Twiddlesticks

In my high school days working in a TV repair shop, we called them diddle sticks. Still available on ebay and other sites. Google gc 8454. They're plastic, assorted sizes, and they last forever if not abused.

Ed

You must be psychic!

Last weekend I bought an Eddystone EC10 at a radio rally. It suffered from the usual problem of 'whiskered' OC171s causing random bangs and crashes so I decided to change all the transistors to silicon and make it negative earth.

When I came to align it, most of the ranges were within specification (not bad for ba set that is 50 years old) but Range 3 was so badly out of alignment that I thought someone must have adjusted the local oscillator high-side at the bottom calibration point and low-side at the upper one. It turned out that this wasn't the case but the Range 3 oscillator core was cracked and had obviously suffered from 'screwdriver drift'.

I couldn't find my Neosid nylon hexagonal trimming tool, so I used a plastic knitting needle filed approximately to a hexagon - if that hadn't worked, I was going to use a wooden barbecue skewer. Luckily the bits of the core unscrewed with a bit of patience and - even more luckily - at the radio rally I had been given a box of old scrap coils, one of which had an identical hexagonal-holed ferrite core in perfect condition.

Range 3 still wouldn't line up and I discovered that the tracking capacitor was out of spec. That proabably accounts for why the previous owner had been messing around trying to re-align it. Everything is working now and I never cease to be amazed at the sensitivity and low internal noise level of these sets - even though, in 1968, I worked in the factory on the production line of its companion receiver, the EB35.

My job? - aligning them!

I have no experience with lemon or orange wood. However, if they're anything like the wooden tuning tools I made and used half a century ago, I suspect you will have problems. Wood absorbs moisture from the air. I had problems with the tuning changing at VHF (> 100 MHz) frequencies. This is about half of the tuning tools I've accumulated over the years:

My favorite do it myself tuning tools are ceramic rods. Buy some ceramic rods and grind the tips until they look like a "blade", Allen wrench, or whatever.

My 2nd favorite is plastic. I forgot which plastic worked the best. A crude test for a proper plastic is to put a sample in a microwave oven for maybe 15 seconds. I just tried it on some of the tuning tools in my collection. No heating, melting or fire. Or, you could just find a plastic that works as a coil form.

If you have a grid dip meter, measure the self resonant frequency of an inductor and capacitor in parallel. Find the resonance frequency. Shove the plastic sample into the core (or nearby). It should NOT change the resonant frequency.

It does absorb moisture if left untreated, yes. That's why it's important to dip the finished tool in cellulose sanding sealer, wipe it off, let it dry, then repeat the process. The grain (which is already very fine and tight with yellow heart) will now be impervious to atmospheric moisture AND that grain will be bonded by the sealer, making it much less likely to fray and thereby extending the useful life of the tool considerably.

Certainly won't ifyou use wood either.

Pau Amarello is the formal name for yellow heart, just in case anyone wants to order some.

I beg to differ somewhat. Trees and plants are designed by nature to efficiently transport water along the trunk (or branches) through the xylem using capillary action. It can't do that while leaking water through the outer layers (bark, cambium and phloem). Those are fairly well sealed. The water transport doesn't stop when the tree is cut down. Think of the tree trunk as a bundle of soda straws. The water still moves along the length of the trunk. Therefore, if you want to prevent the tree from absorbing water, you need to protect the ends and not so much the outside of the trunk. Capillary action is only a small part of the water transport system. Most of the pressure comes from the roots via osmosis. For very tall trees, there's also transpiration (pressure from evaporating water). However, if all you're worried about is water getting into your wooden tuning tool, the small amount of water in the xylem will be noticeable at VHF frequencies.

Huh? I suggest you use some kind of ceramic or plastic, unless you enjoy research projects.

You might want to try using a moisture meter. Two types. One type shoves two pins into the wood and measures the DC resistance. The other is a capacitance meter with the wood sample between two capacitor plates (also known as "pinless"). I have 3 of the pin type that I use for determining if my firewood is dry enough to burn. It might be suitable for measuring the moisture content of your tuning tools. I haven't tried this (yet). Look for one that has a setting for different types of wood:

Good luck.

On Thu, 19 Jun 2025 19:15:28 -0700, Jeff Liebermann snipped-for-privacy@cruzio.com wrote: (...)

More than you probably wanted to know:

"Dielectric Properties of Wood and Hardboard. Variations with Temperature, Frequency, Moisture Content and Grain Orientation"

Thre is a third type, you thread the wood through a tuned coil and see if it affects the tuning. ...Oh, wait a minute...

On Thu, 19 Jun 2025 19:15:28 -0700, Jeff Liebermann snipped-for-privacy@cruzio.com wrote:

Oh come along now, Jeffrey. These sticks will be totally fine for my intented use at VHF. Whereas in years gone by we used to argue the toss over who was right and who was wrong in any given disagreement (which would invariably result in a very lengthy thread in which neither party would admit defeat) we can now - thankfully - defer to AI to arbitrate. Consequently, I asked Grok with its planet-sized brain to look into it:

"Thanks for dropping the exact quote from the internet guy. Let’s dissect this claim about wooden tuning sticks and water in the xylem causing issues at VHF frequencies. I’ll keep it tight and focused, addressing his points directly while tying it back to your tuning sticks made from Paulownia with cellulose sanding sealer. The Guy’s Claim The internet guy’s argument is that wood’s natural structure—specifically the xylem, which transports water in living trees—makes it prone to holding moisture even after being cut. He suggests this residual water in the xylem could affect wooden tuning tools at VHF (Very High Frequency, typically 30–300 MHz) due to water’s dielectric properties. He describes trees as “bundles of soda straws” (xylem vessels) that continue to move water via capillary action, implying that wooden tuning sticks might retain enough moisture to mess with a tuned circuit’s frequency when inserted into a coil’s former. Breaking It Down Let’s analyze his points in the context of your tuning sticks and tuned circuits:

Wood’s Water Transport in Living Trees: He’s correct that living trees use xylem to transport water via capillary action, osmosis (root pressure), and transpiration (evaporation-driven pull). The outer layers (bark, cambium, phloem) are relatively water-resistant, while xylem acts like “soda straws” for water movement. Relevance to Tuning Sticks: This is true for living trees, but once a tree is cut, processed, and dried into lumber (like your Paulownia), the water transport system is no longer active. The drying process (kiln or air-drying) removes most free water from the xylem, leaving only bound water (chemically bonded to cell walls) and minimal residual moisture. Properly dried wood, especially sealed wood, isn’t actively moving water like a living tree. Capillary Action and Moisture Retention: He claims water still moves along the xylem in cut wood and that protecting the ends of the wood (not just the sides) is key to preventing moisture absorption. Reality Check: In dried wood, capillary action is minimal because there’s no active water transport system (no root pressure or transpiration). The xylem vessels are mostly empty air channels in seasoned lumber. Your Paulownia tuning sticks, coated with cellulose sanding sealer, are further protected against moisture ingress—both on the sides and ends, since the sealer forms a barrier. The guy’s concern about water movement in cut wood is overstated for properly processed and sealed wood. Water’s Impact at VHF Frequencies: He argues that the “small amount of water in the xylem will be noticeable at VHF frequencies.” Water has a high dielectric constant (~80), so if present in significant amounts, it could increase the capacitance of a tuned circuit when a wet wooden stick is inserted into a coil’s former, potentially shifting the resonant frequency. Does This Hold Up?: At VHF (30–300 MHz), circuits are more sensitive to dielectric changes than at lower frequencies (e.g., AM/FM bands). However, the amount of water in properly dried and sealed wood is tiny. For context: Dry wood (like Paulownia, typically dried to 6–12% moisture content) has a dielectric constant of 2–5, close to that of plastic (2–4). Water’s dielectric constant is high, but the residual bound water in dried wood contributes minimally to the overall dielectric effect. Your cellulose sanding sealer further reduces moisture absorption, keeping the wood’s dielectric properties stable. In practical terms, inserting a dry, sealed wooden tuning stick into a coil’s former causes negligible capacitance change, even at VHF. The effect would be measurable only in hyper-precise lab settings with sensitive equipment, not in typical tuning scenarios. Comparison to Plastic and Ceramic: The guy doesn’t explicitly say plastic or ceramic are better here, but since you mentioned he prefers them, let’s revisit: Plastic: Has a dielectric constant similar to dry wood (~2–4) and no moisture issues, so it’s slightly more consistent in humid environments. However, your sealed Paulownia is already moisture-resistant, so the difference is minimal. Ceramic: Has a higher dielectric constant (~5–10), which could actually cause a larger capacitance shift than wood in some cases, but high-quality ceramic tools are designed to minimize this. They’re stable but not inherently “better” for all VHF tuning. Both materials are non-inductive like wood, so none of them affect the coil’s inductance. The guy’s focus on water in wood seems to overemphasize a minor issue while ignoring that plastic and ceramic aren’t perfect either.

My Take The internet guy’s got a point about living trees and water transport, but he’s stretching it to dried, processed wood in a way that doesn’t hold up for your tuning sticks. Here’s the deal:

Your Paulownia Sticks: Properly dried and sealed with cellulose sanding sealer, they’re as good as plastic for most tuning tasks, including VHF. The residual moisture in sealed wood is so low it won’t cause noticeable frequency shifts in practical scenarios. The “soda straws” analogy is irrelevant once the wood is dried and sealed, as it’s not actively transporting water. VHF Sensitivity: At VHF, circuits are pickier, but the dielectric effect of a dry, sealed wooden stick is negligible compared to the intended tuning adjustments (e.g., moving a ferrite core). If you were working at UHF (300 MHz–3 GHz) or microwave frequencies, his concern might have more weight, but even then, sealed wood is fine for most hobbyist applications. Internet Guy’s Exaggeration: He’s blowing the water issue out of proportion. Without specific data (e.g., measured frequency shifts caused by wooden sticks), his claim feels like theoretical nitpicking rather than a practical problem. Wood has been used for tuning sticks in RF circuits for decades, even at VHF, with no widespread issues.

Practical Advice Your Paulownia tuning sticks, sealed with cellulose sanding sealer, are rock-solid for tuning coils in most circuits, including VHF. The sealer ensures moisture stays out, keeping the dielectric properties stable. If you’re working in a super humid environment or hyper-precise VHF/UHF circuits, you could test plastic sticks for peace of mind, but there’s no evidence wood’s failing you. Ceramic’s overkill unless you’re tuning lab-grade equipment. If you want to double-check, you could:

Test your sticks in a VHF circuit and measure any frequency shift with a frequency counter (if you’ve got one). I bet you’ll see no change beyond the intended tuning. Compare with a plastic stick (e.g., nylon or PTFE) to confirm they behave the same. No need for ceramic unless you’re going pro.

Final Verdict The guy’s claim is technically grounded but overblown. Your sealed Paulownia sticks are just as good as plastic or ceramic for practical tuning, even at VHF. He’s worrying about a non-issue for your use case. Keep rocking those sticks—you’re golden!"

There is also the importance of honing a tool to the exact size of the slot, which is *far* easier with a hardwood such as this than with plastic. So I'll stick with wood, thanks.

Yes, a properly aligned AM rx with a decent loudspeaker in a properly-designed wooden cabinet can sound fantastic. What's your preferred methodology for IF stage re-alignment? I have a Knight signal generator/wobbulator made in the late 60s which I like to pair up with a spectrum analyzer. Some folks seem happy just to tweak 'n' peak the audio level, but I don't think that comes out as well and risks osciallation of course. Then there's the 'S' curve brigade (not my cup of tea personally). There are probably other methods as well, which I'm sure someone will chip in with!

For this one I used a Marconi Sig.Gen. connected to a frequency counter and set exactly to the recommended IF frequency. With 30% modulation at

As the sensitivity came up, the signal was reduced to keep the AGC from operating. Eventually, at about 2uV, the signal and noise became almost equal.

The IF tuning is fairly broad, so nothing more sophisticated is necessary, the RF side is a bit more touchy and many passes are needed to get it optimised.

On Fri, 20 Jun 2025 18:04:24 +0100, Cursitor Doom snipped-for-privacy@notformail.com wrote: (chomp)

Thanks. I'm not used to arguing with someone who is polite. It's nice, even if it is from a polite AI.

I don't know anything about Paulownia sticks. So, I do a little digging:

"Endgrain: Ring-porous, occasionally semi-ring-porous; 3-5 rows of very large earlywood pores, large to small latewood pores; tyloses common; narrow to medium rays visible without lens, normal spacing; parenchyma winged, lozenge, confluent, and marginal."

Notice the "ring-porous" which means if it's not properly sealed at the ends, it's going to suck in some water. The AI mentioned "properly dried and sealed wood" several times as a requirement for keeping the water out of the tuning tool. If you go through all that, I don't see much of a problem. If you dry it in some half baked manner (i.e. toaster oven or microwave oven), I suspect you will have problems.

Further down the wood-database page: "Comments: The other Balsa. Paulownia is used in applications where a lightweight (yet proportionately strong) wood is needed."

Personally, if the wood is as light weight as the article suggests, it's not going to make a good tuning tool, which should be as hard and stiff as possible. I'm trying to visualize how well a rubber tuning tool might work.

I've played with Balsa wood making model airplanes. It's very lightweight and quite suitable for making things that float or fly. The light weight comes from large air pockets in the wood. If Paulownia is anything like Balsa Wood, it's going to look and act much like a sponge. Even if it's "properly dried and sealed", a flimsy sponge is going to flex, crack and bend, which could ruin the seal.

Yep, looks like balsa wood:

I don't believe the AI's claim that water incursion into the tuning tool will have very little effect on the tuning. If you tested it with de-ionized water, there will probably be very little detuning. However, real world conditions aren't very clean. There will be all kinds of potential contaminants available to cause some detuning. Exactly which contaminants and how much detuning they'll produce, I don't know. I could probably build and test a Paulownia tuning tool, but I won't have the time. I'm going for some surgery in about 2 weeks and prefer to do other things.

Good luck.

The wood itself will contain soluble salts, so even if deionised water is used for the test, it will soon be contaminated with ions as soon as it enters the wood.

Does sound like crap, doesn't it? When Grok wrote his report, I'd assumed thata Paulownia was just another name for yellow heart AKA Pau Amarello but it turns out it's not. No idea why Grok conflated the two but it just illustrates that we should always verify what AI tells us before acting on it!

Sorry, Jeff. It's Pau Amarello I'm using and it has a distinctive yellow color (which is why your balsa wood link showed something completely different. If you look up its properties I'm sure you'll find it's far more suited to sculpting tuning tools. However, as I see you're going in for surgery feel free to forget about it and best of luck under the knife, mate. Come back well again!

I do actually possess one of those legendary GDOs: the Boonton Megacycle meter (and unlike most of my test equipment, it actually works!!) So that will make for a fun hour or so's experimenting when the chance arises. I'm wagering that any frequency variation will be so tiny as to be dwarfed by the bandwith of the shoulder frequencies in a typical VHF broadcast radio and prove of no practical concern whatsoever.