Hello guys, now a few answers.
JohnNL: I can’t remember the 10kW being use during bad weather when I was on board, but
it may have been. I don’t know when the 10kW arrived, but certainly by 1972.
JohnNL: Contact Chris Edwards of Offshore Echos. He or François Lethote just might have a back copy. The article, with photographs, originally appeared in Shetland Life monthly magazine.
Freddie: I thought that the Brown Boveri, when on 9935kHz, sounded best.
Another Anorak: A lot of engineers of that era disliked Ampliphase preferring Doherty transmitters such as Continental. But Peter Chicago worked with both on the Mebo II and the Mi Amigo and he chose Ampliphase for the Ross Revenge, possibly because it was cheap.
Freddie again: I don’t know where the RNI 100kW was built. All the RNI transmitters were second-hand (probably not previously loved). All the 1960s offshore Ampliphases were new and all were built in Italy: 50kW and later 10 kW for Radio London, 2 x 10kW for Radio Scotland, 10kW for Radio 390 and 10kW for Radio 270.
A clarification: when I said “I have never heard of Ruud’s information from Nico Steenbergen that half power was used when there was too much salt spray or salty water in storms”, that did not mean that it did not happen, just that no one mentioned it when I was on board. However I am still not sure reducing from 35 to 17 kilowatts would have made that much difference, but maybe it did. Radio transmission is a black art. 
Previous Message
Ian can give you full details of the technical set up on the Mebo and the history of the RCA rig. He was there after all. Previous Message
AA You may be correct there in your summing up - I believe the RNI Ampliphase, was the 100kw version, so it probably suffered even more from low power distortion. It must have been made for export from the USA, as 50kw was normally the max that could be used in the USA.
I believe the 50 on the Ross, was never run at more than 35kw -to extend tube life & to conserve fuel. Though is might have been a bit more when they first started.
I'll bring this thread to Alan Beech's attention, he might be able to enlighten us, further. Previous Message
Im not a TX engineer but my understanding is that RNI used an Ampliphase transmitter like several other offshore stations did and the RCA Ampliphase system has to be set up accurately and the antenna has to be matched well to the transmitter.RNI often sounded distorted on Medium wave because the antenna was not a good match to the transmitter giving a fair bit of reflected power (SWR). This presumably was due to the antenna originally being built for 1610 KHZ but the station changed frequency a number of times to lower channels - especially during the jamming.These lower channels were a fair bit lower than the natural resonant length of the tower on the Mebo 2 and presumably they did not modify the matching coils and capacitors enough to compensate fully.
The Ampliphase transmitters also tended to sound distorted if run at much lower power for some reason. The one on the Ross did as well when they turned it down to save diesel or in rough seas.
A TX engineer will likely be able to give more detail on these factors.
on 3/5/2023, 8:11:22, in reply to "