JUMA PA1000 Linear Amplifier

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Re: JUMA PA1000 Linear Amplifier

Postby G4ZOW » 16 Jan 2012 10:01

Matti,

Nice project, congratulations on all your work to date.

I'm on your side and prefer single board designs wherever possible minimising wires excessive wiring around the place :lol:

Just my 2c, and I'm no designer - but I collect amplifiers, especially QRO HF mobile's.

I work with a company who design and manufacture continuous duty RF amplifiers and transmitters for the radio broadcast industry.

We currently use these Murata SMPS which meet all EU directives: http://www.murata-ps.com/cgi-bin/cd4pow ... talog/1001

You want to also look at Delta, similar quality at half the cost!

As an even cheaper alternative you may wish to have a word with Christi, a Rumainian SMPS designer based in China :mrgreen: he can configure one of his standard models to fit. his 2kW unit is somewhat bare but at $177.00 USD is on the money don't you think:

Click on the image top right: http://connexelectronic.com/product_inf ... cts_id/120 He can fit it in a case just like the Murata's.

David G4ZOW
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Re: JUMA PA1000 Linear Amplifier

Postby OH7SV » 16 Jan 2012 11:04

David,

Thanks for good comments.
I have noticed the Murata SMPS. They look good but are too big (long) in size to integrate in the enclosure.
Christi's resonant looks attractive. I might contact him for a custom model.

73 Matti OH7SV
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Re: JUMA PA1000 Linear Amplifier

Postby N7LOH » 17 Jan 2012 15:08

Wow,I love this discussion and the little I understand of it shows me just how much work goes into the devices of our hobby.So I will watch,read and hopefully learn.I am looking forward to buying your 1 kw amp whenever it becomes available.Cool stuff for sure.73,
-george
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Re: JUMA PA1000 Linear Amplifier

Postby vk4dd » 20 Jan 2012 04:48

These kind of clean symmetrical signals need a proper phase reversing transformer from drain to drain to maintain a good voltage swing in drains. A MOSFET drain or a BJT collector can only pull, they are not capable to push. Actually push-pull BJT transistors or MOSFETs do not exist


Tnx for showing the importance of having a phase reversing supply transformer. I assume not having one could result in saturating the ferrite. Assuming that is where this distortion comes from.

I like to experiment and work on PA's. It is not so much the destination but more the journey of experimenting what I like. It is great when it all works but than you need to find an other project.

Have a good journey.

73 Ron.
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Re: JUMA PA1000 Linear Amplifier

Postby 4z1ao » 28 Feb 2012 08:12

Haven't seen any news for more than a month. I am very interested in the amp. Any news about the schedule for its appearance and the price? What is the status of the project?

73 Isaac 4Z1AO
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Re: JUMA PA1000 Linear Amplifier

Postby LB3HC » 18 Mar 2012 18:37

SP5G is experimenting with a HF PA design based on two MRFE6VP61K25H. It looks like he parallels the two FETs in each MRFE6VP61K25H device and uses two MRFE6VP61K25H devices to achieve pull pull (or should we say "push pull"?). What I wonder about is what kind of transformer configuration is used on the output of the SP5G design? This is a somewhat good picture: http://sp5g.net/wp-content/uploads/2011 ... 204003.jpg It looks like SP5G uses ferrite cores with coax wound on them but I am not sure about the impedance transformation ratio. The output impedance would be very low with paralelled FETS I would assume. Do you agree? Here is his webpage with some info http://sp5g.net/?p=1772

I also wonder what output transformer is used on the Juma 1000 design? Is it a Ruhtroff or Guanella type output?
What cores are used?
What is the max frequency that the Juma 1000 prototype will operate on?

73
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JUMA PA1000 weight reduced from 14 kg to 5 kg

Postby OH7SV » 24 Mar 2012 17:39

Here are the original heavy weight mains transformers.
juma-pa1000-mains-transformers.jpg
JUMA PA1000 original mains transformers 10 kg

This is the prototype with the light weight resonance switching power supply.
The power supply weights only 0.8kg. Note also the handle on the right side.
juma-pa1000-SMPS.jpg
JUMA PA1000 resonance power supply 0.8kg

The first tests have been done and everything is looking good.
The total weight of the amplifier is now only 5 kg :D
The spurious generated by the SMPS seems to be low and fortunately not on ham bands.

Although the efficiency of the SMPS is very good a fan is added to cool it.
juma-pa1000-extra-fan.jpg
Extra fan for the SMPS

73 Matti OH7SV
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Re: JUMA PA1000 Linear Amplifier

Postby 4z4rb » 29 Mar 2012 17:44

The amp SP5G is playing with was built by me .
the output trafo is a 9:1 TLT wound with a semi rigid 25 ohm coax on a 1.5"core
Looksa like he made a nice case for the amp board I supplid him
very nice project!!
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Re: JUMA PA1000 Linear Amplifier

Postby K9FV » 30 Mar 2012 12:11

This is a VERY interesting thread - I've learned a good bit and hope to learn more.... especially the portion on output/input matching. I'm VERY interested in these TLT matching. I've got my head around the RF1000 type, but TLT are a different thing. I've been doing reading and learning more. I have made a 4:1 coax TLT using a coax type cable about 25 ohms, that worked pretty good on testing with 10 ohm resistor for the low Z. Now to test a 9:1 TLT.

This "U" type using semi-rigid 25 ohm coax I don't understand. Does anyone have a link or info on how to build or wire up a 9:1 ratio of the "U" type?

Thank ya'll for any guidance or suggestions.

73 de Ken H> K9FV
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Re: JUMA PA1000 Linear Amplifier

Postby G4ZOW » 30 Mar 2012 21:50

Matti,

So you ordered one of Christi's SMPS's :-)?

Does it come standard with soft start?

What about PFC?

If no PFC what do you plan in that department?

Baruch,

Congrats on your twin device HF board.

Have you implemented any gain levelling circuitry?

Are you marketing this pallet?

(((73)))

David
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