Difference between revisions of "8-Band RF Output Switch"

From BATC Wiki
Jump to navigation Jump to search
Line 1: Line 1:
For those of you who want to drive Microwave transverters from your Portsdown or need a higher drive level, the team have developed an 8-Band RF output switch that includes an RF amplifier. It is designed to be used with the Output Attenuator (see below). It will be capable of amplifying the variable level from the attenuator providing up to 10 dBm and switching it to separate amplifiers for the 70, 144, 437 and 1255 MHz bands, and to 4 transverters for the higher bands. PCBs are on order and will be available from the BATC Shop.
+
For those of you who want to drive Microwave transverters from your Portsdown or need a higher drive level, the team have developed an 8-Band RF output switch that includes an RF amplifier. It is designed to be used with the Output Attenuator (see below). It will be capable of amplifying the variable level from the attenuator providing up to 10 dBm and switching it to separate amplifiers for the 70, 144, 437 and 1255 MHz bands, and to 4 transverters for the higher bands. PCBs are available from the BATC Shop.
  
 
[[File:8-Band RF Switch Built V1 small.jpg|576px]]
 
[[File:8-Band RF Switch Built V1 small.jpg|576px]]
  
Here is the draft (not yet validated) schematic: [[:File:8 BAND RF SWITCH V1-0 SCH.pdf]]
+
The initial design was as shown above - the first batch of boards will be supplied in this form.  The initial (V1.0) circuit is here: [[Media:8 BAND RF SWITCH V1-0 SCH.pdf]].  The first board layout is here: [[Media:8 BAND RF SWITCH V1-0 SS.pdf]].
  
Here is the board layout: [[:File:8 BAND RF SWITCH V1-0 SS.pdf]]
+
The original parts list, which has not yet been updated, and has only been checked against the DigiKey Part Numbers, is here: [[:File:8 BAND RF SWITCH V1-0 PARTS.xls]]
  
The parts list, which is currently provisional, and only checked against the DigiKey Part Numbers, is here: [[:File:8 BAND RF SWITCH V1-0 PARTS.xls]]
+
HOWEVER, the circuit needed some simple rework to provide a more stable power supply for the SKY MMIC and to equalise the levels across the bands.  The modifications are to:
 +
 
 +
# Cut the track on the underside between the output of the voltage regulator and the link point marked 5VA.
 +
# Replace the 7805 with a 7808 regulator (for 8 volts) and wire a 30 ohm resistor between the regulator output and the the point marked 5VB.  Note that the resistor will need to dissipate 300mW (it passes 100mA), so 3 1/8 watt 10 ohm resistors in series might be easiest.
 +
# Wire a 78L05 regulator with its input from the 12V supply and its output to the point marked 5VA.
 +
# The input attenuator should be set up with R1=R2=68 ohms, and R3=220 ohms.  If you need 10 dBm output on 1255 MHz, this can be achieved by adding a series combination of 68 ohms and 2.7 pf across R3
 +
 
 +
The modified board is shown below.
 +
 
 +
[[File:8-Way RF Prototype Small.jpg|556px]]
 +
 
 +
The new circuit (will be published as soon as the design is validated.

Revision as of 22:35, 24 March 2018

For those of you who want to drive Microwave transverters from your Portsdown or need a higher drive level, the team have developed an 8-Band RF output switch that includes an RF amplifier. It is designed to be used with the Output Attenuator (see below). It will be capable of amplifying the variable level from the attenuator providing up to 10 dBm and switching it to separate amplifiers for the 70, 144, 437 and 1255 MHz bands, and to 4 transverters for the higher bands. PCBs are available from the BATC Shop.

8-Band RF Switch Built V1 small.jpg

The initial design was as shown above - the first batch of boards will be supplied in this form. The initial (V1.0) circuit is here: Media:8 BAND RF SWITCH V1-0 SCH.pdf. The first board layout is here: Media:8 BAND RF SWITCH V1-0 SS.pdf.

The original parts list, which has not yet been updated, and has only been checked against the DigiKey Part Numbers, is here: File:8 BAND RF SWITCH V1-0 PARTS.xls

HOWEVER, the circuit needed some simple rework to provide a more stable power supply for the SKY MMIC and to equalise the levels across the bands. The modifications are to:

  1. Cut the track on the underside between the output of the voltage regulator and the link point marked 5VA.
  2. Replace the 7805 with a 7808 regulator (for 8 volts) and wire a 30 ohm resistor between the regulator output and the the point marked 5VB. Note that the resistor will need to dissipate 300mW (it passes 100mA), so 3 1/8 watt 10 ohm resistors in series might be easiest.
  3. Wire a 78L05 regulator with its input from the 12V supply and its output to the point marked 5VA.
  4. The input attenuator should be set up with R1=R2=68 ohms, and R3=220 ohms. If you need 10 dBm output on 1255 MHz, this can be achieved by adding a series combination of 68 ohms and 2.7 pf across R3

The modified board is shown below.

8-Way RF Prototype Small.jpg

The new circuit (will be published as soon as the design is validated.