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Analog modulating a 1000 watt carrier class E rig




 
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Author Topic: Analog modulating a 1000 watt carrier class E rig  (Read 10522 times)
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ka1tdq
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« Reply #100 on: September 28, 2019, 01:48:48 PM »

It's funny but I'm almost a step ahead of you. I already have the bucket and it'd be easy just to add salt water!

Actually, I was using the bucket was for secondary containment.

I stopped at HRO this morning and got 100' of LMR400. I'll install it tomorrow. My kid's birthday party today.

Jon


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ka1tdq
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« Reply #101 on: September 28, 2019, 07:31:07 PM »

...and I let the smoke out. I'm not sure of exactly what, but it looks like one of the drivers. I'm thinking the problem all along was parasitics.

I replaced my antenna feed line with a near perfect SWR, tuned up at 300 watts with a nice safe waveform, unkeyed... When I keyed up again the waveforms were completely scattered with smoke coming from something.

I'm thinking I should've put those 300 ohm resistors inline with each driver.

Jon
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w8khk
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« Reply #102 on: September 29, 2019, 01:36:41 AM »

You might want to consider adding one of these:

http://www.classeradio.com/efficiency_meter_rev_f.pdf
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Rick / W8KHK  ex WB2HKX, WB4GNR
ka1tdq
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« Reply #103 on: September 29, 2019, 10:13:12 AM »

The 5-meter method does just as well.

At some point I'll pull the heat sink assembly, replace the damaged components and put in some parasitic suppression.

Jon
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w8khk
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« Reply #104 on: September 29, 2019, 10:37:32 AM »

The 5-meter method does just as well.

The idea here is that the QIX board monitors AND SHUTS DOWN immediately upon overload.  No human can respond to an overload that quickly while monitoring meters visually.  The alternative: ordering from Mouser or Digi-key and soldering OFTEN.  Certainly worth a careful look at this option.
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Rick / W8KHK  ex WB2HKX, WB4GNR
ka1tdq
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« Reply #105 on: September 29, 2019, 11:34:28 AM »

Oh
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« Reply #106 on: October 02, 2019, 12:43:46 AM »

Ugh! Oily cantennas!! You'd think Heathkit could have offered something with a bellows.
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« Reply #107 on: October 02, 2019, 10:46:35 PM »


I'm thinking I should've put those 300 ohm resistors inline with each driver.

Jon

Yes, those resistors have to be there, or the likelyhood of parasitics is quite high.

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ka1tdq
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« Reply #108 on: October 03, 2019, 09:49:29 AM »

It'll require a rebuild of the heat sink assembly.

Something to note, the transzorbs protected two of four mosfet modules. Once I cut out the transzorbs, the dead short went away from the drain bus for those two modules. Something else went as well with the remaining two modules.

After all this, I still had a sporadically fluctuating SWR problem when using my rice box. I had a coax splice in the shack that was intermittently making connection. I could shake the coax at the splice and SWR would jump all over the place. Once I put a new connector on, the problem went away. I'm sure this contributed to the parasitic problem as well.

It's a shame though to blow up a rig over a PL-259.

Jon
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ka1tdq
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« Reply #109 on: October 03, 2019, 07:45:50 PM »

Actually I take that back. I forgot that I installed two transzorbs per mosfet module. Once I cut them all out and did resistance checks, I realized that the drains were protected. So, all seems ok and I'll just need to solder on more transzorbs.

But, in the time since I thought I blew up my class E rig, I converted my 75 meter dipole into a 40 meter delta loop and bought an Icom 7300. What a nice rig!

Jon


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