MMSSTV HELP · CHAPTER 07

Repeater Mode

Using MMSSTV as an automatic SSTV receive-and-replay station.

Help Home Getting Started Receiving SSTV Transmitting SSTV Modes Templates Logging Repeater

Starting repeater mode

MMSSTV can be started in repeater mode by adding the -r command-line option:

MMSSTV.EXE -r

The original documentation states that the normal MMSSTV functions remain available while repeater mode is running.

How the repeater works

  1. MMSSTV listens for an access tone. The historical default is 1750 Hz.
  2. After detecting the tone, MMSSTV returns a CW identification.
  3. If an SSTV picture starts within the receive timeout, MMSSTV receives it.
  4. After reception, MMSSTV can retransmit the received picture.
  5. The repeater can optionally transmit beacon pictures at intervals.

Repeater setup

Open Option → Setup repeater to configure the repeater. Important original settings include:

EnabledEnables repeater operation.
SQ levelAuto-correlator squelch threshold.
AnswerCW ID sent in response to the access tone.
ToneAccess tone frequency.
Tone det.Minimum tone detection time.
Answer waitDelay before CW ID.
RX timeoutTime allowed for the picture to begin.
Replay waitDelay before replay transmission.

Replay templates

MMSSTV can add callsign information, time stamps or other graphics to replay and beacon pictures by using stored templates.

Multiple template numbers may be entered, allowing MMSSTV to cycle through templates in sequence.

The original documentation gives 25,26,27 as an example: MMSSTV uses templates 25, 26 and 27 repeatedly in that order.

Beacon operation

Repeater mode can transmit a beacon image periodically. The setup includes beacon interval, silence time, SSTV mode, template selection and an optional image filter.

The beacon timer is reset when MMSSTV receives a picture.

Squelch protection

Before transmitting, MMSSTV checks whether the channel is clear. Squelch can cancel the CW response, prevent replay of a received image or postpone a beacon transmission.

Automatic SSTV beaconing can cause QRM. The original MMSSTV documentation specifically warns operators to pay close attention to the squelch threshold and channel activity.

Debug pane

The repeater debug pane shows the current operating state together with counters for CW answers, received pictures, transmitted pictures and beacons. It also shows the auto-correlator level used by the squelch system.

This chapter is based on REPEATER.TXT, added by Makoto Mori, JE3HHT, on 11 September 2001 and translated into English by JA7UDE Oba.
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