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## Re: Probably a stupid question

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• Henk and Ian I think that Tony answered Jerry s original question quite adequately Also the follow ups suggested from Robby et al were FB from a practical
Message 1 of 13 , Nov 1, 2008
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Henk and Ian
I think that Tony answered Jerry's original question quite adequately
Also the follow ups suggested from Robby et al were FB from a
practical consructional standpoint.
However there are errors in both your theories.
First of all Henk is right in his assumption that if the two windings
were connected such that both starts were connected together and both
finishes were connected together (as would be the case in the event
that the hairpin was not cut and the other two free ends got shorted
together) then the two inductors would indeed be in parallel and
therefore would like his analogy with resistors MIGHT be expected to
behave accordingly, and the resultant measured value would be halved
and not remain the same as Ian has claimed.
Ian's explanation is flawed however for this in so much that it is
wrongly based on assuming that the two windings make electrical
contact throughout their winding length, which is not the case as
they are only joined at their extremities.
Both Henk and Ian have overlooked the effect of Mutual Inductance
which must be taken in consideration and which is most important with
Bifilar windings.
In an ideal situation the coupling will be such that the Mutual
Inductance M will equal the individual self inductance L for each
coil such that the apparent inductance of each coil is doubled and
appears to be 2L such that when connected in parallel they do indeed
appear to measure as L.
If we consider the case where both coils are arranged in series and
connected IN phase we see that the overall inductance becomes equal
to L + M + L + M, and since L = M, this equates to 4L or four times
the self inductance of one winding.
This supports the fact that the Inductance of a conventionally wound
coil is more nearly related to the SQUARE of the Number of turns
rather than just linearly proportional to their number
Also if when we get two bifilar coils connected in series but OUT of
phase theoretically we have no inductance at all, since (L+M)-(L+M)
=0 !
Hope this helps
Charles G3OTH

--- In softrock40@yahoogroups.com, "G3ROO" <ian.g3roo@...> wrote:
>
> Surely Henk.... the two inductors are wound on the same core so if
they are wire in parrallel they will only seem like a wire of thicker
diameter so the inductance will remain the same.
>
> If the wires were on different cores and then in parrallel then the
inductnace wouldbe halved.
>
> 73
>
> Ian
> ----- Original Message -----
> From: Henk Keppel
> To: softrock40@yahoogroups.com
> Sent: Friday, October 31, 2008 8:14 PM
> Subject: [softrock40] Re: Probably a stupid question
>
>
>
> Hi Jerry,
>
> it is not a stupid question because as I see you did not yet get
the answer on your question.
>
> If you keep the hairpin as one connection and you connect the two
loose ends together then you have two coils, connected in parallel,
resulting in half the inductance of each (just like resistors)
> If you "cross cconnect" them, i.e. cut the hairpin and connect
them in series by connecting one begin with the other end (measure
with an Ohmmeter).(Just as with resistors).
> The resulting inductance is the sum of both, or double the
inductance of one because the windings are exectely the same, better
the of you wound them single.
>
> success, Henk, PA0KEP
>
>
>
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• Having thought on this overnight, and for those of you following my drift. I realise I have shot myself in the foot by using that last quoted equation to
Message 2 of 13 , Nov 2, 2008
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Having thought on this overnight, and for those of you following my
drift. I realise I have shot myself in the foot by using that last
quoted equation to represent ideally wound mutually coupled bifilar
coils (where L=M) connected in series OUT of phase.
The equation representing this effect would be better expressed as (L-
M)+(L-M)=0
This then allows one to reduce the value of M to zero and end up with
a value of 2L, which would be the case for mutually non coupled coils.

As I am about to wind some bandpass filters for my Lite + USB Xtall
v9 later today I am going to try and measure some of their L values
etc as I go along.
I dont have access to a very accurate means of measurement for small
values of L but I should be able to confirm nevertheless the effects
of
M as described earlier.

In passing I see that both Tony and Robby in addition to giving core
dimensions, material type, AWG and turns data also quote values for L
for L100 and T100 primary but do not give a value for T100 secondary.
I wonder if there was any reason for not doing this, if so although
it might not serve any useful purpose it would be interesting to know
the reason why.

As it might be easier for me, and maybe others, to check the series
resonant frequency of C100 and L100 and parallel resonant frequency
of C101 and primary of T100 with say a GDO or similar I wonder if it
would be a good idea to know what values of these to aim for ?

When winding particularly for example L100 for the 160 meter band
should I aim for 1.863 MHz series resonance as derived from
reciprocal of 2pi root LC using given quoted values of 18.7 uH and
390 pF.
Similarly 1.797 MHz parallel resonance for C101 and T100 primary
using quoted values of 5600 pF and 1.4 uH and pro rata for other
bands ?
This technique might also help allow for some tolerance in the value
of caps fitted to the PCB.

For those of you familiar with using poles, zeroes and spice etc,
would my suggestions and simplifications using Tony's values be
justified, perhaps someone can advise me further if I should be
aiming for anything different ?

Thanks Charles G3OTH

> Also if when we get two bifilar coils connected in series but OUT
of
> phase theoretically we have no inductance at all, since (L+M)-(L+M)
> =0 !
> Hope this helps
> Charles G3OTH
>
>
> --- In softrock40@yahoogroups.com, "G3ROO" <ian.g3roo@> wrote:
> >
> > Surely Henk.... the two inductors are wound on the same core so
if
> they are wire in parrallel they will only seem like a wire of
thicker
> diameter so the inductance will remain the same.
> >
> > If the wires were on different cores and then in parrallel then
the
> inductnace wouldbe halved.
> >
> > 73
> >
> > Ian
> > ----- Original Message -----
> > From: Henk Keppel
> > To: softrock40@yahoogroups.com
> > Sent: Friday, October 31, 2008 8:14 PM
> > Subject: [softrock40] Re: Probably a stupid question
> >
> >
> >
> > Hi Jerry,
> >
> > it is not a stupid question because as I see you did not yet
get
> the answer on your question.
> >
> > If you keep the hairpin as one connection and you connect the
two
> loose ends together then you have two coils, connected in parallel,
> resulting in half the inductance of each (just like resistors)
> > If you "cross cconnect" them, i.e. cut the hairpin and connect
> them in series by connecting one begin with the other end (measure
> with an Ohmmeter).(Just as with resistors).
> > The resulting inductance is the sum of both, or double the
> inductance of one because the windings are exectely the same,
better
> the of you wound them single.
> >
> > success, Henk, PA0KEP
> >
> >
> >
> > ------------------------------------------------------------------
--
> ----------
> > I am using the Free version of SPAMfighter
> > We are a community of 5.5 million users fighting spam.
> > SPAMfighter has removed 9029 of my spam emails to date.
> > The Professional version does not have this message
> >
> >
> >
> > ------------------------------------------------------------------
--
> --------
> >
> > avast! Antivirus: Uitgaande bericht is niet besmet.
> >
> > Virus Gegevensbestand (VPS): 081031-0, 31-10-2008
> > Getest op: 31-10-2008 21:14:15
> > avast! auteursrecht (c) 2000-2008 ALWIL Software.
> >
> >
> >
> >
> >
> >
> > ------------------------------------------------------------------
--
> ----------
> >
> >
> >
> > No virus found in this incoming message.
> > Checked by AVG - http://www.avg.com
> > Version: 8.0.175 / Virus Database: 270.8.5/1757 - Release Date:
> 30/10/2008 14:35
> >
>
• I wound a toroid for L100 for the 160 meter Band Pass Filter for a Version 9.0 RX today using data supplied in the Files section by Tony and Robby Using the
Message 3 of 13 , Nov 3, 2008
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I wound a toroid for L100 for the 160 meter Band Pass Filter for a
Version 9.0 RX today using data supplied in the Files section by Tony
and Robby
Using the GDO technique proposed in my earlier message and with C100
(390pF) fitted to board I observed the following:

L100 wound with 66 turns (40 turns on first layer and remaining 26
turns on second layer) with 1 inch tails produced a sharp dip at
exactly 1.860 MHz
When I added an extra turn (67 in total) the resonant frequency
dropped 30 KHz to 1.830 MHz

These results using the data and parts supplied by Tony thus agree
very closely with calculations and predictions I made earlier based
on L100 being 18.7uH nominal

I have not had a chance yet to make and measure results for T100
primary but will post these later

In the meantime if anyone or those responsible for the design of
these filters can confirm the theoretical target design values of
pole and zero frequencies I would be obliged, so that I can compare
with these practical findings and tweek turns if necessary before I
permanently solder in

Incidently the value of nominal 390 PF capacitor as supplied in
Tony's kit was 387 pF on my general purpose cheap handheld (0 to 20
Henry and 0 to 200uF range) LCR meter but same meter gave a reading
of 23uH for the coil so as already stated earlier I would not like to
rely on it for uH measurements of this magnitude

Regards Charles G3OTH

> As I am about to wind some bandpass filters for my Lite + USB Xtall
> v9 later today I am going to try and measure some of their L values
> etc as I go along.
> I dont have access to a very accurate means of measurement for
small
> values of L but I should be able to confirm nevertheless the
effects
> of
> M as described earlier.
>
> In passing I see that both Tony and Robby in addition to giving
core
> dimensions, material type, AWG and turns data also quote values for
L
> for L100 and T100 primary but do not give a value for T100
secondary.
> I wonder if there was any reason for not doing this, if so although
> it might not serve any useful purpose it would be interesting to
know
> the reason why.
>
> As it might be easier for me, and maybe others, to check the series
> resonant frequency of C100 and L100 and parallel resonant frequency
> of C101 and primary of T100 with say a GDO or similar I wonder if
it
> would be a good idea to know what values of these to aim for ?
>
> When winding particularly for example L100 for the 160 meter band
> should I aim for 1.863 MHz series resonance as derived from
> reciprocal of 2pi root LC using given quoted values of 18.7 uH and
> 390 pF.
> Similarly 1.797 MHz parallel resonance for C101 and T100 primary
> using quoted values of 5600 pF and 1.4 uH and pro rata for other
> bands ?
> This technique might also help allow for some tolerance in the
value
> of caps fitted to the PCB.
>
> For those of you familiar with using poles, zeroes and spice etc,
> would my suggestions and simplifications using Tony's values be
> justified, perhaps someone can advise me further if I should be
> aiming for anything different ?
>
> Thanks Charles G3OTH
>
>
• ... From: g3oth ... This subject has been discussed in the past. The general conclusion was that there is no need to tweak these components. The bandpass is
Message 4 of 13 , Nov 3, 2008
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----- Original Message -----
From: "g3oth"
> In the meantime if anyone or those responsible for the design of
> these filters can confirm the theoretical target design values of
> pole and zero frequencies I would be obliged, so that I can compare
> with these practical findings and tweek turns if necessary before I
> permanently solder in
>

This subject has been discussed in the past. The general conclusion was that
there is no need to tweak these components. The bandpass is fairly wide,
small differences will make little change.

I do not think anybody has commented on the design parameters but using the
G4FGQ BPF calculator I find values agree for 50 ohms.
I have wondered whether fewer spurii may result from making narrow filters
for a single band. Then tweaking may be necessary.

73 Alan G4ZFQ
• ... Hi Charles, For all of the Softrock radios I build by the documented turns count. I do make some measurements of each toroid once wound just for a data
Message 5 of 13 , Nov 3, 2008
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> In the meantime if anyone or those responsible for the design of
> these filters can confirm the theoretical target design values of
> pole and zero frequencies I would be obliged, so that I can compare
> with these practical findings and tweek turns if necessary before I
> permanently solder in

Hi Charles,

For all of the Softrock radios I build by the documented turns count.
I do make some measurements of each toroid once wound just for a data
point in case I was to make a change later.

To verify the input filter/transformer I have found the best way is to
put a signal generator at the input and 50 load across the entire
secondary (ignor the center tap connection). This method avoids the
impedance shift (from 50 to 12.5 ohms) if only using 1/2 of the
secondary. This process works fine when the filter is not installed
in the radio.

For ease of measurements a Spectrum Analyzer with tracking generator
or a Network Analyzer is the best. I have posted in the files section
a sweep of the current Lite filters: KF4BQ >> SR LiteXTALL BPF.pdf

73, Mike Collins KF4BQ
• Hi Mike and Alan Many thanks for pointing out the existence of your files. It would seem from them that I have nothing much to worry about regarding the
Message 6 of 13 , Nov 3, 2008
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Hi Mike and Alan
Many thanks for pointing out the existence of your files.
It would seem from them that I have nothing much to worry about
regarding the toroids I have wound so far.
I was just interested to know whether or not the uH values shown in
Tony's files against core material colour, dimensions and turns etc.
had been derived a) theoretically direct from a network theory
standpoint or b) taken from core manufacturers typical inductance
data for the material, dimensions and turns, as listed or c) from
direct measurement of sample coils as used in the experimental
Bandpass filter prototypes.
If either b) or c) were the case then I realise all I have done is to
reconfirm such. If however the values of inductance quoted were
arrived at from idealised network theory then maybe my practical
measurements using simple equipment has been of use in showing that
18.7 uH is indeed the Bulls Eye to aim for, which together with the
390pF constant will produce a zero around 1.860 MHz which indirectly
could help others to validate their builds.
Now off to wind some more toroids !
Regards Charles G3OTH

--- In softrock40@yahoogroups.com, "Mike Collins" <mikecol@...> wrote:
>
> > In the meantime if anyone or those responsible for the design of
> > these filters can confirm the theoretical target design values of
> > pole and zero frequencies I would be obliged, so that I can
compare
> > with these practical findings and tweek turns if necessary before
I
> > permanently solder in
>
> Hi Charles,
>
> For all of the Softrock radios I build by the documented turns
count.
> I do make some measurements of each toroid once wound just for a
data
> point in case I was to make a change later.
>
> To verify the input filter/transformer I have found the best way is
to
> put a signal generator at the input and 50 load across the entire
> secondary (ignor the center tap connection). This method avoids the
> impedance shift (from 50 to 12.5 ohms) if only using 1/2 of the
> secondary. This process works fine when the filter is not installed
> in the radio.
>
> For ease of measurements a Spectrum Analyzer with tracking generator
> or a Network Analyzer is the best. I have posted in the files
section
> a sweep of the current Lite filters: KF4BQ >> SR LiteXTALL
BPF.pdf
>
> 73, Mike Collins KF4BQ
>
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