Power amplifiers - Revision history

M0DHP at 17:28, 14 December 2017

2017-12-14T17:28:30Z

2017-10-15T20:45:07Z

2017-10-15T20:36:40Z

2017-10-15T20:36:05Z

2017-10-03T20:56:33Z

2017-03-28T10:48:28Z

2017-03-28T09:11:46Z

Practical designs

2017-03-28T09:10:08Z

Practical designs

2017-03-28T09:09:52Z

Multiband PGA103 amplifier

2017-03-28T09:09:07Z

Practical designs

@@ Line 1: / Line 1: @@
 The choice of power amplifiers for DATV is very critical and due to a characteristic called spectral re-growth it is vital that amplifiers are not overdriven when used on DATV.
-  The average FM or SSB amplifier MUST backed off by over 50% or 6 - 10dB by reducing the drive from the transmitter.  This means a 50 watt amplifier will only deliver a maximum 15 watts of clean DATV power!
+  The average FM or SSB amplifier MUST be backed off by over 50% or 6 - 10dB by reducing the drive from the transmitter.  This means a 50 watt amplifier will only deliver a maximum 15 watts of clean DATV power!
 [[File:146 333ks 30watts.JPG|400px]] <<<< 30 watts (ugh) ----------------         7 watts >>>>> [[File:146 333ks +10dB 7watts.JPG|400px]]

@@ Line 19: / Line 19: @@
 ===Practical designs===
-Dave G8ADM has written an article for CQ-TV which describes how to use amplifiers from DG0VE when driven by the DTX1 or Portsdown.  (The full article will be in available CQ-TV 257)
+Dave G8ADM has written an article for CQ-TV which describes how to use amplifiers from DG0VE when driven by the DTX1 or Portsdown.  (The full article is available CQ-TV 257)
   Note this article was written for the DTX1 and when used with a '''Portsdown''' you DO NOT need the additional driver stage on 146 or 437MHz and in addition  a 10 dB attenuator MUST be put between the Portsdown and final amplifier.

@@ Line 35: / Line 35: @@
   The output from the '''Portsdown''' on 437 MHz and below is too high and MUST NOT be used to drive a PGA103 as it becomes very spurious and may damage the device.
-NOTE - you MUST use a filter after the PGA103 in both applications!  Sam G4DDK described the amplifier design in CQ-TV 242 and sells kits of parts on his [http://www.g4ddk.com/Products.html].
+NOTE - you MUST use a filter after the PGA103 in both applications!  Sam G4DDK described the amplifier design in CQ-TV 242 and sells kits of parts on his [http://www.g4ddk.com/Products.html web page].
 [[File:pga103.JPG|400px]]

@@ Line 35: / Line 35: @@
   The output from the '''Portsdown''' on 437 MHz and below is too high and MUST NOT be used to drive a PGA103 as it becomes very spurious and may damage the device.
-NOTE - you MUST use a filter after the PGA103 in both applications!  Sam G4DDK described the amplifier design in CQ-TV 242 and sells kits of parts on his [http://www.g4ddk.com website].
+NOTE - you MUST use a filter after the PGA103 in both applications!  Sam G4DDK described the amplifier design in CQ-TV 242 and sells kits of parts on his [http://www.g4ddk.com/Products.html].
 [[File:pga103.JPG|400px]]

@@ Line 35: / Line 35: @@
   The output from the '''Portsdown''' on 437 MHz and below is too high and MUST NOT be used to drive a PGA103 as it becomes very spurious and may damage the device.
-NOTE - you MUST use a filter after the PGA103 in both applications!  Sam G4DDK described the design in CQ-TV 242 and sells kits of parts on his [http://www.g4ddk.com website].
+NOTE - you MUST use a filter after the PGA103 in both applications!  Sam G4DDK described the amplifier design in CQ-TV 242 and sells kits of parts on his [http://www.g4ddk.com website].
 [[File:pga103.JPG|400px]]

@@ Line 1: / Line 1: @@
 The choice of power amplifiers for DATV is very critical and due to a characteristic called spectral re-growth it is vital that amplifiers are not overdriven when used on DATV.
-  The average FM or SSB amplifier MUST backed off by over 50% or 6 - 10dB by reducing the drive from the transmitter.  This means a 50 watt amplifier will only deliver 20 watts of clean DATV power!
+  The average FM or SSB amplifier MUST backed off by over 50% or 6 - 10dB by reducing the drive from the transmitter.  This means a 50 watt amplifier will only deliver a maximum 15 watts of clean DATV power!
-[[File:146 333ks 30watts.JPG|400px]] <<<< 30 watts  ----------------         7 watts >>>>> [[File:146 333ks +10dB 7watts.JPG|400px]]
+[[File:146 333ks 30watts.JPG|400px]] <<<< 30 watts (ugh) ----------------         7 watts >>>>> [[File:146 333ks +10dB 7watts.JPG|400px]]
-For example, these pictures show a RA60H1317M Mitsubshi 60 watt brick on 146 MHz driven by a Portsdown transmitter.  The first picture is driven direct and delivering 30 watts but occupies the whole of the band - the second has a 10 dB attenuator between transmitter and amplifier and delivers 7 watts (almost 10dB down on the rated amplifier output) and needs 5 amps at 12v to achieve this!
+For example, these pictures show a RA60H1317M Mitsubshi 60 watt brick on 146 MHz driven by a Portsdown transmitter.
 ===Transmitter output levels===

@@ Line 19: / Line 19: @@
 Dave G8ADM has written an article for CQ-TV which describes how to use amplifiers from DG0VE when driven by the DTX1 or Portsdown.  (The full article will be in available CQ-TV 257)
-  Note this article was written for the DTX1 and when used with a Portsdown you DO NOT need the additional driver stage on 146 or 437MHz and in addition  a 10 dB attenuator should be put between the Portsdown and final amplifier on 437MHz .
+  Note this article was written for the DTX1 and when used with a '''Portsdown''' you DO NOT need the additional driver stage on 146 or 437MHz and in addition  a 10 dB attenuator should be put between the Portsdown and final amplifier on 437MHz .
 [[File:ADM PA.jpg|400px]]

@@ Line 31: / Line 31: @@
 * 23cms - no attenuator needed = +15dBm (40 milliwatts) (without amp = 4 dBm)
-The output from the Portsdown on 437 MHz and below is too high and MUST NOT be used to drive a PGA103 as it becomes very spurious and may damage the device.
+ The output from the '''Portsdown''' on 437 MHz and below is too high and MUST NOT be used to drive a PGA103 as it becomes very spurious and may damage the device.
 NOTE - you MUST use a filter after the PGA103 in both applications!  Sam G4DDK described the design in CQ-TV 242 and sells kits of parts on his [http://www.g4ddk.com website].