[1000mp] FL-7000 Amplifier

[Jim Smith]

Hi Bob,

First of all, if you use any rig at power levels higher than recommended 
by the manufacturer, I would expect you might have a warranty problem if 
you fry anything.

The amount of heat generated by a particular amp depends on the power 
level you run it at and the duty cycle.  If you put a 100W capable cw 
rig into transmit mode and leave it transmitting forever, the duty cycle 
is 100%.  i.e. it is generating a steady 100W without a break.  Some 
rigs are rated to handle this.  Many (like my MkV) aren't.

If you have a rag chew with someone on CW as there are periods (the 
spaces between code elements and words) when you aren't transmitting any 
power, so the average power will be somewhat less than 100W which means 
that the duty cycle will be less than 100%.

If you have a rag chew with someone on SSB the duty cycle will be much 
less than 100% as, because of the variations of the voice, the 
transmitter is generating an average power much less than 100W. 

Now, RTTY is kind of like the first example.  If you transmit 100W on 
RTTY, you are transmitting a full 100W during the entire time of the 
transmission.  So, during transmission, the duty cycle is 100%.

Well, you also receive, so the overall duty cycle will be less than 
100%, right?  Right.  But how much less?  When I'm running, my RTTY CQ 
message is about 7 seconds.  I listen for 3 seconds and, if no answer, 
another 7 seconds' worth of CQ.  This represents a duty Kyle of 70%.  (7 
out of 10 total, ON.  3 out of 10 total, OFF.)  This is still pretty 
high.  I might run the CQ message for 10 minutes without a nibble. 

My MkV is rated at 100W for RTTY (200W otherwise).  During CQWW RTTY I 
measured the temperature at an arbitrarily chosen point on the heat 
sink.  I was so horrified by what I saw that I cranked the MkV back to 
70W and ran the rest of the contest that way.

So, the higher the duty cycle number, the hotter the rig gets.  I don't 
know anything about the FL-7000 but I'm guessing that, if you run it at 
500W on RTTY, you will be able to fry eggs on the heat sink - but not 
for very long.

Hope this helps (even though it isn't what you wanted to hear).

PS Tnx for the Qs

73 de Jim Smith   VE7FO

 

Bob Stewart wrote:

>Hi All,
>
>I have the opportunity to purchase an FL-7000 amplifier to use with my
>FT-1000MP. My question is what power can it be used at for RTTY
>transmission. The handbook says 200W for RTTY. I am a RTTY contester and
>need 500W output - can the FL-7000 be used at this power level?
>
>
>Bob ZL2AMI
>
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