Thursday, September 24, 2009

Gearing up

Next month, I'm going to order a DVB-S modulator (for me) and a DVB-S receiver for the repeater.

Stefan (from SR Systems) says that you can set up a repeater simply by connecting the receiver directly up to the modulator. The modulator will turn on automatically when the receiver detects good reception. Not only that, but it has a "PTT" logic indicator pin that can turn into an open collector output with one transistor and one resistor to key the amp!

After that's done, the MPEG encoder board will be paired with the new DVB-S transmitter board as my user station.

The bad news is that they don't make a DVB-S receiver for 70 cm. Too bad. We'll have to receive on 1.2 GHz. But, of course, we'll be able to do so in a 2 MHz wide channel so we should not have the same interference problems we do with FM TV on K6BEN/R.

All I need besides that is a 15A power supply for the whole thing, a 23 cm antenna, some coax.... and a place to put it all.

For the receive antenna, I'm looking at the Diamond F1230A. It has 13.8 dBi gain. With about 3 dB of coax loss and 9 dB of loss for operating on 1.2 GHz, you should be able to use the PC Electronics ATV DX chart as it is - without having to correct for being on 1.2 GHz. Just assume that the receive site has unity gain. So, for example, if you can generate 5 watts into a Directive Systems 14 element loop Yagi, you'd be able to hit the system from about 15 miles away.

No comments: