VK4BVI > 08-08-2018, 11:55 AM
VK4ADC > 08-08-2018, 01:49 PM
VK4BVI > 08-08-2018, 03:33 PM
VK4ADC > 08-08-2018, 03:49 PM
VK4BVI > 08-08-2018, 04:10 PM
VK6ZFG > 02-12-2018, 08:47 AM
VK4BVI > 13-12-2018, 04:09 PM
(02-12-2018, 08:47 AM)VK6ZFG Wrote: Hi Ron
The MRF492 is rated for a maximum output of 70W. It loses linearity if used above this power level.
I have modified DSE K6349 100W PAs that use two MRF492s from 100W to 130W output. This involved replacing the PA coil with a much heavier gauge wire and likewise the filter coil and capacitors. It also greatly improving the bias circuit which is not just a simple diode based one.
A single MRF492 will not get you a clean 100W especially if a simple diode based bias circuit is used as per the DL5DBM article.
73s
Igor
VK6ZFG > 14-12-2018, 09:41 AM
(13-12-2018, 04:09 PM)VK4BVI Wrote:Hi Ron(02-12-2018, 08:47 AM)VK6ZFG Wrote: Hi Ron
The MRF492 is rated for a maximum output of 70W. It loses linearity if used above this power level.
I have modified DSE K6349 100W PAs that use two MRF492s from 100W to 130W output. This involved replacing the PA coil with a much heavier gauge wire and likewise the filter coil and capacitors. It also greatly improving the bias circuit which is not just a simple diode based one.
A single MRF492 will not get you a clean 100W especially if a simple diode based bias circuit is used as per the DL5DBM article.
73s
Igor
Hi Igor
The transistor being used in the amplifier is now a 2SC2879. After receiving some excellent advice I discarded the MRF492.
Between natural disasters, I am wiring up the switching relays, so almost ready to go.
73
Ron
VK4BVI > 15-12-2018, 10:13 AM
(14-12-2018, 09:41 AM)VK6ZFG Wrote:Hi Igor(13-12-2018, 04:09 PM)VK4BVI Wrote:Hi Ron(02-12-2018, 08:47 AM)VK6ZFG Wrote: Hi Ron
The MRF492 is rated for a maximum output of 70W. It loses linearity if used above this power level.
I have modified DSE K6349 100W PAs that use two MRF492s from 100W to 130W output. This involved replacing the PA coil with a much heavier gauge wire and likewise the filter coil and capacitors. It also greatly improving the bias circuit which is not just a simple diode based one.
A single MRF492 will not get you a clean 100W especially if a simple diode based bias circuit is used as per the DL5DBM article.
73s
Igor
Hi Igor
The transistor being used in the amplifier is now a 2SC2879. After receiving some excellent advice I discarded the MRF492.
Between natural disasters, I am wiring up the switching relays, so almost ready to go.
73
Ron
The 2SC2879 is a better transistor but it is listed as a 2-30 MHz device so may not work too well at 50 MHz.
73s
Igor
VK5KAF > 20-02-2019, 01:29 PM
VK4BVI > 20-02-2019, 02:27 PM
(20-02-2019, 01:29 PM)VK5KAF Wrote: wonder how the amp building went i am very interested
cheers John
VK5KAF