GW4ALG 136 kHz Transverter

The 'transverter' (transmit & receive converter) was designed to work with a Yaesu FT707 transceiver, operating at 10 MHz.   All of my best DX QSOs were made using this set up.  More recently, I have modified the transverter to interface with my IC756PRO.

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Operation

On receive, the antenna is link-coupled to a tuned 'longwave' coil having a ferrite rod core. The signal then passes through a bandpass filter (two top-coupled tuned circuits) to gate 1 of a BF981 dual-gate FET, where the signal frequency is mixed with 10 MHz to produce the 10.136 MHz output to the transceiver.

On transmit, I use another BF981 FET mixer driven by the low-level RF signal (about 100 mV) available on the back panel of the FT707 and IC756PRO.  Incidentally, the level of the RF signal is continuously variable on the FT707 using the CARrier level control on the front panel.  But the RF  POWER control on the IC756PRO provides only a limited range.  The 10.136 MHz from the transverter is mixed with the 10 MHz local oscillator to produce the required 136 kHz.   The signal is then amplified to drive three bipolar transistors (Sanyo 2SD325D) connected in parallel. Bifilar-wound, dust-iron cored toroidal transformers match the low-impedance collectors to 50 ohms.  Finally, the output passes through a single section low pass filter and directional power meter.

Circuit diagram

Many of the components were found in my junk box, so I'm sorry that I haven't been able to include any manufacturer's part numbers!   Please contact me if you have trouble finding suitable components, and I'll try and suggest some alternatives. 

Receive Converter

L1 is a 'long wave' coil slid over a short section of ferrite rod and resonated to 136 kHz.   A couple of nice slug-tuned coils of about 3.5 mH were used for L2 and L3  (salvaged from an old tape cassette player).  L4 and L5 are 10 MHz IF transformers.

Transmit Converter

L6 is another slug-tuned coil salvaged from an old tape cassette player.    L7 and L8 are ex-equipment coils (about 60 turns), wound on EMC grade ring cores coloured yellow & white; 21 x 12 x 6 mm.

Driver and Power Amplifier

L9 and L10: same as L7/L8. 
L11 and L12 are each 25 turns, bifilar-wound on ex-equipment, EMC grade ring cores coloured yellow & white; 33 x 20 x 11 mm.  I never did understand why the 0.22uF coupling capacitor between L11 and L12 works so well: it seems that 2.2uF would be a better choice!  Also, the use of 25 mm OD 3C85 ring cores  for L11 and L12 (instead of EMC grade material) will provide greater PA efficiency.

Each PA transistor will draw about 1.2 A.  Select a device that will be happy at 1.5 A at 10 W dissipation.  Use a heat sink!  My PA delivers about 18 W output for 40 W input - you must be able to do better than this!

Control Circuits; LPF; and Power Meter

L13 is wound on a piece of ferrite rod. 
L14 and L15 were made using the same type of coil as used for L7/L8/L9/L10 (see above), with a two-turn link winding added.  25 mm OD 3C85 ring cores  would be more suitable.

Transverter DC Interface Circuits

Transverter RF Interface Circuits

Connection information

Feedback

Suggested improvements would be most welcome!

Des M0AYF has based his transverter on the above design.  Click on the thumbnails below to see the completed unit.