A hot solder pot and rosin flux has worked for me every time. Dip wire in
flux, dip wire end in the pot and wait 20 seconds. One of the little Chinese
pots that sell for $15.00 works fine. For the larger stuff I have a Plato pot.
Randy
-----Original Message-----
From: Amps [mailto:amps-bounces@contesting.com] On Behalf Of KA9EGW
Sent: Tuesday, May 16, 2017 3:59 PM
To: amps@contesting.com
Subject: [Amps] Stripping Litz
Methylene chloride?
Sent from my iPhone, still learning to use it
> On May 16, 2017, at 14:07, amps-request@contesting.com wrote:
>
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> Today's Topics:
>
> 1. Re: Real time tests to see if an RF transformer is
> saturating? (Chris Wilson)
> 2. Interesting new amplifier (Jim Thomson)
> 3. Re: Real time tests to see if an RF transformer is
> saturating? (Chris Wilson)
> 4. Re: Real time tests to see if an RF transformer is
> saturating? (Manfred Mornhinweg)
> 5. Re: Interesting new amplifier (Bill Turner)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Tue, 16 May 2017 17:29:15 +0100
> From: Chris Wilson <chris@chriswilson.tv>
> To: amps@contesting.com
> Subject: Re: [Amps] Real time tests to see if an RF transformer is
> saturating?
> Message-ID: <681889323.20170516172915@chriswilson.tv>
> Content-Type: text/plain; charset=iso-8859-1
>
>
>
> Hello Manfred,
>
> Tuesday, May 16, 2017
>
>
> What a totally awesome reply Manfred. I have read it several times and
> believe I fully understand the how and why of it all, so that equals a
> great explanation! I have ordered a couple of cores and 3 bobbins, so
> if disaster strikes I can try again. Could a similar arrangement be
> used for the output transformers of the amps themselves, which run
> warm, if not hot? I don't think I linked directly to the amp
> schematic, so here it is below. Quite how long it took you to do all
> the below i don't know, but obviously not a five minute job....
> Sincerest thanks for not only telling me how to further improve it,
> but also why and sharing your thinking as you approached the task!
>
> http://www.w1vd.com/137-500-KWTX.html
>
> and for completeness, this is the LPF I run after either a single amp,
> or the combiner
>
> http://www.w1vd.com/LPF.html
>
> Again, wonderful stuff, very helpful indeed!
>
>
>> Chris,
>
>> at that low frequency, indeed you can make the individual amps for
>> 100 ohm and put them in parallel, or for 25 ohm and put them in series.
>> There should be no phasing problems, at such a low frequency. But you
>> have to make sure that both amplifiers have extremely similar
>> responses, in terms of gain curve mainly.
>
>> The advantage of using a combiner is that it isolates one amp from
>> the other, so the system is highly tolerant to differences between
>> the individual amps, down to the point where one amp module can
>> completely fail, and the other will continue limping along. Without a
>> combiner, the failure of one module would probably cause the demise of the
>> other too.
>
>> I have been giving some thought to your transformer. First, I suggest
>> NOT buying that giant toroid. Bigger isn't always better. A huge core
>> has a lot of ferrite, that causes losses! That huge toroid has an
>> enormous space for winding, which you would never take advantage of.
>> A smaller core in a better design can provide far better performance.
>> So, let's start optimizing this design:
>
>> The first step is turning it into an autotransformer. The schematic
>> you linked shows a conventional transformer, with separate primary
>> and secondary, and both of them having one end grounded. That's very
>> inefficient! There is no reason at all to use separate primary and
>> secondary windings, if anyway they will be connected together! So,
>> for a start I would change this into an autotransformer: 7 turns
>> total, with a tap at 5 turns - or multiples of that, depending on the
>> core used. This eliminates 36% of the wire, and strongly improves
>> coupling, without any ill effect at all. Also transformer action is
>> now required for only 571W instead of the full 2000W, which allows
>> using a far smaller core, and far less total copper.
>
>> In that autotransformer, the current coming from your amplifier
>> enters the transformer through the tap, and splits in two parts:
>> 5/7ths of the current flows "up" through the 2 turns and into the
>> load, while 2/7ths flows "down" through the 5 turns and returns via
>> ground. The voltage applied to the 5 turns induces 2/5ths of that
>> voltage in the 2 turns. So the output voltage is 7/5ths of the input
>> voltage, while the output current is 5/7ths of the input current, the
>> transformer works at only 2/7ths of the total power (571W), and at
>> the output you still get the full 2000W.
>
>> There is an old adage: Engineering is a combination of material and
>> brains. The more you use of one, the less you need of the other.
>
>> Okay. Now lets try to come up with a good transformer for those 571W.
>> I will write here as I attempt to design it, so you can learn how to do it.
>
>> A good core shape is an RM or a pot core. They have bobbins (easy to
>> wind), round center legs (even more easy to wind), a much shorter
>> path length than a toroid, and they are available in suitable
>> materials. The catch is that they aren't very large. So, let's take
>> the largest RM core offered by FairRite, and see very dumbly how it works
>> out.
>
>> This core is available both in the 95 and the 98 materials. They are
>> quite similar, but I like 95 better because of its flatter loss
>> versus temperature curve. So, the chosen core would be the 6295420121.
>
>> First let's find out how many turns we need. 2000W on 50 ohm is 316V.
>> This core has a cross sectional area of 1.95cm?. Its volume is 14.36cm?.
>> How much power can we make it dissipate? That's a decision one has to
>> take. I would say, 2W is fine for continuous use, some more is
>> acceptable for intermittent use. So, at 2W to be on the safe side,
>> 139mW/cm? loss is acceptable. Looking at the material loss chart
>> given by Fair-Rite, an acceptable maximum flux density at 136kHz
>> seems to be 0.11T.
>
>> Now we can use equation 4 on my page
>
>> http://ludens.cl/Electron/Magnet.html
>
>> to calculate the required number of turns:
>
>> 316V /4.44 / .000195m? / 136000Hz / 0.11T = 24.4 turns
>
>> That's the minimal requirement. Since we need multiples of 7 turns,
>> let's use 28. So the recipe is 28 turns total, with a tap at 20 turns.
>
>> We don't need to make the 28 turns of the same wire, since the top 8
>> turns carry more than twice as much current as the lower 20 turns. To
>> evenly distribute losses, it's better to distribute copper
>> cross-section according to actual current flow.
>
>> Also it's hard or impossible to wind very thick, stiff wire on such a
>> bobbin, and on top of that thick wire suffers badly from skin effect.
>> It follows that you should wind this transformer with several strands
>> of thinner wire. That invites using a single size of wire, but using
>> more strands for the 8 turn winding than for the 20 turns.
>
>> For best coupling it would also be optimal to interleave primary and
>> secondary layers. In this case you could first wind a layer with 10
>> turns, then one layer with 8 turns, then a third layer with 10 turns,
>> and interconnect the three layers properly so that the 8 turn layer
>> ends up at one end of the other 20 turns. This scheme is still
>> reasonably easy to do, but doesn't allow us to use optimal copper
>> cross sections for each winding... Anyway, let's try a modification of it:
>
>> The winding space on the bobbin is roughly 18*8mm. We can start from
>> enamelled wire of roughly 0.7mm diameter (AWG #22), and wind 10 turns
>> with two strands side-by-side. That's a total width of 14mm, which
>> should fit in the 18mm bobbin space despite some slight kinks and
>> imprecisions. Try to keep the winding centered, leaving some empty
>> space at each side, because this reduces the risk of flashover between
>> layers.
>
>> Then wind two or three layers of Mylar or Kapton tape, cut just a tad
>> wider than the bobbin, so that it seals well against the bobbin sides.
>
>> Then comes the 8 turn winding. For simplicity let's use the same
>> wire, but 4 strands instead of 2. Wind 4 turns, with the 4 strands
>> nicely side-by-side. That will use up most of the bobbin width. Then
>> wind one or two layers of Mylar or Kapton tape, threading the four
>> wires through it, and then wind the other 4 turns. So this is a
>> double-layer winding, with both ends coming out of the bobbin on the same
>> side.
>
>> Now wind another two or three turns of Kapton or Mylar tape, and then
>> wind the topping layer of 10 turns of 2 strands of wire. Finish with
>> another few layers of tape.
>
>> The whole thing should be only around 5mm tall, fitting comfortably
>> in that bobbin.
>
>> Now the windings have to be interconnected. A lot of wires will be
>> sticking out of the bobbin... The two 10-turn windings have one end
>> on each side of the bobbin, while the 8-turn winding has both ends on
>> the same side. First thing is to take one end of one 10-turn winding,
>> and the opposite end of the other 10 turn winding, and join them.
>> This can be done on top of the Mylar tape, at a place of the bobbin
>> that will end up in one of the core's openings. Make the connection nice and
>> short.
>
>> Then the still free end of a 10-turn winding on the same side of the
>> bobbin where both 8-turn ends come out, has to be joined to the
>> CORRECT end of the 8 turn winding. The correct one is the ENDING, not
>> the BEGINNING, assuming that you wound everything in the same
>> direction. So, join that, fit the core (you can tape it together for
>> now, later glue or clamp it), and the transformer is ready for testing.
>
>> I would expect this to work pretty well, although it's not entirely
>> optimized. We could have used more strands of a thinner wire, and
>> interleave 3 primary with 2 secondary layers, for example. Anyway
>> it's MUCH better than winding separate primary and secondary on a
>> stack of large toroids, let alone a giant and non-optimally shaped toroid!
>
>> Manfred
>
>
>
>
>
>
> --
> Best regards,
> Chris mailto:chris@chriswilson.tv
>
>
>
> ------------------------------
>
> Message: 2
> Date: Tue, 16 May 2017 09:42:49 -0700
> From: "Jim Thomson" <jim.thom@telus.net>
> To: <amps@contesting.com>
> Subject: [Amps] Interesting new amplifier
> Message-ID: <B978198639414444A856D6929AD33FDC@JimPC>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Date: Tue, 16 May 2017 05:11:38 +0000
> From: Bill Turner <dezrat@outlook.com>
> To: Amps group <amps@contesting.com>
> Subject: [Amps] Interesting new amplifier
>
>
> <4Z4RB has been selling amplifier boards on eBay for some time, but I
> <see he now is selling a complete amp (less power supply) at a pretty
> <good price:
>
> http://www.ebay.com/itm/1500w-2-x-LDMOS-LINEAR-POWER-AMPLIFIER-LEGAL-LIMIT-/162503347501?
>
> <Obviously not FCC approved. I suspect he gets around that by
> claiming, <in effect, that it is homebrewed. Is that legal?
>
> <I sent him a message asking about duty cycle at full power and if a
> <manual can be downloaded. Waiting for reply.
>
> <Does anyone have any experience or comments about the amp or the
> <seller?
>
> <73, Bill W6WRT
>
> ## Looks like a bargain to me. He also makes a 1 kw amp with a single LDMOS
> device.... $1600.00 ( also less power supply).
> http://www.ebay.com/itm/BLF188XR-1kw-LINEAR-POWER-AMPLIFIER/1625031852
> 77?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.
> MBE%26ao%3D2%26asc%3D40130%26meid%3D0b6e78f2c5754c899998225e57dddd32%2
> 6pid%3D100005%26rk%3D5%26rkt%3D6%26sd%3D152536460986
>
> ## The 1.5 kw amp Bill mentioned above is $2400.00 ( less power supply).
> Both amps cover 1660-6m...and both contain 7 x LP filters. I dont see 30M
> band on either of them though.
>
> ## either of them can be driven with just 5 watts. He has a 5 / 50 input on
> the back, so a 10 db attenuator can be switched in for your typ 100w xcvr.
> ## he also offers an optional vac relay. Rated for AM, FM, SSB, CW. No
> mention of duty cycle or imd etc.
> I nominate Bill to race out and buy one, then evaluate it for the rest of us.
>
> Jim VE7RF
>
>
>
>
>
> ------------------------------
>
> Message: 3
> Date: Tue, 16 May 2017 18:09:35 +0100
> From: Chris Wilson <chris@chriswilson.tv>
> To: amps@contesting.com
> Subject: Re: [Amps] Real time tests to see if an RF transformer is
> saturating?
> Message-ID: <1310166509.20170516180935@chriswilson.tv>
> Content-Type: text/plain; charset=us-ascii
>
>
>
> Hello Roger,
>
>
> I have some fairly heavy fabric covered Litz wire, but stripping the
> enamel is proving a nightmare. It's old, pre 1960's i think, and a
> solder pot doesn't do the trick. Nitromors paint stripper works, but
> takes hours if not days, and you have to tease the paint stripper
> through all the strands to clean them. Doing loads of ends would be a
> daunting task. I acquired it from an acquaintance who got similarly
> fed up with trying to tin it and let me have a go. I got a little
> further but it was still a fool's errand messing with it. A shame as
> it would probably be ideal for this... Thanks for the tip!
>
>> On Tuesday, May 16, 2017, you wrote:
>>
>> If you can find it, you're better off using Litz wire.
>
>> 73, Roger
>
>
>
>
>
>
> --
> Best regards,
> Chris mailto:chris@chriswilson.tv
>
>
>
> ------------------------------
>
> Message: 4
> Date: Tue, 16 May 2017 18:25:40 +0000
> From: Manfred Mornhinweg <manfred@ludens.cl>
> To: amps@contesting.com
> Subject: Re: [Amps] Real time tests to see if an RF transformer is
> saturating?
> Message-ID: <591B4424.6090304@ludens.cl>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Chris,
>
>> I stacked 3 off 78 material cores in the same size as the 77 material
>> toroids and wound them with 180 strand speaker wire with a conductor
>> diameter of about 2mm.
>
> This sounds like you misunderstood one thing: That speaker wire surely
> has no insulation between the individual strands, and so it will
> behave exactly like a solid wire, in terms of RF performance. To
> achieve an improvement over solid wire you need to have INSULATED
> strands! And ideally they should be woven in a very specific way, so
> that each strand is on the surface and inside the bundle as much as any other
> strands.
> The Litz wire suggested by Roger is exactly what you want, but it's
> relatively rare and expensive. What's typically done is assembling a
> bundle from many thin enameled wires, or winding with several enameled
> wires in parallel.
>
> Manfred
>
> ========================
> Visit my hobby homepage!
> http://ludens.cl
> ========================
>
>
> ------------------------------
>
> Message: 5
> Date: Tue, 16 May 2017 19:07:31 +0000
> From: Bill Turner <dezrat@outlook.com>
> To: Amps group <amps@contesting.com>
> Subject: Re: [Amps] Interesting new amplifier
> Message-ID:
>
> <CY1PR0301MB1196C0B24289A602312632CEC0E60@CY1PR0301MB1196.namprd03.pro
> d.outlook.com>
>
> Content-Type: text/plain; charset="us-ascii"
>
> ------------ ORIGINAL MESSAGE ------------(may be snipped)
>
>> On Tue, 16 May 2017 09:42:49 -0700, you wrote:
>>
>> I nominate Bill to race out and buy one, then evaluate it for the rest of us.
>>
>> Jim VE7RF
>>
>
> REPLY:
>
> Bill is indeed tempted.
>
> 73, Bill W6WRT
>
>
> ------------------------------
>
> Subject: Digest Footer
>
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>
>
> ------------------------------
>
> End of Amps Digest, Vol 173, Issue 35
> *************************************
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