RE: [PNW Microwave] Abridged summary of PNW-Microwave@googlegroups.com - 4 updates in 1 topic

[hamw...@gmail.com]

Hi Ray,

 

There were several different versions of the 1296 board that Jim produced.  I spoke with Jim on my board a while back when I was building mine and revised the later rev boards to have two trimmers on each input vs one fixed value and one trimmer.   Depending on which rev board you may obtain success by replacing the fixed caps with another trimmer of  around same value on the input side of the amp.   I was having the same challenge with my board, not reaching the rated RF output of 160 to 180 Watts with 10W drive .   Mike (K7MDL) and I tried various values on the input with no success.  Based on my ongoing discussion with Jim for my Rev board (Rev 7.3) from 2012,  I incorporated those changes  and after my amplifier was producing and easy 170 to 180 watts with 9 to 11 watts drive.

 

1. Remove the two fixed capacitors (believed to be 2.2pf) on the input side of the devices and replace with a 2-6PF trimmers.  So in all… each side ended up with  two 2-6pf caps I ordered from Digi key.
2. The output side where the output coax is soldered to the board was revised:  a  connection is taken from the middle of the trace…there is a break in this trace at the end which was intended to be shorted across so the output could be end-launched as an option.  If yours is bridged it is essentially adding a small capacitance at the end by including that separated piece of trace. To resolve this, remove the solder bridge and just let that piece ‘float’ by itself.  I believe this made the biggest difference in the output.
3. I also reflowed the output tabs on the transistors to ensure a good connection and solder flow.  It’s a bit challenging after the fact because they are now connected to the copper heat spreader so Flux and a very high wattage iron will do it.

 

If  you would like to talk about this off line or I can share anything else of my experience I had with mine getting it finally working, I be happy to share.

 

73,

Paul

WA9BTV

 

 

 

 

 

 

 

 

 

 

 

From: PNW-Mi...@googlegroups.com <PNW-Mi...@googlegroups.com>
Sent: Friday, April 15, 2022 7:38 AM
To: Abridged recipients <PNW-Mi...@googlegroups.com>
Subject: [PNW Microwave] Abridged summary of PNW-Mi...@googlegroups.com - 4 updates in 1 topic

 

PNW-Mi...@googlegroups.com

Google Groups

Today's topic summary
View all topics

·      W6PQL 150w? 1296 amp - 4 Updates

W6PQL 150w? 1296 amp

Ray Cannon - W7GLF <w7...@qsl.net>: Apr 14 03:38PM -0700 I thought I would pass on my so far less than spectacular results of trying to get power out of my W6PQL 150 watt 1296 amplifier.   This was owned by KD7TS although it sure looks like the prebuilt ...more

Mike Lewis <k7...@hotmail.com>: Apr 14 10:45PM Does that version have a trimmer on each input, to vround as i recall? The values of the fixed cap on the input also chaged over time. Seems like ww tested a few values trouvleshooting Pauls rf deck, ...more

Ray Cannon - W7GLF <w7...@qsl.net>: Apr 14 04:01PM -0700 Yes it has a 1-3 pF trimmer on each input. I remember when Mike bought it and I am sure he got the pre-assembled board/heatsink. I bought some from Mouser that are 2-6pF. I also bought some 2 ...more

Nick Krachmalnick <nick...@gmail.com>: Apr 14 06:01PM -0700 Hi Ray,   When I asked W6PQL about setting the bias, he responded with the below:   "Bias voltage is also 28v (same as VDD); while watching the VDD current, connect VDD to a 28v current-limited ...more

Back to top

You received this digest because you're subscribed to updates for this group. You can change your settings on the group membership page. To unsubscribe from this group and stop receiving emails from it send an email to PNW-Microwav...@googlegroups.com.

 

[hamw...@gmail.com]