1296 MHz amplifier build project

[Fred W]

Hello All.

Here's my shot on what we're up to.

A couple of the key goals of the group was, to build our own equipment and learn more about the workings of microwave operation. (In my opinion it has more than succeeded. I would also like to add that this has been the most fun and enjoyable time I have had in Ham radio).

Now to the point, for 2021 we decided that we needed a new project and building an amplifier sounded very intriguing. In keeping with our previous project of a 1296 MHz transverter we decided on building a reasonable sized amplifier for 1296 MHz.

This looked to be very promising as there is quite a bit of information available and the pricing of components is reasonable for microwave bands.

So we are now in the process of moving forward and anyone who would like to join us is more than welcome.

We are loosely following the W6PQL style 150 watt solid state amplifier and  are now starting to acquire our parts and pieces.

(https://www.w6pql.com/150w_23cm_turn-key_amplifier.htm)

The three items we are getting ready for our February meeting will be PCBs, XRF286 mosfets (2 are required) and the copper heat spreader.

Our plan is to produce our own PCBs and if all goes well we will create these at the next meeting. I was told that PCBs are still available for purchase from W6PQL if one wants to go that route.

XRF286 mosfets are available online from several different suppliers, about $16 ea shipped from china.

I have found a supplier for the 1/4" x 4" x 6" copper heat spreader. Pricing is better for a small quantity than for one, due to shipping and handling cost. I will be ordering several this week, so let me know if you would like one and I'll add it to the order. About $33 ea.

That's the status for the group, we look forward to hearing from you via Email ,Zoom or in person.

Fred - N7FW

[Mike Lewis]

Here are some pics of the 1296 60W amp I built a few months ago.  Uses PQL Amp control board and FET switches.  I used a coupler and ADL5519 dual detector for forward and reflected power monitoring.  I embedded my RF wattmeter into the chassis with a small OLED display to show power, calculate SWR, output 0-4V in proportion to SWR for the Hi SWR shutdown input, and measure 12V, 28V and temperature.  It can be connected by USB to calibrate and remote monitor if desired.    

 

Paul, WA9BTV built a XRF286 150W amp, it is now putting out 150W at 10W drive.  He is using a 3.5” touchscreen for his embedded wattmeter with the dual detector.

 

Also in my attached pic is a XRF286 150W PQL based amp that WA7TZY built into a rack chassis.  It has a separate metered power supply with toroidal transformer.  5V, 12V and dual 28V output.  The small boxes in chassis are relays mostly but also a 18W booster map (Mitsubishi module, drive level set to max of 10W) and a homebuilt interdigital filter in front of the low NF LNA.  It won’t be bothered by high power from other nearby antennas.  Same for all his other amps.

 

Both of these have oversized heat sinks to permit upgrading to higher power RF pallets later.  I am looking at the upping the 60W to a 600W pallet but run it at 28V for lower power and high failure immunity chances.

 

Fred bolted his XRF286 chips in place.  W6PQL solders his.  I suspect you could arrange to ship Jim a batch of heat sinks and chips and have him solder them if you wanted.  Paul did his own (more than once), I think he would send it to Jim next time 😊.

 

 

Mike

K7MDL  EL87sm & CN88sf

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[Fred W]

So right now we are just working on getting the RF deck going (I think that's what it is referred by).

For the PCB we plan on building those ourselves, using the UV exposure method and chemically etching the boards at Franks.

The copper is just bare, so drilling and tapping will be required for PCB mounting, heatsink attaching and securing to your enclosure. We don't believe any milling is required and we plan to solder the RF286's to the copper.

If anyone is outside the local PNW area, it may be more economical for you to order the copper directly. Basically the raw copper is $33 with $10 shipping. Adding more pieces will only add $ for weight. This is a USA provider.

This amp should be capable of 100 watts plus. A 28vdc power source will be needed and we are currently looking at options.This is a stepping stone to bigger and better things, we understand that there will be challenges this is partially why we chose this route. Better to let the smoke out of a $15 device than a $250 one. :-)

The amp can be driven by about 3 to 4 watts up to 10 watts for max output.

Some of the commercial radios will easily drive that, but for lower power transverters we realized that it may take something more to drive the amp. Frank is currently working on that and we plan on having a solution. Probably another part of the build.

The complete design and final stages are still a work in progress. A big reason why I am blogging here is to drive interest and participation. Please join us. This is your opportunity to have some input and a lot of fun.

Mike I really like your display and would enjoy incorporating that into our build! Those graphical color displays really dress projects up. Not to mention the data they can display.

Please remember, these challenges and comradery are why we do this!

Fred - n7fw

Copper requests:

Frank - 2

Rod - 1

Bill - 2

Pablo - 1

 

Payment will be due when you receive your copper.

On Tue, Jan 26, 2021 at 1:51 PM Pablo Sala <pabl...@gmail.com> wrote:

Hi Fred,

Please, include me in the order for the heat spreader. Let me know if you want me to send you the money via PayPal.

Is Frank going to make the PCBs with his CNC machine?

Also, what's the group's plan to get to the 8-10W needed to drive this PA from the low-power output of our W1GHZ transverters?

Thanks,

Pablo

Sent from my iPhone

On Jan 26, 2021, at 10:35 AM, Fred W <fredm...@gmail.com> wrote:



[Nick Krachmalnick]

Hi Fred,

Count me in on the copper spreaders 1 each (will cover 2 XRF286's I assume. If not 2 each).

I like the clean layout of Mikes equipment. Very nice.

73's

Nick

To view this discussion on the web visit https://groups.google.com/d/msgid/PNW-Microwave/CANC-Whz3ZgbKqGUH3_SysjebOwUQU-5C78TqwU%3DvkYAPSeOZHA%40mail.gmail.com.

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Nick
nick...@gmail.com

[Mike Lewis]

On the PQL design he recommend milling a channel to lower the XRF286 tabs to the level of the PCB.  He says that misalignments and gaps cause loss of power. Fred (WA7TZY) bolted his in on smaller size blocks (see the pic in previous email) and raised the boards with aluminum flat stock to get the perfect lift.   Paul had ½” thick copper blocks milled with a channel to that holds both boards, no spacers required except for the terminating resistors.

 

Mike

K7MDL  EL87sm & CN88sf

 

From: pnw-mi...@googlegroups.com <pnw-mi...@googlegroups.com> On Behalf Of Fred W

To view this discussion on the web visit https://groups.google.com/d/msgid/PNW-Microwave/CANC-Whz3ZgbKqGUH3_SysjebOwUQU-5C78TqwU%3DvkYAPSeOZHA%40mail.gmail.com.

[Fred W]

Looking at Jim's website can be confusing, he shows several different projects while describing another.

The PCB material we are using will be cut into 2 pieces, placed on the heat spreader on both sides of the XRF286's

We believe that the thickness of the PCB will provide the correct height needed to mate up to the devices we have.

If a channel is required we have some ideas for that.

If you purchase the XRF286's that have ears on each side screwing them down is an option.

For now we believe that this size heat spreader is adequate. We plan on adding a heatsink and there's always the option of doubling the heat spreader or adding a fan.

And because this is DIY you can tailor it to suit your own ideas.

Fred - n7fw

[jabeco]

This thread peaked my interest. 

Here is my dual xrf-286 PQL. 

It is biased and sequenced by shutting the 28v PS off/on (PS noisy on rx).

GL on the builds, mine drives to 100w with 3.5w in. 

73, .-James K7KQA DN06

Sent from my T-Mobile 4G LTE Device

[Fred W]

Hello everyone

I will probably place an order for the copper tomorrow, here's a list of who has requests in.

Copper requests:

Frank AG6QV - 2

Rod WE7X - 1

Bill  N6NM - 2

Pablo KI7OJL - 1

Nick N0CYT - 1

Scott VE7FYC - would you like 1?

Fred n7fw - 2

Please let me know if changes or additions are needed.

As a side note, I am receiving some emails directly and I do not mind. But please, if it pertains to anything microwave think about sending it to the group. I enjoy everything that comes across the reflector and I'm sure many others do also.

I do appreciate every response received and especially the ones right now that pertain to our build, thank you.

For me the more I get to know you and your call sign the better. I have lots to learn and there is a wealth of people with great knowledge and experience out there.

The reflector is a subgroup of PNW VHF society so we aren't bothering anyone that hasn't subscribed to the group.

Fred - n7fw

On Wed, Jan 27, 2021 at 8:13 PM Scott CHARLES <ve7...@gmail.com> wrote:

Hello Fred.

I would like to join in the build group.

Please let me know what you need from me?

Thank you. 

Scott CHARLES, VE7FYC 

[Nick Krachmalnick]

Hi Fred,

Please change the number of heat sinks from 1 to 2 for me when you have a moment.

Thanks very much,

Nick

N0CYT

To view this discussion on the web visit https://groups.google.com/d/msgid/PNW-Microwave/CANC-Whwbx3qrHpSk_4de2GHDk1RKd2_PpbdzKcTJ3FX6Nd%2BMpg%40mail.gmail.com.

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Nick
nick...@gmail.com

[Pablo Sala]

Hi Fred,

So, how many copper spreaders are actually needed for an amplifier? One or two?

I see most people ordering two. Why is that? Please, clarify.

And if two are indeed needed for a single amplifier, then please change my order from one to two.

Thanks,

Pablo, KI7OJL

To view this discussion on the web visit https://groups.google.com/d/msgid/PNW-Microwave/CAJLZ--XE0oKj4FJhA9rJsU%3DKtu0Qhc2%2BPQ0DHz6dtVobUMnwKA%40mail.gmail.com.

[Nick Krachmalnick]

Hi Pablo,

I believe, Fred please correct this if I am not right, that one 4" x 6" spreader will cover two XFR286's.

So instead of ~150 watts with two XRF286's, a second set of XRF286's can by added for a ~ 300Watt amplifier. The additional components (splitters & combiners, second heat sink & 2 more XRF286's and suitably sized wire & a bigger/2nd aluminum heat sink to get rid of the heat from the spreaders & a suitable power supply to power this setup would be needed).

73's

Nick

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Nick
nick...@gmail.com

[Ray Cannon - W7GLF]

I have decided to forgo this project since I already have two 60 watt amplifiers and a 150 watt amplifier for 1296.  Seems kinda silly to build yet another one but I will be available for moral support.

[Pablo Sala]

Thanks for the clarification, Nick.

In that case, I will keep my order to a single copper spreader (sufficient for two XRF286).

Thank you, Fred, for taking care of this,

Pablo, KI7OJL

[Nick]

Hello Fred and group.

I would like to join in on the build. As the drive to meeting is prohibitively long, especially the return, and took 5 hours to get home, I will have to stay home. As such would you list the copper spreader source so I can order 2 for my self and have it shipped to my door rather to group for distribution at the meeting.  As to the boards, I can either have the group mail them to me or as noted I can get a couple from W6PQL, whom I have been a customer for years.

I am also interested in the low power option Fred is working on, as I have a few transverters that have the lower output. Another RF relay and one could have a dual input option of high and low drive.

 

I have Zoom but didn’t see a invitation for last meeting. I know it is a hassle and limited, but even 15 minutes when a discussion on parts purchases would be welcome.

 

Thanks,

Nick……WB7PEK

 

 

 

 

From: Fred W
Sent: Tuesday, January 26, 2021 3:35 PM
To: Pablo Sala; PNW Microwave
Cc: John Petrich; WA7EE Mariana
Subject: Re: [PNW Microwave] 1296 MHz amplifier build project

 

So right now we are just working on getting the RF deck going (I think that's what it is referred by).

To view this discussion on the web visit https://groups.google.com/d/msgid/PNW-Microwave/CANC-Whz3ZgbKqGUH3_SysjebOwUQU-5C78TqwU%3DvkYAPSeOZHA%40mail.gmail.com.

 

[AG6QV - Frank]

I was reading through W6PQL's page on the XRF-286 amplifiers and it looks like he is using Rogers 4003c boards for the amp and not standard FR4 boards.

I have located a place to purchase these at $15.54 per board. There is a minimum order limit of $36 and for 3 boards they charge $36.90 in shipping. They are located in Italy!

https://www.rf-microwave.com/en/rogers-corp/ro4003c-0200-1e-1e/double-side-laminate-with-polyester-ceramic/ro4003-20-1-152x114/

I have contacted Rogers in AZ but not heard back. It would be nice to have a local source.

- Frank

-- 
73 de Frank
CN87tl

[Mike Lewis]

FYI, Jim quoted me $45 plus $9 postage for one of the few 150W boards he has left in stock.

 

Mike

K7MDL  EL87sm & CN88sf

 

From: pnw-mi...@googlegroups.com <pnw-mi...@googlegroups.com> On Behalf Of AG6QV - Frank
Sent: Saturday, January 30, 2021 21:24
To: PNW Microwave <PNW-Mi...@googlegroups.com>

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[VE7HR]

Frank,

I may be able to get some made at my board supplier. 

Do you have the gerbers?

If you tell how many you want I can make an inquiry. 

Dave

VE7HR 

Sent from my iPhone

On Jan 30, 2021, at 6:36 PM, Mike Lewis <k7...@hotmail.com> wrote:



To view this discussion on the web visit https://groups.google.com/d/msgid/PNW-Microwave/CO6PR18MB3858F64FC3C221BC075987DFF6B79%40CO6PR18MB3858.namprd18.prod.outlook.com.

[Frank M. Kromann]

Hi Dave,

I only have artwork in the form of pdf files and we were thinking to add photo resist to the boards, expose to UV light followed by developing and etching. That's how I used to make PCBs in the 80s and 90s :-)

The artwork files can be downloaded from here

For other project or if this does not work out it could be interesting to find a good PCB manufacturer that does provide Teflon boards.

- Frank

--
73 de AG6QV
CN87tl

[litni...@gmail.com]

Please count me in on the amplifier project. Will have devices by April?! but will definitely want a spreader and PC's

Thanks so much for your effort!!!!!