开云体育

Excellent page here not only provides the uncrippled Spectrogram for download but a noise generator and many other goodies as well.

73

Rahul VU3WJM

?

?

With the software and connecting the output of the AF amp to? PC, i wonder where do we set the BFO to find out the shape of our filter, assuming that we do not know the center frequency yet, or setting the BFO is not necessary?

rgds
julius

* REPLY SEPARATOR? *

On 7/20/2005 at 9:14 AM vdberghak wrote:

>Indeed measuring is knowing if the final result is in line with the
>original expectations.
>As mentioned before, it can be easily done with the sound card. At that
>time, I asked for feedback (screenshots of the same method) of measured
>filters to see if my 4,9 MHz filter is about in line with the 10 MHz
>version. If some members do this measurement it is possible to compare
>results and find out if it is really a 'lottery'. As I understand, most
>builders have their filter dimensioned in accordance with the original
>schematic and they all seems to work fine?
>OK builders, please download the few kb program, connect your BITX to
>the sound card, measure the shape of the filter and post the screendump!
>Thanks in advance,
>Chris.
>
>> Without measuring to get
>> good filter is more lottery than predictable result. Only in
>> situation that somebody can use the same type of crystals producer
>> and batch results might be comparable.
>
>
>
>
>
>
>
>Yahoo! Groups Links
>
>
>




?????

?????
????? ?????
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---

NEW - crystal clear PC to PC

In German Funkamateur was published schematic for hf noise generator
and described metod of mesurment by using sondcard lf spectogram. I
am sorry that it is again in russian but can be easily translated. I
couldnt find similar article in english. Schematics are
understandable on its own.




--- In BITX20@..., "vdberghak" <vdberghak@z...> wrote:

Indeed measuring is knowing if the final result is in line with

the

original expectations.
As mentioned before, it can be easily done with the sound card. At

that

time, I asked for feedback (screenshots of the same method) of

measured

filters to see if my 4,9 MHz filter is about in line with the 10

MHz

version. If some members do this measurement it is possible to

compare

results and find out if it is really a 'lottery'. As I understand,

most

builders have their filter dimensioned in accordance with the

original

schematic and they all seems to work fine?
OK builders, please download the few kb program, connect your BITX

to

the sound card, measure the shape of the filter and post the

screendump!

Thanks in advance,
Chris.

Without measuring to get
good filter is more lottery than predictable result. Only in
situation that somebody can use the same type of crystals

producer

and batch results might be comparable.

Allison

That URL for the MOSFET HF Amp is actually:



I wonder if anyone has ever tried a grounded-gate MOSFET linear...something
much like the grounded-grid valve type amps? I have no idea if it might
work, but it could be fun to try.

Arv K7HKL
_._

There are at least two or more designs using IRF510s in push
pull form. The power out was in the 30-45 watt range for two devices
running at 24V through 10M. This is reasonable for the class of
device. The real trick is as you go up in frequency (above 5mhz) you
need to pay attention to input and output matching. Failure to do so
will result in less power than expected. Also insure the driver is
both properly loaded and can deliver the required power.

Also testing these devices at RF find they exhibit poor IMD at 12V.
At 20-24V they perform much better.

Also to drive these properly the driver stage should easily be good
for 1watt. If any stage before the final amplifer or drivers cannot
deliver sufficient drive not only will power out suffer the signal
quality and bandwidth will be poor.

One of many articles using two IRF510:

home.cnham.com/pdf/amp/irf510/HF_use_FET_1.pdf

Allison
KB1GMX

--- In BITX20@..., Arv Evans <arvevans@e...> wrote:

Chris

My BITX40 uses 24 volts on the IRF510 for a power output of 11

watts. It

required the addition of separate sheilding, 2 ferrite beads on the

gate

lead, and a paracitic suppressor (2 ohm 2 watt carbon resistor wound

with 4

turns of #16 AWG) between drain and output filter to tame it.

If you have a variable power supply, try bringing the voltage up

slowly once

you have it working properly with 12 volts. I did not do this the

first time

and it cooked an IRF510! 8-(

My IRF510 is mounted on the heat sink for a computer CPU. The

original CPU

fan is mounted on the other side of the heat sink and turns on with

the PTT

controlled voltage for the IRF510. I bolted the IRF510 directly to

the heat

sink, which is mounted to the chassis via 1/2 inch (1.3 cm) nylon

standoffs.

The fan housing is plastic so this isolates it from RF on the heat sink.

Next step might be to replace the IRF510 with push-pull IRF510s or

IRF630s and

a 48 volt supply!

Arv K7HKL
_._


On Wednesday 20 July 2005 03:17 am, vdberghak wrote:

Hi all,
did anyone tried to put higher voltage on the IRF stage?
If so, I am interrested about the results like:
- stability,
- increase of output power.
If the output power is not much higher and other problems will

show up,

I will not try it...
Thanks,
Chris.




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With the software and connecting the output of the AF amp to PC, i wonder where do we set the BFO to find out the shape of our filter, assuming that we do not know the center frequency yet, or setting the BFO is not necessary?

rgds
julius

* REPLY SEPARATOR *

On 7/20/2005 at 9:14 AM vdberghak wrote:

Indeed measuring is knowing if the final result is in line with the
original expectations.
As mentioned before, it can be easily done with the sound card. At that
time, I asked for feedback (screenshots of the same method) of measured
filters to see if my 4,9 MHz filter is about in line with the 10 MHz
version. If some members do this measurement it is possible to compare
results and find out if it is really a 'lottery'. As I understand, most
builders have their filter dimensioned in accordance with the original
schematic and they all seems to work fine?
OK builders, please download the few kb program, connect your BITX to
the sound card, measure the shape of the filter and post the screendump!
Thanks in advance,
Chris.

Without measuring to get
good filter is more lottery than predictable result. Only in
situation that somebody can use the same type of crystals producer
and batch results might be comparable.

Yahoo! Groups Links

___________________________________________________________
Gesendet von Yahoo! Mail - Jetzt mit 1GB Speicher kostenlos - Hier anmelden:

Hi Chris,

Thanks for your answer. As you can see in my reply to Allison I will
follow your advices.

With you I hope that more pictures of the filtershape will be
dropped it in this group. The arguments Max gave in his reply makes
more clear to me that a filter design have to be checked by measuring
the result.

On the moment I am still working on the 9MHz filter The first part of
the design (2nd order test filter and calculating new C's and
impedance) worked well. In 4 steps I came to desired bandwith, all
pictures are saved so the process can be followed.
Now I have two things to do:
1. Match te impedance of the filter to the amplifierstages.
2. See how the calculated C's does work out on a 4th order filter.
When there are results I will drop them in this group.

In "RF Amplifier Classics", 1-10 there is a design with two IRF510 in
push-pull on 28 V giving over 40W with 1 W drive. Mail me if you want
a copy of the article.

73

Ruud (PE2BS)





--- In BITX20@..., "vdberghak" <vdberghak@z...> wrote:

Hi Ruud,
as I remember, you asked for a solution in the circuit, by using

other

resistors.
I kept the circuit 'original' and added very small transformers,
pictures can be seen in the BITX17 Photos directory.
I did many experiments with several values of components, did many
measurements (by soundcard) so the differences can be seen easily

(as

you know, but other may not).
Best regards,
Chris.

Doing the measurements I noticed that matching the impedance is

very

important for the filtershape. Changing the C's makes great

impedance

changes. (33 pF, R= 328 Ohm, C=76 pF, R= 142 Ohm on the 2nd order
test filter) That's why I asked some information about matching

the

impedance in the amplifierstages in the BITX20 (msg 868). I am

still

waiting for a reply....

Chris

My BITX40 uses 24 volts on the IRF510 for a power output of 11 watts. It
required the addition of separate sheilding, 2 ferrite beads on the gate
lead, and a paracitic suppressor (2 ohm 2 watt carbon resistor wound with 4
turns of #16 AWG) between drain and output filter to tame it.

If you have a variable power supply, try bringing the voltage up slowly once
you have it working properly with 12 volts. I did not do this the first time
and it cooked an IRF510! 8-(

My IRF510 is mounted on the heat sink for a computer CPU. The original CPU
fan is mounted on the other side of the heat sink and turns on with the PTT
controlled voltage for the IRF510. I bolted the IRF510 directly to the heat
sink, which is mounted to the chassis via 1/2 inch (1.3 cm) nylon standoffs.
The fan housing is plastic so this isolates it from RF on the heat sink.

Next step might be to replace the IRF510 with push-pull IRF510s or IRF630s and
a 48 volt supply!

Arv K7HKL
_._

Hi Allison,

Thank you for answering my questions. I understand that changing the
amplifier stage is not a good idea: variabels are depending on each
other and calculate the impedence is not easy.
I will follow yours and Chris' suggestion and will match the filter
to the amplifierstages by rf transformers.

73

Ruud
PE2BS

--- In BITX20@..., "ajparent1" <kb1gmx@a...> wrote:

--- In BITX20@..., "Ruud Jongeling" <pe2bs@t...> wrote:

Hello fellow BITX'ers,

Because I want do do some experiments with a ladderfilter on 9

MHz, I

studied the amplifier stage Asshar discribed and used in his

BITX20.

I have some questions about it.

- I understand that the input and output impedance depends on the
resistors Rf and Re: Rf*Re=Rout*Rin. In the exemple with Rf=1000,
Re=10 and Rin=50, Rout becomes 200. But what happens if the

input

is 100? There will be a mismatch but where will it be? Is the

output

impedance fixed because of Rload (220 in the schema) and will be

the

mismatch at the input of the amplifierstage?

The putput impedence is affected by both the load resistor and
feedback resistor value. Mismatch under 1:2(2:1) is resonable
for thos application.

- I studied the ladderfilter theory and different C's means

different

input and output impedance of the filter. How to match the

amplifier

to these impedances? Witch resistors do I have to change for the
exemple of 100? How to calculate them?

- The last question is about the two amplifier stages around the
ladderfilter. Left of the filter the emittor resistance is 220.

Right

of the filter the emittor resistance is 470. The other resistors
around Q2 and Q3 are the same.Why is this? Does this has anything

to

do with matching the impedance?

The resistors you refer to set bias not impedence. The resistors in
series with capacitors (typical value 10 ohm) are the Re value that
set impedence. The input impedence (first order) is Re * (Beta/F)
[beta/F is the first order AC beta{current gain of transistor} at RF
frequency] and that will be in parallel the base bias resistor and
depressed further by the Feedback resistor. Changing Re and

changing

Rfb both alter gain and input as well as output impedence. As you

go

up in input impedence the range of values tends to be limited and
circuit stability decreases.

Actually I prefer to set the amplifier impedence and use either an

L

network (C-L) or a RF transformer of the ferrite loaded type. For a
small sacrifice in gain a series or parallel resistor at the input

and

output of the filter may also be used.

Allison
KB1GMX

Hi all,
did anyone tried to put higher voltage on the IRF stage?
If so, I am interrested about the results like:
- stability,
- increase of output power.
If the output power is not much higher and other problems will show up,
I will not try it...
Thanks,
Chris.

Indeed measuring is knowing if the final result is in line with the
original expectations.
As mentioned before, it can be easily done with the sound card. At that
time, I asked for feedback (screenshots of the same method) of measured
filters to see if my 4,9 MHz filter is about in line with the 10 MHz
version. If some members do this measurement it is possible to compare
results and find out if it is really a 'lottery'. As I understand, most
builders have their filter dimensioned in accordance with the original
schematic and they all seems to work fine?
OK builders, please download the few kb program, connect your BITX to
the sound card, measure the shape of the filter and post the screendump!
Thanks in advance,
Chris.

de 4N1ZM

I was looking in different designs of ssb trx and it looks like that
most important part is exactly filter. And that is place where
successful work of trx can easy fail. Crystals are simply different
from producer to producer from lot to lot. Without measuring to get
good filter is more lottery than predictable result. Only in
situation that somebody can use the same type of crystals producer
and batch results might be comparable.

One other approach is Kohn type filter with all same capacitance
values that can be trimmed by variable c or varicaps in the section.
That one looks most permissible and easy try without much work.

Here is link to collection of all ladder filter approaches:



You should fist get djvu viewer from

By the way djvu format is the most efficient for schematics size on
the net, even in comparison to pdf.




--- In BITX20@..., "Max" <m_orwell@y...> wrote:

de 4N1ZM

There is two programs and alternative aproach to ladder filter

design.

Since altavista translation can overcame language bariers it is
possible to check this link through systran translation engine.
Program give obvious relation between impedance capacitance and
crystal unit mesurmen tools:




--- In BITX20@..., "ajparent1" <kb1gmx@a...> wrote:

That is a good starting point but I'd add much has been published
since then on building crystal filters.

Using the series ladder design and the right constants you can

build

USB and LSB filters as well as symetrical. A good source is the

ARRL

publication Experimental Methods in RF Design which devotes a

fair

amount of text to crystal filters and has a good listing of

citings

for further reference.

I've use their techniques to build excellent filters using 6 and

8

crystals with symetrical shapes to greater than 70db and low

ripple.

The gausian to 6db shape happens to sound the best to me for

2.2khz

SSB filters. I'm using a 6 crystal version of same in the first
version of BITx I've built as an transverter IF.

Allison
KB1GMX

--- In BITX20@..., Ron Brink <pa2rf@y...> wrote:

Thanks for the good info dear Allison,

Yes, in the meantime I discovered MOSFET IRF's are not most

favourable candidates for a 6 m PA. The 2SC Japanes transistors are
more common and most likely much easier to use.

A line up of 2n4124, 2sc1970 and a pair of 2sc1971 will do
9-11W CW power at 12V nominal.

About the synthesizer circuitry, in the past I have used a divider

4059 in combination with a 4046.

If after the VFO a hi-speed divider (e.g. 74F74 or U256) is used you

can go up to the GHz range and have a rockstable vfo.

That is certainly one way to go. Another is to use the 4046 phse
comparator in a 1:1 tracking loop with the reference being a VFO in
the 1-4mhz range.

Myself I build PLLs using chips like the MM55104, MC145106 and
MSM5807. Most of these are designed for 10khz challening used in US
CB radio but are easy to apply, found in junk radios and CMOS.
My preferd chip is the MC145106. Using those in a loop has a
twist. The divide by N counter in most maxes at 255 (255*10khz is
only 2.55mhz). This would imply a limited ability to do PLL in
the 40mhz range however there are easy ways around it. The most
common is to mix the VCO with a local crystal osc (better yet a VXO)
and have the result end up on the 1-2mhz range for counting. Then
the /n counter set the channel step and if you use the VSO you
can get interpolation between 10khz channels. One the base design
is worked out (copied from CB rig) scaling to any LO is easy as the
loop is the same and only the VCO and VXO is moved to suit. If built
carfully with good shielding and ground plane the 10khz spurs should
be at least 70db down. Since noise is related to the /n value this
scheme tends to be cleaner than those using a VHF counter. The side
effect is tuning range is limited to /n in the range of 10 to 255
or about 2.4mhz. I've built several using those chips and I package
them in a box of PCB material around 1.75" square and about .75" tall.
usual power consumed is under 60ma @5v. I have one I've built already
for upcomming Bitx-6.

Oh for tuning the pll without a micro. Take a 27c256 or similar
Eprom and program is so the address lines take 2 or 3 BCD coded
switches and translate that to a binary code at the output to suit.
The processis static and requires no clock (no cpu noise!) and is low
power.

My bitx-6 is progressing well. One of the design goals is to fit
it in a box 5Wx2Hx7D (inches) without headset, mic and DC power.
power ouput goal is in the 3-5W (cw power) range using 2SC1971.


Allison
KB1GMX

--- In BITX20@..., "Ruud Jongeling" <pe2bs@t...> wrote:

Hello fellow BITX'ers,

Because I want do do some experiments with a ladderfilter on 9 MHz, I
studied the amplifier stage Asshar discribed and used in his BITX20.
I have some questions about it.

- I understand that the input and output impedance depends on the
resistors Rf and Re: Rf*Re=Rout*Rin. In the exemple with Rf=1000,
Re=10 and Rin=50, Rout becomes 200. But what happens if the input
is 100? There will be a mismatch but where will it be? Is the output
impedance fixed because of Rload (220 in the schema) and will be the
mismatch at the input of the amplifierstage?

The putput impedence is affected by both the load resistor and
feedback resistor value. Mismatch under 1:2(2:1) is resonable
for thos application.

- I studied the ladderfilter theory and different C's means different
input and output impedance of the filter. How to match the amplifier
to these impedances? Witch resistors do I have to change for the
exemple of 100? How to calculate them?

- The last question is about the two amplifier stages around the
ladderfilter. Left of the filter the emittor resistance is 220. Right
of the filter the emittor resistance is 470. The other resistors
around Q2 and Q3 are the same.Why is this? Does this has anything to
do with matching the impedance?

The resistors you refer to set bias not impedence. The resistors in
series with capacitors (typical value 10 ohm) are the Re value that
set impedence. The input impedence (first order) is Re * (Beta/F)
[beta/F is the first order AC beta{current gain of transistor} at RF
frequency] and that will be in parallel the base bias resistor and
depressed further by the Feedback resistor. Changing Re and changing
Rfb both alter gain and input as well as output impedence. As you go
up in input impedence the range of values tends to be limited and
circuit stability decreases.

Actually I prefer to set the amplifier impedence and use either an L
network (C-L) or a RF transformer of the ferrite loaded type. For a
small sacrifice in gain a series or parallel resistor at the input and
output of the filter may also be used.

Allison
KB1GMX

Hi Ruud,
as I remember, you asked for a solution in the circuit, by using other
resistors.
I kept the circuit 'original' and added very small transformers,
pictures can be seen in the BITX17 Photos directory.
I did many experiments with several values of components, did many
measurements (by soundcard) so the differences can be seen easily (as
you know, but other may not).
Best regards,
Chris.

Doing the measurements I noticed that matching the impedance is very
important for the filtershape. Changing the C's makes great

impedance

changes. (33 pF, R= 328 Ohm, C=76 pF, R= 142 Ohm on the 2nd order
test filter) That's why I asked some information about matching the
impedance in the amplifierstages in the BITX20 (msg 868). I am still
waiting for a reply....

--- In BITX20@..., "Ron" wrote:
> Hi fellow BITX-homebrewer,
> Yesterday I was browsing through some old "Electrons" (Dutch Ham
> magazine) and found an interesting article in which it was told that
> our famous MOSFET IRF-family (in particular IRF510 and IRF540) could
> work on 50 MHz ! I am surprised by this. The article did not show
> fixed designs, so maybe it is just wishfull thinking...
> According to the article, achievable power levels should less lower
> than at, let's say 7 MHz ( 2 Watts versus 12 Watts RF).
> Anybody experience in this field ?

To drive the input of the mosfet at 6M you will have to use very
different networks so the input capacitance can be absorbed into the
network.? Same would have to be done for output.? Major redesign
of the "linear module" is the result.? I've tried the IRF510 and
friends and they can generate fair power at 6m but they are hard to
drive and not as stable.? Devices like the 2SC1307, 2sc799, 2sc1970
and 2sc1971 are easier to use and fairly common (found in 27,mhz
US CB radios). Power out with those can be as high as 10W.

> However, with an IF of 10MHz, VFO freq of 40MHz might be too high to
> get a (simple) rock-stable VFO.

The easiest way to get a 40mhz VFO is to take a 4mhz VFO and mix it
with a 36mhz crystal and filter the result to 40mhz.? then you get the
stability of 4mhz VFO and the required high frequency.

I'm doing it with whats called a sampling tracking PLL.?? Simpler
than a full digital PLL and somewhat less trouble with spurs and
sidebands. Tuning between the digital steps is by varying the VXO
used in the down conversion osc.? It allows me to use older PLL
chips that have /n counter that only count to 255 or maybe 512.


Allison
KB1GMX

---

Yahoo! Mail
Stay connected, organized, and protected.

Allison, & others...

Since the time constant in an H&P (Huff and Puff) stabilizer is usually much
longer than that of a traditional PLL, a PIC-based H&P design might be quite
easy to implement. I wonder about the posibility of using the PIC H&P as a
slow tuning PLL-like unit where the PIC would control frequency over the full
tuning range. With such a design the operator might enter a frequency via
the keypad and the PIC would take over and slowly tune the VFO to the
requested frequency. "Slow" here being a relative term that could be quite
fast if a lookup table were employed for gross settings of the DC offset for
particular frequencies.

One big advantage of using a PIC for frequency display is that VFO offsets are
easy to accomodate (i.e. the display can show the operating frequency,
although the actual VFO may be on some other frequency as in superheterodyne
designs). This also works for LSB-CW-USB offsets of the BFO frequency.

This use of a PIC (or any other micro-controller) as a H&P control element is
something that might be best discussed in the context of the Huff & Puff VFO
forum at <>.

Arv K7HKL
_._

Within the base ladder filter topology there are subgoups of type.
They can designed as minimum loss, butterworth, linear phase or
Chebychev not unlike LC filters. Each has it's differences and
sailent characteristics. When designing any of these filter the
meaurement of the crystals used is important for the result to be
close to the design prediction. Measurement includes frequency,
motional L, motional C, holder C and Q. All interact. Using 4
crystals of the same type and frequency does not assure the builder
the expected result though usually it will be close. Once the
crystals are known and a design selected the termination impedence
will also be a factor. That is one design criteria, the filters
sensitivity to termination.

When I select crystals from a group of the same lot I often find
besides frequency variation some units that have significantly
different Q [usually inferior] to the rest of the lot. The
variations can be as great as 3:1. An inferior crystal such as
that will be acceptable in an oscillator but would degrade a filter
if used in one.

While this is not meant to be exhaustive by any means. It helps
explain why theory and result will be dissimilar.


Allison
KB1GMX

--- In BITX20@..., Jim Strohm <jstrohm@e...> wrote:

On Jul 10, 2005, at 7:04 AM, Ashhar Farhan wrote:

while PLL chips are difficult to find, the 16F84 or the 16F628 are
plentiful. why can't we program the PIC to behave as a PLL on it's
own?

the PIC timer can be used to accurately measure the oscillator
frequency
(as normal PIC based frequency counters do) instead of displaying the
frequency on a display, it can (in addition) also pump a capacitor
that
in turn is used to bias a varactor across the VFO.

if chris and his merry band can do a single chip HnP, there is no
need to
assume that they can't turn out a single mirochip PLL too.

Given how cheap a PIC is, I think it's just a matter of time before
we stop using standard TTL/CMOS logic, and start programming PICs as
replacements. They won't be pin-for-pin replacements, but they'll be
easier to locate than some of the more esoteric logic chips.

A PIC PLL sounds like a fabulous project.

Jim N6OTQ

Three things:

PIC is a sequential device, there are whole classes of logic solutions
that are not easily done with a sequential device.

Using the PIC as a PLL, it could be done but even the fastest parts
are far too slow to be succiciently precise. With PLLs a lack of
precision can be causes noise in the signal. The core of most PLLs
is the phase detector which is usually a very fast sequential logic
element to in real time compare the phse of two signals. Hard to do
well enough with a PIC.

Using a PIC for HnP and display, this is very do able.

Allison
KB1GMX

Hi Paul and Max,

Thanks for your info about the design of a ladderfilter. The
ladderfilter was subject in this group before. Building the BITX20 I
made a shape of the ladderfilter with the program SpectrumAnalyzer
(see also msg 460: "Shape of Ladderfilter easy to measure" by Chris
v.d. Berg). I noticed some differences between the theory and the
actual shape of the filter, see the pictures in the Photo-box and the
messages about them.

From Chris I received an article from G3JIR in QST nov. 80 about
Ladder Filter Design. A copy is dropped in the Files-box. The filters
discribed looks like the filters in the Russian program Max put in
the File-box. I am working on a 9MHz filter following the steps G3JIR
discribed. With the SpectrumAnalyzer it is not difficult to measure
the bandwith of the filters and Excel can calculate the impedance of
the filters and the C's in the filters.

Doing the measurements I noticed that matching the impedance is very
important for the filtershape. Changing the C's makes great impedance
changes. (33 pF, R= 328 Ohm, C=76 pF, R= 142 Ohm on the 2nd order
test filter) That's why I asked some information about matching the
impedance in the amplifierstages in the BITX20 (msg 868). I am still
waiting for a reply....

When I completed the design of the filter I will drop the info in the
Files-box and the shape pictures Photo-box. I hope you will drop
pictures of your filtershapes too.

73

Ruud.






--- In BITX20@..., "Max" <m_orwell@y...> wrote:

de 4N1ZM

I added older easier for understanding version of ladder filter
desingn program in file section under 4N1ZM folder.

--- In BITX20@..., "Max" <m_orwell@y...> wrote:

de 4N1ZM

There is two programs and alternative aproach to ladder filter

design.

Since altavista translation can overcame language bariers it is
possible to check this link through systran translation engine.
Program give obvious relation between impedance capacitance and
crystal unit mesurmen tools:




--- In BITX20@..., "ajparent1" <kb1gmx@a...> wrote:

That is a good starting point but I'd add much has been

published

since then on building crystal filters.

Using the series ladder design and the right constants you can

build

USB and LSB filters as well as symetrical. A good source is

the

ARRL

publication Experimental Methods in RF Design which devotes a

fair

amount of text to crystal filters and has a good listing of

citings

for further reference.

I've use their techniques to build excellent filters using 6

and

8

crystals with symetrical shapes to greater than 70db and low

ripple.

The gausian to 6db shape happens to sound the best to me for

2.2khz

SSB filters. I'm using a 6 crystal version of same in the

first

version of BITx I've built as an transverter IF.

Allison
KB1GMX

Yes Paolo,
I'm a memeber of this list and just for this reason I discovered this good
RTX and decided to show to other italian Hams... hi!

Best 73

Alex I0SKK




-----Messaggio originale-----
Da: BITX20@... [mailto:BITX20@...] Per conto di
Paolo Cravero as2594
Inviato: venerdì 8 luglio 2005 9.05
A: BITX20@...
Oggetto: [BITX20] Article about BITX20 on Italian magazine

Hi,
I just discovered that a series of 4 articles about BITX20 has been
published on the Italian magazine "RadioKit Elettronica" (03/2005 to
06/2005):






Unfortunately I am not a reader of this magazine, so I totally missed
the article and can't comment.

I wonder: is the author subscribed to this list?!?!?!?

73,
Paolo IK1ZYW

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