Hello Taka,
the spectra in the pdf file you enclosed above show a
carrier at around -10 dBm on the spectrum analyzer (e.g in the 20 m
band), which taking into account the 20 dB + 30 dB of attenuation you
had would mean an output of 40 dBm so more than you reported later - not
sure which numbers are the right ones, hi.
The inductance values you
measured for the transformer look reasonable, at low frequency that
core gives about 10 uH/turn^2, with nominally a 30 % tolerance.
I did not yet test the PA here, for the moment I have some measurements on the driver - modified with R55 at 120 ohm:
here is the output power at the fundamental over frequency, for different drive levels in Quisk:
Hello,
here are some measurements on the H-Lv2b3 TX IMD; the results look quite good, similar to what measured previously on the H-Lv2b2, taking into account that the drive level to the PA is now lower and its supply is also lower.
here is the H-Lv2b3 PA output vs frequency for the various TxPGA settings:
73, Graeme zl2apv
Hello,
I was referring to the post just above
where the driver output is plotted vs. frequency; in the H-Lv2b3 the
driver output peaks at about 17 dBm at 14 MHz and goes down to 15 dBm at
30 MHz. In the previously measured drivers the drop at high frequency
was quite less; a summary of the measured PA drivers outputs for the various versions is in the graph below
Hi Alan,
Hello,
today I removed all the PA driver input filter components and
measured them on a VNA; from what I could see they looked ok and quite
similar to the ones I used for the H-Lv2b2 - except maybe the
capacitors, for which it was difficult to precisely measure the
losses/Q.
Since I suspected that some/all of the capacitors might not
have a very high Q, I changed them all (C49, C50, C51 and C52) with the
spares I had from the previous build. Besides R56 and R59, which were changed previously with no measurable effect, I didn't change anything else.
This made quite a difference on the PA output level flatness:
150pF 0805 NP0>=50V<=5% | CC0805JRNPO0BN151 | Y | C50 | 805 | 2 | 1 | http://www.octopart.com/search?q=CC0805JRNPO0BN151 | ||||||
160pF 0805NP0>=50V<=5% | GRM2165C2A161JA01D | Y | C51 | 805 | 2 | 1 | http://www.octopart.com/search?q=GRM2165C2A161JA01D |
Hello Steve,
Hi Alan,
but at a slower time base also this
the reading depends anyway on the probe position, I think there is some RF noise picked up there.
Measuring near the DC/DC converter, on DB14, I sometimes see some jumps in the voltage, at low power and at full power, does not make much difference:
but a similar behavior I see also on the other DC/DC converters, so I guess it might be a "feature" of the converter.
Finally, the regulation seen with a two-tone test, still at full power at 1.8 MHz on DB14, seems not too bad
73 de Claudio, IN3OTD / DK1CG
Measuring near the DC/DC converter, on DB14, I sometimes see some jumps in the voltage, at low power and at full power, does not make much difference:
I've remeasured the ripple/noise there to double check and I get the same results, maybe even a little less.
The measurements above were done at 1.8 MHz; as you saw, at 3.8 MHz the ripple on the Vpa supply increases and with the TX at this frequency, I see about 200 mV peak-to-peak near B100:
Note that 3.8 MHz is more or less where the 2nd harmonic has a maximum also(see bottom graph here); it was roughly the same also in the H-Lv2b2.
The waveform on the LDMOS drains looks slightly flattened at the top, so this may be similar to what you see also: