Category Archives: Land Mobile Radio

Summiting White Tank East (radio site visit) 14APR18

For the White Tank peaks, I’m lazy. I can get the key and drive. This morning I went up to check on the radio site on the east ridge where I have an ADS-B receiver and a railroad data receiver setup. The Windows PC there had apparently died a while back, the ADS-B link failed at the beginning of April, so it was time to fix things.

Time-lapse video of the drive between I-10 Verrado offramp to and from the peak

The cool thing about the White Tank road is it goes through the old Caterpillar proving grounds, where they pitted Caterpillar bulldozers against the mountain. And the White Tank road was part of the testing arena.

Verrado’s north end currently ends at the golf course; the tower road is the wide diagonal that heads northwest into the narrows up-canyon.

While Verrado continues to inch its way up the lower portions of the road, it’s unlikely it’ll ever get up this far. This what I call “the bowl”, where Caterpillar dozers not only moved millions of tons of rock back and forth for test and fun, but also cut the 20%-grade, ~0.6 mile long ramp that climbs north out of the bowl and then descends into the White Tank park boundaries.

On this fine day, there’s plenty of people walking the ramp. It’s windy as heck out, and the temperatures are in the mid-50’s, but the sun is warm.

Hauled out the dead PC. Am rebuilding it now to put back on the hill in the next week or two.


Summiting Table Top 10MAR18

4375′ elevation – clean prominence: 2333′ – isolation: 31.3 mi

GPS log available at peakbagger link above.

Time-lapse video of drive off pavement

Kind of clandestine wireless communications site – off-grid

From the parking lot, Woolsey’s in-between the two saguaros. There was one other vehicle in the lot.

Trail register.

Timber at the top of the ascent trail. This is the SE end of the mesa.

A solar powered radio facility! And all camo’ed out.

While I do not know its purpose or owning agency, it definitely appears to be some sort of relay site, with the cheesy, wire omni antenna (even with an antenna BNC connector, who’d have thunk?), perhaps monitoring VHF high-band transmitters around the peak and relaying messages/signals from them on some UHF frequency using the directional Yagi antenna in the green radome.

Amazing that the panels are not damaged or missing.

The equipment enclosure. Must have batteries and the two radios inside.

The antenna connector at the bottom of the case. Note the green ground wire, so someone working on this has some fleeting idea of the correct insulation color for ground. However, it’s interesting that no critter has chewed through the insulation.

Honestly, I’d be so embarrassed to hoist an antenna as crappy looking as the VHF high-band omni on the right. And what’s worse, the connector used there is a BNC, definitely not rated for outdoor environments.

From the trail-top timber post, looking at the high point of Table Top. There is a very deep gulley/draw between there and here and the trail to the peak is around the east side of the mesa.

As I get closer to the true peak, a shot back toward the SE end of Table Top – the radio equipment and trail-top timber are at the right side of the ridge.

Finally, the benchmark is achieved. It’s been sprinkling lightly for the past hour.

The peak register is hidden near the benchmark. Signed in.

From the top, came back down retracing the path up.

Arrived at the truck right around sunset, by the time I made it to I-8 it was well after 1900.

No CBP or DEA observed. I’m sure that they were observing me, though %^)

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.


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.

LNA mounted – time to test!

To recap: I’ve taken the LNA that I purchased from iseeabluewhale on eBay and put it into a diecast aluminum box (purchased 10 of those from wonderco_buy on eBay as well). The TNC pigtails came from my friend Chris’ stash. The other bits and pieces came from the fossil beds of the garage.

Turned out to not be so tricky to get the thing mounted and connected.

Put it up on the roof behind the FM notch, and powered by 4 NiMH batteries.

First test – sweep 100 – 200 MHz and see what it looks like. Hopefully it looks just like the sweep from last night, just 20 dB higher.

100 – 200 MHz Pre-LNA, with filter, from last night (red peak, green instantaneous):

100 – 200 MHz w/LNA, with filter:

No obvious instability or oscillation. All the signals I can hear, like NOAA weather, Arizona DPS, aviation AM, even the residual signals from FM broadcast, all clear and crisp. My my my. Looks like pretty good fidelity.

Now I’ve just got to get a source of stable dc power to the amp! And I like these little boxes…

Spectrum scanning (again)

Now that the filter setup appears stable, it’s time for another assay of the spectrum around the QTH with the discone.

001 – 100 MHz (old):

001 – 100 MHz (new):

Pretty big difference! And just to check the ICOM demodulator, here’s the same spectrum using the AM demodulator.

100 – 200 MHz (old):

100 – 200 MHz (new):

Low noise floor, more better! Still some strong interference, but livable.

200 – 300 MHz (old):

200 – 300 MHz (new):

So much better.

With most of the big interferers suppressed significantly, tomorrow I will put one of the LNAs in a case and get it up on the roof as part of the lineup.

FM broadcast band notch filter update

Wasn’t able to spend any time on this the past week or so, but today I finally tracked down the pesky problems that I was having with my temporary installation.

I’d damaged one of the original TNC pigtails used to connect to the filter, and that created a sometimes 30 dB additional loss. Also, I finally found a marginal to no-good TNC-f to TNC-f adapter that I was using temporarily to connect the TNC-m connector on the box to the UHF-m connector on the cable that runs from the roof to the shack. I don’t like UHF connectors of any type, but the discone has a UHF-f connection and this cable was originally connected directly to the antenna. Until I finish my next phase of project (getting LNA into a die-cast box as well) I will leave it this way.

Using the ICOM PCR1000 receiver, here’s a plot of 50 to 150 MHz. Pretty serious FM broadcast band suppression!


Still a few broadcast stations making it through, but much better than before. The plot below is the one from a few weeks back when I first got the filter assembled into the box.



The following is what it looks like today.


What’s changed? Certainly the filter/coax assembly is doing a better job of rejecting the FM broadcast stuff, but what’s curious is the new noise floor rise that wasn’t apparent before. That noise floor rise corresponds to the band notch characteristics of the filter, but I don’t know why I didn’t see it before.

Also, the installation needs to be rid of the coax adapters that I’m using while the project is midway. Once I get the LNA into a cast box, then both the LNA and the filter into a bigger cast box, I’ll install N-f connectors on the outside of the big box and will no longer need the adapters.

Finally getting somewhere…