There's a Hole at the Bottom of the Sea...

So... to have a Rohn 25G based tower be self supporting, you have to pour a very substantial footing.  With 25G, you can go up to 40ft in a self supporting configuration, and I really hate guy wires.  On the other hand, a footing for a self supporting 25G tower is 4'x4'x4'.  Initially, this didn't sound like a big deal.  Four feet just doesn't seem like that much in theory.  In practice, 2.5 cubic yards of dirt takes a lot of time to dig by hand.

Scott in the hole -- "This has gotta be 4 ft!"

I started the hole a couple of weeks ago, and got about 2.5 ft down into the ground.  It was disheartening when I first measured the depth thinking it was around 4 ft, and I was barely half way done.  My friends Scott and Chris helped me on Sunday with some of the digging and we made some pretty substantial progress.  There are a couple of problems with such an endeavor.  First, it's hard to maneuver in such a small hole.  Make sure you have short tools or small people to dig (child labor!).  Second is just the difficulties of getting a 6' 230lb guy into and out of the hole to dig.  Luckily I only have to do this once.

So, I'm hoping that I can get the hole dug in the next week or so, and we can get things prepped for a pour.

The other progress that I made is obtaining the rebar for the footing.  Unfortunately, Rohn calls for #7 rebar, which is 7/8" in diameter.  Nobody around Corvallis stocks this, because it's fairly large stuff.  I ended up getting the rebar from Farwest Steel in Eugene.  It was around $75 for 18 pieces of 4' #7 rebar.  Not too bad for 150 lbs of steel.

Partially painted tower section

I also went up to Seattle to pick up the rest of the tower sections from the MicroHAMS guys.  They have graciously donated 4 sections of Rohn 25G that they had laying around.  I'm very grateful to them for their generous donation.  They required a bit of cleanup, and I got them hosed down and scrubbed off a bit.  They still need to get some attention from Scotchbrite and painted.  I have one of the sections almost done, and after I finish the hole I'll work on the rest.  Rodda paint in Salem had some aviation white tower steel paint.  The specification sheet is here:  http://www.roddapaint.com/professional/product-data/31114.aspx  They had it in stock in Salem, so give them a call if you need some.  Notice they have Aviation Orange as well if you need to paint up your tower to be FAA compliant.  It's not exactly cheap at $60 a gallon, but I want to get things done correctly as possible the first time.

Scott also cut down the bottom section that I purchased from a guy in Corvallis.  This is going to be the section that's embedded in the concrete pad.  I don't have any details on the cutting process, but he said he just used an angle grinder.  It's good to have friends to help you out with the physical labor and construction processes.

The receive antenna is on order as well, and should be shipped in a week or so.  I'm also waiting on my Tait T800 supplier to finish reconditioning the repeater.  I'm hoping to head to Boise next week to pick that thing up.  The ORRC is going to meet on August 8th in LaGrande, so I plan on trying to be there to answer any questions with our application for coordination.

So, things are progressing, but always more slowly than one would want.  Things are coming together, and I'm hoping to have the repeater operational sometime in September before monsoon season starts.

Finishing Touches on the Computer

6-pin Mini-DIN connectors in the back panel

I just finished up the configuration for the computer to make it clean looking.  The last bit of work that I intended to do on it was to mount some 6-pin mini-DIN connectors to the rear of the case that plugged into the node adapters.  This way I could keep the case sealed and not have any ugly pig tails hanging off of them.  I purchased some bulkhead connectors from DigiKey (I got an excess of them to save on the outrageous shipping charges, so if people need a couple for one of their projects, I have like 8 left).  The part number is: CP-2860-ND.  They were all of $1.56 apiece, but I ordered 10 of them just to have a round number.  I'm figuring I can rework my APRS Digi computer to use a couple of the connectors as well.

External view of the Mini-DINs

It works out fairly well so far.  I currently have stolen the Kenwood TM-271A off of my APRS Digi setup to be a radio for the D-STAR hotspot.  I'll put CRVLS back on the air as soon as I finish playing with the D-STAR stuff.  I've constructed a cable with a 10µF capacitor in series with the receiver's output to take the DC offset off of the line.  I don't know if the Tait repeater is going to require it or not, so I've held off on building it into the connector on the back of the computer.  If it does, I'll probably solder it internally to the case.  The hotspot is currently on 146.45MHz here in Corvallis and I've kept it linked to REF010 C to talk to some of my friends back in New England.  It's performing fairly well for what it is.  I'm running Scott's (KI4LKF) Linux based repeater software with relatively little problems.  I actually had more issues running the Windows hotspot software.  I think there are still some USB issues with Satoshi's v7 board that rear their ugly head with newer motherboards such as mine.  I may try out one of the alternative boards next go around for the 2m side of the repeater.

The TX Antenna Arrived!

I got the TX side antenna from Telewave.  It's a ANT450D6-9 which should give around 9 dBd gain.  I can't wait to get it up in the air, but it'll be a while before we can get a proper tower erected to test it out.

The Repeater Controller

The repeater controller is pretty much built.  I am waiting with baited breath on the release of David Lake's (G4ULF) D-STAR repeater software.  Supposedly it is in the hands of the K5TIT trust group to package up for distribution to the masses and its release is imminent.

Hardware

Front view of the controller

The system is based around a 2U 19" rack mount case.  While a 1U case would be smaller and take up less space in the rack there is a major reason for using 2U.  A 1U case requires the use of special fans that are shorter than the normal fans that ship with processors.  Many times these fans don't cool as well as the stock coolers due to poor airflow around a small 1U case.  For this reason, it tends to be much better to build systems like this in a 2U case where you can use a normal fan.

PicoPSU 12V ATX Supply

As I mentioned in an earlier post, it made sense to me to try to build this system based on 12VDC rather than a 110VDC.  The RF gear is going to run on 12VDC, and if I standardize on this I can use standard batteries, power supplies, and chargers to make sure that emergency power is readily available.  I used a PicoPSU to provide the 12VDC to the computer.  This is a 150W supply that plugs directly into the ATX connector on a motherboard and takes in 12VDC.

Anderson Power Poles in place of the 120V connector

I modified the cabling a bit on the PicoPSU to have Anderson Power Poles instead of the Molex connector that was on them originally.  This just required a little bit of crimping and soldering.  I also removed the 110VAC connector on the back of the case and inserted a panel mount power pole connector that I picked up at SeaPac from DC Power from Portland.  I'm actually very happy with the setup, although I'm a little bit worried about cables getting pulled out from the back.  We'll see how it works out when it gets its permanent place in the rack.

Satoshi Node Adapter moounted in the case

The modification for 12VDC power allowed me to remove the power supply from the case.  This is going to help with cooling inside the case and also allowed me quite a bit of free space inside.  I chose to use this extra space to mount the Satoshi Node Adapter internal to the case so that it wouldn't look like a bag on the side of the controller.  I purchased a V7 node adapter from Satoshi.  Originally I ordered it in the case and fully assembled because I didn't quite know how I was going to work with things.  I ended up taking it out of the case and using some JB Weld to mount it to some threaded posts.  This should also allow two node adapters to be stacked one on top of another in the case with plenty of clearance.  This will be useful for having a controller that can handle both 440MHz and 2m at the same time.

Front panel USB connector hacked to a USB-A for the node adapter

To clean things up a bit with cabling, I took a USB A header that connected to the motherboard and cut it up to have a USB B plug on it.  I soldered the proper pins and reconstructed the cable.  It connects into one of the motherboard headers provided for front panel USB connections.  This particular header had room for two USB connections on it, and I'm leaving one available for the second node adapter when it's installed.  This makes the cabling a lot cleaner.

Node Adapter LEDs brought to the front panel

I also removed the LEDs from the node adapter board and moved them out to the front panel of the computer so that I can monitor the status of the PTT and COS detection of the node adapter.  Some hot glue on the back of the LED mountings keep them in place.  I still need to grab a couple of 6-pin DIN sockets from Mouser or DigiKey so that I can bring out the radio connections to the rear panel of the computer.

Internal view of the machine

The motherboard is an Intel DH55HC with a Core i3 processor on it.  I chose this setup because the new Core processors are getting a reputation for having very low power consumption for the amount of computing you get out of them.  More importantly the Core i3 has an on-die GPU which both saves power and saves space in a 1U case. The motherboard has onboard ethernet, and I've loaded it up with 2Gb of DDR3 memory.  This should be more than sufficient for a D-STAR controller.

To further reduce power consumption, I decided to put in a solid state drive.  I chose a 64Gb V+ model from Kingston that I picked up at Fry's.  Unfortunately, there was a defective SATA connection that broke when I tried to change out the SATA cable.  It's been returned to Kingston for replacement, and I hope to get it back sometime next week for re-installation.

Rear view

All of this work has resulted in a clean looking installation and has reduced power consumption to about 5A peak at 12VDC.  This is about 60W maximum power consumption.  The machine averages around 2A current draw in normal usage.  This is very good for a full x86 processor such as the Core i3.  I could have gone with one of the Atom systems, but I had doubts that it would be powerful enough to handle the gateway tasks required of the D-STAR stack.

Software

I'm using the CentOS Linux operating system because it seems to be the distribution that most of the D-STAR folks are used to.  This is because Icom has chosen to use it as the only supported distribution for their gateway software.  I'm not particularly fond of CentOS because I've been bitten by RPMs entirely too many times over the years.  Yum seems to solve many of these problems, though, and I will be exploring the distribution to see what I really think.  I'd honestly rather have a Gentoo distribution so that I could cut down on the amount of software on the box.

Until David comes out with his software, I'm using the r2g2_p and rptr software that Scott (KI4LKF) wrote, and that the Dutch Star people are continuing to distribute.  This allows me to run the repeater as a  hotspot and connect to various reflectors until I can become a "real" repeater on the system.  Scott's software does the RF repeater duties, and the big things that are lost in this setup is the callsign routing capabilities of D-STAR.  It does give me an opportunity to check out the RF side and get things tested before adding new software to it.

The KF7LDG Repeater Project

This January I purchased an Icom ID-880H from Ham Radio Outlet in New Hampshire because there was a good penetration of D-STAR users in the Connecticut and Western Massachusetts areas.  I ended up having a lot of fun with the mode, and worked it a lot in the car, and even chatted with D-STAR folks in Dayton.  Unfortunately, upon moving back to Corvallis I found out that the nearest D-STAR repeater was up on Mt. Hebo (W7GC operated by the Oregon Coast Repeater Group) and wasn't able to be accessed from a mobile in Corvallis.

This caused me thinking about how to solve this problem.  After considering a few different options, including setting up a DVAR Hotspot, I decided to set up a full blown D-STAR repeater at my employer's datacenter in Corvallis.  I didn't want to purchase the Icom stack because of the expense and the lack of experimentation potential.  I talked to David Lake a bit while I was in Dayton about his D-STAR repeater software.  This led me to the conclusion that I should wait for his software, and build the repeater based on a standard PC.

Even though a standard PC has some flexibility, there are some downsides as compared to a dedicated controller, and I decided that I should try to make a low power consumption PC that could run on 12VDC. I also wanted to get rid of as many rotating parts as possible, mainly the disk drive.

After that, my repeater experience is really limited, so I embarked on a process to learn as much as I could about repeater design and implementation.  I think the main thing that I learned is that repeater components are expensive, and it's the parts you least expect (like the duplexer and feedline) that can be the significant drivers of cost.

I made the decision to use the Tait T800 series 1 repeater for the RF gear because David was using it, it was nicely 19" rack mountable, and seemed to be cheaply available on the used market.  I met a guy from Idaho at the SeaPac convention in Seaside, OR that had a stack of them for sale, and I made arrangements to purchase a rack of equipment that had both 440 MHz and 2m repeaters in them.  I'm still waiting for him to complete the cleanup and refurbishing on the unit, and I'll go to Boise and pick it up.

After repeatedly seeing their ads in QST and researching them on their web site, I chose Telewave to provide the antennas and duplexer for the project.  I'm going to be using a 2-bay folded dipole at the top of the tower for receive, and a 4-bay folded dipole 10 ft. below the receive antenna for transmit.

The antennas will be on a Rohn 25G tower in a self supporting configuration at 40' tall.  Because of our proximity to the Corvallis Airport, 45' is around the maximum height we can support without notifying the FAA and FCC and going through that process.  If things work, and it seems necessary to increase coverage, we'll look at maybe adding some more sections to the tower.

I formed a club with a few friends of mine that are interested in Ham radio and digital communications.  We obtained the callsign KF7LDG for the Willamette Valley Digital Radio Association to support the repeater project.  I've applied for coordination from the Oregon Regional Relay Council, and we'll see what frequency we get.  That's the primary thing that's holding up the duplexer order.

Throughout the project, I'll be posting pictures and updates so that people can see what's going on, and hopefully the information can help out others trying to complete similar projects.