Date   
Re: A tale of two tap washers...the saga goes on, an on

Arvid Evans <arvevans@...>
 

Sam & other BITXers

Your measurements explain my results then. Instead of tap/faucet
washers I used 1/4 inch slices cut from "1/2 inch" PVC pipe (the
schedule-40 or medium-thick-wall type). These measure about 13/16" OD
and 5/8" ID.
In my BITX20 I followed Farhan's instructions regarding the nunber of
turns and my coils came out nearly perfect for inductance value.

I just wound a second set of coils using the PVC material and
facilitated the winding process by cutting a slot in the plastic
former. This means I did not have to thread the wire through the core
150 times. These new coils check out on the dip meter as also being
on-the-money for inductance.

It is interesting that these "air-core" toroids exhibit some of the
same characteristics as ferrite cored units. My dip meter does not
get a strong coupling to the coil itself unless I add a coupling loop
through the core. I thought that phenomena was due to ferrite
channeling the magnetic field, but maybe the shape of the coil has
more influence than I thought.

Arv
_._
--- In BITX20@..., Sam Caldwell <samc@x> wrote:
Hans Summers wrote :

...in which G0UPL travels to his local hardware store to further
investigate
the nature of the infamous tap washers, and in particular the
differences
between ordinary and "delta" washers.
Both are know as 1/2 inch tap washers but both measure more than
1/2 inch
(12.7mm). As close as I can measure with my ruler:
As I understand it, the " half -inch' refers to the bore of the water
pipe with which they are associated - and includes three-quarter and
one-inch as part of the series.

A typical "half-inch" tap washer in the past would measure perhaps
three-quarters of an inch dia., but in more recent times the
proliferation of fancy bathroom ware has given rise to a variety of
custom taps (faucets) with their own washers.

My own houshold taps ( I'm told ) have ceramic washers which ( I'm
told ) never wear out and ( I know ) are drip-free.

Regards, Sam C.
ZL1TOI

Re: Chip pad

Hans Summers <Hans.Summers@...>
 

I was wondering how to make a pad for the chip then thought
use a piece of PCB with a cut through the copper in the centre
and then additional cross cuts of the copper to make the lands
for the holder.
That's what I do too, when I need to. I use firm pressure on one of those
cheap orange plastic "craft" knives. You can produce a nice thin cut with
this method. The LM386 in the BITX20 I just mounted "ugly" though, with no
pads. I tend to use the knife method if I need to use surface mount IC's.

The pinnacle of the art came when I found I had to connect a 24-pin Analogue
to Digital converter chip, in a TSSOP package. Pin spacing was a mere
0.65mm. In other words, 4 times denser than your BITX20 LM386. To do this I
cut 2 columns of 6 pads on either side of the IC (24 pads total). I glued
the IC to the board. The even-numbered pins (2, 4, 6 etc) were bent upwards
away from the board. Odd-numbered pins (1, 3, 5 etc) were soldered direct
onto the pads. The even-numbered pins were then connected to the outer
columns of pads using the hair-thin individual strands of copper from
ordinary lighting cable. You can find a picture of the result about 2/3 down
on the left hand side of this page
http://www.hanssummers.com/electronics/equipment/spectrumanalyser2/index.htm


People who work with SMD talk of special soldering irons & bits, special
solder, magnifying glass, flux, special lights etc etc. I used none of this.
Just my ordinary 18W Antex CS iron with 1mm bit and ordinary 22swg solder.
Just goes to show that the patient homebrewer can accomplish a lot even
without specialist equipment.

72/3 de Hans G0UPL

Re: Chip pad

g4dfv2004 <duncan.walters@...>
 

An easier method to make a pad for non-SMD IC's is to use 0.1"
Veroboard instead of plain copper laminate.
Then only one saw/knife cut is required.
KISS?

Duncan G4DFV

Re: Digital dial for BITX20 using PIC

Hans Summers <Hans.Summers@...>
 

A very nice readout. But for anyone wanting something *really* simple, have
a look at my 2-chip binary readout counter
http://www.hanssummers.com/radio/sfreq/index.htm . Also see my BITX20 in the
G0UPL photos folder to see it installed in my front panel.

My latest version is even simpler by using a 74HC390 instead of the
74HC4040, eliminating 5 diodes and 2 resistors from the circuit. The output
is also easier to read: 2 columns of LED's indicating 80, 40, 20, 10 and 8,
4, 2, 1KHz. This is easier to add up than the binary 64, 32, 16, 8, 4, 2, 1,
0.5Khz of my earlier versions. The reading is 0 - 99KHz, my dial is marked
14.0, 14.1, 14.2, 14.3 and this is added to the counter reading to get the
reception frequency. The 1KHz LED flickers such that it's brightness can be
used to estimate the frequency inside the 1KHz resolution.

Would anyone be interested if I were to offer a complete kit of parts (for
ugly construction, i.e. no PCB), suitable for connection to the BITX20 VFO
as in mine? The pack would include: 74HC4060, 74HC390, 5V voltage regulator
+ filter, 8x 3mm high-brightness red LED's, single transistor VFO buffer
amplifier, all diodes resistors and capacitors. Cost £3.37 + postage (as
usual, parts cost only, no profits for poor G0UPL). If enough people were
interested I could do this.

72/3 de Hans G0UPL

-----Original Message-----
From: vk3bfa [mailto:ablight@...]
Sent: 29 June 2004 01:56
To: BITX20@...
Subject: [BITX20] Digital dial for BITX20 using PIC


Hi fellow builders,
posting this link for information
http://www.wia.org.au/armag/2002/AR_Sept02_Digital_Freq_Display.pdf
- its a digital frequency readout using a PIC micro with user definable IF
offset - might be of use to the group, and I readily admit its outside
Ashan's original inexpensive transceiver concept - it would probably cost
more to build than the BITx20 itself! Still, I think its an elegant
solution, so let me know what you think. Its .PDF, approx 162K in size 73 de
VK3BFA Andrew

Re: Block Diagram

Mark <Mark@...>
 

Charles,

Where did you post it?

--- In BITX20@..., "Charles" <charles@d...> wrote:
Hi

I have just posted a block diagram of the BITX - I hope I have
correctly identified all the section of the main schematic diagram.

Let me know of any errors.

This will be used as part of a teaching aid to Amateur Radio
Students
in UK.


Charles

Re: Chip pad

Jim Strohm <jstrohm@...>
 

On Jun 29, 2004, at 3:31 AM, g4dfv2004 wrote:

An easier method to make a pad for non-SMD IC's is to use 0.1"
Veroboard instead of plain copper laminate.
Then only one saw/knife cut is required.
KISS?
And an even easier -- yet vastly more expensive -- method is to use one of the etched adapter boards that brings out the pins from a surface-mount chip to 0.1-in spacing pads. SMD chips can be soldered to these with little difficulty and a small iron as Hans noted. Nowadays I use a lighted magnifier -- even on DIP stuff -- because it's a lot easier on me.

And I have a cute little Intel Play USB microscope that has a 10X setting for the more challenging SMD stuff.

Jim N6OTQ

Inductors - RX Probs

Mark Jones <Mark@...>
 

Hi all

Looking for some help here.

Testing the RX today, AF amp clearly OK, the simple tests in the text work
out fine i.e. Touch base Q4 static, Q3 more static, Q2 less static. Trimmers
with L1,2 & 3 do little or nothing, but the trimmer in the T3 mixer has a
huge effect on noise out of the speaker. At either end of the travel very
loud.

It looks like there is no RF coming in. I have re-wound the two mixers with
no change, I'm wondering about the coils.

Here's what I have:

L1,2,3 22 turns 24 SWG on T-50-6
T1, T3 13 turns triffiliar 28 SWG on FT37-43

Any thoughts?

Mark Jones (G0MGX)
07971 091767

Re: Inductors - RX Probs

Jim Strohm <jstrohm@...>
 

On Jun 29, 2004, at 8:13 AM, Mark Jones wrote:

Here's what I have:

L1,2,3 22 turns 24 SWG on T-50-6
T1, T3 13 turns triffiliar 28 SWG on FT37-43

Any thoughts?
That wire is large enough that it should not have fractured within its enamel coating. For L1 - 3, an ohmmeter will confirm continuity.

For T1 and T3 -- this is worth asking -- did you use multi-colored wire for the trifilar winding to ensure proper connections and phasing? And did you check continuity before and after you soldered? A trifilar winding of #28 is much likelier to break without showing visible damage than the #24.

The only other possible cause I can think of is that the toroids are mis-marked and are so far from providing the right inductances as to make the circuit fail. If you can trust your supplier, this should not be a problem -- to test, use the mfg. data sheet to calculate inductance, place a 1 nF cap across the inductor's leads, and hit it with a dip meter. If it's a good toroid, it'll test within 10% of predicted inductance.

Jim N6OTQ

Re: Digital dial for BITX20 using PIC

John Fisher <k5jhf@...>
 

This is really Cool, 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: Hans Summers [mailto:Hans.Summers@...]
Sent: Tuesday, June 29, 2004 3:42 AM
To: 'BITX20@...'
Subject: RE: [BITX20] Digital dial for BITX20 using PIC


A very nice readout. But for anyone wanting something *really* simple, have
a look at my 2-chip binary readout counter
http://www.hanssummers.com/radio/sfreq/index.htm . Also see my BITX20 in the
G0UPL photos folder to see it installed in my front panel.

My latest version is even simpler by using a 74HC390 instead of the
74HC4040, eliminating 5 diodes and 2 resistors from the circuit. The output
is also easier to read: 2 columns of LED's indicating 80, 40, 20, 10 and 8,
4, 2, 1KHz. This is easier to add up than the binary 64, 32, 16, 8, 4, 2, 1,
0.5Khz of my earlier versions. The reading is 0 - 99KHz, my dial is marked
14.0, 14.1, 14.2, 14.3 and this is added to the counter reading to get the
reception frequency. The 1KHz LED flickers such that it's brightness can be
used to estimate the frequency inside the 1KHz resolution.

Would anyone be interested if I were to offer a complete kit of parts (for
ugly construction, i.e. no PCB), suitable for connection to the BITX20 VFO
as in mine? The pack would include: 74HC4060, 74HC390, 5V voltage regulator
+ filter, 8x 3mm high-brightness red LED's, single transistor VFO buffer
amplifier, all diodes resistors and capacitors. Cost £3.37 + postage (as
usual, parts cost only, no profits for poor G0UPL). If enough people were
interested I could do this.

72/3 de Hans G0UPL


-----Original Message-----
From: vk3bfa [mailto:ablight@...]
Sent: 29 June 2004 01:56
To: BITX20@...
Subject: [BITX20] Digital dial for BITX20 using PIC


Hi fellow builders,
posting this link for information
http://www.wia.org.au/armag/2002/AR_Sept02_Digital_Freq_Display.pdf
- its a digital frequency readout using a PIC micro with user definable IF
offset - might be of use to the group, and I readily admit its outside
Ashan's original inexpensive transceiver concept - it would probably cost
more to build than the BITx20 itself! Still, I think its an elegant
solution, so let me know what you think. Its .PDF, approx 162K in size 73 de
VK3BFA Andrew


Components, 2nd round

Hans Summers <Hans.Summers@...>
 

BITX'ers,

DEADLINE: 12:00 UTC THURSDAY 01-JUL-04 (TOMORROW!)

Paolo, Farhan and myself are investigating the possibility of a complete kit
of all parts for the project, including resistors, capacitors, variable
resistors, etc along with the previous semiconductors + crystals pack. This
will probably take a while to organise.

In the interim, I have received a request from Charles G4VSZ for 4 component
packs for himself and his club. I also have an outstanding request from Jim
N6OTQ. So this week I will run another round of component sourcing. The
components come mostly from Rapid Electronics because their prices are
excellent. The LM386 comes from Farnell, because then I can be sure that it
is the LM386N-1 variant, which is uncertain from Rapid. The 2N2219 comes
from Viewcom (http://www.viewcom.force9.co.uk/index.htm) and incurs some
postage fees which I have to add to their transistor price. The price is the
price of the components, no profit for G0UPL :-(

If more people order, the price will decrease slightly. Last time with 9
orders, it was £8.19 + £0.28 postage. At the present time with 5 orders, the
prices are:

£3.29 Qty 10 of 10.000 MHz crystals, HC49 style
£0.59 Qty 25 of BC547B transistors
£0.75 2N2219A driver transistor
£1.53 IRF510 MOSFET
£0.19 Qty 15 of 1N4148 diodes
£0.07 36V Zener diode
£0.05 9.1V Zener diode
£0.05 5.6V Zener diode
£0.29 LM386N-1 Audio Amp IC (correct variety)
£1.88 Qty 5 of 2-22pF trimmer capacitor
£0.71 Miniature tuning capacitor*

£9.68 total including £0.28 UK postage.

* NOTE: The tuning capacitor is one of the miniature kind as used in
portable radios. Size is 20.2 x 20.2 x 10.8mm. Control shaft is 6.6mm
diameter tapped with 2.6mm thread. Panel mounting is via twwo 2.6mm tapped
screws next to the control shaft. Capacitance: AM section 3.0 - 141.6pF,
Oscillator section 4.0 - 59.2pF. So in parallel you'd have 200pF which is
less than Farhan's design for 350pF. It might therefore be necessary to
alter the VFO coil to get the required tuning range.

Feel free to order extras of any item for spares, or exclude things you
don't want.

Any more orders?

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

10 MHz crystal matching

Heinz Schnait <oe5eep@...>
 

Hello,

I just measured the resonance frequency of ten 10 MHz crystals. I found a
set of four within 30 Hz and another set of four within 45 Hz.

How does this compare to other peoples results?

Did somebody already plot the passband shape of a resulting 4 crystal
filter?

73 Heinz, OE5EEP

Re: 10 MHz crystal matching

n3ted <tedkell@...>
 

--- In BITX20@..., Heinz Schnait <oe5eep@q...> wrote:
Hello,

I just measured the resonance frequency of ten 10 MHz crystals. I
found a
set of four within 30 Hz and another set of four within 45 Hz.

How does this compare to other peoples results?

Did somebody already plot the passband shape of a resulting 4 crystal
filter?
How do you do that? Figure out the shape that is?

Tnx

N3Ted


73 Heinz, OE5EEP

level and wave shape after balans mixer?

Chris van den Berg
 

Hi,
I build some parts of the transceiver and tested every part
individualy.
The LF parts works fine (a pitty the schematic is not corrected with
the voltage/output of the lm386). If I add a sinus LF wave to the
microphone terminal, the shape looks simular on the colector.
However, as soon as I connect the coil of the balans mixer to it, it
becomes a-symetrical (one side is going to be clipped).
If I put a lot of LF signal in it (looks heavily distorted, then I
get a maximum output(after the attenuater) of about 0.2 mw. (in 50
ohm). After reducing the LF signal to a point it looks normal, the
output power is very very less....
Did anyone look at the osciloscoop the way I did? Anyone measured
the output?
The distortion I can imagine can be caused by one of the diodes, but
such low output at that moment?
After the next amp (before the x-tal filter, the maximum output is
about 1 mw (in 50 ohm). The reason is that I measure in 50 ohm is
that the load is in the mw. meter.
Thanks in advance for your comments,
Chris PA3CRX

Re: level and wave shape after balans mixer?

Ashhar Farhan <farhan@...>
 

On Wed, 30 Jun 2004, vdberghak wrote:

The LF parts works fine (a pitty the schematic is not corrected with
the voltage/output of the lm386).
the correct schmatics are now at www.phonestack.com/farhan. i have run out
of bandwidth on http://farhan.net.co.nr. ther is no way i can access those
files now. just before i ran out of bandwidth, i did manage to put a
redirect on the home page. yo probably have te BITX20 page directly
bookmarked. which is why you are not being redirected to the new site.


If I add a sinus LF wave to the
microphone terminal, the shape looks simular on the colector.
However, as soon as I connect the coil of the balans mixer to it, it
becomes a-symetrical (one side is going to be clipped).
you need a 10mV signal at the base of the mic. this is usually too low to
be measured with an oscilloscope. your best bet is to actually connect a
mic and speak into it. if you can whistle (keeping your breath away from
the mic), it is a single tone-test. an extended 'aaaa' looks like a
three-tone test to me.

the other side is clipeed, because you note, the diodes in the mixer will
clamp the output through the attentuator. this is an expected behaviour.

If I put a lot of LF signal in it (looks heavily distorted, then I
get a maximum output(after the attenuater) of about 0.2 mw. (in 50
ohm). After reducing the LF signal to a point it looks normal, the
output power is very very less....
Did anyone look at the osciloscoop the way I did? Anyone measured
the output?
it is best to check the balanced modulator on its own first, without the
mic connected. you should be able to null the carrier at mid setting of
the preset and the 22pf trimmer. if that works, then you can move to the
audio stage.

typically, keeping the audio output of the mic amp connected to diode
modulator, you should see similar waveforms at the modulator input (where
the two transformer windings are shorted) and the output (the attentuator
pad) when using the oscilloscope at audio frequencies (keeping the time
base to about 10mSec per div).

as you have pointed out, the distortion is due to the non-linear nature of
the diodes. To measure the RF component alone, you should measure the
output through a hihg pass filter. for quick and dirty measurement,
connecte an RFC across the output of the attenuator and then connected the
oscilloscope.

if you have already made the crystal fitler, it is best that you measure
and check the signal at the output Q12 (without the RF mixer connected).
there is little that can go wrong in the Q12 and Q11. the only caveat is
that depending upon the exact frequency of the BFO, you might or might not
get SSB. If you are sitting in the middle of the filter's passband, you
will get DSB with audio roll-off at 1-2khz. but the enveolope will be
there to see.

have you tested the receiver yet? it is usually the recevier that comes
alive first. it gives you a good idea of how things are working.

i am convinced that we need to add detailed test measurements for the
transceiver on the site. i have most of them in my log book. i will post
them soon.

- farhan

The distortion I can imagine can be caused by one of the diodes, but
such low output at that moment?
After the next amp (before the x-tal filter, the maximum output is
about 1 mw (in 50 ohm). The reason is that I measure in 50 ohm is
that the load is in the mw. meter.
Thanks in advance for your comments,
Chris PA3CRX





Yahoo! Groups Links




Crystal filter passband shape

ashhar_farhan <farhan@...>
 

--- In BITX20@..., "n3ted" <tedkell@e...> wrote:

Did somebody already plot the passband shape of a resulting 4
crystal
filter?
How do you do that? Figure out the shape that is?
the shape is easy to figure out if you already know the crystal
parameters. the crystal parameters are easier to measure now thanks
to the G3UUR method. i have outlined it at
http://www.phonestack.com/farhan/xcvr1.html.

the essential idea is that a crystal filter looks like a capacitor
and an inductor in series (these are called motional capacitance and
motional inductance respectively). in addition to these, between the
leads of the crystal you will also be able measure a parallel
capacitance.

using the G3UUR method, you put each of the crystals into the
oscillator and measure its frequency. then you solder a 22pf or a
33pf in series with the crystal and measure the frequency shift. the
shift gives you a good approximation of the motional capacitance and
given the capacitance it is trivial to calculate the inductance
(given that we know the crystal's frequency). the parallel
capacitance is also approximated and the crystal is completely
modelled.

once you know the crystal parameters, you can spend a weekend
understanding the butterworth filter design. or you can use the
cookbook method in EMRFD like I did, or just use w7zoi program that
comes with his other book Introduction to RF Design.

using the my motional parameters, w7zoi did run it through his
program GPLA.exe and i have just uploaded the results to the
pictures folder.

i am including his comments that go with the picture below:
<snip>

The first file, ashhar01, part A, shows the
filter I designed with your motional L of 11.95 mH. I designed for
2200 Hz
bandwidth and a Butterworth response. Then the filter at part B
is a
more practical version of the same thing. It is much like the
filter that
you ended up building. My simulations suggest that is really is
worthwhile
to add the tuning capacitors at the ends though, for it produces a
much
smoother, ripple free response. The first analysis I did used
equal
terminations of 200 Ohms (perhaps 220) at each end and the response
was of
course text book. But the question remained -- what would the
response be
if the filter was terminated in other resistances. The file
ashhar02
shows what you get with a 50 Ohm source and a 200 Ohm load. This
is still
pretty good. The response is not nearly so good with 100 Ohms per
side,
which is about the characteristic Z0 of your amplifiers.

</snip>

- farhan

Re: level and wave shape after balans mixer?

Chris van den Berg
 

Thanks for the additional information.

the correct schmatics are now at www.phonestack.com/farhan.
I checked again http://www.phonestack.com/farhan/bitx.html and found
out that point 5 and 6 are stil wrong (not in accordance with the
data sheet, as noticed and posted by someone else).
I connected it correctly but an other person that follows the
schematic can have serious problems.
(if you make adjustments to your site, may be you can also add a
link to this yahoo group?).

The point is that I expected more output after the mixer. I am
always suspicious with that kind of coils (did I take the right one,
did I make the correct connections, is it really working the way it
should be) so I like to check something.

if you have already made the crystal filter, it is best that you
measure
and check the signal at the output Q12 (without the RF mixer
connected).
I will work on it today and add directly the next stages to
terminate the filter as good as possible. I hope the output will
then be incresed some more otherwise I do not end up with enough
power at the end (or am I pessimistic ;-) ).

have you tested the receiver yet? it is usually the recevier that
comes
alive first.
The receiver works, while connecting a wire to Q3 I hear a lot more
then with the wire connected to the mixer.

i am convinced that we need to add detailed test measurements for
the
transceiver on the site. i have most of them in my log book. i
will post
them soon.
In general, voltages can be checked easily to find out roughly that
the connections are correct and the correct values resistors are
mounted. Some general clues about what can be expected while
connecting a wire to a point or what voltage can be measured with
simple test gear would make it more complete indeed. May be current
with and without oscilator on (for every stage) will avoid the need
for more test equipment?
Adding too many measurement possibilities may be prevents a lot of
people building the design because they think it is all needed.
Doing the way you do now makes it important for everyone to
understand the circuit resulting in a higher level of radio
amateurs ;-)

Other builders comments?
Best regards,
Chris, PA3CRX

Re: level and wave shape after balans mixer?

Mark <Mark@...>
 

- farhan wrote:

i am convinced that we need to add detailed test measurements for the
transceiver on the site. i have most of them in my log book. i will
post them soon.

I would welcome test measurements - two days of head scratching so
far! The RX is alive in my rig but not yet kicking! I have a lot of
BFO audible in the output also I have had to bypass the xtal filter
and the band pass filter to get any signal strength.

I'll tell you all this story just for fun. I had no joy with the
band pass filter and nearly threw the rig out of the window. Then I
realised that when I had "made" 2.2 pm out of 5 x 10pf caps I had
them in parralel and not series! Oh boy, the basic mistakes!

I try some more tomorrow.

Mark G0MGX



--- In BITX20@..., "vdberghak" <vdberghak@z...> wrote:
Thanks for the additional information.

the correct schmatics are now at www.phonestack.com/farhan.
I checked again http://www.phonestack.com/farhan/bitx.html and
found
out that point 5 and 6 are stil wrong (not in accordance with the
data sheet, as noticed and posted by someone else).
I connected it correctly but an other person that follows the
schematic can have serious problems.
(if you make adjustments to your site, may be you can also add a
link to this yahoo group?).

The point is that I expected more output after the mixer. I am
always suspicious with that kind of coils (did I take the right
one,
did I make the correct connections, is it really working the way
it
should be) so I like to check something.

if you have already made the crystal filter, it is best that you
measure
and check the signal at the output Q12 (without the RF mixer
connected).
I will work on it today and add directly the next stages to
terminate the filter as good as possible. I hope the output will
then be incresed some more otherwise I do not end up with enough
power at the end (or am I pessimistic ;-) ).

have you tested the receiver yet? it is usually the recevier
that
comes
alive first.
The receiver works, while connecting a wire to Q3 I hear a lot
more
then with the wire connected to the mixer.

i am convinced that we need to add detailed test measurements
for
the
transceiver on the site. i have most of them in my log book. i
will post
them soon.
In general, voltages can be checked easily to find out roughly
that
the connections are correct and the correct values resistors are
mounted. Some general clues about what can be expected while
connecting a wire to a point or what voltage can be measured with
simple test gear would make it more complete indeed. May be
current
with and without oscilator on (for every stage) will avoid the
need
for more test equipment?
Adding too many measurement possibilities may be prevents a lot of
people building the design because they think it is all needed.
Doing the way you do now makes it important for everyone to
understand the circuit resulting in a higher level of radio
amateurs ;-)

Other builders comments?
Best regards,
Chris, PA3CRX

Re: 10 MHz crystal matching

Hans Summers <Hans.Summers@...>
 

I just measured the resonance frequency of ten 10 MHz
crystals. I found a set of four within 30 Hz and
another set of four within 45 Hz.

How does this compare to other peoples results?
Here are my measurements in ascending order:

9,994,677
9,994,704
9,994,733
9,994,747
9,994,799 0
9,994,811 +12
9,994,821 +22
9,994,829 +30
9,994,874
9,994,887

You can see the chosen 4, which are within 30 Hz. I wouldn't have been able
to match a second set within 45Hz.

Note: these frequency counter readings are on my homebrew frequency counter
(http://www.hanssummers.com/electronics/equipment/radiofreqcounter/intro.htm
) which is installed in my 80/40m receiver
(http://www.hanssummers.com/radio/polyphase/index.htm). Previously in 30m
QRSS beacon experiments (http://www.hanssummers.com/radio/qrss/index.htm) I
built a simple 30m direct conversion receiver
(http://www.hanssummers.com/radio/30m/index.htm) and calibrated the
frequency counter against the Moscow RWM timesignal on 9,996,000. My counter
was reading just over 1KHz too low at this frequency. So the measurements
above would need to be revised upwards by about 1KHz. But it's the relative
frequency which is important here anyway, and I haven't repeated the
calibration.


Did somebody already plot the passband shape of a
resulting 4 crystal filter?
How do you do that? Figure out the shape that is?
Farhan has spoken about theoretically determining the shape. I'd also like
to see experimental measurements. One way is to use a spectrum analyser with
tracking generator and very narrow bandwidths available. The filter shape
would appear directly on the screen. I built a spectrum analyser
(http://www.hanssummers.com/electronics/equipment/spectrumanalyser/index.htm
) and someday I will make a tracking generator, but not yet (too many other
projects).

When I have time, I indend to build another logarithmic amplifier using the
excellent (but expensive) AD8307 chip. Using this with a voltmeter to
measure the logarithmic output, a frequency counter and a 30m VFO it would
be possible to take a series of measurements of the filter attenuation at
different frequencies and plot the curve. The log amp on my spectrum
analyser can be seen here:
http://www.hanssummers.com/electronics/equipment/spectrumanalysertemp/logamp
/index.htm. You'll note that it's a very simple circuit. I think this will
provide a cheap way to obtain the passband curve.

72/3 de Hans G0UPL
http://www.HansSummers.com

Re: level and wave shape after balans mixer?

Charles Darley
 

Hi All
 
I rather agree with Mark - I have done a lot of construction in the past and the absence of such info takes a long time of searching for a fault.  AND It will make great testing and fault finding practice for my club members whilst I am building the project.
 
the question is how best to show it ...
 
I suggest a second schematic so that the first is used during construction and then the second during testing.  At the point where  a value wants to be put annotate with an arrow and letter and then list the information separately ..
 
Mark if you give me the info then I would happily try to do a suitable sheet and post it to the group fro discussion
 
Regards Charles
 
 

-----Original Message-----
From: Mark [mailto:Mark@...]
Sent: 01 July 2004 12:19
To: BITX20@...
Subject: [BITX20] Re: level and wave shape after balans mixer?

- farhan wrote:

i am convinced that we need to add detailed test measurements for the
transceiver on the site. i have most of them in my log book. i will
post them soon.

I would welcome test measurements - two days of head scratching so
far! The RX is alive in my rig but not yet kicking! I have a lot of
BFO audible in the output also I have had to bypass the xtal filter
and the band pass filter to get any signal strength.

I'll tell you all this story just for fun. I had no joy with the
band pass filter and nearly threw the rig out of the window. Then I
realised that when I had "made" 2.2 pm out of 5 x 10pf caps I had
them in parralel and not series! Oh boy, the basic mistakes!

I try some more tomorrow.

Mark G0MGX



--- In BITX20@..., "vdberghak" wrote:
> Thanks for the additional information.
>
> > the correct schmatics are now at www.phonestack.com/farhan.
> I checked again http://www.phonestack.com/farhan/bitx.html and
found
> out that point 5 and 6 are stil wrong (not in accordance with the
> data sheet, as noticed and posted by someone else).
> I connected it correctly but an other person that follows the
> schematic can have serious problems.
> (if you make adjustments to your site, may be you can also add a
> link to this yahoo group?).
>
> The point is that I expected more output after the mixer. I am
> always suspicious with that kind of coils (did I take the right
one,
> did I make the correct connections, is it really working the way
it
> should be) so I like to check something.
>
> > if you have already made the crystal filter, it is best that you
> measure
> > and check the signal at the output Q12 (without the RF mixer
> connected).
> I will work on it today and add directly the next stages to
> terminate the filter as good as possible. I hope the output will
> then be incresed some more otherwise I do not end up with enough
> power at the end (or am I pessimistic ;-)  ).
>
> > have you tested the receiver  yet? it is usually the recevier
that
> comes
> > alive first.
> The receiver works, while connecting a wire to Q3 I hear a lot
more
> then with the wire connected to the mixer.
>
> > i am convinced that we need to add detailed test measurements
for
> the
> > transceiver on the site. i have most of them in my log book. i
> will post
> > them soon.
>
> In general, voltages can be checked easily to find out roughly
that
> the connections are correct and the correct values resistors are
> mounted. Some general clues about what can be expected while
> connecting a wire to a point or what voltage can be measured with
> simple test gear would make it more complete indeed. May be
current
> with and without oscilator on (for every stage) will avoid the
need
> for more test equipment?
> Adding too many measurement possibilities may be prevents a lot of
> people building the design because they think it is all needed.
> Doing the way you do now makes it important for everyone to
> understand the circuit resulting in a higher level of radio
> amateurs ;-)
>
> Other builders comments?
> Best regards,
> Chris, PA3CRX


Bitx 20, Help me!

felipetanaweb <felipetanaweb@...>
 

Please I do not have the 10MHz crystals to make the filter, but I
have 5 pieces of 8MHz crystals with this 8MHz crystals is possible to
make the filter with new values of resistor and capacitor?And to
modify the Bitx20 to Bitx40 is only to modify the Band Pass filter
and de oscillator?Somebody has this modification?

Thanks!