5532 Op amp Pin Out
A Version of the Receiver Using Just L1 and C1 as the band pass filter
You can see a red LED and current limiting resistor in the photos. This is a power on indicator. The telescopic whip antenna can be seen in the lower photo.
Early Versions of the Project Front End
In section A of the schematic below, a dual-ganged 365 pF air variable
capacitor was used for tuning. CV, a small compensating capacitor may be required to adjust for the capacitive differences of
the 2 L-C tanks in the front end filter. It may have to be placed on the L1 side
of the filter (opposite to what is shown). A JFET source follower was used for Q1 but discarded because stage gain was
insufficient with a short whip antenna.
In the version depicted as section B, two 12-110 pF air variable capacitors were used along with switchable 270 pF capacitors to provide 2 ranges of tuning.
Although this worked, the switching mechanism was found to degrade selectivity somewhat. The JFET was reconfigured as a common source RF amp. This amp caused some
distortion of the RF signal on stronger stations unless the gate resistor was lowered to 47K or less. Ultimately a cascode BJT RF amp was chosen for the project. A photograph of the section A breadboard is shown below the schematic.
The inspirational detector schematic used for
motivation to develop the full wave detector
Varactor Tuned Front-end Band pass Filter
Above photo. The 2 potentiometer varactor controlled band pass filter.
