Date   
Re: About unknown inductances

Bay Mete
 

Also you can try a quick search on
http://www.ebay.com
either.

Best wishes
TB3CWG Mete


2007/2/12, Clark <anelectricboat@...>:


Where are you guys getting your toroids? (I'm a beginner, too) I can
solder and all that (Navy electrician), but I haven't the foggiest idea
where to buy toroids.

Thanks and 73 de KI4GYT Clark


BITX20 Kit Progress Report

Doug Hendricks <ki6ds@...>
 

It is time to give you another progress report. We have good news and we have bad news. The bad news first.

We are going to have to do another run of prototypes with a few changes in the layout. We discovered that there was a stability problem with the i.f. amplifier in the receiver that required a fix. Dan found one, and it is fixed but the fix needs to be added to the layout. The first layout had some pins reversed on the relays, again that had to be corrected. And finally, there is a stability problem with the final amplifier chain the way that it is layed out. Dan is going to add one more stage to add additional gain and also move the location of the final amplifier away from the source of the instability.

The good news. First of all, we have not found anything that is remotely close to a show stopper. The VFO is going to be stable and we are happy with it. We have found that we can use toroids and trimcaps where needed. We also are happy with most of the pcboard layout, other than the fixes mentioned above.

The bottom line. The BITX20 will happen, don't worry. One thing that Dan, Arv and I are agreed on is that we must do adequate testing to make sure that when we do release the kits, that they will work. Every run of prototypes cost money, but it is money that is well spent and necessary. Every run of prototypes also cost time, and as the old adage goes, time is money. But again, the time is well spent and necessary.

Now I hope that you will understand why I have not accepted any orders or money. I don't want to do that until we have a viable product and a delivery date that can be realisticly met. Thanks again for all of your support and patience. This is going to be a great experience when we get to the end. 72, Doug, Dan, Arv and Jim.

Re: About unknown inductances

farhan@...
 

dimitri,

the broadband transformers are being used just as transformers. They are not behaving like an inductors that have reactance. This is to do with the fact that there is a secondary winding that is consuming the emf setup by the primary winding. hence, the actual inductance is not very important except that there is enough of it to be able to setup a strong magnetic field that can be picked up by the secondary winding.

in order to ensure the transformer effect, a winding should have a reactance atleast 4 times that of the impedance that is driving (or being driven from). this is a rule-of-thumb. If it is twenty times instead of four, you wont suffer any problem. The only aspect to be considered with higher inductances is that they have more turns and more turns mean more capacitance (between succseive loops of winding wire). If the inductance gets high enough to be able to resonant (along with the stray capacitance of the wires) within the general wheraabouts of the spectrum of work (3-30mhz in our case), then we will have a problem.

i used the tv balun cores for almost all the broadband transformers except in the power amplifer output. I considered the output of 5 watts excessive for the tv baluns to handle (without any experimental substantiation, I must admit). Hence, i used tap-washers (that are for all purpose, just air-core toroids). With air core toroids, I faced the problem of too many turns that lead to higher inter-winding capacitance. Conveniently, the power amplifier's transformer was feeding the half-wave output filter which absorbs the effect of higher transformer capacitance as well the IRF510's higher drain-source capacitance.

The transformers are used mostly in the power chain. I assume that by adding an extra amplification stage in the power chain, we can keep all impedances (input and output) of the entire power chain at 50 ohms, eliminating the need for transformers at all. The only requirement then would be to have an impedance matching transformer in the output stage.

The additional stage would probably also stabilize the power chain further and help boost the driver output (which is a fight with the transistors in my junk box).

- farhan

On Sun, 11 Feb 2007, Dimitri Aguero wrote:

Good evening to all

Experimented builders: please be patient with my beginner's question.
Remember that some of us have not deep knowledge of electronics...

Yesterday I was measuring some toroids I have got. My goal is to use
reproductible materials.

One was a big T-200-2
Another, a medium-sized T-50-43
Another, a small T-28-61
Another, was recovered from a BNC cable connecting Megabit Ethernet switches
Another (green) was recovered from an inductance in a power souce
Another was a binocular core sold by French supplier Selectronic. Material
unknown, possibly a 4B1.
Another, finally, was a 4C65 ferrite.

I took the time to measure all of them between 1 to 30 MHz with my Palstar
ZM-30, which delivers +/- 1V peak to peak (0,7 V at higher frequencies).
All of them showed more or less the following four behaviours:

1) Inductance increases more or less slowly
2) Inductance arrives to a peak
3) Inductance decreases quickly
4) *Impedance* becomes > 600

Exceptions: the 61 material and the green inductance, which showed in that
range only behaviour 1)

The question I want to answer is: which of them is the best material for the
broadband transformers required by Farhan's design ?

My feeling is that, at the frequency of the transformer, the material should
be near behaviour 1) (steady inductance across all frequencies, to show a
linear behaviour)
Materials showing behaviour 4) should not used, zones 3 and 2 are non-linear
and should be avoided.

Thank you in advance for any comments.





Re: About unknown inductances

myid_63301
 

--- In BITX20@..., "Richard E. Teague" <k5btp@...> wrote

...Where are you guys getting your toroids? ..
Thanks and 73 de KI4GYT Clark
________________________________________
www.kitsandparts.com

Good parts and quick service

Stan

Re: About unknown inductances

Richard E. Teague
 

...Where are you guys getting your toroids? ...



Thanks and 73 de KI4GYT Clark

________________________________________







I get most of mine from W8DIZ at kits and parts



http://partsandkits.com/index.asp







73 de K5BTP

Re: About unknown inductances

ki6ds@...
 

I sell a toroid and wire kit on my web page. Go to www.qrpkits.com and
click on the picture of the toroid kit. The basic kit consists of 25 of
each of the following toroids:

t37-2, t37-6, ft37-43, ft37-61, plus 50 feet of #28 thermaleze red and 50
feet of #28 thermaleze green wire, for $25 plus shipping. For $5 more you
can add 50 feet of red and green #26 wire. 72, Doug

Where are you guys getting your toroids? (I'm a beginner, too) I can
solder and all that (Navy electrician), but I haven't the foggiest idea
where to buy toroids.

Thanks and 73 de KI4GYT Clark

Re: About unknown inductances

Clark
 

Where are you guys getting your toroids? (I'm a beginner, too) I can
solder and all that (Navy electrician), but I haven't the foggiest idea
where to buy toroids.

Thanks and 73 de KI4GYT Clark

Re: About unknown inductances

Steve Hartley G0FUW <g0fuw@...>
 

Dimitri
I have used T-50-43 for all broadband transformers and RF choke with excellent results.
The VFO coil was wound on a T-50-2, and the RF bandpass and Low Pass filter coils all on T-50-6.
73, Steve, G0FUW

----- Original Message -----
From: Dimitri Aguero
To: BITX20@...
Sent: Sunday, February 11, 2007 5:44 PM
Subject: [BITX20] About unknown inductances


Good evening to all

Experimented builders: please be patient with my beginner's question.
Remember that some of us have not deep knowledge of electronics...

Yesterday I was measuring some toroids I have got. My goal is to use
reproductible materials.

One was a big T-200-2
Another, a medium-sized T-50-43
Another, a small T-28-61
Another, was recovered from a BNC cable connecting Megabit Ethernet switches
Another (green) was recovered from an inductance in a power souce
Another was a binocular core sold by French supplier Selectronic. Material
unknown, possibly a 4B1.
Another, finally, was a 4C65 ferrite.

I took the time to measure all of them between 1 to 30 MHz with my Palstar
ZM-30, which delivers +/- 1V peak to peak (0,7 V at higher frequencies).
All of them showed more or less the following four behaviours:

1) Inductance increases more or less slowly
2) Inductance arrives to a peak
3) Inductance decreases quickly
4) *Impedance* becomes > 600

Exceptions: the 61 material and the green inductance, which showed in that
range only behaviour 1)

The question I want to answer is: which of them is the best material for the
broadband transformers required by Farhan's design ?

My feeling is that, at the frequency of the transformer, the material should
be near behaviour 1) (steady inductance across all frequencies, to show a
linear behaviour)
Materials showing behaviour 4) should not used, zones 3 and 2 are non-linear
and should be avoided.

Thank you in advance for any comments.

Re: About unknown inductances

Arv Evans
 

Dimitri

For the untuned transformers in Farhan's design, the issue is more one
of power transfer than that of inductance. You might try winding up a
bifilar winding of 10 to 16 turns so you have a 1-to-1 transformer.
Terminate the secondary in 50 ohms and drive the primary with a 50 ohm
source. Measure the power transfer characteristics. If your cores will
transfer power with minimal loss at 10 MHz, then they should work in
your transceiver.

For the tuned inductances (VFO, RF amplifiers, etc.) you can try a
variable capacitor and a winding that allows resonance at 10 MHz. By
tuning the signal source off frequency while measuring RF across the
resonant circuit you can get a good idea of Q-factor. for that
inductor. This will help you determine if they are suitable for use in
your BITX20.

If you do not have enough suitable toroidal cores, you can always use
the non-ferrite tap-washer idea from Farhan's original circuit
description. While these do not have the tight magnetic path of ferrite
cores, they do work and can be made from about any small circle of
plastic or similar non-metallic material.

Arv
_._

Dimitri Aguero wrote:


Good evening to all

Experimented builders: please be patient with my beginner's question.
Remember that some of us have not deep knowledge of electronics...

Yesterday I was measuring some toroids I have got. My goal is to use
reproductible materials.

One was a big T-200-2
Another, a medium-sized T-50-43
Another, a small T-28-61
Another, was recovered from a BNC cable connecting Megabit Ethernet
switches
Another (green) was recovered from an inductance in a power souce
Another was a binocular core sold by French supplier Selectronic. Material
unknown, possibly a 4B1.
Another, finally, was a 4C65 ferrite.

I took the time to measure all of them between 1 to 30 MHz with my Palstar
ZM-30, which delivers +/- 1V peak to peak (0,7 V at higher frequencies).
All of them showed more or less the following four behaviours:

1) Inductance increases more or less slowly
2) Inductance arrives to a peak
3) Inductance decreases quickly
4) *Impedance* becomes > 600

Exceptions: the 61 material and the green inductance, which showed in that
range only behaviour 1)

The question I want to answer is: which of them is the best material
for the
broadband transformers required by Farhan's design ?

My feeling is that, at the frequency of the transformer, the material
should
be near behaviour 1) (steady inductance across all frequencies, to show a
linear behaviour)
Materials showing behaviour 4) should not used, zones 3 and 2 are
non-linear
and should be avoided.

Thank you in advance for any comments.



About unknown inductances

Dimitri Aguero <daguero@...>
 

Good evening to all

Experimented builders: please be patient with my beginner's question.
Remember that some of us have not deep knowledge of electronics...

Yesterday I was measuring some toroids I have got. My goal is to use
reproductible materials.

One was a big T-200-2
Another, a medium-sized T-50-43
Another, a small T-28-61
Another, was recovered from a BNC cable connecting Megabit Ethernet switches
Another (green) was recovered from an inductance in a power souce
Another was a binocular core sold by French supplier Selectronic. Material
unknown, possibly a 4B1.
Another, finally, was a 4C65 ferrite.

I took the time to measure all of them between 1 to 30 MHz with my Palstar
ZM-30, which delivers +/- 1V peak to peak (0,7 V at higher frequencies).
All of them showed more or less the following four behaviours:

1) Inductance increases more or less slowly
2) Inductance arrives to a peak
3) Inductance decreases quickly
4) *Impedance* becomes > 600

Exceptions: the 61 material and the green inductance, which showed in that
range only behaviour 1)

The question I want to answer is: which of them is the best material for the
broadband transformers required by Farhan's design ?

My feeling is that, at the frequency of the transformer, the material should
be near behaviour 1) (steady inductance across all frequencies, to show a
linear behaviour)
Materials showing behaviour 4) should not used, zones 3 and 2 are non-linear
and should be avoided.

Thank you in advance for any comments.

Re: Filter frequency and BFO setting

Jim Kortge <jokortge@...>
 

Stan wrote:
--- In BITX20@..., Jim Kortge <jokortge@...> wrote:


I'll take a crack at an answer...

The center of the passband is indeed above the marked crystal >
Thanks Jim, That was a big help,
Good...that exercise was good for my sagging brain last nite! :-)

I see where I made my mistake.
You're correct it does help to doodle it out on a dwg.
That's the only way I can do those kind of things and get it right. With every rig I've designed, I've gone through the same exercise, since some of them use the wrong sideband, as set by convention. USB for instance on the 2N2/40 rig.

Glad I could be of some help Stan, and nice to get email from you. Lots of good activity on the BITX20 reflector. As a homebrewer, I find that very exciting and gratifying, know there is still much interest in building.

72,

Jim, K8IQY

Re: Filter frequency and BFO setting

Jim Kortge <jokortge@...>
 

Rahul Srivastava wrote:
Hi! Jim,
Nice to hear from you. Looking forward to some designs from you. BTW Norton rf preamps amps patterned on your designs are huge success with friends here.
73
Rahul VU3WJM
Greetings Rahul,

Nice to hear from you.

Great to hear the Norton design ala K8IQY is being used. That design is really solid and works well. Been following the activity on the BITX20; lots of enthusiastic builders and many experimenters it appears. All good!! :-)

I'm actually working on a two-band SSB/CW rig targeted for bicycle mobile and pedestrian mobile use, so Rx is really low power, somethink like 38 ma. at the moment without the DDS VFO. I may scrap that in favor of a more conventional VFO or VXO to keep the current down. The unfortunate thing is that most of the ICs that I've used are only available in SMT. That keeps the parts count down and the features up, but makes it much harder for most hams to build. I may revert to a configuration where only the ICs are SMT, and everything else is through-hole, to make building it more reasonable. We'll see.

I did notice that some of the BITX20 builders were talking about putting the rig on 40 meters. I've thought about that and realized it would be very easy to do if the IF were shifted to 10.7 MHz. Fortunately, there is a standard computer crystal close to that frequency from Mouser and others. I'm going to get some on order to flesh out a replacement crystal filter for the rig. With the slightly higher crystal filter, the VFO would move down in frequency a bit; then the same VFO could be used for either a 20 or 40 meter rig, with only parts in the front-end needing to be changed.

Guess that's it my friend. Keep up the good work and I'll continue to read the emails and help where I can. I've offered to assist Doug, KI6DS with his kit, so will be building a BITX20 somewhere along the way. I'm interested in how it looks on the lab equipment. I've modelled much of the circuitry in SPICE and will continue to do more of that.

72 and kind regards,

Jim, K8IQY

Re: Filter frequency and BFO setting

myid_63301
 

--- In BITX20@..., Jim Kortge <jokortge@...> wrote:


I'll take a crack at an answer...

The center of the passband is indeed above the marked crystal >
Thanks Jim, That was a big help, I see where I made my mistake.
You're correct it does help to doodle it out on a dwg. How to get it
set up.

73 de Stan ak0b

Re: V.3 PCB Layout

Rahul Srivastava
 

Hi!
Very true about the influx of sub standard components in mkt. In these parts problem is even worse. In commercial line of work every month or so I simply have to reject the whole lot. Certain opto couplers and even 7905s lately gave me hard time.
Early 2SCxxx devises seemed to be very good. I have also used many in past. Possibly the earlier JA stuff was better than what the dragon is pushing.
Jim K8IQY has sucessfuly used generic devise as very good and low noise RF preamp in Norton configration but again as you rightly said at low input / outpt impendences.. Apart from excellent designs wis web page is also an electronics art galley to be admired. A VHFcomm artical and some RU make use of this configration in Bi Directional mode.

I feel 3904 is an ideal choice for the kit by Doug and Dan.
73
Rahul VU3WJM

Allison Parent <kb1gmx@...> wrote:
--- In BITX20@..., Rahul Srivastava <vu3wjm@...> wrote:

HI! Allison,
The gain does not changes until thre devices meet the Ft/f > 10
criteria. Unfortunately cheaper devices from the far east do not meet
the published specs as far as Ft is concerned. Bi -directional nature
and additional AC feedback of two stages tends to reduce the gain as well.

That is true but if the stage gain is low as used in the BITX
IF stages then the 10x criteria may be a bit lower.

Sounds like cheaper devices could be really devices that don't
meet spec (rejects). In that case your best calculations are
likely not going to hold as the device is undefined.

BC547s and 2N2222 s have a higher capacitance as well. Just make a
tuned xtal osc of single xtal variety and try out different devices, a
better picture evolves of gain and device add on capacitance. 2N3904
have always worked well in past for me but are not so common as the
547s in this region hence the mod with local components. I am not sure
of other places but here we get 2SC2570A very cheap why take a risk
rather than go ahead with a high Ft device??.

Yes, understood. Most of the 2222s, 3904 and similar have an FT
of around 300mhz or better. But there are a lot of other devices
that easily make 100mhz FT and thats enough for the IF and BFO.

Devices I've tried are 2xc710, 2sc1815, 2sc945, 2sc839, 2sc1674,
2sc1675 and 2sc941 and many more (pulls from old 27mhz CB radios
from the 1980s).

As to device capacitance most small signal transistors are
adaquate for 10mhz region. At higher frequencies it may be
more problematic. However, I've used metal can 2n2222A at
6m as RF amp and even 10-100mw drivers. The trick there is a
50ohm system to make the RC loading less significant. Another
example is I'm using a 2sc1226A which has an FT of 150mhz as
a 10M SSB driver transistor (~.5w output) and it works excellent
though it's not being stressed. The nominal use for that
transistor was 5-15W audio amplifer output stage.

A high FT device is a desireable choice for the RF amp where
noise is also a factor. The 3905 or 2222 is around 6db NF
at best where a better device like the 2n3866, 2n5109, 2sc1252,
2sc2570 will drop that to 3-4db (resistive feedback amplfiers
are inherently noisy). For HF that may not be important but
at 10m and 6m it is more significant.

Allison




Allison Parent <kb1gmx@...> wrote:
--- In BITX20@..., Rahul Srivastava <vu3wjm@>
wrote:

Hi! Dan,
V3 should be stable with 2222 devices as they have lower gain than
3904s. However if the IF stage is made with 3904s keeping the feedback
resistor at 10k should be a good starting point.

The gain sould not change as the amps (see Farhans origional article)
are of the feedback type and the components around the amp set the
gain. The critical parameter is the device FT (frequency where the
device gain is unity [1]) as it could be not less than 5x and
preferable 10x the operating frequency. For the IF and BFO the
2222 or 3904 are about even. I've found 2SC945 and 2SC839s to
work well in most of same circuits.

Where the device used is more cirtical is the RF amp (RX) and the
TX driver and final.

Another reason for high gain is better quality ferrites. Our VU
ones are not as good as Amidon and Fair-rite stuff. Farhan and myself
bought a pack of 500pcs binocular cores for Rs200/ ie 1 cent per core.

The problem of cores is if they are not ferrite and are powered
iron. The wrong core material can hurt performance or make the
tuned circuits have very low Q (or not tune at all). For the IF
and mixers I found the cores sould have a high ui (usually type 43
(ui of 850) ferrite) though type 61 (ui of 125)powered iron will
work with more turns of wire. The problem is if you have unknown
cores you have to try and see.

Should make only a small difference over the tap washers as there
is less unintended coupling to other stages. I tested both and the
difference is small. The ferrite loaded coils require less wire
and are more compact though. I used both FT37-43 (ferrite ring)
for interstage and also tried binocular cores (2hole) and both
produce the same results.

I'm using the board from FAR circuits (they are in the USA) that
is the basic Farhan circuit and layout. I've built one for 6M
and also working on one I've decide will be for 10M. At those
frequencies the devices closest to the antenna are more important.

Regards,
Allison






---------------------------------
The all-new Yahoo! Mail goes wherever you go - free your email
address from your Internet provider.







---------------------------------
Now you can scan emails quickly with a reading pane. Get the new Yahoo! Mail.

Re: Filter frequency and BFO setting

Rahul Srivastava
 

Hi! Jim,
Nice to hear from you. Looking forward to some designs from you. BTW Norton rf preamps amps patterned on your designs are huge success with friends here.
73
Rahul VU3WJM

Jim Kortge <jokortge@...> wrote:


Stan wrote:
I have managed to confuse myself. In a series xtal filter as used in
the BITX20 doesn't the frequency of the filter bandpass actual increase
above the frequency of the xtals?
I'll take a crack at an answer...

The center of the passband is indeed above the marked crystal frequency, a lot
or little depending on the coupling capacitors used. For narrow band filters,
(larger coupling capacitors) the frequency is closer to the marked case
frequency, for wide band filters (SSB)implemented with smaller coupling
capacitors it is even farther away.

i.e. the BP would be 10.0 to say
10.003 MHz
Or more maybe....but we'll use your numbers. So it is a 3 KHz wide filter
centered at 10.001500 MHz, with the lower passband edge at 10.000 MHz and the
upper passband edge at 10.003 MHz


Then the BFO would be set at 10.003 and then the result is hetrodyned
to 14 MHz we have USB ?
Not the way I see it...

For the sake of discussion, lets assume the audio passband goes from dc to 3
KHz, just to make things simple. If we run that into a mixer with a 10 MHz BFO,
the resulting principle output will be a double sideband signal centered at
10.000 MHz. Extending upward from the carrier is an upper sideband signal, from
10.000 to 10.003 MHz., and a lower sideband signal, extending from 10.000
downward to 9.997 MHz. The audio spectrum is also inverted on the lower
sideband, such that the highest audio frequency, 3 KHz is now the lowest RF
frequency, at 9.997 MHz.

Since we want USB on 20 meters or 14 MHz, whatever comes out of the crystal
filter will be hetrodyned up in frequency an additional 4 MHz. If this is the
USB being passed through the filter, the BFO needs to be at 10.000 MHz so that
the USB portion of the DSB signal fits into the passband of the filter, that
from 10.000 to 10.003 MHz. When we hetrodyne it is up to 14 MHz 10MHz+4MHz), no
inversion takes place or is desired. The lowest audio frequency will be at
14.000 MHz and the higest audio frequency will be at 14.003 MHz.

If we wanted the LSB signal to pass through the filter, we would have to raise
the BFO frequency another 3 KHz, so that the USB signal now fits into the
crystal filter passband. The USB part of the DSB signal now resides from 10.003
to 10.006 MHz, and will be rejected by the filter.

However, if we hetrodyne to 4 MHz then the result is LSB
I'm not following this part. The VFO is at about 4 MHz. The other signal out of
the 2nd mixer would be at 6 MHz nominally (10MHz-4MHz), with the audio inverted,
so it would be a LSB signal from 5.997 to 6.000 MHz.

However in both cases the BFO would he on the high frequency side of
the filter?
Not the way I see it and have drawn it on my doodle sheets. I have to make
pictures of the signals and passbands everytime I do one of these analyses.
You'd think eventually I could remember all of it, but my head is too tired to
do that anymore.

Please verify or correct me. Thanks, Stan
I hope I've got it right. Comments others??

72 and cheers to all,

Jim, K8IQY





---------------------------------
What kind of emailer are you? Find out today - get a free analysis of your email personality. Take the quiz at the Yahoo! Mail Championship.

Re: Filter frequency and BFO setting

Jim Kortge <jokortge@...>
 

Stan wrote:
I have managed to confuse myself. In a series xtal filter as used in the BITX20 doesn't the frequency of the filter bandpass actual increase above the frequency of the xtals?

I'll take a crack at an answer...

The center of the passband is indeed above the marked crystal frequency, a lot or little depending on the coupling capacitors used. For narrow band filters, (larger coupling capacitors) the frequency is closer to the marked case frequency, for wide band filters (SSB)implemented with smaller coupling capacitors it is even farther away.

i.e. the BP would be 10.0 to say
10.003 MHz
Or more maybe....but we'll use your numbers. So it is a 3 KHz wide filter centered at 10.001500 MHz, with the lower passband edge at 10.000 MHz and the upper passband edge at 10.003 MHz

Then the BFO would be set at 10.003 and then the result is hetrodyned to 14 MHz we have USB ?
Not the way I see it...

For the sake of discussion, lets assume the audio passband goes from dc to 3 KHz, just to make things simple. If we run that into a mixer with a 10 MHz BFO, the resulting principle output will be a double sideband signal centered at 10.000 MHz. Extending upward from the carrier is an upper sideband signal, from 10.000 to 10.003 MHz., and a lower sideband signal, extending from 10.000 downward to 9.997 MHz. The audio spectrum is also inverted on the lower sideband, such that the highest audio frequency, 3 KHz is now the lowest RF frequency, at 9.997 MHz.

Since we want USB on 20 meters or 14 MHz, whatever comes out of the crystal filter will be hetrodyned up in frequency an additional 4 MHz. If this is the USB being passed through the filter, the BFO needs to be at 10.000 MHz so that the USB portion of the DSB signal fits into the passband of the filter, that from 10.000 to 10.003 MHz. When we hetrodyne it is up to 14 MHz 10MHz+4MHz), no inversion takes place or is desired. The lowest audio frequency will be at 14.000 MHz and the higest audio frequency will be at 14.003 MHz.

If we wanted the LSB signal to pass through the filter, we would have to raise the BFO frequency another 3 KHz, so that the USB signal now fits into the crystal filter passband. The USB part of the DSB signal now resides from 10.003 to 10.006 MHz, and will be rejected by the filter.
However, if we hetrodyne to 4 MHz then the result is LSB
I'm not following this part. The VFO is at about 4 MHz. The other signal out of the 2nd mixer would be at 6 MHz nominally (10MHz-4MHz), with the audio inverted, so it would be a LSB signal from 5.997 to 6.000 MHz.
However in both cases the BFO would he on the high frequency side of the filter?
Not the way I see it and have drawn it on my doodle sheets. I have to make pictures of the signals and passbands everytime I do one of these analyses. You'd think eventually I could remember all of it, but my head is too tired to do that anymore.
Please verify or correct me. Thanks, Stan
I hope I've got it right. Comments others??

72 and cheers to all,

Jim, K8IQY

Re: First things first (long post)

Ronald Scifleet <ronaldscifleet@...>
 

Thanks Leonard, I can start building.
Cheers,
Ron,
VK2YQJ

----- Original Message ----
From: kc0wox <bitx@...>
To: BITX20@...
Sent: Sunday, 11 February, 2007 8:30:32 AM
Subject: [BITX20] Re: First things first (long post)

Hi Leonard,
I'm using Rahul's design from his article BITX. The main board that
I have made is 3 inches wide by 8 and a half inches long.
I down loaded his PCB files in word format and printed them to a
Printed Circuit Board Transfer Film on a laser printer. I then laid
the printed film onto a cleaned board then ironed it onto the board
for about 4 minutes. I then peeled off the film then etched and
drilled the board.
So, any layouts for this version of the BITX would be great.

Ron,
VK2YQJ
Ron:
We are working with the same board. The videos may help you when I
catch up.

I just added component location drawings on my web site for the
boards. http://www.golddred gervideo. com/bitx20/ index.htm

One small warning though. I have not built all sections so there may
be errors in them. They are a very good start though.
Leonard
KC0WOX




Send instant messages to your online friends http://au.messenger.yahoo.com

Re: First things first (long post)

kc0wox <bitx@...>
 

Hi Leonard,
I'm using Rahul's design from his article BITX. The main board that
I have made is 3 inches wide by 8 and a half inches long.
I down loaded his PCB files in word format and printed them to a
Printed Circuit Board Transfer Film on a laser printer. I then laid
the printed film onto a cleaned board then ironed it onto the board
for about 4 minutes. I then peeled off the film then etched and
drilled the board.
So, any layouts for this version of the BITX would be great.

Ron,
VK2YQJ
Ron:
We are working with the same board. The videos may help you when I
catch up.

I just added component location drawings on my web site for the
boards. http://www.golddredgervideo.com/bitx20/index.htm

One small warning though. I have not built all sections so there may
be errors in them. They are a very good start though.
Leonard
KC0WOX

Re: BITX20 Kit Progress Report

Tim A. King, Jr. <ag4rz@...>
 

Any more progress?

Tim
AG4RZ

----- Original Message -----
From: ki6ds@...
To: BITX20@...
Sent: Wednesday, January 31, 2007 12:43 PM
Subject: [BITX20] BITX20 Kit Progress Report


Hi guys, just thought I would give you all a progress report on the BITX20
Kit prototypes. Things are going fine, but we have confirmed that there
will be a second round of boards. That is why we build prototypes, grin.
The builders are about 1/3 through building the board. We keep hearing
and seeing things on the list that people want. We are going to produce a
kit on 20 Meters first, as close to the Version 3 schematic as we can be
and still have a good kit. (Sometimes when you go from ugly construction
to a pcb there are issues. We have to find that out before we order
production boards.)

Please have patience and I will keep you updated on the kit progress as we
go forward. I am very excited by the progress so far. 72, Doug






------------------------------------------------------------------------------


No virus found in this incoming message.
Checked by AVG Free Edition.
Version: 7.5.432 / Virus Database: 268.17.15/659 - Release Date: 1/30/2007 9:31 AM

Re: V.3 PCB Layout

Allison Parent <kb1gmx@...>
 

--- In BITX20@..., Rahul Srivastava <vu3wjm@...> wrote:

HI! Allison,
The gain does not changes until thre devices meet the Ft/f > 10
criteria. Unfortunately cheaper devices from the far east do not meet
the published specs as far as Ft is concerned. Bi -directional nature
and additional AC feedback of two stages tends to reduce the gain as well.

That is true but if the stage gain is low as used in the BITX
IF stages then the 10x criteria may be a bit lower.

Sounds like cheaper devices could be really devices that don't
meet spec (rejects). In that case your best calculations are
likely not going to hold as the device is undefined.

BC547s and 2N2222 s have a higher capacitance as well. Just make a
tuned xtal osc of single xtal variety and try out different devices, a
better picture evolves of gain and device add on capacitance. 2N3904
have always worked well in past for me but are not so common as the
547s in this region hence the mod with local components. I am not sure
of other places but here we get 2SC2570A very cheap why take a risk
rather than go ahead with a high Ft device??.

Yes, understood. Most of the 2222s, 3904 and similar have an FT
of around 300mhz or better. But there are a lot of other devices
that easily make 100mhz FT and thats enough for the IF and BFO.

Devices I've tried are 2xc710, 2sc1815, 2sc945, 2sc839, 2sc1674,
2sc1675 and 2sc941 and many more (pulls from old 27mhz CB radios
from the 1980s).

As to device capacitance most small signal transistors are
adaquate for 10mhz region. At higher frequencies it may be
more problematic. However, I've used metal can 2n2222A at
6m as RF amp and even 10-100mw drivers. The trick there is a
50ohm system to make the RC loading less significant. Another
example is I'm using a 2sc1226A which has an FT of 150mhz as
a 10M SSB driver transistor (~.5w output) and it works excellent
though it's not being stressed. The nominal use for that
transistor was 5-15W audio amplifer output stage.

A high FT device is a desireable choice for the RF amp where
noise is also a factor. The 3905 or 2222 is around 6db NF
at best where a better device like the 2n3866, 2n5109, 2sc1252,
2sc2570 will drop that to 3-4db (resistive feedback amplfiers
are inherently noisy). For HF that may not be important but
at 10m and 6m it is more significant.


Allison




Allison Parent <kb1gmx@...> wrote:
--- In BITX20@..., Rahul Srivastava <vu3wjm@>
wrote:

Hi! Dan,
V3 should be stable with 2222 devices as they have lower gain than
3904s. However if the IF stage is made with 3904s keeping the feedback
resistor at 10k should be a good starting point.

The gain sould not change as the amps (see Farhans origional article)
are of the feedback type and the components around the amp set the
gain. The critical parameter is the device FT (frequency where the
device gain is unity [1]) as it could be not less than 5x and
preferable 10x the operating frequency. For the IF and BFO the
2222 or 3904 are about even. I've found 2SC945 and 2SC839s to
work well in most of same circuits.

Where the device used is more cirtical is the RF amp (RX) and the
TX driver and final.

Another reason for high gain is better quality ferrites. Our VU
ones are not as good as Amidon and Fair-rite stuff. Farhan and myself
bought a pack of 500pcs binocular cores for Rs200/ ie 1 cent per core.

The problem of cores is if they are not ferrite and are powered
iron. The wrong core material can hurt performance or make the
tuned circuits have very low Q (or not tune at all). For the IF
and mixers I found the cores sould have a high ui (usually type 43
(ui of 850) ferrite) though type 61 (ui of 125)powered iron will
work with more turns of wire. The problem is if you have unknown
cores you have to try and see.

Should make only a small difference over the tap washers as there
is less unintended coupling to other stages. I tested both and the
difference is small. The ferrite loaded coils require less wire
and are more compact though. I used both FT37-43 (ferrite ring)
for interstage and also tried binocular cores (2hole) and both
produce the same results.

I'm using the board from FAR circuits (they are in the USA) that
is the basic Farhan circuit and layout. I've built one for 6M
and also working on one I've decide will be for 10M. At those
frequencies the devices closest to the antenna are more important.

Regards,
Allison






---------------------------------
The all-new Yahoo! Mail goes wherever you go - free your email
address from your Internet provider.

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