IC-502 + DigiVFO

 The Icom IC-502 from the mid 1970's is a standalone 3 watt, 6 meter band SSB / CW transceiver.  I've made contacts with this radio during e-skip openings.  Its a tough little radio to tune because the knob requires the steady hand of a safe cracker to operate.  It also drifted with the original analog VFO during a conversation.  The original VFO is a completely analog device, with less accuracy that we're used to the 21st century.

QRP Labs came out with their Digi VFO product late in 2025 based on the popular Prog Rock 2 product.  This tiny board now boasts a display and rotary encoder, as well as CAT control capability for a modest price.

Based upon the suggestions of others in the amateur radio community, it seems rather easy to remove / or simply disconnect the original VFO and use the Digi VFO in its place (after providing a good low pass filter), The attenuated signal came out to be just less than about 1 volt peak to peak.

The original VFO was easily removed with only 4 electrical connections.  The gear reduction drive and VFO unit separated with just two set screws.

The plan was to make a mounting plate for the Digi VFO and mount it back in the original location and use the original knob.  This required a shaft extension, but that's a simple mechanical adapter that I made on the 3D printer out of PLA with carbon fiber for added strength.

I mounted the Digi VFO board directly to the rotary encoder assembly simply because it was convenient to do so.  The low pass filter design ended up being a modification of the QRP Labs LPF kit to turn the square wave output into a smooth fundamental 36Mhz to 38Mhz signal out of CLK0 pin.  The BFO setting is at 13.99600 Mhz and Low setting for a heterodyne radio Local Oscillator injection. In the Digi VFO setup menu and starts displaying at 50.100 Mhz for convenience of the operator to produce at 36Mhz output at a display reading of 50.000 Mhz

(The Digi VFO could use an option for 10Khz per knob rotation to move quickly through the band with the single click of the knob, but I won't knock the product. It is very good.)

Packaging is key.  At least when the new product is displacing a much larger component, it makes it easier.  I managed to solder everything to mount to the rotary encoder with shorter jumpers than in the previous photo.  It fits nicely in place of the original with a carefully manufactured adapter plate.  The output of the low pass filter is clean and sinusoidal.  The spectrum analyzer shows a clean output from the transmitter.

The result was so encouraging, I decided to modify the original radio cover to accommodate the frequency readout.  The display sits directly above the VFO tuning knob.  The tuning knob uses a shaft extension to employ the original tuning knob without the reduction gearbox.

This project was a complete success bringing life back to an excellent product.

APRSTASTIC: Automated Packet Reporting System with LoRa Mesh Networking at W3HZU

The W3HZU Keystone VHF Radio Club is embracing innovation with the APRSTASTIC project, utilizing MESHTASTIC firmware over LoRa to transform Amateur Radio Positioning System (APRS) communication. Traditional APRS relies on a network of fixed stations.  Traditional APRS on the 2-meter band typically involves devices sending packets with location data and other info to an APRS digipeater (digital repeater) or an Internet-connected gateway (IGate). These packets are usually transmitted at 1200 baud using AFSK (Audio Frequency Shift Keying) modulation.  The APRSTASTIC software project takes it further by leveraging a mesh network on the 900 MHz frequency.  https://github.com/afourney/aprstastic 

So, how does it work? APRSTASTIC, created by Adam Fourney KK7CMT, is a project that integrates MESHTASTIC firmware with APRS functionality. It allows devices to join a mesh network, broadcasting APRS packets that include location data, messages, and more. These packets are transmitted over LoRa modulation, which offers long-range, low-power communication ideal for this setup.  Only amateur users are permitted to use the APRS network, so the software requires users to register with the service.  This attaches the eligible user's callsign to messages and allows access to the gateway functionality.  The basic function of GPS tracking is supporting reporting mobile node location to the APRS map.  As part of the mesh, devices can relay signals, extending the network's range and coverage. This makes APRSTASTIC particularly useful for tracking, emergency communications, and community networking – all without needing extensive infrastructure.

APRSTASTIC presently supports features like SMS messaging and Winlink integration, making it a versatile tool for emergency communications, and remote messaging.  The hardware consists of a Heltec V3 LoRa node running Meshtastic firmware.  The short name is assigned "APRS" and the long name is "W3HZU-12".  The Heltec V3 board is attached to a Raspberry Pi computer with a simple USB-C cable.  The Raspberry Pi runs the APRSTASTIC python software package on a fresh install of the standard Raspbian OS.  Very little customization needs to be done to get this running.  It is low-cost and low power.  The club member Ron K3HIL developed a few linux cron job scripts to keep APRSTASTIC running reliably, and restarted if there is a problem.  The W3HZU-12 node communicates easily to the repeater node on the club's 100 foot tower, which supplies APRS network access for many miles in York County, into parts of nearby Lancaster and Lebanon Counties, and lower Dauphin County.  Infrequently the APRS node announces its presence and invites amateur users to register by replying with a Meshstastic message containing a "?"

At W3HZU, this technology is opening new doors for radio enthusiasts.  It is a stepping stone to gain interest in licensed amateur radio, as we have a large Meshtastic user community in the tri-county area.  The project's open-source nature, hosted on GitHub, invites collaboration and customization, making it a promising development for the amateur radio community advancing the art of radio.  Club members Eric N3FIX and Ron K3HIL have been working to encourage the maker community to join forces with the Amateur Radio community in this project.  The support received from both the Keystone VHF Club and the Susquehanna Valley Mesh community has been mutually beneficial.

https://www.w3hzu.com/aprs-gateway/