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Amateur radio filter systems



Preselektor Stirnseite
9-Kanal Preselektor,

front view SW-preselector in case

backside SW-preselector in EUROMASS II case

top_view SW_preselector
Topview SW-preselector

WARC bands include ......
160, 80, 40, 30, 20, 17, 15, 12, 10m

more infos here im web.....
9-channel / 9-band Preselector with high selection (>30dB), strong signal, all filters switchable, TX/RX switching, 16dB attenuator,  18dB Pre-Amp. with OIP3= 34dB,
developed for multi band or more-operator-use at your place

Measurement diagrams are below this text, scroll down to see it.
Controller unit for short wave preselectors
Manual for 9-band preselector, (german)
Circuit plan 9-band / 9-channel preselector (public version)
Description of short wave preselector with band-pass-filters
The preselector should use to reduce the strong outband signals at TRX inputs and reduce blocking effects in radio mixers. The system is built with high quality Chebyshev band-pass filtern 3. order. Outband signals are suppress with
> 30dB.

This filter have a TX / RX switching unit with up to 300 watts load, have a switchable 16dB attenuator, and 18dB pre-amplifier with OIP3 ca. 34dBm @ 22dBm, 1dB compression (W7IUV concept with a 2N5109) for strong signals
This filter is built with COG/NPO smd capacitors in size 1206 and with Amidon iron powder cores in size T44/T37.
The filter is designed for strong signals and suppress strong outband signals from other radio stations or broadcasting services.
All filters are switched with high quality signal relays and placed between two common lines for antenna input and transceiver output.
All filters ways without activation are switch off from common lines and grounded at input and output with relays.
The TX/RX switch works with the same 10A relays as we use in our low-pass filters. This system part can controlled with PTT line or integrated VOX function. The VOX circuit accept low power levels with ca. 5watts and switch to TX mode (bypass preselector) and with hold-on delay back to RX.
All control lines work in low active logic and also at remote interface available (sub-d 15 pin). If you switch a control line to ground level, the fuction is active, a open line is inactive.

The pre-amplifier circuit is from W7IUV and works with a 2N5109 transistor. I know this is a old one, but its provide exellent data. Good back coupling and high collector currents provide stable 18dB gain and stability for strong signals.
OIP3= 34dBm is very good for this circuit and a lot of OM's love this concept. This circuit works with very strong signals and will not provide intermodulations when a station close to you go to TX.
Tests show us, new concepts with units from Mini Circuits or Analog Devices are not really better. The linearity and strong signal protection works only with high currents and a very linear gain curve.
The 9-band preselector include TX/RX switching have dimensions 160 x 100 mm (Europa card format). The pre-amp. have a own board and is placed over the TX/RX switch part of the filter board.
The pre-amp pcb provide the remote interface (sub-d) for control and the interface for the controller / display unit and a second power supply socket.
The controller board is a option for this system and based at a micro controller from Atmel, have a 2 lines and 16 digit LCD display and a 6 button panel for control functions. Whith buttons con controll all functions of the preselector and the display show the status of ervery part.
The controller unit provide also a serial CAT interface for remote control with a PC system.
Pre Amp Board

9-Band  preselector, top layer
Pre_amp Board
Pre-amp pcb with remote interface
9-channel / 9-band short wave preselector with aufgesetztem pre-amp board
The signal way through the preselector go from antenna input over TX/RX switch, to 16dB attenuator, then to the band filters and last station is the pre-amp circuit.
If pre-amp or attenuator not used, relay contacs shorted these circuits. When the preamp is not used, the power supply for this circuit is switch off.
With this filter is it possible to send the RX signal trough a band pass filter with bandwith of the selected amater band, reduce the level by 16dB or increase it by 18dB. You can also combine the functions of attenuator and pre-amp.
All circuits have a own control input and switched over relays.
Measurement data for all 9 amateur radio bands
Measurement data are measured with a new calibrated Agilent networkanalyzer ENA 5071B. The results are show in the curves for S11 and S21. Please look at the dB scaling and start stop frequencies in the diagramms.

All filter curves show a pass band tuning and strong filter curves at the band ends. For the most neighbour band are the suppression close to 30dB, wide band and sub harmonic suppression are better as 30dB.
1. BP filter data 160m band, selection ca. 40dB
2. BP-filter data 80m band, selection ca. 40dB
3. BP-filter: data 40m band, selection ca. 34dB
4. BP-filter: data 30m band, selection ca. 30dB
5. BP-filter: data 20m band, selection ca. 30dB
6. BP-filter: data 17m band, selection ca. 31dB
7. BP-filter: data 15m band, selection ca. 30dB
8. BP-filter: data 12m band, selection ca. 30dB
9. BP-filter: data 10m Band, selection ca. 30dB