Date   
Re: Microphone level adjustment question - Update

k9jri@att.net <k9jri@...>
 

I was surprised that nobody appears to be using a scope to set the drive level but that is not unlike the old days :) It appeared as though I might have both overdrive and when overdriven some stability issues in my kit.

So:

Using G8OWB's documentation for PE1BWI's stability mod I added the 220 ohm and the 1,000 ohm resistors. Most of the harshness that I was hearing on the local receiver was gone but there were still strong hints of overdrive.

At this time I set all of the bias pots and the drive pot to their CCW position and performed the necessary alignment adjustments. I was careful to not bring up the drive pot (R83) to far.

Although my Bird43P will not read individual voice peaks it was registering about 8 watts PEP on a steady Ahhhhhh. While all of the roughness in the audio now seems to be gone I will have a good 400 MHz. scope available tomorrow and will take a look to see if it is still flat topping. I suspect that it is.

I will follow up with the results of the scope tests and let you know what the real PEP is on normal voice peaks. Not a lot different than adjusting a Central ELectronics 10B with no test equipment.

I received one comment about RF getting into the electret microphone elements. That comment should have be in a LARGE BOLD font as it is certainly the case with the BitX20A that I have :)

73 - Mike - K9JRI

--- In BITX20@..., "k9jri@..." <k9jri@...> wrote:

When I listen to my Hendricks BitX20A on a local receiver I hear some really rough audio at times. If I use my electret mic it is worse than if I use an old 600 ohm dynamic mic with a DC blocking cap.

Back in the good old days, before ALC, I would use a scope to look at the RF envelope for flat topping but I no longer have a scope. Is there any simple way to detect flat topping other than to look at the output with a scope?

My concern is that if I am NOT flat topping the finals badly then it may be a sign of the instability problem pointed out by Martien (PE1BWI) and I should apply his stability mods.

I would appreciate any input you might have on the proper way to adjust the audio input levels without a scope AND and comments on the likelihood that the is the instability that PE1BWI was talking about.

Oh yes.... the local receiver was not being overloaded. Both the local receiver and the BitX20A were connected to 50 ohm dummy loads and I was listening with headphones to prevent any feedback possibilities.

73 - Mike - K9JRI

Re: Microphone level adjustment question

Arv Evans
 

Mike K9JRI

I find it much more reliable to use a recording device (tape recorder or
PC sound card
based recording) to monitor my own speech via an attenuated receiver.
This gets away
from hearing my own talking as background and the receiver output at the
same time.
This way I can play back the recording multiple times to detect subtle
nuances in quality.

Some electret microphones will pick up and rectify RF, causing rough
sounding audio.
Fixing this may require a 0.001 mfd cap across the microphone terminals
right at the
microphone element itself. Try moving your microphone cord around to
see if it makes
a difference.

Arv K7HKL
_._

On 06/02/2010 07:09 PM, k9jri@... wrote:

When I listen to my Hendricks BitX20A on a local receiver I hear some
really rough audio at times. If I use my electret mic it is worse than
if I use an old 600 ohm dynamic mic with a DC blocking cap.

Back in the good old days, before ALC, I would use a scope to look at
the RF envelope for flat topping but I no longer have a scope. Is
there any simple way to detect flat topping other than to look at the
output with a scope?

My concern is that if I am NOT flat topping the finals badly then it
may be a sign of the instability problem pointed out by Martien
(PE1BWI) and I should apply his stability mods.

I would appreciate any input you might have on the proper way to
adjust the audio input levels without a scope AND and comments on the
likelihood that the is the instability that PE1BWI was talking about.

Oh yes.... the local receiver was not being overloaded. Both the local
receiver and the BitX20A were connected to 50 ohm dummy loads and I
was listening with headphones to prevent any feedback possibilities.

73 - Mike - K9JRI

Re: Microphone level adjustment question

redcatradio2000
 

Mike,

I think the experts here, which I am not one, will tell you to do
Martien's stability mod no matter what. Its not hard to do and may save
you a lot of headaches.

Frank - W4NHJ

On 6/2/2010 9:09 PM, k9jri@... wrote:

When I listen to my Hendricks BitX20A on a local receiver I hear some
really rough audio at times. If I use my electret mic it is worse than
if I use an old 600 ohm dynamic mic with a DC blocking cap.

Back in the good old days, before ALC, I would use a scope to look at
the RF envelope for flat topping but I no longer have a scope. Is
there any simple way to detect flat topping other than to look at the
output with a scope?

My concern is that if I am NOT flat topping the finals badly then it
may be a sign of the instability problem pointed out by Martien
(PE1BWI) and I should apply his stability mods.

I would appreciate any input you might have on the proper way to
adjust the audio input levels without a scope AND and comments on the
likelihood that the is the instability that PE1BWI was talking about.

Oh yes.... the local receiver was not being overloaded. Both the local
receiver and the BitX20A were connected to 50 ohm dummy loads and I
was listening with headphones to prevent any feedback possibilities.

73 - Mike - K9JRI

Microphone level adjustment question

k9jri@att.net <k9jri@...>
 

When I listen to my Hendricks BitX20A on a local receiver I hear some really rough audio at times. If I use my electret mic it is worse than if I use an old 600 ohm dynamic mic with a DC blocking cap.

Back in the good old days, before ALC, I would use a scope to look at the RF envelope for flat topping but I no longer have a scope. Is there any simple way to detect flat topping other than to look at the output with a scope?

My concern is that if I am NOT flat topping the finals badly then it may be a sign of the instability problem pointed out by Martien (PE1BWI) and I should apply his stability mods.

I would appreciate any input you might have on the proper way to adjust the audio input levels without a scope AND and comments on the likelihood that the is the instability that PE1BWI was talking about.

Oh yes.... the local receiver was not being overloaded. Both the local receiver and the BitX20A were connected to 50 ohm dummy loads and I was listening with headphones to prevent any feedback possibilities.

73 - Mike - K9JRI

Re: any usa smdBITX arrivals?

ohwenzelph
 

Mine arrived yesterday, jun 1st, looks great.
jerry aa1of
franconia nh

Re: New file uploaded to BITX20

eplerkeppler
 

Dislexics UNTIE!

--- In BITX20@..., "2E0ZHN" <eliamady@...> wrote:

Hi All,

A small correction to make, the file shows 3 kits for ON7CH, this is incorrect. It should state 1 kit for ON7CH and 2 kits for ON7HC.
You can see why I made the mistake :)

73's Elia

--- In BITX20@..., BITX20@... wrote:


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 : /2E0ZHN smdBITX/smdBITX Group Buy Update 6.pdf
Uploaded by : eliamady <eliamady@>
Description : smdBITX Group Buy Information Rev 6

You can access this file at the URL:
http://groups.yahoo.com/group/BITX20/files/2E0ZHN%20smdBITX/smdBITX%20Group%20Buy%20Update%206.pdf

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

Regards,

eliamady <eliamady@>

Re: New file uploaded to BITX20

Yaya
 

Hi All,

A small correction to make, the file shows 3 kits for ON7CH, this is incorrect. It should state 1 kit for ON7CH and 2 kits for ON7HC.
You can see why I made the mistake :)

73's Elia

--- In BITX20@..., BITX20@... wrote:


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 : /2E0ZHN smdBITX/smdBITX Group Buy Update 6.pdf
Uploaded by : eliamady <eliamady@...>
Description : smdBITX Group Buy Information Rev 6

You can access this file at the URL:
http://groups.yahoo.com/group/BITX20/files/2E0ZHN%20smdBITX/smdBITX%20Group%20Buy%20Update%206.pdf

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

Regards,

eliamady <eliamady@...>

Re: BITX20 SMB

bgbarnett1
 

Elia,

Your link is not working. I found this in the files section (smdBITX
Group Buy Update 6). Is this info correct? If so, it looks like
the kit, including shipping to the U.S., would be about $53.68 .

How do I reserve a Kit?

Will a Moneyorder work for payment?

Where do I send the Moneyorder?

Bob







--- In BITX20@..., "2E0ZHN" <eliamady@...> wrote:

Hi Bob,

I suppose you are referring to the smdBITX for which yes I still have
some kits available. Pricing information is available here:

http://groups.yahoo.com/group/BITX20/files/2E0ZHN%20smdBITX/smdBITX%20Gr&#92;
oup%20Buy%20Update.pdf

73's Elia, 2E0ZHN

--- In BITX20@..., "bgbarnett1" bgbarnett@ wrote:

Hi,

Just happened on some of the posts. It sounds like a kit of parts is
or was available for the SMB.

Is the kit still available? If so, what is the the price? I think I
have found most of the files. Schematics and such. Need as much info as
I can get.

Thank you,

Bob barnett

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 : /2E0ZHN smdBITX/smdBITX Group Buy Update 6.pdf
Uploaded by : eliamady <eliamady@...>
Description : smdBITX Group Buy Information Rev 6

You can access this file at the URL:
http://groups.yahoo.com/group/BITX20/files/2E0ZHN%20smdBITX/smdBITX%20Group%20Buy%20Update%206.pdf

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

Regards,

eliamady <eliamady@...>

Re: any usa smdBITX arrivals?

redcatradio2000
 

Mine arrived today 1 June 2010 and everytinng looks good after inventory.

Frank - W4NHJ

On 5/30/2010 3:04 PM, iam74@... wrote:



--- In BITX20@... <mailto:BITX20%40yahoogroups.com>,
"Doug" <w7rdp@...> wrote:

Arrived in the Seattle, WA, USA area in today's mail.

73, Doug W7RDP
Mine arrived in the Houston area the same day (5/29), and in perfect
condition.

AD5YE
john


Re: difference in VFO between BITX20 and BITX20A: connection of resistor?

larry <ag8o1@...>
 

thks a lot larry

----- Original Message -----
From: kc0wox
To: BITX20@...
Sent: Tuesday, June 01, 2010 1:17 PM
Subject: [BITX20] Re: difference in VFO between BITX20 and BITX20A: connection of resistor?




[ ] L2,
11 turns #26 (8.5 inches) on T376
(yellow) core

[ ] L1,
9 turns (7 inches) #26 on T376
(yellow) core

--- In BITX20@..., "larry" <ag8o1@...> wrote:
>
> COMPUTER CHRASED
> I lost info on L1.L2 turns and size wire on bitx17a? larry AG8O

Re: difference in VFO between BITX20 and BITX20A: connection of resistor?

kc0wox <bitx@...>
 

[ ] L2,
11 turns #26 (8.5 inches) on T376
(yellow) core

[ ] L1,
9 turns (7 inches) #26 on T376
(yellow) core

--- In BITX20@..., "larry" <ag8o1@...> wrote:

COMPUTER CHRASED
I lost info on L1.L2 turns and size wire on bitx17a? larry AG8O

Re: difference in VFO between BITX20 and BITX20A: connection of resistor?

larry <ag8o1@...>
 

COMPUTER CHRASED
I lost info on L1.L2 turns and size wire on bitx17a? larry AG8O

----- Original Message -----
From: Arv Evans
To: BITX20@...
Sent: Friday, May 28, 2010 9:01 AM
Subject: Re: [BITX20] difference in VFO between BITX20 and BITX20A: connection of resistor?



Chris PA2CRX

The BITX20A BFO has been optimized for best quality sine-wave output.
This included taking
output from the tank circuit instead of from the emitter. There is also
the filtering action of
R32 and C91 added to attenuate higher frequency energy. This
arrangement has the effect of
lowering the output voltage and making this voltage somewhat dependent
on impedance
distribution around the feedback loop (L7, C15, C34, C35, C37 and C38).
Some BITX20A
builders have noticed that the VFO output changes as you open or close
C38. This is because
the feedback loop impedance is altered by changing the value of C38.

If one plans to use the BITX20A VFO design at other frequencies, you may
find that the output
voltage might be inadequate if significant change is made to the
impedance of the feedback loop.
If you use Jim Tonne's "BITX_Tune" software to re-design the BITX20A VFO
for other frequencies,
you should always follow through with running the new design in LT-Spice
to show the magnitude
of output voltage with your new design.

Q8 in the BITX20A VFO design is biased to half the supply voltage (9V)
by R33 and R34. This should
then cause the emitter resistor R36 to show ((9/2)-0.6) = 3.9 volts.
With R36 being 2.2K ohms,
then the current through Q8 should be (3.9 / 2200) = 1.8 ma. Q7 is also
biased to 4.5 volts by
R33 and R34, so it's 1K emitter resistor should show a voltage drop of
(4.5-0.6) = 3.9 V, resulting
in an emitter current of 3.9/1000 = 3.9 ma for Q7. Since both Q8 and Q7
use the same regulated
9 volts, the total current drain would be (3.9 + 1.8) = 5.4 ma.
Resistor R35 is 100 ohms, so the
current through it to the 9V Zener diode would be ((12 - 9) /100) = 30
ma. This 30 ma minus the
5.4 ma load from Q8 and Q7 leaves 24.6 ma through the Zener diode, which
is plenty for regulation
purposes. This is 24.6 * 9 = 0.22 watts which explains why that
regulator runs a bit warm.

Remember that you cannot make reliable DC voltage measurements on VFO
circuits with the oscillator
running. What you will see is the average of the AC sine wave and is
dependent on purity of that
waveform. Best way to measure voltages in a VFO is to stop oscillations
by opening the feedback
loop, or swamping it with a 0.1 mfd capacitor...then make the DC
measurements with the stage
operating as an amplifier instead of as an oscillator.

Hope this helps answer some of your questions.

Arv - K7HKL
_._

On 05/28/2010 08:04 AM, vdberghak wrote:
>
> Hi all,
> In my BITX17 I use a VXO. However, I made also the VFO from the
> original schematic. It oscillates directly, however, the voltage on
> the collector is about 6 volt so the zener of 9V1 do not the
> stabilising function... The output is so low, my frequency counter
> does not display the frequency. Enough output for the counter at the
> coil or at the 2K2 resistor.
>
> Then I looked to the schematic of the BITX20A. The 4K7 resistor is not
> connected to the emittor/2K2 resistor but it is connected to the coil!
> (not DC connected at all).
> Is this wrong in the schematic? Or it is wrong in the (original)
> schematic on Farhans site?
>
> If the original schematic is correct, I wonder why the output is so
> low and the current so (relatively) high...
>
> Any comments?
> Thanks,
> Chris, PA3CRX
>
>

Re: Vacation update - Hendricks Qrp BitX20A correction

k9jri@att.net <k9jri@...>
 

The original BFO frequency was 10999.250 rather than 10999.450. can't read my own notes :)

--- In BITX20@..., "k9jri@..." <k9jri@...> wrote:

We just returned from two weeks on "The Isle of Palms", SC where we stayed at the Wild Dunes resort. Band conditions were terrible and the hi rise condo that we stayed in seemed to be a better shielded enclosure than E.F. Johnson used to put around Viking II.

I had two antenna tuners with me. An Elecraft T1 and an SGC-239. The antennas were a 20M dipole connected directly to the T1 and a W3EDP multiband antenna connected to the SGC-239. The 20M dipole was used with the BitX20A and a SWL PSK-20 with N3ZI DDS2 vfo. The W3EDP was connected to my SWL Retro-75, 75M AM rig.

I also had an aluminum MacBook with me for logging and digital modes.

No contacts were made with any of the rigs. The antenna environment was terrible. The 20M dipole was on the balcony (3rd floor) and the W3EDP could only be strung at night.

Some observations about the BitX20A were that I had several probably answers but the comment was that they could not copy my audio. When I would listen to myself on the other radio it always sounded like there was severe RF in my audio. I believe that the BitX20A does not like to be right next to the antenna even though my DC power cord has a ferrite sleeve choke and the front panel mic connector has a ferrite sleeve choke inside the cabinet. I was using a 7.5 AHR Glass Mat battery as my small 2.9A switching supply clobbered to entire band with noise. Again, it was right there with the antenna.

I believe that I also had the BFO frequency set too low and did not have much low frequency audio response. I have reset the BFO to 10999.50 since I returned home and have better LF response. It had been set at 10999.450. I also tested with the rig in the near field of an antenna and found that my electret mike (Heil HM-iC) is much more susceptible to RF than is my D-104/T-UG9. Naturally I had taken the smaller electret mic on the trip.

Digital operation with the PSK-20 was terrible as well due to RF getting into the MacBook. Everything was on a steel table on the deck with a 3' piece of coax connecting the tuner to the rig.

I believe that the important lesson learned was to test the gear with the intended antenna setup to see if it will work. Another lesson was that a laptop and sound device (Griffin iMic in this case) just add fuel to the fire as regards RF interference.

I hope to be in better shape for the next trip as I have a NADC-40 and a PFR-3A ordered from Hendricks QRP. I believe I will be in much better shape with an all-in-one CW rig like the PFR-3A.

Vacation update - Hendricks Qrp BitX20A

k9jri@att.net <k9jri@...>
 

We just returned from two weeks on "The Isle of Palms", SC where we stayed at the Wild Dunes resort. Band conditions were terrible and the hi rise condo that we stayed in seemed to be a better shielded enclosure than E.F. Johnson used to put around Viking II.

I had two antenna tuners with me. An Elecraft T1 and an SGC-239. The antennas were a 20M dipole connected directly to the T1 and a W3EDP multiband antenna connected to the SGC-239. The 20M dipole was used with the BitX20A and a SWL PSK-20 with N3ZI DDS2 vfo. The W3EDP was connected to my SWL Retro-75, 75M AM rig.

I also had an aluminum MacBook with me for logging and digital modes.

No contacts were made with any of the rigs. The antenna environment was terrible. The 20M dipole was on the balcony (3rd floor) and the W3EDP could only be strung at night.

Some observations about the BitX20A were that I had several probably answers but the comment was that they could not copy my audio. When I would listen to myself on the other radio it always sounded like there was severe RF in my audio. I believe that the BitX20A does not like to be right next to the antenna even though my DC power cord has a ferrite sleeve choke and the front panel mic connector has a ferrite sleeve choke inside the cabinet. I was using a 7.5 AHR Glass Mat battery as my small 2.9A switching supply clobbered to entire band with noise. Again, it was right there with the antenna.

I believe that I also had the BFO frequency set too low and did not have much low frequency audio response. I have reset the BFO to 10999.50 since I returned home and have better LF response. It had been set at 10999.450. I also tested with the rig in the near field of an antenna and found that my electret mike (Heil HM-iC) is much more susceptible to RF than is my D-104/T-UG9. Naturally I had taken the smaller electret mic on the trip.

Digital operation with the PSK-20 was terrible as well due to RF getting into the MacBook. Everything was on a steel table on the deck with a 3' piece of coax connecting the tuner to the rig.

I believe that the important lesson learned was to test the gear with the intended antenna setup to see if it will work. Another lesson was that a laptop and sound device (Griffin iMic in this case) just add fuel to the fire as regards RF interference.

I hope to be in better shape for the next trip as I have a NADC-40 and a PFR-3A ordered from Hendricks QRP. I believe I will be in much better shape with an all-in-one CW rig like the PFR-3A.

Re: FLL counter with VCO information

Marcel
 

Hello Farhan, you are right. I think my problem is mainly caused by the shielding of the input BPF and the strong broadband signals here in Europe, coming from my active antenna, which I am using for lissening.
A tuned dipole for 20m would be better, or a good attenuator between the BITX and the active antenna.

Because of the harmonics of the VCO, the harmonics of the mixer and the very strong broadcast signals, leaking along the BPF, I have some birdies and images. With the LPF between it, it improves a lot. But I think it is better to make a good shielding then a LPF.

Marcel

--- In BITX20@..., Ashhar Farhan <farhan@...> wrote:

hmmm,
my mental model is that the diode mixers work by clipping the vfo into
a very distorted, odd-harmonic rich signal. this is because they _are_
non-linear circuits. an LPF that filters out is useful though. we have
grown to a casual addition of the LPF after the VFO 'because doug
(demaw) said so' without much thought of why it is required given that
the mixer would distort it horribly anyway.
try designing the filter to allow the second harmonic (even harmonic)
in by raising it's cut-off a little. if the birdies and the images
return, we would have tested this hypothesis.
- farhan


On Sun, May 30, 2010 at 6:47 PM, Marcel <pe1lnx@...> wrote:



Hi to all,

I have made the BITX20 version 3 with the FLL counter and the Hartley VCO. It all works fine and is very stable. After doing some measurements, I discovered the rich harmonics of the VCO (up to 100 MHz). It is a well known disadvantage of the Hartley design.
So I decided to add a 7-pole LPF between the VCO and the BITX. I have used the SVCFilter freeware program. In my photobook you can see the results of the calculation.
After inserting the LPF, the BITX becomes more quiet. No mixing of strange signals anymore. Before, the first and second harmonic were only 26 and 29 dB down. After the modification, they were more than 60 dB down, and no harmonics up to 100 MHz.
So, if you are using this design, it works well, but take care of the harmonics.

73, PE1LNX

Marcel

Re: BITX20 SMB

Yaya
 

Hi Bob,

I suppose you are referring to the smdBITX for which yes I still have some kits available. Pricing information is available here:

http://groups.yahoo.com/group/BITX20/files/2E0ZHN%20smdBITX/smdBITX%20Group%20Buy%20Update.pdf

73's Elia, 2E0ZHN

--- In BITX20@..., "bgbarnett1" <bgbarnett@...> wrote:

Hi,

Just happened on some of the posts. It sounds like a kit of parts is or was available for the SMB.

Is the kit still available? If so, what is the the price? I think I have found most of the files. Schematics and such. Need as much info as I can get.

Thank you,

Bob barnett

BITX20 SMB

bgbarnett1
 

Hi,

Just happened on some of the posts. It sounds like a kit of parts is or was available for the SMB.

Is the kit still available? If so, what is the the price? I think I have found most of the files. Schematics and such. Need as much info as I can get.

Thank you,

Bob barnett

Re: FLL counter with VCO information

Yannick DEVOS <yannick.devos@...>
 

Hi.

Just to add my two pence worth.
Now my version 3 bitx used a Si570 as LO for the VFO.
The signal is known to be squared with fast rising and falling edges.
Based on the following article from Leonard, I connected it directly to Q7 base, without attenuation nor filtering, but through a minicircuits 1:1 transformer.
http://golddredgervideo.com/kc0wox/bitx/transformers.htm
I have not noticed any images signals but the frequency was not over-populated.
I have only one strong (and pure) carrier around 14.270. It is fixed (not changing with Si570 frequency) and does not disappear if I try to improve shielding.
I think it is perhaps coming from the microcontroller. Some small noises are there also (from the LCD controller I guess) and disappeared with shielding.
I should try to add a choke inductance before the AF to reject RF from coming in the LM386...

I have neither oscilloscope nor spectrum analyser to check what I have at the output, but from the reception side it is ok.
As I told before, my modulation in TX is not as great as I expected, but this can come from other parts (the power supply).
I had no time in the last days to check it again with better filtering.

I was thinking in trying to add a simple 1 cell RC filter with cut-off at 7MHz.
I worry about having too much energy on the 4 MHz harmonics on TX, but for RX no noticeable problem.

73,
Yan.
---
Yannick DEVOS - XV4TUJ
http://capheda.wordpress.com/
http://www.qsl.net/xv4tuj/

Le 30 mai 2010 à 23:13, Ashhar Farhan a écrit :

hmmm,
my mental model is that the diode mixers work by clipping the vfo into
a very distorted, odd-harmonic rich signal. this is because they _are_
non-linear circuits. an LPF that filters out is useful though. we have
grown to a casual addition of the LPF after the VFO 'because doug
(demaw) said so' without much thought of why it is required given that
the mixer would distort it horribly anyway.
try designing the filter to allow the second harmonic (even harmonic)
in by raising it's cut-off a little. if the birdies and the images
return, we would have tested this hypothesis.
- farhan


On Sun, May 30, 2010 at 6:47 PM, Marcel <pe1lnx@...> wrote:



Hi to all,

I have made the BITX20 version 3 with the FLL counter and the Hartley VCO. It all works fine and is very stable. After doing some measurements, I discovered the rich harmonics of the VCO (up to 100 MHz). It is a well known disadvantage of the Hartley design.
So I decided to add a 7-pole LPF between the VCO and the BITX. I have used the SVCFilter freeware program. In my photobook you can see the results of the calculation.
After inserting the LPF, the BITX becomes more quiet. No mixing of strange signals anymore. Before, the first and second harmonic were only 26 and 29 dB down. After the modification, they were more than 60 dB down, and no harmonics up to 100 MHz.
So, if you are using this design, it works well, but take care of the harmonics.

73, PE1LNX

Marcel


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

Yahoo! Groups Links


Re: any usa smdBITX arrivals?

kc0wox <bitx@...>
 

I have a partial assembly manual at http://golddredgervideo.com/kc0wox/bitxsmd/ver4/

It's not complete yet as I haven't finished mine. I add to the manual as I progress along. You might want to wait a little bit on the crystal filter as I'm still working on it. I didn't measure my crystals as Elia did but I think that just "fine tunes" the filter. As soon as I get the bandwidth I want, I will try changing crystals and measureing the results.

You can see the results of my measurements as I make them at http://golddredgervideo.com/kc0wox/bitxsmd/ver4/crystalfiltertest.htm
I will be adding more to the page as I get things worked out. I hope to complete it tomorrow. At that time, I may have some reccomended values to use in the filter. Filter design is kind of a "black magic" kind of thing. I try to use the standard values and then move to others if the results don't measure as I would like them. I am lucky enough to have some equipment to measure the results.

Leonard
http://kc0wox.com

--- In BITX20@..., "iam74@..." <iam74@...> wrote:




--- In BITX20@..., "Doug" <w7rdp@> wrote:

Arrived in the Seattle, WA, USA area in today's mail.

73, Doug W7RDP
Mine arrived in the Houston area the same day (5/29), and in perfect condition.


AD5YE
john