Thanks, Arv. FB as usual.
That last reference contains almost everything one ever wanted to know.
But, as before, there are only a few pictures of the mini pro version.
I forgot to mention the one from Robodyne (Actually I didn't mention it)
because it has a CH340g USB interface chip, and not a Mega16U2.
It would works pretty much the same way, but requires a different
driver.
There may be more info as time goes on; these mini Mega2560
boards are quite new. But the connections are all the same as the
Mega2560 V3 (or A3). The only real thing one needs to consider is
ICSP and possibly the crystal. For a 5v board, that should be 16 MHz.
But that doesn't fit with a 12 MHz USB connection. Hmmm...
john
AD5YE
|
Re: limited dynamic range of the BITX40
I'm assuming the HV DC generator is stealing RF from before the transmit LPF,
and that any distortion created by clipping the peaks would be easily filtered harmonics of the transmit frequency.
toggle quoted message
Show quoted text
On Tue, Sep 5, 2017 at 12:15 pm, Jerry Gaffke wrote:
A PIN TR switch would be fast and quiet, much better than relays for CW ops.
That HV DC generator from RF trick is still half baked.
Have never seen mention of it.
Weird, as it seems obvious enough.
Why would it not work?
|
Re: limited dynamic range of the BITX40
Here's a nice publicly accessible webpage on using 1n4007's in a TR switch,?
apparently good for up to 100W.
http://wa5bdu.blogspot.com/2017/03/pin-diode-tr-switch.html
The tough part is that it needs a high voltage supply, higher than the peak RF.
But note that the peak RF voltage is half of the peak-to-peak RF voltage.
We can easily create a DC voltage that is equal to the peak-to-peak RF voltage by hanging a couple diodes and a cap
off the transmit RF, stealing a wee bit of RF power. ?The RF envelope should ramp up slowly enough when you hit PTT
that this DC voltage can keep ahead of the RF peak voltage. ?(If it ramps up too quickly, you splatter into adjacent channels.)
A PIN TR switch would be fast and quiet, much better than relays for CW ops.
That HV DC generator from RF trick is still half baked.
Have never seen mention of it.
Weird, as it seems obvious enough.
Why would it not work?
Jerry, KE7ER
|
managed to get FT8 working using vox circuit and Windows 10 tablet. Thought I blew up the finals but it miraculously recovered
|
Re: Stereo Jack Breakout Board for Bitx40
I like the ground isolations between each signal I/O pair.? I
approve.? :-)
The only comment I would make would be to separate grounds between
the two connectors, in case someone wants to use a non-ground
referenced speaker amp for example.? Something like the 8002:
? (Ask
me how I know about this mistake... ;-)
-Mark
On 09/05/2017 10:08 AM, Kevin wrote:
toggle quoted message
Show quoted text
I did a previous
layout for my setup and it was suggested that a breakout type PCB
would be nice:
Support files in the files section here.
|
Stereo Jack Breakout Board for Bitx40
I did a previous layout for my setup and it was suggested that a breakout type PCB would be nice:   Support files in the files section here.
|
Re: limited dynamic range of the BITX40
In the thread you reference (below) here's a link to the pin diode
handbook they talked about. The link in the article was no good.
Vince.
toggle quoted message
Show quoted text
I'd like to do a uBitx like rig without relays as they seem large and
unreliable, use analog switches and PIN diodes instead, perhaps 1n4007's
for the TR switch. ?? Lots of folks claiming success with the 1n4007 in
that position, including??" ElectronicAntenna Switching" by??Wes
Hayward??in??QEX, May 1995.?? But worth looking at some of the rants here:
??
????
(
)
Specifically this one:
"Since the 1N4007 has been made by probably fifty different companies over
the years, and is offered in epoxy, glass, ceramic packages with square,
round, and hexagonal die, and with die geometry from less than .040 square
to larger than .090 round (and everything between), and may be fabricated
by single diffusion, double diffusion, epitaxial, suprataxial or just
about any other method a manufacturer chooses, nobody having a 1N4007
really has any idea what he has.The 1N4007 is also available as a die
alone, without any package, in several geometries and diffusions.Since its
Cj and trr are unspecified, they vary a lot from fabrication to
fabrication. The really good 1N4007s made 30 years ago by Motorola in
Scottsdale are long gone and now they're all made offshore, to absolutely
no standards.This is why I wouldn't generalize about using a 1N4007 as a
PIN substitute: Some might work great this way, others absolutely won't."
??
That guy strikes me as a bit cranky and opinionated, but he may have
earned the right. ??Apparently worked at Unitrode, and contributed to
their "The PIN Diode Circuit Designer's Handbook". ??I'd pick a few
different 1n4007's from big name manufacturers on Mouser, stick with
whatever brand works best.
As you push toward 30mhz the capacitance across a 1n4007 gets significant,
whereas that $0.25 NXP part is good for several GHz and is designed for
low distortion and a wide adjustment range as an attenuator.
If you look back to my post of a week or so ago, you will see that I
didn't really know what a PIN diode was. ??
So take my opinions with a large grain of salt.
Jerry, KE7ER
??
On Tue, Sep 5, 2017 at 12:54 am, Ashhar Farhan wrote:
yeah. you could even try a 1N4007, at audio frequencies, it will do just
as well. These rectifiers have PIN structure too. They work very well as
attenuators through the HF range.
??
--
Michigan VHF Corp.
|
toggle quoted message
Show quoted text
On Tue, Sep 5, 2017 at 5:52 AM, John Backo via Groups.Io <iam74@...> wrote: In searching for documentation for the W8TEE VFO, I came up with this for the
ATMega2560 board:
There are two versions of the USB board (which is the one Jack uses). One is
called the "Meduino" and the other is branded as the English Creoqode board.
The Meduino is most often unbranded. Apparently these are the same board;
both were probably made in China; the English board was branded by them.
The documentation on the boards is scarce. I did not find a schematic, but presumably
they are smaller versions of the ATMega2560 A3 board, so the schematics should be
about the same. There are 2 "datasheets" on the web for these boards. But be
careful -- the sheet on the Epalsite Wiki is about the USB version but the
one on the AliBaba site (and others) is about the "Inhaos" version, which has
no USB interface and relies on the USB/Serial converter with the six pin connector.
It is called the "Mega 2560 Core Datasheet"
One of the things to watch out for are the ICSP connections. There are 2 on the USB
board; only one is noted as ICSP. The one near the USB plug is also ICSP but is for the
ATMega16U2. Unless you know what you are doing, don't even think about that connection
because the 16U2 takes a special firmware which interfaces the USB and the RX0/TX0
of the 2560. Messing the firmware up destroys the board.? If you are brave and understand ICSP
you can use the labeled ICSP connector to interface with the2560.
Another thing I noticed is that the crystal oscillators for the 2560 and the 16U2 are the same.
The one for the 16U2 is for the USB interface and presumably is 12 MHz. So the one for the 2560 is
also presumably 12 MHz. Another frequency is possible, but would not make sense for a USB interface.
The Epalsite wiki is about the best documentation on this particular board. It has a nice picture
of the general pinout of the board (which has been duplicated a lot elsewhere). Also the Arduino
site has some nice pinout and layout pictures for the ATMega2560 board.
Most of the available boards are from Wideem991, either from China or the US. The Creoqode board
is available in the UK, of course, but also from some US sources. Prices range from about $US13.00
to $US20.00. This for the same board. Prices seem to be coming down somewhat since they were
generally higher a few weeks ago.
john
AD5YE
|
Re: Automatic RF Attenuation Mod for Bitx40
I've modified my Version 1, changing the coupling between the op amps from AC to DC. ?This is the best performer now but my Version 2 works quite well also. ?If you need a drawing that you can see more clearly, email me and I will send it to you. -Jim/ND6P 
|
Re: Crystal matching for the uBITX (was uBITX - A reboot of the old BITX)
the G3UUR test circuit is all that I have used. but that's a start, after that, using the sweeperino, i build and sweep and tweak the values until an acceptable filter shape emerges. experimentation is a large part of filter design.
On Fri, Jun 23, 2017 at 3:28 AM, Master Ice <special@...> wrote:
Hi Ashhar.
?
I assume you use the G3UUR test
circuit?shown in Experimental Methods in RF design or something
similar.
If so, when calculating the values of Cm
and Lm, did you actually measure and include the stray capacitance of the
crystal holder and the wiring to the crystal switch circuitry?
Were the results significant?or are
they so minimal in effect as to be ignored?
?
Many thanks for your time
?
Slim Haines G4IPZ
?
----- Original Message -----
Sent: Thursday, June 22, 2017 5:50
PM
Subject: Re: [BITX20] uBITX - A reboot of
the old BITX
We have to first characterize the crystal. that's measure their
motional inductance and capacitance. i do this using the G3URR's method. it is
a very simple two transistor oscillator. after that, i use the same oscillator
to measure the frequency of each crystal and sort them into bins.
thanks to the bitx40 production, at least for 12 mhz crystals, i don't
have to match them. they are kept prematched in separate pouches. i just dip
into one!
- f
|
Re: uBITX - A reboot of the old BITX
alex,?
it is best that you do a receiver signal test. feed in a 100 mv signal into the antenna. and trace it all the way to the crystal filter output. post the voltages at each point : other side of the lpf, at the mixer output, at the output of the first if, output of thr bandpass etc. my four builds are very sensitive. somethingis not tuned properly. prolly the vhf bandpass filter. - f
On 5 Sep 2017 1:54 pm, < pa1fox@...> wrote: Hi all,
Based on the great description from Ashar I have started to build the uBitx from scratch. Even as far as not using a Raduino, but using standard (Ebay) Arduino Nano board, a standard LCD display from the shelf and a locally bought Adafruit SI5351 board. I have changed some aspects of the design. It's a very nice project to change and work onto. One of the planned changes is to include 6 meters. I expect to need a preamp but that is not my first concern. To suit the tuning range to 52 MHz I have changed the IF to 75 MHz and decided to use tuneable coils for that IF section. The second oscillator is now on 87 MHz to bring the second IF back to 12 MHz.? The first oscillator has a tuning range from 90 to 139 MHz to cover all the HF bands including 6 meters.?
Off course the low pass filter at the input has been redesigned to drop off above 52 MHz. I plan to make four band pass filter sections for the transmitter stage, switched by the software. This will include a dedicated 50 MHz band pass filter. I expect to replace the IRF's by VHF types (RD's). The TX part is not ready yet apart from the bidirectional sections. First I want to have the receiver in working order.
Yesterday the receiver side has started to come to life. My first impressions:
The overall gain is not good yet. Signals of 10 uV are just audible (tested around 7 MHz). I think the circuit around Q70 (audio preamp) needs to be adjusted. I use a BC550 and already needed to increase R50 up to 470k, Biasing of this transistor needs to be further adjusted as the collector voltage is currently down to 2V.. Optimizing this will increase the gain of the audio chain which will also increase the receiver sensitivity.
There are still a LOT of digital spurs received all over all bands, so I need to work on further shielding and grounding of supply leads etc. This will probably become a major part of the time spent to optimize the rig. I might need to use shielded wiring for the I2C connections to the SI5351 and the leads to the LCD.
On my LCD display, the + and - connection of the background leds are swapped. Don't know why but it's good to know there are different connected types out there.
I'm already amazed about the crystal filter. After setting the master calibration and the LSB and USB carrier frequencies, tuning on the band sounds quite nice. Space reservation and plans for an additional 5MHz narrow CW filter are already made.
Beware, on the uBitx INO file, the are some mistakes in the comments. For example the description of the A6 and A7 lines of the Arduino are swapped. A0 is not the PTT line.Took me some time to figure this out as my rig was behaving very strange to the tuning pot which was connected to the keyer input..... I do not have a C++ background but have worked in assembler for PIC and ATMEL processors before. It's a nice learning curve to dig into the software and figure things out. This is definitely necessary in order to do my changes.
My housing is small, about the same size in width and depth as the one used in Ashar's youtube video but about half the height. My copper clad PCB is mounted about half the way in height so I have both sides to build on. This is necessary as I also plan to include a 12V battery back from 10 NiMH penlights in the box also.?
Don't know if it's going to work at the end, but hey, that's part of the hobby.
73, Alex
PA1FOX
|
Is there any info on T9, T10 and T11 of the uBitx? All I could find in
Ashhar's write up on it was that transmit inductor details would be coming
soon - unless he was only referring to the missing details of the LPF
inductors and the info I'm looking for is there and I'm just not seeing it
(very possible).
Thanks!
Vince.
--
Michigan VHF Corp.
|
Re: limited dynamic range of the BITX40
I'd like to do a uBitx like rig without relays as they seem large and unreliable, use analog switches and PIN diodes instead, perhaps 1n4007's for the TR switch. ? Lots of folks claiming success with the 1n4007 in that position, including?" ElectronicAntenna Switching" by?Wes Hayward?in?QEX, May 1995.? But worth looking at some of the rants here:
? ??
Specifically this one:
"Since the 1N4007 has been made by probably fifty different companies over the years, and is offered in epoxy, glass, ceramic packages with square, round, and hexagonal die, and with die geometry from less than .040 square to larger than .090 round (and everything between), and may be fabricated by single diffusion, double diffusion, epitaxial, suprataxial or just about any other method a manufacturer chooses, nobody having a 1N4007 really has any idea what he has.The 1N4007 is also available as a die alone, without any package, in several geometries and diffusions.Since its Cj and trr are unspecified, they vary a lot from fabrication to fabrication. The really good 1N4007s made 30 years ago by Motorola in Scottsdale are long gone and now they're all made offshore, to absolutely no standards.This is why I wouldn't generalize about using a 1N4007 as a PIN substitute: Some might work great this way, others absolutely won't."
?
That guy strikes me as a bit cranky and opinionated, but he may have earned the right. ?Apparently worked at Unitrode, and contributed to their "The PIN Diode Circuit Designer's Handbook". ?I'd pick a few different 1n4007's from big name manufacturers on Mouser, stick with whatever brand works best.
As you push toward 30mhz the capacitance across a 1n4007 gets significant, whereas that $0.25 NXP part is good for several GHz and is designed for low distortion and a wide adjustment range as an attenuator.
If you look back to my post of a week or so ago, you will see that I didn't really know what a PIN diode was. ?
So take my opinions with a large grain of salt.
Jerry, KE7ER
?
On Tue, Sep 5, 2017 at 12:54 am, Ashhar Farhan wrote:
yeah. you could even try a 1N4007, at audio frequencies, it will do just as well. These rectifiers have PIN structure too. They work very well as attenuators through the HF range.
?
|
BITX QSO Night, Sunday, September 10, 7pm Local Time, 7277 kHz in North America, 7177 kHz elsewhere
BITX QSO Night, Sunday, September 10, 7pm Local Time, 7277 kHz in North America, 7177 kHz elsewhere
Join us as we make contacts from BITX40 to BITX40 on 7.277 MHz in 40 meters!
This is a worldwide event for BITX40 stations starting at 7pm in each time zone. To participate, call CQ BITX on Sunday, starting at 7pm your local time. The BITX QSO Night continues through the evening and conditions usually improve after sunset, so it is worthwhile to participate later in the evening.
Suggested Best Operating Practices:
Work at QRP power levels unless conditions require more power.
Call and listen for CQ BITX on the hour and every quarter hour.
It is helpful if you call CQ BITX with your callsign, name and location.?
Repeat your callsign a number of times during your CQ BITX and during QSO's.
Start a QSO by confirming the callsign, location, name and signal report of the other operator.
Say the callsign, name and location of the other operator so others can hear.
If the frequency is busy, avoid long conversations.
After your initial QSO is complete, ask if there are any other stations who would like to contact.
Report your QSO's, discuss propagation, noise, signal reports, audio reports, antenna type, etc. in this thread.
This is an undirected, scheduled event.? The BITX QSO Night relies on you to call CQ BITX to initiate contacts with other stations, so warm up that final and transmit a few calls on Sunday evening.? Talk to you then!
|
Re: Auto RF Attenuator for Bitx40, Version 2
Here is the drawing with the 47 ohm resistor added to match the BPF. ?Tested and works well. Jim/ND6P 
|
I recommend checking R131 and R141 and all the resistors around Q13,
Q14.
When I checked the board with IR imager FLIR I found the resistors
141/142/143 getting quite hot. 40-50C, and a few boards have
had failures in these resistors.
Raj
At 05/09/2017, you wrote:
toggle quoted message
Show quoted text
Try checking the main board for
any components that are bad. I have heard of some boards being damaged.
In all possibility, it's probably the IRF510. If you need any I believe I
have some in a parts bin from my father when he was building a QRP cw
rig. It's a part from mouser so it should be good. I'll have to find it
though my lab is a mess.
Ian Litchfield KD2IXL?
On Sep 5, 2017 2:20 AM, "Nemo"
<paulswift6@...>
wrote:
- These questions and answers al all very interesting. Now I have mine
working but only 2 watts RF output when I shout at it that is. Im making
an proved mic amp to get a bit more audio drive as it looks a bit low. If
I can get 4 watts with 12 volt FC input I will be happy.
- but I think the 510 is a bit soft and that's the main reason for a
low output.
- kind regards
- Paul.(HS0ZLQ G0MIH)
|
The large knobs are from the junk box. They were given to me by another ham years ago, in a box of small parts.?
|
Just another aside, I just want to say how much I am enjoying this group. I'm part of a few online ham groups and none of them are as active and helpful to each other as this one is. I appreciate what is going on here and happy that I found such an involved community! Ian Litchfield KD2IXL
On Aug 29, 2017 9:57 PM, "Arv Evans" < arvid.evans@...> wrote: 8-)
Sent from my Verizon, Samsung Galaxy smartphone
-------- Original message -------- Date: 8/29/17 6:18 PM (GMT-07:00) Subject: Re: [BITX20] OT
Dang! Spied and tried "chats" in the sidebar (not obvious, but will have to learn that!) with a reply composed but not sent, and now can't get it back :( Here goes...
I use RSS for alerts (Akregator) and by link to Firefox and website. Not missing functionality or content, can copy and paste at will ... Just that Groups.io doesn't do emoticons (they add expression to communication) or interwork with (the likes of) Messenger for OT Chat (could be a right-click on name?). Haven't tried email client for RSS - that'd mean leaving Thunderbird running where Akregator runs as a daemon.
Still immensely grateful for what we have / get..
73
Dex ZL2DEX
|
In searching for documentation for the W8TEE VFO, I came up with this for the
ATMega2560 board:
There are two versions of the USB board (which is the one Jack uses). One is
called the "Meduino" and the other is branded as the English Creoqode board.
The Meduino is most often unbranded. Apparently these are the same board;
both were probably made in China; the English board was branded by them.
The documentation on the boards is scarce. I did not find a schematic, but presumably
they are smaller versions of the ATMega2560 A3 board, so the schematics should be
about the same. There are 2 "datasheets" on the web for these boards. But be
careful -- the sheet on the Epalsite Wiki is about the USB version but the
one on the AliBaba site (and others) is about the "Inhaos" version, which has
no USB interface and relies on the USB/Serial converter with the six pin connector.
It is called the "Mega 2560 Core Datasheet"
One of the things to watch out for are the ICSP connections. There are 2 on the USB
board; only one is noted as ICSP. The one near the USB plug is also ICSP but is for the
ATMega16U2. Unless you know what you are doing, don't even think about that connection
because the 16U2 takes a special firmware which interfaces the USB and the RX0/TX0
of the 2560. Messing the firmware up destroys the board. If you are brave and understand ICSP
you can use the labeled ICSP connector to interface with the2560.
Another thing I noticed is that the crystal oscillators for the 2560 and the 16U2 are the same.
The one for the 16U2 is for the USB interface and presumably is 12 MHz. So the one for the 2560 is
also presumably 12 MHz. Another frequency is possible, but would not make sense for a USB interface.
The Epalsite wiki is about the best documentation on this particular board. It has a nice picture
of the general pinout of the board (which has been duplicated a lot elsewhere). Also the Arduino
site has some nice pinout and layout pictures for the ATMega2560 board.
Most of the available boards are from Wideem991, either from China or the US. The Creoqode board
is available in the UK, of course, but also from some US sources. Prices range from about $US13.00
to $US20.00. This for the same board. Prices seem to be coming down somewhat since they were
generally higher a few weeks ago.
john
AD5YE
|
Try checking the main board for any components that are bad. I have heard of some boards being damaged. In all possibility, it's probably the IRF510. If you need any I believe I have some in a parts bin from my father when he was building a QRP cw rig. It's a part from mouser so it should be good. I'll have to find it though my lab is a mess. Ian Litchfield KD2IXL?
On Sep 5, 2017 2:20 AM, "Nemo" < paulswift6@...> wrote: These questions and answers al all very interesting. Now I have mine working but only 2 watts RF output when I shout at it that is. Im making an proved mic amp to get a bit more audio drive as it looks a bit low. If I can get 4 watts with 12 volt FC input I will be happy.
but I think the 510 is a bit soft and that's the main reason for a low output.
kind regards
Paul.(HS0ZLQ G0MIH)
|
tom van der meer
Smitty, N6MTS
Kevin
Raj vu2zap