|Testing Toroid cores for AMATEUR RADIO PROJECTS..Basic measurements and comparision to "charts"..in
particular concerning Ferrite material which has a wide variance of inductance vs. number of turns..ie type 43 and
61 material compared.
note: it is not possible to distinguish these cores apart unless you make a test winding and measure the inductance
. I tried measuring the resistance across the cores both -43 and -61 and I did not get a resistance measurement.
They both look alike.
May 2, 2012..I did a test winding on some FT50-61s and FT50-43s today on the bench. I used a short length of wire
for about 2.5 turns with 3/4 inch tag ends. The FT50-61s all measured about .67 uh to almost .7 uh. The FT50-43s
measured (approximately) 2.4 uh (by comparision.
|The L and C meter I am using now is one I
bought from ebay and overseas from the
IT gives definite measurements to a number
of decimal points.
I dont know just how absolutely accurate it is
because I have no known standard to use for
It seems to work quite well. For a six turn
wire length on an FT37-61 toroid..the chart
told me to expect
1.99 uh inductance. The meter read 1.965
uh..as per the picture below.
So I am a happy camper and Im quite
confident in this batch of toroids. I will
measure a few others from the bag..but I
expect no problems.
I might try and develop a faster method.
Maybe a 2 turn test would give a good
enough approximation to ensure complete
confidence in the cores.
THE CHART I AM USING HERE IS ONLY FOR
-43 AND -61 ferrite.
These are the most popular mixes of ferrite
but amateur radio projects do call for other
mixes and I have small quantities of other
mixes in my collection.
I will find other charts for these mixes as well.
IF you wish to order some cores from me for
a project..I can supply small numbers in a
padded envelope for low postage rates.
About $1.40 in Canada and a bit more
stateside and a bit more still internationally.
Toroids are subject to fracture and I have to
wrap them well certain sizes (ie the larger
sizes) tend to fracture.
Larger sized toroids like the larger than 1
inch diameter sizes may have to be shipped
in a box rather than padded envelope and
the postage charge goes up significantly in
I "spot check" the cores I buy from the
common suppliers..just to be sure they are
as labelled. Here I check a batch with my
"chinese ebay L/C meter" They test pretty
close to what the Chart says they should be.
|I printed this chart from the Kits and
Parts dot com web site. I compared it to
another chart by a well known qrper
WA8MCQ..both these charts can be easily
found by web search and they seem to
be the same. I did not find a chart for the
-77 material and some of the other less
common values I have around. Perhaps I
will have to resort to math and use the
amidon chart I have to calculate
according to the Al values.
The two types of toroids I am measuring
today are the 43 mix and the 61 mix.
Both materials look identical. I doubt you
could tell the difference between them
I tried measuring the resistance across
the cores to see if that would give any
clues..but I did not get any stable
|TWO different cores both claiming to be -43 material. NOTE there is a slight difference in the measurements. The chart calls for 15.1 uh for 6 turns.
I did not absolutely and carefully wind these coils. I wound them with "about" the same amount of (TAG END) lead length..a bit over 1 inch. I could have been
more careful and wound two separate coils and made sure the spacing between the turns was the same and the positioning on the core was the same ect..
but..I am just trying this to make sure the cores are -43 material as the supplier stated they were. SEEMS CLOSE ENOUGH FOR GOVERNMENT WORK AS THEY
SAY. FOR AMATEUR RADIO PROJECTS..I WOULD BE CONFIDENT IN THESE CORES. I have bought cores over the years from about 4 different suppliers
including Micro metals and Amidon. Amidon used to the the main supplier back in the 70s but now with the internet and so many qrp people with their web
sites and all their projects..many people..(including me) sell parts. I sell in limited quantities though.
|I'll be doing some more measuring of different Ferrites as well over the next few
days and I will be writing and taking pictures and posting them here.
|Just a note about the type 72 ferrite cores used in the W7EL QRP
wattmeter - apparently Amidon doesn't sell that type anymore.
A couple of us here are looking at type 77 as a replacement. I built
up the coupler for the wattmeter and attached coax connectors at the
two "diode" ports... preliminary sweep results look good for using
type 77 as a replacement for type 72
"found this note on either the QRP-L reflector or somewhere else on the
web"...I have not built the W7EL wattmeter YET ..de earl ve3ab.
|Later (1995) ARRL Handbooks specify the type 77 for this project.
|I went out and bought about 10 of these
type 77 cores about 10 years ago when I
was thinking of building that wattmeter.
I still have the cores and I plan to test
them in the next few days..
If you are building the w7el wattmeter ..I
might be able to help with some of these
cores at a reasonable price.
I hope to build the watt meter in the near
future. I now have a stock of the ICs for
the project as well.
73 earl ve3ab
|So far..I am very pleased with this LC meter.
I have not used it with large capacitors (yet).
When I do use for capacitors,,I will be sure
to discharge the capacitor with a bleeder
I intend to build some carefully wound coils
to check the calibration of this unit..or I will
buy some close tolerance coils. So
far..seems to be good.
If there is an error (and that has yet to be
determined); perhaps it will be a repeatable
error. That is..if the instrument is out by 3 or
4 percent ..perhaps it is always out by that
percentage and you can factor that in to the
measurement for better accuracy.
The LC bridge is still available on ebay. It is
a basic circuit without a box or fancy
enclosure. I store it in a plastic box and
bring it out to use it on the bench.
It is powered by the laptop computer. Other
than that..the computer does is not used
with the unit for memory or data
transfers..just to power it by the USB port.
I also have an Autek RF 1 analysers I use
from time to time.
|I sell a wide
variety of small
Ham radio OPS
|W7EL qrp wat-meter
(the Oak Hills Wat-meter
is based on the Roy
|TOROID CORES..MY PRICES availability and testing.
|Part Number price each
T25-2 20 cents ea.
T25-6 20 cents ea.
T30-2 20 cents ea.
T30-6 22 cents ea
T37-2 30 cents each
T37-6 32 cents each
T37-7 35 cents ea
T44-2 40 cents ea.
T44-6 42 cents eac
T50-1 50 cents eac
T50-2 45 cents ea
T50-6 45 cents ea
T50-7 45 cents each
T50-10 55 cents each
T68-1 65 cents each
T68-2 65 cents each
T68-6 65 cents each
T68-7 70 cents each
T80-2 75 cents each
T80-6 85 cents each
new T80-10 (I have a few I can sell)
T106-0 (new) I have a few I can sell
T106-2 $1.20 each
T106-6 $1.45 each
T130-2 $1,50 each
T130-6 $1,80 eacg
T200-2 very limited supply
T200-6 very limited supply
Ferrites (I will be pricing these soon) note: for large
orders of Ferrites and Iron Powder Cores I recommend
W8DIZ the torroid king. His web site. If you only need a few
for a project..I can help you out. I carry these items as a
convenience to people who buy other items from me. My
prices are about 30 pct higher than W8DIZ because of
shipping and a slim wee 10 to 15 pct profit for me.
|The smaller sized cores and Ferrite Beads and Baluns I can send in a lightly padded
envelope for $1.44 across Canada ..up to about 100 grams in weight.
NOTE: MY QUANITIES ARE SOMEWHAT LIMITED. I typically supply only a dozen or so cores at a
time (usually). Sometimes only a few!!-- I COMBINE ITEMS TO SAVE ON POSTAGE.
This is not my "CORE" business. MY ""CORE"" BUSINESS IS SEMICONDUCTORS and ICs
PLEASE PARDON THE PUN !!
I do sell the cores to have a well rounded inventory to offer to people who are building little
qrp projects and for myself..I build stuff too! I do combine items to maximize your shipping
costs. Iam a builder, tinkerer and experimenter and I have this stuff around anyways. The
little money I make goes into my hobby of electronics, ham radio and the web sites I operate.
FOR LARGER ORDERS..just google QRP and Toroids and you can find many suppliers with
better prices than myself. If you just need a small amount of cores..my service might be the
most economical for you. Across Canada large envelope: $1.50 to mail and to USA about $2.80
with no handling charges.
For small wee orders ..I'm your man! Sometimes it is worth it to buy from me. I can save money
on shipping particularly for CANADA.
--> I live in Elliot Lake, Ontario CANADA and I sell by mail order: radio parts for older solid
state radios from the late 60s, 70s and early 80s.
I have NO MINIMUMS! I ONCE PULLED AND MEASURED A single core from an old qrp rig and
shipped it off to someone. I think I only charged him about $3 for this service.
|MY "core business" is NOT COREs.. BUT....>>>
Semiconductors AND Transistors and ICs AND good used pulled
PARTS from 1970s/1980s vintage radios. ie Ten Tec Argonauts,
Scout, FT301 (I have 5 of these transceivers); Atlas 210x, TS780
Also..I buy broken gear and fix it up and either sell it for a wee
profit or I use it myself.
I also tear down and part out rigs that are damaged or
butchered up or have serious issues.
Radio gear from the 1970s and 80s ..SOLID STATE. I have some
tubes as well.
if you want to sell off or even give away old gear of this vintage.
I also take parts off boards (de-soldering) if the parts are good
vintage semiconductors/ICS ie..RCA vintage parts ect.
|TESTS AND MEASUREMENTS (ON THE BENCH) (note: I do bench measurements testing
toroid cores and I can custom wind...at my VERY LOW $10 per hour bench rate!!!
|I use a 6 turn winding and use this chart as my 'GUIDE'.
Lately Ive tried a 2.5 turn winding for certain
|The w7EL wattmeter is a good linear scale meter. I have the parts here to
build one and I have extra CA3160AE chips and several -77 cores I can
sell. The CA3160ae chips are a bit hard to source and I sell them
cheaper than any ebay seller..with economy postage to boot.
|Do you have broken/stuck ferrite cores for slug tuned coils or other broken
ferrites and powered iron cores. I can measure them here and I keep a whole
whack of ferrite slugs and I can match one or more up as a service. I charge
only a few bucks for doing this. -- My $10 per hour bench rate makes it worth
while to send items back and forth "MAIL ORDER business service" In
CANADA small slugs for coils can be sent letter mail for $1.44 across Canada.
USA about double that amount and abroad..approx $5.20 from Canada