My Big-E So Far...

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My Big-E So Far...

Postby N3LRX » Fri Mar 09, 2007 2:59 am

Here's the start of my RF Deck.
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Tank Coils and 160M Coil Shorting Relay. I'll be changing the shorting relay to another style or relay soon.
The inputs and Outputs of the Output Transformer. Red is the Secondary, Yellow is the Primaries.
The Zorbers are connected to the terminal block and to ground. I haven't added the .15mf bypass caps yet.
The Yellow and Orange wires connected to the block will carry the modulated DC.
The other Orange and Yellow wires will carry the the 24VDC and the 5VDC for the FET driver circuits.

Image
The butt end of the Output tranny and the Loading Cap.
The Tuning Cap is still on order..

Note:
There's no Iron! There won't be! The power supply is enclosed in a separate enclosure.
All the High Voltage, Low Voltage, and control voltages are mounted in one enclosure and routed where needed.
There is only one small 12V transformer for the band switching relays.

There's allot of room in this box without Iron! Perhaps I have room to add a 40M tuning circuit.. :)
The Heat Sink is not attached, It's still in the process of being drilled and tapped.
I have the FET Buses built already, pending some hole to screw them too..

I'm still waiting on the High Voltage Tranny from MD. Torrid I ordered a 96VCT 10A Torrid transformer. Once that's done I'll be able to complete the Power Supply.

As soon as I get the PCB's from Steve, I'll start working on the PWM Modulator. Which will also go into it's own enclosure.

More to come as the final pieces arrive!
73 DE Randy N3LRX
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look'n good!

Postby KD3CN » Fri Mar 09, 2007 8:57 am

Looks like a great start Randy. You did a nice job on those coils. Keep in mind that you may have to reduce them a little by tapping at a winding or two off the end. I had to do that to alleviate arcing on the tuning cap.

Keep going!
73, Karl
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Postby N3LRX » Fri Mar 09, 2007 12:58 pm

Thanks Karl,
Slowly but surly its coming along.

I used #6 on the 160M coil instead of #8, turns out nice because it's rigid enough to support itself without any help when both ends are secured. Still might add something, there is a little spring give but I doubt I'll be moving the RF Deck around while transmitting anyway.

Bruce reminded me the VFO has the IXD Drivers built in so theres no need for the 5VDC inside the RF Deck. So, I'll just change that to 12VDC and remove the relay control transformer.

I'm also working on custom meter faces haven't figured out what to print them on. Plain Ink Jet paper will fade fast, so I'm looking for something more rugged. Maybe Ink Jet Photo paper? Never used it so I don't know how sturdy that stuff is at holding color. Any suggestions? I still haven't drilled the faces on the enclosures for mounting anything yet. If I screw up drilling the bottom or back I can cover it up, with the faces I may not be so lucky. :( So I'm making sure everything lays out perfect before I poke any holes.

When I get the PCB's from Steve I'll know how much space I've got in the PWM box. I may have enough space to build the VFO into a sub enclosure inside there and have the freq display on the face of the PWM. I have a small single board Freq counter that could be used for that.

With all the iron, caps and rectifiers in the power supply that's about the tightest packed enclosure in the project. That 'Spare Tire' power transformer takes up some space! :D The 12V Bosta Tranny is no slouch either! LOL The other control voltage transformers are small since theres nothing that demands over 5 amps.

Sweet, Simple, and plenty of room to work inside, Old Buzzard style, can't quite walk around inside like a B-Cast transmitter, but theres still allot of space! Just the way I like it.. :D
73 DE Randy N3LRX
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Postby kf1z » Fri Mar 09, 2007 3:04 pm

Looking good Randy!

If you are using the 96 volt transformer....

You probably WON'T be able to use the boost transformer!
(of course, that depends on the input voltage rating, and your actual line voltage...)


96 volts.... rectified, filtered.... you'll be around 125 to 130 volts dc....

if you add 12 volts, you'll be up around 140 + volts.


If you look at Steve's powersupply schematic....
You'll see he's using an 88 volt transformer.... and then a "boost" tranny.


My opinion is..... save the space and leave the boost transformer out....



As far as the meter faces go.... I have photo paper for the printer...
But, don't know how long they go without fading.....
Haven't had it long....



Anyway....

I just got some new rack mount boxes...
And will be rebuilding my transmitter and modulator in the next few weeks.... when other projects get caught up....

I'll post some pics along the way...



Have fun!
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Postby N3LRX » Fri Mar 09, 2007 3:27 pm

It's actually 76VAC@9A Series, or 2x38VAC@18A in parallel.

So it's slightly less power than the 88VCT Steve's using.. I just double checked and I did order the smaller one. (Less expensive)

I got the 12V transformer which is actually a 24VCT pretty cheap. (16A@12V/8A@24V)

May result in less power outpoot without the Turbo Power but it still should be within range to run OK Fine.. (I hope! :))
73 DE Randy N3LRX
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Postby kf1z » Fri Mar 09, 2007 8:07 pm

Oh, ok well that makes a difference...

So if you run your 76 volts (38x2), and 24 volts on the boost, you'll be running 100 volts ac in.

That's the same as Steve's with the 88v, and 12v xfrmrs.


I got my toroidial transformer off a guy on ebay (still sells them)
For $50 + sh
It's a 110v Pri / 40v Sec (x2)....
BUT my line voltage is always above 125 volts.
So I get about 92 volts AC out of the two Secondaries in series....
My rectified dc sits at about 127vdc


Don't worry, with those two transformers.... you'll have full power....
No problemo.....
(Steve's 88v trans. are rated at 5.5 amps I believe)
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Not Bad for a few hours work.

Postby N3LRX » Mon Apr 02, 2007 10:42 pm

The PWM Generator board.
Image
Image
The Regulators and most of the Caps are soldered, The IC's are Socketed.
I need to order some pots now that I know the package the board is designed for. There are a few other Caps of various values I overlooked that I need to get also.

The Shutdown / Efficiency Board
Image
Image
Most components are soldered and IC's are socketed.


The next task is to solder the resistors, this is the hassle since I don't have my resistors sorted. So it comes down to finding each value the hard way. Still, not bad for only a few hours work. I started at 8 O'Clock AM tonight and finished up for the night at 11 O'Clock PM
73 DE Randy N3LRX
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Postby steve_qix » Tue Apr 03, 2007 7:20 am

Looks good !

A couple of questions - where are the MOSFETs going to be mounted? Didn't see them anywhere, and wasn't able to figure it out from the description. Is the heat sink in the left side of the picture?

The primary lead from the output transformer to the MOSFETs, and the lead from the other side of the primary to the RF bypass capacitor both should be as short as possible. This is a low impedance circuit, and additional inductance caused by long leads in the primary connection is undesirable.

Also, keep in mind, the RF output transformers can get very warm and need ventilation :wink:

Any TransZorbs in the RF drain circuit need to go directly from the drain bus to the source bus. These leads must be fairly short, otherwise there will be inductance in series with the TransZorbs, and they will not protect the drain bus in the event of a voltage spike. Same with the shunt capacitors - actually these leads need to be shorter still, to prevent ringing in this low impedance circuit.

The lead lengths on the secondary side are not so important. Since there is already considerable inductance present (the tank coil), the leads simply add to this. The only consideration here is radiation from the leads themselves into other parts of the circuit, into wires running out of the cabinet, or to other circuits that have nothing to do with the RF amplifier.

The modulator boards need to be easily accessible -and- accessible when the transmitter is operating. There are a number of measurements to be made, along with adjustments that can only be done when the unit is fully operational. I only mention this because I have seen some implementations where the boards were hard to get at, and this made adjustment and possible troubleshooting almost impossible.

Sure looks like a good start :) The only thing that you might consider changing would be the location of the output RF transfomer, to get shorter primary leads, if possible 8)

Talk later and Regards,

Steve
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Postby N3LRX » Tue Apr 03, 2007 8:40 pm

On the RF Deck the FETs aren't shown. The heatsink will be mounted in that big hole in the back where the yellow primaries are. By the time I'm done the primaries wont be but a few inches long. They're long in the picture because they're rough cut.

My FET buses are pretty tight. I made all connections there as short as possible. I just have yet to get my heatsink drilled and tapped to mount them.

My Mod Deck will have plenty of room. The PWM and the Eff/SD board will have their own box, Theres going to be more than enough room for easy access tuning. Plenty of room for expansion as well.

The Power Supply is also in it's own box. The filter Caps, HV Relay, Iron, and Rectifiers are in the P/S box. All DC lines will be bypassed to prevent any transient RF between units.

I do have one question (so far, there'll be more!) Since I am only using 2 FETs in the PWM Output do I also leave the 1N4937 Diodes and the 5 Ohm Resistors out as well? I know I am only supposed to use 2 of the DESI30's but I was unsure of the others. Does it matter whether they are in or out? I'd assume since there is no FET they'd just sit there and do nothing. But I don't want to detune anything by leaving them in without asking.

Both PWM boards and the Efficiency Meter board are now mostly populated. All that is left are the trim pots and the precision resistors in the anti-alias that I have yet to order.

I'm almost there! Now it comes time for me to get the courage to start popping holes in the face plates. I'm a bit paranoid about that. I can make mistakes inside, on the back, or on the bottom and it won't be seen. Popping holes in the front though, if I screw up, I may not be so lucky as to covering it up.
73 DE Randy N3LRX
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Postby steve_qix » Wed Apr 04, 2007 1:41 am

Hi Randy,

On the PWM boards - for every MOSFET, put in 1 DSEI30-06 diode and the appropriate resistor/speedup diode on the gate side :-)

On the lead lengths of the RF transformer primary - a few inches is longer than any I've seen. You'll have to see how it works. I usually keep mine to under 1 inch, and so far, no problems !

Looking forward to the testing. Make sure the transistors (2n3904/2n3906) are in correctly. The silk screen layer on some of the boards, and the holes do not line up correctly with the transistor layout in some cases. The tab on the silk screen layer is always correct - and that's the emitter of the transistor. Both the 2n3904 and 2n3906 are E-B-C, with the flat side facing you. The emitter is on the left. If your transistors' emitter lines up with the tab, you'll be all set !

Talk later and Regards,

Steve
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I Got's Me some I-ron!

Postby N3LRX » Fri Apr 06, 2007 5:13 pm

I Got's Me some I-ron!, some Powdered Iron anyway, My big old Spare tire lookin' toroid transformer came in today so that completes the parts for my Power Supply. I've been a bit under the weather but maybe tonight I'll finish slobbering up that. Then I'll have at least one complete unit for the transmitter..

I've over built everything in the Power Supply for current rating so it's a pretty but Nasty beast! Separate power sources for all the various voltages. Good thing I decided to build it in it's own enclosure because I doubt I'd be able to fit it in with anything else! I'll post some Pics when I get it done!
73 DE Randy N3LRX
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The Closer I get..

Postby N3LRX » Thu May 03, 2007 11:19 pm

The Power Plant:
Image
The nearly finished Power Supply, all the iron to power the various sections of the transmitter.

The PWM Modulator:
Image
The PWM boards mounted in their final resting places. All physical interconnect wiring is done. All that awaits is the heat sinks for the output stage and the external chassis connections
73 DE Randy N3LRX
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Postby steve_qix » Thu May 10, 2007 7:46 pm

Looks good ! Hey, put a TO220 heat sink on the 5 volt regulator on the overload/efficiency meter board. Without one, the regulator gets hot.

Otherwise, looks good :-)

Regards,

Steve
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Postby N3LRX » Thu May 10, 2007 8:58 pm

I was going to ask that.. I've got the 7812 on the PWM Board bolted to the chassis the 7805 and the 7912 I'll use a spacer and Sil-Pads on them. I've got a handfull of TO-220 heat sinks I may just grind the down a tiny bit so they fit between the chassis and board without adding pressure to the IC. I found some 7912's in plastic cases. I may pull out the metal tabbed 7912 and use them. They're 1 A instead of 1.5 A but I can't imagine that being a problem the low level circuits can't really pull that much can they?

For the L/C on the PWM Filter I'm going to use Orange Drops. I'm assuming theres quite a bit of current potential there.

I've added the Neg. Ext. Peak Pot and the Carrier Level Pot to the front panel and a ext. line level in pot to the rear panel. I'm still thinking about putting a balanced input and an XLR so I can come directly from my audio chain with XLR's. Right now I'm using a 1/4" Stereo jack using the tip and ring to isolate the input from chassis ground. I tried to breadboard the Mic PreAmp together last night and bastardized that.. I may wind up ordering the PCB sometime soon.. I don't need one but it would be nice to have so if I decide to take the TXer on the road I don't have to drag the audio rack along with me unless I want to.

Can't make up my mind on an interconnect I might just use an SO-239/PL-259 and RG-8 for the PWM Output. First I'm going to check the hamfests for some of those round ITT/Cannon Military type connectors I'd rather use them. I'm also still debating on putting the low voltage Iron for the boards in the PWM case or leaving them in the power supply unit.

I still haven't had the guts to drill any meter holes yet. I already hosed up my Power Supply Chassis trying to drill the Volt Meter hole. I hope I can recover the cosmetic appearance after my mistake. I will try to get over to Bacon Slab's Casa (Frank KB3AHE) this weekend and see if he can help. I think he's got a drill press and I don't. That was my mistake I think. A drill press is a MUST HAVE for drilling the sinks too.. I've got the drills and the taps for that. I was going to have someone do it for me but he's too busy right now and I'm impatient LOL! (As if you didn't know that already! Hee Hee)

I've got some VU meters I'd also like to put in. And some sort of Swinging Monkey audio meter for PWM Output.

Too many ideas and conflicts in my own decisions! If I keep this up I'll never get done! LOL
73 DE Randy N3LRX
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Postby steve_qix » Sat May 12, 2007 8:58 pm

The 7812 and 7912 regulators don't get excessively warm to warrant heat sinks.

I would be wary of grounding the 7812 tabs to the chassis or cabinet. THis may cause unwanted ground loops and/or other problems with RF, etc.

Only the 7805 on the overload/efficiency meter board gets warm enough to need a heat sink ! :-)

Regards,

Steve
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