Welcome back to Sarah from the SignalsEverywhere YouTube channel who has recently returned to producing videos from a hiatus. In her latest video, Sarah shows off her new OP25 Mobile Control Head Android App which allows you to implement a full P25 digital radio scanner at a fraction of the cost of a commercial digital scanner. In the past, Sarah had released a similar application written for the Raspberry Pi but has decided to shift her focus to writing an equivalent Android app that is less clunky and can be deployed for a lower cost.
The app controls and displays information from the OP25 software that runs on a Raspberry Pi with RTL-SDR connected. It works by using a server application on the Raspberry Pi that manipulates the OP25 instance and its configuration files.
Sarah writes:
The application is a wrapper for OP25 that uses a raspberry pi and an android device to provide users with a mobile control head for their OP25 P25 scanner setup. Currently it's just a basic application but I'll be adding features like automatic site switching, etc.
Exponential market growth! Lithium battery technology has made exponential market penetration in the last decade or so. Once an exotic and expensive platform, today nearly every battery-powered device uses lithium. Along with increased market acceptance comes attention, both good and bad. Most of the bad news circulating about lithium batteries... Read more »
As radio amateurs, taking proper precautions against lightning and electrical surges can be a difficult and expensive proposition. We often neglect them and rely on luck.
After reading Bonding and Grounding for the Radio Amateur, I decided it was worth the investment. I already had all ground connections - house, tower, station - bonded. What was missing was bonding the antenna connections to the ground as they entered the house. I needed a Single-Point Ground panel.
A Single-Point Ground is a metal panel or box providing a common bonding point for all cables as they enter a building. This metal is connected to the external ground rods, which are all bonded together. The idea is to bond the cables connected together, so that lightning or surge potentials all rise and fall together. Without a potential difference, damaging currents cannot flow.
SPG panel ready to mount on basement wall
I cut a 0.090" Aluminum panel 12" by 16" and mounted the KK1L antenna switch to the bottom edge. I added lightning arrestors for the antenna coaxial cables, plus a barrier strip holding gas discharge tubes for the rotator and shunt antenna control cables.
I chose MFJ-272 lightning arrestors. I needed six of these, and the MFJ units were about $40 each. The Alpha Delta and Polyphaser units were more expensive. The arrestors are mounted to the panel with a single large screw, supplied with the arrestor.
Short coaxial jumpers connect the arresters to the KK1L switch. I made these out of 18 inches of RG-400 coax using new Amphenol UHF connectors and a UG-175 adapter. RG-400 is doubly-shielded, eliminating the potential for any coupling between the jumpers. (Notice I didn't quite have enough RG-400 for all six jumpers, so there are only five at the moment. I'll have to purchase more)
The panel mounts on the basement wall where the cables enter the house through a 4 inch PVC pipe. A grounding block connects a short piece of copper wire to an eight foot ground rod on the outside. The ground connection is also bonded to the perimeter ground wire between the house, tower and station grounds using a split bolt.
I had a bit of trouble with the coax running from the A and B ports of the KK1L to the operating desk. Since the coax to the antennas ended at the basement wall, I trimmed some coax from the antenna feed lines. To get the right length, I pulled the feed lines outside, then trimmed them from the far end. Simple, eh? Except the first one looped around and got stuck, and the cut piece ended up being about five feet too short.
The next feed line was a newer run of Davis Buryflex. I ran it to the A3S/A743, and then cut the right length. For some reason, I had problems with the connectors on both ends, but once they were redone, the cable worked as expected. For a short while, I thought the cable itself might be defective.
To do these tests, I made good use of my RigExpert AA-55 Zoom. Which of two pieces of old coax is any good? The cable loss test is quick and give one real numbers to compare. You just need to test the coax both open and shorted.
With the SPG installed, the next step is to automate the switching of the KK1L.
Many thanks to Rusty Epps W6OAT and the senior leadership of the WWDXC for inviting me to present on the important topic of tower safety. I presented to the group via Zoom at it’s on-line August meeting on Tuesday, August 11, 2020.
Following the presentation, I received this note:
Tnx again for a magnificent presentation to WWDXC. Folks stayed on line for almost another hour, discussing and sharing horror stories. YOU WOKE US ALL UP!
Stay vigilant; learn what you need to know to be safe . . . and spread the word. Visit zerofalls.org for more information.
Coronavirus is driving change across everything we do. With it’s April 2020 meeting The Northern Illinois DX Association (NIDXA) went to an online meeting format for the first time in its history. I did the keynote presentation from my home QTH in Massachusetts this past Friday evening April 10, 2020.
We used Zoom, the videoconferencing application that’s taken off in a big way as a result of mandatory social distancing and travel restrictions. As we kicked off the presentation, we took advantage of one of the in-built tools that Zoom offers – polling – to learn a little bit about the audience. Of the nearly 50 participants, we found that all but three – almost 95% – have some kind of regular interaction with amateur radio tower work. Clearly, this was an audience that should care about the topic.
The best indication of whether an online presentation has been successful may be the percent of participants who remain at the end of the talk . . . in this case, we had nearly 100% staying on to the end. It was also a pleasure to receive a few private emails after the meeting expressing appreciation for the information provided. We even got one email asking for an immediate purchase of one of the climbing kits.
A nationwide 5G cellular network is being built out now. The major network infrastructure owners and operators are taking this seriously. As they build up a force of expert tower installers and maintainers, they are committed to safety. Tower climbing can be risky – or it can be safe. The pros know how to make it safe – proper equipment and training are core requirements. Every ham who wants to work with antennas and towers should be paying attention.
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