When you see an amplifier provide loads of gain in a particular band or frequency it is usually because there is a circuit self resonance, so losses are minimal, or there is some negative feedback that due to phase shifts is becoming less so. ?It is not much fun when the amplifier gain and phase shifts flip into the positive region and oscillation begins.
toggle quoted message
Show quoted text
On Mar 14, 2024, at 07:13, Greg McCain via groups.io <gamccain50@...> wrote:
?Yes.
K2 - 50W Amp - QrpGuys SWR/Power meter.
Greg
On Thu, Mar 14, 2024 at 12:29 AM, Larry Acklin
<acklin@...> wrote:
Hi- is this into a watt/swr meter then dummy load?? Antenna connections with SWR issues can fool inexpensive watt meters.?
Larry
KB3CUF?
On Wed, Mar 13, 2024 at 11:23?PM Greg McCain via <gamccain50=
[email protected]> wrote:
Hi gang,? Not complaining ...? ?Just curious.
I had recently built 3 of the 50W amps ( 15M, 20M and 40M). Want to use them for a little extra punch (say 10 to no more than 20 watts out) for field semi-portable 'digi' work (FT8, J8Call, WSPR) . . .? well, just because.??I built all three as '12 volt' versions.?
?I set the drive bias exactly as described in the instructions. The builds went well and the amps appear to output as described in the manual(s)./graphs.
I was just wondering why the 40 meter version is 'hotter' than say the 20 meter version which is hotter than the 15 meter version.
I found that I can get 10 Watts OUT with the following Watts IN from my K2.
15M - approx 4.5 Watts IN
20M - approx 2 Watts IN
40M -? LOTS of WATTS OUT (Too Many) with Just 1 Watt in !!
** For the 40M, I found if I backed down the bias, I could get 10 Watts out by setting the K2 for between 0.1 and 0.2 Watts out. Yep 'tenths' of a Watt.?
Is my stumbling on the bias backdown a potential problem point?
Or, perhaps I should make up some PI attenuator circuits to add to the Transmit circuit chains in the AMPs where needed to tone down the 3.6 - 3.9 Watts that my new QMX is producing??
Thanks in advance,?
Greg? KI4NVX
