Methylene chloride?
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> 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/162503185277?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D2%26asc%3D40130%26meid%3D0b6e78f2c5754c899998225e57dddd32%26pid%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.prod.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
>
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>
> End of Amps Digest, Vol 173, Issue 35
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