I build the 40dB tap from the same QST article as my W7ZOI_Power_Meter.
To make it useful, I need to measure the coupling and insertion loss, so here goes. S1 and S2 are the through ports, S3 is the tap. It's pretty flat over 7-433MHz, with a through loss of <1dB and a coupling of 33-34dB.
Test setup is the FT817 in FM mode and lowest power as the signal source, through a 20dB pad to the source port of the coupler, the W7ZOI_Power_Meter connected to the measured port, and my better 50R termination for the remaining port.
So, now I can connect a dummy load to S2, my new ubitx to S1, and the power meter via a 20dB pad to S3, shout oooollllllla into the mic and read -16dBm off the power meter.
Thats -16dBm after 20dB of attenuation and a coupling of -34dB, so I'm ooolllllaaa-ing at -16+20+34=38dBm, or six-point-something watts. Maybe a bit low, bit it'll do for now.
F [MHz] | S1S2 [dBm] | S1S3 [dBm] | S2S3 [dBm] | SRC [dBm] | loss S1S2 [dB] | loss S2S3 [dB] | |
---|---|---|---|---|---|---|---|
0 | 7.15 | 4 | -30 | -30 | 4 | 0 | 34 |
1 | 10.00 | 4 | -30 | -29 | 4 | 0 | 33 |
2 | 29.00 | 5 | -29 | -28 | 5 | 0 | 33 |
3 | 50.50 | 5 | -28 | -28 | 5 | 0 | 33 |
4 | 145.50 | 4 | -29 | -29 | 5 | 1 | 34 |
5 | 433.00 | 3 | -30 | -31 | 3 | 0 | 34 |