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DMR Simplex Contact

To date, I have only made 2 simplex contacts via DMR, with one being an arranged contact while at a hamfest for "local communication needs" and the other being an "eavsdropper" while at the same hamfest surprised to hear someone else using 446.075 Mhz , time slot 1, talk group 99. Both contacts were pretty close, at most a 1/4 mile away. Not earth shattering in the least.

National DMR Calling Frequency

446.075 MHz has been adopted by many in the US as the 70cm DMR Calling frequency along with the time slot and talk group parameters mentioned above.

A longer range test

I coordinated a test with Joe KD2AKU while he was at home with his Tytera MD-380 DMR radio with stock rubber duck antenna inside his house as well as outside in Staatsburg.

My location was ~40 foot above the tree line atop the Ferncliff Observation Tower, about 85-90ft above local ground level. I was using the same radio as KD2AKU with the same antenna.

What does it look like?

7.17 miles is not really that far for any record breaking test using 5W, but was a good test to prove the theory it should work based on elevation and topology in the area. Audio was crystal clear, I tried 100mW but was unable to make contact. The Tytera only has a high and low power setting. I "modified" my MD-380 for lower power than standard which is 2.5W at the low setting.

Here you can see the elevation in the area and possible geographic features that may have interfered with us.

Looks like my height is what enabled the contact to happen with room to spare.

And what did it sound like?

Firstly, it was super windy at 7:15 PM May 21st evening on top of the observation tower so it made it hard to hold both my cellphone camera and the radio with a focus of "DO NOT DROP" anything. Very short contact video. Try not to vomit. :o :o

Additional testing....

For those with a DMR radio, be sure to have 446.075 MHz programmed in your radio along with time slot 1 and talk group 99 and you never know who you will hear.

If anyone wants to coordinate a contact from your location to me next time I venture to the observation tower, let me know.

I would also like to explore text message sending which we could not do quickly during this test.

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