Syllabus Sections:-

Transceivers ( transverters )

  3N2   30  Understand that using a transverter enables operation on frequency bands not covered by the primary transceiver equipment.

The use of down converters and transverters ahead of HF equipment was popular until about the late 70's.

Down converter

A down converter take a signal from a band higher than HF ie higher than 30MHz say 2m and converts it down to an RF signal in the HF band range. This is achieved by mixing the 2m signal with an Intermediate Frequency to give an output on 28-30MHz.

The signal that came in on the 145MHz band is now being heard on a receiver tuned to the 28MHZ band and so long as the HF receiver can receive the mode of the signal is will be heard just as if the receiver could receive 145MHz directly.

The Transverter

Whilst the down converter only dealt with the converting down of a signal the transverter could not only achieve the conversion down but also the conversion up. This then enable a radio amateur with only an HF rig to transmit and receive 2m.

Where is such equipment used to-day ??

It is not used in the lower frequencies but the microwave frequencies commonly down convert to 2m or 70cms when receiving satellite communications and sometime a transverter is also used.

3N2   30 continued  Calculate appropriate frequencies used in transverter operation.

Transverters were used mainly for HF to VHF use when transceivers were either HF all mode as not many vhf/uf all mode units about. Now a days technology has caught up so we have many multimode HF/VHF/UHF units. Generally the most wanted band is 144-146mhz for this you will need an IF by using a crystal controlled  LO (local oscillator) of 116 MHz to can mix to the required frequency by the rig to produce 28-30 MHz.

So to sum up use a rig with 28-30 MHz with mixer IF of 116 MHz to give you 144-146mhz i.e 116+28=144, and 116+30=146.

3N2   30 continued  Recall that transverters generally require low power drive.

A low power drive from the transceiver into the transverter will be needed to avoid destroying the transverter as it will not be capable of using a full HF radio's power into it.

3N2   30 continued Understand the need for extra care to avoid transmitting out of band when using a transverter.

When using a transverter the frequency of conversion i.e 28 to 30 MHz is very close to the band limit for ham use i.e 29.700 for HF, so this end of band limit MUST be accounted for in any transconverter

3N2   30 continued Recall that transverters require correct interfacing with the primary equipment to control sequencing and prevent hot switching

So what is hot switching ? Hot switching is a term used to describe the operation of a relay whilst the input signal is applied. You must neither open nor close a relay on a transverter when the main rig supplying the RF drive is in the transmit position. Such hot switching can reduce the life of the relay, because a relay used to hot switch will experience contact erosion and heating which does not occur in a cold switching that is when no drive is applied.
So the transverter needs to have circuitry linked to the primary rig which controls when it is to switch to TX and RX and to only switch when no drive is applied from the primary rig.

3N2   30 continued Understand the techniques of RF sensing and PTT (Push-to-talk) transmit receive switching.