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Re: T3
P.S. T3 is the reference designator for the BFO transformer in the original BITX schematic.
john ---In BITX20@..., <iam74@...> wrote : There is no T3, either in the schematic nor in the outline diagram. It is an error in reference designators. If I were to guess, in the original on-a-napkin diagram, A.F. included two full mixers and changed the BFO mixer to the one shown, which is the original BITX configuration. Such things happen all the time. Hi. john AD5YE ---In BITX20@..., <riggerswa@...> wrote : can someone show me on a board overlay where t3 is? on the bitx40v3 smd board? |
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Re: T3
There is no T3, either in the schematic nor in the outline diagram. It is an error in reference designators. If I were to guess, in the original on-a-napkin diagram, A.F. included two full mixers and changed the BFO mixer to the one shown, which is the original BITX configuration. Such things happen all the time. Hi. john AD5YE ---In BITX20@..., <riggerswa@...> wrote : can someone show me on a board overlay where t3 is? on the bitx40v3 smd board? |
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Re: avoid the mistake that I made
Baruch Atta
I adjusted the connections so that when I rotate the pot clockwise, the frequency goes up.? Both pots.? I connected a 500 ohm pot in series with the 10K pot. ?the 500 is "bandspread". ? On Thu, Dec 8, 2016 at 6:09 PM, Al Duncan VE3RRD ve3rrd@... [BITX20] <BITX20@...> wrote:
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avoid the mistake that I made
Maybe I should call this post "read the directions"!
After hooking up my BITX40 and turning it on, I noticed a couple of "problems". The volume control didn't do a very good job of adjusting the volume, and the tuning pot only seemed to let me cover a portion of the CW part of 40m (even after adjusting the VFO cap). I decided to compare my wiring with the connection diagram on the hfsigs.com website (should have done this first) and noticed that the wire colors differed from what I had connected. I "assumed" that the red wire went to the wiper on both pots, but it is the brown wire that goes to the wiper. The red and black wires go to each end of the volume and tuning pot. After correcting this error, and then swapping the red and black wires around so the volume increased when I turned the pot clockwise, everything worked! Now I can tune from about 7.020 to about 7.250 MHz. 73 AL - VE3RRD |
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Re: Modifying Bitx20 to use a Si5351
Hi Todd,
I am building the Arduino part as a separate PCB, the ATmega328P plus associated components are going on one PCB with an Si5351 Adafruit board, OLED screen, rotary encoder, buttons, EEProm and beeper attached. This is all currently breadboarded up and working. My PCB is laid out for this part. The other PCB will just be the Bitx20 with the VFO and BFO wires going from the Arduino board to this one. I have been experimenting this afternoon - I plugged the Si5351 directly in to the Bitx20 VFO and BFO input points. The VFO I put in at the base of Q7 and the BFO directly in to the T3 mixer, both via a 0.1uF capacitor. The circuit I am using is the one shown on the following blog post: My initial experiments did appear to work, the signal levels going in to these two places were slightly under the levels when using the original oscillators by approximately 0.2 - 0.3V. I did hear some morse code at around 14MHz but then all the signals appears to fade out for the rest of the day both with the Si5351 and the original oscillators back in place. I am currently working on getting the PCB laid out for the Bitx20 using surface mount components. |
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Re: Modifying Bitx20 to use a Si5351
>> I am creating the PCB myself, it it not a pre-designed one, I am just at the initial stage of re-working my original through hole design in to a surface mount one and so am removing the VFO and BFO circuitry.<< Presuming you're using Farhan's schematic, he has the DDS connector? and signal insertion point shown. No need to examine the existing board. Will you be placing the Si5351 and its associated xtal and I2C level-shifting components directly on your SMD layout or will you use the Adafruit (or EtherKit) breakout board and plug it onto your board? 73, Todd K7TFC |
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New file uploaded to 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 : /Bitx-40p2 ver. KMK/Montaje.jpg Uploaded by : co6bg <co6bg@...> Description : Components You can access this file at the URL: To learn more about file sharing for your group, please visit: Regards, co6bg <co6bg@...> |
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New file uploaded to 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 : /Bitx-40p2 ver. KMK/Montaje Bitx40p2 112x83mm.pdf Uploaded by : co6bg <co6bg@...> Description : Montaje pdf You can access this file at the URL: To learn more about file sharing for your group, please visit: Regards, co6bg <co6bg@...> |
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New file uploaded to 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 : /Bitx-40p2 ver. KMK/Impreso 112x83mm KMK-Bitx40p2.jpg Uploaded by : co6bg <co6bg@...> Description : PCB in word You can access this file at the URL: To learn more about file sharing for your group, please visit: Regards, co6bg <co6bg@...> |
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New file uploaded to 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 : /Bitx-40p2 ver. KMK/ImpresoBitx40p2 112x83mm.pdf Uploaded by : co6bg <co6bg@...> Description : PCB in pdf You can access this file at the URL: To learn more about file sharing for your group, please visit: Regards, co6bg <co6bg@...> |
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Re: Bitx 40 board.
Ah, yes. That is a slightly different problem...
The IF is determined by the VFO frequency +/- the BFO, not the nominal filter frequency. Note that you can get either out of the mixer and the function of the filter is to choose which one to pass. In the BITX40, that is 11.998.600 (roughly actual) - 4.998.600 = 7.000.000 (40m). This is filtered on 40m as LSB because of sideband inversion; the only trouble with it is that it will tune in reverse. (I am sure you have noticed this in the BITX40. It tunes "the right way" around 16 MHz with an analog VFO). In a real-world rig, one still has to adjust the BFO (or the IF offset) slightly to clarify things. Note that by adding another VFO (which is a simple thing to do with a DDS), one can also get other bands: 11.998.600 + 2.002.200 = 14.000.000 (20m). On 20m, it would be direct USB, and the BFO would have to be adjusted to reflect that. Eliamady recognized this on his board by providing 3 caps with diode switching in his BFO. One can tune one to LSB, one to USB, and one to CW (or digital if the bandwidth of the filter were good enough). The VFO was off-board, and could be anything one designs for it. Note that one is tuning for an IF at the actual slope or position in the passband, nothing else. One tunes below the center frequency for USB and vice-versa for LSB for IF+VFO. For IF-VFO, inversion takes place. But, you say, isn't the 11.998.600 frequency below 12 MHz? Yes, it is. But sideband inversion takes place because the IF is more than the VFO! If it were the other way around, the result would be USB, and one would tune the signal to another slope in the filter to pass it. Remember that the actual received or transmitted signal is determined by the mixer output; it is there that the selection is made. Both sidebands are actually available in the chosen IF --- the filter decides which one is passed through. If the received signal is LSB (say) then the USB is gibberish and nothing is lost in the choice. But it also means that we can choose USB if that is where the real signal is...or DSB for that matter. All the 20m BITX rigs I have heard about use an IF+VFO design. It is very difficult to make a wide-ranging analog VFO, even one 1 MHz wide. The only widely-used practical one that has been devised uses an IF around 9 MHz; 9+5 = 14 and 9-5 = 4, hence a 20m/80m pairing. And that one covers only a portion of 80m. One covering several MHz is going to be a nightmare design. But a DDS provides a relatively simple solution...provided one can get the BFO right. john AD5YE? ---In BITX20@..., <chase8043@...> wrote : Thanks John I already have the 5351 running as a VFO and I may in the future also have the 5351 run the BFO. In my sketch I assumed that the "BFO" value meant 12 MHZ, the IF. It should be the actual BFO frequency, in my case 11.9986 MHZ. This would explain why my readout was off slightly. 73 Ken |
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Re: Bitx 40 board.
Thanks John I already have the 5351 running as a VFO and I may in the future also have the 5351 run the BFO. In my sketch I assumed that the "BFO" value meant 12 MHZ, the IF. It should be the actual BFO frequency, in my case 11.9986 MHZ. This would explain why my readout was off slightly. 73 Ken On Wed, Dec 7, 2016 at 10:38 PM, iam74@... [BITX20] <BITX20@...> wrote:
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Re: Modifying Bitx20 to use a Si5351
I am creating the PCB myself, it it not a pre-designed one, I am just at the initial stage of re-working my original through hole design in to a surface mount one and so am removing the VFO and BFO circuitry.
I will look up the board you mentioned and see how the DDS input is implemented there - this should give a me a good idea of what components I need to remove / leave in place on my PCB. Thanks again for the help. |
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Re: Bitx 40 board.
Ken --
You don't really need to set up a DDS BFO. The on-board BFO oscillator is strong and stable. What you probably should do is adjust the BFO frequency directly to suit your ears. (See message #19317; that is what I did with my unit). You can setup a DDS BFO as well, of course; I know you now know how to do that. --? If using a DDS, remember to disable the on-board oscillator; probably removing the BFO crystal is the simplest solution. In fact, injecting the DDS signal into where the crystal was is probably the best all-around solution as to where to do it. Mind the signal level and the frequency. Experiment for the best sound. You probably SHOULD use a DDS for the VFO. Remember to disable the on-board VFO oscillator by removing L4. john AD5YE ---In BITX20@..., <chase8043@...> wrote : I got it. I kept thinking the IF(12 MHZ) was the BFO. So it turns out my BFO is also 11.9986 MHZ. So if I have mine start at say 7.164 MHZ, it's o/p is 11.9986 - 7.164 = 4.8346 MHZ OK back to the DDS LPF and 20M BPF. 73 Ken |
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Re: Calling CQ on 7.285 with BITX
Baruch Atta
Three stations on the BITX 40 NET ?tonight N2CQR KB9MAC W3TTT I opened with my Icom at 100 watts, then switched to the BITX at 7 watts. I then worked W4QNW in South Carolina 550 miles / 875 km (with the BitX).? He was calling CQ DX, but 500 miles is DX for 7 watts, right? Are we up for tomorrow? 73, Joe W3TTT On Tue, Dec 6, 2016 at 5:11 AM, Bill Meara n2cqr@... [BITX20] <BITX20@...> wrote:
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Re: Bitx 40 board.
I got it. I kept thinking the IF(12 MHZ) was the BFO. So it turns out my BFO is also 11.9986 MHZ. So if I have mine start at say 7.164 MHZ, it's o/p is 11.9986 - 7.164 = 4.8346 MHZ OK back to the DDS LPF and 20M BPF. 73 Ken On Wed, Dec 7, 2016 at 4:33 PM, Joel Caulkins caulktel@... [BITX20] <BITX20@...> wrote:
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Todd K7TFC
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