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Transformer source

PostPosted: Tue Feb 26, 2008 2:46 pm
by mdburke-K9MB
I am working on getting components together for a Class E rig and found this source for toroid power transformers.
Anyone know anything about them? I assume that they are made in China. The specs look great and the prices are very reasonable with an 880VA transformer going for about $75 and a 1.5KVA going for $150 if you want to have a lot of extra capacity. Voltages available are diverse as well.
Anyone have any experience with these transformers? The guy there seems to be a nice person who answers questions fast and with some knowledge of his product. He also has HV transformers for tube amps and will be adding more of those in future.

Re: Transformer source

PostPosted: Tue Feb 26, 2008 3:40 pm
by kf1z
This is one question of yours I can answer!

I don't know where the cores are made, or primaries are wound....

The guy that sells them winds the secondaries himself.....

I use his 750va "42+42" volt xformer in my rig.... (2 modules of 12 fets..)

I couldn't see the point in spending more than twice as much from "maryland....".

And, he'll wind whatever secondaries you want.....

Re: Transformer source

PostPosted: Tue Feb 26, 2008 6:26 pm
by mdburke-K9MB
Hi Bruce,
Thanks for the information. I got good vibes from the guy at ANTEK because he acted like he understood transformers and if he was just reselling them, he might just send up a lot of smoke.
I am going to buy a 1.5KVA 52V X2 transformer I think. It should be big enough for all my megalomaniacal (is that a word? :? ) ruminations for the future and since you have had good luck with his products, I feel confident sending him my $155 plus shipping.
While I am getting your help. How about Electrolytics? I have a bid in on some 35,000MFD @80volt CDE Computer grade caps on Ebay, but they are pretty expensive at 4 for $68 and I am buying 8 of them so I will have 4 in parallel in series with 4 more so it will give me 140,000 at about 68VDC for the lower voltage and 70,000MFD for the high voltage about 136Volts for the high voltage supply. It will take about a minute to charge these babies, I guess. :)

Thanks for the response. I was wondering if my deodorant was giving up on me, since I had not had a response on the other posts about the FETs. My questions might be dumb, I am not knowledgeable enough about Class E to even pose a question that I know to be intelligent, but I have always learned by bumping my head against things until I find the doorways through or over them. (No wonder he doesn't have his pic up like some :) ).

I have downloaded a ton of articles on Class E by doing Google searches and there are som QEX articles printed in 2001 that I need to get copies of. It will take me a while to read all the 300 pages I have to read and maybe by then I will be smarter or worn out and give it up.
I am a design engineer that has been working with small transmitters and weak signal receivers in the 150-433MHz range for 30 years but we use bipolars for our RF Transmitters. I have used small Supertex FETS for a long time to turn on LEDs in my nursing home monitoring equipment, but have always wondered how they would work as RF amps, at least for low frequencies, and now I find that there is a whole website dedicated to that goal and I am thrilled. I will be retiring soon and my desire to home brew again will no doubt rise when I am not asked to do this stuff every day and I am getting my act together to get a Class E AM rig on 160 and 75 Meters.
Thanks again for the help.
73, MIke

Re: Transformer source

PostPosted: Tue Feb 26, 2008 6:55 pm
by kf1z
Ok Mike... fine....

As for the mosfet post.... I can take uneducated guesses...that's about it....
Though between this forum, and even a couple threads on , I believe the info you asked for has been discussed before....

Those people like Frank, Steve, and Floyd... and a select other few, sometimes take a while before they check here, and respond to posts....
Be patient....

As for caps... sometimes those Telco caps... 75volt@ 60,000mfd show up...
But still expect to pay around $15-20 used for each.....

I take it from the number of caps, and low/high voltage, you're building a class-H modulator? must be....

Do you have Frank GFZ's QEX article?.... if not, it's here:

A Single-Stage 1500 W Amplifier for 160 / 80 / 40 Meters

Re: Transformer source

PostPosted: Tue Feb 26, 2008 9:19 pm
by mdburke-K9MB
Hi Bruce,
Thanks for the advice. Your help makes me know someone will answer, so I am cool. I did find the 1500Watt article and it is a beautiful design. Excellent way to make the output transformer. I am wondering where I can get the larger ferrite beads that he mentions in the article.
I am considering doing what he did there and driving it with either my SSB rig or a Viking II that I am rebuilding instead of doing the FET drivers at first. I will do a modular design so I can switch it out.
Yes, I am planning an Class H modulator. I will probably make a PWM modulator later, but I am an old timer and something linear is easier for me to understand.
I have a lot to read and study, so that will keep me busy for a while too.
Thanks again

Re: Transformer source

PostPosted: Tue Feb 26, 2008 9:39 pm
by kf1z
Mike ,
The ferrites are SB-1020-43 ( Some call them FB-1020-43)
Are available at CWSBytemark, and they are $1.50 each,

Don't forget "digital" drive as well...(square-wave)
You don't need to use a transmitter to drive these....

I built Steve's vfo, and use the IXDD414 drivers...(1 for each 2 mosfets)
It's a very 'simple', easy layout... and the drivers aren't expensive...

Re: Transformer source

PostPosted: Tue Feb 26, 2008 10:09 pm
by mdburke-K9MB
Hi Bruce,
I got the link for those ferrite beads on the Class E site, but in the article, he talks about some bigger beads, but I don't see anything that big on the site for that link. I quote below:
"This amplifier was scaled to use
larger output transformer cores
than I had in my junk box. The next
larger size of commercially-available
core (1.5-inch OD, shorter, and
having a lot more core area) would
be a much better design choice. Using
these larger cores, the height of
the output transformer could be reduced
by 50% with a corresponding
reduction in leakage inductance
with a better aspect ratio".....

He goes on to say that even though the height is greater with these smaller beads, the efficiency was great, so I may just use them unless I can find them easily. I have some sources for toroids and beads that we use in my regular job, so I could see what is out there.
I know that the drivers look extremely simple and you don't have the problem of zeroing phase as you would with all those twisted pairs and I missed the fact that that device would drive two FETs I was under the impression it would only drive one, so at about $3.00 each too. I found some new ones from Microchip too, that look interesting. Do you use your amp on 75 as well as 160meters? I wonder if the drivers will drive two of them at 40 meters? It probably won't matter, because I am not that interested in 40 phone and 100 watts will work about anywhere on a winter night on 40 anyway. I am focused primarly on 160 and 80 meters.
I am in the planning stages, so a lot will change. That is the reason I am asking people who have already done this. Less painful that way if you learn from others experience.
Tell me about your rig. Is it the one on the Class E site -375Watts carrier? The 1500Watt version has 21FETS in it. Man that baby will suck some juice, but he was getting about 83% out of it, so it is amazing considering how many devices that are in parallel.
I wonder if you have used a product called Cool AMP? I ran into this stuff when I used to be active in the Central States VHF society and went to their meetings. It puts a very thin coating of silver on the copper one tenthousandth of an inch thick. This is not going to be carrying all the current at 160 meters, but it also keeps the copper from oxidizing, so it does serve a valuable purpose and with the high recuriculating currents in these amplifiers' tank coils, that could be a good thing and you don't have to handle nasty cyanides, etc... I found a source for it if you are interested, or if you know a better product, let me know.
73, Mike