From Newsgroup: sci.electronics.repair
On Thu, 19 Jun 2025 19:15:28 -0700, Jeff Liebermann <
jeffl@cruzio.com>
wrote:
On Thu, 19 Jun 2025 14:00:31 +0100, Cursitor Doom <cd@notformail.com>
wrote:
On Wed, 18 Jun 2025 18:03:03 -0700, Jeff Liebermann <jeffl@cruzio.com> >>wrote:
On Wed, 18 Jun 2025 18:04:29 +0100, Cursitor Doom <cd@notformail.com> >>>wrote:
Gentlemen,
Many of us are familiar with the all-too-common problem of reciever >>>>re-alignment. Dealing the vintage radios with fragile ferite cores in >>>>their IF stages is unavoidable and can prove to be a major PITA. The >>>>cores are brittle and eager to shatter at anything much above mm/mg >>>>torque levels. The key is to use a tool which is not only non-metallic >>>>but also a perfect fit for the slot it must engage with in the top of >>>>the core. Given the range of sizes one encounters in this concern,
it's often necessary to 'roll your own' tool. Well I have a suggestion >>>>to make. Wood makes the best tool for this job and opinions vary as to >>>>which particular wood is ideally suited to this task. Lemon and orange >>>>are often cited. But they're expensive and hard to source typically. >>>>However, I've found a marvellous alternative: yellow heart. I don't >>>>know what the technical name is for this wood, but that's what it's >>>>informally called. It's cheaper and more readily obtainable than
orange or lemon and AFAIC, *better* than either with it's incredibly >>>>fine grain and viceral hardness. It files and sands readily and when >>>>dipped in cellulose sealer, will not fray in use.
Just thought I'd share that with you guys.
CD.
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)
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.
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.
<https://www.reddit.com/r/boatbuilding/comments/hhaujy/why_does_planking_end_just_behind_the_bow/>
"This affirms the wooden boat builders trick of sealing the plank ends
with glue, even the staunch traditionalist will put glue on the end of
the planks."
frequencies. This is about half of the tuning tools I've accumulated >>>over the years:
<https://photos.app.goo.gl/7Gq4r85pipeccUMz9>
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. >>><https://www.ortechceramics.com/products/ceramic-tubes-rods/ceramic-rod/> >>>
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.
Certainly won't ifyou use wood either.
Huh? I suggest you use some kind of ceramic or plastic, unless you
enjoy research projects.
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. LetAs
dissect this claim about wooden tuning sticks and water in the xylem
causing issues at VHF frequencies. IAll 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 GuyAs Claim
The internet guyAs argument is that woodAs natural
structureuspecifically the xylem, which transports water in living
treesumakes 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 30u300 MHz) due to
waterAs dielectric properties. He describes trees as obundles of soda
strawso (xylem vessels) that continue to move water via capillary
action, implying that wooden tuning sticks might retain enough
moisture to mess with a tuned circuitAs frequency when inserted into a
coilAs former.
Breaking It Down
LetAs analyze his points in the context of your tuning sticks and
tuned circuits:
WoodAs Water Transport in Living Trees:
HeAs 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 osoda strawso
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, isnAt
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 thereAs 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 ingressuboth on
the sides and ends, since the sealer forms a barrier. The guyAs
concern about water movement in cut wood is overstated for properly
processed and sealed wood.
WaterAs Impact at VHF Frequencies:
He argues that the osmall amount of water in the xylem will be noticeable at VHF frequencies.o 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 coilAs former, potentially shifting the resonant frequency.
Does This Hold Up?: At VHF (30u300 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 6u12%
moisture content) has a dielectric constant of 2u5, close to that of
plastic (2u4).
WaterAs 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 woodAs dielectric properties stable.
In practical terms, inserting a dry, sealed wooden tuning
stick into a coilAs 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 doesnAt explicitly say plastic or ceramic are better
here, but since you mentioned he prefers them, letAs revisit:
Plastic: Has a dielectric constant similar to dry wood
(~2u4) and no moisture issues, so itAs 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 (~5u10), which
could actually cause a larger capacitance shift than wood in some
cases, but high-quality ceramic tools are designed to minimize this.
TheyAre stable but not inherently obettero for all VHF tuning.
Both materials are non-inductive like wood, so none of
them affect the coilAs inductance. The guyAs focus on water in wood
seems to overemphasize a minor issue while ignoring that plastic and
ceramic arenAt perfect either.
My Take
The internet guyAs got a point about living trees and water transport,
but heAs stretching it to dried, processed wood in a way that doesnAt
hold up for your tuning sticks. HereAs the deal:
Your Paulownia Sticks: Properly dried and sealed with cellulose
sanding sealer, theyAre as good as plastic for most tuning tasks,
including VHF. The residual moisture in sealed wood is so low it wonAt
cause noticeable frequency shifts in practical scenarios. The osoda
strawso analogy is irrelevant once the wood is dried and sealed, as
itAs 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 MHzu3 GHz) or microwave frequencies, his concern
might have more weight, but even then, sealed wood is fine for most
hobbyist applications.
Internet GuyAs Exaggeration: HeAs 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 youAre working in a super humid environment or
hyper-precise VHF/UHF circuits, you could test plastic sticks for
peace of mind, but thereAs no evidence woodAs failing you. CeramicAs
overkill unless youAre 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 youAve got one). I bet youAll 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 youAre going pro.
Final Verdict
The guyAs claim is technically grounded but overblown. Your sealed
Paulownia sticks are just as good as plastic or ceramic for practical
tuning, even at VHF. HeAs worrying about a non-issue for your use
case. Keep rocking those sticksuyouAre 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.
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