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Thursday 24 January 2013

472KHz KX3 Transverter

Started to layout a manhatten construction last night, I might transfer to a PCB and 'pretty' the build eventually. I am going to use my KX3 as the RX and drive of the TX side of a 472KHz setup. I also have an Softrock V6.2 I modified for 500KHz already but it is a bit high I can lower it a bit which might be good as a second RX and sort of panadapter.

The KX3 will require an external transverter setup as the LPF would never fit inside.

The design is loosely...

RX side:
A main HF band colpitts LO, exact frequency will be down to the mixing schema and the KX3 transverter options then use a DBM either one made from torroids and diodes or a packaged version I will look at 602/612 and ADE-1 or and SBL-1 to mix UP the RX 472KHz signals to the KX3 RX IF. It all depends on the response to tests. I have a 500KHz xtal in a test oscillator that I can pull DOWN and I will add attenuation so can do the typical 1uV and 50uV S meter calibration tests to determine which has the better response.

On the TX side:
Use the same HF band LO as RX, and DBM (decision to be defined) to mix DOWN the KX3 TX IF to 472KHz. As G3XBM has pointed out and it is in the spec sheets you need to limit the input power to the mixers to c10mW so I will need to 'play' with attenuation. The output will be followed by a 1W PA and then a 25W PA using IFR510 and output LPF similar to the GW3UEP versions in an earlier post. SM7UCZ gave me some interesting BUZ MOSFET so I might also try one of them.

ATU (see G3XBM ferrite rod design) and antenna will as per 500KHz either be /P beach thing using a 10m pole and loading coil (I used a 2 litre coke bottle wound with tapes every 10 turns) or a 140ft LF long wire I have used successfully at home, with a homebrew variometer made from a section of 6" Yellow gas pipe (when they replaced the mains to the street I asked for an off cut if they had one and was given a couple 6 foot lengths!) and a smaller 3" white PVC pipe that would go inside.

The easiest HF LO to choose might be 28MHz so that the dial reads 28.472 to 28.479 giving 472 to 479 KHz but as I mentioned it depends on the KX3 transverter setup Elecraft said if you want 472KHz build a transverter and use 7MHz IF.

I have a second KX3 that does not have the AUTO ATU so will need to make sure the transverter matches well.

KX3 RX on 472KHz directly is poor so you could not use it as you might an FT817. As the circuit has not been released and there is no obvious place where you could inject a 472KHz RX signal. I am sure it is possible but it is not recommended that you  bypass the KX3 front end filters that will effect normal operation.

It 'might' be possible to control from the KX3 menu system..

From KX3 manual..Revision B4 June 1, 2012
Copyright © 2012, Elecraft, Inc.

Page 5

Keyline Out and GPIO (ACC2)
The 2.5-mm stereo ACC2 jack provides a keyline
output (ring contact) and a general-purpose 3-volt
logic signal (tip contact).
The keyline output goes low during transmit, and
can be used for transmit/receive switching of linear
amplifiers and transverters. For keyline voltage and
current limits, see Specifications.
The general-purpose signal, GPIO, can be set up for
various equipment control functions. For example,
it can send band-change information to Elecraft
XV-series transverters. See the ACC2 IO menu
entry for a full list of uses for this signal, as well as
hardware interface requirements.

Page 9

Transverter Bands
Nine user-definable bands are provided for use with
transverters. These can be used with the Elecraft
KX3-2M internal 2-m module, Elecraft XV-Series,
or other transverters.
The KX3 does not have a low-level
transverter output; transverters are driven from
the main antenna jack. This requires the use of
transverters that have a common receive/transmit
antenna jack and associated T/R switching. Consult
the transverter manual for drive power limitations
and switching requirements.
The ACC2 jack provides a keyline output for
keying transverters. The ACC2 jack also provides a
GPIO pin that can be used to select among multiple
transverters based on the band selected at the KX3.
This is further explained below.

Transverter Band Setup

Transverter bands are set up using the XV menu
entries, as follows:
? Locate the XVn ON menu entry. Tap 1 – 9 to
specify which transverter band to configure. Set
the parameter to YES to enable band n.
? XVn RF sets the operating frequency (MHz).
? XVn IF specifies the I.F. band (7, 14, 21, 28, or
50 MHz). Use 50 MHz for the KX3-2M option.
? XVn PWR sets maximum KX3 power output
for the current transverter band in watts (0-1).
Use 0.3 watts for the KX3-2M option.
? XVn OFS can compensate for frequency offset
in the transverter’s oscillator. (An offset is not
required for the KX3-2M module, since its
oscillator signal is derived from the KX3’s
main synthesizer. If there is a frequency error,
calibrate synthesizer using REF CAL.)
? XVn ADR should be set to TRN 0 for use with
the KX3-2M module. It can also be used to
specify an optional Elecraft XV-series
transverter selection address. Only addresses
TRN1-TRN7 are recognized for this purpose.
To select XV-series transverters using this
method, set MENU:ACC2 IO to TRN CTRL,
and connect the ACC2 jack’s GPIO pin to the
transverter’s auxBus line.

Page 35


Determines the function of the GPIO signal (ACC2 jack, left side panel):
OFF (output, 0 V), ON (output, 3 V), LO=PTT (input; apply 0 V or ground to
activate PTT), HI=PTT (input; apply 3 to 5 V to activate PTT), LO=Inh (input;
0 V inhibits transmit), HI=Inh (input; 3 to 5 V inhibits transmit), TRN CTRL
(output; XV-series transverter control using Elecraft auxBus prototcol). If the
GPIO signal is inhibiting transmit, the TX icon will flash as a reminder.

NOTE: External interface circuitry may be required. The GPIO pin is a 3-V
logic input/output with a 500-ohm series current-limiting resistor. It is tolerant of
0-5.5 VDC when used as an input. If a voltage outside this range is to be used,
insert a larger series resistor. (Example: when an RS232 RTS signal is used to
activate PTT, use a 2.2 to 10 K series resistor.) When the GPIO pin is used as an
output, its 3-V logic high may not be sufficient for use with some equipment. In
this case a 3-V to 5-V level translation circuit can be used.

Page 37

{band} In

Allows you to remove one or more bands from the BAND rotation. Use BAND
up/down to select bands, then set them to In or Out using VFO A. (Works with
transverter bands, too.) You can still get to mapped-out bands using memory
recall, direct frequency entry, or computer-control commands.

Page 39


If set to NOR, TUNE power level follows the POWER knob. Otherwise,
establishes a fixed power level for TUNE, overriding the present POWER knob
setting. Note1: TUN PWR does not pertain to ATU TUNE , which always uses 2
or 3 watts and is internally controlled. It also does not apply to transverter bands
using the low-power KXV3 output (XVTR OUT).

Page 40


Tap 1 – 9 to select the applicable transverter band (1 - 9). Set parameter to YES
to turn the transverter band on.


Lower edge for transverter band n (1-9); 0-24999 MHz. (Tap 1 – 9 to select
applicable transverter band.) Normally, 144 would be used for the K144XV
internal 2-m module. But if the K144XV is being used as an IF for a higher-band
transverter, you can set it to the lower edge of the higher band.


Specify KX3 band to use as the I.F. for transverter band n (1-9) . (Tap 1 – 9 to
select the transverter band.) I.F. selections include 7, 14, 21, 28, and 50 MHz.
Use 50 MHz for the K144XV internal 2-m module.

H 0.1

Sets upper limit on power level in watts for XVTR band n. Applicable only to
external transverters, not the KX3-2M module. Tap 1 – 9 to select band.
The KX3 does not have a low-level transverter port, so external transverters must
have their own T/R switching and be able to handle the specified power level.

Offset (–9.99 to +9.99 kHz) for transverter band n (1-9). (Tap 1 – 9 to select
transverter band.) Compensates for oscillator/multiplier chain errors in external
transverters. Not applicable to the internal KX3-2M module, which derives its
signal from the KX3’s synthesizer.


Assigns optional band-decode addresses to transverter bands. Addresses TRN1-7
can be used to select Elecraft XV-series transverters if the ACC2 IO menu entry
is set to TRN CTRL and the transverters are connected to the ACC2 jack
(tip=auxBus, ring=key out). TRN0 is used with the KX3-2M module (internal).
Tap 1 – 9 to select the transverter band; rotate VFO A to select the address.
To configure an Elecraft KX3-2M 2 m module as XVTR band 1, set XV1 ON to
YES, XV1 RF to 144 MHz, XV1 IF to 50 MHz, and XV1 ADR to TRN0. The
XV1 OFS and XV1 PWR menu entries are not applicable in this case.

1 comment:

g4fre said...

Be aware that the KX3 software currently doesnt support these transverter band settings, Wayne has still to fix the software.

I use a true transverter (ie has a receive AND transmit mixer) to put my K3 on 477kHz. It uses a 10MHz LO which is the 10MHz reference i feed to drive the K3 which is very accurate