Specifications
Bravesemo!
This article should be COMPULSORY reading for hams getting their 1st Amp. Wayyyy too many hams fall into that old
contester credo....."all knobs to the right"!
W9WHE
RE: Less I
S more!
by KE1MB on February 8, 2005 Mail this to a friend!
Less is more... Try to explane to some people that a watt meter takes into account all of the power comming from your
xmiter. And not all of that power is comming from the fundemental either. Amost all devices come with a spec sheet that
tells the user at what point the best IMD preformance can be obtained. This is where I believe the device should be run.
For example the famious 2SC2879. This device has a IP3 of 60db or better when run at half power. That means eight of
these devices with maxium output rattings of 120watts each, should only be asked to produce 500watts.
R
E: Less IS more!
by AC0H on February 8, 2005 Mail this to a friend!
<<"For example the famious 2SC2879. This device has a IP3 of 60db or better when run at half power. That means eight
of these devices with maxium output rattings of 120watts each, should only be asked to produce 500watts.">>
My newly built K2/100 uses two of these in the KPA100 final stage and is rated @ 100W so the finals are derated 50%.
Some will argue that ALC isn't neccesary if you know how to tune an amp. Some people just can't learn to keep their
hands off that load control for adjusting the amps power out. All fine adjustments to amp output should be done with the
power out control on the Transmitter/Transciever.
RE: ALC Adjustment Procedure
by W5AOX on February 8, 2005 Mail this to a friend!
The biggest problem with this article, Alan, is that those who need to read and follow this procedure the MOST will blow
right past and ignore it.
"... This doesn't apply to ME, I know what I'm doing..."
"..I've been QRO for Yo-these-Many-Years, I ALREADY know what I'm doing..."
"ALC? I think I got one of those knobs somewhere in back of this thing... I ain't got time to mess with such nonsense...."
Another trouble: If DX or rare ops would refuse to respond to distorted splattering it would be a good thing. That would
leave them with fewer dawgs in the pileup though...
Jim W5AOX
RE: ALC Adjustment Procedure
by WB2WIK on February 8, 2005 Mail this to a friend!
Nice job.
Problem is, of course, that many things make operators sound terrible on the air, and overdriving amplifiers is only one of
them -- probably not the biggest one, either.
I worked a guy on 40m SSB last night who was barefoot with an IC-706Mk2G (normally a pretty good sounding rig), and
he sounded terrible. Very overdriven, overmodulated sound; could hear every breath, the door bell, the telephone -- way
too much background noise, and lots of distortion. Evidently the mike gain was (I'm guessing) full "up," and didn't need to
be. Sounded just like somebody horribly overdriving an amplifier, and he didn't even have an amplifier.
I just wish people would listen to how they sound on the air as a requirement prior to making a first contact.
I also wish people were required to use two good wattmeters prior to making their first contact using an amplifier. The first
meter should measure exciter power and be in the "input" line to the amp. The second meter should measure output
power and be in the "output" line from the amp. Apply a CW drive signal and slowly increase drive until the output meter
stops rising at exactly the same rate as the input meter, and stop there: How much power is that?
Most would be surprised to find the answer is usually about one-half of whatever the amplifier is rated for.
WB2WIK/6
RE: ALC Adjustment Procedure