This afternoon, I conducted more comprehensive insertion loss testing
through the Ameritron QSK-5. I confirmed that the result of the excessive
loss is primarily due to the SPE's ATU being in-line, even in bypass. In
bypass, the ATU must still be optimized per band and per band segment. More
than likely, I had not optimized the SPE tuner before testing and had
neglected to include all tuner loss, thinking that the SPE was in hard
bypass in "standby" mode through what I imagined was a high-quality relay
bypass with short leads, resulting in a fairly constant Z through the bypass
and essentially minimial loss. The SPE ATU is indeed active whether the amp
is in bypass or operate.
I again ran 100W through the SPE after optimizing the ATU in bypass, and
measured only the diffefrence of the QSK-5 being in and out of the circuit
and reconfirmed by testing with the SPE amp in hard bypass by jumpering the
amp's In and Out cables together. Recall that my QSK-5 is never in bypass
mode through its internal relays; its always in the operate mode through the
PIN diodes and amp bias is controled seperately.
Measured QSK-5 loss:
40m: 0.22 dB
10m 0.23 dB
Measured loss through SPE tuner using "auto-tune" optimizing:
40m 0.30 dB
10m 1.00 dB
The disparity between my original 1.5 dB loss on 10m and the new combined
measurement of 1.23 dB is likely the result of the ATU not being optimized
and saved to memory during the initial testing. The SPE amp uses a switched
relay network consisting of caps and toroids much like that used in many of
today's internal rig tuners. My experience is that switched component
tuners in general are more lossy than classic internal tuners using variable
C and switched or variable L.
Again, today's testing was conducted using a Bird 150W Terma-Line load. I'm
much happier with the QSK-5 loss performance now.
Paul, W9AC
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|