All of these are suitable to demonstrate your skills for the Intermediate Radio Amateurs exam!
The Trull RX
This is a very simple radio intended for those just starting on building electronic projects. The standard version is supplied with parts for receiving the lower part of the medium wave broadcast band where there are powerful signals (easy with short aerials in the UK) from Talk Radio and Absolute Radio. It is a regenerative tuned radio frequency receiver that is suitable for receiving the amplitude modulation used by the main MW broadcast stations. The regen TRF is an old technique that has been brought up to date with modern devices that make it much easier to use. It has an adjustable gain RF amplifier, tuning/detector, regen and audio amplifier stages; with the latter being able to drive a small loud speaker or phones. It has plenty of space on the 100 x 160 mm single sided printed circuit board, and includes a holder for a 9 volt battery with On/Off switch. An alternative TOKO 3334 inductor can be specified when ordering, that allows it to be used on the 20, 40 or 80m amateur bands while the regen stage also permits copy of CW and SSB phone stations. The price is £24.
The Knapp RX
The is a simple project aimed at first time amateur radio constructors, and those who used valved versions of this classic type of RX! Because it is a regenerative Tuned Radio Frequency receiver, it is able to copy broadcast stations using amplitude modulation or amateur transmissions using morse or single sideband phone (and double sideband too). The smooth regeneration control, with its separate transistor stage, provides a marked increase in selectivity and sensitivity compared to an ordinary TRF set. It can be built for any 'band' between 3.5 and 15 MHz, and has several options to keep the tuning range to less than 150 KHz for operator convenience. It uses a single sided 50 x 80 mm PCB with detailed step by step instructions that are suitable for novice builders - for its simplicity, the rig performs very well. You will need simple common tools (wire cutters, small screwdriver, solder/soldering iron) to assemble it, together with some wire for an aerial, a 9 or 12 volt battery and a pair of Walkman type stereo 32R phones. This photo shows an 80m version without its knobs fitted. Price is £22
The Knole DC RX
This is a 'good' direct conversion receiver intended for use an any single amateur band 20 to 80m. It can drive a loud speaker and has filters for CW and phone - SSB/DSB. It is provided with a triple tuned radio frequency input filter, and has a MC1496 Gilbert cell mixer that is 'stronger' than many other types, and is thus better able to combat troublesome out of band broadcast transmitter interference. The main double sided circuit board is 100 mm square with the controls mounted on a small printed circuit front panel. It uses three integrated circuits, a supply regulator and a FET for the local oscillator; this uses a toroid for better frequency stability with a PolyVaricon Main tuning capacitor and varactor Fine tuning - the latter can be changed to receiver incremental tuning when used with a CW transmitter. It has a wide supply range of 9 to 16 volts with reversed supply protection. It can be used 'open' style as pictured, or easily put in a box if you prefer! The PCB is drilled ready to accept a TR relay for use with either the Kilton or Kilmot transmitters below. Price £44
The Kilton TX
This is the CW transmitter to go with the Knapp or Knole receivers. It is normally 'crystal' controlled for use as a 'seperate' whose tuning is NOT linked to the receiver. It can do any band in the range 20 to 80m using your actual crystal or a ceramic resonator. It is supplied with a 3.59 MHz ceramic resonator for 80m use, which can be pulled or tuned down over about 50 KHz with the on board tuning trimmer. When a crystal is used, the pulling tuning range will be very limited. It produces 1.5 Watts on a 13.8 volts but can use a supply in the range 9 to 16 volts. The output low pass filters are included together with provision for full or semi-break in T/R operation. The T/R relay control circuits are included but owing to a lack of space on the PCB, the relay has to be mounted elsewhere. When you order it with the Knole RX, the relay is included and it can be mounted on the Knole PCB. The circuit does not provide receiver sidetone. Apart from the tuning, there is nothing to adjust or set up! It is the same size (50 x 80 mm) and style as the Knapp but uses a double sided PCB. The photo below shows it built for 80m with a ceramic resonator. The price is £19. 7.03 MHz or 14.06 MHz crystal are £2 if wanted.
The Kilmot TX
This is the phone transmitter to go with the Knapp or Knole receivers! It provides double sideband (DSB) suppressed carrier phone signals which are fully compatible with any other station using upper or lower single sideband transmission - this approach makes everything rather simpler! Like the Kilton, it is normally 'crystal' controlled for use as a 'seperate' whose tuning is NOT linked to the receiver. Although it can do any single band 20 to 80m with an actual crystal or ceramic resonator, it is most effective on 80m. It is supplied with a 3.68 MHz ceramic resonator, which can be pulled over about 50 KHz (down) using the on board tuning trimmer. When a crystal is used, the pulling range will be very limited. It produces 1.5 Watts on modulation peaks with a 13.8 volts supply but can use anything in the range 9 to 16 volts. The output low pass filters are included together with provision for T/R relay control by your mike's PTT switch. Owing to lack of PCB space the T/R relay is not included, except when you order it with the Knole RX, where there is space for the relay to be mounted. It is intended for use with the common sort of dynamic microphone. Setting up can be done with care by using your normal dummy load and output indicator. It is the same size (50 x 80 mm) and style as the Knapp but uses a double sided PCB. The photo below shows it built for 80m with a ceramic resonator. This kit is a bit more dense than others in this category and does require a little more patience to locate the correct holes for each part! The price is £24. Crystals for 7.159 MHz or 14.318 MHz are available at £2 each.
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