Date   
Re: Inductance Meter

Hans Summers <Hans.Summers@...>
 

Following Farhan's mention of my frequency counters...

http://www.hanssummers.com/electronics/equipment/radiofreqcounter/intro.htm
this one is a full 8-digit counter.

On the other hand, you can throw together something really fast with 8=LED
binary readout and only 2 chips:

http://www.hanssummers.com/radio/sfreq/index.htm

This reads only 0 - 99.5KHz, the MHz and 100KHz aren't shown. However,
please note that is is quite easy to fit a switch to select a different
division of the timebase, in order to obtain a MHz reading. Look at the
website of Onno PA2OHH http://www.qsl.net/pa2ohh/sfreq.htm whose ideas my
counter is based on.

73 Hans G0UPL
http://www.HansSummers.com

-----Original Message-----
From: Ashhar Farhan [mailto:farhan@...]
Sent: 05 July 2004 03:01
To: Charles
Cc: BITX20@...
Subject: Re: [BITX20] Inductance Meter




the VFO of BITX20 has an interesting story. it is actually my inductance
meter! looking at the VFO, if you removed the trimmer, it becomes a test
oscillator that iuse at all times. this idea is due to W7AAZ (Bill Carver).
you can quickly assemble a frequency counter like one of the several shown
by Hans. To measure an inductance, solder the the coil into the VFO circuit,
measure the frequency. The capacitance is well established, from there
calculate the inductance. i had written a few lines code in C (i think it is
posted it its entirity on rec.radio.amateur.homebrew). that helped me
calculate it quickly. the test oscillator also works as acrystal oscillator
(solder a crystal in place of the coil) to measure and match the crystals.

- farhan


On Sun, 4 Jul 2004, Charles wrote:

Hi all

I note that the post has separated part of the url from the web page
mentioned - let's try again ----

www.web-ee.com/Schematics/Inductance%20Meter/Inductance%20Meter.htm

You need all without a break between Inductance% and 20Meter.htm

I hope this helps you to find the page...

Charles

Re: using the BITX on RTTY

Hans Summers <Hans.Summers@...>
 

Hans I wonder if you would like to confirm one or two items
which are not clear to me...
No problem! My favourite varicap is a standard 5mm red LED. Have a look at
my 30m QRSS beacon project http://www.hanssummers.com/radio/qrss/index.htm
which used one for the frequency shifting to produce DFCW and
slow-hellscreiber modes. Far too many people get stuck ordering components
for a project, when they can't find the specified varicap. Varicaps are
components which seem to go in and out of fashion quite quickly. In most of
those cases, they could easily substitute with something else, or even just
a simple diode. Don't forget even in the BITX20 we're using a 36V zener
diode for the VFO fine tuning! A "real" varicap diode will have more
precisely defined and reproduceable capacitance limits but in the majority
of homebrew QRP circuits, that isn't very important. One exception is if you
want a large capacitance, e.g. the BB212 varicap which seems to be
increasingly hard to find. Even in this case, many times the circuit can
easily be redesigned for a lower capacitance range.


1. that the volts into the 4060 are 12V
Errr.... No. I used 12V on the "varicap" but only a +5V supply to the 4060.
The reason I say "err" is that according to the datasheet, the "typical"
maximum clock frequency of the old 4000-series CMOS version of this IC is
7MHz on a 5V supply (no "maximum" maximum clock frequency is indicated).
Ooops. But it did work Ok for me anyway despite being violation of the
datasheet parameters. At higher supply voltages the 4060 has typical 16MHz
at 10V and 24MHz at 15V. So you would be better off using +12V supply anyway
;-) Even better, use the modern 74HC4060, at 5V supply you're looking at
over 30MHz for the max count freq. But you'd need 5V supply for 74HC.

2. that the 14MHz xtal could be changed for one of the 10MHz
xtal already obtained ( through you ) for the project ...
Sure, why not. Any crystal should exhibit the same pullable effect with
parallel capacitance. Although some are more "pullable" than others and as
you might expect, in general you will find that the higher the frequency the
greater the shift (in absolute KHz terms). From my "crystal penning"
experiments and those of Dave WA4QAL there appears to be some evidence that
physically smaller crystals are more shiftable, e.g. we obtained more shift
on HC49 style crystals than the larger slab in an HC6 case. The same might
apply to pulling with capacitors, but I don't know. The 14MHz crystal I used
was the common HC49-cased variety.

While we're on the subject of crystals, if you want to move them by more
than a bit of capacitance will accomplish, you can get many KHz lower by
removing the case and painting the crystal with ink! See my page about this:
http://www.hanssummers.com/radio/penning/index.htm. My 1-valve CW tx for
80/40m (http://www.hanssummers.com/radio/cwtx/index.htm) contains two
"penned" crystals: 3.558 (originally 3.579) and 7.010 (originally 7.030).
See also the first modification I made to the 30m QRSS beacon I mentioned
above, http://www.hanssummers.com/radio/qrss/qrv/mod1/index.htm, which was
to add a 10.140 crystal. I guess that this crystal must have been custom
manufactured at some point but it wasn't very accurate, 4KHz to high. A
single ink dot on its surface was enough to bring it down to 10.142 which
was about perfect for what I wanted.

And if you want to go the other way and increase the frequency of a crystal?
Grind it and grind it, then grind some more. For this you need a larger
crystal (e.g. FT-243 style), the HC49 is just too small and you wouldn't be
able to remount if afterwards. See
http://home.netcom.com/~wa4qal/crystal.htm for some interesting grinding
experiments recently undertaken by Dave WA4QAL.

3. could I / a student use ugly construction for the test
project ???
Yes definitely! I used a scrap of plain matrix board but "ugly" is fine too!

73 de Hans G0UPL
http://www.HansSummers.com

Re: Bitx 20, Help me!

Juanjo Pastor
 

Hello again Chris,

Crystals between 8 and 12MHz are easy to get here
in Europe,
They are also cheap available by one of the group members but (as
mentioned by one of the other group members) some persons have a
kind of brain damage that force us to use what we have. Spending
hours to get some used parts from an old PCB cost ofcourse more then
buying new but now I can say: 'I build this transceiver from scrap
and components that I had collected in the past'.
An other point of view; by using these alternatives, you learn a lot
about parameters and the circuit!
(If I do not get it working the way I want to, may be I will go to
the 10 MHz IF ;-) ).
If you want to follow the "from scrap" route, you'd better use 8.86 MHz
crystals from defunct color TV sets or the 14.318 MHz ones from old and/or
defunct PC motherboards...

I am not building the BITX, but I am enjoying this list and
learning about

I appreciate your comments, as mentioned above, search in your junk
box and build your own tranceiver based on the BITX20.

Chris, PA3CRX
As I said before, I do own almost all of the parts or can get them easily,
the hard one here is the IRF510 but I have a few of them from scrap... I am
into a 40m CW VXO TX, when I end it maybe I will start the 20 meter SSB
project...

73, 72 de Juanjo, EA5CHQ-EC5ACA. EA-QRP #104, G-QRP #9742,
QRP-L #1662.

Juanjo Pastor
C/San Roque, 4-1�
46460 Silla
SPAIN

e-mail: ea5chq@...
web: http://www.ea5chq.tk
web del club: http://www.eaqrp.com
Tel.: +034 96 120 17 67
Movil: 651 35 35 11

New file uploaded to BITX20

BITX20@...
 

Hello,

This email message is a notification to let you know that
a file has been uploaded to the Files area of the BITX20
group.

File : /K7HKL/BITX20 FREQUENCY CALCULATION SPREADSHEET.xls
Uploaded by : k7hkl_arv <arvevans@...>
Description :

You can access this file at the URL

http://groups.yahoo.com/group/BITX20/files/K7HKL/BITX20%20FREQUENCY%20CALCULATION%20SPREADSHEET.xls

To learn more about file sharing for your group, please visit

http://help.yahoo.com/help/us/groups/files

Regards,

k7hkl_arv <arvevans@...>

Trifilar Twister Tool

Arv Evans <arvevans@...>
 

Hi

Twisting the wires together for winding trifilar inductors is made easier with a simple tool built for that purpose.  A picture of my "Trifilar Twister Tool" is attached to this email.  A copy of the picture is also available at BITX20/FILES/K7HKL/Trifilar Twister Tool.gif.

I made this using a 1 inch long section of plastic tube (3/8 In. OD by 3/16 in. ID) and a stiff section of wire.  You can build this using material at hand.

Operation involves securing the far end of your wire so that it will not twist.  Then connect the near end of your wire to the twister tool.  By holding the bushing and turning the crank handle you can control the tension, count the turns ( turns / length = turns per unit length ), and make a very clean looking double, triple, or quadruple wire for winding on toroid forms.

Arv
_._
+

Re: Trifilar Twister Tool

Charles Darley
 


Hi All
 
What a great idea ...  wish I had thought of it my self -- a bit more control than using an electric drill  !!
 
Charles G4VSZ

-----Original Message-----
From: Arv Evans [mailto:arvevans@...]
Sent: 06 July 2004 20:09
To: bitx20@...
Subject: [BITX20] Trifilar Twister Tool

Hi

Twisting the wires together for winding trifilar inductors is made easier with a simple tool built for that purpose.  A picture of my "Trifilar Twister Tool" is attached to this email.  A copy of the picture is also available at BITX20/FILES/K7HKL/Trifilar Twister Tool.gif.

I made this using a 1 inch long section of plastic tube (3/8 In. OD by 3/16 in. ID) and a stiff section of wire.  You can build this using material at hand.

Operation involves securing the far end of your wire so that it will not twist.  Then connect the near end of your wire to the twister tool.  By holding the bushing and turning the crank handle you can control the tension, count the turns ( turns / length = turns per unit length ), and make a very clean looking double, triple, or quadruple wire for winding on toroid forms.

Arv
_._
+

Re: Trifilar Twister Tool

Hans Summers <Hans.Summers@...>
 

 
Nice one Arv!
 
Now we're on the subject I'll share my own method and experiences in case it helps anyone.
 
I don't have available nice new spools of wire labelled 28 or 32 swg. I do have a junk box full of all sorts of things. I had some metres of wire removed from a defective lighting dimmer switch. I have no idea what the gauge of this wire is, but for the purposes of this project I called it swg 28 for the time being.
 
Finer wire was more of a problem. I have a number of old defective emergency lighting controller PCB's donated by the facilities manager at my office. Each contains several small transformers, which use a powdered iron core rather than E I laminated construction. These small transformers are easy to break up by carefully using a pair of pliers to crush the core, and easily remove the wire.
 
I had a little trouble finding wire of suitable thickness. Some of it was rather thin and when I attempted to "trifilarise" it, it snapped. What I called "28 swg" turned out to be too think to get 40 bifilar turns on a tap washer for the power amplifier transformer. So I had to hunt for something slightly thinner, but not quite as thin as the wire I found and called "32 swg".
 
Another problem to be wary of is straightening the wire after removing from the bobbin. Doing it using your fingers will lead to a nice clean but deep cut. Just think about cheese cutting wire. Once I'd reminded myself of this painfully, I used the rubber shaft of a mains-testing screwdriver to straighten the wire. I tied one end of the wire to a kitchen cupboard door handle, and wound one turn around the screwdriver shaft. You can then pull through to the end of the wire and it straightens it perfectly. I mentioned this on the GQRP list and someone mentioned soing the same thing, using a dowel wooden rod (a bare metal screwdriver shaft would probably damage the wire's enamel).
 
Once I had salvaged enough useful wire, I created trifilar wire by taking three 5-foot lengths of wire, and tying one end to the cupboard door handle again. The other ends were clamped in the chuck of my electric drill. By using the drill on its slowest setting I was able to quickly wind trifilar wire. The tension in the wire is important. Too slack, and it twists up into a ball. Too tight, and the drill snaps the wire. I found the right tension was to pull it tight and then give back an inch or two. After each burst of "drilling" I counted the number of twists by holding the wire parallel with a ruler. Note that each turn creates two "twists" on the wire so counting the bumps for 8 turns per inch, you need 16 bumps per inch.
 
I found this method worked quite well for me after one or two failed attempts. Arv's method would I'm sure give a lot more control over the tension etc and be less likely to result in wire breakages. The only thing that would worry me is that at 8 turns per inch, for 5 feet of wire that's almost 500 turns which is quite a lot more effort by hand. I did wind the mixer transformer by hand using a screwdriver shaft at one end and the door handle at the other. About 1 foot of wire, 96 turns, and even that was more effort than I liked but maybe I'm just lazy ;-)
 
73 Hans G0UPL
http://www.HansSummers.com 

-----Original Message-----
From: Charles Darley [mailto:charles@...]
Sent: 06 July 2004 21:10
To: BITX20@...
Subject: RE: [BITX20] Trifilar Twister Tool

Hi All
 
What a great idea ...  wish I had thought of it my self -- a bit more control than using an electric drill  !!
 
Charles G4VSZ
-----Original Message-----
From: Arv Evans [mailto:arvevans@...]
Sent: 06 July 2004 20:09
To: bitx20@...
Subject: [BITX20] Trifilar Twister Tool

Hi

Twisting the wires together for winding trifilar inductors is made easier with a simple tool built for that purpose.  A picture of my "Trifilar Twister Tool" is attached to this email.  A copy of the picture is also available at BITX20/FILES/K7HKL/Trifilar Twister Tool.gif.

I made this using a 1 inch long section of plastic tube (3/8 In. OD by 3/16 in. ID) and a stiff section of wire.  You can build this using material at hand.

Operation involves securing the far end of your wire so that it will not twist.  Then connect the near end of your wire to the twister tool.  By holding the bushing and turning the crank handle you can control the tension, count the turns ( turns / length = turns per unit length ), and make a very clean looking double, triple, or quadruple wire for winding on toroid forms.

Arv
_._

Re: Trifilar Twister Tool

Arvid Evans <arvevans@...>
 

Hans

When working with really small wire (ie. you don't have anything
better to work with!) try twisting two or even three conductors
together and use this as one wire to wind your toroid coils. This
gives you both a stronger wire for winding, and more skin-area for a
lower coil resistance. If the wire is really small there should still
be enough room on your core former for the required number of turns.

Arv - K7HKL
_._


--- In BITX20@..., Hans Summers <Hans.Summers@t...> wrote:

Nice one Arv!

Now we're on the subject I'll share my own method and experiences in
case it
helps anyone.

I don't have available nice new spools of wire labelled 28 or 32
swg. I do
have a junk box full of all sorts of things. I had some metres of wire
removed from a defective lighting dimmer switch. I have no idea what the
gauge of this wire is, but for the purposes of this project I called
it swg
28 for the time being.

Finer wire was more of a problem. I have a number of old defective
emergency
lighting controller PCB's donated by the facilities manager at my
office.
Each contains several small transformers, which use a powdered iron core
rather than E I laminated construction. These small transformers are
easy to
break up by carefully using a pair of pliers to crush the core, and
easily
remove the wire.

I had a little trouble finding wire of suitable thickness. Some of
it was
rather thin and when I attempted to "trifilarise" it, it snapped. What I
called "28 swg" turned out to be too think to get 40 bifilar turns
on a tap
washer for the power amplifier transformer. So I had to hunt for
something
slightly thinner, but not quite as thin as the wire I found and
called "32
swg".

Another problem to be wary of is straightening the wire after
removing from
the bobbin. Doing it using your fingers will lead to a nice clean
but deep
cut. Just think about cheese cutting wire. Once I'd reminded myself
of this
painfully, I used the rubber shaft of a mains-testing screwdriver to
straighten the wire. I tied one end of the wire to a kitchen
cupboard door
handle, and wound one turn around the screwdriver shaft. You can
then pull
through to the end of the wire and it straightens it perfectly. I
mentioned
this on the GQRP list and someone mentioned soing the same thing,
using a
dowel wooden rod (a bare metal screwdriver shaft would probably
damage the
wire's enamel).

Once I had salvaged enough useful wire, I created trifilar wire by
taking
three 5-foot lengths of wire, and tying one end to the cupboard door
handle
again. The other ends were clamped in the chuck of my electric drill. By
using the drill on its slowest setting I was able to quickly wind
trifilar
wire. The tension in the wire is important. Too slack, and it twists
up into
a ball. Too tight, and the drill snaps the wire. I found the right
tension
was to pull it tight and then give back an inch or two. After each
burst of
"drilling" I counted the number of twists by holding the wire
parallel with
a ruler. Note that each turn creates two "twists" on the wire so
counting
the bumps for 8 turns per inch, you need 16 bumps per inch.

I found this method worked quite well for me after one or two failed
attempts. Arv's method would I'm sure give a lot more control over the
tension etc and be less likely to result in wire breakages. The only
thing
that would worry me is that at 8 turns per inch, for 5 feet of wire
that's
almost 500 turns which is quite a lot more effort by hand. I did
wind the
mixer transformer by hand using a screwdriver shaft at one end and
the door
handle at the other. About 1 foot of wire, 96 turns, and even that
was more
effort than I liked but maybe I'm just lazy ;-)

73 Hans G0UPL
http://www.HansSummers.com

-----Original Message-----
From: Charles Darley [mailto:charles@d...]
Sent: 06 July 2004 21:10
To: BITX20@...
Subject: RE: [BITX20] Trifilar Twister Tool


Hi All

What a great idea ... wish I had thought of it my self -- a bit more
control than using an electric drill !!

Charles G4VSZ
-----Original Message-----
From: Arv Evans [mailto:arvevans@e...]
Sent: 06 July 2004 20:09
To: bitx20@...
Subject: [BITX20] Trifilar Twister Tool


Hi

Twisting the wires together for winding trifilar inductors is made
easier
with a simple tool built for that purpose. A picture of my "Trifilar
Twister Tool" is attached to this email. A copy of the picture is also
available at BITX20/FILES/K7HKL/Trifilar Twister Tool.gif.

I made this using a 1 inch long section of plastic tube (3/8 In. OD
by 3/16
in. ID) and a stiff section of wire. You can build this using
material at
hand.

Operation involves securing the far end of your wire so that it will not
twist. Then connect the near end of your wire to the twister tool. By
holding the bushing and turning the crank handle you can control the
tension, count the turns ( turns / length = turns per unit length ), and
make a very clean looking double, triple, or quadruple wire for
winding on
toroid forms.

Arv
_._

Toroids have legs! ;-)

Arv Evans <arvevans@...>
 

Hi

In converting the BITX20 design for building my BITX40 transceiver I found myself 'experimenting' with several different sets of air-core toroid inductors. Soldering, removing, & re-soldering these into the circuit quickly became a slight problem because the windings kept unwinding. Here is my solution to that problem (see the photo).



Since I am using slices of PVC pipe for my toroid forms, it was easy to push a heated wire into the PVC and use this to anchor the windings. These short wires (actually the cut off ends of various resistors and capacitors left over from building my BITX20) now serve as component mounting legs for the toroids. If the wires are a bit loose in their holes ( from my overheating them during the insertion process ), a drop of super glue fixes the problem.

Note that in the picture there is a toroid with a capacitor in the middle. This is an alternative to the above idea. I simply super-glued the capacitor leads to the sides of the PVC coil former and connected my coil ends to the capacitor's leads.

I do not know if the same idea can be applied to 'tap washer' based toroids. Since they are a bit smaller it might take more care in positioning the inserted wires.

Arv - K7HKL
_._

Re: Toroids have legs! ;-)

Jim Strohm <jstrohm@...>
 

OK, those are cute.

And way cool, ESPECIALLY the parallel LC config that uses the cap's legs for termination and mounting.

I love this place.

Jim N6OTQ

Re: Toroids have legs! ;-)

Bharat Balsavar <vu2bdx@...>
 

Hi,

This is indeed a good idea.

I have a question - basic becuse I'm very new to this field!

I noticed that some of the turns are closely wound while some are not.

How does this affect the performance of the inductances and are there any thumb rules or 'brewing' basics to have a more even winding?

TIA.

73s
-----
Bharat D Balsavar
VU2BDX





From: Arv Evans <arvevans@...>
Reply-To: BITX20@...
To: bitx20@...
Subject: [BITX20] Toroids have legs! ;-)
Date: Wed, 07 Jul 2004 12:55:40 -0600

Hi

In converting the BITX20 design for building my BITX40 transceiver I
found myself 'experimenting' with several different sets of air-core
toroid inductors. Soldering, removing, & re-soldering these into the
circuit quickly became a slight problem because the windings kept
unwinding. Here is my solution to that problem (see the photo).



Since I am using slices of PVC pipe for my toroid forms, it was easy to
push a heated wire into the PVC and use this to anchor the windings.
These short wires (actually the cut off ends of various resistors and
capacitors left over from building my BITX20) now serve as component
mounting legs for the toroids. If the wires are a bit loose in their
holes ( from my overheating them during the insertion process ), a drop
of super glue fixes the problem.

Note that in the picture there is a toroid with a capacitor in the
middle. This is an alternative to the above idea. I simply super-glued
the capacitor leads to the sides of the PVC coil former and connected my
coil ends to the capacitor's leads.

I do not know if the same idea can be applied to 'tap washer' based
toroids. Since they are a bit smaller it might take more care in
positioning the inserted wires.

Arv - K7HKL
_._
<< ToroidsHaveLegs.gif >>
_________________________________________________________________
Claim your Citibank Ready Cash today. http://go.msnserver.com/IN/52041.asp It�s fast, easy and affordable.

Re: Toroids have legs! ;-)

Arv Evans <arvevans@...>
 

Bharat

The turns on that coil were sloppy because I got tired of winding them.  There are 150 turns of #42 wire on that coil.  While it does work at about the intended inductance I would probably be a bit more careful in winding a final version of my inductors.  That particular coil was wound more for the purposes of the photograph (to show the "legs" on the coil) than to be a final design component.

Now, to answer your question...the number of turns is more important than the beauty of the winding.  I find that for a predictable inductance value I need to make sure the turns are equally spaced, but for less critical construction I can usually get away with scramble-wound coils.  In the BITX20 project we are departing a bit from typical toroid coil methods in that we are using air-core toroids instead of the usual powdered iron or ferrite core material.  This means that:

   (1) It will take over twice the number of turns than would be required for an equivalent ferrite cored inductor.

   (2) It is probably more important that the turns be evenly spaced around nearly the full diameter (360 degrees) of the 'tap washer' former in order to obtain the tight magnetic field that is typical of toroid coils.

   (3) Since Farhan quoted the number of turns required based on his very neat air-core toroids, if you wish to duplicate the design exactly you should probably make you coils look like his.

   (4) I was surprised to find that the "air-core" toroids showed some characteristics that I had previously thought were due more to the ferrite core material than to the circular layout of the coil.  This specifically was the very light coupling I was able to get with my dip meter.  I had to use a coupling loop to obtain a good dip indication.   I think this indicates that the shape of the coil is more important than I had thought, and that this toroidal shape probably helps to minimize unwanted coupling between inductors, and between an inductor and other components of the circuit.

   (5)  The use of "air-core" type toroids is probably a plus in this design because ferrite material is inherently temperature unstable.  Thus an air-core coil for the VFO tuned circuit should be easier to stabilize for frequency than one with a ferrite core material.  For the VFO inductor you should be careful to make the winding as tight as possible (or just cover it with hot-melt glue like I did) to make sure that there is minimal physical movement of the turns with temperature changes or vibration.

   (6)  For Farhan's BITX design the use of Tap Washers as coil formers is probably the most common method because they are usually black and thus look like their ferrite cored cousins, even though they are actually working as air-cored toroids (yes, the dielectric constant of nylon or PVC is not quite the same as that of air).  You can use nearly any plastic material for the former for air-cored toroids.  If you wonder if your particular plastic is suitable for RF use, you can put a piece of the material in the microwave oven for a minute to see if it gets warm.  If it heats up under 1 minute of microwave exposure you should probably look for a better material.

You may notice from the pictures that I did not use "tap washers".  Instead I am using 1/4 inch long slices of 1/2 inch PVC pipe.  I did this because I had the PVC pipe available and not the tap washers, and because it let me cut a slot in the PVC to make it easier to wind the many turns.  Passing the wire through that slot is much easier than threading it through the hole in the core.  If you use PVC instead of Tap Washers you may have to adjust the number of turns slightly to obtain the correct inductance value.  In my case I used a dip meter and Farhan's indicated capacitance values to determine if I had the correct number of turns.  This way I maintained the original design L/C ratio and hopefully about  the same Q factor that Farhan used.

I hope this helps.  Please feel free to ask more questions.  Either myself or some of the more expert people on this forum should be glad to help.

73's
Arv - K7HKL

On Wed, 2004-07-07 at 23:29, Bharat Balsavar wrote:
Hi,

This is indeed a good idea.

I have a question - basic becuse I'm very new to this field!

I noticed that some of the turns are closely wound while some are not.

How does this affect the performance of the inductances and are there any 
thumb rules or 'brewing' basics to have a more even winding?

TIA.

73s
-----
Bharat D Balsavar
VU2BDX





>From: Arv Evans 
>Reply-To: BITX20@...
>To: bitx20@...
>Subject: [BITX20] Toroids have legs!    ;-)
>Date: Wed, 07 Jul 2004 12:55:40 -0600
>
>Hi
>
>In converting the BITX20 design for building my BITX40 transceiver I
>found myself 'experimenting' with several different sets of air-core
>toroid inductors. Soldering, removing, & re-soldering these into the
>circuit quickly became a slight problem because the windings kept
>unwinding. Here is my solution to that problem (see the photo).
>
>
>
>Since I am using slices of PVC pipe for my toroid forms, it was easy to
>push a heated wire into the PVC and use this to anchor the windings.
>These short wires (actually the cut off ends of various resistors and
>capacitors left over from building my BITX20) now serve as component
>mounting legs for the toroids. If the wires are a bit loose in their
>holes ( from my overheating them during the insertion process ), a drop
>of super glue fixes the problem.
>
>Note that in the picture there is a toroid with a capacitor in the
>middle. This is an alternative to the above idea. I simply super-glued
>the capacitor leads to the sides of the PVC coil former and connected my
>coil ends to the capacitor's leads.
>
>I do not know if the same idea can be applied to 'tap washer' based
>toroids. Since they are a bit smaller it might take more care in
>positioning the inserted wires.
>
>Arv - K7HKL
>_._
><< ToroidsHaveLegs.gif >>

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Toriod Q

m1dgs <d.snell@...>
 

Has anyone measured the Q of the toriods? I wondered whether it
mattered too much provided the winding details were observed.

However care has to be taken with the coating materials.
There is an interesting note by Roy Lewallen, W7EL on Mounting
Toroidal Inductors with Common Materials:-
http://www.qrp.pops.net/w7el.htm
His results show that his black sealing tape reduced the Q of his
coil by nearly 40%. Other materials were noted to have lesser effects
although some were worse than others, notably Duco cement. Duco
cement is a nitro cellulose household glue which reduced the Q by
nearly 25%.

Dave M1DGS

Inexpensive capacitor measurements...

Arv Evans <arvevans@...>
 

Hi

Since Farhan's stated original intent in designing the BITX20 was to provide an inexpensive transceiver, maybe it would be appropriate to show BITX builders an inexpensive way to measure unmarked or questionable capacitors.  The following circuit came to me via Don Metzger - K8JWR, but I suspect the method has been around for quite some time.  The picture shown here is the relatively simple schematic for this tool.



Use a mains transformer that delivers a few ma. at about 15 volts RMS.  Connect a known .001 mfd capacitor at Cx and adjust the value of R1 ( for R1 I used a 250K trim pot salvaged from an old circuit card ) for an indication of 1.000 volts on your DVM.  Now you can measure capacitor values from a few pf up to 0.001 mfd by connecting them in the place of Cx. 

I used this method to "calibrate" the knob indicator on a 3X450 pf variable capacitor that I regularly use as part of my test equipment repertoire.  Now I just set the dip meter to the desired frequency, and use the variable capacitor to tune my inductor for a dip on that setting.  Once the coil is on-frequency I can read the capacitance from my calibrated variable capacitor and substitute that value of fixed capacitance into the circuit.

Part of the fun derived from building your own ham radio equipment is in devising ways to perform complex design and testing by use of relatively simple and inexpensive methods & equipment.  This idea fits into that category.

73's
Arv
_._

Before someone asks the question...No, this circuit will not measure electrolytic capacitors, but it will get you close enough for most of the small caps you will be using in designing resonant circuits for HF applications.
---------------------------------------------------------

Re: Inexpensive capacitor measurements...

John Fisher <k5jhf@...>
 

Very Nice, thanks very much :-)

 Regards,
 John
 
=============================================
email:      k5jhf@...
photos:   http://photos.yahoo.com/k5jhf@...
files:       http://briefcase.yahoo.com/k5jhf@...
webpage: http://www.geocities.com/k5jhf@...
callsign:    K5JHF
=============================================

-----Original Message-----
From: Arv Evans [mailto:arvevans@...]
Sent: Thursday, July 08, 2004 3:35 PM
To: bitx20@...
Subject: [BITX20] Inexpensive capacitor measurements...

Hi


73's
Arv
_._

Before someone asks the question...No, this circuit will not measure electrolytic capacitors, but it will get you close enough for most of the small caps you will be using in designing resonant circuits for HF applications.
---------------------------------------------------------

Re: Toroids have legs! ;-)

Bharat Balsavar <vu2bdx@...>
 

Thanks, Arv.
73s
-----
Bharat D Balsavar
VU2BDX


From: Arv Evans <arvevans@...>
Reply-To: BITX20@...
To: BITX20@...
Subject: RE: [BITX20] Toroids have legs! ;-)
Date: Thu, 08 Jul 2004 00:28:47 -0600

Bharat

The turns on that coil were sloppy because I got tired of winding them.
There are 150 turns of #42 wire on that coil. While it does work at
about the intended inductance I would probably be a bit more careful in
winding a final version of my inductors. That particular coil was wound
more for the purposes of the photograph (to show the "legs" on the coil)
than to be a final design component.

Now, to answer your question...the number of turns is more important
than the beauty of the winding. I find that for a predictable
inductance value I need to make sure the turns are equally spaced, but
for less critical construction I can usually get away with
scramble-wound coils. In the BITX20 project we are departing a bit from
typical toroid coil methods in that we are using air-core toroids
instead of the usual powdered iron or ferrite core material. This means
that:

(1) It will take over twice the number of turns than would be
required for an equivalent ferrite cored inductor.

(2) It is probably more important that the turns be evenly spaced
around nearly the full diameter (360 degrees) of the 'tap washer' former
in order to obtain the tight magnetic field that is typical of toroid
coils.

(3) Since Farhan quoted the number of turns required based on his
very neat air-core toroids, if you wish to duplicate the design exactly
you should probably make you coils look like his.

(4) I was surprised to find that the "air-core" toroids showed some
characteristics that I had previously thought were due more to the
ferrite core material than to the circular layout of the coil. This
specifically was the very light coupling I was able to get with my dip
meter. I had to use a coupling loop to obtain a good dip indication.
I think this indicates that the shape of the coil is more important than
I had thought, and that this toroidal shape probably helps to minimize
unwanted coupling between inductors, and between an inductor and other
components of the circuit.

(5) The use of "air-core" type toroids is probably a plus in this
design because ferrite material is inherently temperature unstable.
Thus an air-core coil for the VFO tuned circuit should be easier to
stabilize for frequency than one with a ferrite core material. For the
VFO inductor you should be careful to make the winding as tight as
possible (or just cover it with hot-melt glue like I did) to make sure
that there is minimal physical movement of the turns with temperature
changes or vibration.

(6) For Farhan's BITX design the use of Tap Washers as coil formers
is probably the most common method because they are usually black and
thus look like their ferrite cored cousins, even though they are
actually working as air-cored toroids (yes, the dielectric constant of
nylon or PVC is not quite the same as that of air). You can use nearly
any plastic material for the former for air-cored toroids. If you
wonder if your particular plastic is suitable for RF use, you can put a
piece of the material in the microwave oven for a minute to see if it
gets warm. If it heats up under 1 minute of microwave exposure you
should probably look for a better material.

You may notice from the pictures that I did not use "tap washers".
Instead I am using 1/4 inch long slices of 1/2 inch PVC pipe. I did
this because I had the PVC pipe available and not the tap washers, and
because it let me cut a slot in the PVC to make it easier to wind the
many turns. Passing the wire through that slot is much easier than
threading it through the hole in the core. If you use PVC instead of
Tap Washers you may have to adjust the number of turns slightly to
obtain the correct inductance value. In my case I used a dip meter and
Farhan's indicated capacitance values to determine if I had the correct
number of turns. This way I maintained the original design L/C ratio
and hopefully about the same Q factor that Farhan used.

I hope this helps. Please feel free to ask more questions. Either
myself or some of the more expert people on this forum should be glad to
help.

73's
Arv - K7HKL

On Wed, 2004-07-07 at 23:29, Bharat Balsavar wrote:

Hi,

This is indeed a good idea.

I have a question - basic becuse I'm very new to this field!

I noticed that some of the turns are closely wound while some are not.

How does this affect the performance of the inductances and are there
any
thumb rules or 'brewing' basics to have a more even winding?

TIA.

73s
-----
Bharat D Balsavar
VU2BDX





From: Arv Evans <arvevans@...>
Reply-To: BITX20@...
To: bitx20@...
Subject: [BITX20] Toroids have legs! ;-)
Date: Wed, 07 Jul 2004 12:55:40 -0600

Hi

In converting the BITX20 design for building my BITX40 transceiver I
found myself 'experimenting' with several different sets of air-core
toroid inductors. Soldering, removing, & re-soldering these into the
circuit quickly became a slight problem because the windings kept
unwinding. Here is my solution to that problem (see the photo).



Since I am using slices of PVC pipe for my toroid forms, it was easy to
push a heated wire into the PVC and use this to anchor the windings.
These short wires (actually the cut off ends of various resistors and
capacitors left over from building my BITX20) now serve as component
mounting legs for the toroids. If the wires are a bit loose in their
holes ( from my overheating them during the insertion process ), a drop
of super glue fixes the problem.

Note that in the picture there is a toroid with a capacitor in the
middle. This is an alternative to the above idea. I simply super-glued
the capacitor leads to the sides of the PVC coil former and connected
my
coil ends to the capacitor's leads.

I do not know if the same idea can be applied to 'tap washer' based
toroids. Since they are a bit smaller it might take more care in
positioning the inserted wires.

Arv - K7HKL
_._
<< ToroidsHaveLegs.gif >>
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Cleaning PC Board material for your BITX transceiver construction

Arv Evans <arvevans@...>
 

Hi

PC Board material that is stored for some time usually takes on a layer of oxidation that hinders soldering components to its surface.  In the past I have routinely used sandpaper to remove this oxidation and prepare the surface for my "ugly construction" projects.  Now I think I might have found a better way to prepare the surface.  I tried a small wire brush and found that it not only removes surface oxidation, it also leaves a much more polished surface and requires less effort.  The wire brush was purchased at a local hobby store for about $1 US, see the picture below.  If you have a small wire brush you might try it and see if it works for you.



73's
Arv
_._

Re: Cleaning PC Board material for your BITX transceiver construction

Charles Darley
 


Hi

Can I also suggest that where the components are to be placed that the PCB pad is tinned and where earth connections are to be made that area too is tinned, as it ensures a good joint and the joint is quicker too!! 

 

I think the sort of bush mentioned has brass wire bristles and used for cleaning suede shoes !!

 
Charles  G4VSZ
 
 
 -----Original Message-----
From: Arv Evans [mailto:arvevans@...]
Sent: 09 July 2004 19:00
To: bitx20@...; rlelm@...; leatkin@...; bequan@...; ciresnave@...
Subject: [BITX20] Cleaning PC Board material for your BITX transceiver construction

Hi

PC Board material that is stored for some time usually takes on a layer of oxidation that hinders soldering components to its surface.  In the past I have routinely used sandpaper to remove this oxidation and prepare the surface for my "ugly construction" projects.  Now I think I might have found a better way to prepare the surface.  I tried a small wire brush and found that it not only removes surface oxidation, it also leaves a much more polished surface and requires less effort.  The wire brush was purchased at a local hobby store for about $1 US, see the picture below.  If you have a small wire brush you might try it and see if it works for you.



73's
Arv
_._


Re: Cleaning PC Board material for your BITX transceiver construction

Bruce Raymond <bruceraymond@...>
 


I'd like to suggest the use of a copper/silver cleaner, such as Tarn-X.  I don't know
what would be similar across the pond or in other parts of the world.  I just pour a
little bit of Tarn-X on a paper towel or rag and then wipe the pcb.  Be sure to wash
off the Tarn-X residue with water when you're done.  I've heard of people using
toilet bowl cleaners and such, but this appears to be more benign.  It does a
reasonable job, although not as good as a serious session with steel wool.  OTOH,
it's a *lot* less work  ;-)
 
- Bruce  ND8I
 
 

-----Original Message-----
From: Charles Darley [mailto:charles@...]
Sent: Friday, July 09, 2004 2:55 PM
To: BITX20@...
Subject: RE: [BITX20] Cleaning PC Board material for your BITX transceiver construction

Hi

Can I also suggest that where the components are to be placed that the PCB pad is tinned and where earth connections are to be made that area too is tinned, as it ensures a good joint and the joint is quicker too!! 

 

I think the sort of bush mentioned has brass wire bristles and used for cleaning suede shoes !!

 
Charles  G4VSZ
 
 
 -----Original Message-----
From: Arv Evans [mailto:arvevans@...]
Sent: 09 July 2004 19:00
To: bitx20@...; rlelm@...; leatkin@...; bequan@...; ciresnave@...
Subject: [BITX20] Cleaning PC Board material for your BITX transceiver construction

Hi

PC Board material that is stored for some time usually takes on a layer of oxidation that hinders soldering components to its surface.  In the past I have routinely used sandpaper to remove this oxidation and prepare the surface for my "ugly construction" projects.  Now I think I might have found a better way to prepare the surface.  I tried a small wire brush and found that it not only removes surface oxidation, it also leaves a much more polished surface and requires less effort.  The wire brush was purchased at a local hobby store for about $1 US, see the picture below.  If you have a small wire brush you might try it and see if it works for you.



73's
Arv
_._



Re: [AQRP] FW: Inexpensive capacitor measurements...

John Fisher <k5jhf@...>
 

Thanks a million, Monty, Great job. And thanks to Arv Evans for sharing
this circuit :-)


Regards,
John

=============================================
email: k5jhf@...
photos: http://photos.yahoo.com/k5jhf@...
files: http://briefcase.yahoo.com/k5jhf@...
webpage: http://www.geocities.com/k5jhf@...
callsign: K5JHF
=============================================

-----Original Message-----
From: Monty N5ESE [mailto:n5ese@...]
Sent: Friday, July 09, 2004 12:56 PM
To: John Fisher
Cc: AQRP
Subject: Re: [AQRP] FW: [BITX20] Inexpensive capacitor measurements...


Gang:

Here's an ASCII schematic to replace the missing GIF image in the
posting below. If it doesn't look right in your mail client, cut and
paste it into Notepad or your favorite word processor, and set the font
to courier or courier new.

I highly recommend that you install the 1000 pF calibration capacitor in
the circuit with a switch to switch it in and out as required, in case
your original "calibration" drifts. There are lots of things that can
affect measurement accuracy and stability in this circuit: line
frequency; line voltage changes; R1's potentiometer stability,
resolution and settability; your meter's linearity, and your meter's AC
input impedance.

A wall-wart (AC, not DC) would be an ideal transformer, comes pre-fused,
and keep you away from line voltages. A nominal 9 or 12 VAC wall-wart
would probably end up providing 15 VAC in this application.

Your $9 Harbor Freight Digital Voltmeter probably won't be very accurate
at low readings (say, below 100-150 pF), but try it and see.

By the way, you don't have to have exactly 1000pF for your cal
capacitor.
If you have something close, and you know what it is by virtue of its
tolerance or because you can measure it with a lab instrument at work,
that's good enough. For example, if it's a 1000pF NPO ceramic and you
know that its actual value is 1090 pF, adjust the pot so the meter reads
1.09 VAC. As another example, suppose you have a 2% 910 pF silver mica
- just adjust the pot so that the meter reads 0.91 VAC.

I wouldn't trust measurement readings below 50 or so pF very much...
stray capacitances in the layout, meter probes, and meter input
circuitry will begin to contribute significant errors as the capacitance
approaches lower values.

Still, it's a great little circuit!

73,
monty N5ESE

-----------------------------
Capacitance Measuring Circuit
-----------------------------
(view with monospace font like Courier)

Cx
__o-F-o__
) ________o---||---o_____
)|( |
)|( __________|
)|( 15 | |
115VAC )|( VAC &#92;|/ |
)|( R1 | |
)|(________/&#92;/&#92;/&#92;/&#92;_______|
) ^ ^
_________) | 180K (typ) |
| |
| ____ |
| | | |
|___| AC |___|
| VM |
|____|


I really like this BITX20 list on Yahoo groups. They're building up a
cheap rig and sending out great information :-)


Regards,
John

=============================================
email: k5jhf@...
photos: http://photos.yahoo.com/k5jhf@...
files: http://briefcase.yahoo.com/k5jhf@...
webpage: http://www.geocities.com/k5jhf@...
callsign: K5JHF
=============================================

-----Original Message-----
From: Arv Evans [mailto:arvevans@...]
Sent: Thursday, July 08, 2004 3:35 PM
To: bitx20@...
Subject: [BITX20] Inexpensive capacitor measurements...


Hi

Since Farhan's stated original intent in designing the BITX20 was to
provide an inexpensive transceiver, maybe it would be appropriate to
show BITX builders an inexpensive way to measure unmarked or
questionable capacitors. The following circuit came to me via Don
Metzger - K8JWR, but I suspect the method has been around for quite
some time. The picture shown here is the relatively simple schematic
for this tool.



Use a mains transformer that delivers a few ma. at about 15 volts RMS.
Connect a known .001 mfd capacitor at Cx and adjust the value of R1 (
for R1 I used a 250K trim pot salvaged from an old circuit card ) for
an indication of 1.000 volts on your DVM. Now you can measure
capacitor values from a few pf up to 0.001 mfd by connecting them in
the place of Cx.

I used this method to "calibrate" the knob indicator on a 3X450 pf
variable capacitor that I regularly use as part of my test equipment
repertoire. Now I just set the dip meter to the desired frequency,
and use the variable capacitor to tune my inductor for a dip on that
setting. Once the coil is on-frequency I can read the capacitance
from my calibrated variable capacitor and substitute that value of
fixed capacitance into the circuit.

Part of the fun derived from building your own ham radio equipment is
in devising ways to perform complex design and testing by use of
relatively simple and inexpensive methods & equipment. This idea fits
into that category.

73's
Arv
_._

Before someone asks the question...No, this circuit will not measure
electrolytic capacitors, but it will get you close enough for most of
the small caps you will be using in designing resonant circuits for HF
applications.
---------------------------------------------------------







Via the Austin QRP Club list
Yahoo! Groups Links







Via the Austin QRP Club list
Yahoo! Groups Links