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SRM1000


Old, basic and simple, the SRM1000 was my first Tetra terminal. These are considered "first generation" and were designed in Cambridge. They were first used on the Dolphin network (now closed down) under the model number d120.

There are two main versions of this terminal kicking around on the second hand market > TT and TZ band.
The TT band versions are 380 - 400 MHz and are almost certainly ex-ambulance service.
The TZ versions are 410 - 430 MHz and are mostly ex - dolphin network devices.
SRM1000's are usually about 3 Watt's output in DMO. Whilst operating in TMO mode, they have the ability to have the output power controlled by the network.

These terminals (like most Simoco / Sepura terminals) can be re-aligned. This offers the ability to run increased output power whilst in DMO mode. The most I have seen from an SRM1000 is approx 20 Watt's on my analogue SWR/power meter. 2E1GXT has tested the same kind of radio with a professional, digital test set, and found the output to be closer to 35 Watt's. Video here.

SRM1000's also recognise the presence of DMO repeaters on a given talkgroup. They will receive calls FROM a repeater, but tend not to SEND calls through a repeater very reliably. It requires several attempts to get an SRM1000 to make a call through a repeater.
I suspect that the issue is merely a setting which requires adjusting, but haven't yet resolved which setting it is.

Car handsfree Kit


The car handsfree kit consists of a small microphone, a remote PTT switch and a small "jumper plug". All of these items plug into the rear of the control head. Whilst in this configuration, audio is routed to the loudspeaker which plugs into the main transceiver body. The jumper plug replaces the telephone handset on the rear of the control head.

The loudspeaker has an audio ground and audio signal. Audio ground is NOT power supply / chassis ground, so do NOT connect audio ground to ANYTHING apart from speakers or transformers!!

The microphone is the same.. so...  do NOT connect audio ground to ANYTHING apart from microphones or transformers!!

The PTT has +5V PTT and then a true, DC / power supply / chassis ground.

The practice of connecting mic ground, speaker ground and PTT ground together REALLY has to stop. It overheats the audio stage and WILL eventually cause damage.
 
Telephone handset


The telephone handset can either replace the jumper plug from the handsfree kit, and run at the same time, or entirely replace the handsfree kit. If you have the telephone handset plugged in at the same time, the audio is still routed to the loudspeaker until the handset is lifted from its magnetic cradle. At this point, the loudspeaker is muted and audio is routed entirely though the handset.

The same things apply to the telephone handset as the handsfree kit, so do NOT connect audio ground to ANYTHING apart from microphones, speakers or transformers!!







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