I’m not normally one to do much with “Go Boxes.” My general opinion of them is primarily that they have their place, but if it takes 2 people to lift it, and it can’t be operated without a manual, the value is diminished significantly. I’ve seen photos of some projects with multiple HF radios and UHF/VHF radios, and dozens of unlabeled connectors, that will be more of a hinderance than anything else.
Some of that “go box” crowd prides themselves on being flexible and having the technological know-how and gadgets to just make things happen. That’s great.. BUT there’s a balance. It needs to be clean and organized so it’s reliable and easy to operate.
I did another thing
So I built a proof of concept “go-box”.
A couple years back, I had put together a portable (public safety band) repeater in a plastic ammo box from Cabela’s. The design was nothing novel for the Search and Rescue team that I built it for, since they had been using that same setup for quite a while.
The basic premise included two CDM750 radios and a mobile duplexer in the case, along with a switching power supply in the bottom of the box. There were two punch-throughs in one side of the box; one for RF (obviously) and one for power. In my case, I have two power feedthroughs because there was a chance I was going to put VHF radios in the box, which would have required an external duplexer. In either case, I used type N connectors for my feedthroughs. In the image below, you can see the power connector, and an attenuator and load I was using for some in-house testing before I proposed this as a workable solution.
Power
The Amphenol power connector that was used had 5 pins; two for DC, and three for AC. The kit included two complete power cords – one for AC and one for DC, so that the two could never be inadvertently switched. The DC leads connected to the output of the power supply (and the AC leads connected to the input of the power supply). This configuration was designed by Dan Busse, who has deployed these boxes for years.
- A: 115 VAC Ground
- B: 115 VAC 60 Hz High
- C: 115VAC 60 Hz Neutral
- D: 12VDC High “+” *
- E: 12VDC Return “-” *
* I made a mistake when I put the connector together, so mine is backwards from Dan’s. I will probably try to fix it before I build a DC cord for it. A document from Dan outlining his configuration(s) is linked below.
For this project, I took the case, and power supply and replaced everything else. Here’s what I threw in there to be simple:
- Radio. Icom 2820H, because it was on my desk, and had a remote head, so the control head could be pulled out of the box.
- Radio hand mic and programming cable are included, but optional, as you’ll see below
- Power Supply: used a 10A, 12V “LED Light strip” supply from Ebay. That’s what I had in the box originally, and that’s plenty for a UHF/VHF 50W radio.
- Fuse block – fusing both AC and DC inputs
- Coax jumper to connect radio to the internal connector
- Headset. Plantronics HW710
- audio interface harness for radio & headset, including PTT jack (see below).
The Headset
I opted not to use a Heil headset,because they’re bulky, and cover both ears. In this case, having one ear exposed to have a conversation is key, and the Plantronics are lightweight enough to wear all day comfortably.
I chose the Plantronics specifically, because Dan uses them extensively, and they just WORK. He likes them, as it will directly connect to a dispatch PTT setup with the two-prong plugs for a console. This connector is often called a “PJ7”, and is also called a “B-gauge” plug and jack set, or “Longframe” connectors. Switchcraft and Neutrik still make them for a number of purposes including military users, telephone, pro audio, or, well… dispatch.
Using the Plantronics systems (either modular or PJ7) means any setups utilizing this equipment properly will be compatible with a majority of public safety operations out there. While I have the 2 prong JACK, I don’t have the PTT cable. I’ll be working on that next, as an option.
Wiring
The Headset I bought was an HW710, but HW510 (smaller boom), HW520 (510 with 2 ears) or HW720 (710 with 2 ears) will all work… plus others, I expect. I bought one with a “QD to RJ9” cable. All of those headsets have the “QD” connector, which also directly interfaces with that PTT button I don’t have.
the RJ9 has four pins – two mic and two speaker connections. So, I needed to find a way to connect these to my radio.
Source: https://bwsthoughts.wordpress.com/2016/12/02/plantronics-quick-disconnect-cables-pin-outs/
I bought 10 RJ22/RJ9 jacks with wires from amazon for $6 or $7. I then replaced the RJ11 connector in a surface mount telephone jack with the RJ9 (you SHOULD be able to plug an RJ9 into an RJ11, but the pins don’t always align properly). From there, I connected the radio’s speaker output to pins 2 and 3, and cutting an Ethernet cord in half yielded a cable that would let me connect the microphone input to pins 1 and 4, as well as exposing a ground and PTT connection so I could key the radio.
I had some trouble initially, and thought I needed to bias the mic or something – but that RJ11/ RJ9 issue got me. I spent a lot of time digging for answers on the headset, and found this reference, which told me what I needed to know – the mic is FINE for working with most ham radios… just watch for DC bias. Once I got the right connector, I got great crisp, clear loud audio.
https://k5pa.com/cs520hams/index.htm
For now, I have the surface mounted box, with an Ethernet cable coming out for mic and PTT to the radio, a speaker connection to the back of the radio, and an RCA jack available for an external PTT switch. I still need to work on how I want to do that, but I do have a foot switch on order, and there are a plethora of handheld pushbuttons out there.
Wrapping up the initial prototype…
What I did had a lot of positives that do make it worth expanding, even without the PCB mentioned above:
- Flexible – easy to adapt to almost any radio
- Lightweight, can be carried comfortably with one hand
- Fully self contained – just add power
- Still has some room for expansion
Here’s the final product – again, as a prototype. The box contains the hand mic, magnet mount, and programming cable. The power cord and headset (in bag) fit over the power supply, and there’s room to spare. This isn’t necessarily the IDEAL box for this type of effort, but it’s what I had on-hand, and was easily adaptable for this project.
Additional Accessories….
One additional item I procured was a “trainer” cable to keep in the box – this allows for two headsets to be connected to the same jack, and switch one of the microphones on and off. While it’s often used for training, it can also be used to have an operator and logger or two operators doing different things. These are $18 on amazon, so not a huge investment. The trick is making sure that they have a “long end” and “short end” on the headset end of the “Y”, with a switch on one leg. This allows the longer lead to be the logger or support person, while the primary operator is directly connected to the radio – and the support person can always HEAR, but won’t be heard on the radio if they’re talking while the operator is transmitting.
