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Re: My second BITX40 has arrived!
L4 is in the center of the board, next to C93. How do you know? Tune to a frequency and put your finger next to it. The VFO will change frequency violently. If you are going to use a DDS, the VFO MUST be disabled. The easiest way to do this is to remove L4 from the board. Personally I would have put the DDS entry into the space between Q8 and Q9. Then the removal of C72 would have made the VFO irrelevant. (This is the easiest way to modify the BITX v.3) Incidentally, even if you decide to remove C72 and insert the DDS here, L4 must still be removed to disable the VFO. The quarters are too close and there will be interference with the VFO running. The DDS level must be adjusted to one that satisfies the mixer --- even if that involves an attenuator or another amplifier.? john AD5YE ---In BITX20@..., <expatrick@...> wrote : I am finding the sensitivity to be very poor with the DDS. ?Did your sensitivity improve when you removed L4? And, is L4 the coil that is right next to the DDS jack? ?I can't see the markings on the board and can't find a high-res image of the board. ? When you "removed" the coil, did you short it or just remove it altogether? tnx de AC3K |
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Re: My second BITX40 has arrived!
you must remove the L4 for the dds to properly work On 07-Dec-2016 10:49 am, "expatrick@... [BITX20]" <BITX20@...> wrote:
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Re: My second BITX40 has arrived!
I am finding the sensitivity to be very poor with the DDS. ?Did your sensitivity improve when you removed L4? And, is L4 the coil that is right next to the DDS jack? ?I can't see the markings on the board and can't find a high-res image of the board. ?
When you "removed" the coil, did you short it or just remove it altogether? tnx de AC3K ---In BITX20@..., <ik8yfw@...> wrote : Thanks, I'll try it in the weekend. Best 73 de Giuseppe, IK8YFW. |
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Re: Bitx 40 board.
Precisely. Each rig is slightly different. You must choose the sound you want to hear, and adjust the signal to fit the slope you want in the passband. If you are happy with it the way it is, leave it alone. Otherwise, adjust the BFO frequency. It usually doesn't take much to effect a large difference. Experiment. Provision is made on the board for that (C103). Aim for the sound you want to hear; the ear is a very fine instrument. I usually tune my Kenwood rig to a frequency, match it with the other rig, and adjust the BFO until they sound the same (assuming the VFO is stable). The 20M BITX is upper sideband. So inductance has to be added to adjust the slope. The BITX40 is lower sideband -- adding (or subtracting) capacitance does the job. Since this is sideband inversion, it really could be done with inductance, but capacitance adjustment is much easier. Thank you, Uma. john AD5YE On Tuesday, December 6, 2016 9:20 PM, "Ashhar Farhan farhanbox@... [BITX20]" wrote:
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There is a longer explanation to this. The crystals we use in the BITX are microprocessor grade. This means that they are not very precise. Uma is the crystal sorter. She takes a bunch of 1000 crystals a day and sorts them by their frequency into different bags. Each board takes its five crystals from any one bag. Hence, the central frequency of each board will be slightly different from another board. The central frequency of the ladder filter moves down from the oscillating frequency of the same crystal. That is why, in a set of matched crystals, one can be directly used as the carrier/beat frequency oscillator without needing any trimmer : it directly sits on the higher side skirt of the filter. The BITX40 board's BFO usually ranges from 11.990.0 to 11.997.0, though in almost all cases it is very close to 11.998.0. The best way to determine the BFO frequency is to take it another ham's shack, tune in the BFO to zero beat on USB or LSB and note the frequency. I use the Rigol scope's built-in frequency counter to measure it off the modulator transformer's primary. So, the IF offset should ideally set to the measured BFO's frequency. These are however, very subjective choices. Given that 2.2 KHz is not an ideal passband, 3 KHz is more like it, setting the BFO will determine how you would like to hear the receiver. Setting it close to the passband will make it bassy, setting it away will make it tinny. Setting it a few hundred hertz away will make it hollow. You get to choose which way you want to make your radio sound bad (harr! harr!) - f |
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Re: New BITX40v3 seams deaf on ssb phone signals
If you attach the antenna, does the noise go up substantially? If yes and if you can hear only CW stations but no SSB then you have to just move the trimmer gently to cover the SSB portion of the band. if the receiver noise is not going up when you attach the antenna, then, more often than not, this is just a problem of T1, T2, T3 being bent in the transit. The tinned portions of the wires from these three transformers often touch each other leading to this deafness. Keep the antenna connected and gently move the wires of these transformers away from each other. This should fix it. - f On Wed, Dec 7, 2016 at 10:26 AM, expatrick@... [BITX20] <BITX20@...> wrote:
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Re: New BITX40v3 seams deaf on ssb phone signals
Mark W
开云体育Someone has probably mentioned this already, but out of the box, I’m not sure it tunes very far into the US phone portion of the band. ? From: BITX20@... [mailto:BITX20@...]
Sent: Tuesday, December 06, 2016 9:33 AM To: BITX20@... Subject: [BITX20] New BITX40v3 seams deaf on ssb phone signals ? ? I just got the new 40 m version three board in the mail three weeks ago. Very pretty packaging I might add. Unfortunately this thing seems ?not to like S9 phone signals in the extra class portion of the 40 m band. It actually doesn't like any voice signals. I can hear some strong CW stations in that portion of the band but no real voice conversations. When I kick my dipole over to any one of my other HF Rigs, ?are your booming voice signals. ?The food suffered no trauma in transit that I can tell and everything seems to be fine.? ? Any ideas now? I'm thinking of throwing a signal generator on it and seeing what I got. |
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Re: Bitx 40 board.
There is a longer explanation to this. The crystals we use in the BITX are microprocessor grade. This means that they are not very precise. Uma is the crystal sorter. She takes a bunch of 1000 crystals a day and sorts them by their frequency into different bags. Each board takes its five crystals from any one bag. Hence, the central frequency of each board will be slightly different from another board. The central frequency of the ladder filter moves down from the oscillating frequency of the same crystal. That is why, in a set of matched crystals, one can be directly used as the carrier/beat frequency oscillator without needing any trimmer : it directly sits on the higher side skirt of the filter. The BITX40 board's BFO usually ranges from 11.990.0 to 11.997.0, though in almost all cases it is very close to 11.998.0. The best way to determine the BFO frequency is to take it another ham's shack, tune in the BFO to zero beat on USB or LSB and note the frequency. I use the Rigol scope's built-in frequency counter to measure it off the modulator transformer's primary. So, the IF offset should ideally set to the measured BFO's frequency. These are however, very subjective choices. Given that 2.2 KHz is not an ideal passband, 3 KHz is more like it, setting the BFO will determine how you would like to hear the receiver. Setting it close to the passband will make it bassy, setting it away will make it tinny. Setting it a few hundred hertz away will make it hollow. You get to choose which way you want to make your radio sound bad (harr! harr!) - f On Wed, Dec 7, 2016 at 8:26 AM, Ken Chase chase8043@... [BITX20] <BITX20@...> wrote:
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Re: Bitx 40 board.
OK I am confused. Isn't the IF 12 MHZ? The 12 MHZ is mixed with a BFO of 11998.8 KHZ giving a 2.2 KHZ audio passband? 73 Ken On Tue, Dec 6, 2016 at 7:46 PM, Joel Caulkins caulktel@... [BITX20] <BITX20@...> wrote:
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Re: Bitx 40 board.
开云体育I set mine to 11998.600 because that was my BFO frequency. Farhan says it should be 11998.800 YMMV. Joel Caulkins KB6QVI On Dec 6, 2016, at 4:36 PM, olsonaj6927@... [BITX20] <BITX20@...> wrote:
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Re: Will try 7.285 MHz with BITX
Bill, Could hear you clearly for about 2 minutes- now it's faded. I called back to your CQ but you may not hear me 5 watts with a hamstick dipole in Winfield, IL- near Chicago. Using a Forty-2 by F6BQU. John KC9OJV From: "Bill Meara n2cqr@... [BITX20]" To: Bitx20 <bitx20@...> Sent: Tuesday, December 6, 2016 6:24 PM Subject: [BITX20] Will try 7.285 MHz with BITX
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at 1930 EST? 0030Z tonight
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Re: Si5351a VFO boards.
It is not just a 2 Mhz offset that you have to change.? The oscillator is used to set the internal pll s in the 5351, and different divider ratios have to set depending on the oscillator frequency.? All si5351 libraries and code I have seen have a place to set the oscillator frequency to either 27 or 25 Mhz.?? In the NT7S library there is also a calibration adjustment that can be applied to make small adjustments to account for any slight difference in? crystal frequency
DuWayne KV4QB |
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Re: Si5351a VFO boards.
If you are using an Arduino to drive your vfo you should be able to write a 2 Mhz calibration offset in the code to accomodate either a 25mhz or 27mhz. Crystal. ?Typically the offset is a few khz as very few crystals are exactly on the marked frequency. ?This is because crystals are classified not only by load capacitance, but also 5ppm, 10ppm, or some op to 50ppm. |
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Re: Si5351a VFO boards.
James Duffey
There is also a hardware solution, you can easily change they 27.000 MHz crystal during the build of Hans’s Si5351a board, or install a 25 MHz TCXO as there are pads on the board for that. The TCXOs at 25MHz are not expensive. Digi-Key has them for $1.65 - Duffey KK6MC
-- KK6MC James Duffey Cedar Crest NM |
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Re: Si5351a VFO boards.
Jack Purdum
Pete, N6QW, is an absolute genius when it comes to building something, as his LBS rig proves. He's forgotten more about electronics than I will ever know. In Tom VFO video, he uses a push button to change the VFO's frequency increment. In the original Forty-9er QST article, that's the way I wrote the code, too. However, I wrote a subsequent article in QRP Quarterly that automatically changes the increment base upon (your own) custom spin rate of the encoder. For me, I have the default set to 100Hz, so I can make very small changes in frequency. However, if I start spining the encode fast (and you define what "fast" is), it automatically changes the increment to 10KHz (or whatever you want it to be). As I approach my goal frequency, the spin rate drops and the code senses that and drops the default back to 100Hz. I find it very convenient. Fun stuff! Jack, W8TEE From: "Mikele Martincic socijalizam1@... [BITX20]" To: "BITX20@..." Sent: Tuesday, December 6, 2016 2:28 PM Subject: Re: [BITX20] Si5351a VFO boards.
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look at that :
here you will find many interesting stuff. 9a3xz,Mikele? 2016-12-06 20:15 GMT+01:00 Jack Purdum econjack@... [BITX20] <BITX20@...>:
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Re: Si5351a VFO boards.
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Todd, I would only say that it is 'falling off a log' easy?if you can
and are willing to program your own code changes
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The?point?of my post was simply to?inform those
amongst?the group?who are?not au fait with carrying out even
basic Arduino or Atmel AVR coding that the respective boards?are not just a
case of plug and play.
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As I said ".....you will need to compensate for which board you are using
within the coding within the relevant .ino sketch file when using an Arduino
based version."
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Of course if you are aiming to use a QRP Labs AVR based VFO board with an
Adafruit Si5350 break out then you will need to be able to deconstruct Han's
machine code which is not written in Arduino?C?.
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73
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Slim G4IPZ
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Re: Si5351a VFO boards.
Be careful using N6QW, Pete Juliano's code from the LBS. The libraries for the SI5351 is incorrect. Don't get me wrong, Pete does fantastic work. Our club did the LBS as a group build and we quickly found problems with the code. 73 Ken VA3ABN On Tue, Dec 6, 2016 at 2:28 PM, Mikele Martincic socijalizam1@... [BITX20] <BITX20@...> wrote:
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Joel Caulkins/N6ALT
DuWayne Schmidlkofer
Tom Clifton
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