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Continuity on #RWTST -
#RWTST
#QMXplus
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I managed to get through the steps to build the RWTST version of the transformer. I'm getting caught up on Step 14:
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I have continuity between the secondaries. I also have continuity between the primary center tap and each of the two primary points on the left side. I do not have continuity between the two P points on the left side (i.e., the wires that were part of the hairpin loop before I cut it). Am I supposed to? Based on the wording in the instructions ("points P (P is for primary) should all show continuity to each other"), I assumed that I should have continuity between the two P points on the left side.
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Separately, do I understand correctly that the tighter the wire is twisted, the closer I will get to optimum power? I was able to twist them quite tightly, but it made them brittle for completing the coil. I tried again with fresh wire but I'm concerned that it's not tight enough.
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Thanks!
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Hi. You are logically inconsistent.? If I have 3 points A,B,C and A connects to C, and B connects to C, then A and B MUST show continuity to each other. I suggest you check your measurements.
73
Roger
8P6RX
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On 25 Mar 2025, at 11:00, "avinoam83 via " <gmail.com@groups.io target=_blank>[email protected]> wrote:
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If you didn't scrape the enamel off the newly-twisted 'A' center tap on the right side, those two wires won't contact each other, and you won't have continuity between the two left 'A' points - even if you scraped the enamel off the outside of the twist.
If you have the finer-gauge wire, you can burn the rest of the enamel off with solder and a hot soldering iron, if you have the thicker .6 wire, you need to un-twist the A center tap and scrape the wires first, then twist.
Stan |
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Unless you are using some exotic insulated wire, a few
seconds of exposure to the flame of a butane lighter will easily burn off the enamel. After you have done that, there will be a little oxide and smutz on the wires, so a gentle pull through a folded piece of sand paper will clean that right off. Way easier than scraping, or sanding the insulation off. -Chuck Harris, WA3UQV On Tue, 25 Mar 2025 08:31:25 -0700 "Stan Dye via groups.io" <standye@...> wrote: If you didn't scrape the enamel off the newly-twisted 'A' center tap |
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On Tue, Mar 25, 2025 at 08:57 AM, Chuck Harris wrote:
Unless you are using some exotic insulated wire, a few My experience is different, Chuck.? A simple roll of wire (certainly not exotic) I bought on Amazon from a quality manufacturer happens to have a high-temperature enamel.? So yes, I can burn it off, but only with with a high-temperature butane torch, but not a simple butane lighter flame nor any soldering temperatures.
Other wire types do have enamel that is specially formulated to burn off with solder or at low temperatures - you can often see it in their specs.
The .6 wire that Hans originally provided is somewhere between the two - if I didn't scrape it at least some amount, to significantly fracture its surface, it wouldn't burn off for me with soldering nor a simple lighter flame.? And I don't like to use a high-temperature torch.
Stan KC7XE. |
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You're referring to the leads on the right (primary center tap), correct? If so, I did that, which I believe is how I'm getting continuity from left to right. However, I'm going to apply some solder to the twist in order to make sure that I'm not getting a false positive by touching one lead or the other. Thanks!
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On Tue, Mar 25, 2025 at 08:04 AM, <john.runchey@...> wrote:
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K used a lighter and tried scraping as well. I'm going to try with some hot solder. Thanks!?
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On Tue, Mar 25, 2025 at 08:57 AM, Chuck Harris wrote:
Unless you are using some exotic insulated wire, a few |
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I used two different wires - The one that Hans provided and this one: . I did that in order to maintain color coding for the P and S wires. The P wire is the Amazon wire. At the very least, I seem to have cleared enough enamel to establish continuity between the center tap and the P on the other side. I'm going to try some more when I get home. Here is what I have:
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On Tue, Mar 25, 2025 at 09:10 AM, Stan Dye wrote:
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I would guess that 100% of the QRP Labs kits are shipped
with some manufacturer's thermaleze equivalent wire. I would further guess that a very, very small contingent in this group would use their own wire over the wire provided by QRP Labs with their kits... I am one of that contingent, but only because I use a toroid winding machine, and filling my winding machine's shuttle from short hanks of wire is a chore. But you are right, if you use something exotic, such as a ceramic insulated wire, my tip about using a common lighter won't work. You may not know it, so I will help you: You are using an exotic wire. I will jump out on a limb and say that most QRP Labs kit builders, aren't. -Chuck Harris, WA3UQV On Tue, 25 Mar 2025 09:10:42 -0700 "Stan Dye via groups.io" <standye@...> wrote: On Tue, Mar 25, 2025 at 08:57 AM, Chuck Harris wrote:My experience is different, Chuck.? A simple roll of wire (certainly |
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I've just started building my QMX+ kit and what I found was that I needed an indicated temperature of 440C to burn the enamel off. My normal 380C barely touched it.? I'm using a WEP 926 LED soldering station.? I'd like to use a little less and will be experimenting as the toroid saga continues.
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FTAOD this is with the 0.33mm wire supplied in the kit.
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HTH
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Chris, G5CTH |
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I’ve been using my Weller WSD81 station set at 375C and a 1.6mm chisel bit with great success.
I've built quite a few QRP Labs kit, with last week a QMX+ and a QMX 20-10. On previous builds I’ve had to scrape the 0.6mm wire, heating just wasn’t good enough. But with the 0.33mm was easy.
What I found was the best way was to cut the wire a bit shorter, perhaps 6mm in excess of what’s needed to go into the pcb, then start the iron right on the cut end where the copper is exposed. Then work the solder blob up to the desired place. This works much better and faster than trying to burn the enamel mid way. |
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FTAOD seems to be a legalese thing, had to look it up.
Took me some time to find that on the web.
A slight misspelling on my part brought up lots of very cute images of amphibians, which distracted me from my initial purpose.
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Perhaps it is best understood by reading it in proper context, as written by a professional.
Here's an example of how it should be used, from ?
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"For the avoidance of doubt, this paragraph is intended to, shall be??to and,??does?avoid any and all doubt??provided that it shall not be deemed to, and shall accordingly not, amend, alter or affect the foregoing passage, which passage does not, for the avoidance of doubt and notwithstanding this present clarification as it may,??be amended updated or clarified, introduce any doubt, (other than, for the avoidance of doubt, those previously-identified doubts as may have been conclusively eliminated by the doubt-avoiding effect of this present clarification)."
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TLDR:? FTAOD="To be clear,"
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Jerry, KE7ER
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On Wed, Mar 26, 2025 at 01:57 AM, Chris wrote:
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On Tue, Mar 25, 2025 at 09:11 PM, Chuck Harris wrote:
if you use something exotic, such as aPlease avoid using personal attacks, Chuck.? Some facts:
1- I can assure you again that I am not using exotic wire.
It is this:
It turns out that you can buy inexpensive wire that has has high temperature enamel.? It is made for motor windings.
It certainly is not ideal for winding toroids for qrp.? And the enamel will NOT burn off with a simple lighter.? Get some. Try it. Or not. But I have it, and I have used it for winding toroids for ATU kits and transformers. ?
2- I do use the kit wire supplied by qrp-labs for my qrp-labs kits.? The smaller diameter wire provided will indeed burn off with soldering or a lighter - it is of a thermaleze type.
3- For the older kits with the .6mm wire, here is a quote from Hans' transformer winding doc: "If using 0.60mm wire, scrape the wire enamel from this 1cm section. The enamel on the 0.60mm wire will be very difficult to remove using heat; so it is better to scrape it or sand it."?
4- I agree with Hans.? I don't think that wire had a thermaleze type insulation, either.
5- I, too, have recently retired from a 40+ year career of electrical engineering design/build/test.? I'm not an expert with RF circuits, but I do know my wire and how to use it.
Stan KC7XE
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Stan,
I scoured my post for a personal attack, and could not find one. Motor wire is an exotic wire when used in a QRP radio kit. Compact, intermittent duty, motors quite often are built to withstand short term very hot operation... often thermally stressing even 200C rated wire. These kits are low temperature, low power radios, that come provisioned with a thermal stripping wire, equivalent to thermaleze. A large quantity (2x the total amount required) of the desired wire was included with each kit. Easily enough to cover the occasional oops an inexperienced builder may encounter. Your use of high temperature motor wire, to replace the wire that comes with these kits, makes your choice an outlier for the overwhelming majority of builders of these kits. It appears to me that its principal benefit is that *you* had it on hand. An inexperienced builder will find it challenging to use a knife to completely strip a #28AWG wire without damaging, or incompletely stripping, the wire. I find that most inexperienced craftsmen greatly over estimate the forces required to do fine operations. They also greatly underestimate the time required to do fine operations properly. Either can cause disappointing results. Sanding off wire insulation has its own difficulties. Most high temperature motor wire insulation is also designed to protect against abrasion... which is exactly what you are trying to do when you sand or scrape the insulation off of the wire. The insulation is almost always tougher than the copper wire itself, causing the side where you first break through to the copper to get sanded much more quickly than the rest of the wire. By the time your are done, the wire will be in the shape of a flat oval. If everyone was using, or could be reasonably expected to be using, high temperature, non-thermal stripping wire on their kits, then your advice would be spot on. I believe they are not, but are rather seeing the heat sinking effect of the large continuous ground planes needed for high quality RF work. Through the use of poor technique, or perhaps ineffective soldering equipment, they are not getting enough heat into the joint to melt (not burn) the usually easy to strip thermaleze style wire. A simple match, or a lighter, to pre-strip the wire will help with that job, and not put the wire at much risk. -Chuck Harris, WA3UQV On Wed, 26 Mar 2025 09:52:57 -0700 "Stan Dye via groups.io" <standye@...> wrote: On Tue, Mar 25, 2025 at 09:11 PM, Chuck Harris wrote:Please avoid using personal attacks, Chuck. |
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