The AM Forum

I've never built a class E rig using analog drive. I've built several for 75 meters and one for 40 meters using a single FET with digital drive. I've always had difficulty with rig stability on 40 meters using any push-pull configuration due to gate capacitance (yadda - yadda).

I'm posting a picture from the class E website for ease of explanation. Looking at the push-pull setup, to make it work I gather you'd need to install a balun on the drive input if you were to drive this setup from a ricebox.

If so, great! How many FETs can you put in parallel on each phase on 40 meters without much difficulty. I'm imagining only 2 per phase.

I haven't started building anything yet, but I'm putting feelers out there.

Jon

Or just another boring ::) 8 FET digitally driven 75m transmitter, but after having learned from all my mistakes...

It's tempting because those 4-1000's look awfully nice sitting on the bling shelf. That glass cabinet is asking for something small too.

It's nice to have options.

Jon

Hi Jon...

Options are always nice  ;D

Have you received that parcel yet ?

40M sinewave drive is easy enough...
Have attached a photo of my first 40M TX using 4 X IRF840s class E.....
Appox 12 watts drive from a Icom IC-730 rig was plenty.....
That little coil with the ferrite through it on the left was adjusted for a 1:1 SWR for the ICOM...
Was a good little TX producing about 150watts carrier output.....

Cannot remember much more about it now.....


Wayne

Hey Wayne,

No package yet, but I did change addresses since then. I have arranged for mail forwarding though.

So, I do see some secrets hidden in that gem about analog drive. Very nice! (In my best Borat voice)

I like how you adjusted the SWR for 1:1. I was planning on just cramming the RF through a tuner. Or, if the SWR is way too high just put the Icom at 100 watts output and it'll automatically kick back to around 12 watts. You guys with your over engineering...  8)

Jon

Hi Wayne,
 That Tx'er appears to be something that Phil Wait VK2DKN published in Amateur Radio Mag (part one circ July 2008). I am sure anyone wanting detail will be able to find and download the article - a good starting point.

Hi Stuart...

I'm not sure what method Phil used in his sinewave drive.....
He did publish it in the Amateur Radio magazine sometime ago though.....

This design I used came from Wally WA2V?? which he posted on the old Class E forum quite a while ago now....

Phil is still using that TX and drives it with a rather large and old Collins Transmitter....


Wayne

Actually Jon have been thinking about your options  ;D

I reckon you should build Rods 75M VMCD TX .... the one I built up a few posts ago....
Have uploaded the picture again....

It goes very well and if you use exactly the parts I have you should get similar results  :)

Combined with the PWM ( steves design ) whenever you get it that is ... would make a nice small TX....

Just a thought....

Maybe after that build a Sinewave driven 40M TX using say the IRF840s .... 6 of them ......
Sinewave drive is quite easy and you would have a good power level of 200 watts ...........

 ;D

I've said it before, but I wish I could build and trace transmitter patterns like those works of art.

Yeah, I've settled on another 8 FET 75 meter rig (see the 'Tech Forum' last inductor post) for several reasons. I still do now have a garage full of literally 1000 lbs of iron, so that project will follow this one. It'll be a garage-mounted remote-controlled version of a 4-1000 x 3-500's. Maybe just driven by a ricebox for ease of construction. Aside from the wife's protests about the rig being upstairs, I hadn't thought about the heat generated from that rig in my shack. In the dead of winter I'd need to open the windows.

Or maybe have servos open and close the windows along with the PTT switch... eh...

Jon

All good...
No matter which way you go its all a bit of fun....  :)


Wayne

Yes, it is.

I just like being able to say that I'm the only class E operator in California. Bragging rights are always good.

Granted, I'm not there yet. I still need to build it... here. I've laid waste to Arizona already.

Jon

I
I've had a 500 watt PEP rig on 10 meters for a few years now. 

Especially great since their is no ten meter activity now.

It's a single ARF448 in class e.  Using a PWM and a positive peak stretcher circuit. 

So you'll be the second class E operator in California.  First on 75 meters, though.

--Shane
KD6VXI

I'll post pictures and my progress on this site.

Jon

Shane,
I can't fine info on the ARF448. Is that a typo??
Rod

ARF448 - a real RF MOSFET APT - now Microsemi still producing these and other TO247 style RF devices for 10m these are  8)

Jon, I have bad news for you. I've been running class E in California for fifteen maybe sixteen years. I have to check the dates. It was that long ago. Sine wave drive. Class H modulator. 300 W carrier. 75 meters. But I spell my name the same so people will probably mix us up. You should be fine.

Jon, K6JEK

The ARF448 is a redesign of another device we played with before.  Not cheap, but we sourced a couple from overseas.  It started out as a 2 device 250 watt amp, then I started looking at the class e papers available and found a Class e amplifier that did twice the power with half the semiconductors.  PROFIT as they say.

I don't think they are in production anymore, and if they are, they REALLY went up in price.  

However, for what they are, they do some serious power in class E.

https://wenku.baidu.com/view/39437020dd36a32d737581fb.html for the pdf of the amp.

I can say this.  If you build that 10 meter deck, it won't tolerate overvoltage!  Just a 10 pct increase in voltage let the magic smoke out.

--Shane
KD6VXI

In the paper about the ARF448 he mentions that the frequency chosen was twice the rated value for the device. So yeah, what Shane said.

Jon, wow, I don't believe we've talked on the air, at least while I was in Arizona. Anyway, I'm hoping to join the CA-E club here in a little bit. I'll be on the air this week with my tube setup. Pathetically I'm waiting on two 10 amp 5x20mm fuses to come in from eBay for my Acom amp. I needed to rewire it from 220vac to 120vac and it required new fuses. Absolutely nobody sells those fuses locally. I did an Amazon order and they screwed it up with the wrong values. I found this guy in Texas on eBay who sells them. One thing I do know about Texas, they know electrical stuff. I will get the correct fuses this time.

Anyway, catch you guys on the air.

Jon

Jon,

Not sure if he has those fuses, but Murphy's Junk in El Cajon will be your new best friend.

Huge surplus house.  He buys quite a bit of the military stuff as it goes to auction.  At one point he had 15-20 Collins 208-10U and pallets of 30L-1 amps.

--Shane
KD6VXI

I went to a surplus place in El Cajon and picked up a few items. Prices were, eh... good stuff though!

Jon

I spent most of my time growing up there.  We had two good ones, California Industrial Electronics and one whose name escapes me.  Then in High School Murphy's Junk came along and took over.

California Electronics is the place I talked about China came and bought the entire exportable inventory by the shipping container.  Thousands of vacuum tubes ended up in their.  California Electronics had tens of thousands of tubes. 

Other than those places, El Cajon is a dump.  115 plus sometimes in the summer.  I remember having schools close it was so hot.  I moved to the Mojave desert to cool off (lol)...  Kinda kidding, kinda not.

If you want surplus by the pound, there is a great place in north LA.  Apex Electronics and Surplus.  Also, the TRW swap meet is still going, although I haven't been since probably 1989 so I can't say what they have.

--Shane
KD6VXI

When my wife and I moved to the southwest years ago, we took a drive through California. It was late at night and we randomly picked an exit and grabbed a hotel. Early in the morning I got the idea to Google surplus electronics stores in LA. Wouldn't you know it, we had stopped just a couple miles from Apex. Tons of everything!

Sometimes brain neurons have a sixth sense about these things.

Jon

Ah, the fuses arrived today! Tested the transmitter and amp combo and it sounds great! I have an audio pickup on the feed line that goes to my headphones. So 150 watts carrier, for now. I did a test transmission. That poor transmitter survived the trip from Arizona, to the apartment and then to the house. Got to love tube technology.

Wife and I are going out for the evening so not on the air tonight, but soon. I’m really ecstatic that everything works (including automatic sequencer).

Jon

Congratulations