On 10/9/2013 6:35 PM, peter chadwick wrote:
Roger,
It just so happens that at 1345 UTC this Saturday, I'm giving a presentation at
the RSGB National
Convention entitled 'Spreading the Sewage' - we didn't think that
'Spreading the S**t' was quite
appropriate! I need to make sure that I have at least 2 if not 3 pints
of beer available for
refreshment during the 45 minutes - although the other year, someone
wrote to the RSGB General
Manager afterwards to complain about me drinking beer during the
presentation and livening it up with
a dirty joke!
I have analysed the QST reviews of 123 transmitter/transceivers since 1973 for
this, and the
frightening thing is the way that while tube rigs in general had
negligible 7th, 9th, 11th order
IMDs, the solid state rigs do - and then some. Both the FTDX5000 and the
FT1000D running in Class A
are good.........but, I gather get hot.
My 5000MP only gets warm if kept at 75W. Of course in class A reducing
power will cause more dissipation and thus more heat.
As they say in Yorkshire "Tha don't get owt fer nowt".
Yah know, I actually understood that. <:-))
Now many years ago I knew a rather cute gal from near London...At times
she sounded like a foreign language.
The results make me glad I still run a tube PA transceiver!
It's also one of the reasons I'm interested in QRO via tube.
I see lots of "claims" about the IM out of some of these new SS amps.
They don't appear simple and they are expensive! <:-))
What I don't understand is all three of the major manufacturers have
rigs with receivers that have sensitivity and dynamic range far in
excess of being useful on the low bands
What good does 120 db dynamic range, sharo selectivity, and sensitivity
at least 3 times greater than the noise floor do when you are on 160,
75, or 40 and the guy 5 up is 15 KHz wide? His signal is in your pass band.
I think it was on the FTDX5000 group a few months back. There was a ham
complaining about that specific situation. He couldn't understand why
his state of the art receiver was hearing this 20 over 9 signal 5 up
when he was trying to copy a weak signal.
Many tried, but I think he still blamed the receiver and that situation
will continue to exist until they clean up the transmitters. Being as
we went through several decades of relatively inexpensive bipolar rigs I
don't see that happening any time soon.
Seems like I read the new 990S from Kenwood is in the low 40s for IM3.
Of course you probably realized this is one of my "hot buttons" long
ago.<:-))
Good luck on the talk.
73,
Roger (K8RI)
73
Peter G3RZP
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