operators of the radio than some random volunteer who has been given a 20 minute introduction to which button to press and which part to point up.  I'll agree that there are some rare instances where this is true, but comparing hams running their weekly practice nets where they are completely unable to handle anything unexpected vs total novices figuring it out during event setup, I won't back up hams as the superior communications force.


Getting my part 90 license wasn't prohibitively hard, but after getting it, I appreciate why most people opt to use third party licensing firms who will fill out all the paperwork and deal with the FCC for you. They cost a little more money, and save a lot of time, but in the end you end up with the same license.

I instead opted to do the research myself, figuring out what the different station codes and modulation codes mean, and which frequencies I can pick from, and what forms I need to fill out. I figure I spent about 10 hours researching how to fill out the 601 license application form, two hours filling it out, and $165 to turn the crank.

$165 and two hours to fill out a form on a horrendous Java application. I was able to do it during my lunch break at work, with no test, and after a day of engineering review the FCC granted me the license less than 48 hours after I pressed submit.

Before you ask, I've thought long and hard about offering my assistance or posting a detailed blog post on exactly how to get a part 90 itinerant license, and I've decided to not get into that at this point for a number of reasons. There is a lot of ignorance coming from hams in the forums about getting part 90 licenses, and the vast majority of it has proven to be false, but I don't feel that I'm yet qualified to try and refute it.

I am also always interested in any special events you're involved with in Northern California which need either paid or volunteer communications support. My docket for this spring is just about full, but I'll always consider it, and have some friends to whom I would gladly pass the info.