LOHAN tunes into ultra long range radio

Our Low Orbit Helium Assisted Navigator (LOHAN) Vulture 2 spaceplane has taken a massive leap in transmitting power with the installation of a mighty 900MHz ultra long range radio module - the RFD 900u Radio Modem by Oz's RF Design. the RFD 900 rig The diminutive module plugs straight into the Pixhawk autopilot, replacing …

[DaLo]

Slightly OT

How come http://www.theregister.co.uk/2014/04/02/lohan_rehab_tests/ does not appear in http://www.theregister.co.uk/Wrap/lohan/?

Tagging issue?

[Lester Haines]

Re: Slightly OT

Simple oversight. I'll sort it the next time I update the wrap.

[Mage]

900MHz

The 900MHz option is probably only USA. Illegal in EU.

900MHz doesn't exactly need LOS, but all UHF (400MHz to 1200MHz approx) has HUGELY BETTER range LOS than not. Obviously too the 470MHz TV gives better non-LOS coverage than 790MHz TV. TV used to be up to 862MHz.

In EU there is licence free SRD in 864MHz to 868MHz. But it's low power. (SRD = Short Range Device) similar to 433MHz allocation. The EU 446MHz allows more power but only with built in aerial walkie talkies, not random function devices such as 433MHz (usually wireless weather stations, door bells and IR remote extenders, such as back channel on 2.4GHz video senders).

In general there are few Radio transmitting gadgets that are able to be EU (CE) and USA (FCC) legal. Amateur Radio doesn't have to use approved equipment for full licence in most of EU so USA 420 to 450 MHz equipment can be used by Full Licence people in most of EU as long as they only transmit in 430 MHz to 440MHz band.

Note: Just because you can easily buy a transmitting gadget doesn't make it sensible or legal in your own country.

[DJO]

Re: 900MHz

The 900MHz option is probably only USA. Illegal in EU.

I refer the learned gentleman to the location of the proposed launch site.

[SW10]

Weight a mo

Was all this gubbins anticipated by the Southampton students?

I'm increasingly worried that the plunging/crashing tendency may supersede the soaring/navigating tendency.

[Tanuki]

ISM band allocation.

I do hope that Ozzie 900MHz radio is actually type-approved for use in ITU "Region 1" [Europe, Africa, the Middle East west of the Persian Gulf including Iraq, the former Soviet Union and Mongolia].

[Anonymous Coward]

Re: ISM band allocation.

Why?

From a previous article, the rocket motor can't be obtained/used in Europe, so the team are heading across the pond to region 2 for the actual flight.

[paulc]

I be worried...

about other circuitry being interfered with when this thing transmits...

[Lester Haines]

Re: I be worried...

Yup, we're thinking about that.

[Nigel Cro]

You're Gonna Need...

You guessed it!

... A Bigger Plane.

[JeffyPoooh]

Antenna could be better

Acknowledging that you probably *don't* want high gain and the associated high directionality (that may end up pointed away from you) for the mobile platform, but that said - the little rubber ducky antenna doesn't look all that good in terms of wasteful loss at 900 MHz. First thing to look at if you need "MORE POWER!!!!" (JC/TG).

If you can predict the geometry then you might be able to add some appropriate directionality (gain), such as a CSC^2 pattern.

The ground antenna could be a high gain Yagi-Uda antenna, if you're willing to aim it in the general direction of the vehicle.

There's also the concept of Good Enough. If what you've got works, then you're done.

[Anonymous Coward]

Transmitting Radio without Antennas == "silence"

Don't power up the RFD900 without both antenna connected. Radios powered without antenna can suffer irreparable damage!

[JeffyPoooh]

Re: Transmitting Radio without Antennas == "silence"

AC: "Don't power up the RFD900 without both antenna connected. Radios powered without antenna can suffer irreparable damage!"

Seems like an odd claim...

OEM website: "...it is OK to have only one antenna connected"

I had to go check, because it would be rather odd for a low power transmitter (1 watt in this case) to be using such a weak device that an open or short circuit would damage it. It's a flea, and it can't generate enough voltage (roughly 10) to hurt itself.

It's rather trivial to design low power transmitters to be indestructible w.r.t. loads *anywhere* on the Smith chart. Anyone that fails to do so should have a very good reason. Not just laziness.

[John Brown (no body)]

"a 3G dongle."

Probably a silly question, but considering you'll be launching from the back arse of nowhere, does anyone know if there is a 3G signal available there?

[paulc]

Re: "a 3G dongle."

I think you'll find that the radiation pattern of the 3G towers is aimed mostly horizontally ....

[Emty]

Nice new complications

Fascinating to see the project gradually change from garden shed engineering to something that starts looking like real work. A couple more steps down this slippery slope and Lester is heading a bureaucracy that will make NASA look like amateurs. You can do it Lester!

[Anonymous Coward]

Re: Nice new complications

I must admit that I skipped all of this until a few weeks ago. Usual: got bored, filled time spelunking El Reg, .... Whoops! So I really had to scramble to catch up. A very nicely done, real-world, engineering project. Good luck. God speed.