Elecraft K-2_XV_serie_application_notes_2006.pdf, transverter_application_notes_RevC.pdf Elecraft_K-2_XV_serie_application_notes_2006.pdf

ELECRAFT TRANSVERTER APPLICATION NOTES

Rev C

By Dave Olean (K1WHS) and Jay Rutherford (K1UC)

Editors Note: This article was written before the introduction of the K60XV low level transverter output
option for the K2 and before the introduction of our XV transverters. The Elecraft XV50, XV-144 and XV-222

may all be stacked and fed off of the same 28 MHz IF drive line. These transverters have internal switching relays that
drop the unused transverters off the IF bus. No external switching is required. When connected to the K2’s AuxBus via
the KIO2 or KPA100, the Elecraft XV transverters will automatically turn on/off and connect to the IF bus as each
transverter band is selected on the K2. The section on switching though is still a good description of how to switch
non-elecraft transverters. Also note the the KRC2 band decoder for theK2 (and other rigs) provides switching outputs
for the transverter bands.)

Transverter Overview

Transverter is a contraction of the term transmitting and receiving converter. It is easily visualized as a new

“front end RF section for your existing HF radio and consists of a common local oscillator for receive and transmit,
mixers, and assorted RF amplifier stages. The transverter will convert receive and transmit frequencies from one
amateur band to another. The transverter typically has a means of being switched between receive and transmit, e.g., a
relay or PIN diodes. By utilizing an existing HF radio as an IF amplifier, (typically on 28 MHz) the performance of
the HF radio can be duplicated on any VHF band. Generally, a low level transmit signal/ receive connection, and
TX/RX switching, will interconnect the HF radio and the transverter.

There are many advantages inherent in transverter operation on the VHF and UHF bands. The first and most
obvious is the tremendous cost savings, by not having to duplicate an entire radio as you go to new bands. Other
benefits will depend on your specific VHF application to some extent. As a K2 owner, you are no doubt well aware of
the characteristics that make the K2 stand out among HF radios. Obtaining great performance on VHF/UHF can be
elusive when multi-mode standalone commercial transceivers are employed. In almost all cases, there is little attention
spent to CW operation. Filter options are poor or often non-existent. Receiver dynamic range can be quite poor.
General ergonomics can be difficult with small boxes, multiple questionable features, confusing menus, and limited
space for button pushing! A transverter will re direct the full feature set of your HF K2 to your favorite VHF band
with little change in performance. Receive dynamic range difficulties on VHF can be significantly more pronounced
than at HF due to increased antenna gain, propagation differences, and lower angle of radiation when compared to, say
20 or 80 meters. Having a crunch-proof receiver can pay great dividends for the VHF Dx’er or contest operator as
well as the casual user. There are also some bands that are lacking in choices for standalone VHF/UHF radios. The
222 and 902 MHz bands are cases in point. The same can also be said of all the bands above 1.2 GHz. To get a good
signal on any of these bands, a transverter is the only way to go.

The transceiver is often called the “IF” to reflect the role it plays. Common IF frequencies for transverters are 28
MHz and 144 MHz, although some other HF bands are also used in some instances. A 222 MHz transverter, such as
the Downeast Microwave 222-28K, is connected to the RF output jack of an HF transceiver and to a 222 MHz antenna
at its own RF output port. It receives a low level transmit signal from the HF transceiver in the 28 MHz range and
converts the signal to 222 MHz and then amplifies its’ own RF output. When not transmitting, the 222-28K receives
222 MHz signals and passes them along to the transceiver as a 10 Meter signal.

Transverter architecture will fall into two broad general categories. Category 1 uses a single RF connection and
generally requires a few to ten watts of drive from the HF transceiver. TX RX switching can be obtained from RF
sensing, or keying lines between transverter and HF transceiver. Such designs can allow a 10 watt 144 MHz
transceiver to operate on 50 MHz for example with a minimum of fuss. A small 20 meter QRP rig can easily operate
on 144 MHz. Simplicity is the rule. Such a setup is shown in FIGURE 1. Category 2 is somewhat more complicated by
using separate receive and Transmit paths between the radio and transverter. The TX level is typically designed for
somewhere near 1 milliwatt, but may accommodate ranges up to 500 mw or down to –20 dBm with pot adjustments in
the transverter. This layout will allow for changes for station performance improvements. New receive preamps and
transmit amps may be added without complex switching modifications. In many cases, a sequencer may be installed to
control switching of coax relays, transverter, preamps etc. etc. FIGURE 2 demonstrates the Category II transverter

1

hookup.

The K2 does not allow for 1 milliWatt transverter operation directly as yet, but there is a simple remedy to
allow K2 operation with split receive and transmit. (Ed. Note: The K60XV option for the K2 now provides a

separate low level drive output for transverters.) The 160 meter band option includes a separate receive terminal that

can be used on any HF band, so, by adding a 160 meter kit, the separate TX and RX path problem is resolved. Most
operators install a plug in attenuator on the main output BNC jack. These may be simply made with carbon
composition resistors. The value may be tailored to the power level required by the transverter, A 30 dB pad will
attenuate one watt from the K2 to the one milliwatt level. This will be explained fully in the Transverter Connection
Details section below.

2

3