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Hello, BITXs!!

I'm sorry but the modification by Allison doesn't work in my dual band
BITX (15 and 20meters). It makes great white noise in the receiver.
Without the modification the noise is little and the band sound is
good. After the modification the white noise is loud and the band
sound is muffled.

I test also to add another coil to the ring diodes mixer. But this
modification don't make diference aparently. The band sound and
sensibility remain unchanged.

I am working in an dual conversion BITX, after the "disaster" of 32MHz
FI due to the bidirectional amplifier feedback configuration I work in
a dual conversion. First FI 32MHz, second FI 10MHz. The mixers are
identical ring diodes based, the oscilator is 12MHz cheap and easy to
source. I want to mantain the bidirectional architecture. I will use a
bidirectional amplifier made up of dual gate mosfets and resonating
coils for 32MHz.

I will post the result of works and schematic. I will like to make VHF
with this configuration.

Greetings
I got my all band ticket!!
EA7ARX, ex EB7HPM/EC7ALV

Good old PSP was the tool.

Finally got DIA to crack using gunzip with no shortage
of complaints, installed it and it crashed hard after
looging a long list of errors. Apprently it has a lot
of dependancies on MS products. The system here is NT4
with SP6A but NO MS loaded products including OE and IE.
Its' a security thing.

I'll hunt around for a decent too to eiter convert the DXF
files from cadd6 or maybe a different cadd tool that really
works for schemtaic capture.

I have more schematics comming but I need a better tool
for the PC environment.

Allison
KB1GMX

Allison

Thanks for posting the schematic of your BITX modulator modification.
With the different languages and varying skill levels involved in the
BITX forum, sometimes a picture or schematic is necessary for all to
understand the more technical aspects of some design & construction
activities.

Arv K7HKL
_._

-

I posted a file to the KB1GMX folder as a quick jpeg of
the modulator turned around. It isn't pretty but saves
guessing.

Allison

Dia was a dud, could not get a file that would unzip from any of the
hosts.

The other two are really poor for schematic capture. I found the
libraries more suited to digital design. I'll keep Eagle around for
digital stuff. For analog that has lots of passives like trifilar
transformers, forget it.

I'd forgotten how horrid PC based schematic capture tools are.
Last one I used a lot was CADD6 (G-cadd) I have that but the
files are not easily viewed without cadd or autocadd. Microcadd
was easier to use but didn't run well under NT but is decent on
a simple dos machine wich also limits portability as you need
microcadd to view files (it's a really small program).

Much too much time spent on this already. I may just take paintshop
and tweek and existing image.

Allison
KB1GMX

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

Allison

All can produce posting quality files. I usually use "Dia" and set

it to

make .png (Portable Network Graphics) output. You have to save a

copy in

native .dia format first, then "export" the drawing and set the file

type to

".png" or ".jpg" as desired.

There are examples of Dia produced schematics on my web sites
<www.k7hkl.webhop.net> and <www.qrp.webhop.net>. There are also

some Dia

built schematics at BITX20/FILES/K7HKL/...

Arv
_._

On Friday 29 July 2005 09:36 am, ajparent1 wrote:

Ok, Looks good which one produced the most usable output
for posting?

Afterall I can post gerber files and vectorlists but they are
hardly easily seen.


Allison
KB1GMX

--- In BITX20@..., Arv Evans <arvevans@e...> wrote:
> Allison
>
> Free Schematic CAD software that should run on your Microsoft

NT-4.x

can be

> obtained via the following URLs:
>
>
>
>
>
>
>
> All of these sites provide freeware schematic drawing software for

windows

> (and for Linux) that would be suitable to use in drawing a partial

schematic

> for the changes you have made in the BITX design. Of these three,

EagleCAD

> from CadSoft is probably the closest to a professional CAD program,

but the

> other two are certainly adequate and may be easier to learn.
>
> And...Yes, there are other schematic drawing programs available.

These are

> just the ones that I know about and use frequently.
>
> Arv K7HKL
> _._
>
> On Thursday 28 July 2005 09:52 pm, ajparent1 wrote:
> > The best I can do would be jpeg photo of hand drawn paper page.
> > Even that takes some effort as only one PC supports USB and this
> > is not that one. All my schematic capture cadd stuff runs on
> > VAX/VMS and is generally incompatable with PCs.
> >
> > I may add the change is not very big. I just turned the circuit
> > around to reverse the LO and IF ports. The transformer T3 feed
> > IF and Q9 feeds the balance pot through the .1uF cap.
> >
> > If there is a prefered PC schematic capture I may investigate
> > but it must run under NT4 on a slow machine as this box is
> > generally accessable.
> >
> > Allison
> > KB1GMX
> >
> > --- In BITX20@..., Arv Evans <arvevans@e...> wrote:
> > > Allison
> > >
> > > Would it be possible for you do a quick schematic of the

changes and

> > store it
> >
> > > in the FILES section of this forum? That way it will be

available

> >
> > for others
> >
> > > who might not understand all that was changed from just

the textual

> > > description.
> > >
> > > Thanks,
> > >
> > > Arv K7HKL
> > > _._
> > >
> > > On Thursday 28 July 2005 09:20 pm, ajparent1 wrote:
> > > > One of the things I didn't like in the 20m proto BITX

I'd built

> > > > was the presence of audio getting into the IF amp on

transmit and IF

> > > > noise in to the audio on recieve. I'd gone the route of

adding an

> > > > 47uh RF choke from the intersection of the balance pot

wiper to

> >
> > ground
> >
> > > > which helped greatly. However, it always bothered me.
> > > >
> > > > So I opened it up and tried a design change that I find

pleasing and

> > > > also elimiates a number of components. As an engineer I'm

the sort

> > > > that looks at a design and says "what if..?". The

solution was

> > > > staring me in the face and also eliminates the PI

attenuator

as well.

> > > > The change is to turn the balanced modulator around and

feed

the IF

> > > > in on the transformer and RF (bfo) in at the balance

potentiometer

> > > > via the .1uf capacitor. This eliminated the need for the 3

resistors

> > > > and the rf choke. I noted cleaner modulation, less RX

noise

and more

> > > > gain available in both RX and TX.
> > > >
> > > > Might as well add this mod to the collection. I plan

to use

this

> > > > mod in the 6M version.
> > > >
> > > > Allison
> > > > KB1GMX
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > > SPONSORED LINKS
> > > >
> > > > Craft hobby
> > > > Hobby and craft supply
> > > > Ham radio
> > > >
> > > >
> > > > Hobby supply
> > > > Ham radio outlet
> > > > Ham radio sales
> > > >
> > > >
> > > >
> > > > YAHOO! GROUPS LINKS
> > > >
> > > >
> > > > Visit your group "BITX20" on the web.
> > > >
> > > > To unsubscribe from this group, send an email to:
> > > > BITX20-unsubscribe@...
> > > >
> > > > Your use of Yahoo! Groups is subject to the Yahoo! Terms of

Service.

> > YAHOO! GROUPS LINKS
> >
> >
> > Visit your group "BITX20" on the web.
> >
> > To unsubscribe from this group, send an email to:
> > BITX20-unsubscribe@...
> >
> > Your use of Yahoo! Groups is subject to the Yahoo! Terms of

Service.

YAHOO! GROUPS LINKS


Visit your group "BITX20" on the web.

To unsubscribe from this group, send an email to:
BITX20-unsubscribe@...

Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.

Allison

All can produce posting quality files. I usually use "Dia" and set it to
make .png (Portable Network Graphics) output. You have to save a copy in
native .dia format first, then "export" the drawing and set the file type to
".png" or ".jpg" as desired.

There are examples of Dia produced schematics on my web sites
<www.k7hkl.webhop.net> and <www.qrp.webhop.net>. There are also some Dia
built schematics at BITX20/FILES/K7HKL/...

Arv
_._

Ok, Looks good which one produced the most usable output
for posting?

Afterall I can post gerber files and vectorlists but they are
hardly easily seen.


Allison
KB1GMX



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

Allison

Free Schematic CAD software that should run on your Microsoft NT-4.x

can be

obtained via the following URLs:







All of these sites provide freeware schematic drawing software for

windows

(and for Linux) that would be suitable to use in drawing a partial

schematic

for the changes you have made in the BITX design. Of these three,

EagleCAD

from CadSoft is probably the closest to a professional CAD program,

but the

other two are certainly adequate and may be easier to learn.

And...Yes, there are other schematic drawing programs available.

These are

just the ones that I know about and use frequently.

Arv K7HKL
_._



On Thursday 28 July 2005 09:52 pm, ajparent1 wrote:

The best I can do would be jpeg photo of hand drawn paper page.
Even that takes some effort as only one PC supports USB and this
is not that one. All my schematic capture cadd stuff runs on
VAX/VMS and is generally incompatable with PCs.

I may add the change is not very big. I just turned the circuit
around to reverse the LO and IF ports. The transformer T3 feed
IF and Q9 feeds the balance pot through the .1uF cap.

If there is a prefered PC schematic capture I may investigate
but it must run under NT4 on a slow machine as this box is
generally accessable.

Allison
KB1GMX

--- In BITX20@..., Arv Evans <arvevans@e...> wrote:
> Allison
>
> Would it be possible for you do a quick schematic of the

changes and

store it

> in the FILES section of this forum? That way it will be available

for others

> who might not understand all that was changed from just the textual
> description.
>
> Thanks,
>
> Arv K7HKL
> _._
>
> On Thursday 28 July 2005 09:20 pm, ajparent1 wrote:
> > One of the things I didn't like in the 20m proto BITX I'd built
> > was the presence of audio getting into the IF amp on

transmit and IF

> > noise in to the audio on recieve. I'd gone the route of

adding an

> > 47uh RF choke from the intersection of the balance pot wiper to

ground

> > which helped greatly. However, it always bothered me.
> >
> > So I opened it up and tried a design change that I find

pleasing and

> > also elimiates a number of components. As an engineer I'm

the sort

> > that looks at a design and says "what if..?". The solution was
> > staring me in the face and also eliminates the PI attenuator

as well.

> > The change is to turn the balanced modulator around and feed

the IF

> > in on the transformer and RF (bfo) in at the balance

potentiometer

> > via the .1uf capacitor. This eliminated the need for the 3

resistors

> > and the rf choke. I noted cleaner modulation, less RX noise

and more

> > gain available in both RX and TX.
> >
> > Might as well add this mod to the collection. I plan to use

this

> > mod in the 6M version.
> >
> > Allison
> > KB1GMX
> >
> >
> >
> >
> >
> >
> >
> > SPONSORED LINKS
> >
> > Craft hobby
> > Hobby and craft supply
> > Ham radio
> >
> >
> > Hobby supply
> > Ham radio outlet
> > Ham radio sales
> >
> >
> >
> > YAHOO! GROUPS LINKS
> >
> >
> > Visit your group "BITX20" on the web.
> >
> > To unsubscribe from this group, send an email to:
> > BITX20-unsubscribe@...
> >
> > Your use of Yahoo! Groups is subject to the Yahoo! Terms of

Service.

YAHOO! GROUPS LINKS


Visit your group "BITX20" on the web.

To unsubscribe from this group, send an email to:
BITX20-unsubscribe@...

Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.

Allison

Free Schematic CAD software that should run on your Microsoft NT-4.x can be
obtained via the following URLs:







All of these sites provide freeware schematic drawing software for windows
(and for Linux) that would be suitable to use in drawing a partial schematic
for the changes you have made in the BITX design. Of these three, EagleCAD
from CadSoft is probably the closest to a professional CAD program, but the
other two are certainly adequate and may be easier to learn.

And...Yes, there are other schematic drawing programs available. These are
just the ones that I know about and use frequently.

Arv K7HKL
_._

The best I can do would be jpeg photo of hand drawn paper page.
Even that takes some effort as only one PC supports USB and this
is not that one. All my schematic capture cadd stuff runs on
VAX/VMS and is generally incompatable with PCs.

I may add the change is not very big. I just turned the circuit
around to reverse the LO and IF ports. The transformer T3 feed
IF and Q9 feeds the balance pot through the .1uF cap.

If there is a prefered PC schematic capture I may investigate
but it must run under NT4 on a slow machine as this box is
generally accessable.

Allison
KB1GMX
--- In BITX20@..., Arv Evans <arvevans@e...> wrote:

Allison

Would it be possible for you do a quick schematic of the changes and

store it

in the FILES section of this forum? That way it will be available

for others

who might not understand all that was changed from just the textual
description.

Thanks,

Arv K7HKL
_._

On Thursday 28 July 2005 09:20 pm, ajparent1 wrote:

One of the things I didn't like in the 20m proto BITX I'd built
was the presence of audio getting into the IF amp on transmit and IF
noise in to the audio on recieve. I'd gone the route of adding an
47uh RF choke from the intersection of the balance pot wiper to

ground

which helped greatly. However, it always bothered me.

So I opened it up and tried a design change that I find pleasing and
also elimiates a number of components. As an engineer I'm the sort
that looks at a design and says "what if..?". The solution was
staring me in the face and also eliminates the PI attenuator as well.
The change is to turn the balanced modulator around and feed the IF
in on the transformer and RF (bfo) in at the balance potentiometer
via the .1uf capacitor. This eliminated the need for the 3 resistors
and the rf choke. I noted cleaner modulation, less RX noise and more
gain available in both RX and TX.

Might as well add this mod to the collection. I plan to use this
mod in the 6M version.

Allison
KB1GMX







SPONSORED LINKS

Craft hobby
Hobby and craft supply
Ham radio


Hobby supply
Ham radio outlet
Ham radio sales



YAHOO! GROUPS LINKS


Visit your group "BITX20" on the web.

To unsubscribe from this group, send an email to:
BITX20-unsubscribe@...

Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.

Allison

Would it be possible for you do a quick schematic of the changes and store it
in the FILES section of this forum? That way it will be available for others
who might not understand all that was changed from just the textual
description.

Thanks,

Arv K7HKL
_._

One of the things I didn't like in the 20m proto BITX I'd built
was the presence of audio getting into the IF amp on transmit and IF
noise in to the audio on recieve. I'd gone the route of adding an
47uh RF choke from the intersection of the balance pot wiper to ground
which helped greatly. However, it always bothered me.

So I opened it up and tried a design change that I find pleasing and
also elimiates a number of components. As an engineer I'm the sort
that looks at a design and says "what if..?". The solution was
staring me in the face and also eliminates the PI attenuator as well.
The change is to turn the balanced modulator around and feed the IF
in on the transformer and RF (bfo) in at the balance potentiometer
via the .1uf capacitor. This eliminated the need for the 3 resistors
and the rf choke. I noted cleaner modulation, less RX noise and more
gain available in both RX and TX.

Might as well add this mod to the collection. I plan to use this
mod in the 6M version.

Allison
KB1GMX

Hi,

2mw is very low from the driver. Mine I see nearly 1mw at the output
of the bandpass filter (L1, L1,L3). The driver stage brings that up
to near 300mW on mine. I don't use the IRF510 as the output is more
than sufficient to drive a TenTec 1208 transverter at 100mW,
1mW however was not adaquate. Driver transistor used on mine was
2N2219A with bifilar transformer wound on a 2 hole core of -43
material to match 50 ohms. Without the 5db output attenuator it
measures as 3.8V rms across 50 ohms which is actually 288.8mW using
a HP rf voltmeter. Thats close enough to 300mW.

If you are using a trifilar transformer on the driver and measure
the power to the IRF then the driving impedence is around 10-12 ohms
and a 50ohm power meter will be inaccurate. Even then I'd expect
to see about 1.7-1.9V of rf at that point.

In any case 300mV is invalid. The gate of IRF needs to be driven
with several volts of RF to develop expected power without instability.

On mine the Q14 (predriver) device is 2N2222A and driver is 2N2219A
both have FT ratings of 350mhz which is adaquate to get good gain at
14mhz.

Measurements at the output of the filter (at 50ohms) is .9-1mw.
After Q14 I get 40mW. Adding the driver brings that to 300mW.
I used ferrite loaded transformers at T1, t2 and T3 as well as
collector of 2n2219A. Also added a choke coil (DC return) at RF
mixer (100uh molded type) and at modulator. Transistors used
are Q1,Q13,Q7 are 2n2222A, Q2,3,12,11,9,8,10 are all 2n3904.
This version uses a different VFO (Hartly with fet buffer).
All circuits are bypssed with more than shown is schemtic
and some sections are shielded (modulator and bfo). Construction
is dead bug (ugly on ground plane OF unetched PCB).

A newer version is being built that will use a PLL to provide LO
and the output will be for 6m using 9.6mhz filter, 40mhz LO and
I may try commercial DBM (anzac MD108) for both modulator and
mixer. Since this one is to be small power will be limited to
around 3-5W and use a RF transistor 2sc1971 for the final.

More information than asked for but, measurements are how I know
a circuit does indeed perform as expected.

Allison

Hi Milarepa,
based on my measurements, it is only a few mw, so the oposite of
what Allison measured.
I searched for you in the older postings (I have often the feeling
that older messages are not red) and you can find my answer in
message 375 (containing a mistake) and 387.
Good luck,
Chris.

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

Based on my proto 300mW is correct. If there were 300mV the power
would be about 2mW which is way to little.

Allison
KB1GMX


--- In BITX20@..., "MILAREPA" <MILAREPA@T...> wrote:

Dear forum,
I have read somewhere from the posting messages that the output

of pre

driver should be about 300 mWatts,
but I read from the article it should be about 300 mVolts.
Which is right ?
-------
I begin to test the tx section,
rx section test is good in 3.5; 7; 10; 14 MHz.
-------
Thanks.

Based on my proto 300mW is correct. If there were 300mV the power
would be about 2mW which is way to little.

Allison
KB1GMX

Folks
I am working from the (c)2004 circuit on Ashar's web page and have very low
output from PA. I am using cheap general purpose transistors (ME4003) and
changed pre-driver for 2N2222. Better but still only about 1W out.
I have used a very similar PA in the TCF transceiver by VK3XU and it works
fine. That is on 40m though.
I have read through previous postings and applied mods by Chris, PA3CRX.
I now have full 6W output. Well done Chris!
I see Ashar has adopted the trifilar transformer and the extra 200pF capacitor
in his simple dual band transceiver design. Is there a definitive revision,
or is it a case of 'suck it and see'?
73, Steve, G0FUW


___________________________________________________________

Book yourself something to look forward to in 2005.
Cheap flights -
Bargain holidays -

Dear forum,
I have read somewhere from the posting messages that the output of pre
driver should be about 300 mWatts,
but I read from the article it should be about 300 mVolts.
Which is right ?
-------
I begin to test the tx section,
rx section test is good in 3.5; 7; 10; 14 MHz.
-------
Thanks.

Hi Chris,

Rather than guess at Gautams question it is easy to ask. Saves
giving multiple conflicting answers.

I may add my favorite "cheap" Varactor [tuning] diode is 1n4007
rectifier. It also makes a fair substitute for a PIN diode
in switches and attenuators. Not as good as the real thing but
far less cost.


Allison
KB1GMX

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.
>
>
>
>
>? YAHOO! GROUPS LINKS
>
>
> ?Visit your group "BITX20" on the web.
> ?
> ?To unsubscribe from this group, send an email to:
> ?BITX20-unsubscribe@...
> ?
> ?Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.

---

How much free photo storage do you get? Store your holiday snaps for FREE with Yahoo! Photos.

Gautam

I am assuming that you are using the same size VFO inductor and capacitors as
specified by Farhan. If you are using the original design with the 36V zener
diode as a VFO fine tuning capacitor, you might try a different diode. They
do not all show the same capacitance value or range. If this does not work,
it is possible to use other diodes in place of the zener. My BITX20 uses a
Red LED as the tuning diode.

It is possible that you have connected the tuning diode using the wrong
polarity. Try reversing it to see what the results might be.

Since the tuning diode contributes only 10 pf, it can be disconnected
temporarily and the VFO tested without it.

If you do not have a way to measure capacitance, the value of your variable
capacitor can be measured using the simple capacitance test circuit shown in
<>. This
might help to verify that your tuning capacitor is really 365 pf. With the
capacitor completely open it should measure less than 20 pf.

Arv K7HKL
_._

--- In BITX20@..., kumar gautam <fromgautam@y...> wrote:

Hello,
In my bitx20 BFO shows 9.995 MHz. and in VFO section when i add 2j

gang capacitor my VFO shows 4.000 to 4.180 MHz(when trimmer shifted to
4.000MHz) and after tuning Trimmer(shifted to 4.150MHz) it shows 4.180
to 4.410Mhz.

After trying various type of variable capacitors i coul'd not find

entire range i.e. 4.000 to 4.400MHz.

Kindly help me in this regard i.e.
1. what is the exact frequency of BFO.

Varies depending on the crystal filter characteristics. Ideally
it should be tuned to 300hz down the lower frequency edge (assuming
upper sideband) of the filter slope. To do that precisely you have
to know the filter shape. The alternate way is to listen to good
signals and start with the bfo low and tune it up for natural
sounding recieve signal. Then there may be some fine tuning of the
BFO once you have a QSO for best TX sound.

2. What modification should i do for correcting the VFO.

Try fewer turns on VFO coil. The tuning diode the 22pf capacitor
connected to the tuning diode may need a slight increase in value.

also could i connect T1,T2 and T3 legs in any direction or it is

coneected in any direction.

?? I am not certain what you are asking.

Allison
KB1GMX