Can I create a loop with hardwired DH+ and Radio DF1?

I have a pump house and a tank well over a mile apart. The pump house is hardwired to the tank via direct buried telco cable. Mind you this was done decades ago and the 2 PLC5 based stations have communicated over DH+ all this time and still do today. A 1785-KE module sits on one of them that has a DF1 radio attached to it. The lower PLC5 sends its info to the upper PLC and all data is retrieved over radio from the upper PLC. All this works fine most of the year. Each fall the first lightning strikes somehow induce into the DH+ cable enough energy to blow up the DH+ channels. These PLC'5 need to go anyway so a radio was going to be needed.

So with garlic around my neck I was able find the right combination of a licensed terrain hugging frequency, Bat Wings and a little Eye of Newt to make a RF connection on the lower station possible and it in fact works quite well.

So my question about all this pertains to MSG routing. While this is temporary I am curious... I now have 2 forms of communication media connected at the same time. I have verified that if I turn off one radio I can still reach both stations using the other radio's DF1 and then through some PLC routing magic through the DH+ wire to the remaining station. Leaving everything connected seems to pose no problems but I know I have created a serial loop. If this were Ethernet this would grind to a halt but it doesn't seem to bother the serial link at all.

So what determines the path the packets take when there are more than one path? Since everything serial on these requires a KE module... The PLC has to assume everything is on DH+. So what decides if a MSG gets sent to the radio via serial or DH+ directly?

I would guess it would broadcast out both ports?

And certainly DH+ is faster than RF but that doesn't mean that the radio didn't also send the packets and if true that will clog up the airwaves.

Am I imagining a problem that isn't really a problem?

I'm not totally sure I understand the architecture. A sketch with DH+ Station Numbers and a description of how the master station sends its messages over radio would help.

My guess is that the PLC is receiving both a message over DH+ and a message over DF1 and it's replying to them both.

You can configure a DF1 device to "ignore duplicate packets" but that applies only to duplicates with the same Transaction Sequence Number in the DF1 frame.

Port number in the msg instruction determines which path msg takes

I read in an old magazine that you tie 3 knots 6 inches apart and that would prevent damage. i never tried it.
i don't know where we bought these modules at but we have some dh+ to ethernet converters, there were also options for dh+ to Dh+ converters for isolation. i don't remember the brand name, i'll look and see if i can find the vendor. i used a device that went to ground. worked great unless you had a direct hit.
james

Probably 15 years ago I was rowing a four-day rafting trip down the lower Salmon River in Idaho, on an end-of-the-season float trip with a bunch of other river regulars. We were sipping tequila around a campfire at a place called Killer Goat Beach when a lightning storm rolled in and the strikes started up around the canyon rim.

I have never before, or since, been able to see the countours of a nighttime lanscape clearly WITH MY EYES CLOSED. There was nowhere to take shelter so we sat in the rocks in the sheeting rain and drank that tequila.

Hayden, Idaho is not too far from that river beach, and it's home to Transtector, who have earned my trust with lightning protection for industrial comms networks for that reason.

But I'll bet this system works because of the TNSW byte.

chelton: That was my initial thought too but the same port is used for both MSGs since everything at the 2 stations are DH+. The KE module rebroadcasts as DF1 for the radio.

Ken, James: I haven't tried the knots, but I have transtector modules on both ends. and still this happens. Someday Ebay is going to run out of PLC5/12's and KE modules and I will have to do this anyway.

Ken:
During all this 20 and 30 are frequently MSGing back and forth with updates for each other as they have for decades.

I can send a MSG from 10 to 20 or 30 and that works.

I can remove the radio at 20 and I can still reach 20 from 10

I can remove the radio at 30 and still reach 30 from 10

.. and I can leave both radios connected along with the DH+ and still reach everything... but having 2 paths for the comms with no way to steer the packets makes my spidey senses tingle... TNSW Byte ?

TheWaterboy said:

chelton: That was my initial thought too but the same port is used for both MSGs since everything at the 2 stations are DH+. The KE module rebroadcasts as DF1 for the radio.

Ken, James: I haven't tried the knots, but I have transtector modules on both ends. and still this happens. Someday Ebay is going to run out of PLC5/12's and KE modules and I will have to do this anyway.

Ken:
During all this 20 and 30 are frequently MSGing back and forth with updates for each other as they have for decades.

I can send a MSG from 10 to 20 or 30 and that works.

I can remove the radio at 20 and I can still reach 20 from 10

I can remove the radio at 30 and still reach 30 from 10

.. and I can leave both radios connected along with the DH+ and still reach everything... but having 2 paths for the comms with no way to steer the packets makes my spidey senses tingle... TNSW Byte ?

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So why not just eliminate the DH+ path and let 20 and 30 exchange info using 10 as the go-between? Requires a bit of new logic, but should resolve the "issue".

I can do that, and will have to when the PLC's get replaced, but in the meantime I am curious about the answer and there are some protocol gurus here that can explain it.

If it turns out to be a stable setup it provides a redundancy I wasn't aware was possible.
I don't expect it to be a supported topology but the Gurus will weigh in.