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.

The M37 isn’t done, but its been awhile since I have gone on a Parks on the Air trip so I loaded my pickup and the M101 and headed to Perry State Park, KS. In keeping with the Korean War era schtick, I brought a Remington typewriter and logged contracts with it. Not really efficient compared with using HAMRS or some logging program, but it worked and it was fun to do. In thinking about how my setup is coming together, it occurred to me that it is similar a RATT Rig (Radio Automatic Tele Type) in purpose, being an HF station at least. I remember the RATT rigs from the 80s/90s as a battalion long range communications setup (Bn <-> BDE), with FM/Wire serving the Bn <-> Battery/Company layer. We didn’t have tactical IP networks back then. I found a website, Rattrig.com, that shows an M37 setup which it pretty neat. I don’t think I will do the shelter part, but I think I can approximate a realistic role for an M37 as an HF station. People do use RTTY (the data transfer mode that RATT Rigs use) on the amateur bands so perhaps I can get a few contacts in that mode in upcoming POTA trips.

I used the TA-312 a lot while on active duty, really quite a whole lot. At the time I really didn’t appreciate just how useful and rugged these phones are.

The US Army recently removed these from inventory (last decade or so), which I think was a mistake given what they can do. They provide reliable communications for an area and do not give an interceptable signal like radios do. They are compact, can take a beating, and are quite simple to understand. I found a pair of these recently and decided to pick them up. One of them had a ringer that wouldn’t ring, so I did have to do some repair.

Despite using these phones extensively, I don’t believe I have ever seen the inside. I took my time, consulted what info I could find on the internet (including Signal Center | U.S. Army Signal Corps field telephones and switchboards) and identified what I needed to fix the phone with a broken ringer. The ringer is part “Buzzer BZ-23/PT” and is held in place by the 4 external screws and a small pin connecting the ringer assembly to the ringer volume control knob. There are two wires that require solder connections as well and are color coded so it is clear what goes where. This job looked intimidating at first, but was actually quite straightforward with patience, lots of photos, and referencing the SignalCenter website.

I got handset spaghetti cables and other miscellaneous parts from SignalCenter.com and the ringer/buzzer from Fair Radio Sales – Electronic Military and Industrial Surplus.

Replacing the handset spaghetti cable took some patience, but also was fairly straightforward to do. I took lots of photos but the individual cables are color coded so it actually wasn’t hard to do at all. The spaghetti cable has a small hook on either end that prevents the cable from backing out when it is pulled on. Fishing the small cables through the handset and phone body was not as difficult as I expected.

I don’t anticipate these phones being incredibly useful for amateur radio events, but they should be a very interesting addition as part of the overall setup I have when people visit the station in the field.

Thank you to Signal Center | U.S. Army Signal Corps field telephones and switchboards for the TA-312 information and parts and Fair Radio Sales – Electronic Military and Industrial Surplus for the “buzzer”.

I rarely saw the H45 on active duty, and when I did it was in the GP Small or medium tents. I have an M1950 Yukon stove same as I used with the hex tent on active duty, but with liquid fuel (diesel/mogas). Burning wood in the Yukon does work, but it takes frequent fire maintenance and it is difficult to manage temperature output with it. I also found coal to be difficult to burn in the Yukon, it just really isn’t set up to do this. Coal would be nice as a compact and long burning fuel.

I have seen the H45 on sale quite often, so I ordered one. The stove itself wasn’t much, but shipping for the large crate was expensive. The solid fuel component I was unable to find for sale anywhere. I had one made and I am happy with it, even if it’s heavier than the original.

My main worry was that the H45 would be too large and put out too much heat, but was pleasantly surprised to find that temperature control is much easier and even with the H45 vs Yukon. It is bigger than the Yukon, but in height and not really length so I don’t lose floorspace using it.

Using coal as a fuel works very well, with very long and even burn times, well beyond overnight without messing with it.

Ill keep the Yukon of course, it is more compact and easier to setup, but the H45 works well in an M1950 Hex tent and I expect ill use the H45 for most of my winter camping.

The original horn in the M37 matched its original electrical system, 24v. If you have a converted M37 there really isn’t a 12v horn that directly replaces a failed horn. On my truck, there is a modern 12v horn concealed that works out, but I wanted to use the original part if possible. The original horn was corroded in the interior, so this ruled out using a 12/24v converter. Vintage Power Wagons sells the 12v HYF-370 horn, which does fit in the MX-4003-UT housing with a bit of fitting.

The screws holes holding the HYF-370 together need drilled out a little to fit, and the HYF-370 came with a gasket between the two halves so I used a small amount of permatex with the gasket to compensate for the slightly larger holes. The original horn housing is held together with a large hand turnable part (below) which the HYF-370 does not have a hole for, but it does have a bolt shaft in the center so a metal dowel works to hold the thing together. Shaping and tapping this was fairly straightforward, I used M8x1.25 and 10NF32 taps, but I am not sure how consistent this would be.

I put terminals on the wires, soldered the other end to the douglas connector, hooked it up and it works. Sounds appropriately truck like, even if it likely does not sound exactly like an original.

If you have an M37 with 12v, and your horn isn’t working, this is one way to get this working and still look mostly correct.

Found a manpack harness at Apex Gun Parts Gun Parts & Accessories (apexgunparts.com) who seem to have a wide selection of various parts. The WWII era belt was from Overlooked Surplus in Leavenworth, KS Overlooked Military Surplus (wwiigimilitarysurplus.com). Overlooked Surplus has a very interesting selection, and I will definitely be stopping by there more as the budget allows. They have an old field desk of particular interest to me.

The painting was done with stencils I made on a Cricut machine, which did ok but difficult to work with the tiny lettering needed. I got it, but it took a couple attempts. The ORG | CH table above the dataplate I assume was for operators to jot down frequencies of units they worked with. Small space to write, however, no idea how practical this was in the field. The other marking was “Pointer Adjust” and the nearby dial does move the frequency dial needle. I assume they found a known stable frequency and adjusted the needle to match that. These radios were continuously tuned, as opposed to later PRC-25/77s or modern SINCGARS where turning the tuning dial stepped a set amount of kilohertz.

Pretty happy with the final result and it is now ready to go in the truck when it gets back from service. I still have to work out the antenna and mount, since the installed antenna wont work well with 2m radio and the flex antenna stuck on the radio isn’t hooked to anything – it also is tuned for MIL frequency range. The flex antenna does look nice though. For the vehicle antenna, which will connect to the BNC Aux antenna connector, I am looking at a Firestick 2m type which should look similar or at least not too out of place. It comes in black and the conductor is spiraled over the fiberglass whip, but hopefully is fine after paint.