When using direct conversion receivers or Zero IF frequency SDR receivers it
is important to have capacitors across
all rectifiers in all the power supplies if possible.
Sometimes Local Oscillator leakage thru the power line coupled to the power
line by some other means, gets is
modulated by the changing impedance of the diodes at a 120 Hz rate and you will
hear a constant buzzing sound.
The signal introduced by the local oscillator to the power line is amplitude
modulated by the diodes switching on and
off and picked up again by the receiver. The AM signal is at the same exact
frequency the receiver is tuned to and
the sidebands are demodulated.
This same effect is sometimes noted when you tune in your own transmitted
signal, lets say a CW signal, and you hear
a hum on the carrier which is not heard at the far end. The RF in the shack is
being modulated in the same way. The hum
is only noticed in the shack but not on the signal going out the antenna.
73
Bill wa4lav
________________________________________
From: Amps [amps-bounces@contesting.com] on behalf of Hardy Landskov
[n7rt@cox.net]
Sent: Friday, September 13, 2013 12:28 PM
To: amps@contesting.com
Subject: [Amps] Rectifier equilization?
I have just rejoined the amp list after a few years and am wondering if the
diode equalization question was ever resolved.
I am building a new bridge HV PS and it uses 12 diodes per leg. Rich Measures
says using a .01 & 470K across each diode is no longer needed due to
improvements in semiconductor manf. processes.
I have 100 1N5408's that came off the same reel so I feel they should be
matched fairly close.
I would like to hear a few opinions.
Thanks
73 Hardy N7RT
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