Messages

1

General Discussion / Re: Where do you mount yours?

« on: September 07, 2015, 01:02:08 am »

The supplied DVB-T antenna can be cut down to 68.8mm or as close as you can. That gives a better tuned 1090mhz 1/4 wave antenna. If you put the tip in boiling water for 30 seconds, it can be pulled off.

Ideally, the cable leading to the Rx dongle should be a multiple of the 1/4 wave length to ensure the VSWR is as low as possible. That is an easy mod and in fact if you are going to use the DVB antenna in the cockpit you need to remove the magnet out of the base ideally. The bottom peels off, there is a metal plate with a small magnet stuck on. The magnet pops out. The plate can be prised out and that traps the screen (a ground plane supposedly) and you'll see the core soldered. Measure out and trim in multiples of the 68.8mm measured from the end of the plug.

I am initially going to stick the antenna on top of the case so will trim mine down to the minimum to cut down on cable clutter. When my other DVB produce arrives, it will be chopped down to mount inside the RPi case....

Trapdoor, the simple formula found in several places on the Internet for calculating the length of a VHF antenna gives 65.4mm for 1090 1/4 wave. Can I ask why you're suggesting 68.8mm?

2

General Discussion / Re: Raspberry Pi Model B (not +)

« on: September 07, 2015, 12:50:01 am »

Is this determined by Raspberry or PilotAware? Is there likely to be a solution in the short term? Presumably Pi 1 B+ will become in short supply now that they have been superseded by the Pi 2.

That'll be the Linux drivers for the Pi 2 build not PilotAware.  Will be sorted in due course I'm sure, and the first generation are still available in various places.

Thanks TJ80. Doesn't say much for the Raspberry claim that the Pi 2 is 100% backward compatible.

It's a pity because I see using the Pi 2 now as a way of 'future-proofing' against the increase in functionality that will almost invariably be requested of the PilotAware software.

3

General Discussion / Re: Where do you mount yours?

« on: September 05, 2015, 12:15:20 am »

For instance, would a pair of these work well enough for both the 1090mhz and 868mhz radios - I assume it would at least be an improvement on both the standard untuned items included as standard?

TJ80 is referring to a GSM quad band antenna. I know nothing of these things - is it a reasonable premise that an antenna designed for, say, 900 and 1800, will be pretty good for 1090 because it falls between these design frequencies, or are these effectively 2 antennae specifically for 900 and 1800 rather than the intervening spectrum?

4

General Discussion / Re: Raspberry Pi Model B (not +)

« on: September 04, 2015, 10:30:49 pm »

What I do know for a fact is that it does not currently work with the Pi2
There are some kernel drivers missing.

Is this determined by Raspberry or PilotAware? Is there likely to be a solution in the short term? Presumably Pi 1 B+ will become in short supply now that they have been superseded by the Pi 2.

5

General Discussion / Re: Where do you mount yours?

« on: September 04, 2015, 09:49:21 pm »

A paper with antenna guidance would be very much appreciated.

I definitely second that.

There are some cheap antennae on eBay which claim to be tuned to 1090. They look similar to the provided DVB-T antenna but with a pigtail coil in the middle. Are they likely to really be optimized for 1090?

I've read several tutorials on building your own 1090 antenna, but they look a bit on the ugly side for placing in an aircraft.