Date   
New file uploaded to BITX20

BITX20@...
 

Hello,

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

File : /VU2ESE/Q-measurement and apps.pdf
Uploaded by : ashhar_farhan <farhan@...>
Description : W7ZOI's Q measurement experiments for BITX coils

You can access this file at the URL:
http://groups.yahoo.com/group/BITX20/files/VU2ESE/Q-measurement%20and%20apps.pdf

To learn more about file sharing for your group, please visit:
http://help.yahoo.com/l/us/yahoo/groups/original/members/web/index.htmlfiles

Regards,

ashhar_farhan <farhan@...>

Re: bitx v3

Sunil Lakhani <freedomworld123@...>
 

--- In BITX20@..., "st2nh" <st2nh@...> wrote:

I want to buy bitx v3 pcb
The email of Mr. Sunil doesn't working -i.e. - suillakhani123@
gmail.com
Any more info, email, link
tnx-73
Nader, st2nh
Dear Nader,
You can find links on my blog http://www.cqbitx.blogspot.com
for Bitx Kits and some other items.
73's
Sunil VU3SUA

Re: Bandpass Filter - TX LPF 2nd harmonic trap

Ashhar Farhan <farhan@...>
 

i have investigated this and posted about it a few weeks ago. The
bandpass filter used in the original BITX is entirely 'shapeless'. It
was designed ad-hoc without any consideration at all, except that it
'works'. Apparently it doesn't do it's job.

I have measured 6b losses at the RF filter as per my original design.
In investigating it, W7ZOI also ran some tests measuring our tap
washer toroid Qs and trying to design bandpass filters. I am posting
his writeup in the files section as soon as I am done with this email.

The net sum is this ... download the AADE's filter design software and
punch in the values of our inductors available at hand to arrive at a
butterworth filter. Put in approximately those values of capacitors
and you are on your way. You need to be able to tune either the
inductors or the capacitors of course, to peak it correctly.

- farhan

On Sat, May 31, 2008 at 9:01 AM, n7ve <dan.Tayloe@...> wrote:
A second harmonic trap in a TX low pass filter is easy to do. I
worked out the math once, and it turns out you take a standard low
pass filter, and multiply the inductance of one of the series
inductors by 75%, and then calculate the C needed to resonate the 75%
at twice the frequency.

The way the math works out, the 75% percent inductor in parallel with
the 2xf parallel resonating cap "looks" like a 100% inductor at the 1x
frequency.

Thus, we have what appears to be a 100% inductor at 1x the frequency,
and with the parallel cap, looks like an open circuit at 2x the frequency.

Neat stuff that can be applied to any low pass filter.

- Dan, N7VE

--- In BITX20@..., "Jim Tonne" <tonne@...> wrote:


Mark:

The 11 MHz filter of course does not change
according to the band you are moving to. It appears
to be a Butterworth design. Since it is so narrow
(relatively) the component Q values are controlling the
shape at the top. It would be inappropriate to say
that this is a particular family (Butterworth, etc.). By
the way, an item of significance here is to pass the
SSB signal while attenuating some other stuff and have
a reasonably-low loss at 11 MHz. The family is so
irrelevant.

I found some time to reverse-engineer what Farhan had
done to create the input/output lowpass filter, which
DOES change according to the band you are moving
to..

(For the 20-meter design) it appers to be a 17 MHz
Butterworth lowpass which has had a part added to
form a "trap" at 29 MHz. This is a very reasonable
design technique although not optimum.

I do not have toroid-winding capability (no toroids
being the reason) and so the values I used for circuit
analysis are as follows:

Input termination 50 ohms
Output termination 50 ohms
From the amplifier side:
First shunt C to ground (C47) 200 pF
Inductor L2 .5758 uH
Second shunt C to ground (C48) 360 pF
Inductor L1 .43405uH
Final shunt C to ground (C49) 200pF

The harmonic at 28 MHz is down very far indeed.
The harmonic at 42 MHz is down 42 or more.
Higher harmonics are even further down, about
6 dB per octave.

To move this filter from 14.1 MHz to another
frequency, merely multiply the component values
(shown above) appropriately. To go to a 10-meter
design, for example, half the capacitors and halve
the inductors.

- Jim Tonne WB6BLD

P.S. to the BTX guys: do we need an appnote
about this?

Re: Bandpass Filter - TX LPF 2nd harmonic trap

n7ve <dan.Tayloe@...>
 

A second harmonic trap in a TX low pass filter is easy to do. I
worked out the math once, and it turns out you take a standard low
pass filter, and multiply the inductance of one of the series
inductors by 75%, and then calculate the C needed to resonate the 75%
at twice the frequency.

The way the math works out, the 75% percent inductor in parallel with
the 2xf parallel resonating cap "looks" like a 100% inductor at the 1x
frequency.

Thus, we have what appears to be a 100% inductor at 1x the frequency,
and with the parallel cap, looks like an open circuit at 2x the frequency.

Neat stuff that can be applied to any low pass filter.

- Dan, N7VE

--- In BITX20@..., "Jim Tonne" <tonne@...> wrote:


Mark:

The 11 MHz filter of course does not change
according to the band you are moving to. It appears
to be a Butterworth design. Since it is so narrow
(relatively) the component Q values are controlling the
shape at the top. It would be inappropriate to say
that this is a particular family (Butterworth, etc.). By
the way, an item of significance here is to pass the
SSB signal while attenuating some other stuff and have
a reasonably-low loss at 11 MHz. The family is so
irrelevant.

I found some time to reverse-engineer what Farhan had
done to create the input/output lowpass filter, which
DOES change according to the band you are moving
to..

(For the 20-meter design) it appers to be a 17 MHz
Butterworth lowpass which has had a part added to
form a "trap" at 29 MHz. This is a very reasonable
design technique although not optimum.

I do not have toroid-winding capability (no toroids
being the reason) and so the values I used for circuit
analysis are as follows:

Input termination 50 ohms
Output termination 50 ohms
From the amplifier side:
First shunt C to ground (C47) 200 pF
Inductor L2 .5758 uH
Second shunt C to ground (C48) 360 pF
Inductor L1 .43405uH
Final shunt C to ground (C49) 200pF

The harmonic at 28 MHz is down very far indeed.
The harmonic at 42 MHz is down 42 or more.
Higher harmonics are even further down, about
6 dB per octave.

To move this filter from 14.1 MHz to another
frequency, merely multiply the component values
(shown above) appropriately. To go to a 10-meter
design, for example, half the capacitors and halve
the inductors.

- Jim Tonne WB6BLD

P.S. to the BTX guys: do we need an appnote
about this?

Re: Low receive audio?

john_kb7nrn <johnandlorna@...>
 

A 1mv signal into the antenna jack? That's overdriving it just a little
don't you think?

--- In BITX20@..., "Leonard" <bitx@...> wrote:


I tested the 2 boards that I have today and if I inject 1mv rms into
the antenna jack, both had a 1.12 volt pk-pk signal at the hot lead
of
the volume control.

http://golddredgervideo.com/kc0wox/bitxkitsigtrace/rx1mvin.jpg
Leonard

Re: Low receive audio?

john_kb7nrn <johnandlorna@...>
 

I just read Leonard's post about his Receive Waveforms page and printed
it out. Will go through the receiver again and see if I can pin point
the problem now.

Thanks Leonard!

John
KB7NRN


--- In BITX20@..., "john_kb7nrn" <johnandlorna@...> wrote:

I have my Bitx20A kit built up to the receiver. I've been doing a few
tests because the recovered audio seems a bit low. When I apply a
20uv
14mhz signal at C11 I get about 5mv pp recovered audio from the AF
amp.
I can actually hear a 5uv 14mhz signal in the head phones but can't
read it on my scope.

I've been through the receive chain but can't seem to locate a
problem.

Should I be getting more recovered audio? What have others found on
their reciver?

John
KB7NRN

Re: Low receive audio?

Leonard <bitx@...>
 

--- In BITX20@..., "Leonard" <bitx@...> wrote:

--- In BITX20@..., "john_kb7nrn" <johnandlorna@> wrote:

I have my Bitx20A kit built up to the receiver. I've been doing a
few
tests because the recovered audio seems a bit low. When I apply a
20uv
14mhz signal at C11 I get about 5mv pp recovered audio from the
AF
amp.
I can actually hear a 5uv 14mhz signal in the head phones but
can't
read it on my scope.

I've been through the receive chain but can't seem to locate a
problem.

Should I be getting more recovered audio? What have others found
on
their reciver?

John
KB7NRN
I tested the 2 boards that I have today and if I inject 1mv rms
into
the antenna jack, both had a 1.12 volt pk-pk signal at the hot lead
of
the volume control.

Leonard

That should have read between 1.12 volts and 2 volts. It's difficult
to measure the small input voltages.
Leonard

Re: Low receive audio?

Leonard <bitx@...>
 

--- In BITX20@..., "john_kb7nrn" <johnandlorna@...> wrote:

I have my Bitx20A kit built up to the receiver. I've been doing a few
tests because the recovered audio seems a bit low. When I apply a
20uv
14mhz signal at C11 I get about 5mv pp recovered audio from the AF
amp.
I can actually hear a 5uv 14mhz signal in the head phones but can't
read it on my scope.

I've been through the receive chain but can't seem to locate a
problem.

Should I be getting more recovered audio? What have others found on
their reciver?

John
KB7NRN
I tested the 2 boards that I have today and if I inject 1mv rms into
the antenna jack, both had a 1.12 volt pk-pk signal at the hot lead of
the volume control.

http://golddredgervideo.com/kc0wox/bitxkitsigtrace/rx1mvin.jpg
Leonard

Low receive audio?

john_kb7nrn <johnandlorna@...>
 

I have my Bitx20A kit built up to the receiver. I've been doing a few
tests because the recovered audio seems a bit low. When I apply a 20uv
14mhz signal at C11 I get about 5mv pp recovered audio from the AF amp.
I can actually hear a 5uv 14mhz signal in the head phones but can't
read it on my scope.

I've been through the receive chain but can't seem to locate a problem.

Should I be getting more recovered audio? What have others found on
their reciver?

John
KB7NRN

bitx v3

st2nh
 

I want to buy bitx v3 pcb
The email of Mr. Sunil doesn't working -i.e. - suillakhani123@
gmail.com
Any more info, email, link
tnx-73
Nader, st2nh

Re: Bitx Kit Scope Waveforms

st2nh
 

This is a wonderful steps and demo
Many thanks OM Leonard
Now I can mark those shots as a test-point in bitx schematic

Nader,st2nh


--- In BITX20@..., "Leonard" <bitx@...> wrote:

I photographed the scope waveforms at important points on my kit
board.
If you can duplicate these amplitudes, you should be able to bias
up
the pa and get 10-12 watts out with 50 millivolts mike input.

http://golddredgervideo.com/kc0wox/bitxkitsigtrace/scopewaveformstx.ht
m

I took these measurements and documented them because I'm always
trying
to remember what I should have a certain test points. I plan on
printing this out and keeping a copy on my workbench.
Leonard

Re: Bandpass Filter

Jim Tonne <tonne@...>
 

Mark:

The 11 MHz filter of course does not change
according to the band you are moving to. It appears
to be a Butterworth design. Since it is so narrow
(relatively) the component Q values are controlling the
shape at the top. It would be inappropriate to say that this is a particular family (Butterworth, etc.). By
the way, an item of significance here is to pass the
SSB signal while attenuating some other stuff and have
a reasonably-low loss at 11 MHz. The family is so
irrelevant.

I found some time to reverse-engineer what Farhan had
done to create the input/output lowpass filter, which
DOES change according to the band you are moving
to..

(For the 20-meter design) it appers to be a 17 MHz
Butterworth lowpass which has had a part added to
form a "trap" at 29 MHz. This is a very reasonable
design technique although not optimum.

I do not have toroid-winding capability (no toroids
being the reason) and so the values I used for circuit
analysis are as follows:

Input termination 50 ohms
Output termination 50 ohms
From the amplifier side:
First shunt C to ground (C47) 200 pF
Inductor L2 .5758 uH
Second shunt C to ground (C48) 360 pF
Inductor L1 .43405uH
Final shunt C to ground (C49) 200pF

The harmonic at 28 MHz is down very far indeed.
The harmonic at 42 MHz is down 42 or more.
Higher harmonics are even further down, about
6 dB per octave.

To move this filter from 14.1 MHz to another
frequency, merely multiply the component values
(shown above) appropriately. To go to a 10-meter
design, for example, half the capacitors and halve
the inductors.

- Jim Tonne WB6BLD

P.S. to the BTX guys: do we need an appnote
about this?

Re: Bandpass Filter

Jim Tonne <tonne@...>
 

I am trying to understand the
bandpass filter in the BITX20A design.
Mark: would you be so kind as to send me
the parts values you are using?

- Jim WB6BLD (author of Elsie)

Bitx kit receiver waveforms

Leonard <bitx@...>
 

I've just added a page for testing the receiver. It's at
http://golddredgervideo.com/kc0wox/bitxkitsigtrace/rx.htm

I used my transmitter waveform page
http://golddredgervideo.com/kc0wox/bitxkitsigtrace/scopewaveformstx.htm
yesterday to test a receiver and it led me directly to a bad Q20. Well,
not directly because the test that checked Q20 was the absolute last
test on the last page. The procedure called for at least 800 mv's
signal out of Q20 with about 700 mv's in. I had the right in but the
out was only about 250 mv's. I didn't have a 2N5486 so I stuck in a
J310 not because it was a good sub but it was what I had. It gave me
about 700mv's out and I was able to bias up and set the PA for 12 watts
out so that tells me the rest of it is good. I ordered some 2N5486's
and next I can check the receiver with the new receiver procedure.
Leonard

Bandpass Filter

Mark <Mark@...>
 

Hi all

Just experimenting with a copper clad board version of the BITX20; and
trying to aim at 17M.

Using the software from ARRL i.e. Elsie; I am trying to understand the
bandpass filter in the BITX20A design. Can anyone advise if this is a
butterworth, chebycheff, whatever!

Any knowledge or advise appreciated.

Thanks,

Mark,

G0MGX

Re: Active Antenna

Arv Evans
 

Sanil

You are posting that question to the wrong group.

This is the BITX20 group, which is tightly focused on design,
construction, troubleshooting, and operation of the BITX20 QRP SSB
transceiver.

Thanks,

Arv
_._

Sanil wrote:



Suggest me a good , simple sensitive Active Antenna for my Grundig YB
400 short-wave Rx.
73s
Anil



--
======================================
Web: http://K7HKL.homelinux.net
http://bitx20a.livejournal.com
http://home.earthlink.net/~arvevans/
http://www.geocities.com/k7hkl_arv/
======================================

Re: Active Antenna

Greg W:-) <onegammyleg@...>
 

I agree Raj.

People often try active antennas hoping to improve weak signals and
instead they end up with overloading the radios front end being out
all sorts of unwanted birdies and mixing products --- The end result ,
a worse signal than what they had to begin with.

And for as portable which already has a lot of gain in the front end ,
this almost definitely a recipe for disaster.


gregW:-) OH2FFY

========================================================================

--- In BITX20@..., Raj <rajendrakumargg@...> wrote:
SNIP
I have never been satisfied with an active antenna,
SNIP
73 Raj vu2zap

Re: Weak signal reception

 

The Bitx needs re calculation of the coupling capacitor values in the
audio stages. AFAIK, the values are too high resulting in too much
low frequency response. The audio stages should start to roll off at
300 Hz and below.

I have brought this to the attention of Farhan and Doug in the past.

The only time I've seen the receiver motorboat was when R66 wasn't
set correctly.
Leonard
--
Raj, vu2zap
Bengaluru, South India.

Re: Active Antenna

 

Anil,

I have never been satisfied with an active antenna, try a random length long wire
with or without an earth counterpoise.

I use my 40M dipole with excellent results on all bands. Beats my active antenna
by light years! I use it with my home brew receiver (design in Hambrewers group
files section) and also the Icom and JRC receivers in my shack.

Right now I am contemplating on how to amplify the antenna and distribute it
to all my receivers!

73 Raj vu2zap

http://groups.yahoo.com/group/hambrewers

Suggest me a good , simple sensitive Active Antenna for my Grundig YB 400 short-wave Rx.
73s
Anil

Re: Active Antenna

Manuel Santos Greve <manuel.santosgreve@...>
 

Good Bye.

EA4BVZ - MADRID- Manuel Santos
----------------------------------------------------------------------------


2008/5/30, Sanil <sanil@...>:



Suggest me a good , simple sensitive Active Antenna for my Grundig YB 400
short-wave Rx.
73s
Anil