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On Sunday, November 27, 2016 6:22 PM, "Mark Walton k3mrk1@... [BITX20]" <BITX20@...> wrote:

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I dont mind a little drift, I can work with that. 1 khz per min makes it a little difficult to listen to one signal for very long. To tune a single signal, I must tap the tuning control on top till I get it. It wouldnt be so bad on CW, but within a minute the voice becomes unintelligible.

On Sun, Nov 27, 2016 at 12:49 AM, k7tfc@... [BITX20] <BITX20@...> wrote:

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--- wrote :

We starting including the resistors after the reports of the drift. the pads are big enough for you to solder regular 1/4 watt in place of wthe smd resistors (in manhattan style). if you do really want them, drop a mail to and they will post a 'pinch' of them to you for free, though the cost of postage is prohibitive but they have agreed to bear it.? - f

That is indeed very generous, but I hope no North American or European takes advantage of the offer. 1/4 watt resistors are ***far too easy*** to come by on both continents for any sense to be made of sending a "pinch" of them all the way from India! Moreover, it's my understanding that this effort by RF Signals is part of a community fund-raising and money *earning* (as opposed to money *making*) project. That was one of my reasons for buying one of the boards. I'd like to see as much of that money stay in India as possible.

I think there's another issue involved here that bears some thought and discussion. So the BitX40 VFO has some drift? BFD (Big Fat Deal)! I hope I never get to the point either physically or psychologically when having to touch a VFO knob to sharpen the tuning up a bit now and then becomes burdensome or somehow unacceptable. And God forbid I would ever become such a jerk as to mar an otherwise pleasant QSO by pointing out to the other guy--more often than not a total stranger--that he's drifting (or exhibiting some other meaningless "flaw" in his signal) unless I'm **asked** for a detailed signal report.

This ongoing inflation of features and expectations needs some serious reconsideration, reflection, and soul searching. It's made possible by **store-bought** DDS and SDR technology, along with all the feature bloat that goes along with much of it: waterfalls and spectral displays and other means of finding fault with the other-guys transmission.

Sure, lower the bias current by putting in 220 ohm resistors to minimize heating. Take any other reasonable route to maximize the VFO's stablility. Figuring all that out is part of the fun. But if you can't get around to any of that, stick an antenna on the thing and get on the air anyway! If you end up offending the spectrum police, too bad for them!

73,

Todd K7TFC ?

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Did you add it to the red wire or black wire?

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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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so I am at a stop point and need some help from the community. Have a bitx40v3, purchased a qrp-labs vfo. All tested and seem to be working. Could someone help by leeting me know what the IF freq should be set to.?

thanks

art n2ajo

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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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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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so I am at a stop point and need some help from the community. Have a bitx40v3, purchased a qrp-labs vfo. All tested and seem to be working. Could someone help by leeting me know what the IF freq should be set to.?

thanks

art n2ajo

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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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so I am at a stop point and need some help from the community. Have a bitx40v3, purchased a qrp-labs vfo. All tested and seem to be working. Could someone help by leeting me know what the IF freq should be set to.?

thanks

art n2ajo

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Ken,

I set my Arduino sketch to always start on 7.268.500 so when I turn on the Radio/DDS it always displays that, of course it's only displaying that, but it's really outputting 4.730.100 to the VFO. So, 11.998.600-4.700.100 = 7.268.500. Clear as mud?
I know it gets confusing at times.

Joel Caulkins

KB6QVI

Joel Caulkins

KB6QVI

On Dec 7, 2016, at 12:58 PM, Ken Chase chase8043@... [BITX20] <BITX20@...> wrote:

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What is displayed on your DDS? 7.000000 MHZ or 7.001400 MHZ.

73 Ken

On Tue, Dec 6, 2016 at 7:46 PM, Joel Caulkins caulktel@... [BITX20] <BITX20@...> wrote:

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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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so I am at a stop point and need some help from the community. Have a bitx40v3, purchased a qrp-labs vfo. All tested and seem to be working. Could someone help by leeting me know what the IF freq should be set to.?

thanks

art n2ajo

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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@..., 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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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@..., 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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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@..., 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