ME14-X & ME28-X  IF RX/TX xtal preselector


1. Introduction:

       ME14-X and ME28-X type IF preselectors christal filters can be utilised to any type transverter furnished with 14 MHz or 28 MHz IF output.

      The equipment comprises 12 Xtal filters tuned for the CW and SSB band sections in accordance with the IARU band allocation. The frequency range is 14.030-14.400 MHz, 28.030-28.400 MHz respectively. The filters prevent the strong signals of nearby strong stations entering into the HF base station, furthermore significantly decreases the disturbance of the running station occurring in the receiver of the searching station located at the same QTH (50 – 300m).
On VHF & UHF transverter mode we can use the filter in the IF TX line also, to kill the unwanted side noise, click of the driving transceivers.

2. Description:

14 MHz and 28 MHz versions of the preselector equipment (ME14-X, ME28-X) are available. The minimal set-up comprises 5, while the maximal one 12 pcs. of Xtal filter units. The CW filters are available in +/- 5 KHz/3 dB or +/- 7,5 KHz/3 dB, while the SSB filters in +/- 12,5 KHz/3 dB, or +/-15 KHz/3 dB bandwidth versions.
You can select the passband centre frequencies enlisted below:

1 28.040MHz 14.040MHz +/-7.5KHz/3dB,+/-25KHz/40dB*
2 28.055MHz 14.055MHz +/-7.5KHz/3dB,+/-25KHz/40dB
3 28.070MHz 14.070MHz +/-7.5KHz/3dB,+/-25KHz/40dB
4 28.085MHz 14.085MHz +/-7.5KHz/3dB,+/-25KHz/40dB
5 28.100MHz 14.100MHz +/-7.5KHz/3dB,+/-25KHz/40dB
6 28.115MHz 14.115MHz +/-7.5KHz/3dB,+/-25KHz/40dB
7 28.170MHz 14.170MHz +/-15KHz/3dB, +/-40KHz/40dB*
8 28.200MHz 14.200MHz +/-15KHz/3dB, +/-40KHz/40dB
9 28.230MHz 14.230MHz +/-15KHz/3dB, +/-40KHz/40dB
10 28.260MHz 14.260MHz +/-15KHz/3dB, +/-40KHz/40dB
11 28.290MHz 14.290MHz +/-15KHz/3dB, +/-40KHz/40dB
12 28.320MHz 14.320MHz +/-15KHz/3dB, +/-40KHz/40dB
13 28.350MHZ 14.350MHZ +/-15KHz/3dB, +/-40KHz/40dB
14 28.380MHz 14.380MHz +/-15KHz/3dB, +/-40KHz/40dB

* +/- 5KHz/3dB CW and +/-12KHz/3dB SSB filters is available to any chanels!

Prior to turning the equipment on you need to select 1 or 2 cable IF mode by means of setting J1 jumper mounted on the main board. Setting “ON” selects separate RX and TX cable, while “OFF” selects common RX/TX cable mode. (In case of request the equipment is shipped suitable factory setting.)

Connect the preselector accordingly to your transverter and base HF radio.

2x IF cable transverter connection                          Single IF cable connection

The equipment shall be supplied from a +12…15V / 0,3A stabilised PS. (Option). The centre pin of the DC connector is for positive supply voltage.
During transmission PTT1 and PTT2 connector pins have to be grounded. You can connect here two separate base radio’s SND (send) outputs. (I.e. the running to PTT1, and the searching station to PTT2)Connection 1xIF cable and 2x IF cable.

3. Operation:

Turn the equipment on pressing the “ON” knob. As a result, you can read the message displayed as follows:

The equipment switches to the first channel (CH1) after a few seconds delay.

Select the desired passband centre frequency (minimum 5, maximum 12 channels) turning the CHANNEL knob.
Pressing the knob “PRE” turns an IF preamplifier stage on/off
(It’s based on a GALI-41 type high dynamics MMIC.)
Pressing the knob “ATT” turns a 10 dB attenuator stage on/off.

You can use both PRE and ATT in the same time. In this case the total gain of the 2 stages is 5-6 dB (i.e. 1 S grade)Pushing the “CHANNEL” knob turns the actually selected passband filter off, thus the preselector equipment switches into “’BYPASS” mode. Both PRE and ATT function settings remain active in BYPASS mode.


Pressing CHANNEL knob again reactivates the formerly selected passband filter.

Transmission (grounding any of the PTT inputs) turns both PRE and ATT off. The  main(runing) radio IF transmit signal going accross the selected filter,( e.g. CQ channel..)
except when we are on *BYPASS* mode. The 2nd radio(multiplier) station IF TX signal going directly to the transverter - not filter in the line.The max IF tx level of radios is +5dBm! Higher tx level can kill the xtal filters!
You can use both  type filters easy in  2x radio mode on your contest station.

4. Construction:

The filter is accommodated in a 240x190x60mm size metal box. That is, the equipment’s basic “floor” area complies with that of the transverters we manufacture.


The in/output connectors, the box of the filters containing maximum 12 pcs. of Xtals filter units, the IF preamplifier, attenuator, and the switching relays are mounted on the chassis.

The CW and SSB filters are of plug-in configuration. The filters can be plugged in in any sequence. The filter position and associated passband centre frequency can be programmed in PRG mode, together with the number of built-in filters. The user later may extend the equipment adding the optional filters ordered, and can program the displaying accordingly. The filter units are high slope rate 4-pole filters, and the L-C components have been tuned for 50 Ohm in/output impedance. All of the filter units are factory tuned; both the insertion loss and the impedance are optimised for 50 Ohm.

Controll panel:

The programmable controller (PIC), the 5V DC stabiliser and the relay controlling FETs are mounted on the control panel together with the front panel’s control knobs.

The display is a 2 lines, 16 characters per line LCD unit connected to the controller via an I2C bus.

5. Specification:

Insertion loss:                                    
<2.0dB on CW, <2.5dB on SSB
Filters ripple:                            
IF amp. gain:                                       
typ. 13dB
RX attenuator:                                 
P1dB           :                                       
RX attenuation on neighbour rx ch:   
min. 30dB
RX attenuation on other  rx  chans:   
min  50dB

max. IF input TX PWR:                   
Insertion loss:                                    
max. 3dB
TX sign. ripple:                            
TX attenuation on neighbour ch:    
TX attenuation on other   chans:     
 min. 50dB
PTT1 inp:                      
 GND on TX, main TCVR
PTT2 inp:                       
GND on TX  2nd TCVR( multiplier stn)

Power supply:                 
External, +12...15V/0.3A
  240 (W)x 60(H)x 190(D) mm
Weight      :                     

6. Program mode:

The filter equipments are shipped to the users factory programmed and tuned for the required frequencies. On condition that you order additional filter units, you can modify the program entering the number of channels and the new passband centre frequencies using the program mode. However we are shipping additional optional filter units exclusively for registered Preselector customers.