One beans place in space.
Ok, so if you haven’t figured this out already, I really like microwaves and other RF emitting devices. What I never thought of before however is how to measure the speed of light using a microwave.
Mr Hood (a friendly English physics teacher) shows us exactly how to do this in this article. Certainly a case of thinking outside the box 
For a while now I’ve been hanging on to a working version of pcrd – the linux control program for Icom PCR-1000 scanners. This version will compile with the latest gcc based distributions and work on all known Linux distros. You can find it here. It seems to work well here – the only issue I encounter is sometimes getting the unit to turn on – however after that, it tunes fine for as long as it’s turned on.
If you do notice any problems with pcrd, feel free to let me know – I’ll see what I can do about them. I want to add DSP support, but I don’t have the needed details to do this as yet, so it’s on the todo list.
Damn. I’ve been playing with radios for years, and I have to say, these units are sweet. I’ve been trying to think of things that can be improved on them, and failed. The radios can do free-input text messages between units, and even allow a lead-in delay for sending 1200/2400 baud FFSK data through standard analogue repeaters. Best of all? It actually works.
So lets see, it’s a Dual mode radio (Conventional/Trunking), 1000 channels, free form text messages, Voting, scanning, excellent RX sensitivity, great RX/TX audio, 25W output (selectable via software – no winding screws!). The actual unit is basically a huge DSP. I like it. Details of the units can be found here at TMC Radio’s site. I’m still looking for things to pick on the radios for – so I can submit feedback for improvement, but it’s not easy!
It’s been a busy last few weeks, so I thought I’d do a quick update before heading off to work (yes, working 7am on a Sunday should be illegal!). I’ve decided to splash out on the radio front and replace some of my aging PRM80 radios with new SRM9000 series units from TMC Radio. The specs on these units are great! They will even do radio to radio SMS messaging on simplex or duplex channels Should be a heap of fun to play with.
I got my cable going – One interesting thing that I did find however is that the PRM8030 radios really don’t like being hooked together with modem boards installed! Radios would key up without any activity, and just stay transmitting a carrier until the cross band cable was removed. I did some mods to the cable to allow LEDs to show which radio is transmitting, as well as a switch to enable/disable the cross band mode. After a bit of trial and error, this now works! I also had to install a relay to stop the mic audio being cut out even when the cross band was off!
On the wireless front, I will be doing a presentation on OpenWRT running on Linksys WRT54GS hardware at the next Melbourne Wireless meeting. Showing off a captive portal I have made which authenticates valid financial members of the group, and then allows them to use the internet connection free of charge. Nifty! There will also be a presentation on OSPF routing and a demo of this working via wifi at the meeting.