Cobra Mesh Repeater

A friend asked if something other than a Cobra module could be used as a Mesh Repeater. I had played around with this a few years back. I did a quick retest to see if my memory was correct and if everything still worked on newer firmware levels.

In a nutshell, yes it seems to work just fine. It's a bit of a pain to setup and finding the right components in a rugged enclosure is not easy.

Here's the test I setup.

I had my 18R2 in one room.

I had a 36M in another room with the door closed and the antenna removed.

In this setup, the 18R2 could not talk to the 36M.

In the first test, I used 72M in the middle that would mesh to the 36M.

In the second test, I used my own Mesh Repeater in the middle that would mesh to the 36M.

In the third test, I showed that another 18R2 would NOT mesh since it was not synced to the same system.

Test 1: A normal 72M performing MESH to an unreachable mod:

Test 2: A non-Cobra Mesh Repeater performing MESH to an unreachable mod:

Test 3: Only a synced Cobra device participates in the MESH. Another 18R2 will not MESH to an unreachable mod:

Here's a picture of the device I used for the Repeater:

I have several SNAP devices I've bought off ebay over the years.

This SNAP DMX pro has a nice rugged case. They also have a SNAP RS232 SNAP LINKs and RS485 SNAP LINKs that look very similiar.

They typically come with an RF200 chip BUT it has a custom firmware on it, so you can't easily use it. (You can't see them via Portal so you can't change the firmware via Portal.) I just popped the chip off and put a normal RF200 in there that I could talk to.

Here's what a SNAP LINK Looks like:

(AGAIN, these won't work as is.)

I also have a couple of SNAP Connect E10's. They look like this:

The E10s have a normal RF200 chip in them that is ready to use, but it also have a mini linux computer attached to it. So it's a bit overkill.

(In theory you could use 2 E10s to extend a signal across ethernet. I've never tried it, but that's one of the big purposes the E10s were used for.)

I prototyped an E10 using the Cobra wireless signal to control some Merlin RS485 firing modules.

In all these cases, these devices require USB power and do not have a method to monitor battery levels.

Really all you need is the right chip and ability to connect the needed power to 2 pins on the chip. I just found it easier to use some devices that held the chip for me and handled the power connection.

In all my tests I used the Synapse RF200 (RF200PD1). This chip is no longer made. The newer version is the RF220. (This is what changed from the 18R2 rev A to rev B. Cobra moved to a new chip.) The Cobra modules actuallly use a CEL version of the chip. While the 18R2 (at least the A rev) actually has the normal RF200 chip in it.

I think the newer RF220 runs about $63 new. You sometimes see older Synapse stuff on ebay for less. There's probably some other chips like the CEL version that could also be used. Then you need to power it in an enclosure.

Besides the challenges of getting the right hardware, I had to manually configure the MESH and encyption key to match my 18R2. Each Cobra remote uses unique encryption key. It's not easy to get the key. As a courtesy to Cobra, I don't publically disclose how I get the keys. I will say it requires physical access. I haven't reverse engineered how Cobra syncs modules, and in most cases these chips don't have any displays or buttons which would make a normal sync easy.

So even though it's more expensive. Something like a Cobra 6M would make a great repeater. It's easily synced, you can monitor the battery usage, you could use it as a mod when not needed as a repeater and it's fully supported by Cobra.

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