And some of the reflected power ends up as
"waste heat" in the final and tank circuit.
Sent from my iPad
> On May 24, 2017, at 23:15, Vic Rosenthal <k2vco.vic@xxxxxxxxx> wrote:
>
> Everything Ron said is correct-- except that when an amplifier is generating
> 1000 watts and feeding an antenna through a line with an SWR that results in
> 100 watts reflected power, the usual SWR/power meter will show 1100 watts
> forward and 100 reflected. A meter like the Alpha 45xx has the option of
> computing "delivered power", which is forward-reflected.
>
> In the situation described by Bill, the actual power generated is 900 watts,
> and the antenna will radiate 900 watts less the losses incurred. The multiple
> reflections of a portion of that power are what cause the additional losses
> due to SWR.
>
> Don't believe this? You can test it. Transmit a given power into a 50 ohm
> load and note the reading. Say forward power is 10 watts and reflected is 0.
> Then change the load impedance so there is an SWR greater than 1:1. You will
> note that forward and reflected readings will both increase about the same
> amount.
>
> Vic 4X6GP
>
>> On 25 May 2017, at 2:46, Ron Youvan <ka4inm@xxxxxxxxx> wrote:
>>
>> Bill W6WRTTurner wrote:
>>
>>> There is something I don't completely understand about the effect of
>>> SWR on an amplifier. Perhaps someone here can clear it up?
>>
>>> Let's say my SWR meter indicates 1000 watts forward and 100 watts
>>> reflected.
>>
>>> 1. Does this mean the actual radiated power from the antenna is 900
>>> watts?
>>
>>> 2. How much power is the amp actually putting out - 1000 watts or just
>>> 900?
>>
>>> 2. If the answer to #2 is only 900, why does the SWR meter indicate
>>> 1000? Is that a false reading caused by the actual 900 added to the
>>> 100 reflected? If so, why does reflected and actual power add to
>>> produce a false reading?
>>
>>> After 60 years in ham radio I suppose I should know this stuff, buy I
>>> must have been absent that day. :-)
>>
>>> All comments appreciated.
>>
>> Do not worry about the confusion, it is all too common among HAMs even
>> highly seasoned ones, to get this wrong.
>> You will soon here the opposite of the following here, but they are
>> wrong.
>>
>> The amplifier outputs 1,000 Watts.
_______________________________________________
Amps mailing list
Amps@xxxxxxxxxxxxxx
http://lists.contesting.com/mailman/listinfo/amps
|