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Idea for future versions of BITX
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Klaus Hirschelmann
In case maybe one day there will be plans for later versions of BITX, what about including the Si5351 DDS already on board and using pluggable BPF- and LPF-Filters like e.g. those offered by QRP-Labs? ? By doing this, making at least single band radios for a lot of our ham bands could be simplified enormously. Klaus, DJ7OO ? ? ?? |
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I am not so sure that this is a good idea.
If one reads the comments about the various DDS units, a common problem area is controlling the noise. Putting the DDS on the same board as the rest of the rig would produce an inflexible layout which may or may not be problematic. The chances are very good that it would be... In a way, it is the inverse of the problems associate with something like the AD8307. That device is so sensitive to such a wide range of signals that it is mandatory to shield it away from the rest of the circuits. With a wide-ranging DDS/PLL unit, one might produce things like birdies which are very hard to trace and isolate. It's hard enough to think about designing a single (or dual) IF rig covering all of HF with a wide-ranging VFO and getting it right. Even the best of the HF receivers (like the Sangean) have birdies. One can hear them just by tuning through the whole range... Why invite trouble? john AD5YE |
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Putting an Si5351 down does not make it inflexible, it can always be disabled (like that analog VFO). ?The SoftRock guys have an Si570 on some of their boards, but they took great pains to keep out any digital hash coming from the I2C host that drives it. ?Could be that a small processor on the radio board would be better than an arduino, as the board designer could include series resistors to keep edge rates down and choose crystal frequencies that won't interfere. ?And caps and ferrite beads and perhaps shielding. ?Hard to say what will make the most sense for a $59 transceiver. Jerry, KE7ER |
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Changing the processor to something like a Teensy would allow for more digital modes to be added.? As it stands, CW is about all the Arduino is able to decode.? For something like PSK-31 more clock cycles and a better ADC are required.? I haven't checked the pin-out, but I would think that a few jumpers or even a PCB buffer would be enough to swap the Nano for some other development board.? This would also open up more options for digital filters and user interfaces.
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Jack Purdum
Hi John: I agree that keeping the DDS and microcontroller off the main PCB is a good idea. Experimenting with different controllers would be easier. The new Teensy 3.6 blows the Arduino family out of the processing water. It has 1GB of flash, 256K of SRAM, and 4K EEPROM and is clocked at 180MHz. It has two ADC's at 13 bit resolution and 2 DAC's at 12 bit resolution. True, it's more expensive (under $30), but is worth it if you need the horsepower. While I haven't tried coding too many things with it yet, so far everything I've tried using the Arduino IDE has worked. How cool would it be to have a waterfall display nad some other SDR features with the BITX40?! Jack, W8TEE From: John VA7JBE via Groups.Io <va7jbe@...> To: [email protected] Sent: Saturday, January 14, 2017 1:39 AM Subject: Re: [BITX20] Idea for future versions of BITX Changing the processor to something like a Teensy would allow for more digital modes to be added.? As it stands, CW is about all the Arduino is able to decode.? For something like PSK-31 more clock cycles and a better ADC are required.? I haven't checked the pin-out, but I would think that a few jumpers or even a PCB buffer would be enough to swap the Nano for some other development board.? This would also open up more options for digital filters and user interfaces. Keeping the DDS and micro controller/processor separate from the main board allows for more flexibility in this regard, and I'd be happy to leave it that way.? On-board refinements for the BitX40 that stick with the original design goal of making a board for experimentation and customization might include adding even more places for people to plug into the signal, like in the IF, or refining what's already there (widening the bandwidth of the crystal filter comes to mind.) |
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the teensy has a great audio shield as well! On 14-Jan-2017 10:09 pm, "Jack Purdum via Groups.Io" <econjack=[email protected]> wrote:
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¿ªÔÆÌåÓýI don't think it'll take long for the Chinese to copy the teensy and start offering it for 5 bucks:-) Joel? KB6QVI On Jan 14, 2017, at 8:39 AM, Jack Purdum via Groups.Io <econjack@...> wrote:
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Jack Purdum
I keep waiting to see a knockoff, but, unlike the Arduino family, I don't think the Teensy is Open Source. If there is a knockoff for any Teensy, I'd appreciate it if someone would post the URL for us all. Jack, W8TEE From: Joel Caulkins <caulktel@...> To: [email protected] Sent: Saturday, January 14, 2017 12:20 PM Subject: Re: [BITX20] Idea for future versions of BITX I don't think it'll take long for the Chinese to copy the teensy and start offering it for 5 bucks:-) Joel? KB6QVI
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The idea of having one board with all the basic functions on it and adding plug in BPF and LPF filters to change operating bands has merit . This would allow hams from all over the world to "plug in " the filters for the ham band that is the most popular and active in their part of the world. ?For example , I would like to be able to operate 160 m QRP at night as there is quite a bit of activity on the west coast of USA and Canada at the moment on 160 . The advantage of plug in modules., is that you would have the option to go back to "40m " if one wanted to do so . The alternative , would be to come up with a conversion?list specifying the parts to be replaced and the values required for operation of the BITX40 board on the different ham bands. The issue with this is that the parts required are not always readily available locally to a lot of hams around the world. ?I view the BITX40 as a Global Experimental Radio Project ( GERP ) and as such , to maximize the opportunities to experiment with the board , I think a conversion kit to other radio bands makes the most sense. If a conversion kit was made available, 160 M conversion (for example) . ?Once the conversion kit was received , one could modify the BITX board following some basic instructions to the new band of interest , with the option to convert back if one wanted to do so at a later date . The addition of conversion kits for other bands, should enhance the amount of interest in the BITX40 as a global basic platform for amateur radio enthusiasts to experiment with around the world.? Any additional thoughts on this ? |
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I gather what you are saying and think that any experimentation is a great thing. Perhaps those that mod their Bitx40 for other bands would share their data/results. That way those interested in a particular band could build for that band. If however you are going multiband there is already several designs out there that accomplish that with little or no extra component count and a board the same size or not much bigger. Most people are probably going to use an Arduino based AD9850 or Si5351 to run their VFO so band switching BPF/LPF is taken care of right there. Several different designs of BPF and LPF boards are already in use. Yhis leaves really only the PA and maybe some controls to figure out. I dont know if you have looked at it yet or not but there are two files under the files section that you may want to peruse. One is by Elia Mady M0ZHN and is a BitX based Multi Band exciter. The other is a BitX based exciter by Andy G6LBQ. I myself at the moment am working on a SMD board based on Elia's design without the audio amp or AGC or Microphone amp so that I may experiment with different designs and see what works best for me. The board is 4in by 4in. I am also working on a board for myself based upon Andy's Multband BitX that uses SMD. ?Maybe you can get some ideas or tips from their files. I have had some good reading from them. I do apologize if you already knew this or had seen it already.? Best wishes and good luck with all your projects. ? Ian K3HQL On Sunday, January 15, 2017 2:27 PM, VE7BEE <obeebe@...> wrote: The idea of having one board with all the basic functions on it and adding plug in BPF and LPF filters to change operating bands has merit . This would allow hams from all over the world to "plug in " the filters for the ham band that is the most popular and active in their part of the world. ?For example , I would like to be able to operate 160 m QRP at night as there is quite a bit of activity on the west coast of USA and Canada at the moment on 160 . The advantage of plug in modules., is that you would have the option to go back to "40m " if one wanted to do so . The alternative , would be to come up with a conversion?list specifying the parts to be replaced and the values required for operation of the BITX40 board on the different ham bands. The issue with this is that the parts required are not always readily available locally to a lot of hams around the world. ?I view the BITX40 as a Global Experimental Radio Project ( GERP ) and as such , to maximize the opportunities to experiment with the board , I think a conversion kit to other radio bands makes the most sense. If a conversion kit was made available, 160 M conversion (for example) . ?Once the conversion kit was received , one could modify the BITX board following some basic instructions to the new band of interest , with the option to convert back if one wanted to do so at a later date . The addition of conversion kits for other bands, should enhance the amount of interest in the BITX40 as a global basic platform for amateur radio enthusiasts to experiment with around the world.? Any additional thoughts on this ?
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¿ªÔÆÌåÓýI like the idea of a ¡°building block¡± BITX that can be ordered at a low price from Ashhar¡¯s team. ? But look at from another direction. Ashhar and his colleagues supply us with a low cost, tested, fully functional QRP transceiver board for one band. That band is chosen with the present propagation situation in mind. The basic concept has a lot of room for improvements, hacks, modifications and experiments. that we can perform ourselves. Not all of us have the same capabilities to do so of course, but with all the support in this group from other group members who share their results with us, we all could do something if we want more than the basic features. ? We should be very reluctant to come up with an extensive wish list. I am a development engineer myself, I know how much time, energy and also money is to be invested in a project like this. So let us be grateful for what Ashhar is doing now and not press him in doing more than he wants himself. ? Cor PA4Q ? From: [email protected] [mailto:[email protected]] On Behalf Of VE7BEE ? The idea of having one board with all the basic functions on it and adding plug in BPF and LPF filters to change operating bands has merit . This would allow hams from all over the world to "plug in " the filters for the ham band that is the most popular and active in their part of the world. ?For example , I would like to be able to operate 160 m QRP at night as there is quite a bit of activity on the west coast of USA and Canada at the moment on 160 . The advantage of plug in modules., is that you would have the option to go back to "40m " if one wanted to do so . The alternative , would be to come up with a conversion?list specifying the parts to be replaced and the values required for operation of the BITX40 board on the different ham bands. The issue with this is that the parts required are not always readily available locally to a lot of hams around the world. ?I view the BITX40 as a Global Experimental Radio Project ( GERP ) and as such , to maximize the opportunities to experiment with the board , I think a conversion kit to other radio bands makes the most sense. If a conversion kit was made available, 160 M conversion (for example) . ?Once the conversion kit was received , one could modify the BITX board following some basic instructions to the new band of interest , with the option to convert back if one wanted to do so at a later date . The addition of conversion kits for other bands, should enhance the amount of interest in the BITX40 as a global basic platform for amateur radio enthusiasts to experiment with around the world.? Any additional thoughts on this ? |
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I love the idea of a conversion kit I'd order one if it was made available. 73 Ken VA3ABN On Sun, Jan 15, 2017 at 3:27 PM, VE7BEE <obeebe@...> wrote:
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The input/output filter area could have a line of through hole pads where one can solder a pin socket like
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that of a pro IC socket. These holes should be exactly multiples of 0.1". Small low profile daughter boards can be made to take different band filters. With this you can actually switch bands with ease. something like these, here we get long single line strips. At 16/01/2017, you wrote:
The idea of having one board with all the basic functions on it and adding plug in BPF and LPF filters to change operating bands has merit . This would allow hams from all over the world to "plug in " the filters for the ham band that is the most popular and Any additional thoughts on this ? |
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If you want a board like this, check out the MST3 kit. Rgds, ? On 2017-01-16 07:27 AM, VE7BEE wrote:
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Continuing on the idea of a conversion kit : What one would be the easiest to do ? 80 M ? 20 M ? ?If this is the case , what would be the minimum requirements for modification to 80 m ? for example . If some one has information on a conversion to 80 m please share what you have . The BITX40 Team I am sure have their hands full and do not want anyone to think this idea is to put pressure for a secondary band kit . that is not the case. ?I am thinking that if there is enough interest in a conversion kit , maybe some of us can put our heads together and come up with a parts list for a couple of different bands to start with . Rewinding the existing toroids or getting some extra toroids and rewinding them should not be too hard. I have already played with the VFO and it is still reasonably stable at 10 MHZ . ( conversion to 160 M) . I have not had time to sit down and figure out the LPF and BPF as of yet.?
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Over the last few days, someone posted they had it working on 180m and someone else on 80m. I don't recall who it was without going through the postings. Sometime ago, Ashhar hinted at replacing the 100 pf caps of the BPF with 22pf for 20m. So I am in the process of building an off-board BPF for 40m/20m. I am just waiting for caps to arrive to try it. I know almost nothing on BPF/LPF design so I have been doing some reading. I had a friend model the present 40m and 20m in Ltspice, which I don't understand how to use, and said the plots were very good. So that is where I am with the Bitx40. 73 Ken VA3ABN On Sun, Jan 15, 2017 at 11:25 PM, VE7BEE <obeebe@...> wrote: Continuing on the idea of a conversion kit : What one would be the easiest to do ? 80 M ? 20 M ?? If this is the case , what would be the minimum requirements for modification to 80 m ? for example . If some one has information on a conversion to 80 m please share what you have . The BITX40 Team I am sure have their hands full and do not want anyone to think this idea is to put pressure for a secondary band kit . that is not the case.? I am thinking that if there is enough interest in a conversion kit , maybe some of us can put our heads together and come up with a parts list for a couple of different bands to start with . Rewinding the existing toroids or getting some extra toroids and rewinding them should not be too hard. I have already played with the VFO and it is still reasonably stable at 10 MHZ . ( conversion to 160 M) . I have not had time to sit down and figure out the LPF and BPF as of yet.? |
Joel Caulkins/N6ALT
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