EME203 Crystal Filter Kits

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EME203 Description:

The Mini-Kits EME203 Crystal Filter Module is part of the M1 series building blocks to construct a high performance M1 HF Transceiver. The M1 HF Series Kits have been designed to allow easy construction due to the use of mainly leaded components for those that don't like surface mount devices. SMD components are only used when required due to availability of components, or for better performance. The crystal filter modules however use a number of SMD components, but we have used the larger 1206 size capacitors in the crystal filter circuit. The RF modules are all designed with a 50ohm impedance making it easy to interconnect with the other M1 series modules, and your own homebrew circuit designs.

The filter board can be used to construct either a 5 pole or 8 pole crystal filter, and incorporates SPDT analogue switches to either isolate the filter, or switch it in for either the RX or TX signal paths. Multiple filter boards can be stacked using extended header connectors, and controlled through a single 16 Pin IDC header connector, making it easier to interface to logic circuitry. The filter designs have been made using the DJ6EV Dishal software and tested using a DG8SAQ vector network analyzer. The filters input and output have been matched for 50ohms to make it easier to incorporate in many different projects. See the Block diagram for the connections to this module.

The following filter Kits are now available to suit SSB, CW, and AM modes. We may produce further bandwidths at a later time.

9M-8-2.5k KIT ( 9MHz 8 Pole 2.5kHz @ 6dB ) for SSB

9M-5-6.0k KIT ( 9MHz 5 Pole 6kHz @ 6dB ) for AM

9M-8-0.5k KIT ( 9MHz 8 Pole 500Hz @ 6dB ) for CW New Product 16/3/16

Some of these performance figures may change with future tests.

Kit Constructors Alert:

1/ All Kits after February 2016 have had a modification added to quickly discharge C6 when the regulator is turned off. When changing modes, this causes a problem with the filter still being in circuit for a couple seconds until C6 discharges, and also caused a voltage glitch from the TS5A3157 switches on pin 5 when going from TX back to RX mode. A 1K resistor has been added on the regulator output to ground as a discharge path for C6. The resistor can simply be mounted vertically in position C3 on the top of the board. This places it in parallel with C3 that is under the board. A picture of the modification can be seen below.

EME203 Kit Notes:

The images below show both sides of the board. The module uses a number of SMD devices that could not be avoided as it makes the module more compact and offers better performance.

1/ Stacking Modules: The first module board will require SMA connectors to allow connection to the other M1 series modules. SMA connectors are not used on additional stacked filter modules so don't fit them. Additional Filter modules are stacked using stackable headers as shown in the pictures below. Only one connection to the 16 Way ribbon cable from the logic control is required to the top stacked filter module. A HDR-M8-2R connector is used to interface the top stacked module to an IDC16S header that is crimpd onto the 16 way IDC cable for the logic control.

2/ M3x12mm brass spacers are used to stack the module boards. There has been no measured difference with RF losses or impedance mismatch when nylon spacer are used to save cost.

3/ The modules should be kept well away from the BFO and IF amplifier modules as performance can be degraded due to RF feedback or the BFO getting into the filter modules.

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EME203-1A Top View
Top view of the EME203 8 Pole SSB Filter Module
EME203-2A Bottom View
Bottom View of the EME203 Crystal Filter Module
Crystal Grounding
The above picture shows how the crystals need to be grounded for correct operation of the filter
Logic Connection
A 16 way right angle male header is used to connect the module to the 16 way ribbon cable
Mode Select Link
The mode selection link can also allow the SSB filter to be used on CW by placing a link across both SSB and CW
R5 1K Resistor Mod
This picture shows the 1K resistor modification to Kits after February 2016 to quickly discharge C6.

EME203 Kit Tests:

EME203-SSB-Ver1
Frequency response of the original 9MHz 8 pole 2.5kHz @ 6dB SSB Filter using matched ECS-90-18-4X 18pF load type crystals to within 10Hz and 1% capacitors. Notice the centre frequency is just below 9MHz and the return loss and
EME203-SSB-Rev2
The SSB filter was improved by adding a 3.3pF capacitor across CK12 which improves the ripple and also return loss compared to the original filter. Kits after March 2016 have the improvement.
EME203-CW-Ver1
Frequency response of the original prototype 9MHz 8 pole 500Hz @ 6dB CW Filter using matched ECS-90-S-4X type crystals to within 20Hz and 1% capacitors. Notice the high loss of the filter that will reduce the gain of the receiver and the actual 400Hz BW
EME203-CW-Rev1
Frequency response of the final 9MHz 8 pole 500Hz @ 6dB CW Filter using matched ECS-90-S-4X type crystals to within 20Hz and 1% capacitors. The filter was modelled in Dishal as a 700Hz BW filter which when built measured 548Hz BW @ 6dB
EME203-AM-Rev1
Frequency response of the original 9MHz 5 pole 6kHz @ 6dB AM Filter using matched ECS-90-S-4X 18pF load type crystals to within 20Hz and 1% capacitors. Notice the centre frequency is around 4kHz high.

Changes and Modifications:

1/ The 9M-8-2.5k SSB filter has been improved by placing a 3.3pF capacitor across both CK12 positions on the board. The plots of the original filter and improved filters are here. Kits after March 2016 have the improvement.

2/ All Kits after February 2016 have had a modification added to quickly discharge C6 when the regulator is turned off. When changing modes, this causes a problem with the filter still being in circuit for a couple seconds until C6 discharges, and also caused a voltage glitch from the TS5A3157 switches on pin 5 when going from TX back to RX mode. A 1K resistor has been added on the regulator output to ground as a discharge path for C6. The resistor can simply be mounted vertically in position C3 on the top of the board. This places it in parallel with C3 that is under the board. A picture of the modification can be seen here.