'Tis the season for 10m AM! class-e amp help request

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Postby kf1z » Fri Oct 13, 2006 7:56 pm

Thanks Floyd,

Might make a little sense....

I downloaded "TL", and I'm not at all sure how you're using this program in this application....

Ok, on the use of the 259b... I don't have one now, and I just sold my "rf analyst" thinking it wasn't all that usefull to me anymore ( darn it ).

Anyway, I haven't chosen any particular device, as I am still trying to learn how to choose one.....and will probably start by experimenting with any of those mentioned here so far...I may even already have some irf540 and 510 (s).....


So you are designing your input circuit to match the total gate impedance to 50 ohms? So I'd assume then that you are using a transmitter as your frequency source...?
Is that the case, or did I miss something..?


Thanks Floyd,
bruce
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Postby blackplasma » Fri Oct 13, 2006 11:34 pm

hi Floyd,
I'm only aspiring to 13.56MHz for now, and brute force may be the best way to go, but thanks indeed for offering to help match.

cheers,
Matt
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IRF-510

Postby Stu » Mon Oct 30, 2006 4:12 pm

This maybe of intrest to someone (and since the irf-510 has been mentioned in this post)

http://home24.inet.tele.dk/oz1pif/50MHz_IRF510.htm

Yes I know its not class-e but shows that reasonable power can easily be achived from the irf-510's even at 6m so i am sure someone would be able to post a design for 10m for those of us that can follow the diagrams to build but arent to hot in the design dept. :-)
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Postby blackplasma » Sun Nov 05, 2006 11:58 pm

When inductance on the GDT becomes a problem (guaranteed ;-)), this setup has 40nH-60nH of leakage inductance. Working too close to the bar here, need to dig out my IRF730s. ^^

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Postby blackplasma » Sun Nov 26, 2006 10:11 am

I found pumping any kind of RF power at 22m (13.56MHz) difficult... I don't know how you guys do it 10m, but I bet it's satisfying if you never had to buy GaAs MOSFETs.

I give up. I don't have the know-how to make a good discrete driver that can crank any kind of power into a gate at these frequencies, so I wish anyone success at 10m.

Here's the output, splattering the spectrum as plasma; hope you guys will forgive me.

Switching device was a single IRF730, and its output capacitance of ~160pF + my added 50pF gave alright class-E operation. The scope shows Vds, 20V/40nS per div.

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Postby kf1z » Tue Sep 25, 2007 1:42 pm

WA2WVL wrote:Bruce, the first thing you need is the input impedance at the frequency.
I have measured this on some devices but maybe not the type you are using.
This is done by first assuming that the real (resistive part) is 1 ohm and calculating an "L" network to match this up to 50 ohms. Using a bridge
(I use an MFJ259B) to adjust the network for a perfect match. No circuit just connecting to the Gate to Source.
When you get the match take the shunt C value in the computer network back into the computer program and adjust the R to find out what the R really was. I use the ARRL program TL which comes with the Handbook. Forget the C because it is series tuned out by the L in the network. Now using Xc=1/2PIxFxC calculate the series Xc of the FET. For the IRF540N this comes out to be 1.51-j2.8 @ 28.5MHz.
Make sense?
Floyd


Floyd, are you still around??
Or any one that can help clarify this......

You state:
"This is done by first assuming that the real (resistive part) is 1 ohm and calculating an "L" network to match this up to 50 ohms."

Are you talking about just a capacitor from gate to source? or an inductor? Both?

Then you say:
"Using a bridge (I use an MFJ259B) to adjust the network for a perfect match. No circuit just connecting to the Gate to Source."

Which thoroughly confuses the first statement.....

I would like help on calculating this "L" network.....
For some reason (lack of knowledge I guess) I can't quite understand this....

Thanks to anyone who can set me straight....
It is indeed something I should already know how to do, and my next project is going to require me to know how to do it.....

Same goes for figuring the OUTPUT impedance of a mosfet (help there appreciated as well.... hint. hint)
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Postby VK3KRI » Fri Sep 28, 2007 4:24 am

I've matched the gate of a MOSFET with an L network for small transmitters, so it should be the same princiiple I guess. Source to ground, Small 'L' in series with Gate , Large 'C" from ofthe side of 'L' to ground and input applied ACROSS the cap. I think I have about 2200 pF for the 'C' to match 50 ohms to the gate of an IRF840 at 40m. The 'C' seems huge to be across the 50 ohm input , but it works.

Part of the 'L' is part of the L network, and part is series resonsnt with the input capacitance of the MOSFET to cancel the MOSFET input capacitance. I have no idea what value of 'L' i have , I just adjusted it so there is a match. The values to change a bit under power due to Crss I guess.
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Postby kf1z » Fri Sep 28, 2007 7:28 am

Thanks Ian,

That's what I've come to realize....

But, funny thing is, when you look at Floyd's designs that he's posted, there is only inductors and transformers....
Maybe in those circumstances, the "L" network wasn't needed.... or at least the "c" part..

I understand now that an 'L' network can be made up of 2 inductors, or 2 capacitors.....
So, could be that in Floyd's designs... the "L" network is made up of the series inductor, and the primary of the transformer to ground....

OR, I'm off, and it's just a different way of doing it!

In any case, thanks for the reply Ian,

Bruce
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Postby WA2WVL » Sat Sep 29, 2007 9:37 pm

Bruce, KF1Z I am sorry that I have not been reading my spots for some time. If you still need info please send me a message or Email.

I think I have figured out how to Broadband match LARGE FETS over 1.8-29Mhz. Operation would be class AB linear.
I just bought some IRFP90N20D FETS which I hope to use. These are 200V, 94A, 580Watt devices ($5.50 ea) They have very low feedback capacity which becomes very importain on 10 meters. (about 2.8% of Cin)
Floyd WA2WVL

PS: I will keep the Forum up on my progress
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Postby frank carcia » Sun Sep 30, 2007 8:43 pm

Cool Floyd,
Please share what you have learned as you know what I'm playing with.
The only problem with low voltage is the very low outout z. fc
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Postby kf1z » Thu Oct 18, 2007 1:14 pm

WA2WVL wrote:Bruce, KF1Z I am sorry that I have not been reading my spots for some time. If you still need info please send me a message or Email.

I think I have figured out how to Broadband match LARGE FETS over 1.8-29Mhz. Operation would be class AB linear.
I just bought some IRFP90N20D FETS which I hope to use. These are 200V, 94A, 580Watt devices ($5.50 ea) They have very low feedback capacity which becomes very importain on 10 meters. (about 2.8% of Cin)
Floyd WA2WVL

PS: I will keep the Forum up on my progress



well floyd,
I did send you an email on the 29th or 30th......but maybe you've been busy.....
just as well post any info you care to share right here for all to see....

right now I'm looking at some app notes from APT...
going to try some trial and error, based on that info.....

thanks floyd
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Re: 'Tis the season for 10m AM! class-e amp help request

Postby WA2WVL » Tue Jan 15, 2008 10:21 pm

Bruce: KF1Z

My spots on Metal Clad Micas was Dec 29 and Dec 30, 2005.

You also might look at my spots of Jan 26, 2006, Jan 30, 2006, April 13, 2006 and Oct 11, 2006

All of these relate to 10 Meter amps.

Floyd, WA2WVL
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Re: 'Tis the season for 10m AM! class-e amp help request

Postby KC7UTU » Mon Feb 18, 2008 10:52 pm

:idea: :idea:

HEY!!!

I'm thinking of a device that nobody has mentioned yet. EKL components is producing the replacment part for the 2sc1969 finals used in all the old 10m radios such as the galaxy-88 or any of the new RCI type radios: The ERF2030 by EKL should be perfect MOSFET for 10meter modulator/amplifier combo. Good luck digging up a data sheet for it though- I searched the web and found little about it but at $2.50 each for singles the price isn't too shabby.

I'm following this thread because I hope to start a project for higher frequencies like 10m, 6m or 2m

keep it going!

73

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Re: 'Tis the season for 10m AM! class-e amp help request

Postby W5EFR » Wed Nov 19, 2008 7:30 am

Sorry to bring up an old thread....

I saw something interesting recently.

While the Palomar company is long gone, everyone and their brother that builds "10 meter" linear amplifiers uses the name...

I saw this on an 11 meter forum... a Palomar Mosfet 700. It is supposedly biased in Class AB1 and the owner reports it has a bias voltage of 2.6 vdc on the gates

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It uses 4 FQP9N15 MOSFETs to drive 8 FQP9N15 MOSFETs...

I realize this isn't Class E, but the Mosfets may be usable for a 10 meter amplifier... just a thought, I'm not an Engineer, I don't play an engineer on TV, and I am way new to this Class-E thing...
Bow
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Re: 'Tis the season for 10m AM! class-e amp help request

Postby kf1z » Wed Nov 19, 2008 8:20 am

Don't be sorry!
I wish there was a little more discussion on the topic...
The solar cycle peak is only 2 or 3 (4?) years away!

So the unit yopu pictured.... is that a homebrew COPY of the Palomar amp?
Or is that commercially built by Palomar?

If the latter, Maked me feel good about the units I've built!

Thank for posting Bow.
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