“The Electronics Of Radio” NorCal 40B Transceiver Build Lab Notes: Problem 16F, 16G
This continues a series of blog posts on David Rutledge’s text, “The Electronics of Radio”, that I am studying while building the NorCal 40B transceiver. This series of posts will not be a review of the book, nor is it a assembly manual. Rutledge presents a series of problems at the each chapter that aid in understanding electronics and building the 40M QRP CW transceiver. I am going to try to go through all of these problems and document them here. All of these are titled similarly, so search for them that way. For what its worth, most people will want to skip these posts, they are really for my own self-education on electronics and may not make a lot of sense unless you have Rutledge’s book.
[The links to all problem solutions as I go through them will be posted here.]
T3, C14, C6, and L14 are added on to the circuit. Plus resistive loads are added to U1 and U2 for signal input and measurement purposes. Plus resistive loads are added to U1 and U2 for signal input and measurement purposes.
F.
L = AL * N
AL = 55nH/turn2
Nprimary = 23; Lprimary = 55 * 232 = 29.1µH
Nsecondary = 6; Lsecondary = 55 * 62 = 1.98µH
—-
f0 = 1 / (2π√(LC))
C = 1 / 4π2f02L
—-
Cprimary = 1 / 4π2f02L = 1/(4π2 * 4.9MHz2 * 29.1µ) = 36.3pF
Csecondary = 1 / 4π2f02L = 1/(4π2 * 4.9MHz2 * 1.98µ) = 532.8pF
The frequency with the largest voltage output seen on the oscilloscope is identified (4.914.015MHz).
Here is the waveform with 2.74V at its maximum peak-to-peak.
G.
Loss from the 10V input signal to the 2.74V output signal is calculated. Note: If the loss is >10dB, then something is wrong with the build. In my case it looks okay so far!
Loss = 10 log (P+ / Pend) db
V+ = 10 Vpp
Vend = 2.74 Vpp
P+ = V+2/R+ = 102 / 3K = 33.3mW
Pend = Vend2/Rend = 2.742 / 1.5K = 5mW
Loss = 10 log (P+ / Pend) db
Loss = 10 log (33.3m / 5m) db = 8.23dB
Another chapter done!
KM1NDY