New Repeater Configuration

I have been looking at various configurations for the new club DMR repeater. It would be great to combine DMR operation on the Brandmeister network with some implementation of AllStar Link as well. The Hytera repeater is unique compared to a Motorola TRBO in that the Hytera has a vocoder with analog input and output. There is a DB26 connector on the back that has two analog RX outs for timeslot 1 and 2 audio. In addition, there is an analog TX mic input and separate PTTs for both digital and analog TX. Several status outputs indicate when a valid DMR input or COR, CTCSS/CDCSS is received. Also, several pins can be programmed by the CPS for a variety of I/O functions.

The first experiment was to try using AllStar over DMR. That is to transmit and receive via a DMR radio into the repeater, and use the analog in and out to drive a URI/Raspi AllStar interface. A TG with the repeater id was programmed as the TX contact on TS2. Incoming calls on that TS were both re-transmitted by the repeater, and forwarded to AllStar over the network. Similarly, network traffic from AllStar keyed the Hytera’s TX and was transmitted out as DMR on the programmed TG on TS2. Even DTMF passed through the AMBE2 codec and could control and link remote AllStar nodes reliably. The problem was that there was no way to filter TG’s at the input of the repeater and use it for other Brandmeister traffic on that TS.

The second experiment used the mixed-mode feature of the repeater. The Hytera’s controller can automatically sort analog from digital reception into the RX. The questions were whether it would support external control in the analog mode, and how the multi-site connect network connection (needed for Brandmeister) would function in mixed-mode. With some judicious programming in the CPS, the results are very good. With the current settings, the analog mode relinquishes control to external PTT and CDCSS signals and the DMR mode works normally as well.

In the mixed mode, the AllStar audio quality is higher since it only passes through one codec. An interesting side effect of this configuration is the fallback to internal control if the RasPi crashes. When external control is lost, the analog repeater still functions in a basic mode with the build-in logic. Just as long as the Pi or URI does not fail in a way that holds the PTT activated, in which case the repeater’s TOT would need to kick in.

So the results with the mixed mode look most promising. Every contingency with mode conflicts has not been thoroughly evaluated yet though. So testing will continue. Additional control is also possible using GPIO lines present in the URI that can be activated by way of DTMF commands in AllStar. Several more features are available via programmable pins on the Hytera’s I/O connector that could be manipulated, if need be. Hang times for both modes are also adjustable.

Dave, K7DMK