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Hoe koppelde men 2 (of meer) AM zenders aan 1 antenne?


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1 uur geleden zei Rob Veld:

En schematisch voorbeeld:




The Diplexer as used to combine 963 and 585Khz in March 1985.



" To allow both services to be radiated from one antenna system, a "diplexer" had to be built. Although simple in theory, a diplexer to combine two high powered radio transmitters and match these into a single antenna is not a simple beast to design or set up. This is made even more difficult when operation is required on a ship, with the limited technical facilities and budget available. Within the components of the diplexer RF currents as high as 100 amps and 25,000 volts may be present so its construction is a feat of engineering. Following the introduction of this second service, the fifty was reduced to approx 27 kilowatts of power, and the ten was operated at about 7 kilowatts. Although there was a significant difference in operating power, the lower frequency of the english service allowed it to cover a substantial distance and in some areas coverage was improved despite the drop in power. Tests were conducted on 585Khz at times, presumably to test its suitability as a frequency during darkness, but no doubt also to increase the separation from RTE on 567Khz. However, following the demise of Laser 558 in November 1985 Caroline quickly adopted that channel and for the next few years was to go through a relatively stable and successful period."


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De periode (van testen) met twee zenders vanaf de Mi Amigo in 1975, die niet voldeden, pas in 1976 zou het wel goed gaan op een andere frequentie.



"After months of only being able to broadcast in the evenings, we were excited to learn that we were to begin broadcasting on two frequencies. Caroline was to be on 389 metres during the day and on both 259 and 389 metres in the evenings, from seven in the evening when Radio Mi Amigo closed down. At last, we assumed that we were going to be able to begin restoring Radio Caroline to her former glory as an all day music station. Chicago was in his element as he beavered furiously, building the diplexer to connect two transmitters to the same antenna and after a few weeks, he was ready to begin testing. These tests were initially performed at night when both radio stations had ceased normal programming, but very soon after, we were running both transmitters during the day. Radio Mi Amigo on 259; and non-stop music from Radio Caroline on 389. Despite our repeated pleas, Peter would not let us begin programming on the new frequency. None of us could understand why until we returned to England, only to find that the ancient 10-kilowatt transmitter used for 389, could only just be received on the south east coast barely eight or so miles away. The experiment at this time was a complete failure and tests were abandoned soon after and any ideas of daytime programming shelved, as parts necessary to get the transmitter working properly were either not available or not affordable. We were at our lowest ebb at this point. All Chicago's work seemed to have been wasted and our efforts and plans to make Caroline an all day station were, at least temporarily, dashed."





En zo ging het in 1973:  "Caroline 773 kHz with the 10 kilowatt transmitter fed into the vertical antenna ( power output 8 kilowatt).


 On 1187 kHz the 50 kilowatt transmitter fed into a 'sausage' aerial slung from the main mast to the aft mast, with a power output of 15 kilowatt."


(Offshore Radio Gerry Bishop)



Hoe het in 1966 ging bij Britain Radio en Swinging Radio England vanaf de Laissez Faire is weer een ander verhaal. 








Edited by Robin Westhof
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1 uur geleden zei Juul:

wat een zooitje...........................


Je moet daarbij denken dat in 1989 de Ross was 'leeggehaald' door de Nederlandse autoriteiten. Met weinig middelen heeft men weer een redelijk werkend geheel kunnen maken waardoor er nog een jaar kon worden uitgezonden. 


Ik heb geen foto's van voor de raid. Misschien Leendert?

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Ik ben bezig geweest om 918 en 1287 op 1 antenne te krijgen.

Dat lukte prima, maar ik was ontevreden over het bereikte resultaat.

Je hebt al een te korte antenne, dan gaan de natuur wetten een grote rol spelen.

Les 1 wat ik leerde was dat de laagste frequentie dominant gaat worden.

Met een te korte straler, 40 meter is te kort voor de 828 om als kwart golf te werken, zul je dus hier aanpassingen moeten maken.

En deze werken dan weer door op de hogere frequentie.

Het beste resultaat wat ik kreeg was 3 dB minder tov een perfect aangepaste monopole straler.

De verschillen onderling was m.b.t. de afstraling nihil geworden, wel beide met dezelfde power input.

in de normale wereld worden vermogens opgegeven voor het afgestraalde vermogen, niet op de input.

En juist voor de LPAM is het vermogen begrenst op de input dat beperkt je mogelijkheden om met het vermogen gelijke veldsterkte te krijgen.

Ik heb de 1287 afgestoten, leuk mee bezig geweest maar ik was niet tevreden met het verschil.



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