Intermediate

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 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! 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! 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 complicated than separate RX and TX, but it does make operation very much easier! This scheme is shown above. 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 and they cost an extra £2. The Ilford kit costs £18. If ordered together, the Ivel and Ilford are discounted to £43.

The Ilton DSB Transmitter

This is 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 will be crystal controlled except on 80m where there is a suitable 3.69 MHz resonator, which should also permit transceive operation with the Ivel. 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 £49.

The Culm

This is a small CW TCVR for any single band 20 to 80m. On 80m it uses a ceramic resonator for the VFO to give several tens of KHz tuning range. 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 has an RF amp with an RFG preset, followed by a double tuned RF filter and then a pair of JFETs for the product detector. This is followed by the first audio amp and a humped low pass CW filter centred on 725 Hz , which feeds the AFG pot and the audio power amp for a LS or phones. For transmission, the VFO 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) on any band to 20m. 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 3.58 MHz ceramic resonator can be replaced by a crystal of your chosen frequency for the higher bands where ceramic resonators are not suitable. Alternatively, fit a 2 or 4 MHz ceramic resonator to drive the extra Sim-mix kit fitted with a crystal for any band (including 5262 KHz!) up to 20m – this has the advantage of giving approx 50 KHz tuning range instead of the very limited range with a crystal. Adding the Sim mix (in the Accessories section) for the higher bands is a little bit more complicated mechanically as they do need to be near each other and to set them up properly. The photo below is the simple 80m Culm. The main difference between the Culm transceiver and the Ivel/Ilford combination is that it is half the size (due to the double sided PCB) and the TR arrangements which give full break in operation so you can hear the other station between your Morse characters! The Culm price is £42.

The Heath RX and Heale TX

This pair is aimed at those who enjoy phone Amplitude Modulation! The Heath RX, for either 40 or 80m, employs a crystal controlled converter ahead of a low frequency Regen RX so it can receive all the common modes – CW, SSB and AM! The Heale is primarily an AM transmitter for the same band using a MOSFET CW output stage and gate audio modulation for the AM. Nominal max output power is 5W with a carrier level of 1.25W on AM. For transmission, the signal flow in the RX is reversed so that transceive operation should be possible on their chosen band. These are new designs, with etched prototype PCBs having been made, but sadly not yet tested! They are a bit more complicated than a DC RX and are comparable in complexity to a simple superhet. I may later decide that the Heale TX should really be on the Advanced p

Site Navigation

Home, Simple, Advanced, Accessories and Ordering pages

%d bloggers like this: