This is a small fun 1.5 Watt CW transceiver! It has good performance for its size as it is optimised for single band CW operation. It is normally supplied for 80m using a ceramic resonator VFO giving coverage of all of the CW section of the band, however it can also be used on other bands as described below. It is direct conversion with narrow 750 Hz bandpass audio filtering. The output is for 'Walkman' type 32R stereo headphones. It has controls for the main tuning, fine tuning for reception and audio gain. The Fine tuning control acts as the receiver incremental tuning which is automatically removed during transmission, or with the RIT slide switch. The keying operation is full break in. The rig includes receiver muting and a transmission sidetone audio oscillator, with a separate preset for its level in the phones. There are double tuned receiver band pass filters and double half wave transmitter output low pass filters. The audio filtering also includes a humped low pass filter to narrow the receiver bandwidth. It can be easily mounted in your own case if you prefer using conventional pots etc. There are many options for experiment and it can also drive the 10W Linear RF amp. The PCB is doubled sided 100 x 80 mm. It needs an 8 to 16 volt supply with RF output varying accordingly. Price is £34.
The standard kit includes suitable RX and TX filter parts for use on any band up to 20m, but for use on bands other than 80m, the VFO needs either your own QRP frequency crystal OR the Mini Mix kit - this is much preferred since it retains the wide tuning range for all bands. (The tuning range of a plain crystal will be very limited.) The mixer kit (see Accessories page) takes in the standard 80m VFO where it is mixed with a band dependent crystal, filtered for the chosen band and fed back to the LO circuits of the Brent. The Mixer kit is 50 x 80 mm and costs £14 for any of 20, 30 or 40m.
This is the standard Brent equipped for 80m:-
This is a transmitting project aimed at builders with limited experience where ease of assembly is important; the PCB has been laid out with plenty of space and it includes a small front panel. The robust IRF510 output transistor, mounted on a heatsink to make it more tolerant of abuse, produces 1.5W of RF on a nominal 12 volt supply. It is normally supplied for 80m using a ceramic resonator VFO giving coverage of the lower half of the phone section of the band. It is capable of working on other bands to 20m using either a crystal or the Mini Mix kit but please ask me about this before ordering. Tuning is by a PolyVaricon variable capacitor. The double tuned receiver band pass filters feed the single mixer chip, which acts as a product detector for the direct conversion receiver. The audio amplifier has a bandwidth of 3 KHz suitable for voice signals, with an AFG pot and is able to drive a loud speaker. The transmitter uses double sideband modulation, with a suppressed carrier - this is fully compatible with other stations using single sideband! The speech amplifier, with a mike gain preset, is designed for low impedance dynamic microphones. During transmission, the mixer chip is used as a balanced modulator. The transmitter RF amplifier has its own RF gain control preset to ensure that the output stage does not limit on speech peaks. A double half wave filter removes the unwanted transmitter harmonics. The rig’s TR relay is controlled from the mike’s PTT switch and mutes the RX during transmission. There are many options for experiment and it can also drive the 10W Linear RF amp. The main PCB is double sided 100 x 100 mm. It needs an 9 to 16 volt supply. Price is £49.
This is a simple superhet for any single band from 20 to 160m. The great advantage of the superhet is much less interference from the unwanted second sidebands which are present with direct conversion RXs. Being only a receiver means that it does not have the extra complication associated with transmission and hence is easy to get going. The PCB layout is well spaced out to occupy most of the 100 x 160 mm PCB which has a ground plane for good RF earthing. It uses a 6 MHz five crystal ladder filter suitable for phone reception. In addition there is a switchable audio CW filter with an output stage for phones or a loud speaker. The VFO frequency depends on band and features varactor tuning with coarse and fine controls to just cover each amateur band. There is also double tuned RF filtering. The carrier insertion oscillator is usually adjusted for the sideband normally used for phone on each band. It is supplied with hardware and plain PCB front panel. The matching transmitter is the Kingsdon. The photo shows the RX with a TX attached. Price £49 but see below!
This is the matching 5 Watt phone and CW superhet SSB transmitter to go with the Midney receiver. It can do any band up to 20m but this must be the same as the RX's! The speech amplifier, for low Z microphones, drives the CIO/balanced modulator, followed by an IF filter, RF mixer using the RX LO signal which feeds the TX BPF, broadband driver and tuned FET output stage. CW is done by injecting a keyed 750 Hz tone into the speech amplifier and the RX audio stage for sidetone. CW TR control is semi break in. It is a well spaced 100 x 160 mm double sided PCB which is normally mounted immediately behind the RX PCB as shown below. Price £49, but ordered with the Midney, both are £89!
Photo of the Midney with Kingsdon transmitter attached:-
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