I have been told that if you have radar and are using it then the beam is detectable by ships and therefore a reflector is not needed. Comments please.
If the beam is detected the other ships radar will get radar interference, curious patterns all over the screen. This does fotunately not happen very often!
Nope ! A radar beam from your boat will be "seen" by specialist radar DETECTOR kit, but it will not register on a ship's normal radar which only picks up return signals from its own transmitter.
(Barring occasional co-channel interference if you are unlucky to be near an airport, one of HM Grey Funnel line, Fylingdales, etc. !)
Seeing that you have started a post on radar and reflectors, I thought it might be valuable to share some observations that I have made.
When crossing the channel a couple of years ago in flat calm conditions, under motor, I was watching the radar, then matching the visual target from the deck, there was excellent visibility.
We were sailing, motoring, in company and there were also other sailing boats around. I began to then observe, with my bino's as best I could, the radar reflectors used by the surrounding yachts with the strength of the image on my radar screen. What was alarming was that our friends who had one of the tube type reflectors attached to their shrouds above the second crosstree gave a very poor image when compared to the larger reflector other boats had at the front of the mast.
Position of the reflector here is not so important, what is though is that the tube type reflector appears to be almost useless.
Presumably you mean the tubular type about 4cm diameter and 40cm long rather than the cylindrical Blipper type. It has long been known that the long thin ones are virtually useless; with their width virtually equal to the wavelength they cannot give a strong directional return. I wonder how they comply with the Trade Descriptions Act?
Amphitrite is totally correct. Whilst doing my apprenceship as a radar technician in the 70s, we used to see these patterns very regularly as radars "saw" each other. There is a technical name for these patterns but, alas, my memory fails me. The reason that these are quite rare nowadays, is that frequency stability of both the transmitter and receiver is much, much better now with modern technology but they can still occur if the right events take place. Any radar will receive the pulses from another radar if they are transmitting/receiving on the same frequency but whether anything is displayed is another story.