FT-7900R ZUM Repeater Build - Part 1

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

 

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...

The BWD-90 Folded Dipole

With all of the projects and ideas racing through my head lately, I realized I have neglected to set up the Barker and Williamson BWD-90 folded dipole antenna I got from my dad, K2JGL (SK). I have been very preoccupied with C4FM, MMDVM devices, repeaters, Raspberry Pi computers, WIRES-X, lightning arrestors, grounding, and maybe a few other things. It's time to get back on the air on HF and make some real DX QSO's with the awesome BWD-90 antenna.

Walking through our property looking for a suitable location to set up the antenna, I see this is going to be a bit more difficult than previously thought. The basic site characteristics to setup the antenna would be a flat open space at least 120' long, 50' wide, and 50 ' high. Well, we live in the woods, so that's not going to happen. Guess I'll have to settle for whatever site I can find.

One of the many great benefits of this antenna is the ability to change takeoff angles. My plan is to have the ability to adjust the antenna for several configurations. The following is taken from the Barker & Williamson user instructions.

NVIS propagation is performed as a flat-top with height varying from ground level to approximately 12 feet. This height is dependent on the ground (soil) conditions. It may be possible to lay the antenna on the ground in desert/low water table environments. The B&W NVIS pole kits allow multiple heights. In NVIS installations a counterpoise will sometimes enhance performance. If you are not getting enough distance from your NVIS setup, try raising the center of the antenna a few feet to make a very shallow inverted Vee. (Appropriate NVIS daytime frequencies are approx 5-12 Mhz, nighttime are 2-4 Mhz.) 

Conventional propagation minimum clear height is recommended at 25 feet for operation down to approx 3.5 Mhz (ends 12 feet for inverted Vee or sloper), and 40 feet for 1.8 Mhz (ends 20 feet for inverted Vee or sloper). Less height does not disqualify operation, but may require a tuner on the lowest frequencies. Also, propagation may be reduced with inadequate height on the lower frequencies. 

The next step is to design a support system that includes a left, center, and right side pulley system so the antenna can be set in any position with the ends from 12' to 24' high, and the center from 12' to 40' high. This would allow everything from a flat-top at 12', to an inverted V at 40' above ground.

See the Wire Antenna Suspension System to see how I finished this project.

FT-70D on WIRES-X

To connect and control WIRES-X with your FT-70D, you first need to find the room or node numbers you would like to connect to at Yaesu's active Rooms and Nodes pages. All columns can be sorted. e.g. Sort by State to see rooms or nodes in your area.

If you are using a hotspot MMDVM, don't follow these instructions. See the information by Chris, K9EQ about this at hamoperator.com.

CONNECT - To connect to a WIRES-X repeater or node, select the frequency of the repeater or node, then press  MODE  until the DN mode is selected. Connect to WIRES-X by pressing   F   then  AMS .

SELECT - To connect to a room, rotate the  DIAL  until you get to the entry screen  EN # _ _ _ _ _ . Enter the room number and press  AMS 

STORE - After connecting to a room, store the room in one of five memory slots by pressing and holding the corresponding number of  1 ,  2 ,  3 ,  4 , or  5 . A confirmation beep will sound.

CHANGE - To change between rooms stored in memory,  DIAL  to the room and press  AMS .

DISCONNECT - To disconnect from a room, press and hold  BAND . To disconnect from WIRES-X and return to normal radio operations, press and hold  MODE .

If you run into trouble, just disconnect and reconnect to WIRES-X.

And there you have it!

Download the PDF of these instructions.

Blessings!

You're Grounded

Since my "ham budget" is, well... there is no ham budget. So spending big bucks on thick copper busbar, copper mats, copper this, and copper that can get pretty pricey, not to mention a non-negotiable with the wife. This is true especially if it's all prefabricated PnP stuff.

Being like most of you other hams, I like to design and build my stuff myself. In furtherance of this manly, hamly expression of creativity, I designed and built two ground and lightning suppressor boxes, and two interior ground busbars. One set for myself and one set for my friend Stu, KD9MNK. Here is what I came up with.

Busbar in the box with two ATT3G50U's installed

The busbar is constructed with a 1.5 x 1.5 x 0.125" aluminum angle and #10 x 3/4 stainless machine bolts. I drilled 1/4" holes spaced 1.75" apart, allowing for three Alpha-Delta ATT3G50U surge and lightning suppressors to be mounted on the bar, and a heavy ground wire block (top right) for the ground wire. While assembling the busbar, I applied Noalox to all metal surfaces to insure electrical connectivity and prevent corrosion. The exterior bar is housed in a 8 x 8 x 4" PVC junction box with a waterproof cover. The interior and exterior busbars are identical in construction, except for the length - the interior busbar is four inches longer.

The box I made for Stu is fed from the bottom with a 2" PVC conduit running from his home to the back yard where the box is mounted at the base of his antenna. A second 2" opening on the box floor provides the coax exit. this is plugged with a 1/4" thick rubber disk with holes for the coax to pass through. A third exit in the box - also plugged with a rubber disk - is for the cable grounding the busbar and the ATT3G50U's. Water tight. Bug tight. Nice.

The KD9MNK busbar box for the base of the tower

The interior busbar is mounted in the house, just inside the coax conduit feed point. Another set of Alpha-Delta ATT3G50U's reside here, as well as the grounding point for the radios. I designed a 1.25" conduit that passes from the basement, into the wall cavity of the room above, where the KD9MNK station is located. The 20" long conduit terminates into the bottom of a sealed plastic duplex electrical box. A standard blank wall plate holds two SO-239 connections and a grounding stud. Nice and neat. A ground line runs from the wall plate stud to the busbar and out an exit point from the coax conduit, just outside the house. Grounding rods take it from there.

Yup, this should work fine.

The K9KMS busbar box ready for installation at the base of the tower

The KD9MNK interior connectors and grounding stud

CQRlog

See the Update

"CQRLOG is an advanced ham radio logger based on MySQL database. Provides radio control based on hamlib libraries (currently support of 140+ radio types and models), DX cluster connection, online callbook, a grayliner, internal QSL manager database support and a most accurate country resolution algorithm based on country tables created by OK1RR. CQRLOG is intended for daily general logging of HF, CW & SSB contacts and strongly focused to easy operation and maintenance." - cqrlog.com

CQRlog 2.5.2 on Linux Mint 21.3

A couple years ago, I wrote about several Windows-based and web-based logging software systems for amateur radio enthusiasts. The web-based software provides users the option of using any OS, as all that is needed is a web browser, but on the downside, you also need an internet connection.

Long ago, while looking to get off the Windows bandwagon, I experimented with Linux, Redhat, and a few other OS's, but recently, I was introduced to Raspbian, a Debian-based / Linux-based OS designed for the Raspberry Pi computer. My opinion of Raspbian so far is very positive. The fact that the OS is free, and thousands of programs are available for free, helps my wallet recover from the ever-expanding money pit Windows based computers can be.

Now let me jump forward to what I really want to talk about - the new Raspberry Pi 4 and CQRlog. The CQRlog software package is touted as the best Linux-based amateur radio log program on the planet, and I may just have to agree. The Raspberry Pi 4, on the other hand, may just change the way we currently look at desktop computers. This is good.

I am a big fan of Ham Radio Deluxe, a fantastic Windows-based program, but now it is quite expensive, initially $100, then $50 per year for maintenance. And if you still mail out QSL cards, the annual cost of the hobby can really eat into the household budget. More recently, I was using the Log4OM software, another fantastic Windows-based program that has most of the bells and whistles of HRD, but the best part is Log4OM is free, but please make a donation to their work if you like it.

Then there's CQRlog, an open source software system that, when used with a few other Linux-based open source software packages, rivals anything out there, and it's free! CQRlog integrates with LoTW, HRDlog.net, eQSL, and Clublog. It also provides live logbook support through HamQTH or QRZ. HamLib takes care of TRX controls so current radio configurations auto-populate in the QSO window.

You can find all available software packages in the Raspbian/Debian repositories. In Raspbian OS, simply go to the Preferences menu and click on Add / Remove Software. Search Ham Radio and select all the desired software packages. It's as easy as Pi.

Update

September 29, 2020

So it's been over a year now since I started using CQRlog, and well, I'm still using it and I really like it! Logs are super easy to set up, updates to several online logs can be automatic and in real time, and the integration with LoTW is great. 

Services from the website HamQTH - from the makers of CQRlog and RemoteQTH - are well integrated into the CQRlog software. No nagging ads and no subscription fees. If you like the software and services, you are free to make a much appreciated donation.

This software has been very stable, reliable, and easy to use. I did have it crash twice, but I believe it was related to a rig control conflict I created by using several programs wanting rig control at the same time. My bad. As you can see, the appearance of the many interfaces are nice, clean, and up-to-date, unlike so many ham programs with the vintage 1980's, DOS-to-Windows transition look. 

CQRlog is clearly at the top of my list for logging software. See the CQRlog website for more.

Filum Receptorem 101

Back in the day, we were all taught that the most significant component leading to successful QSO's is the antenna. A really good, well tuned antenna can help you generate more QSO's with even the most mediocre radio, than any other upgrade you can make in your system. For this reason, we first need to analyse our antennas in every aspect, and second, be sure we are providing the best possible environment for the antenna to work properly. With this in mind, antenna design, polarity, placement, and feed should all be considered.

At my home QTH, I currently have two antennas set up. For 144/440 MHz, a Comet GP-6 sits atop a 55 foot tower, and for HF work, a GAP Titan DX is mounted 2 meters above the ground, both in a less-than-ideal environments. We live in a tall forest with sandy soil and beach sand containing magnetite, and my home and barn have metal roofs. The GAP is positioned half way between the buildings, about 30 feet from either. As you might agree, not the best of situations as far as antennas go, but that's the best we can do here, given all factors.

As the antennas are in their current position and environment - on a sunny August 21 with heavy foliage - I captured the following readings with my Comet CAA-500 Mark II antenna analyzer. I am pretty happy with what I found. This should help me take better advantage of the frequencies that might provide the best situation for success.

Blessings!

Comet GP-6

2 METERS

70 CENTIMETERS

GAP Titan DX

10 METERS

12 METERS

15 METERS

17 METERS

20 METERS

30 METERS

40 METERS

80 METERS

Even so, I am having a great time making QSO's all around the world and making good distance in the local area. So far, I have nothing to complain about, though I have no experience or knowledge of what it is like having what one might consider ideal conditions. I'm in this for the enjoyment of the hobby, and "just havin' fun" is what I am doing!

Favorite Pi(e)

When Nancy and I go out to a new restaurant, we always ask if they have my personal favorite, Key Lime pie. But since last week, I may have to change my thinking and cautiously consider Raspberry...

First, it was the Raspberry Pi zero for my ZUMspot. I was so amazed with it's simplicity and usefulness, I had to get a Raspberry Pi 3 B+. It was like a whole new Raspberry world opened before me. And all I could think about before was Key Lime pie. Ha! And now comes the Raspberry Pi 4, the newest Pi on the pi rack, my favorite Pi so far.

The new and amazing Raspberry Pi 4 (2GB) running Raspbian is my shack's main desktop computer.  CQRLOG software is now my go-to radio log, the FreeDV software is set up for digital HF, and Gpredict for satellite tracking. The Raspbian/Debian repositories have a Ham Radio package that includes a host of programs for amateur radio Linux users. Did I mention all of this open source software is free? Yup. Free.

Space TV

Of all the out-of-the-box things I can think of, this was not one of them - sending pictures via amateur radio from space to earth, especially when they originate from the International Space Station orbiting the earth at 19,000 mph!

Here are the results of my very first attempt with SSTV on August 3, 2019.

And the confirmation from ARISS.

How cool is that!

Are you experimenting with amateur radio? If not, why not.

DX vs. MMDVM

For a while now, its been a little tough to get regular DX the old-fashioned way. Aside from that, FT8 works fairly well on 20m, but that's not for everyone, and it pretty robotic and impersonal. There isn't enough people on HF DV like the FreeDV 1600 and 700D modes, so it's less than a thrill right now.

That being said, there is hope. There has been a tremendous increase of activity on the MMDVM front. With new gadgets hitting the market as fast as baby rabbits, even the Tech hams can now talk around the world, and on an HT to boot! Yeah, it's not like the traditional and personally rewarding "contacts" like we are used to, flexing our RF muscles in cunning and calculated ways, but the end result is the same. Hams talking to hams around the world, and how cool is that!

So my FT-991A isn't used quite as much right now for DX, but the FTM-400XDR and FT-70D are barking up a storm from my ZUMspot and a few connected Yaesu WIRES-X repeaters in the area. My favorites right now are America Link and MNWis. Ride the wave, baby! But if the internet goes down, make sure you are squared away in your own shack. Independence is highly rewarding!