All parts in the kit were properly identified and clearly referenced in the assembly manual.
Like the voltage regulator and audio amplification stages the RF stage went together without a hitch. The 10 transistor equivalent circuit of the TA7642 per the datasheet. The documentation points out that with the TA7642, it is possible to construct a Tuned Radio Frequency receiver with useful sensitivity and selectivity, using only a handful of components and that this device served as the basis of many radio receivers that were the successors to the Boy’s Radios. Equivalent to the ZN914 and MK484, the TA7642 contains ten transistors and performs the task of RF amplification, audio detection, and automatic gain control. The bulk of the RF work is handled by a single IC, the TA7642, which has its origins in the late 1960s. Other components in the stage included a pair of capacitors, a single resistor and of course, the transformer and speaker. The Murania has a single stage of audio amplification based on the 2N3904 NPN transistor that drives the speaker through a matching transformer. My Murania was putting out 1.792 VDC+ within the acceptable range of 1.6 – 1.8 volts. I appreciated that the instructions called for testing the voltage regulator circuit before proceeding on to the audio amp stage. The instructions call for covering the core with a layer of masking tape first and using masking tape to hold the first and last winding in place. 22 AWG enamel wire around a ferrite core. The first task is to wind the coil which consists of 37 turns of No. The radio is built in five stages… (1) wind the coil, (2) build the voltage regulator, (3) build the audio amp, (4) build the RF circuit, (5) final assembly. The 4SQRP website suggest the kit can be built in about 2 hours time, and that was my experience. Documentation is very good with clearly expressed step by step directions, but lacks pictures which might be helpful in illustrating potentially confusing steps for the newbie builder, such as the correct orientation of a polarized component such as an LED, diode or electrolytic cap.
#ONE TRANSISTOR FM RADIO RECEIVER SCHEMATIC MANUAL#
Like other 4SQRP kits, the assembly manual needs to be downloaded from their website. The Murania features a unique construction technique called “Pittsburgh Construction” developed by W0MQY, Joe Porter, in which components are soldered to the surface of pads on a silk screened double sided PCB. My Murania kit arrived quickly within 2 days of placing my order online….WOW! The Murania kit was inspired the design of those simple high performing transistor radios. The designers of Boy’s Radios employed some creative design techniques to maximize the performance of these minimalist circuits, with sometimes amazing results.
These 2 or less transistor “toy” radios became known as “Boy’s Radios” and are highly collectible today. The documentation for the Murania tells of the advent of transistor radios in the 1950s and how radios with 1 or 2 transistors were considered toys and therefore not taxed like radios containing more transistors. The kit was designed by NM0S, David Cripe, who has engineered several of the 4SQRP kits. Tonight I tackled one of their popular new non-ham radio kits, the Murania, a one transistor Tuned Radio Frequency (TRF) AM broadcast band receiver kit. I presently have the NM0S 4S-Tuner/Antenna Coupler kit on order. I have a few of their kits over the past few years, most recently including the Bayou Jumper Paraset transceiver last year. The Four State QRP Group (Oklahoma – Kansas – Arkansas – Missouri, in case you were wondering), founded in 2003, is one of the best developers and retailers of high quality and reasonably priced QRP (low power) ham radio and other do it yourself electronics kits.
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