wiki/ news/ 2011-07-12 - Avionics team meeting

Avionics/communications - Video sub system

We went over the interconnection details of the video subsystem. Here is a drawing of the connections. Note that some of the shielded cable connections don't have their shields connected on both sides to avoid ground loops. The ATV transmitter has an SMA female RF connector. Frank needs to know the physical pin header connector details on the ATV transmitter. We thought it possible to just use the mating connector end that was removed from the packaging if we have a problem finding the proper connector.

Frank will make actual measurements of the curent draw of each component. Below is our conservative estimate so we can specify a DC-DC switching converter, which is on the critical path.

To estimate the ATV current draw, it was assumed the transmitter was 20% efficient, and puts out 1 watt of RF power. Usually the total power is only seen when a completely black raster image is being sent (true for FM modulation?) so this value is important to actually measure.

The WiFi amplifier also needs 12 VDC. Assume it puts out 3 watts also at 20% efficiency. So this conservative estimate gives is a 1.25 A load for the WiFi PA.

Here are some possible DC-DC converter solutions;

Requirements; Input: 10-20 VDC Output: 12.0 VDC @ 2.2A

945-1275-ND In: 9-36V Out: 12.0V / 2.5A 33 Avail - $83.28 for 1

945-1281-ND In: 9-36V Out: 12.0V / 3.33A 7 Avail - $102.32 for 1

Will need to fabricate a carrier board. There is a positive logic ON-OFF control.

Avionics/communications - Helix antennas

We found two COTS sources of 2.4 GHz helical antennas, and one COTS source of 5.8 GHz antennas.

2.4 GHz Helix antennas

WP Wireless Stub feed axial mode helix (Appears to be a Virginia Tech design) WPANT CP B R0 A0130 2 WP B 12-14 dBi / 40-45 deg HPBW $150.00 1-707-996-5201 Dan Paulson

Luxul Axial mode helix Tessco SKU 356035 13 dBi / 32 deg HPBW $124.95

5.8 GHz Helix antennas

WP Wireless Stub feed axial mode helix (Appears to be a Virginia Tech design) WPANT CP J R0 B0130 2 WP B 12-14 dBi / 40 deg HPBW $150.00 1-707-996-5201 Dan Paulson