Date   
Re: Wiring Diagram

Robert Baker <robertibaker@...>
 

HELLO bd3133d....do you happen to know who brought your version of the kit to market? Hendricks maybe? If so you might be able to get a schematic right off of their web site? Worth a try.....

-----Original Message-----
Date: Friday, March 25, 2011 12:06:22 pm
To: BITX20@...
From: "bd3133d" <bd3133@...>
Subject: [BITX20] Wiring Diagram

Hi...Can anyone out there tell me where I can get a wiring diagram for the BITX20A...Just don't know where all the wires go...This is the first kit we have built and cannot find anything about the wiring.

If no diagram how about just giving me some advise about the wiring..

Re: Bitx20V3

hamfm1000
 

Here I am again answering my own posts.
I pulled the PA board out of the case this evening for troubleshooting.
Still 1V in 1V out at 14.3MHz measured at bottom of 56R.
So - where is the culprit I thought.
Something made me put 1V of 10.3 MHz into the PA.
And what! The scope shows a healthy 6V P-P for 1V input.
So it looks like I have some problem with the transformer T1.
Tomorrow it comes off the board and gets tested separately.

Let you all know how I get on.
73
Tony

--- In BITX20@..., "Tony" <hamfm1000@...> wrote:

Hi,
Back to the Bitx this weekend after a long 'thinking break'.
Am troubleshooting the PA board.
Using the 12V option.
I'm getting 5.06V on the zener.
Q1 is 2N3866 option
Collector = 6.02, Base 1.77, Emitter 1.17

Putting 1V P-P signal gets 4V P-P on scope at 14.200 MHz.

Any suggestions please gentlemen?

73
Tony

Re: BandPass Filter For All 9 HF Bands

Leonard
 

Great job!
If I had my shop setup I'd build one and test it with my network analyzer. Alas, it may be months before I get setup again.

Leonard

--- In BITX20@..., "g6lbq" <ah.electronics@...> wrote:

Just a quick post...

I have finished the bandpass filter for all 9HF bands to compliment the MultiBand BitX project.

For those interested I have uploaded full details in the files section in my personal folder.

73s Andy de G6LBQ

BandPass Filter For All 9 HF Bands

g6lbq
 

Just a quick post...

I have finished the bandpass filter for all 9HF bands to compliment the MultiBand BitX project.

For those interested I have uploaded full details in the files section in my personal folder.

73s Andy de G6LBQ

Re: Ver 3 mods?

Mark <huitmarmottes@...>
 

Hi Clayton,

The bandpass design depends on your parts supply and budget. The original used ready-available parts. The newer design was easier to make and tune and maybe has better Q. You could use toroids here too if you wanted. The mixer change was to a double balanced design, and I would definitely go for this. The IF gain improvement would be good too. You can see some of this in the "history" document in the files section. You can look at the bitx20a design for its sharper lowpass filter.

If you have strong stations near, then the AGC might be a better investment. You may also want to try the push-pull PA design or some of the different VFO mods.

Best of luck and be sure to let us know how it goes :-)

73s,

Mark.

--- In BITX20@..., "claytong_nz" <clayton@...> wrote:

Hi,

I am currently scratch-building a BITX20 using the original design on Ashhar's website, although with some changes for the SMD parts I'm using.
I note that there is a Ver 3 around with a few differences. These seem to be:
1. front-end change - use of canned coils and fixed caps rather than inductors and variable caps
2. Mixer change - two transformers in the mixer
3. IF amp - a two transistor stage after the crystal filter.
(have I missed any?)

My question is how much of a difference do these changes make, and should I be implementing them rather than the original? I was thinking that maybe I'll implement the original and then apply some of these V3 differences and see what happens, but maybe I should just do them anyway. Then I can also apply other changes like the transistor type, AGC stage, ..... - there seem to be quite a few ideas around!

Regards
Clayton
VK1TKA

Ver 3 mods?

claytong_nz
 

Hi,

I am currently scratch-building a BITX20 using the original design on Ashhar's website, although with some changes for the SMD parts I'm using.
I note that there is a Ver 3 around with a few differences. These seem to be:
1. front-end change - use of canned coils and fixed caps rather than inductors and variable caps
2. Mixer change - two transformers in the mixer
3. IF amp - a two transistor stage after the crystal filter.
(have I missed any?)

My question is how much of a difference do these changes make, and should I be implementing them rather than the original? I was thinking that maybe I'll implement the original and then apply some of these V3 differences and see what happens, but maybe I should just do them anyway. Then I can also apply other changes like the transistor type, AGC stage, ..... - there seem to be quite a few ideas around!

Regards
Clayton
VK1TKA

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 : /G6LBQ - Bitx/9 Band BPF PCB - Size 90mm by 165mm.pdf
Uploaded by : g6lbq <ah.electronics@...>
Description : 9 Band - Bandpass Filter Module PCB Artwork

You can access this file at the URL:
http://groups.yahoo.com/group/BITX20/files/G6LBQ%20-%20Bitx/9%20Band%20BPF%20PCB%20-%20Size%2090mm%20by%20165mm.pdf

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

g6lbq <ah.electronics@...>

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 : /G6LBQ - Bitx/9 Band BPF Manual.pdf
Uploaded by : g6lbq <ah.electronics@...>
Description : 9 Band - Bandpass Filter Module Manual

You can access this file at the URL:
http://groups.yahoo.com/group/BITX20/files/G6LBQ%20-%20Bitx/9%20Band%20BPF%20Manual.pdf

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

g6lbq <ah.electronics@...>

Bitx20V3

hamfm1000
 

Hi,
Back to the Bitx this weekend after a long 'thinking break'.
Am troubleshooting the PA board.
Using the 12V option.
I'm getting 5.06V on the zener.
Q1 is 2N3866 option
Collector = 6.02, Base 1.77, Emitter 1.17

Putting 1V P-P signal gets 4V P-P on scope at 14.200 MHz.

Any suggestions please gentlemen?

73
Tony

Re: BFO Waveform Problem

John Backo
 

--- In BITX20@..., John Warner <jrwdlw@...> wrote:

Leonard and John,

Thank you for the help. I tried adjusting R47 to the mid point. It doesn't make
any difference where it is adjusted. I removed C49, and the waveform looks
great. Following John's suggestion, I installed pin sockets at that location,
and tried a 560, 390, and 220pf capacitor for C49. The 560pf has 688 mVpp, the
390pf has 984 mVpp, and the 220pf has 1.67 Vpp. I uploaded the waveforms to the
WJ6JW folder. They are named "BFO Output C49 560pf 688 mVpp.BMP", "BFO Output
C49 390pf 984 mVpp.BMP", and "BFO Output C49 220pf 1.67 Vpp.BMP".

I'm confused by what is happening in the circuit. My understanding is that C49
is a coupling capacitor. Why does it's value have such an affect on the
circuit? There must be some other part in the circuit that is interacting to
cause the problem when using the specified .1uf value. If not, why isn't
everyone else having the same problem? What value should I use? Leonard's
waveform has over 2.5 Vpp. Would the 220pf be appropriate? Sorry for all the
questions, but I would really like to understand the problem and the solution

John
WJ6JW




What you are seeing is the effect of the impedance, Xc, on the circuit. Capacitive impedance is related to frequency, so at a given frequency, different capacitors have different impedances. The voltage out is the result of the loading of the mixer. If you measure carefully you will also notice a change in the voltage in to Q9, since the output impedance changes which in turn causes a change in the input impedance. All these effect the waveform.

Ideally, the input impedance (of the mixer) should be about 50 ohms for a balanced mixer. the output of Q9 should match that for best power transfer and waveform, without going into saturation. Note that the output of the mixer is into a 50 ohm attenuation pad.

However, the proof is in the pudding, so to speak. Which of the capacitors gives you the best loading of the mixer and the most natural sounding result in the receiver? It doesn't have to be .1uf. In fact that is probably not an ideal match; it is used because it works and it is easily available to everyone.

Use the one which delivers about 1 to 1.5v to the mixer. 2.5v works but is probably unnecessarily high. That only causes more spurious response. In other words, use the minimum necessary to get the job done. Probably anything from .001uf to 220pf or so would work ok (as does .1uf of course).

Also, don't forget to be aware of the loading of your probes and their effect on the signal form. Check the signal through a 10pf or so capacitor attached to the probe and see if that makes a difference in the waveform. Some of that distortion may be unnatural to the circuit itself.

Others have stated, correctly I think, that the balance pot should be 200 ohms for best results. But that is not necessary to make the circuit work; it probably contributes to better carrier suppression.

You will note the same thing happening with the VFO with C40 and Q7. There is some variation in the level of the VFO over its frequency range, and it has an effect at the mixer driver. The same thinking applies there.

john
AD5YE

Re: BFO Waveform Problem

jrwdlw
 

Leonard and John,

Thank you for the help. I tried adjusting R47 to the mid point. It doesn't make
any difference where it is adjusted. I removed C49, and the waveform looks
great. Following John's suggestion, I installed pin sockets at that location,
and tried a 560, 390, and 220pf capacitor for C49. The 560pf has 688 mVpp, the
390pf has 984 mVpp, and the 220pf has 1.67 Vpp. I uploaded the waveforms to the
WJ6JW folder. They are named "BFO Output C49 560pf 688 mVpp.BMP", "BFO Output
C49 390pf 984 mVpp.BMP", and "BFO Output C49 220pf 1.67 Vpp.BMP".

I'm confused by what is happening in the circuit. My understanding is that C49
is a coupling capacitor. Why does it's value have such an affect on the
circuit? There must be some other part in the circuit that is interacting to
cause the problem when using the specified .1uf value. If not, why isn't
everyone else having the same problem? What value should I use? Leonard's
waveform has over 2.5 Vpp. Would the 220pf be appropriate? Sorry for all the
questions, but I would really like to understand the problem and the solution

John
WJ6JW





________________________________
From: "iam74@..." <iam74@...>
To: BITX20@...
Sent: Sat, March 19, 2011 5:42:30 PM
Subject: [BITX20] Re: BFO Waveform Problem




--- In BITX20@..., "LeonardL" <dredger@...> wrote:

1 more thing to check. Adjust R47 to midrange. It may chenge the waveform. My
picture was probably shot after the balanced modulator was already adjusted.
Leonard

--- In BITX20@..., "LeonardL" <dredger@> wrote:

If R43, 44, 45 are all 1k, I'd pop one lead of C49 up and recheck the
waveform at Q9 emitter.
Leonard
It would appear to me that Q9 is being driven into saturation. So part of the
duty cycle is free of the signal, and that changes the frequency subtly. What is
the P-P voltage coming into and out of Q9? It should be about .8v or so, though
up to about 1.5v works ok. And as Leonard remarks, the shape is partly dependent
upon the mixer load.(R47 should probably be 200 ohms). It is ok to inject a TTL
shaped wave here, but a neatly clipped sine wave would generate less mess in the
mixer. Ideally, the magnitude should be +7 dBm or so coming out of Q9.

Try reducing the value of the capacitor C49. On my rig, I placed a two-pin
connector there. That way I could insert any value capacitor I wished, or inject
an external VFO at that point adjusted to the "right" voltage.

john
AD5YE

Re: BFO Waveform Problem

John Backo
 

--- In BITX20@..., "LeonardL" <dredger@...> wrote:

1 more thing to check. Adjust R47 to midrange. It may chenge the waveform. My picture was probably shot after the balanced modulator was already adjusted.
Leonard

--- In BITX20@..., "LeonardL" <dredger@> wrote:

If R43, 44, 45 are all 1k, I'd pop one lead of C49 up and recheck the waveform at Q9 emitter.
Leonard

It would appear to me that Q9 is being driven into saturation. So part of the duty cycle is free of the signal, and that changes the frequency subtly. What is the P-P voltage coming into and out of Q9? It should be about .8v or so, though up to about 1.5v works ok. And as Leonard remarks, the shape is partly dependent upon the mixer load.(R47 should probably be 200 ohms). It is ok to inject a TTL shaped wave here, but a neatly clipped sine wave would generate less mess in the mixer. Ideally, the magnitude should be +7 dBm or so coming out of Q9.

Try reducing the value of the capacitor C49. On my rig, I placed a two-pin connector there. That way I could insert any value capacitor I wished, or inject an external VFO at that point adjusted to the "right" voltage.


john
AD5YE

Re: BFO Waveform Problem

Leonard
 

1 more thing to check. Adjust R47 to midrange. It may chenge the waveform. My picture was probably shot after the balanced modulator was already adjusted.
Leonard

--- In BITX20@..., "LeonardL" <dredger@...> wrote:

If R43, 44, 45 are all 1k, I'd pop one lead of C49 up and recheck the waveform at Q9 emitter.
Leonard

Re: BFO Waveform Problem

Leonard
 

If R43, 44, 45 are all 1k, I'd pop one lead of C49 up and recheck the waveform at Q9 emitter.
Leonard

Re: BFO Waveform Problem

jrwdlw
 

I was referring to a PDF version of the manual. Using the link you posted, it's
the scope picture at the URL
http://golddredgervideo.com/kc0wox/bitxver3new/bfo/bfoonscope.gif, and has the
title "500mV VER3 BFO" on the CRT.

You are correct about the 254 mV output level. What's interesting is the output
from Q8 emitter (titled "BFO Q8e 100ns") is 2.38 Vpp. Any comments would be
greatly appreciated.

John





________________________________
From: LeonardL <dredger@...>
To: BITX20@...
Sent: Sat, March 19, 2011 12:49:47 PM
Subject: [BITX20] Re: BFO Waveform Problem


The waveform doesn't really bother me much, see
http://golddredgervideo.com/kc0wox/bitx/transformers.htm ,what bothers me is the
amplitude. If I interpret your scope display, you only have 254 mv's of
amplitude. I'm not sure what you sre refering to page 18. The updated manual at
http://golddredgervideo.com/kc0wox/bitxver3new/newmanual.htm is html and on my
computer doesn't have page numbers. Verify that we are looking at the same link
and version of the manual. There are a few old versions and I did a couple of
pdf's. Post the link to the manual you are looking at. Then I can see the
picture of mine you are refering to

Leonard

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

I was comparing my waveform to the one shown on page 18 of Leonard's "Building
Bitx 3" document. The waveform at the Q8 emitter looks very similar, but once
it comes out of Q9 it's a mess (C49 on my schematic). I've checked to see that
I have the right components in the right places, and it looks good. I hoping
that someone here can look at the waveforms, and tell me what's wrong. I've
included both 100ns and 25ns waveforms, as the 25ns show better detail. They
are located in the WJ6JW folder.

Thanks
John






[Non-text portions of this message have been removed]

Re: Polyvaricon stability issues

byling4 <b.paton1@...>
 

@Raj VU2ZAP,..thanks Raj,..yes I do have it very close to the other rig so I can accept your comments,..like yourself I use bees wax melted over the toroids and other parts which may oscillate,[a tip learned from George G3RJV]..i've left the rig powered for lengthy periods of time but have not noticed any drift,..my finger placed on the back of the polyvaricon or me holding the two wires completely stops the howling which is why I thought that side of the rig was unstable in some way,...

@Steve,G0FUW,..thanks Steve,..again I would accept what you've said but the problem exists even without a mike actually connected,..and i've gone out of my way to have all the wiring either disconnected or moved aside while trying to resolve the issue,...
my intentions were to do the varactor mod eventually, but I thought it best to get it working and txing as the kit supplied before moving on to that,...thanks to both of you for your feedback,..Colin GM7TFN

--- In BITX20@..., Raj <vu2zap@...> wrote:

Colin,

Howling/Whistling would be carrier leak (R66/C65), you could try adjust it to a minimum. When two rigs are very close a small amount of carrier leak would be noticeable but not affect you much on actual transmit. I have seen this with commercial rigs too!

If the whistle is drifting then you could look at polyvaricon issue. Air variable would improve the situation IMHO. Temperature changes in your enclosure will cause some drift. I used to melt some wax over oscillator components to insulate them and reduce drift.

Hope this helps.

on another rig it is doing quite a bit of howling/whistling,...I have tried different wiring arrangements i.e.twisted pairs,single wires to the capacitor,..would using a miniature coax perhaps help or could somebody advise on how they are stabilising that side of the kit. Any and all feedback/comments are appreciated,...thanks de Colin GM7TFN
73

--
Raj, VU2ZAP
Bangalore, India.

Re: BFO Waveform Problem

Leonard
 

The waveform doesn't really bother me much, see http://golddredgervideo.com/kc0wox/bitx/transformers.htm ,what bothers me is the amplitude. If I interpret your scope display, you only have 254 mv's of amplitude. I'm not sure what you sre refering to page 18. The updated manual at http://golddredgervideo.com/kc0wox/bitxver3new/newmanual.htm is html and on my computer doesn't have page numbers. Verify that we are looking at the same link and version of the manual. There are a few old versions and I did a couple of pdf's. Post the link to the manual you are looking at. Then I can see the picture of mine you are refering to

Leonard

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

I was comparing my waveform to the one shown on page 18 of Leonard's "Building Bitx 3" document. The waveform at the Q8 emitter looks very similar, but once it comes out of Q9 it's a mess (C49 on my schematic). I've checked to see that I have the right components in the right places, and it looks good. I hoping that someone here can look at the waveforms, and tell me what's wrong. I've included both 100ns and 25ns waveforms, as the 25ns show better detail. They are located in the WJ6JW folder.

Thanks
John

BFO Waveform Problem

jrwdlw
 

I was comparing my waveform to the one shown on page 18 of Leonard's "Building Bitx 3" document. The waveform at the Q8 emitter looks very similar, but once it comes out of Q9 it's a mess (C49 on my schematic). I've checked to see that I have the right components in the right places, and it looks good. I hoping that someone here can look at the waveforms, and tell me what's wrong. I've included both 100ns and 25ns waveforms, as the 25ns show better detail. They are located in the WJ6JW folder.

Thanks
John

Re: Modifying a version 3 for multiband use?

gabadola
 

hi,
i have build all 2 bitx. over the bitx20 version 3 i have my bpf for all
bands and the dds , not the premixed vfo. the g6lbq is the same .
in the first i have the filter of 10mhz and in the second i have the filter
(and the bfo) 9830400, but i have tried even the 9mhz without modification to
the bfo circuit..
the dds level is around 3v pp and no problem in the mixer with toroid and diode
. in the ade mixer i have limited the dds to 1,5 vpp .





________________________________
Da: James H <jameshickox@...>
A: BITX20@...
Inviato: Ven 18 marzo 2011, 23:18:42
Oggetto: [BITX20] Modifying a version 3 for multiband use?


Hello All,
I got my basic kit in today for the BITX. Mine came with the two boards, a set
of IF cans for the BPF and some toroids and bobbin core forms.

While looking over the basic ver.3 schematic and rhe G6LBQ schematic, I started
wondering if the main differences in the RF path are limited t just the BPF and
the VFO circuit.

Would I be able to modify the board by taking re-routing the signal at the
output of L3 and making that my point to go to outboard bandpass filters?

Second, would a DDS VFO or premix type VFO work by injecting its output into
the0.1 uF. cap liocatd at the base of Q7?

Lastly, If I wanted to change the BFO and crystal filter to 9.0 Mhz, would I
need to adjust T1A, T1, T2, or L5? The other parts of the circuit appear to be
quite broadbanded.

Thanks for any comments and suggestions.

James Hickox, AA5AO
Abilene, TX, USA







[Non-text portions of this message have been removed]

Re: Polyvaricon stability issues

 

Colin,

Howling/Whistling would be carrier leak (R66/C65), you could try adjust it to a minimum. When two rigs are very close a small amount of carrier leak would be noticeable but not affect you much on actual transmit. I have seen this with commercial rigs too!

If the whistle is drifting then you could look at polyvaricon issue. Air variable would improve the situation IMHO. Temperature changes in your enclosure will cause some drift. I used to melt some wax over oscillator components to insulate them and reduce drift.

Hope this helps.

on another rig it is doing quite a bit of howling/whistling,...I have tried different wiring arrangements i.e.twisted pairs,single wires to the capacitor,..would using a miniature coax perhaps help or could somebody advise on how they are stabilising that side of the kit. Any and all feedback/comments are appreciated,...thanks de Colin GM7TFN
73

--
Raj, VU2ZAP
Bangalore, India.