[Amps] More on Toroidal Tank Circuit Issues
Jim W7RY
w7ry at centurytel.net
Fri Mar 28 19:47:07 EDT 2014
Do you think that #12 enameled close wound would withstand the voltage turn
to turn? The coil I have is #14 on a ceramic core. The wire is spaced about
the same size as the #14. So there is space for
cooling. And the coilform has lots of holes in it for even better
ventilation.
I would think that 125 degrees F is no problem for #14 on a ceramic
coilform?
My calculations:
#12 enamel is .085 dia. X45 turns = 3.825 inches long.
A coil that is 2" X 3.825 is 42.8 uH which is what I need.
Thoughts?
73
Jim W7RY
-----Original Message-----
From: Carl
Sent: Wednesday, March 26, 2014 7:36 AM
To: Jim W7RY ; "Undisclosed-Recipient:;"@mx.contesting.com
Cc: AMPS
Subject: Re: [Amps] More on Toroidal Tank Circuit Issues
That form is grooved too tight for larger wire but Carl also has #10 and 12
heavy enameled copper wire.
----- Original Message -----
From: "Jim W7RY" <w7ry at centurytel.net>
To: <"Undisclosed-Recipient:;"@mx.contesting.com>
Cc: "AMPS" <amps at contesting.com>
Sent: Wednesday, March 26, 2014 12:36 AM
Subject: Re: [Amps] More on Toroidal Tank Circuit Issues
> So here is the real fix!
>
> I removed the 80 and 160 meter toroids all together. Installed a 2" dia X
> 3.5" long ceramic coil with 42 turns of #14 wire and hooked it to the end
> of the 40 meter coil. The new coil is perpendicular to the 20-40 meter
> coil.
>
> Works perfectly! No more 10 meter heating! And on 80 meters, with lots of
> keydown at 1600 watts out, the coil gets to about 125 degrees F, and on
> 160 a little less. But I normally don’t run RTTY on 160 meters. As of yet,
> all RTTY contests are on 80-10.
>
> The best bet will be to find a ceramic coil or just the coil-form that I
> can wind with #12 or #10 wire. 10 is probably a bit too big. I guess I
> could wind 80 meters with #10 and 160 meters with #12. I really want to
> stay with a ceramic coil-form to keep it from deforming like a air-dux
> coil would.
>
> I know Carl has a ceramic form on the auction site but it too is wound
> with #14 wire.
>
> Anyone have a 2" (and it must not be more than 2-1/4" X 5 or 6 inch long
> ceramic coil-form with grooves for winding? It has to have at least 36
> grooves for 36 turns of wire.
>
> This has been an interesting experiment to say the least!
>
> Thanks all
> 73
> Jim W7RY
>
>
> -----Original Message-----
> From: Jim W7RY
> Sent: Saturday, March 22, 2014 1:25 PM
> To: Dan Hearn
> Cc: AMPS
> Subject: Re: [Amps] More on Toroidal Tank Circuit Issues
>
> So I used the measurement technique from Tom W8JI that he has on his site
> and found that the 160 meter toroid was certainly resonate on 10 meters!
> No matter what I did. Sure, I could move my hand around the toroid and get
> the the lamp to dim and sometimes go out. But there didn’t seem to be any
> place moving the windings that would help.
> http://www.w8ji.com/rf_plate_choke.htm
>
>
> So..... I made a center tap on the 160 meter toroid and simply shorted it
> to one end with a normally closed vacuum relay. I open the relay only on
> 160 meters.
>
> See here:
> http://s900.photobucket.com/user/w7ry/media/8877%20Amplifier/IMG_0250_zps17bca129.jpg.html?sort=3&o=0
>
> Seems to work just great. No arcing or sparking. As you can see, the leads
> are pretty long and the relay is just taped to the Plexiglas. I used the
> bench power supply to energize the relay on 160. There was no interaction
> with anything. Even had the lid off when testing 160 meters.
>
> The toroid seems to run perfectly cool (about a 10 degree temperature rise
> on 10 meters measuring with my Fluke IR thermometer) when operating on all
> bands. Tuning seemed better and more power output with less drive and
> lower plate current for the same output power (1600 watts) on 10 meters
> just like removing the toroid all together.
>
> I'm going to move the 160 meter toroid back to where it was, and move it
> further from the load vacuum cap. If I had it to do over again, I would
> have mounted the caps closer to the outside walls to give me more room to
> work between them.
>
> I’ll also have to wire up the relay to energize on 160 meters. Rather than
> tie into the tuned input switching, I’ll just put another switch contact
> between the front panel and the sub panel.
>
>
> 73
> Jim W7RY
>
>
>
>
>
> From: Dan Hearn
> Sent: Friday, March 21, 2014 5:47 PM
> To: Jim W7RY
> Cc: AMPS
> Subject: Re: [Amps] More on Toroidal Tank Circuit Issues
>
> Jim, I would try a small air wound coil similar to what you would use in a
> parasitic suppressor in series with the toroid, maybe in the lead to the
> switch.
>
>
> Dan, N5AR
>
>
>
>
> On Fri, Mar 21, 2014 at 4:46 PM, Jim W7RY <w7ry at centurytel.net> wrote:
>
> Both leads are shored by the band switch when on 10 meters guys.
> Interesting that 3 of you came up with the same possibility...
>
> Not sure where to put the capacitor if both leads are shorted together.
> Perhaps I could center tap the toroid (bare the Teflon wire) and solder a
> cap from the center tap to one of the output leads.
>
> I removed the toroid and the major heat in the 3 turns of wire is where
> the winding is within 1/4 inch of the vacuum loading cap. Which is
> probably to close.
> See:
> http://s900.photobucket.com/user/w7ry/media/8877%20Amplifier/P1010217.jpg.html?sort=3&o=16
>
> I was simply going to move it away from the loading cap and see what
> happens. I was also thinking of install a wire coil. I have a ceramic coil
> form that would work. 30 turns, 2”dia 3.5” long which is 20uH. I have room
> to mount this.
>
> Thanks all!
> 73
> Jim W7RY
>
>
> From: Dan Hearn
> Sent: Friday, March 21, 2014 3:02 PM
> To: Jim W7RY
> Cc: AMPS
> Subject: Re: [Amps] More on Toroidal Tank Circuit Issues
>
> Jim, I think your 160 toroid when shorted is self resonant with its
> distributed capacitance on 10m. You might be able to solve this by
> putting a small cap across the 160 m toroid to move its self resonance.
>
>
> 73, Dan, N5AR
>
>
>
>
> On Fri, Mar 21, 2014 at 1:08 PM, Jim W7RY <w7ry at centurytel.net> wrote:
>
> I may have to eat some crow here about using dedicated toroids on 160
> and 80 meters...
>
> I built an 8877 amplifier based on the K8RA (SK) 3CX1500D7 amplifier.
> http://www.k8ra.com/index_049.htm
>
> Mine is shown here:
> http://s900.photobucket.com/user/w7ry/media/8877%20Amplifier/DSC_0037.jpg.html?sort=3&o=47
>
> And here:
> http://s900.photobucket.com/user/w7ry/media/8877%20Amplifier/P1010225.jpg.html?sort=3&o=13
>
> The lower toroid is 160 only and the upper one is 80 meters only (with
> 10,15,20 and 40 coils added in of course).
>
> I’m using a shorting band switch 6 position.
>
>
> On 10 meters, the 160 meter toroid (lower one) gets so hot, the
> fiberglass tape has turned brown, and the Teflon wire is melting the
> Plexiglas that the toroid's are mounted on.
>
> I know all about trying to use a tapped toroid for multiple bands is
> wrong (except on the L coil of the Pi-L circuit, and see my postings about
> the Commander HF-2500 and K1TTT’s pictures of same) but WHY is the 160
> meter toroid getting so hot when using 10 meters? It's mounted very close
> to the loading vacuum capacitor is the only thing that I can think of. But
> the weird part, is that this just started. During all of the testing,
> there was no problem, but now, its really getting HOT!
>
> When testing, I had the top cover off of the amplifier, now that I’m
> using it, the top cover is on. I’m going to try the test again with the
> top off and see what happens.
>
> On 80 and 160 meters, the toroids are normal temperature (around 100
> degrees) and everything works just fine since I’m not shorting turns on
> the toroids.
>
> Ideas?
> Thanks and 73
> Jim W7RY
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>
>
> --
> Dan Hearn
> N5AR
>
>
>
>
> --
> Dan Hearn
> N5AR
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