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--- In BITX20@..., "eternalesquire" <eternalsquire@c...>
wrote:

1) Checked. These are 10 ohm resistors. I've made 2 stages so far
and had double checked all values of resistors going in.

Ok, there must be something...

2) I had been using 0.1 microfarad (value code 104) for all of the
capacitors of these units.

Ok,

3) On a hunch that this was a bad type of transistor, I substituted
a 2N2222A transistor. Gain was acutally worse, X6 rather than X10,
so I put it back.

Should have either made no difference or better. Worse is totally
unespected!

I strongly suspect that whatever mistake I am making, I am making it
consistently.

Now, the original schematic specifies 220 Ohm emitter bias resistors
in parallel with the emitter degeneration leg, for 2 of these
units. A 440 Ohm resistor is specified for the unit after the

crystal filter.

When you say 440 did you really mean 470? Thats what was on the
original schematics.

Were the original values wrong?

No they are well chosen.

Should I make DC voltage readings and show them to you?

Ok, just the preselector stage. Use the same component call outs
(IE: Q1 and Q13) as I will use the publish drawings.

Allison
KB1GMX

Hi

On my first BITX (a BITX20) I used PN2222s and also found the gain to be quite
low. After substituting a handfull of 2N3904s my gain became much better.

Another early BITX builder found that his VFO was unstable, until he replaced
a 2N2222 with a 2N3904.

There have been recent suggestions that VHF transistors be used in the IF & RF
sections of the BITX. There seems to be some merit in that idea.

It seems that some providers of 2N2222 & PN2222 maybe assume that any
transistor that is NPN and not something else, is a 2N2222. My 2N2222s that
were purchased from DigiKey were all good in the BITX but those that were
purchased from another source (100 each 2N2222s for $1.50 USD) show very poor
HF gain, but they are just fine for audio applications.

Arv K7HKL
_._

I dont see the problem at all.
If you inject a 3mv signal, and you get a 20mv signal, the circuit is working just fine.

here is how, you need to check the power gain, not the voltage gain.

Now, a voltage gain of 6.6 translates to 6.6 x 6.6 = 44.4 power gain. (assuming that the input and output impedances are the same). That is smack down 16db as promised.

- farhan

Allison,

Here are my AC and DC measurements for the Q3 amplifier circuit.? I
had used a scope to measure rather than my voltmeter, so measurements
are eyeballed.

With R set to 12V from an external power supply.
Anode of diode is 9 V
Cathode of diode/collector of Q3 = 8 V
Base = 3 V
Emitter = 3 V (probably a tad less due to BE voltage drop)

From BFO through an attenuator, I am applying 10.7 Mhz signal of
5mV pp seen by scope injected at junction of input capacitors

25 mV pp same frequency seen at junction of output capacitors.

I get no amplification whatever when power is removed or reversed,
which is what we want.

Except for the AC gain, this appears to be a properly DC biased small
signal transistor amplifier.

On the other sets of amplifier circuits, I see 50 mV pp at junction of
output capacitors.

Could it be that I am using the wrong techniques to view the signal
with my scope, rather than there being a bug in the circuit?? I'm
halfway tempted to try putting this circuit in LTSpice as a sanity check.

Scratching my head in confusion,

The Eternal Squire

---

NEW - crystal clear PC to PC

Allison,

Here are my AC and DC measurements for the Q3 amplifier circuit. I
had used a scope to measure rather than my voltmeter, so measurements
are eyeballed.

With R set to 12V from an external power supply.
Anode of diode is 9 V
Cathode of diode/collector of Q3 = 8 V
Base = 3 V
Emitter = 3 V (probably a tad less due to BE voltage drop)

From BFO through an attenuator, I am applying 10.7 Mhz signal of
5mV pp seen by scope injected at junction of input capacitors

25 mV pp same frequency seen at junction of output capacitors.

I get no amplification whatever when power is removed or reversed,
which is what we want.

Except for the AC gain, this appears to be a properly DC biased small
signal transistor amplifier.

On the other sets of amplifier circuits, I see 50 mV pp at junction of
output capacitors.

Could it be that I am using the wrong techniques to view the signal
with my scope, rather than there being a bug in the circuit? I'm
halfway tempted to try putting this circuit in LTSpice as a sanity check.

Scratching my head in confusion,

The Eternal Squire

Hi,

I just won on Ebay a large lot of 10.7 Mhz Crystals. If anyone wants
to use this intermediate frequency I can provide a matched set of 4
plus a 5th for BFO. This IF would be useful primarly in ITU region
2, where WWB makes it impossible to use 10 Mhz as the IF.

I am willing to sell matched sets on the following terms:

1) I will only sell to people in North or South America, exclusive of
Cuba and other countries that US citizens are forbidden to sell to.

2) You will be getting 4 matched crystals, plus a fifth unmatched
crystal for BFO.

3) Before you send money I will send you an invoice containing exact
measurements for each crystal, including the BFO crystal. This
invoice also contains the exact cost of postage to your destination
depending on available carrier. You are responsible for your own
customs duties, import fees, and excise taxes.

4) Each crystal in the package of 5 will be packed in its own bag
marked with its frequency measurement.

5) SSB matching will be within 100 hz of average frequency for
matched set of 4 where each crystal is measured in series with a 33 pF
silver mica capacitor having 20% tolerance.

6) CW matching will be withing 30 hz of average frequency for matched
set of 4 where each crystal is measured in series with a 33 pF silver
mica capacitor having 20% tolerance.

7) Each crystal matched to SSB specifications would cost $2.00 USD,
so a set of 4 will cost you $8.00 USD.

8) Each crystal matched to CW specifications would cost $5.00 USD, so
a set of 4 will cost you $20.00 USD.

9) Your unmatched BFO crystal comes at no extra cost.

10) Payment shall be made by PayPal, US postal money order, or
International Reply Coupons. Personal checks not accepted. No
exceptions.

I don't believe this is an unreasonable cost for my time and labor to
handmatch crystals, to spare somebody else the same effort of having
to buy a lot and sift through them with a test oscillator and
frequency counter.

If the majority of you disagree, please tell me and I will reconsider.

Thanks,

The Eternal Squire

1) Checked. These are 10 ohm resistors. I've made 2 stages so far
and had double checked all values of resistors going in.

2) I had been using 0.1 microfarad (value code 104) for all of the
capacitors of these units.

3) On a hunch that this was a bad type of transistor, I substituted a
2N2222A transistor. Gain was acutally worse, X6 rather than X10, so I
put it back.

I strongly suspect that whatever mistake I am making, I am making it
consistently.

Now, the original schematic specifies 220 Ohm emitter bias resistors
in parallel with the emitter degeneration leg, for 2 of these units.
A 440 Ohm resistor is specified for the unit after the crystal filter.

Were the original values wrong?

Should I make DC voltage readings and show them to you?

Thanks,

The Eternal Squire



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

Edited. inline comments.

--- In BITX20@..., "eternalesquire" <eternalsquire@c...>
wrote:

I wired up a second stage and checked it against the schematic as I
was doing it, every trace is accounted for.

Another thought..

One possible is that the 10 ohm emitter resistor (in series with
capacitor) is not 10 ohms! It is sometimes easy to get 100ohm
and 10 ohm by error. Rough calculation suggests that might be the

error.

Another source of error is if any of the capacitors are not
the correct value (too small).

I'd also check the transistors used. Is the gain going TX and RX the
same? It could be possible one transistor is shorted collector to
base internally.

Just thinking out loud.

Allison
KB1GMX

Edited. inline comments.

--- In BITX20@..., "eternalesquire" <eternalsquire@c...>
wrote:

I wired up a second stage and checked it against the schematic as I
was doing it, every trace is accounted for.

Another thought..

One possible is that the 10 ohm emitter resistor (in series with
capacitor) is not 10 ohms! It is sometimes easy to get 100ohm
and 10 ohm by error. Rough calculation suggests that might be the error.

Another source of error is if any of the capacitors are not
the correct value (too small).

I'd also check the transistors used. Is the gain going TX and RX the
same? It could be possible one transistor is shorted collector to
base internally.

Just thinking out loud.

Allison
KB1GMX

--- In BITX20@..., "eternalesquire" <eternalsquire@c...>
wrote:

Allison,

No, I intend this to be used as 20M. I just use a colorburst crystal
oscillator for signal tracing, and I used a scope to compare the
incoming and outgoing signals to measure gain.

Ok, just curious.

Either those are very poor quality versions of MPS2222 (defective
lot?) or something is very wrong. Could it be measurement error?

I wired up a second stage and checked it against the schematic as I
was doing it, every trace is accounted for.

I had used ground-plane component support construction. Could that
technique reduce the gain?

That works well you unless you use really long leads.
I do groundplane AKA "dead bug", Ugly or Manhattan style mostly
as I can fabricate faster than creating a PCB first. Also ground
loops are unheard of with deadbug. I've used this method to
frequencies up to 1296mhz!

Allison
Kb1GMX

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

Inline and edited.

--- In BITX20@..., "eternalesquire" <eternalsquire@c...>
wrote:

All,
Next question: I have now finished building the first bidirectional
amplifier after the preselector. I injected a 3 mV signal at
3579 KhZ in each direction, and got out a 20mV phase-inverted
copy of the same signal when power in the correct direction was
applied. The fidelity is good, but the gain stages are not
even a factor of 10. Is this the expected performance?

This is very low gain. The expected should be far higher in the
order of of around 16DB. I would expect to see around 100mv
for 3mv in.

I'm curious why 3.579nmhz? IS thise going to be 80M version?
If so I'd suggest using T50-2(red) ferrite rings for the bandpass
filter or the required turns will be very high.

I am using all parts as specified, for transistors I am using
MPS2222 and for switching diodes I am using 1N4148.

I know these are probably not the best of transistors, but I
want to attempt to duplicate the results per the web article.

Those should be more than adaquate at 4mhz. However, I'd suggest
rechecking your wiring. Make sure the capacitors are in the correct
places.



Allison
KB1GMX

All,

Here is the new archive for BITX20 Engineering diagrams.

I have reposted a new archive, EGR&#92;BITX_REV_C, containing all the
corrections for Revision B diagrams, plus GIF translations done by Rod.

The Eternal Squire

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 : /EGR/BITX_rev_C.zip
Uploaded by : eternalesquire <eternalsquire@...>
Description : BITX20 Engineering Diagrams, Rev C, 21 August 2005. Rev B diagrams + GIFS

You can access this file at the URL:


To learn more about file sharing for your group, please visit:


Regards,

eternalesquire <eternalsquire@...>

Allison,

No, I intend this to be used as 20M. I just use a colorburst crystal
oscillator for signal tracing, and I used a scope to compare the
incoming and outgoing signals to measure gain.

I wired up a second stage and checked it against the schematic as I
was doing it, every trace is accounted for.

I had used ground-plane component support construction. Could that
technique reduce the gain?

Hi,

Orange, pink and purple/violet are common to 10.7 IF coils.

Allison
KB1GMX

For calculate resonant frecuency in used TOKO or FI cans can be used a
practical old know formulae:

F(MHz)= sqrt(25330/(L(uH) * C(pF))) or L(uH)=25330/(F*F(MHz) * C(pF))
or C(pF)=25330/(F*F(MHz) * L(uH)).

73s
Manuel
EA7ARX

--- In BITX20@..., "bambazonke01" <jimandruth@s...>
wrote:

Does anyone know the colour code for TOKO 10.7 Mhz printed citcuit
transformers?
Which are the IF , oscillator and dicriminator colours?
Jim VE3DDY

They are in 10,7MHz:
orange 1? IF 10,7 (This is the can to be used in BITX)
(100pF capacitor in parallel)
green 2? IF 10,7(uncommun) (100pF capacitor in parallel)
pink (discriminator) (without capacitor as usuall)
blue (disciminator used in old radios)
(without capacitor as usuall)

In 455KHz:
yellow 1? IF 455KHz (1nF capacitor in parallel)
white 2? IF 455KHz (1nF capacitor in parallel)
black AM detector (with secondarie) (1nF capacitor in parallel)
black FM narrowband discriminator (without secondarie)
(1nF capacitor in parallel)

Some others Blue used in 27-34MHz (30pF capacitor in paralell)
All other used TOKO Cans with o without paralell capacitor.

Good Luck
Manuel
EA7ARX

Does anyone know the colour code for TOKO 10.7 Mhz printed citcuit
transformers?
Which are the IF , oscillator and dicriminator colours?
Jim VE3DDY

Inline and edited.

--- In BITX20@..., "eternalesquire" <eternalsquire@c...>
wrote:

All,
Next question: I have now finished building the first bidirectional
amplifier after the preselector. I injected a 3 mV signal at
3579 KhZ in each direction, and got out a 20mV phase-inverted
copy of the same signal when power in the correct direction was
applied. The fidelity is good, but the gain stages are not
even a factor of 10. Is this the expected performance?

This is very low gain. The expected should be far higher in the
order of of around 16DB. I would expect to see around 100mv
for 3mv in.

I'm curious why 3.579nmhz? IS thise going to be 80M version?
If so I'd suggest using T50-2(red) ferrite rings for the bandpass
filter or the required turns will be very high.

I am using all parts as specified, for transistors I am using
MPS2222 and for switching diodes I am using 1N4148.

I know these are probably not the best of transistors, but I
want to attempt to duplicate the results per the web article.

Those should be more than adaquate at 4mhz. However, I'd suggest
rechecking your wiring. Make sure the capacitors are in the correct
places.



Allison
KB1GMX

Hello,

Two weeks I finished my experiment with the 9MHz crystal filter design
and reported the results of it in several files in the File-box Ladder
Crystal Filter Design. I dropped a message in the messages box about
it.

Maybe you can start selecting the crystals the way several amateurs
suggested to you. Look at the Excel file to see how I did this for the
9 MHz filter. Selecting the filter is only the first step and doesn't
result in a good filter automaticaly. Select good C's and take care of
matching the filter to the amplifier stages is also very important.

Ashhar Farhan discribed the filter design in "A simple SSB trenceiver",
this article is in the File box. An other (but more difficult) way is
discribed by G3JIR.

What you could do is finish the BITX20 with the calculated C's. After
that you can see the shape by putting a noise source at the antenna and
send the audio to the computer. You can use SpectrumAnalyzer or an
other program to draw the shape of the filter and do some "fine
tuning" with the C's on the filter. A lot of information about this can
you find in earlier messages of this group.

Please show us the result of the filter shape after you finished the
job. Not many amateurs have done so far. Succes.

73

Ruud
PE2BS

--- In BITX20@..., "eternalesquire" <eternalsquire@c...>
wrote:

Hi,

I never saw anything about the original article about this. I've used
the BFO and a frequency counter to measure all my crystals. How
closely do they need to be matched for SSB reception? for CW

reception?

Thanks,

The Eternal Squire

P.S. I am using 10.7 Mhz as the IF

All,

Thanks for the info re crystals, it will come in handy when I am ready.

Next question: I have now finished building the first bidirectional
amplifier after the preselector. I injected a 3 mV signal at 3579 khZ
in each direction, and got out a 20mV phase-inverted copy of the same
signal when power in the correct direction was applied.

The fidelity is good, but the gain stages are not even a factor of 10.
Is this the expected performance? I am using all parts as specified,
for transistors I am using MPS2222 and for switching diodes I am using
1N4148.

I know these are probably not the best of transistors, but I want to
attempt to duplicate the results per the web article.

Thanks,

The Eternal Squire

All,

Thanks for the info re crystals, it will come in handy when I am ready.

Next question: I have now finished building the first bidirectional
amplifier after the preselector. I injected a 3 mV signal at 3579 khZ
in each direction, and got out a 12mV phase-inverted copy of the same
signal when power in the correct direction was applied.

The fidelity is good, but the gain is only a factor of 4. Is this the
expected performance? I am using all parts as specified, for
transistor I am using PN2222.

Thanks,

The Eternal Squire