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Author Topic: A Clean Canvas - 24 Pill Class E Rig Construction  (Read 166874 times)
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WD8BIL
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« Reply #175 on: April 27, 2010, 02:09:59 PM »

Tom, If it helps here's a peak amp I built up, and am still using, for element powered wattmeters.
You can remove the diode and cap in the peak detector to drive your comparator inputs.
You could even use the forth stage as the comparitor.


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K1JJ
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« Reply #176 on: April 27, 2010, 02:11:47 PM »

Take the bird positive and connect it to the negative input. Then take the bird negative and connect it to the positive input. Then adjust the pot for the trip point you want. If that doesn't work you will need to change some resistor values around the comparator.


That's what I tried last night and NG.


What resistor values would you change to make it more sensitive?   Actually that board is so tiny to work on I'd almost rather add a transistor outboard as an interface gain stage.

Thanks for the schematic Buddley.

T
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« Reply #177 on: April 27, 2010, 06:21:51 PM »

sorry I told you to connect the bird backwards. Plus to plus and minus to minus. Remove R732 to eliminate the voltage divider on th epositive input
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K1JJ
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« Reply #178 on: April 27, 2010, 06:42:42 PM »

I built up a single 2N3904 NPN transistor circuit that amplifies from 0.3 to 5V.  That shud give it plenty of drive.  The DC output is 0-5V.


I'll test this circuit in operation later and post how it works out.

T
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« Reply #179 on: April 27, 2010, 10:28:22 PM »

Not to hijack the post, but I found the problem with current drop. Was a bad driver chip (IXDD414) in one of the banks. Also got the 40 meter 10 fet deck upgraded with coax distribution and termination resistors to the driver chips...had the deck on the air for a couple of hours and rock solid! Grin

Tina
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K1JJ
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« Reply #180 on: April 27, 2010, 10:55:40 PM »

Good going, Tina!

That's a good thang to know since mine is using the same drive config.

T
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« Reply #181 on: April 28, 2010, 09:31:56 AM »

HTF did you manage to blow a driver chip?
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W1IA
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« Reply #182 on: April 28, 2010, 02:19:23 PM »

HTF did you manage to blow a driver chip?
Long B4 I had the correct amount of shunt and ATC caps. Bad cable to one of the phases etc...
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WD8BIL
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« Reply #183 on: April 28, 2010, 02:35:05 PM »

Quote
HTF did you manage to blow a driver chip?

Hey it's TINA!!! He can do it all!
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K1JJ
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« Reply #184 on: May 10, 2010, 04:01:55 PM »

Fired up Rico Suave for a contact on 75M today. Eric made a recording and Joe/PJP broke in with his KW-1 rig. I will have to upload it somewhere else cuz it's 5 meg.

I spent the last week trying to get the PDM pulses out of the homebrew VFO and sequencer board. I'm running Rico at a conservative 1/2 voltage = 250w out for now.

So far, so good. The VFO is stable and the full digital drive is very stable.

I spent a LOT of time bypassing, filtering and shielding various components before all was stable. Thanks to Jay/W1VD who sent me some "chip" capacitors so I could build a "zero lead length" type PC board for the transformer B+ bypassing. This made a big difference and got rid of any parasitics. Those orange drop caps are NG for RF.  I have three 0.1 chip caps per module to ground now.

I added four fuses, one for each MOSFET module. Also added fuses to every PC board for good measure. Notice how clean the transformer area is now that those big orange drop caps have been replaced by tiny chip capacitors.  I went on a days-long campaign adding filters, protection and bypassing bells and whistles. It appears to have paid off in general stability and good operation.  The E waveform looks textbook, but the jury is out until I goose it with X4 power.

I like the sound of the audio, though I am fighting a little hum from a ground loop. The E rig is about 15' in cable length from the audio rack and other gear.

Hope to ramp it up and get on with it more this week.

T





1) RF deck showing new filtering on the drivers and finals

2) Close up of the RF transformer bypassing.

3) More


* 4X1 Rig 774.jpg (321.13 KB, 1280x960 - viewed 850 times.)

* 4X1 Rig 785.jpg (325.89 KB, 1280x960 - viewed 819 times.)

* 4X1 Rig 776.jpg (328.29 KB, 1280x960 - viewed 773 times.)
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Use an "AM Courtesy Filter" to limit transmit audio bandwidth  +-4.5 KHz, +-6.0 KHz or +-8.0 KHz when needed.  Easily done in DSP.

Wise Words : "I'm as old as I've ever been... and I'm as young as I'll ever be."

There's nothing like an old dog.
K1JJ
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« Reply #185 on: May 10, 2010, 04:05:35 PM »

Shielded cables in and out - and damper diode beer can added to PDM filter.  The beer can helped to quiet down the PDM spikes.



* 4X1 Rig 777.jpg (321.88 KB, 1280x960 - viewed 784 times.)
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Use an "AM Courtesy Filter" to limit transmit audio bandwidth  +-4.5 KHz, +-6.0 KHz or +-8.0 KHz when needed.  Easily done in DSP.

Wise Words : "I'm as old as I've ever been... and I'm as young as I'll ever be."

There's nothing like an old dog.
K1JJ
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« Reply #186 on: May 10, 2010, 04:26:47 PM »

http://www.filexoom.com/showfile-19820/75m_rico_suave_e_rig_k1jj_wa2pjp___wa2cau.mp3

This is a recording made today by Eric/WA2CAU of Rico Suave and PJP. It's in 10KC bandpass. (5KC audio)  I did a brief description of the rig and you can hear the audio quality.

Eric's comments cannot be heard. There are several transmissions combined together.

The file is 5 meg and takes a minute to download.

T

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Use an "AM Courtesy Filter" to limit transmit audio bandwidth  +-4.5 KHz, +-6.0 KHz or +-8.0 KHz when needed.  Easily done in DSP.

Wise Words : "I'm as old as I've ever been... and I'm as young as I'll ever be."

There's nothing like an old dog.
David, K3TUE
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« Reply #187 on: May 10, 2010, 10:03:05 PM »

[...] I designed and built a stripline IPA for my 220 repeater some years back. [...]

I've been curious, does anyone work on 220 any more?
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« Reply #188 on: May 11, 2010, 07:35:02 AM »

Shielded cables in and out - and damper diode beer can added to PDM filter.  The beer can helped to quiet down the PDM spikes.



Ahhhhhhhhhhhhhhhhhh... I see one thing that could be the cause of all problems :-)  The first inductor of the PWM filter, and the first capacitor after the first inductor should be located immediately at the PWM output, and not carried away from the output board at all.  In fact, the inductor ideally should be located away from the remainder of the filter unless your PWM output board happens to be co-resident with the filter.

Once the PWM signal is processed by the first inductor, there will be no spikes to worry about.  But, carrying the PWM signal away from the PWM output board is not a good idea at all.  The PWM output signal is rich in harmonics, and these harmonics are of considerable power.  By carrying the pwm output signal away from the output board, there is also a danger of coupling "around" the filter, due to ground effects, ground inductance and the like.  See how it works, but it might, at some time in the future, be advantageous to move the first inductor and the first capacitor and put them at the PWM output.

Something else to consider with respect to the PWM filter.  This is probably not a big deal, but I did notice it immediately.  It is preferable to bring both wires interconnecting the inductors directly to the capacitors, and then have them go on to the next inductor.  In this way, there is no inductance added in series with the PWM filter capacitors.  The interconnecting wires are part of the inductance of the inductors, but you don't want an wiring in series with the capacitors.  Maybe it's not a problem - but I thought I'd point it out.

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WA1GFZ
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« Reply #189 on: May 11, 2010, 10:00:25 AM »

WOW I agree. You are switching a 130 volt squarewave. You should consider moving the output board to the filter plate for best performance. You are running a lot of juice through coax cable. I bet it will run warm. Consider pulling the guts out and sliding #8 or #6 in place.
Inductance in series with the caps hurts high frequency roll off. A big deal in tank circuits also.
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W1IA
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« Reply #190 on: May 11, 2010, 10:15:47 AM »

Overhaul of the old 20 pill deck.
It begins Smiley


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« Reply #191 on: May 11, 2010, 10:56:53 AM »

Hi Brent, Looks like a good start !!

I would put another screw, holding the source bus to the heat sink, between each of the existing screws.  Basically, 1 screw per MOSFET - located more or less between them (and at the ends of the bus, of course) works very well.

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K1JJ
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« Reply #192 on: May 11, 2010, 11:47:52 AM »

Hmmm...  That's probably why I had so much trouble filtering out the PDM pulses from the other boards.  I will reposition things to get L1 close to the PDM power borad output. The rig is running very FB at 400 watt carrier now, so the additional filtering I did only helps it become even more stable when the filter is set up correctly.

I'll also modify the capacitor leads between inductors as you suggested, Steve.

Last night after a 2 minute transmission the VFO broke into a nasty phase noise FMing according to the guys. It turned out that the 12V voltage regulator on the VFO driver board was running too hot, despite a small heatsink. I added four larger heatsinks to all the regulators and two 414's and it ran FB afterwards. Those regulators will shut down due to a thermal sensor internally.  I found that all the tabs in the four devices are at ground, so ONE heatsink plate could be bolted on for simplicity.  Tho, separates are better for servicing.

All in all, after a robust one hour on 75M last night, the rig ran superbly. The RF heatsink was barely luke warm and all appears very stable with no parasitics. The VFO is dead solid.

BTW, that 100 pf doorknob on the input of the L1 filter shown in the pic above  - I removed it, as it caused slight ringing in the pulse.


This is alien technology, I think... Grin


Brent:  That's a nice looking start. I see you left room for another 24 pills, caw mawn... Wink  Be sure to bypass the heck outa the vcc 414's bus.  I used several different types of caps there. Also used some input filtering using ferrite cores and bypass caps on the left edge of the heatsink. (see pic #1 above)

T

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Use an "AM Courtesy Filter" to limit transmit audio bandwidth  +-4.5 KHz, +-6.0 KHz or +-8.0 KHz when needed.  Easily done in DSP.

Wise Words : "I'm as old as I've ever been... and I'm as young as I'll ever be."

There's nothing like an old dog.
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« Reply #193 on: May 11, 2010, 12:21:20 PM »

HF ringing is due to long lead length between switch and first inductor.
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« Reply #194 on: May 11, 2010, 01:08:27 PM »

Hi Tom,

I reserved comment on the capacitor input to the PWM filter, theorizing you might have had some good reason for this capacitor that excaped me, but since this is not the case GET RID OF THE INPUT CAPACITOR ON THE PWM FILTER :-)  Grin  In fact, do everything you can to MINIMIZE the capacitance in the PWM filter input inductor and output stage.

Yes, do move the input filter inductor and first capacitor following the input inductor.  This will cure many ills.

The IXDD414s and regulators in the VFO / Phase Splitter board MUST be heat-sunk.  I thought this was shown in the documentation, but I'll surely check it.  If you notice, all of those components are at one edge of the board, so you can bolt all of them to a chassis or heat sink.  All are tab-grounded devices, so no insulators needed when screwing these components to a heat sink.

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K1JJ
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« Reply #195 on: May 11, 2010, 01:56:20 PM »

Steve,

I was able to shorten the PDM power board lead to about 6" total length from the board to the L1 input terminal. That's pretty good considering the previous routing.  The lead previously went tnru a terminal strip, thus the longer route. All that is gone now. I fixed the filter cap leads too.


You said to minimize capcitance - but can I still add some shield wrapped around this 6" PDM lead and grounded or will that add enuff capacitance to degrade things?

I did have small heatsinks on the driver board, but they were not big enuff. Now the devices get luke warm with the bigger sinks.


The 100 pf input PDM filter cap was gone as of last night.

T
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There's nothing like an old dog.
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« Reply #196 on: May 11, 2010, 02:27:06 PM »


You said to minimize capcitance - but can I still add some shield wrapped around this 6" PDM lead and grounded or will that add enuff capacitance to degrade things?


Hi Tom,

It probably won't hurt anything, but only 6 inches of wire probably won't be an issue.  I don't run any shielding, and the wire running from the PWM output board to the coil is longer than 6 inches.  Since the coil isn't shielded either, I wouldn't bother  Wink
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« Reply #197 on: May 11, 2010, 07:53:06 PM »

Tom,

Despite the fact that I didn't shield the approximately 8 inch wire running from the PWM output to the PWM input filter inductor - and the inductor itself (air wound) is also unshielded, I don't get into anything at all - anywhere, with the PWM signal.  If you bring an AM broadcast receiver into the vicinity of the rig when I'm transmitting, there is some white noise.  That's about it.

So, it probably won't be an issue with your rig either if you don't shield that 6 inch interconnecting wire.
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« Reply #198 on: May 11, 2010, 10:56:59 PM »

Tom,

Despite the fact that I didn't shield the approximately 8 inch wire running from the PWM output to the PWM input filter inductor - and the inductor itself (air wound) is also unshielded, I don't get into anything at all - anywhere, with the PWM signal.  If you bring an AM broadcast receiver into the vicinity of the rig when I'm transmitting, there is some white noise.  That's about it.

So, it probably won't be an issue with your rig either if you don't shield that 6 inch interconnecting wire.
Steve is there  max length (never exceed) on the output of the driver to the PDM filter? I may rethink the layout when I rebuild the filters.

Brent
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« Reply #199 on: May 12, 2010, 07:00:31 PM »

Added additional screws to source buss and soldered legs of devices.


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