All this has been thrown together in rather short time. It surely needs to be sorted out, but I hope it is already interesting in its present form.
When I worked in Potsdam and lived in Berlin, I used to commute by double-decker "Sputnik" train on the line Berlin-Karlshorst = Genshagener Heide = Potsdam. The Berlin repeaters on 70 cm and 2 m are easily accessible from this stretch of tracks. I had a few nice contacts via DB0TA and other relays. Of course, I always chose a seat on the upper deck. Probably thanks to the inclined windows I could even hear one day the downlink of the AO-27 satellite with good signal strength. I also remember some nice simplex QSOs which I always prefer to repeater contacts.
Once every three or four weeks, travelling on the Interregio train Chemnitz - Berlin which until 1997 had one or two older cars, I talked to a group of hams in the Elsterwerda area on 145.525 MHz from about 15 to 20 km away.
During a stay in the UK 1998 to 2000, I just managed to contact two talk-in stations at radio shows from a train although I carried my old TH-75 almost everywhere (listening even on the Underground sometimes).Some excerpts from my logbook will appear on a separate page.
I haven't had a QSO from train to train yet, although I met a few road-mobile stations while travelling by train, and once, between Halberstadt and Blankenburg (Harz), I had a QSO with an aeronautical mobile station. Train-to-plane, anyone else?
I haven't tried yet other modes than FM, and other bands than 2 meter and 70 centimeter.
Unfortunately, almost all railway passenger cars in Germany and most in the UK have now tinted windows, and in many of them one can't even open the window any more. Only very few truly "radio-friendly" passenger cars remain, if there are any left at all. If you want to try a QSO from a train, look for the oldest cars (usually silvery or painted blue-beige) - your safest bet will be a museum train or a narrow-gauge line operated with heritage equipment.
To make a long story short, QSOs from new and re-built cars are almost only possible with stations near the railway line. Attaching the antenna to the (non-tinted) windows of the communication door at the rear end of the rear car may sometimes work better, but only in this one direction. In push-pull trains one is simply out of luck. The electronic equipment aboard many new railway cars can generate some very annoying noise, in particular on 70 cm, making QSOs even more difficult.
Train-to-train communication on underground rail systems could be most interesting in terms of propagation studies.
I summarize here some information which I obtained in e-mails from Tony Langdon, VK3JED:
There are a few amateurs in the Melbourne area who who regularly "play" radio on the train, often on 70 cm via repeater.
Melbourne underground railway tunnels are fairly deep (about 20 to 30 meters). The VK3RCC repeater, which is on top of a tall building in the centre of the city, can't penetrate the tunnel at all, except for a little bit at the ends.
Tony did train to train QSOs a few times, as well as train to tram, bus, or other vehicles. He used both FM and SSB on 2 metres. SSB gives a little extra range, but the noise can be more irritating. He also managed to work the SunSat FM amateur satellite from both a train and a tram. On SSB 25 to 30 km have been covered, the mobile station using a FT-290R with a quarter-wave antenna.
He recommends: "The best you can do is (1) use the best antenna possible, and (2) lower the frequency, 2 metres is the best band on these sorts of trains, leaves 70 for dead (when there's no tinting, the two bands are similar in performance, unless the windows are very small, in which case, 70 is the better band)."
There are rumours of a HF operation on the trans Australian railway route (Adelaide to Perth), which involved a setup which was equivalent to a top mobile station on 40m including external antenna. Perhaps the driver was a radio amateur. Nothing has been found on the WWW concerning this operation except perhaps a notice on http://www.fam.aust.com/ashton/rail.south.australia/pasgr.htm that an intended operation in 1979 had to be cancelled at short notice.