On Sat, Jul 13, 2024 at 06:53 AM, ajparent1/kb1gmx wrote:
So the QRPL amp with the HL2 17dBm output is a better match to the task.
If that ends up being too much drive a small low power (50mW) 2-4db
attenuation is far easier to do if needed.
Hi Allison
I rigged up a 50ohm BNC dummy load and connected it to the DSO, (Siglent SDS1102CML+ 100MHz Dual channel oscilloscope), and life is suddenly V good, see table below !!!
| Fmeasure= |
5398.5 |
KHz |
Zload= |
50 |
ohm |
| ? |
? |
? |
? |
? |
? |
| dB Output |
Vpp |
Vrms(mV) |
V^2 |
P(mW) |
P(dBm) |
| -7.5 |
1.77 |
580 |
0.3364 |
6.73 |
8.28 |
| -7.0 |
1.80 |
620 |
0.3844 |
7.69 |
8.86 |
| -6.5 |
1.90 |
660 |
0.4356 |
8.71 |
9.40 |
| -6.0 |
2.00 |
700 |
0.4900 |
9.80 |
9.91 |
| -5.5 |
2.10 |
740 |
0.5476 |
10.95 |
10.39 |
| -5.0 |
2.24 |
780 |
0.6084 |
12.17 |
10.85 |
| -4.5 |
2.36 |
820 |
0.6724 |
13.45 |
11.29 |
| -4.0 |
2.52 |
880 |
0.7744 |
15.49 |
11.90 |
| -3.5 |
2.66 |
920 |
0.8464 |
16.93 |
12.29 |
| -3.0 |
2.80 |
980 |
0.9604 |
19.21 |
12.83 |
| -2.5 |
2.96 |
1040 |
1.0816 |
21.63 |
13.35 |
| -2.0 |
3.16 |
1160 |
1.3456 |
26.91 |
14.30 |
| -1.5 |
3.36 |
1180 |
1.3924 |
27.85 |
14.45 |
| -1.0 |
3.54 |
1280 |
1.6384 |
32.77 |
15.15 |
| -0.5 |
3.76 |
1320 |
1.7424 |
34.85 |
15.42 |
| 0.0 |
4.00 |
1400 |
1.9600 |
39.20 |
15.93 |
So the RF1 17dBm output is indeed fully variable, and a simple fixed 3dB attenuator between it and the QRPLabs 10W PA should bring down the drive level to around 25mW.
The "dB Output" data are the values from the "Drive Control" in the Thetis SDR s/w, ie 0dB is full power out
Thank you ever so much for your suggestions, and prompting me to try the 17dBm output, this certainly makes for a cleaner/simpler design both philosophically and practically.
Thank You once again, 73
Peter - GM8JCF
