144 Mhz home brew 600W solid state PA

[VK4DD]

Hi Gents,

My amp is sort of ready, except for some paint on the outside.
A engraved front or so would be nice. But apart from that this is it


I made a small Video to celebrate this event

Carefull it is 12MB and takes roughly 4 minutes to download if you are on a 64K ADSL.

You can download it direct from my home page (still under devellopment...)
http://www.vk4dd.com/media/600W_BLF248_2M_PA.mpg

Or you can view at at you tube...
http://au.youtube.com/watch?v=v3Cwcmhot ... annel_page

Please note that I am running the amp flat out on a dummy load.
I get 700W + out on a bird with a 1kW/125 Mhz slug, but also with a 1kW/ 500Mhz slug.
To get the 700W out you need to drive the amp with 35W.
I don't recommend this drive power for WSJT modes as the 2W 100 Ohm resistors will probably go up in smoke.
But for SSB I don't see a problem.

I estimate I have 50W more than what can be reached with a Wilkinson board.
That is probably the advantage of the 90 degrees boards.
Most of us would probably get 600W out if the amp is tuned correctly.
I did a bit more tweaking and manged to get 700W out showing what can be done, if you got good fets and patience to tune it.

Any way the amp is capable of reaching the VK limit of 400W, with a very nice clean signal.
No trace of splatter, or over driving the amp.

Just one more topic.. before I forget.
The schematics of the pic board they are updated again..
I accidently got them mixed up in the schematic, but the silk screen was ok.
So all fine now.

O yes some big improvements in the software as well. See the regular spot.

Cheers
Ron VK4DD

[VK4DD]

Hi Gents,

While many amplifiers have been build and tested...so far all passed the bench mark of 300W successfully.
So far only one amp needs more drive to get passed the 300W mark.

Tuning the amp

C6 is really an important value that needs to be spot on.
I first started with 78pF to80pF. The initial idea was to buy 10 caps of 82pF and find the lowest. That is how I got mine working.
But Glenn VK4BG noticed that some boards needed a lower value. As such the recipe for C6 is now changed.
We start off with 75pF and parrallel 2.2 or 3.3pF caps as required. If not needed we only use the 75pF cap.
Please note that these capacitors have at least 5% tolerance so your 75pF cap might be 71.2pF or 78.7pF...and anything in between.
So that is where the 2.2 and 3.3pF caps come in. Make sure you mark the 75pF in some sort of way that you know which one it is once soldered on the PCB.

If C6 is too high the amp will produce 200 to 250W. The efficiency can be quite good.
If C6 is slightly too low in value than the amp can produce 350W+ at some what reduced effiency.
Position of C6 on the PCB is also critical. So move it to see where the sweet spot is.
very small movements can have an effect on efficiency and output power.

C5 feels not as critical as C6. In the amps I have build I haven't seen much variation in output power because of a slightly different value of C5.
However the sweet spot on the PCB needs to be found, where you find an optimum in power of efficiency.
Moving it has a bigger impact than the value of it...

It is all a matter of trying the different values and different locations, in order to achieve maximum efficiency.

Now the variation in the PCB material.

I have done some measurements on the PCB and think variation in the PCB can cause low output power...
The dielectric contant of FR4 (glass fibre board) varies quite a bit.
Even in the same batch I see variation in the dielectric constant.
I can be probably of help to work out if PCB needs to be shortened ... or made longer...
Of course longer is not possible but with tricks the impedance of the tracks can be increased.
Electrically the PCB would than be longer.

Before you start building the amplifier you measure up the capacity of the tracks as shown.
Please make sure you press on zero before the leads are put on the PCB.... (this is important).

I have measured many PCB's and found that the lowest measures 21pF65.
The highest capacity PCB I have is around 24,5pF.
Most boards are just below 23 pF indicating that there is a little bit of variation in the mateial.
This could be caused by two things... first the thickness of the material, secondly the material it self (Er)

Once the components are soldered on the PCB, you can't measure up the capacity any more ....
Ideal would be if you measure up the PCB and note down this value for later reference.

Please note that this capacity gives us just an indicates the Er of the material/ thickness of the PCB.
A higher Er means that the impedance of the stripline is lower.
If you want you can download AppCAD that is a free program from Agilent technologies.
A real good tool to play with.

If you have boards with different capacities and you want to swap one for a different one, I will be happy to help you out as long as PCB's are in stock.

Ken N0GZ just reported he got 20W extra by moving C5 a little...
Tweaking an amp can be a time consuming activity and you got to have the right feeling for it as well.
I do acknowledge that this can be a difficult process. However having it done a couple of times with tube amplfiers I have develloped a certain feeling for this.
I generally look if I get more power out on a higher or lower frequency. Having small caps available and moving them around is also important to get a better feeling what is needed. On 70cm this plays an even bigger role. Because capacities are smaller and stray capacity plays a bigger role.

Please post your experiences on how to tune the amp here, or email them to me.
I will try to update this report when new info becomes available.



73 Ron VK4DD

[VK4KX]

Hi Ron, have you completed your project Amplifier yet? your signal is loud enough here already, or do I have even louder signals from you to look forward to?
Well done though, too much for me to try I can barely solder my PL259's on the coax, I will stick to increased antenna gain.

What would your ERP be adding the gain of the antenna system?
Many may ask "Why"? but why not if he wants to he can, and there is always the USA to focus his signal on, just warn me before you up the power in my direction and I will QSY to HF.

Great job.

73's

[VK4DD]

Hi VK4KAC,

I like the idea of a stronger signal, but to do that I need to move to Mt Mee or Maleny or there abouts.
So far all I have done so far is replace my 3cx800 amp for a Fet one.
Not that my tube amp made a less power or noise in the shack or that it was not reliable.... in the contrary.
My 3cx800 has been good to me ... compact, reliable, exellent cooling etc but has 3 minutes delay before it fires up and tubes need to be replaced every so often.
Please note that I have been very pleased with this amp. About 10-15 years ago I build a similar 3cx800 amp which used to work extremely good.
I sold it at the time to a friend of mine who had a much larger antenna array. Simply because he was my best friend and he wanted my amp...
I guess that is what best friends are for. Ever since I regretted the sale, because what ever I build after than was not as stable, as efficient, low weight etc as this
3cx800 amp. As such I decided a couple of years ago to rebuild my 3cx800 amp simply because I was so happy with it.

Right now I think the tubes are getting more and more replaced by these fets. Simply because the technology is getting better, lighter etc.
I just spoke to Andy VK4KY and he told me a story about a DX expedition with a HF valve amp.
They had lots of problems with the voltage stability there on an Island in the pacific. Now they have used a Fet PA with a switch mode power supply.
The switch mode supply is much more tolerant to voltage swings and the PA was lighter too...
I still like my tube amps but I think the Fet technology is getting also very mature.

Here is a picture of my 3cx800 amp (which I am not planning to sell I will think about it if some offers 3000Aud).

By the way if you live here in Brisbane area ... I think a visit to Andy VK4KY is mandatory. He has got power pole connectors, baluns, coax cable, 300 Ohm cable, 12V connectors, supply cables etc etc the list goes on and on.
Andy sells the gear with hardly any margin at rock bottom prices to promote home brew in the area.
He is also an amp builder and showed me his HF solid state AMP. 600W out with 4 x MRF150. I must say I was very impressed.
Good to see there is quite a bit of home brew going on here in QLD.

Cheers
Ron VK4DD

[VK4DD]

Hi Gents,

N0GZ had experimented with the PA but one board had difficulty producing more power> First less than 220W later tweaked to 250W finally max 270W out.
After trying different combinations of capacitors which normally fixes the problem we could not think of an other fix than to simply send Ken a new PCB and build up the amp again.
It is know that FR4 (glass fibre boards) has some variation in the dielectric constant ... as such the board could have been off spec.
So it was time to try something new... and see if we could get the power upto 300W or even above...
2 weeks later ... an email from Ken N0GZ with the title:

"Success!!!"

Here is what Ken wrote:

I built and tested the new board, and it works great, 35W in 600W+ out. It must have been the board as I just moved the same
components from the old one. I still have some work to do, adding the power/swr display and tidying up the cabinet. I'll send
pictures later. Thanks again for the support and advice.

73,
Ken N0GZ

Well I must say I was very pleased with this email
But there is more ...
Today 16 Feb 2009 I got an other interesting email from Ken...

Ron,

I have been fiddling with the amp a bit. I added two chokes on the RG-316 coax at the inputs of the amp boards. They are type 43
tubular ferrite chokes about 2 cm long and 1 cm diameter with a couple of turns through. I have seen this arrangement on a
number of commercial amps . In my case it made a noticeable improvement. Your results may vary according to the routing of the
coax and how much stray RF is coupled to its shield. On my amp it now takes ony 26W to produce 600W out. That's 13.6 dB
gain. I am very happy about this because it means my barefoot Elecraft transverter can drive the amp to full power.

Also, the 1 dB compression point seems to be at 640W out (about 30W in). Of course I will not run it this hard in regular use. I
have made these measurements using a very accurate Gigatronics digital power meter with a 40 DB calibrated high power
attenuator ahead of the power sensor, so I'm confident of the data. My Bird mater is not nearly as accurate. Also, the cooling
arrangement with two 80 mm fans works very well. I am thrilled about having the amp ready to go for the Es season which starts in
May in North America.

73,
Ken N0GZ

Woooow the good news does not stop Looks like we have got a winner, gain improves and output increases.
Making it an ideal combination with the Elecraft transverter
I have emailed Ken back and asked him if he made some measurement for before and after the ferrite on the input.

Here is his reply.

Ron,

Power gain went from 12.6 to 13.6 dB (35W vs. 26W input for 600W out) with the chokes. It is possible that the amp
might be capable of more but may be limited by the max current of my power supply (~40A).

On 2M I have two M2 2M9SSB antennas stacked vertically about 3m apart about 12M up on a rooftop minitower. Same gain (14.8 dBd) as M2"s 17
element 2M5WL but has a much wider pattern, better for contesting. I have had them for two years and have been very pleased
with the performance . I have worked both coasts of the US ~2000 m on Es using about 350W power (TE systems brick).
Here in the Midwest we also work a lot of tropo ducting and scatter in the summer months, often
out to 1000 km or more. Power is very useful for this. I also do a little meteor scatter, the extra power is helpful here as well.

My amp controller automatically adjusts the fan speed, although it is not too bad to begin with, the 120 mm fans are much quieter
than the smaller ones.

One more thing - even though getting the amp going was a challenge, it was a lot of fun and I learned a lot. Thank you again!

73,
Ken N0GZ

It is great to hear from Ken that his amp is now fully tweaked and preforming just as good or better than the others.
I am also very pleased that Ken has gone one step further and has found a way to improve the amp.
He has experimented with the input circuit and added the ferrite.
Al dough the input VSWR was not improved because it was almost 1:1 the advantage is that the Ferrite Improves the balanced to unbalanced transformation of the 1/4 coax balun. With out the ferrite one half of the BLF248 must have had less drive and as such lower power.

This is the advantage of building these amps with each other!

All in a all a great project which keeps getting better

I hope Ken can get him self registered and post some pictures on the logger.
If not than I will post them for him.

Thanks Ken for your contribution to the project.

73's Ron VK4DD

Hey isn't this what Amateur radio is all about?

[VK4DD]

Hi Gents,

Today 1 March 2009 an other mile stone 4000 hits on this topic. Thank you for reading my posts.
I also got my web site on the air, including web shop and Pay Pal links to purchase PCB's for this project.

Over time you will find that more products will come on line, as they are developed.

Here is the link to my web site
http://www.vk4dd.com

A real easy website to remember as well

73 Ron
VK4DD

[VK4DD]

Hi Gents,

N0GZ wrote me that he finished his 2m amp. It puts out 640W PEP and 600W CW with 25W drive.
Ken indicates that the output power in CW is probably limited by his power supply.

Ken also wrote that he changed the toroids on the output for FT114-43 ferrite toroids.
He had to do this because in his setup the 35 Ohm coax leads had to much radiation in PA box.
As such it started to interfere with the rest of the electronics.
Changing the to the ferrite solved this problem.

The other thing Ken added to the design is a toroid on the input.
Just some 61 ferrite and 1 or 2 windings will do the job.
With this mod you get more power with less drive power. His transverter has only 25W out as such it was an advantage for him to do so.
I recommend to do this mod.

Technical note from VK4DD

You can either tune for max output power,
or tune for max efficiency.
You can also tune for a compromise between max output power and max efficiency.
If you do WSJT on the moon, I suggest to tune for max efficiency and thus slightly less output power.

All in all a very good results and great to see the amp finished from Ken N0GZ.

I have attached just one picture here, the rest of the pictures are posted in the amp gallery.
viewtopic.php?f=11&t=8285
Keep an eye on that gallery, because more amps will be posted here from time to time.

Cheers
Ron
VK4DD

[VK4DD]

Hi Gents,

Today 22 April 2009 I finished the design for the BLF248 MARK II amplifier.
Here are some details about the BLF248 Mark II design.
The PCB is just 150 mm wide and 185 mm long.
On the input I use a 90 degrees combiner, with a new small foot print from Anaren.
I think it was yesterday that I was looking back at my own postings and saw this board again.
This design uses a single 90 x 150 mm copper heat spreader to mount two devices on.
This means that I sort of standardized on heat spreader.

It is not simply two boards on a smaller foot print, no its more. The output circuit is optimize for better efficiency.
I made the tracks about 5 mm shorter. I also integrated the input coils and a lot more little details.
It really is a big step forward and deserves the name MARK II.

It will also become a very compact building block for hi power amps.
Two of theses PCB's side by side will only measure 300mm.
2 of these PCB's will make close to 1.25 kW. This is not peanuts any more, but a serious EME grade and super tropo amp.
One single board is still very serious power with 600 to 700W out.
This is serious competition for a big Tube that's for sue.

The boards will have a new color and this time they will not be green, but blue.

On top of that I am also producing boards for a 2m amp with BLF245 (48V device).
These boards will measure 200mm long and 70mm wide. They will be good for 300W out based on the BLF245. This is a 48V device.
Like always first class quality boards will be made available factory produced, very nice.
The output circuit is based on a 9:1 transformer. It follows the design of Nanko PA0V.
This design has been proven by Nako PA0V to be effective in EME operation. The advantage is that the BLF245 is cheaper and 48V power supplies can some times be avaliabe in the surplus market. These boards will also be for sale. However the max VSWR is lower than the rugged BLF248 design.

But hey it does not stop here... I also made boards for an HF amplifier based on the BLF177.
A single board will make 300W on HF. These boards are based on a Phillips application note I found.
Currently they run up to about 40 MHz, but with some mods they will run up to 6m.
I posted this in the HF section of the Forum.
These boards will be red, factory produced, first class PCB material etc. It is the nice quality board you are used to get from me.

In total 3 new PCB's are made for more PA home brewing

So a lot of design work has been done and within 2 to 3 weeks I can show the new boards.
Please contact me direct vk4dd@iinet.net.au for these new PCB's.

I am very exited and can't wait for the boards to arrive.

73 Ron
VK4DD

[VK4DD]

Hi Gents,

Here are the latest, schematics, and material lists. (not for Mark II)
For practical reasons I started to use two capacitors instead of 1. C6 is a really good example.
I used to select one ATC out of 10 to get the right value. (quite often 78pF) after a while I noticed my ATC box was overloaded with the wrong ones.

VK4BG came up with the idea to use 22pF and 56pF. That makes 78pF.
In practice this works really well. As some caps can be a bit higher and others can be a bit lower...
For example. A 22pF ATC can be 20pF if you measure it. and a 56pF can be 58pF but even 63 pF.
As such you can have to find two caps. One from the 22pF and one from the 56pF and come close to 78pF.
But if your amplifier is happier with a little more or less capacity than that might be possible as well with other combination.
I hope it did not write it down to complicated. These notes are now in the material list included.

Other than I changed the choke to material 61. I though that lesser radiation of the pig tail is an advantage as N0GZ mentioned.
Also as an option some ferrite beats on the input coax. Also material 61.
Just something that fits nice. It is not that critical how you put it on. As long as the coax shield is not touching other things.

Here in VK4 Andy VK4KY has got heaps of ferrite in stock, Including the FT140-61 and more ...

Also worth repeating is to tune up board by board.
Do not start to parallel the amps with the combiners or Wilkinson boards until you have tuned them for max efficiency/power
or combination of these. If I was a frequent EME'er I would tune the board for max efficiency. Probably around 300W out each.

Any way after that exercise is completed you wire up the amps parallel.

An other frequent question I get is...
Where are all the resistors in the schematic?

My schematics shows the RF circuit. All the resitors and the voltage regulator circuit, decoupling etc can be copied from the data sheet from the BLF248.
To built the BLF248 board you need to download the 3D pictures. And build the Resistors and capacitors and the Bridges as per these drawings.
Care fully copy them one by one. Don't forget the install the copper "bridges:.

Do not solder the BLF248 in place before you have checked that the bias circuit works.

Go back trough the old postings, there is heaps and heaps of information to read on what you must do and don't.
It does not make sense to repeat the lot here again.

73 Ron
VK4DD

[VK4DD]

Hi Gents,

(Technical discussion, Ignore this part if you are building the BLF248 amp, you don't need to know this).

I just had a crazy idea

The idea was to use two 400W 90 degrees Anaren modules on top of each other.
Now if I am right this should half the impedance and double the power.
As such we end up with a 800W 25 Ohm Anaren 90 degrees combiner

25 Ohm is also the input impedance and the output impedance of the amp.
Of course you need to connect to the Anaren with 25 Ohm cables.

And 25 Ohm cables can be purchased or simply made by using 2 x 50 Ohm parallel.

For the dummy load, you can use 2 x 50 Ohm parralel. That is also 25 Ohm.

You could even make a 1.4kW 90 degrees if you stack 2 of these 700 watts on top of each other...
Unreal I like this idea.

The idea came up because Gerd DJ5BV was emailing me that he was going to use a 400W combiner instead of the 700W, to save a few $$.
Since he uses it on SSB only. So than I started thinking, how can I make a bigger 90 degrees combiner with small units...

Note this is all experiential. I haven't stacked these things on top of each other yet.
But I see no reason why it should not work. It think it will give the 90 degrees phase shift...
Who has done this before?

Cheers
Ron
VK4DD

[VK4DD]

Hi Gents,

Solid state is no longer for small amps. It is possible to make a solid state much more power full than a GS35B, an 8877 etc.
This idea is based on using 90 degrees combiners. 90 degrees combiners are really called Quadrature Combiners. In fact it is an other name for the same thing.
If you look in the block diagram, you see for instance QC800/25. That is made out of 2 400W/50 Ohm quadrature combiners on top of each other.
That doubles the power, and reduces the impedance to 25 Ohm. The QC1400/25 is made from 2 Anaren 700W/50 Ohm.

Have a look at the block diagram and see how 8 x BLF248 makes a bit of power...

The end result is 2600 Watts solid state power on 2m. This is serious power .
Would love to play with one, but I must admit have no aspiration to build this thing.
Just the BLF248 would cost you 8 x U$150 = US$ 1200.
But it sure is a nice toy to play with....
No need to mention that you can't use a normal N-connector any more.
At this power level the center pin just melts ....

In the sketch below, I am using 4 x Mark II BLF248 boards
The RF deck measures only 300 mm wide, if you use 2 boards above 2 boards.
With the heat sinks facing each other.
I would suggest to use a centrifugal blower for the air flow.

The power supply would be 4 x 1kW switchers. or 2 x 2.5kW switchers.
Both are commercially available.

The Wilkinson combiner is no longer a PCB. This should now be made from brass discs and 3mm telfon.
A few screws etc. Big 6mm tubes to make the output coils.
I think this is pretty serious stuff.

Cheers
Ron VK4DD

[VK4DD]

Hi Gents,

The new Mark II boards have arrived.
There is only one word I can think of.

AWESOME
The blue looks so good on these boards. They have come out even better than I could have hoped for.
As usual.. super quality boards....
that why this word keeps coming up in my mind...

I am sorry I am so exited. I love it when the finished product looks real nice.

Ok here are some notes on how to use these MARKII boards.
You can use them like the old boards. Same matching and combining techniques are applicable.
That means you don't have to use the 90 degrees Anaren on the input or the output.
But you can use the 90 degrees Anaren if you want to.
For the output Anaren, I supply two small PCB's which enclose the 700W Anaren 90 degrees combiner.
When you decide to use the 90 degrees Anaren boards you also need to use one for the input.
Other wise the signals would be out of phase when you combine them.

You can still use the Wilkinson board, or make your own with 2 pieces 75 Ohm coax.

I will list the boards including the small boards for US$ 65 on my web site.

Solid state amplifiers have never looked so good.

Ron
VK4DD

[VK2LSB]

Post deleted

[VK4DD]

Please send via Email.

I have offered Stuart to check his board and ship it up to me before he solders the BLF248 in place.
I just want to make sure, he gets his amp up and running, and will offer him the help and support to get that job done.
In this case that is easy because he is only 800km away

Regards,
Ron.

[VK2LSB]

Post deleted

[VK4DD]

Hi Gents,

In the Mark II PCB I use 2 Anaren 90 degrees combiners.
The small one is the Anaren 1H0280-3
and the big one is the Anaren 1Z0280-3
These are sold by Richardson Electronics and Avnet.
Both distributors can be found on the Anaren site.

Unfortenately there was no stock for the little Anaren 1H0280-3, but I have ordered some and I expect to receive some in 12 weeks .
Bugger that is early September... The big ones are in stock, so no drama's there....
I would recommend to just keep going and start making the metal work for your amp, find a suitable power supply etc.

Power supplies:

I have settled for the Meanwell switched mode power supplies. I think a 1000W or a 1500W would be good for one Mark II board.
The Meanwell switched modes have good MTBF (Mean Time Between Failure) and these power supplies have done a burn in test at the factory.
This reduces the early drop out to only 5 untis per 1000.

Testing MARK II and component list....
I will test the mark II board without an 90 degrees Anaren, which is fine, because it is 50 Ohm in and out. The technology is proven for me.
That is because the little Anaren is not in stock. So what I will do is cut Mark II in half and build and test a single BLF248 Mark II amplifier.

I think I need 3 weeks or so to get this job done, and expect to start in 1 week.
This will only have an impact on the ATC capacitors not the other components.

As far as lay out... it is the same lay out as the Mark I (the green boards).

Here is a quick start if you are going to build a BLF248 amplifier..
Follow this link.

viewtopic.php?f=11&t=8100&start=38

73 Ron
VK4DD

[VK5APN]

More Copper???

I have had an enquiry for some more copper plates for Ron's VK4DD amps.

Not many suppliers stock 6mm copper plate. The supply said that his was imported from South Africa??

The copper comes in a bar that is 6 inches (152.4mm) wide and 1/4 inches (6.35mm) thick. This was ideal for the first generation 300w BLF248 PCB's. They were cut at a length of 92mm, allowing 1mm sticking out around the PCB, left like that or for machining. The cutting cost is about $2.00 for individual plates but once cutting machine has been set up they become cheaper the more that gets cut.

They have limited supply of the bar. So maybe your last chance to obtain such thick copper.

They have quoted me on 92mm length (1st gen amps (90x150mm PCB)) and 182mm (2nd gen amps (150x180mm PCB)) plates. The prices have remained the same as last time, even though I tried to persuade them on the copper prices etc. His response was, do you want it because it is hard to find it otherwise.

So those who would like some copper plate/s and more info eg pricing, for their amps let me know. Email info under Op Info.

If the size you want is not any of the sizes already mentioned then let me know. If there are a number that would like the same size copper than that would be beneficial as the cost will become cheaper.

See page 6 of this forum thread for pictures of the previous batch.

Regards and looking forward to any responses.

Wayne VK5APN

[VK5APN]

Copper Update

All

Just spoke to the Supplier as someone requested a size of 120mm (152.4 x 120 x 6.35mm). Usefull for the HF Amps.

The copper cost is calculated on weight + Cutting cost + GST. They also informed me that there is only meters left.

The good news, if you go for 10 or more the prices become better.

The next good news is that they will do a final weight costing. That is if only one person orders a particular size the cost will not be the single unit cost. The cost will be calculated on the total weight of the copper of all the other orders put together.

This makes it hard to work out what the final price would be until I have all the orders in. As well as the freight. Post and Package last time (92mm size) was $15.00 for 2 plates and $14.00 for a single plate within Australia. So if the postage rate has not increased I estimate that the postage would be similar.

Where does this lead to?????

I will need all the orders in to get a price per individual requests. Then for the larger size I will need to get a quote on postage.

I am not making anything out of this. I am charging what it will cost me. True Ham spirit. This to you is a HUGE saving (buying in bulk as well as freight) as apposed to organising the copper yourselves individually.

This means that once the orders are in, I will have to purchase and tally individual orders along with the freight. Hoping that all that asked for copper will pay for it. This was not the case last time and was I left with unwanted copper.

Time frame to receive orders?? Perhaps I should wait 2-3 weeks for the orders to be placed and before getting the copper. If you need time to arrange the money, I can understand that. Just let me know if you would like copper to be included in the bulk purchase. This is probably the last time that I'll do this? So do not miss the boat!!

My email address is in the OP INFO which should be vk5apn@aapt.net.au I have had trouble in the past with this account. If you get a bounced email then send it to a newly setup email vk5apn@gmail.com I would prefer the aapt account be used first as I usually check it twice daily. The other one not so regularly.

Recap. I can obtain copper plates that are 152.4mm x 6.35mm thick. These dimensions are fixed it is only the width that is variable. Let me know what you require.

So far 92mm is for the first generation 2m 300w boards (PCB size 150 x 90mm),
120mm is for the HF Amps (PCB size 115 x 135mm)
and 180mm is for the second generation 2m 300w boards (PCB size 150 x 180mm)

But I am not fixed at these sizes.

Hope that is clear. If not email me.

Regards

Wayne VK5APN

[VK4DD]

Hi Gents,

5000 hits, new VK4DD forum, and MKII tested (half the amp).....

This forum has now gone past the 5000 hits but there is more....
I have also started up my own forum on my site which has a less restrictions for users outside VK.
It allows me to document the amplifier project better.
For hams outside VK it is easier to post here. This forum is just for Amplifiers, Antennas. Only the real RF stuff.

http://www.vk4dd.com/forum/viewtopic.php?f=4&t=10

But .... there is more good news...
I have tested half a BLF248 MKII PCB and got upto 400W out on SSB.
That is just with the computer modeled capacitors, no optimization done what so ever.
the 400W came only out because I drove the amp with 20W+. Probably not ideal.. because if you drive the amplifier to hard these things do happen.
Any way it is a good sign that the amp does this, so I am real pleased.
I will do some more tweaking to see if this is the optimum.

But I am real pleased to see that the computer model is as good as the real amplifier...

Have a look at this video on you tube.

http://www.youtube.com/watch?v=tz0RQ8d8 ... annel_page

73 Ron
VK4DD

[VK4DD]

Hi All,

Here is the schematic for the MKII board including the Anaren combiners and the values for the ATC capacitors.
I suggest that you get the 78pf and the 8.2pF capacitor from me. This one is crucial for max power out.
The other capacitors can work with the normal 5% tolerance ATC caps generally have.

The amplifier is now tuned. My amplifier has now more than 70% efficiency at 400W CW out.
SSB the amp was willing to give me up to 450W out. This is way more than the specs.
So you have to make sure you don't drive it this hard, as this data is exceeding the specifications.
So just drive it less.

The amplifier is happy and seems to work with very high efficiency. I am more than pleased with this result, realizing that this is only the first one built.

You will need to tune each BLF248 amp, before you start combining them with the Anaren combiners on the PCB.

73 Ron
VK4DD