Repeater work on Sandia Crest

I had the opportunity of a lifetime to traverse through the nation's most RF dense mountaintop towersite, and possibly reduce my chances of having children by a large amount...in any case, today's work was bucket loads of fun.

Towers lining the crest. [Wikimedia user Skoch3, Photo]

The work at the site was simple -- some regular maintenance to the W5MPZ D-STAR repeater and gateway.

So, I got up early and headed off to Ed's (KA8JMW) place to pick up the caravan to the peak. We packed the truck with some server rack shelves and tools, and headed to pick up Brian (N5ZGT), then Chris (NB5T).

And then, the 10,768 ft (3,255m) summit.

The road was blocked by the Forest Service since the park was closed due to fire danger. Thanks to some prior planning, we had no trouble getting past.

And not two turns in to the curvy mountain road, we meet our first deer, head on. Thanks to Ed's quick foot on the break (maybe he was practicing for QLF?) the deer zipped across the road, perhaps only with a bruised tail.

We were warned that with the lack of humans, nature tends to take over a bit

The one thing I though of going up the road is, what if you had this road all to yourself (like we did then) with a nice, fast rally car?

I think deer would have a problem with that.

Anyway, we got to the top, and met the first obstacle:

Chris dispatched the lock on the well-signed gate and we were in. At that point, we had entered the danger zone; the steel forest. With at least 26 FM stations, almost half being over 20 kilowatts, 33 TV stations, more than half over 100 kW, and an uncountable number of microwave dishes, log periodics, yagis, verticals, radomes, funny looking phased arrays and dipoles supported on dozens of massive towers, I swear I could hear KOB in my teeth.

After driving through the entire site, we arrived at our final destination: the Sandia Nat'l Lab's personal radio  playhouse.

The guys began working on equipment, while I snapped photos and gazed in awe of the city of Albuquerque all within my field of view.

Chris, Ed, and Brian "working."

Brian took the job of tightening the D-STAR antenna, which he did adamantly, without falling, thanks to his fancy harness. It's funny how dinky that antenna seems, but being over 3,000 ft ( 914m) above the rest of the world, it can see almost 100 radio miles (150km). With my 40w mobile radio, it comes in full signal in Socorro, NM, 75 miles (50km) away.

The team was successful of getting things done, cleaning up the shelves of an obtrusive monitor, keyboard and mouse (by going SSH only) and installing a NetIO internet-controlled AC power killswitch.

Before...

After. Notice the new black box on the top right. That controls power for the whole thing via the web. 

The work was complete right on the dong of noon, and we had ribs for lunch. YUM! After that, Chris's wife treated us to some homemade ice cream at his place, and we toured his shack, nestled on the edge of a HOA-restricted subdivision. That doesn't stop him from loving ham radio!

Next on the list is to move this stuff to its permanent home on server racks. Sadly, I won't be here, with only two weeks left in my VLA internship. I don't wanna leave! :(

I would like to thank Ed James KA8JMW, Chris Aas NB5T and last but not least, Brian Mileshosky N5ZGT for taking me on this mighty heighty outing. Perfect timing for knocking another thing off my New Mexico to-do list.

The only part I forgot on that list was to bring a spectrum analyzer up there. It would have probably blown up in my hands.

Me, Ed, Chris and Brian on the edge of the crest. 

Don't play Ingress at Radio Observatories

A few weeks ago, the IPG got some curious email from some ABQ-ians asking if they could play Ingress at the VLA to capture some GPS-based portals. If you've never heard of Ingress, think of it as geocaching with a Virtual Reality spin. Check out their website here.

Ingress is played on smart devices, which require data connections to operate. These data connections are fine and dandy unless you're at the world's greatest radio observatory; here they aren't so dandy.

RF-EMS

Below is a screencap of our RF-EMS (Radio Frequency-Environmental Monitoring System) which captured two WiFi access points (the darker blotches) from an RV containing a Verizon 4G hotspot and another router for something else.

Your VLA on Wifi

In the last blog I described the 10' dish for pinpointing RFI. We also have a (usually) 24/7 monitor that uses some pretty nifty antennas and preamps on a 50' tower, sending it to an HP 70000 Spectrum Analyzer in a RF-shielded room from which we can record and upload plots like the one above, every day for the past 5+ years. 

RF-EMS and Bunker

The biggest downfall is adequate locating of interfering transmitters. Currently, I'm designing a method which will allow the IPG to quickly and accurately pinpoint people with any kind of transmitter, be it a cell phone, hotspot, or vehicle keyfob (if we wanted to locate such things). My idea is based on multilateriation, which uses multiple receivers around the site which compare arrival times to calculate a four dimensional location. Keeping the bill of materials as low as possible, simplicity, ease-of-use and network integration (without causing RFI itself) a prime focus.

It may be overkill, but it gives me something to do in the free time.

Other Doin's: Testing out and Debugging the 74 MHz System

When I'm not having free time, this is what I'm doing. A new feature of the Expanded-VLA is observations on the 4 meter band. The current system in place uses these simple crossed dipoles hoisted a few meters below the sub-reflector.

Installing the 74 MHz Crossed Dipoles

The cross dipoles connect to our receiver, which hooks up to the rack that magically digitizes the signal and turns it into pulses of light which the correlator feeds upon.

One of the problems we face are things broken that don't have to do with our antennas and receivers. For example, the first test we do to examine the receivers performance is a band pass plot. Often times, we see something like this:

A bad bandpass plot caused by a faulty relay in the T301.

This is ugly! What we want to see is this:

A beautiful but RFI-ridden bandpass! You can see 4 band on the left, and P-band in the middle with RFI spikes all over.

First we go digging in the LO-IF and FE racks for a place to stick a spectrum analyzer to...

Eric the BAMF next to the LOIF and FE rack. Our culprit is on the left, in the middle of the top rack of modules

And from that we figure its' this T301 which does the first IF up-conversion from 0-1GHz to 1-2GHz.

The faulty module in question

We get a new one, stick it in, turn it on and voila, it's alive!