ME2T-PRO-II & ME2HT-PRO-II 144MHz Transverter

2016-11-24

 













 

ME2T-PRO-II High Performance 2m transverter

After the successful ME2T-PRO transverter project we decided to modify the -PRO version.
We built in the best Mini Circuits dual ballanced mixer the HJK-3H. The new built in IF amplifier (ASF360 from ASB) has low noise,
combinated with very good dinamic range on receiving section.
You can find the block diagram of the base 100mW transverter  unit here.
The built in military class low phase noise TCXO provide easy work also on FSK modes.Optional AXTAL 0.5ppm TCXO also available!
The transverter can work between 144-146MHz  with low RX NF and high OIP3.
The Mitsubishi RF module provides good IMD signal and 30W output power.
The ME2HT-PRO-II basically same as ME2T-PRO-II but furnished with 80W RF module.
Before of first operation, check the setup description.

Local Oscillator

The high stability  TC23-5T  type  TCXO by PDI  ( +/-1ppm btn 0-50 degr. C ) with low phase noise gives  +3dBm signal on 116.000MHz. (or on 130MHz)
The TCXO frequency can be adjusted with inner trimmer capacitor (+-2ppm) but it's not necessary because the stability is better than +-1ppm/Year.
TCXO stability and  the phase noise is better then most modern transceiver's phase noise.
The output signal of the LO is about +23dBm, it produced by pair of ASB ASL550 3rd generation MMIC. The built in 2x 5th order filter provides  clear output signal.

The simulated caracteristics of the 5th order LPF filter:                                               


The measured   TCXO phase noises: PDI

 

 

 

 

 

 

 

 

 

 

 

 

 

 

                                                                                         

                            

                                                                                 

 AXTAL 116MHz    phase noise                                                                     AXTAL 130MHz phase noise

 

 

 

 

 

                                                  

 

 

 

 

 

 

 

 

We can check the +23dBm output signal on M3 measureing pin. This signal is attenuated by -10dB  to the TX  balance mixer.( CSYM-1815)
We are using HJK-3H+ type (+37dBm IP3)mixer in the RX side. We can check  the real RX and TX  LO signals on M2 and M1 points with DC voltmeter.

RX/TX

The 144-146MHz input signal passes through the input filter to the input PGA103+ LNA. The gain is approx. 20dB, the noise figure is 0.7dB,
the OIP3 is >30dBm! PGA103+ has an exceptional performance of low noise figure, high gain, high OIP3, and low bias current. The stability
factor is always kept more then unity over the application band in order system environment.
Impedance of the MMIC is 50 Ohm both I/O - it provides easy connect on the output 3rd order BPF.
PGA-103+ produces about +9..10dBm IIP3!


                                                                                           The simulated caracteristics of the 3rd order BPF:
 

 

The 144-146MHz signal goes through the band pass filter providing a suitable selectivity. The balanced mixer MX1 mixes the input signal down to 28-30
MHz(or 14-16MHz)  loosing approx. 6 dB in the process.  The  IF signal is amplified by approx.17dB in a low noise, high dinamics ASB ASF360 IF amplifier.
 The final PI filter increses the selectivity considerably. The output signal is can set to optimal value with the RX gain potentiometer.

                                        Chracteristics of diplexer unit:                                                           Caracteristics of 28MHz IF amp. & LPF filter:
 

 

 


          Diplexer full  simulation 
 

The transmit mixer, MX2 only needs approx. -10dBm 28 MHz IF signal from the transceiver. A suitable level can be achieved by adjusting
P2(TX) in the attenuator. Lot of transceivers  has lower or much higher IF output level. To solve this problem we built in
an additional jumperable  and variable 5W/-20dB attenuator. You can switch on/off  easy the attenuator with different jumpers.
The fine level setting possible with the potentiometer P1 on the attenuator unit across the slots of the top cover.
We solved very low level IF out problem of most ICOM radios( -20dBm)
We built in +15dB gain jumperable IF amplifier so ME2T-PRO-II is usable easy to this radio types.
The 144 MHz TX signal behind the MX2 mixer is  filtered through a two-stage band-pass filter  before being amplified in a BF996.

Simulated characteristics of the 2nd order BPF:                                                    ME2T-PRO spectrum: ME2T-PRO_spectr (pdf)


The G2 of the BF996 connects to the ALC circuit on the control unit and to the rear panel PWR potentiometer. We can reduce the final output power to about 5-6Watts.
The controlled gain BF996 amplifier continues the final ASL550 amplifier to a level exceeding more then 100 mW. Through the final pi-filter we can
reduce the harmonics of the TX signal.

                                        Simulated 144MHz LPF :                                                                Measured 144MHz LPF:



2m module PA unit

We constructed >25W output amplifier to the base transverter unit. It's built  with RA30H1317M Mitsubishi module, by Mitsubishi datasheet and applications.
The output signal of the transverter drives the RF module across -3dB attenuator. We set the RF module to AB1 class by a simple circuit applicated by Mitsubishi.
The ME2HT-PRO-II  model PA contains RA80H1415M type 80W RF module.
The output signal led to "N" type  2m ant connector across a harmonics filter and a built in NEC EB2-12NU type smd RF relay.
The final unit has MON output to check the output power connecting to the control unit LED bargraph PWR meter and ALC circuit.
The PA contains simple temperature sensor to check the temperature of the heatsink. The external heater fan module is standard in case 60W transverters,
option in case the 30W model.

CONTROL UNIT

In order to monitor output power, we use an LM3419 based LED bar graph, implemented on the DP6 control unit. You can find  the high
current DC relay too on this PCB, together with the ALC circuit  and the circuit of the external fan speed regulator. The external (optional) fan's speed is reduced by 50%  during RX state.
 In case of long TX periods, when the final PA module's heatsink temperature exceeds normal, then the circuit increases the speed of the DC fan. . The speed depends on the heatsink temperature. We can calibrate the normal fan speed with the P2 , the ALC level with the P3 potentiometer.
The  LEG-12 relay is switching the Vpp voltage to the PA unit. The calibration of the output power on the bargraph, is possible with P1 pwr poti on the DP6 unit.


Switch/attenuator panel


People use different IF level transceivers from home or / portable operation. The jumper selectable attenuator solves the problem; let it be either high or low level  IF signal transceiver.
 You can either set ON or OFF the 5W attenuator, what is more, you can also easily choose single or dual cable IF operation with these built in jumpers.
The unit contains switching circuit associated to the  external PA's (red colour RCA, SND output, (capable to switch max +50V,1A)

The PTT circuit uses two MJD127 devices on the tranverter unit for the RX/TX switching.TX when the PTT is grounded. 
 The PA circuit includes a sequencer, providing suitable delay in the TX key signal when activating first the relays of the external PA relay, then the antenna relay and RF module first stage of the transverter. This means that the TX output  is delayed approx. 50 ms after the antenna relay is activated. 
The antenna relay of the ME2T-PRO and the external PA switches without any TX signal present.

Position of built in attenuator jumpers

Low PWR IF input (-20..+27dBm)
2x IF cable connection

Low PWR IF input (-20..+27dBm)
1x IF cable connection

J1 ON

ON

J2 OFF ON
J3 OFF OFF
J4 OFF ON
J5 ON OFF(ON- 2nd RX)

 

High PWR IF input (27..+37dBm)
2x IF cable connection

High PWR IF input (27..+37dBm)
1x IF cable connection

J1 OFF

OFF

J2 ON ON
J3 ON ON
J4 OFF ON
J5 ON OFF(ON-2nd RX)


If you use single IF cable between your radio and the transverter, you connect it to transverter IFin BNC.
In this case the IF-out connector is not in use. If you want to use a 2nd (e.g. SDR) RX, then switch J5 into ON state. (Only in case of single IF cable mode!)
Don't forget to connect the PTT cable between radio SND connector and ME2T-PRO  PTT input! Otherwise  the IF power (5W) kills
the transverter IF output part. (single IF cable high IF power version)The output is protected by antiparallel diodes but it does not help in case high IF power!
Never apply more than 5W IF level to the attenuator!
In order to protect the RX of those who forget to connect the PTT line, we built in an IF RF VOX circuit in the new version.
The RF VOX interacts at an IF level exceeding +27dBm, but only in case single IF cable mode.

Construction

The base transverter is built on a 1,5 mm double sided glass-fibre epoxy PCB; it is fitted into a standard metal sheet box measuring 148 x 74 x 30mm.
PA unit is fitted into 148 x 55 x 30mm standard box. Both are manufactured with SMD technics.
The external box of the transverter is constructed from 1mm painted iron plate. The heatsink is 150x55mm ALU  heatsink material.
If you use the ME2T-PRO continuously on FSK mode you can order optional fan module (2pcs 50x50mm DC fans on  holder plate).
No overheating problem occours in  case normal room temperature while operating on CW, or SSB and contest mode.
You can find on the front panel the ON/OFF switch, the LED bargraph power meter the PWR potentiomter. The latter reduces the output power to a desired level, down to to 5-6 Watts to drive an external  FET PA's.

High performance contest station with ME14-X or ME28-X RX/TX crystal preselector:

Comments, suggestions  are welcome!
 

TECHNICAL PARAMETERS

Frequency range                                                    144-146MHz
IF frequency range                                                 28-30MHz or 14-16MHz
Emission modes                                                     CW,SSB,FM,Digital
I/O impedance                                                       50 Ohm/unbalanced  Ant-"N" type, IF 2x BNC ( 2m separate RX "N" optional
Operating temp. range                                            0-+50C
LO accuracy @ 20C                                              1ppm PDI TCXO
LO accuracy @ 0-50C                                           +/-1ppm PDI TCXO ( +/-0.5ppm with optional AXTAL TCXO)
Input voltage                                                           13.8V +/-5%
Power consumption                                               0.48A on RX, 5A/TX ( 10A, ME2HT-PRO-II 50W version)
IF power input                                                       -20...+37dBm
IF input VSWR                                                     1:1,1typ, max 1:1,3
Output PWR                                                          ME2T-PRO-II=30W, ME2HT-PRO-II=50W RF,variable from 5W to peak PWR
TX harmonics                                                        min. -70dB
IM3                                                                       -33dBc/ 25W output
PTT  control                                                          Contact closure to GND
SND output                                                           Open collector, +50V/1A max.
RF VOX                                                               Available, starts >27dBm IF input
RX noise figure @ 20C                                          1dB ( overall)
RX gain                                                                 max 25dB ( variable)
RX OIP3                                                               typ. +35dBm, min. +30dBm
RX  IP3                                                                 typ. +10dBm, min. +8dBm
Image rejection                                                      >85dB
Dimensions                                                            240x260x70mm ( incl. optional fans)
Weight                                                                  1.6kg
Case                                                                      Iron plate, @1mm
                                                                   


 

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