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     Northam, Western Australia
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RECEIVE CONVERTER FOR 630M BAND

630m band (472kHz-479kHz) Receive Converter. Under development


HOME  > PROJECT > 630M TRANSVERTER >

The receive converter consists of tree main elements, Low Pass Filter to mitigate strong AM broadcast band transmission over loading the receiver, a single transistor amplifier and Ring Mixer to step the 630m band (472kHz-479kHz) signals up to the 30m band frequency range of 10.472MHz-10.479MHz. While 472kHz-479kHz is the range of interest for this project the receiver converter is well capable good reception well below these frequencies.  

 

Fig 1 Schematic of the receive converter. This circuit is subject to further development.

 

Component details

 

TUF-1+

Frequency Mixers Module

Q1

Transistor - 2N3904 or 2SC2671 TO-92

Q2

Transistor - 2N3904 or 2SC2671 TO-92

R1

Resistor 1k 0.25W Carbon

R2

Resistor 1k 0.25W Carbon

R3

Resistor 100R  0.25W Carbon

R4

Resistor 470R  0.25W Carbon

R5

Resistor 10k  0.25W Carbon

R6

Resistor 680R  0.25W Carbon

C1

Capacitor - Ceramic - 220nf

C2

Capacitor - Ceramic - 15nf

C3

Capacitor - Ceramic - 20nf

C4

Capacitor - Ceramic - 20nf

C5

Capacitor - Ceramic - 15nf

C6

Capacitor - Ceramic - 100nf

C7

Capacitor - Ceramic - 22nf

C8

Capacitor - Ceramic - 50pf

C9

Capacitor - Ceramic - 22nf

L1

14.7uH = 10uH + 4.7uH Epoxy Dipped RF Radial Choke

L2

22uH Epoxy Dipped RF Radial Choke

L3

14.7uH = 10uH + 4.7uH Epoxy Dipped RF Radial Choke

 

 

Photo 1 Assembled receive converter.

 

Photo 1 Assembled receive converter.

 

Low Pass Filter 

 

With the 630 metre band being so close to the AM broadcast band it necessary to provide a low pass filter to attenuate potentially strong signals that may desensitise the receiver. AADE Filter Design 4.5 was used to design and analyse the receiver's low pass filter stage. 

Fig 2 AADE Filter Design 4.5 attenuation analysis of the receiver low pass filter circuit.

 Fig 2 AADE Filter Design 4.5 attenuation analysis of the receiver low pass filter circuit. 

 

The real world filter circuit assembly was testing and exhibited an attenuation curve approximately 25kHz higher in frequency as compared to the model. See Fig 3. The higher cut off frequency of the low pass filter was surprisingly high as the AADE Filter Design 4.5 application had generally provided fairly accurate modelling of similar filters, however the resulting low pass filter performance is sufficient for the proposed receive converter. The variation in modelling when compared with the physical circuit performance may be a result of the use of the cheaper Epoxy Dipped RF Radial Chokes.

 

Fig 3 Low Pass Filter attenuation measurements graphed with excel. 

Fig 3 Low Pass Filter attenuation measurements graphed with excel. 

 

  

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Page last revised 13 November, 2024

 

 

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VK6YSF Experimenting with JS8Call on the 6m Band

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VK6MJM is a  LF/MF station located in Manjimup, Western Australia.

Mode: Mode: FST4W 300 (Similar to WSPR)

Station details were presented by Peter Hall (VK6HP) at PerthTech 2024.Presentation PDF: Peter Hall VK6HP at PerthTech

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