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Amateur Television (ATV) 

In mid-2015, MDARC converted the downlink transmitter of its ATV system to be fully digital. We are now able to transmit four channels of content in the same bandwidth that the old analog transmitter required. This also means that a digital receiver is needed to receive the MDARC ATV signal. Analog reception is no longer operational. Our uplink receiver can now handle both analog and digital, however. So if you are transmitting into our system in analog, your existing analog equipment will still work.

Check into the following nets on W6CX 147.06 MHz + 100 PL repeater:

Online Streams

System Outputs:

1244.50 MHz DVB-S

System Inputs:

The repeater's receiver provides multiple inputs for you to transmit into; four digital and one analog:

Digital TV Inputs:     1292.50 MHz DVB-S

                                   1273.00 MHz DVB-S/DVB-S2

                                       915.00 MHz DVB-S

                                      430.00 MHz DVB-S


Analog TV Inputs:    1270.00 MHz FM 

                                       Note: a PL tone is required to access the analog input, however it's not generally used and documentation is missing. 

                                      It will be updated as soon as we're able to verify it.

Receive Equipment

So what do you need to receive MDARC's DATV signals? Here's the minimum required items:

While our signal is DVB-S, MDARC recommends DVB-S2 receivers in preparation for future upgrades.

Club Member Will Roberts ka3vdt has some used, pre-programmed receivers available at

GT Media V7 or V8 (Amazon)

You may also need one or more adapters to convert from the antenna connector (usually an N-type) to the F-connector on the RG-6 coax or DVB-S2 receiver.

Transmit Equipment

If you are planning to buy or build an ATV transmission system, MDARC, You will need:

Depending on your setup, This may be enough to get in, MMICAMP2 and MMICAMP4, are good choices.If not, add the amplifier from below.

Note: Downeast Microwave used to make high-power amplifiers, Q5 Signal now does that. You can find older 2318PATV 18w around. 

Transmit Modulation specs



Note: Portsdown H264 uses PAL by default, and does not work. 

** You can use a single 1200mhz antenna, however a transmit/receive relay is required, and generally is not recommended. Two antennas allows for full-duplex video/validation of signal into the repeater. Example relays are microwave-rated SMA relay from Teledyne or Ducommun/DB Products. 

These are available on Ebay - You will want a 12v version. 24v will not switch on 12v. Most of these relays are rated for 25-30w @ 1.2ghz.

*A word about the Portsdown system

The Portsdown system was developed by the BATC out of the UK. It's designed around a PCB connected to a Raspberry Pi with an external PLL. The pi takes video from a USB-based capture device or a Logitech C920 webcam and modulates the signal from the PLL to generate a RF signal in the specific band requested using DVB-S.  The original design has multiple bands, most are not available in the US, and uses PAL not NTSC. 

Since the initial design of the Portsdown a lot of the hams in Europe have moved over to doing DATV on QO-100. Development on NTSC/US-based features has fallen behind, including the use of the Portsdown encoder board. Most UK users now use a Lime or Puto SDR. (Pluto is preferred)

Due to this the MDARC community runs a older version of the Portsdown software code. If you have one of these modulators DO NOT CONNECT IT TO THE INTERNET.

To help with this, Fred WB6ASU re-designed the board to be only 23cm/1200mhz to ensure we have a working board. There are a limited number of them; and it requires surface mount soldering to make. 

If you want assistance, please reach out on the MDARC DATV group

More Information:

MDARC Digital ATV Repeater Block Diagram
Note: This diagram is from 2015, when the system was built. Some items have changed over time