Supplemental to the Cascode Hybrid 5 MHz WWV Receiver
DC Voltages of the Cascode Hybrid Amp
On the right is the basic hybrid cascode amplifier schematic. Note that the Q1 voltage divider bias has two 10K resistors as compared to the 12K and 10K combination used in the final project. A slightly lower Q1 bias voltage was ultimately chosen along with a 150 ohm Q2 source resistor to enhance stability. Early bread boards of this amplifier used a 47 - 100 ohms Q2 source resistor along with the slightly higher Q1 bias, but suffered from parasitic oscillations.
The DC voltages are rounded to 1 decimal point. These are ball park values for reference purposes. The typical stage current draw was around 11 mA. R1 sets the output impedance and is optional. R2 sets the input impedance. This amp is very versatile in that it can be used to match a wide variety of input and output impedances.
The main 5 MHz WWV receiver web page
which this web page supplements is here.
Click here for a recording of
5 MHz WWV made with the
Icom R-75 receiver using the 6 KHz AM filter and the stock speaker. You may wish
to
compare it to the recorded 5 MHz WWV receiver project audio files linked
here ,
here and here.
10 MHz Components
For those who wish to experimentally develop a 10 MHz version, I have
included some potential band pass and crystal filter schematics you may wish to
consider. In addition, my preliminary experiments indicated that another RF
amplifier stage might be necessary for 10 MHz WWV. During development of these band pass and crystal filters, 10 MHz WWV reception was very poor and due to lack of time and the poor conditions, further
experimentation was abandoned.
To the left is a 10 MHz band pass filter schematic with a -3dB bandwidth of around 100 KHz.
The GPLA simulation of the 10 MHz front end band pass filter. Tuning is very sharp with this filter.
To the left is a crystal filter design for 10 MHz. The realized bandwidth of these simple min-loss crystal filters is dependent on your crystal parameters.
A photograph of the experimental 10 MHz crystal filter is shown to the right. Leads were kept long so that parts could be reused in future experiments.
Above. The GPLA simulation of the 10 MHz crystal filter.
6 MHz Components
Since it is easy to find 6 MHz crystals and Radio Habana Cuba is on 6.0 MHz, band pass and crystal filters were
designed for reference purposes. To the right is the front end, band pass filter schematic.
To the left is a potential crystal filter for 6 MHz AM reception. The bandwidth is ~ 5 KHz which is starting to get too narrow for some listeners, however, your crystal parameters will determine your filter's actual bandwidth.
The GPLA simulation of the crystal filter using the parameters from the 6.0 MHz crystals I had in my parts collection.
