The AN/PRC-9 sets was disappointing to miss out on, but I did get one item I have been after, a teletype.

Last time I saw a teletype in service was mid 90s, email and other electronic communications made these unnecessary since you could print what you needed and discard the rest without wasting consumables. Like the Remington typewriter I have, these mechanical devices are fascinating and the distinctive sound they make should be nostalgic for anyone visiting the station that worked with teletype when they were in service.

It appears to be in good condition, with no obvious damage, but getting this hooked up to something to drive it will be a challenge. Goal will be getting it cleaned up, operational, and able to type things I send it from a Raspberry Pi using FLRIG and FLDIGI. Actual RTTY seems fairly rare these days but I should be able to send text from any digital mode, or really any text that I want a printed copy of.

Edit – FairRadio ran out of stock before my order, so I wont end up with these. There really aren’t many places that have these either so I may have missed my window. Disappointing but ill keep looking and hopefully get lucky sometime.

Following the SCR300 radio, the Army acquired the PRC-8 (Armor)/9 (Artillery) /10 (Infantry) series of radios. These radios were in service for the 50s and early 60s. I previously have taken an unsalvageable PRC-9 as a housing for a modern radio set, but I got a couple of additional salvageable radios which I intend to make operational mostly as issued. The batteries are no longer made, so I wont be able to use those, but there are some alternative power sources I have found that others have come up with.

The PRC-9 that I used gave me a bit of familiarity with the innards and the parts that weren’t corroded I kept. This should give me some spares, a few of the tubes seemed to be in decent shape.

From an amateur radio use perspective, the PRC-10 (38.0 to 54.9 MHz) covers the 6m band and the PRC-9 (27.0 to 38.9 MHz) covers the 10m band. I selected this model because it was the Artillery version, not for its frequency coverage, but it appears that I got lucky, 10m seems more active to me than 6m over the years I have been listening to the amateur bands. The PRC-8 (20.0 to 27.9 MHz) would have been a good selection too, covering the 15m and 12m bands.

I have been wanting a deeper understanding of radio for quite awhile, and this project should do just that. I did work on tuning 12 series radios (the RT-524) in the late 90s full time, but that was just following a script more than understanding fundamentally what I was doing. My basic understanding is that antennas pick up tiny voltage differences and amplify them but the roles of the various components I am not familiar with. Ill just have to start at the beginning, take this in steps, and slog through the math. The math part I am not really enthusiastic about, but I won’t gain an understanding if I skip that part.

I also have a second Transoceanic 3000 that needs repair that I can explore after this project, which should be an interesting comparison of differing receiver designs.

For the 3 lever light switch (MS51113-1) the replacement connector can be found by searching for part 7716895.

From Big Mikes Motor Pool at https://www.bigmikesmotorpool.com/products/three-lever-light-switch-ms51113-1

The connector itself is unlikely to be bad unless its damaged, if you are doing a rewire it is likely that this part won’t need replaced, just redone. If you get a replacement you will have to wire it anyway. In my truck the wire insulation was crumbling in places so I am doing a complete rewire, including this assembly.

Use silicone grease and gently nudge the protective rubber shell over the wires. It will take some patience as you don’t want to damage the rubber so it can be reused assuming its still serviceable.

Once cut free, you can tin the solder cups. Lead free solder was not working for me, I had to use lead solder. The cups have to be clean and clear, I heated each cup with iron at highest heat setting and tapped the assembly on the worktable to dump the solder in each cup. I used a torx screwdriver to ream out each cup to have a clean surface as used flux and other junk accumulated in these cups.

Before soldering, the wires must be combed and in the correct order or it will tangle up and the protective rubber shell won’t fit over the wires as it should. All the parts should be inline as it will be when it comes together to prevent not being able to get it assembled when complete. Juggling the wire order while also trying to work in the tiny spaces is a challenge. Wiring from the inside of the assembly and working your way to the outside ring helps a bit with the cramped space.

Tin the wire, if using the military type 14 gauge M13486/1-5 wire (Prestolite is the maker of the wire I have), it will take high heat and lead solder to tin this wire. It should have a coating of solder without blobbing, and should fit into the cup on the connector. Flux well and heat the connection, when you feel it drop down into the cup, and is filled with solder, the connection is done. It takes some time and a lot of heat to get the wire to drop in the cup. I used denatured alcohol (sold as alcohol fuel at home depot) and qtips to clean up flux.

When I finished soldering my connections, I tested the assembly by checking continuity with a three lever switch connected. One end of the multimeter on the power feed line (circuit 15) and switching the three lever switches between modes to see if there was good connection. I used the standard military circuit list called “7070301 Circuit Numbers” an example of one can be found at https://jatonkam35s.com/DeuceTechnicalManuals/7070301_circuit_numbers_dolph.pdf. My wiring isn’t standard, but the closest diagram I could find was at https://wawii.com/images/M37%20Wiring%20Diagram%20-%20with%20Signal%20Stat%20900%20a.pdf

The metal wire tags and stamp set I found at https://www.nationalband.com/wrap-around-tag-m434363-1/ part or style number is M43436/3-1. The 1/8th in stamp size fits on the tag and appears to be what was used on the original. The stamp set is found at https://www.nationalband.com/fasteners-accessories/ as style 1571. The sales rep told me you can wrap these with finger pressure and I didn’t really believe it, but its true, they bend into shape fairly easily, but once on are sturdy. When stamping the numbers I am using a light tap with a light hammer, it does not take much to imprint the numbers on the tag.

The opposite side of this assembly will be Packard rubber shell connectors so the assembly can be serviced later if needed.

I don’t intend to crack open the 3 lever switch itself, but I did find an article where someone did and I found it interesting to see how this switch works – http://pages.suddenlink.net/randygar/switch/switch.html

One thing I thought when I got this truck, after looking under the dash, was “I hope I never have to mess with the wiring”.

On rare occasions, this truck would act flaky with the electrical systems, headlights wouldn’t turn on or difficult to start, but it was always brief. I did get a three lever switch at one point, but the problems never really occurred that I noticed after this.

After the rebuild, and driving it for a bit, I noticed the service lights were flaky and I didn’t have turn signals. I got it home and discovered a fuse was melting but not blown. I poked around for a bit and decided to stop driving it since something electrical not working right is a great way to start a fire. A good thing I did, since I found what was likely the foundational issue, the main battery cable sheathing had worn through in multiple places and was arcing on the truck somewhere. The wiring in general is about 20-70 years old and probably could benefit from a refresh so I am doing a rewire. There are wiring harnesses out there for sale, but all of them assume a fairly standard M37, which mine is not. Its a 24-12v conversion with some extra items that aren’t on a standard M37, a siren, cab heater, and whoopee light for instance, as well as some engine modifications to the ignition system that make going back to 24v impractical.

Ill post about this project as I complete systems to document my experience.

M37 Diving (odysee.com) – Short clip of driving while breaking in engine

Finally ready after nearly 2 years of rebuilding. The engine has a lot of power, easily climbing up hills that it struggled with before. The cacophony of odd noises is much less, and the engine oil is as amber as it comes from the container without all the liquified char. The last part I assume won’t last long, but its still jarring to see a military vehicle without liquid carbon as crankcase oil.

For Winter Field Day we setup at Perry State Park, vicinity of Catfish Alley – https://ksoutdoors.com/State-Parks/Locations/Perry/Perry-Gallery/Catfish-Alley-Primitive-Campground

Got the M35a2 serviced at Valley Truck & Trailer – Truck Repair Shop in Valley Falls (business.site) – and they did a fantastic job getting old rubber items such as coolant hoses, belts, and other seals changed just in time to get us in the field. Everything was soggy from ice melting and rain the previous day, so getting fires started was a challenge. The coal stove never got hot enough to light properly but fortunately we had a Mr Heater propane stove that worked very well.

We made a large handful of contacts, but not a huge number, our focus was working out tech issues and showing the people new to amateur radio the basic procedures. Also, we just had a ton of fun just camping and made a relaxing weekend of it. I am very happy with the setup, getting on the air didn’t take much time at all and we didn’t have the problem of hauling heavy items to the tent to operate.

Our setup was an IC7300, with IC7200 in reserve, next go around we will get both radios going one digital and the other voice. Bearcat 996XT to monitor the local activity, and an IC880H for VHF. Antennas were discone and VHF on masts, and Shark hamsticks for HF. The hamsticks perform very well, and we are assuming the massive ground plane of the truck is helping, I really need to test this vs the other antennas I have to see how well they really do in a comparison.

One of the people that joined us brought a photography drone and it took the neat overhead orbital.

It took a bit to get bulkhead connectors, the system enclosure secured, and other details assembled, but it turned out well. I got Shark Hamsticks which are surprisingly good performers. The Hamsicks adapted well to the existing antenna mount housings on the front of the shelter and will be a great deal easier to get in operation then the dipole or DX Commander. I was using an IC7200 as a field radio since its made to be rugged, but since this set is sheltered, and in shock mounted case, using my preferred IC7300 should be fine. The LDG AT-1000 tuner has an antenna switcher, so I can put up 2 Hamsticks at any given time and switch between them. Next to the radio is a Raspberry Pi, which gets time from a Ublox GPS that is just outside the truck inside a capped PVC. The GPS does not get good reception in the truck, since the shelter is 2 layers of sheet metal. I included my Bearcat scanner, and an IC880H VHF set. I have these items secured with shock cord in their shelves, and the enclosure is shock mounted. I was able to do all of this without making significant modifications to the truck, it already had the holes drilled that I needed for 4 antennas and the GPS.

Hamsticks are above the drivers cab. VHF antenna is the taller antenna in the back, with discone on the other side. VHF and discone will be optional for a Parks on the air expedition, but will be nice to have for extended park stays.

Lake Perry campgrounds are very nice, but I haven’t seen the equine area until recently. It lacks the lake view but it very shady with large primitive camping areas. We took horses so that everyone would have something to do on this trip. I have taken the M35 out for a day trip, but this is the first full weekend run of the setup. Being able to just set up an antenna and power and just go is very nice, I am glad to not have to lug the batteries and radio into a tent anymore. I found an old military electonics case that fits everything perfectly and is shock mounted in the interior.

I set up an inverted v antenna since its marginally easier to set up vs DX commander, but signal reports were not as good as with the DX Commander. May just be conditions this particular weekend, but ill have to do a deliberate comparison at some point. It worked though, so its nice to have some options for various environments.

The shelter has black out lights (red light for reduced visibility) which of course isn’t really necessary in this environment, but it did cut down on the number of bugs flying around vs white light.

Not completely done with the setup yet, I need a better method of anchoring down the radio enclosure and probably some air flow. It didn’t get particularly hot this trip, but the radio and power supply is surrounded by cushioning and may warm up on a busy activation or using digital modes.

I found what appears to be an M185 shop on an M35 (deuce and a half) truck. Seems to be in good shape automotively, and the lights and power distribution in the van all work well. Previous use was an operations truck for the Wyoming National Guard based on the stickers and small commercial phone directory I found inside.

Is a 2 1/2 ton truck too much for hauling around amateur radio gear? Yes, but it will be a blast. Once the radio shack is put together, I wont have to lug around batteries and equipment. The shop has ample space to even be a camper of sorts. I am finding that many people convert these shop trucks to be campers, but my goal will be to approximate a military communications shelter.

Looking forward to getting a basic setup and getting out to the field for Parks on the Air.

Seeing no discussion on this, and no useable examples from any source, I thought I would share -a- way of doing this. This hasn’t stood scrutiny of inspectors, but it does what the Security Technical Implementation Guides (STIG) states:

“Review the external and internal Access Control List (ACL)s to verify that the router is configured to only allow specific management and control plane traffic from specific sources destined to itself.”

Which I read to mean that for each interface, there will be an ACL, and for traffic destined specifically to that interface, there should be filters. Doing this per interface is fairly unwieldy, so I am taking advantage of the Cisco object groups to make this less of a pain. Instead of a custom ACL per interface, I can make a widely reusable ACL and I only have to create the Object group unique per router.

To start, define the addresses assigned to the router:
#object-group network This_Router
#host x.x.x.x
#host (each address on your router)

This will contain host statements of each address on this particular router, you can use “show ip int br” to get this.

You will also need object groups for management networks, voice networks (if your router has a voice gateway that requires devices to talk directly to this router), scanning networks, and other sources that need to directly talk to the router. You also need an object group for your entire allocation for pass through traffic. From this, you can build a decently manageable ACL:

!
!
ip access-list extended STIG_RT000130
permit tcp object-group Management_Networks eq 179 object-group This_Router (routing)
permit tcp object-group Management_Networks eq 49 object-group This_Router (TACACS)
permit tcp object-group Management_Networks eq 22 object-group This_Router (SSH)
permit tcp object-group Management_Networks eq 1812 object-group This_Router (Radius)
permit tcp object-group Management_Networks eq 1813 object-group This_Router (Radius)
permit udp object-group Management_Networks eq 123 object-group This_Router (NTP)
permit udp object-group Management_Networks eq 161 object-group This_Router (SNMP)
permit tcp object-group Scanning_Servers object-group This_Router
permit udp object-group Scanning_Servers object-group This_Router
deny icmp any object-group This_Router fragments log-input (For STIG CISC-RT-000140)
permit icmp object-group Allocated_Networks any (Permits internal networks to ping gateways)
deny icmp any any log-input
deny ip any object-group This_Router log-input (this is where you deny anything not explicitly permitted fulfilling the STIG RT000130 requirement)
permit ip any object-group Allocated_Networks (permit flow through traffic)
permit ip object-group Allocated_Networks any (permit flow through traffic)
permit udp host 0.0.0.0 eq 68 host 255.255.255.255 eq 67 (permit DHCP requests to pass through)
deny ip any any log-input (STIG requires that all ACL conclude with this)
!
!

To test this you can put a “permit ip any object-group This_Router log-input” right above the “deny ip any object-group This_Router log-input” statement to safely capture what is triggering that rule (using show log or wherever your logs go), evaluate if you need it, and add it to the ACL if so.

A real ACL will be larger than the example and will include rules specific to your environment. You will also have to stuff other STIGs in this (like STIG CISC-RT-000140 in the example) since you can only have one ACL per interface in a given direction (eg ‘in’ which this STIG requires “ip access-group STIG_RT000130 in”)

Don’t forget to remove the ACL from your interface(s) (particularly the one you manage through) before modifying the ACL or you could block yourself since an empty ACL would be deny any any. Best to do these things after hours and start a session with “reload in 60” without writing the configuration so if this does happen, you don’t interrupt people working and the router will go back to what it was before the ACL when the reload happens.