Category Archives: Wireless General

And while I’m at it

Last week I had the pleasure to spend in far-south Chicagoland, where it started out 48 °F and raining and ended up 18 °F with black ice everywhere. Not immediately, but once the ice formed, it stayed in place the rest of my visit. Made for some dicey walking.

However, my buddies at the RR, like the post office, work rain or shine, ice or sleet, snow or sand, and were busy installing my hoped-for array of antennas on a homebrew rack up on the roof.

Little hard to see in the photos, but it’s basically a triangular array of 3 tripod mounts held down with a bunch of concrete blocks, then two-sided unistrut forming two vertically spaced equal equilateral triangles, upon which it’s easy to set vertical pipes to attach antennas.

Right now the lab I’m helping to build (in the building below) needs far better cellular connections for the industrial modems that we’re testing, so the antennas on the roof will solve a lot of our mysterious connectivity problems.

The lab also needs a solid GPS antenna on the roof – I have a rack-mounted 8-way GPS splitter inside and I’ll feed one antenna to multiple devices in the lab that need GPS.

The runs from the antennas on the roof to the rack are all 1/2″ superflex, and we’ve got grounded lightning protectors at the rack and shield grounds just before the coaxes penetrate the building. We’re also way lower than many better lightning targets all around us, so we’re probably as safe as we can be.

Next step is to head back there and start assembling some LMR240 jumper cables to run from the rack connections to the final resting places for the signals received.

It’s fun working on the railroad.

Update on the rooftop amp

Last time we visited the roof, the amp followed by the FM BCB notch filter was now in the die-cast enclosure, but not actually attached to anything.  Now it finally has a home, at least for now, on the tripod leg. It required a visit to Artie’s Ace Hardware in Phoenix at Tatum and Thunderbird, which until about 8 hours ago was unknown to me as a purveyor of a near infinite number of different kinds of metric fastener! Only 4 miles away, it’s a treasure to know that I can get an M4x8 mm pan head screw even late in the afternoon.

The metric hardware was required to install the steel mounting ears on the die-cast enclosure; those mounting ears accept the muffler clamps that hold the whole thing to the leg of the tripod. Later on this winter I’ll bend up some 0.032 Al sheet to act as a sun shield and remount the box on the north leg with the shield to keep it cooler during the summer. I still need to do something permanent about the power for the amp, it’s currently the solar power setup I made a couple weeks ago.

Left is input, right is output. Runs on any voltage up to about 32 vdc and down to about 7 vdc. The internal dc-dc converter keeps the amp supplied with an even 5.0 volts.

With this amp in place, my stack’o-scanners is just bangin’ along. I’ve got great reception, and no FM BCB interference. And, there’s space in the enclosure for a future Arduino or Raspberry Pi, as well as the necessary network connection.

Shocking new amplifier

Is finally built. I bought three of these a couple years ago from kuyaya520 on eBay and they’ve languished since then, heat-shrink protected and tie-wrapped in place, like for the truck’s half-deaf GRE PSR-600 scanner.

Finally put one in my new die-cast case that I got 10 of last month, and used a 82 ohm resistor to set the operating voltage to around 10 vdc when running off 13.8 vdc. According to the eBay page about the amp, its best gain and noise figure is around 9-10 vdc.

Checked out the gain, and it’s pert darn near what the vendor says it is. Don’t have a simple way to do noise figure. Need to get myself an ENR noise diode so I can do y-factor.

This amp will likely go into the truck to replace the tie-wrapped kludge… I’m starting to get reasonably good at assembling these things.

Next step on the rooftop LNA setup

This past weekend I finally started building the ultimate case to house the LNA and FM BCB filter for the rooftop multireceiver project.

Last night I did the final bit of wiring, installed a DC-DC buck converter to take +12 vdc and knock it down to 5.0 vdc.

Here’s some pics of the project.

The two separate die-cast enclosures are the LNA (lower) and the FM BCB notch filter (upper). There’s a LM2596 DC-DC converter in the lower left, and a weathertight Ethernet connection in the center-right wall. All external RF connectors are N. All internal connectors are TNC. All coax is RG316 double-shielded. I used an Ethernet connection to get power to the box and to allow the future addition of either an Arduino or an Raspberry Pi for telemetry purposes.

The overall enclosure with installed components. Got this particular enclosure for about $22 delivered – someone in Santa Maria CA didn’t want it. Was missing the base plate upon which I mounted all the components – fortunately, I had a piece of Al in the garage that was a near-perfect fit! Would have cost nearly $70 new.

The left N connector is the antenna input, the right N is the assembly output to the shack. The Ethernet connector is for future expansion and dc power.

Installed on the roof temporarily (will be mounted on the tripod to right ultimately) with power supplied by batteries in the Tupperware container.

The batteries (Eneloop AA x 10) are charged with a newly modified solar panel install. Again, over the weekend I cut some Al extrusions to replace the old way I’d attached a single 5 w solar panel, now it supports two 5 w panels for a total of 10 w. This almost guarantees sufficient charge for long winter nights.

In addition, the box mounted on the tripod already had a PoE Ethernet connection from the main rooftop unit. I use that 12.6 volt PoE  through a single 1N4001 rectifier to source power to the LNA box when the solar panels can’t provide enough charge to keep the batteries up. I want to add some telemetry (through a future Arduino or similar on the roof) to measure voltages, temperatures, etc.

 

Scanners set up for monitoring/tracking aircraft

I un-mothballed a number of my old trusty-rusty Radio Shack PRO-2052 scanners for monitoring aircraft operations here in the valley.

With the new VHF/UHF multireceiver antenna setup, it’s very easy to have a number of scanners all running in parallel so that I don’t miss as many conversations and handoffs.

Here’s the stack of scanners: the top is ZAB (Albuquerque Center); the middle is Phoenix area TRACON; the bottom has both KSDL (Scottsdale airport) and KPHX (Phoenix Sky Harbor airport) in there so that I can monitor either or both.

I put different color LEDs for the display backlights. Yellow is top; orange is middle; red is bottom.

10 MHz bandpass filter from China

Saw this 8 to 11 MHz band pass filter (item number: 201406314462) on eBay a few weeks ago and thought it might come in handy to help my SDR radios hear WWV and WWVB while not being overwhelmed by other signals.

Here’s what the 1 to 100 MHz band looks like using the PCR-1000 connected through the new antenna multicoupler, without the new filter. Remember, this antenna setup already has some significant attenuation below about 100 MHz since it’s using a VHF/UHF discone and the 10 to 2000 MHz LNA.

Here’s a plot using the ICOM PCR-1000 using the new BPF. Indeed, it has good performance, especially for the US$11.48 incl shipping.

My very first wardriving card!

I got all reminiscy while digging through a box of stuff that was 14 years old. Found the Orinoco Gold Wi-Fi card that was the heart of my first wardriving setup. Smokin’!

In 2002, a few of us at Motorola SPS RF/IF Products (or was it Radio Products?) were fortunate enough to acquire the Lucent Orinoco Gold cards. We experimented with ad-hoc, infrastructure, all at the amazing speeds of 11 Mbps in the 2.4 GHz band. Darren, Dave and I had the cards. Long before Moto even had employee Wi-Fi in its buildings.

Here at my main site, there’s some scattered monthly summaries of how Wi-Fi was slowly taking off in Phoenix. I mapped them each month in an effort to convince our management that Wi-Fi was growing extremely fast, and that we needed to address the Wi-Fi chipset space. Sadly, we never got our act together, not as Moto and not as Freescale.

One weird trick for making the amp behave

Alright. Things are looking much better again. Moved the LNA to its rightful position just 2 m of LMR-195 behind the antenna. Put the FM BCB band stop filter behind the LNA. Since I’m not sending dc up the coax right now, and since the BCB stop filter is in the way anyway, I bit the bullet and built myself a quick and dirty solar charging battery supply for the LNA!

5 w solar panel, purchased a decade ago from Harbor Freight; 8 NiMH AA cells in a series holder; LM2596 buck converter to reduce the battery voltage to 5.0 v; a Tupperware container to hold the batteries and converter. Impressive, no? %^) Let’s see how it survives the night.

Here’s the new block diagram – note the PCR-1000 is on one leg of the first splitter, so it should have no more than about 4 dB additional loss than when directly connected to the coax from the roof.

001 – 100 MHz, w/LNA, w/filter, w/o-3dB-splitter:

001 – 100 MHz, w/LNA, w/filter, w-3dB-splitter:

Here, the added loss from the splitter is apparent from DC to 80 MHz or so. It apparently doesn’t pass low frequencies well at all. Since the antenna is not rated that low anyway, it’s good to get rid of additional interfering signal…

100 – 200 MHz, w/LNA, w/filter, w/o-3dB-splitter:

100 – 200 MHz, w/LNA, w/filter, w-3dB-splitter:

It seems that the splitter has greater than 3 dB additional loss until up around 140 MHz. The aviation band (118 – 136 MHz) is about 7 dB worse than without the splitter. But that’s it. No other weirdness. I can live with this.

Am much more satisfied now. LNA is directly behind antenna. Have a new experiment to see how solar battery charging works out.