Updated Shack - Episode I

Episode I - Episode II

The planet earth has seasons, and that's a good thing because who can take twelve months of winter? I go through seasons too, probably just like you. Sometimes I get kind of bored with things and just need a change. Other times, after using something for a while, I get to a certain level of frustration that I ask myself, "Why do I put up with this?". Then the creative juices begin to flow and my tiny Shack gets an update!

I decided to take my credenza and add a small shelf to the front to hold a keyboard or two. Then I added a small back-angled shelf on top to hold the radios and allow small storage under the radios. Lastly, I added a back panel to mount two monitors, an antenna selector switch (behind the right monitor), and a RigRunner 4007U (below the monitors). The HP VH240a HDMI monitors with built-in speakers are mounted with Mount-It! MI-2829 tilt-swivel brackets. Two large pass-through holes at the base of the back panel put all wiring behind the credenza for a nice, clean install. A small shelf up top is home for the HTs, the ZUMspot and some other small things.

The shack is now run entirely on a Raspberry Pi 4B 4GB with the latest Raspberry Pi OS. The Debian Ham radio bundle which includes CQRLOG, JS8Call, WSJT-X, FreeDV, and a few other helpful programs, drive my USB connected Yaesu FT-991A. A Rowetel SM1000 sits to the right of the FT-991A. Also pictured is a Yaesu FTM-7250DR, and my old FT-7800R which will be trading places with my less-old FT-7900R, now used for local repeaters and simplex in my workshop.

Right now, I am quite content with this setup. But yes, I still have to get the old Barker & Williamson BWD-90 folded dipole up for HF. I like the GAP Titan DX, but verticals are so noisy compared to the folded dipole. And then I should probably do this, and maybe do that, or maybe just... be content!

So now I can enjoy Ham radio again at my tiny new shack. And then the next season will come. Change can be good, and God is always good!

Episode I - Episode II

ZUM Radio Repeater Build - Part 1

Repeater Build Part 1 - Repeater Build Part 2 - Repeater Build Part 3 - Repeater Build Part 4

 

Here is a project involving a ZUM Radio duplex MMDVM and a Raspberry Pi 3 B+ combined with my trusty old Yaesu FT-7900 and FT-7800 radios, and a couple of mini-DIN cables. Together, a trial version of small digital all-mode repeater capable of full duplex D*Star, DMR, NXDN, P25, POCSAG, and Yaesu System Fusion should be the result. If this works out as expected, I will likely be seeking out an old GE Master II, or any other robust analog repeater, to handle whatever mode is selected.

Pins and Colors

So it's been a little while, and I finally figured it all out. Part of the problem I found was the Yaesu CT-39A mini-DIN wire color was incorrect for the pin location. So lets forget about colors and talk straight up pin number to pin number. Conduct a simple ohms test on your mini-DIN cable pins to determine what color goes to what pin (my Electronics-101 oversight...)

As stated on page 10 of the Yaesu FT-7900R user manual, the pins are identified by both number and function. Using this, combined with the pin information from the ZUM Radio, I found the following connections to work properly using one FT-7900R as a simplex digital mode repeater.

Note: Two wires on the CT-39A mini-DIN are not used: Yellow (RX1200), and second Black (shield ground).

The pins - looking at the back of the FT-7900R - are identified in the following locations. The locator tab will be at the bottom center.

 

Pin 1: top left - PKD (DATA IN)
Pin 2: top right - GND
Pin 3: middle left - PTT
Pin 4: middle right - RX9600
Pin 5: bottom left - RX1200
Pin 6: bottom right - PKS (SQL)


Keep in mind, this will transmit when anyone keys up on the WIRES-X, YSF, or FSC rooms you are connected to. Be sure to keep the power as low as possible for your needs, and share the air.

Now to get a repeater frequency allocation from the Wisconsin Association of Repeaters and get this working as a duplex repeater!

Pi Cooler

The Raspberry Pi ZUM repeater board gets a new case and a custom fan install to keep things nice and cool. This is a HiFiBerry box, which is tall enough to have a GPIO hat and a fan inside. I cut a 1.125" in the top and mounted a Pi fan inside, blowing directly down on the ZUM Radio hat and Raspberry Pi. Temps stay under 40 degrees C.

Repeater Case

There it was, down in the basement. A lonely old Windows computer that has seen it's better days. Perfect! I gutted all the hardware out, saved everything that was still good, and prepared the case to be converted into my new ZUM repeater box.

I was able to rewire the existing power supply to reduce the number of wires clumped together for the previous occupant of this case. Now I have 17 amps of 12 volts, 18 amps of 5 volts, and 11 amps of 3.3 volts available, all regulated and fan-cooled. This works out perfect for all my needs.

Getting everything positioned in the case is pretty easy, so long as the fans have coordinated air movement over the radios and through the case.

I'll need to fabricate a new front face plate to incorporate the two radio faces, a Nextion touch screen, the voltage and temp monitor, and the power switches. The Raspberry can be controlled via SSH, but a re-program of the Nextion screen can provide the shutdown capabilities I am looking for. It should work well and look pretty nice when it's all done.

Propagation Estimation

I found a tool online to help estimate propagation from the repeater's site at Radio Mobile Online. The parameters I used for the estimate are a 6 db vertical antenna at 55 feet on 146 MHz. This, of course, only gives a general idea of coverage. The actual specs will be used as soon as I get the frequency allocation from the Wisconsin Association of Repeaters.

This map is at 5 watts output. Since the goal is to serve the surrounding communities, I would like to keep the repeater at 5 watts to prolong the life of the FT-7900R driving the repeater, but a real-world test today around the area had the 5 watts barely making 5 miles; at 6 miles there was almost no squelch break on the Yaesu FTM-400XDR in the car. I was always told to expect one mile per watt on the ground, so I'm not really surprised. My Diamond X300 antenna, at 55 feet, is basically on the ground, here in the woods.



For comparison, I can hit the WE9COM repeater in Plymouth from my QTH using my FT-70D and FT-2D on 5 watts. The RFinder app lists this repeater as 14.1 miles from my QTH. This is 2.82 miles per watt. Here is an example of antenna height making all the difference.

Below is a map I made with a 5 mile, 10 mile, and 15 mile radius. If one watt per mile on the ground holds true, this map should be better aligned with real-world expectations and performance.

Repeater Build Part 1 - Repeater Build Part 2 - Repeater Build Part 3

Memory Lane

Yesterday, I was searching the internet for electronics kits when I discovered Heathkit is in business again, not like they used to be, but there they are. Wow, the memories that brought back. My first shortwave receiver, listening to the radio with my dad when I was only in the single digits. Then I was trying to recall the model of the radios we had. Well, here they are.

When I was just a little guy, dad had this big gray radio with pull-out drawers in front, a big silver tuning dial, and a big matching speaker. Ends up that radio was a National HRO-60. This is exactly like I remember. The box-jointed wooden crate, the four A, B, C, and D tuning coils. The awesome silver dial that brought the world to my ears, and my imagination. That dimly lit meter glowing with the hope of hearing yet another new friend somewhere out there in this vast world of radio!

I remember tuning the big dial, swapping the tuning coils out, and staring at that big speaker listening to the whole world pass by right in front of me. And somehow, this was all made possible by a thin strand of wire strung out the window to a tree in the yard. Wow. The glorious triumph of those warm, glowing tubes eagerly seeking out the tiniest of signals! I wonder where that radio is now...

When I hit the double digits, dad bought me a radio of my own. For many years, I lost interest in radio out of frustration of not knowing Morse code. I understood it, but just couldn't seem to develop the ear for it, especially mid-message. My radio was the Heathkit GC-1A Mohican, just like this one. This radio sat in my room all the way through high school. Every once in a while I would spin the dials, but somehow never regained interest in it.

In the mid 1970's, the big thing was CB radio. In 7th grade, I had a Realistic CB radio, a crystal police scanner, and later, a Midland CB radio. My next door neighbor Billy and I would talk back and forth on the CB all the time and listen to the incredible "skip" at night, hearing guys seemingly from all over the country. Ah, the good old days. How time flies...