The Ivel plus Ilford CW TX

The Ilford transmitter (on the left above) allows you to send Morse code. It is normally coupled to a simple receiver like the Ivel receiver described on the Simple page. The Ilford transmitter can work on any one of the 20 to 80m bands and is ‘crystal’ controlled – this means that it uses either a crystal or a ceramic resonator to determine the transmitted frequency. For 80m, there is a suitable 3.58 MHz resonator whose operating frequency can be pulled down by a tuning capacitor to give a tuning range of typically a few 10s of KHz in the CW section of the band. Unfortunately, higher frequency resonators are not sufficiently stable and cannot be used above 80m, so you may have to use an actual crystal for 20, 30 or 40m – the consequence is that the tuning range on these bands is very limited – a KHz or so! (But see below about the Diode Doubler for 40m!) This means that 80m is often a good band to experiment and learn CW skills. The transmitter produces 1.5W of RF using a 13.8 volt supply and includes an output low pass filter to get rid of unwanted harmonics. It also includes a transmit receive relay for switching of your aerial between RX and TX, this is activated automatically when you press the key and has a delay before reverting to reception to cater for the gaps between Morse characters. Pressing the key also activates the RX muting electronic switch which prevents unwanted crashing sounds from the RX when transmitting, while still allowing the keyed 725 Hz sidetone oscillator to run and produce audio output through the RX’s audio output amplifier.

For 80m, the ceramic resonator can alternatively be fitted in the Ivel RX allowing transceiver operation where TX and RX operate on effectively the same frequency with single knob main tuning! In fact, the RX has to be tuned very slightly off (by the RX’s Fine control) in order to create a beat note but this offset is automatically removed by the Ilford when actually transmitting. This arrangement is a little more electrically complicated than separate RX and TX, but it does make operation very much easier! The kits in the picture above are wired this way for 80m. The standard Ilford kit includes the 3.58 MHz resonator but if you want crystals for the higher bands you need to tell me what is wanted. With a crystal in the Ilford for the higher bands, the tuning of the Ivel and Ilford are no longer linked and they have to be tuned and operated as ‘seperates’; so please ask me about crystals and adding a trimmer to the Ilford when contemplating this form of separate tuning and I will advise the costs. The standard Ilford kit costs £18. If ordered together, the Ivel and Ilford are discounted to £44.

The Ilton DSB Transmitter

This is a double sideband phone transmitter intended to go with the Ivel RX. Double sideband is much simpler and cheaper to produce than SSB and it is entirely compatible with stations using SSB – either upper or lower sideband. They wont know you are using DSB until you tell them! Much like the Ilford above, the Ilton is normally crystal controlled except on 80m where there is a suitable 3.69 MHz resonator, which allows transceive operation with the Ivel on 80m. (But see below about the Diode Doubler for 40m!) For the higher bands, they have to be tuned independently. Please ask me about these higher bands. The transmitter is mounted just behind the Ivel RX (see photo below) with links to the RX for muting when transmitting. The Ilton’s speech amplifier is designed for dynamic microphones and uses BS170 MOSFETs driving an SA602 modulator to produce the DSB signal; this is amplified using a high speed op-amp driving the IRF510 output stage (with heatsink) which is followed by low pass filters and the aerial change over relay. Peak output is about 1.5W when using 13.8v supplies.

Should be just the job for across town nattering! The price for the Ilton is £24, If ordered together, the Ivel and Ilton are discounted to £50.

Diode Doubler kit

This is a kit that overcomes the necessity to use a crystal for either of the above transmitters on 40m; it works by using the Ivel receiver VFO running near 3.5 MHz and then doubling the frequency to 7 MHz so that you can get VFO operation of the transmitter and receiver together for easy transceiver operation. The kit is a small single sided PCB with an amplifying stage followed by a diode full wave rectifier and then the 40m band filter to remove the unwanted 80m signal from the output which is used to drive the receiver or either transmitter. If you are in any doubt about how to set this up, it is not difficult if both RX and TX, are already known to be working. The price when ordered on its own is £14 but if ordered with either transmitter it is reduced to £12.

The Bradney AM Transmitter

This is the AM TX to go with the Bratton RX. It uses a ceramic resonator (3.69 or 2.0 MHz) to control the frequency and avoid pulling from the output stage, with a tuning range of about 50 KHz down from nominal, under the control of a trimmer and the push button to activate the oscillator stage while the RX is still active. The speech amplifier is designed for common dynamic type of microphone with PTT control of the oscillator, TX output stage, RX muting and TR relay. Peak output power is 5W on 13.8v supplies so that for normal AM use, the carrier level is set for 1.25W allowing full modulation to rise to peak power. (With a few alterations it can also be used for full output CW!) There is the usual double pi harmonic filter for either band. The TX price on its own is £21 but when ordered with the Bratton RX they are discounted to £50.

The Somer

This is a new small CW TCVR for any one of 20, 40 or 80m. It has a new LO scheme using multiplication up and division down from the VFO to avoid chirp without using a crystal or ceramic resonator! So goodbye to rockbound transmitters! The arrangement can provide whole band coverage but this is seldom actually desired to keep the Main tuning rate reasonable. The RX is direct conversion with a PolyVaricon for the main tuning and a voltage controlled diode for the Fine tuning and beat note offset; the latter being automatically cancelled when you go to transmit. The RX is direct conversion using a double tuned RF filter feeding into a SA602 mixer, with a conventional audio pre-amp, humped low pass CW filter and main audio output for phones or a small loud speaker. For transmission, the LO chain feeds digital gates for the RF keying which then drive a buffer stage and a pair of BS170 MOSFETs in the output stage for a nominal 1.5W (with a 13.8v supply). The transmitter output has twin pi low pass filtering and the TR control circuits automatically disconnect the LPF from the RX RF amp when transmitting, for click and thump-free full break in changeover! There is also a 725 Hz sidetone oscillator, with adjustable level, that feeds into the RX audio amp. The photo above is the 20m prototype Somer; two kind early builders have now helped prove the rig and the instructions! The main differences between the Somer when compared to the Ivel/Ilford combination is that it is half the size, with VFO coverage for any one of its bands and with full break in operation. The price is £52.

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