IARS 23cm simplex repeater update

  IARS 23cm Active beacon information and instructions

The Illawarra Amateur Radio Society Inc. (IARS)
is pleased to announce the testing of a Simplex Repeater operating on the 23cm band.
What
- FM Simplex Repeater operating on 1296.850MHz
- RF Power 25 Watts.
- Vertical Omnidirectional Antenna of 11dB gain.
- Input stage has a LNA with approximately +10dB Gain
Where
- Maddens Plains, Grid Reference QF55LR.
- Latitude: 34.27Deg South Longitude: 150.94Deg East
- Height: 371 Metres above sea level. (Not including the height of the tower).
Purpose
The purpose for the development of this particular repeater is;
To encourage interest and experimental development in the higher bands such as 23cm.
It can be used to assist amateur radio operators to develop their own station transmitters, receivers, RF amplifiers, pre-amplifiers and antenna design.
Test the operators experimenting with various modes.
It is a beacon which can be used to monitor propagation on the 23cm band.
Basic Description
The general principle of the repeater is that it is simple.
The transmitter stages consist of a 2 Metre exciter, followed by a transverter.
The transverter has an IF input of 144.850 MHz, up to, but no greater than 1.0W or else it may be over driven. The RF output is of the order of 2.0W. The next stage is the RF PA of 25W.
The memory of the controller chip has been programmed to function for a period of 150 seconds (2 ½  minutes) more than ample time to conduct any form of experimental test.
The antenna is a vertical omnidirectional antenna with approximately 11dB gain.
The control card was developed and built specifically by the IARS for this purpose with the microcontroller used to generate the Morse code and all the control for the simplex repeater.
The unique program code has been written inhouse and developed by IARS to suit this application.
This is all installed into a 19” rack 2U enclosure mounted in the equipment rack at Maddens Plains.
Operation of the Beacon
Approximately every 10 minutes a string of Morse Code will be transmitted from the beacon.
The interesting part of this Morse code is that it is part dynamic.
There are two values which are actively monitoring the unit on site.
The first is the Temperature inside the cabinet in degree Celsius
The second is the system voltage currently at the repeater site.
The Morse code message is structured as follows:
VK2RMP experimental beacon test QF55LR TEMP XX.X Deg. SYSTEM VOLTS XX.X
During the Beacon operation the Simplex section will not operate.
The beacon will not transmit whilst the simplex repeater operation is in progress and will wait until the simplex process is complete.
Operation Procedure of Repeater
It is a simple process after selecting the Repeater frequency.
It is recommended you wait for at least 10 seconds or press your PTT once for a short test, if a tail and beep comes back to you, you good to go.
If not, it may be that your signal is not getting in OR someone is using it on the input that you cannot hear.
Pressing the PTT quickly to see if it responds (similar to a duplex repeater tail) will not interfere with someone else’s transmission, as long as the PTT is quick, and not multiple times, this could be annoying for someone trying to record.
Summary : Onequick one second PTT should give you a Tail and a roger beep. If not someone is using the repeater OR your signal is not been received by the beacon.
If there was no response it may be good to wait for at least 30 seconds to see if the unit was in use before attempting the PTT again.
Once roger beep is received and you are ready to commence your transmission, it is best to operate the PTT button for about 1 second before speaking or transmitting data of pictures.
The reason for this is to stop any clipping at the start of the transmission. The repeater has a 0.5 second noise suppression timer to avoid false triggering.
CTCSS was not used to do this as many experimenters don’t have encoders fitted to the 23cm gear.
Once you release the PTT there is a one second delay before the recording stops and the current reception cycle is terminated, this is to allow for short signal drop off’s during your over.
Without this timer, a signal drop off may prematurely terminate your over and begin re-transmitting what you have just transmitted, whilst you are still recording, rather messy.
After this one second delay the repeater will commence to re-transmit your over. When the repeater has concluded your transmission you will hear an audible ‘Rodger Beep’ of approximately 750Hz.
It is after this Roger beep that a respondent or yourself may commence the next transmission. If you do not hear the ‘Rodger Beep” wait until you do.
Please make the transmission long enough to finish the job and short enough not to cause any others to be impatient.
Remember to be patient - including hearing the “Roger beep” - and avoid any difficulties.
When transmitting data modes such as RTTY or SSTV, ensure the transmission DOESN’T exceed the 150 second time window, because if you do, the signal will be unintelligible and fail.
Keep to the simple operating procedure and you will be able to enjoy our hobby that much more.