New VIC-1 / VIC-3 Intercom to Civvy Radio Adapter Design

[Augi]

After making a bunch of cellphone only adapters that don't pass the PTT signal that a radio would need to operate I decided to design and build a prototype adapter that allows you to connect ham radios in addition to cellphones to the VIC intercoms. The audio paths are selectable between 300 and 600ohms nominal which I expect will work with most ham radios, but being just a guy on the internet can't promise anything specifically. I don't have the time or radios to research or test even a fraction of what exists out there.

My new board hides in plain sight by replacing the guts of a VIC-1 C2298 crew box and it allows you to connect any combination of two radios or cellphones to your VIC system.

The audio and the PTT signals are all protected by a 750V isolation barrier so the 24V system will play nice with 12V and lower electronics.

There are a lot more and more expensive components here so I'll probably have to find a company to stuff the boards, plus I have to find a source of C2298 boxes. Because of that think these will probably be in the neighborhood of $300 if I make a batch of 20ea.

I will supply a pair of mating U229 connectors but the end user will have to provide their own radio-side connectors and assemble the cables and get their own cables to go between the adapter box and VIC head unit.

Please reply and tell me if there is any interest in these boxes. If I get a strong response I will start looking for parts.

Augi

 

[kml9705]

If I'm looking at your drawing correctly, one box would control 2 radios? I would be interested. I've been looking for a way to interface 2 Motorola CDM 1550 radios into the VIC-4 system.

 

[Augi]

You got it.

 

[Radiogeek99]

I would be interested


Sent from my iPhone using Tapatalk

 

[Frost0071]

Put me on your list.
Is it possible to get only the board? So that I can use my own housing.

Crap, I just ordered the cellphone only box a couple weeks ago

 

[humv33]

I'm interested too. Please add me to the list.

Sent from my SM-N950U using Tapatalk

 

[kml9705]

Augi, I have an extra control box for the VIC 4. I could send it to you to reduce the cost on my box a bit, if it will work.

 

[aleigh]

Can I ask who ran the PCB for you? I've got some unrelated projects I need to have boards made for, and that looks like some tidy work, and I presume they do low volumes.

The other thing I'll mention is I know everyone goes in for the isolation and the relays and everything for the PTT but I am not sure why this is necessary. It certainly is not with my VIC-3 and I don't think it is with the VIC-1 either. Tying a 12V and a 24V ground together doesn't matter - ground is ground. For PTT, the radio actually produces the positive power; the VIC simply shorts the radio-produced power on PTT. So if the radio produces 12V, it shorts 12V. If it produces 24V, it shorts 24V...

My VIC-3 is interfaced with my Yaesu FT-857D, straight, no EMI filters, relays, nothing, and it works great. The only "issue" is the mic output on the VIC comes out a bit hot (like lets say it's more like line level, but I have not measured it), so I had to crank the mic sensitivity down to the floor to get it to work well. I have a TODO to put an attenuator on the MIC channel but I haven't gotten around with it. So while this is lovely work - I am not sure what it's solving.

 

[Augi]

To the guys who are asking about alternative housings: I'd love to accommodate everyone but I have to order the boards as a single run so I can't make the multiple layouts needed to fit enclosures to order. The C2298 is a good compromise because it has exactly the right connectors and just enough internal wiring that I can cut it up and not need to buy extra. It's also the smallest form factor and the most reasonably available while still looking like a VIC component.

aleigh: I have been getting boards made at oshpark.com for a long time and I'm very happy with them on cost and quality. Turns are usually less than two weeks.

As to "why": There are several reasons in my mind.

Firstly is better safe than sorry. Ham radios are expensive and VIC systems are expensive. With the VIC 3 in particular, spares availability is hit and miss on the open market. A catastrophic failure of VIC or radio that takes out a couple of parts in my box is likely easily repaired. It's worth it to me if it saves another piece of equipment.

It's good to hear that that Yaesu plays nice and doesn't have any spurious emissions, but that's not necessarily the case with other radios. They weren't all designed with intercom use in mind and some are just better/more expensive/etc than others.

Also, it provides a good place to implement the audio level matching that a lot of radios will need.

Augi

 

[aleigh]

I just hate to read threads that suggest signal isolation and relays for PTT is somehow required, or that this cures the fact the intercom takes 24V. It is not required. Unfortunately there is a lot of this belief on the Internet. The prc68.com guy has his own interfaces which I'm sure you've seen which provide PTT and audio isolation, and there are plenty of other threads out there alleging this. radionerds.com states "Integrating the VIC 1 with other equipment is quite easy. There are some common connections that can be used. The biggest worry here will be to isolate the 12 volt radios from the 24 volt VIC-1, you can't simply hook these things together and expect them to not fry one another."

None of this is true, and just perpetuates poor station practices. Unfortunately we see this kind of half baked wisdom in the digital community a lot, where it has now become dogma to believe you "must have" expensive audio interfaces like the signallink or the rigblaster (which my friends and I refer to as the noiseblaster). As you know they are essentially what you have built here with the added component of an audio interface chip.

It might be true that if someone took a sledgehammer and then some hookup wire to a VIC-3 or VIC-1 they might get it to short the battery power to the PTT or audio signal output lines. Maybe the metal of the sledgehammer would do it. The VIC-3 doesn't run on 24V internally, and I don't think the VIC-1 does either but I don't want to say for certain for fear of being wrong. The VIC-3 is a modern electronic thing and regulates the voltage down just like anything else, probably 5.5V but I don't remember. I looked into all this years ago, reviewed the schematics, when I did the interface the first time. I too was terrified I was going to smoke one of the devices because of all the fuh fuh fuh on the Internet about it.

What you've accomplished is guarding against an incredibly amazingly desperate unlikely situation. If you're hunting to solve that, I hope you've also isolated the power feeds for the devices, who knows what could happen if the truck grounds float. If this sounds sarcastic, it's actually not meant to be:The Yaesu will smoke for sure in this example, my 857D and many/most of their radios do not have reverse polarity protection. As for the noise, if the radio is so bad that it's polluting ground on transmit so bad that it disrupts the vic-3, you need to throw that radio in the trash... A properly grounded installation (radio and VIC) is going to work properly out of the box. The VIC has all kinds of isolation in it already. Remember these were designed for use in vehicles, in harsh environments, in EMP scenarios. They are well made, well tested, well engineered, and were very expensive.

I guess the one thing I would want to ask is, have you ever had it NOT work when you just hooked them up straight? What was the scenario? I've owned and interfaced a handful of radios to both a VIC-3 and a VIC-1 and not had problems.

 

[Augi]

I'll mark you down as not interested.

 

[aleigh]

What I would buy tomorrow is a dust proof enclosure of any manufacture with the military and dust-proof audio jacks (neutrick?) pre-wired to screw terminal or push headers. In other words a breakout box with room on the inside to put another board such of yours, or of different purpose. You have to solve this anyways, and although there is some merit to recycling those old boxes, you could also just find a suitable hammond or whatever have the holes cut. There is real value to what you propose, it's just in the enclosure and mic channel attenuation, not the isolation, which is unnecessary.

 

[alphaseventwo]

im interested in one of these boxes Augi

 

[CUCV_ut]

Hi Augi. Please put me down for one of your new boxes. I'm very excited to be able interface two different TX/RX devices to the VIC-3. Thanks.

 

[Augi]

Will do.

 

[Augi]

Here's an update on this project:

I originally prototyped something with a lot of fancy isolation electronics but it was just too expensive. In order to get the cost down I had to go back to basics and remove a bunch of that. The box still works well for it's intended purpose which is to level-match the audio signals between the devices.

One of the audio paths is selectable between 300 and 600ohms which works for cellphones and I should work with most ham radios. The other audio path is 600ohms and is meant for ham radios only. But being just a guy on the internet can't promise which radios specifically will work or which won't. I don't have the time or radios to research or test even a fraction of what exists out there.

Each channel has an audio level adjustment pot so you can drop the audio level into the radio/cellphone and prevent over-driving the mic input.

This board hides in plain sight by replacing the guts of a VIC-1 C2298 crew box and it allows you to connect two radios or one radio and one cellphone to your VIC system.

I will provide the C2298 box with my board in it, a pair of mating U229 audio connectors and wiring instructions. You will have to provide your own radio-side connectors and assemble the cable. You will also have to get your own cables to go between the C2298 box and VIC head unit (these are standard cables).

The C2298 boxes are all used and have chipped paint and scratches on them. They aren't NOS by any stretch, but they aren't bad either. Most are CARC coated but a couple are OD.

The cost is $150ea + $15 shipping.

Augi

Pictures Attached.

 

[Augi]

The boxes shipped today. Everyone should get them in a couple of days. There is a printout of the instructions in the package, but if you want them in color message me your email address and I'll send you a .pdf.

Augi

 

[CUCV_ut]

My box arrived today. It looks good and I'm excited to give it a try this weekend. It came with the two plugs and instructions. I'll be wiring up one cable to go into a standard 3.5mm audio jack for the computer and another to a VHF ham radio. Once I have it ready I'll add some pictures. Thanks to Augi for coming up with another great device that fits right in with the truck and adds a much needed function. My wife was not so amused when she realized the "Bose sound system" was the intercom headsets. This should help make longer rides even more fun.

 

[CUCV_ut]

Does anyone have any ideas for combining the left and right channels coming out of a laptop into one mono channel for the intercom? I'll be using one of these adapters into a VIC-3 lite box. I've seen simple drawings where they run each channel thru a 1k ohm resistor to combine them. Others have gotten more technical and used an inverter on one channel so the signals don't cancel each other out. I've heard that windows 10 has a simple setting to change the output to mono. I'm still trying to decide between a Panasonic toughpad which will run windows 10 and an older Motorola MW-810 vehicle computer or a CF-19 laptop both of which would only run windows 7 which does not appear to come with a mono setting like windows 10. There is a way to install a third party freeware mixer application on windows 7 to funnel both audio channels out one, which may be the easiest way to get it going but involves extra software. How has anyone wired in their CD players / phones / laptops?

 

[Augi]

For the cellphones I have tied them together directly with fine results. I expect the computer will behave the same.

Augi