What follows below is a combined 'first post' of a very long discussion that was taking place on a closed message. We just felt that it was interesting and worth sharing with everyone up front. Let the discussion also continue here.
ORIGINALLY POSTED by @WA3LTJ:
Lynn, there is an idea that I have been thinking about for a while that maybe you can provide feedback on. It is not far from the CRT2-mini. Note, I have a moderate amount of experience with mixed signal and small embedded systems. A few of my creations are products, some are running in a research laboratory, and many are for my own education (and amusement).
REPLY by @KU7Q:
Andy, I was quite surprised when my articles landed in QEX. I'm pretty sure it wasn't because of the highly technical nature of them (no formulas or theory). I think it was more because they were niche articles that didn't appeal to a wide audience. QST seems to prefer more generic articles.
I'd be happy to comment on your project idea. My background is in electric utility communication systems O&M, but I've always dabbled in creating devices and systems that helped the maintenance technicians do a better job. The last 5 or 6 years I've focused on small embedded systems. I enjoy the process of bringing a new idea to life and I'm so stubborn that I don't stop until it is doing exactly what I want. The last 10% of the project takes 80% of the time. But that's OK. I'm retired now and it fills my days.
REPLY by @WA3LTJ:
Lynn, I have been thinking about various ways to combine transceivers and antennas together as a single package. Conceptually, this is not new. A handheld radio is a transceiver with the antenna on top. A mobile radio and a repeater are stations where the transceiver, power and antenna are collocated.
Right now I am thinking about making a remotely operated POTA station. The antenna can be a loop antenna on a tall lighting stand with the radio and battery just below. However, the radio, battery and controller could be one package used with any of several antennas. If Jim had his way, the package would have a wide-range antenna tuner.
I expect to run 100W. The operator accesses, tunes and operates from 10 to 50 feet away. This should not be difficult. The loop antenna uses a motor-operated capacitor. Tuning requires switching the transceiver to 5 W and monitoring the SWR reading. After that, radio operation is relatively simple in POTA operation. I want to run SSB, so audio will need to run in both directions.
The ideal package will be waterproof and not difficult to carry or set up. I envision operating remotely from a picnic bench, car or tent. I figure Wi-Fi is a good control link. There could even be a dedicated access point on the ground half way between the station and control site, if necessary.
Thoughts?
REPLY by @KU7Q:
Andy, The remote control part isn't that hard to do, even over WiFi (I already do that on my CTR2-Mini). The complexity comes when you want to move audio between the radio and the controller on WiFi. On the radio end a Raspberry Pi with the right software could handle everything you'd want to do. The user end is more problematic. The obvious answer is to just run a cell phone or tablet and use a browser with HTML5. That's where the bulk of the complexity comes in.
In my opinion, if you're only needing to run 10 to 50 feet WiFi is overkill. A controller like my CTR2-Mini could handle almost everything you're describing (albeit you may need to drop the CAT rate down to 4800 baud if you're going 50 feet). In it's native mode the Mini only handles CAT, PTT, and Key to control the radio. It has a radio dashboard that lets you easily control many of the settings on the radio. My new CTR2-Mini Audio Controller adds the ability to push transformer isolated Line-In and Line-Out audio across the CAT5 control cable to the new CTR2-Mini Audio I/O module (described in the link above).
I actually have a new Mini design almost ready for a board run. I'm tentatively calling it CTR2-Max (Mini on steroids 🙂) because it integrates the Audio Controller into the current Mini's design and uses the new Audio I/O module instead of the Radio I/O module. It does require an external box to allow for all the required connections. It wouldn't take much to design a wireless antenna tuner control interface based on an Xiao ESP32-C3 with a small display to go along with the Max. The ESP32 in the antenna tuner controller could use Bluetooth or be set up as a WiFi IP access point. The Max would connect to it the same way as it connects to my CTR2-Mini Antenna Switch Controller. It would be easy to modify the current External Tuner page to display power and SWR and allow the encoder to control the motorized cap on the loop.
The user control end would be just the CTR2-Max, mic, headphones, and paddles. You would need a battery at the control end or you could run a pair of wires to the battery at the radio end. The Mini draws about 200 mA at 12VDC. The radio end would be just the Audio I/O module connected to the radio and the new antenna tuner controller connected to the antenna tuner. Since the Mini/Max already has the ability to control a wide range of radios this configuration gives you the opportunity to choose the radio and antenna/tuner that works best for you.
Here's a drawing of what I'm thinking about.
This may not be what you're looking for, I'm just throwing out ideas,
73, Lynn
REPLY by @WA3LTJ:
Lynn,
I am just beginning to understand the CTR2 architecture. I appreciate your familiarity with the challenges and your interest in the problem. A few thoughts:
In 2019 I designed a self-tune circuit for the loop antenna. It actually used an ESP32 (Sparkfun Thing) and matching motor driver board. I like the ESP32 processor except for the lousy A/D converter. The Thing has been replaced by a different board as part of a standardization with Adafruit. I have been using the Feather M0 recently. I think they have a WiFi version. The self tune circuit used a RF clock generator board to sweep a signal and a RF log amp to sample the main loop element. I could strip down that design and make a simple motor controller. I would need some way to start and stop the motor with low latency through the wireless network. I am not sufficiently familiar with HTML5 or PHP to accomplish that.
I did not realize the difficulty of streaming audio. I am familiar with the Raspberry Pi. I built an application for playing videos and streaming sites. It uses VLC. SSB POTA operation benefits from rapid contacts. After doing remote rig contesting, I have learned that a quick turnaround is not always easy to implement.
I do not want to use a CAT5 cable in the POTA solution. It would be fine in some circumstances, but I learned in Canada that sometimes the path between the equipment and the operating seat is not one to lay a cable. People can trip and fall, or the route for a cable is much further than the line-of-sight.
It would be great to have a COTS solution to my POTA idea. I don't mind having a PC, tablet or RPi at the operating position. I am a little concerned with the power budget at the radio. 200 ma continuous draw is perhaps the limit of what I would like to burn. I use a 20 AH LiFePO4 at the moment. Unfortunately for the battery, I am used to operating for 3 hr straight. That is easily the limit of the battery with the radios I use.
Just my thoughts.
Andy
REPLY by @KU7Q
Andy, I can appreciate wanting to be wireless due to tripping hazards. I was just brainstorming how the Mini could be used in this situation. Thinking about it, if you're Ok with a laptop running at the control site your best bet is a Raspberry Pi on the radio end running Node-RED for control using JavaScript for CAT and PTT, not Key, and run the Sonobus audio server on the Pi and on the laptop to handle the audio. The difficulty comes if you want to support more than one CAT protocol, control different types of tuners, or use CW. Node-RED eliminates the need to do the HTML stuff.
73, Lynn
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THAT'S THE END OF THE ORIGINAL POSTS.