Hi Group, My BitX has never really been able to show much of a jump in current when performing the loud HELLO test. ?With my fiddling, I can now not get any current increase when talking, so may have damaged something. ? I will describe my testing methodology here, in the hope that the community can guide me to the next steps of troubleshooting. Glossary
- RX - The radio is receiving.
- TX - The radio is transmitting.
- TXM - The radio is transmitting with a modulating signal.
- OSC1 - Oscilloscope CH1
- OSC2 - Oscilloscope CH2
- mV - Unless otherwise specified (e.g. across), all measurements are taken between the test point and GND.
Test setup
- I have my computer generating a 400 Hz sine wave with a 4 mV swing. ?(I came to these input settings as they match the readings I got at the mic input (MIC1) when offering a loud "HELLO" into the mic).
- I have one multimeter measuring current, connected in-line with the positive power line between my 12V power supply and the BitX's power jack.
- I have OSC1 connected to the mic input, to monitor the input source.
- I have OSC2 connected that I'm using to probe.
- I have another multimeter which I use for precise readings.
- The antenna is connected to a 50 Ohm dummy load.
Measurements
- At RX, the BitX draws 115 mA.
- At TX, the BitX draws 330 mA.
- At TXM, the BitX continues to draw a steady 330 mA. ?No change from TX without modulation.
- Across MIC1 shows 4 mV in both TX and RX.
- Before R126 shows 0 mV in TX.
- Before R126 shows 11 mV in TXM.
- Across R126 shows 11 mV in TXM.
- Between before R126 and after D5 shows 0.5 mV in TX.
- Between before R126 and after D5 shows 11 mV in TXM.
- Across each of R43, R44, R53, R54 shows 0.5 mV in TXM.
Discussion
- I believe measurement 7 is the audio signal that gets added to the balanced modulator (D5).
- I would have thought that I should see an amplified signal across both R43 and R54, but am seeing nothing.
At this point I'm stuck, and don't know where else to go. ?I can see that audio is getting through the audio amp and to the balanced modulator, but the schematic is unclear to me where I should next measure. ?Any assistance would be appreciated. My time zone is GMT +10, and happy to arrange an EchoLink sched if that will be an easier way to diagnose. Kind regards, ? Lance P.S. ?If anyone knows where there is a text searchable copy of the schematic and board layout, that would greatly help finding components to diagnose.
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Re: Adding switchable USB and LSB to the Bitx40
Now I get it. Thanks.? I'm new to this SSB stuff - AM and FM are much simpler! :)
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Re: Front End Protection Diodes?
Here's one such list: ? /g/BITX20/message/28827I suppose I could edit it some and dump it into the files section, or maybe into the wiki. If you want a list that only has stuff in it that you care about, then go write it. Some scheme for current limiting should be added, perhaps separate fuses for the IRF510 and everything else. Also a voltage regulator to keep things to 12.0 volts for all but the IRF510, and reverse voltage protection.? ?? Jerry, KE7ER
On Fri, Jul 28, 2017 at 09:08 pm, Michael Davis wrote:
The diodes are not in any build Bitx as far as I know They need to be added. Also a fuse and the 100pf cap. It does make it confusing for new members to catch up with all that has gone on since late 2016. It might make sense to list all the most important hacks that make this radio more reliable and more versatile. As an SSB guy, the cw hacks don't interest me. With that said, what is important to some may not be interesting or necessary to others. So maybe 2 lists. The SSB list and the CW list, with links...published occasionally for new owners. Not sure how this can be accomplished.
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Re: Front End Protection Diodes?
Brian, I'm just using the 5 mhz in its original format. I'm not familiar with the article by?Tom Hurst's I'll look it up but real quick I'm just seeing the harmonics at 14, 21, 28 the rest of the spurious signals are way down in the -100dbm range and not a concern. All said by adding the capacitance to L7 it's a clean signal.? Hope this helps and I'll have to find the file you are mentioning. ?73's Dale
On Fri, Jul 28, 2017 at 9:08 PM, Michael Davis <maddmd818@...> wrote: The diodes are not in any build Bitx as far as I know They need to be added. Also a fuse and the 100pf cap. It does make it confusing for new members to catch up with all that has gone on since late 2016. It might make sense to list all the most important hacks that make this radio more reliable and more versatile. As an SSB guy, the cw hacks don't interest me. With that said, what is important to some may not be interesting or necessary to others. So maybe 2 lists. The SSB list and the CW list, with links...published occasionally for new owners. Not sure how this can be accomplished.
Sent from Mike's iPad WA1MAD
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Re: Front End Protection Diodes?
The diodes are not in any build Bitx as far as I know They need to be added. Also a fuse and the 100pf cap. It does make it confusing for new members to catch up with all that has gone on since late 2016. It might make sense to list all the most important hacks that make this radio more reliable and more versatile. As an SSB guy, the cw hacks don't interest me. With that said, what is important to some may not be interesting or necessary to others. So maybe 2 lists. The SSB list and the CW list, with links...published occasionally for new owners. Not sure how this can be accomplished.
Sent from Mike's iPad WA1MAD
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Re: Adding switchable USB and LSB to the Bitx40
That's L8 near the Final. ?The pdf of the schematic is kind of chunky, but if I zoom it up enough it's mostly readable.
L5 is in front of Q10, the crystal oscillator for the BFO.
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On Fri, Jul 28, 2017 at 07:21 pm, Dexter N Muir wrote:
Which L5 are you talking about, Mark? As I read the diagram, L5 is always fitted, in series with the PA PWR line (to the Final Q15),
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Ah yes the cap. Online costs have put me off the project for nearly a year. I just got the gumption to try and make my own butterfly capacitor, and it turned out pretty good for a first run at it. Of Course I did it wrong by using zinc plated hardware because I couldn't find bulk brass nuts. But just as a butterfly cap is works fine with about 25pf, and with the stators jumpered and used like a variable air cap it's 120pf. At out Ham Holiday I saw a high voltage commercial one like mine, but same capacitance. Anyhow the fear and mystery is gone, and I could make a bigger better one next time. Using a antenna calculator helps guess at the needed capacitance for what I will need next time. That one was just a (can I do it) kind of thing. ?I am gonna check out that mag loop group and see if they got anything I can learn. ?Laters.
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Re: Adding switchable USB and LSB to the Bitx40
Which L5 are you talking about, Mark? As I read the diagram, L5 is always fitted, in series with the PA PWR line (to the Final Q15), allowing the DC power through but impeding the final's RF from feeding back along the power supply. That would have no bearing whatsoever on which sideband is being generated/transmitted. Leave it alone - it has (more than) enough inductance to do the job, and low enough resistance (enough current-carrying capacity).
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Re: Adding switchable USB and LSB to the Bitx40
The high side VFO at 19mhz has advantages.
I suspect Allard uses it for USB because it requires minimum hardware mods to give switchable LSB/USB in software.
Another advantage is that there are fewer birdies and images, as they are now mostly up in the low VHF.
The disadvantage is that you have the duller edge of the crystal filter facing the bfo, so less carrier and opposite sideband rejection.
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On Fri, Jul 28, 2017 at 07:05 pm, Jerry Gaffke wrote:
Alternately you can leave the VFO at 5mhz (that way the sharper edge of the crystal filter is nearest the bfo)
and somehow move the bfo down in freq by about 3khz.
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Re: Adding switchable USB and LSB to the Bitx40
Depends on how you do it.
Allard's code simply moves the VFO from 5mhz to 19mhz, which flips between usb and lsb.
No hardware mods required, other than to remove C91,C92 to keep them from sucking away too much of the 19mhz VFO.
C91 and C92 are only needed if you are using the old analog VFO, not for the Raduino.
Alternately you can leave the VFO at 5mhz (that way the sharper edge of the crystal filter is nearest the bfo)
and somehow move the bfo down in freq by about 3khz.
You could drive the bfo from CLK0 of the si5351 on the Raduino as per the ubits, not switch required
to go between usb and lsb. ?Requires a change to the raduino code and coax from Raduino to bfo.
Or you could whack at the analog bfo with coils and caps to move it around.
Your choice.
Jerry, KE7ER
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On Fri, Jul 28, 2017 at 06:28 pm, Mr Sheesh wrote:
If you want switchable USB/LSB I had thought you'd want to jumper across L5 (which comes jumpered in the v3) or instead have a few uH in there, but how many uH isn't clear yet.
?
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Dennis Kidder (W6DQ) and I did start the Software Controlled Ham Radio group as a collection point for anyone who wants to blend our hobby with any software element. Obviously, I get a kick out of it and am learning some EE stuff along the way not easy for someone who's two years younger than dirt. Still it's been a blast.
As to the mag loop, I am a member of that group as well (https://groups.yahoo.com/neo/groups/MagLoop/info) and it has a lot of good information. I bought a vacuum variable capacitor with a 25KV rating as I also wanted to be able to use it with my 100W rig. The thing is about the size of a Volkswagen, so I'm backing off to an air variable cap, but with pretty healthy spacing. I'll experiment to see what kind of power I can use with it, but it should go to about 100W. I've lost two antennas this year to storms, so I'm hoping I can secure this one a little better. Should be fun...
Jack, W8TEE
From: John Smith via Groups.Io <johnlinux77@...>
To: [email protected]
Sent: Friday, July 28, 2017 6:50 PM
Subject: Re: [BITX20] Hey Jack!
Thanks for responding Jack. I thought you had a different group or site this stuff was coming from and shared here. I went back through my bookmarks and found the "Software controlled ham radio" Yahoo group. I haven't checked it in several months because the posts sound like a guys club with practically no focused content. Now it seems to have picked up a bit and saw your post about the Bitx 40 and a mag loop build. I almost talked myself out of it because of the cost of copper for a 40 meter band magnetic loop, which is between 17' and 34' in circumference. The plan was to have the mag loop for receive because of it's narrow bandwidth and noise rejection. And transmit with the low dipole that seems to be getting out better than originally expected. I just fell off topic too. Like I said, I thought this stuff was originally somewhere else. I also had plans to do something similar as the Forty-9er with another kit, but this BITX40 thing with the Raduino came along. Now I am feeling itchy for another project to play with. I'll go through the files section and your other group to collect everything in one spot. Thanks Jack.
I am including a link for a mag loop PDF because it seems like the definitive authority on the subject without talking over our heads. But still getting it all in there to explain it in detail. It might help someone curious about the magic antenna.
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Re: Adding switchable USB and LSB to the Bitx40
If you want switchable USB/LSB I had thought you'd want to jumper across L5 (which comes jumpered in the v3) or instead have a few uH in there, but how many uH isn't clear yet.
? Mark
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You might try taking the "+12V" of Gian's diagram from pin 8 of the LM386, which is only at 12v when the LM386 is powered up for receive.
I don't really know what all "+12V" into pin 7 might do, it certainly is not something written up in the datasheet.
But not much point in doing that when the LM386 is not otherwise powered up, which is the case during transmit.
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On Fri, Jul 28, 2017 at 12:29 pm, Jerry Gaffke wrote:
I assume this is the circuit you are referring to: ?/g/BITX20/message/21876
Dumping 12v into the bypass pin of the LM386 to quiet it down is a bit unorthodox, but apparently works.
The LM386 does not have much of anything to do with transmit, hard to imagine why you are getting this result.
I suspect something else is going on.
Jerry
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Thanks for responding Jack. I thought you had a different group or site this stuff was coming from and shared here. I went back through my bookmarks and found the "Software controlled ham radio" Yahoo group. I haven't checked it in several months because the posts sound like a guys club with practically no focused content. Now it seems to have picked up a bit and saw your post about the Bitx 40 and a mag loop build. I almost talked myself out of it because of the cost of copper for a 40 meter band magnetic loop, which is between 17' and 34' in circumference. The plan was to have the mag loop for receive because of it's narrow bandwidth and noise rejection. And transmit with the low dipole that seems to be getting out better than originally expected. I just fell off topic too. Like I said, I thought this stuff was originally somewhere else. I also had plans to do something similar as the Forty-9er with another kit, but this BITX40 thing with the Raduino came along. Now I am feeling itchy for another project to play with. I'll go through the files section and your other group to collect everything in one spot. Thanks Jack.
I am including a link for a mag loop PDF because it seems like the definitive authority on the subject without talking over our heads. But still getting it all in there to explain it in detail. It might help someone curious about the magic antenna.
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Re: Very fast post from India
Still building my bitx60/80 waiting for parts mainly 10k pots bpf and lpf for 80m all done I can not wait to go portable with the radios?
On 18 Jul 2017 11:12, "chris gress" < Chrisg0wfh@...> wrote: I got my 2x bitx 40 in 4 days much faster than DHL and no duty I have checked my 2 kits no damage to the main boards thanks :-)?
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Re: Front End Protection Diodes?
Dale, are you using a 5MHz vfo? or have you changed to 19MHz and generate USB at 12MHz.
I note you have been using a spectrum analyser. Do you see any close in spurious outputs like in Tom Hurst's "BitX40 Spectrum Output" on page 2 of the files section?
For me, the 19Mhz is not a solution because the xtal filter is so bad on that side.
73 Brian.
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Hi John:
I guess that most of the discussion is around what I'm doing to the BITX40, which I call my B40. I'm selling a PCB for those mods which, when done, includes:
? ? B40 mods: TFT color display, rotary encoder tuning, CW mode, speech processor, AGC, contest keyer, S meter, and supply voltage monitor. You can see the custom PCB?
? ? ? ? ? ? ? ? ? ? ? ? in the Files section of the users group. Search "W8TEE" and then sort by most recent date and look for Rel03 of the assembly manual. I'm redoing the software? ????????????????????????'cus I'm not happy with the way it works right now. I hope to have a release soon that handles frequency tuning with Fast Tune, and the ability to change fields? ????????????????????????smoothly on the display. You can see the display in the Photos section under my call. I sell the board for $7.50 (domestic).
? ? Antenna Analyzer: The PCB is sold by qrpguys.com. With a bare junk box, it costs about $50 to build, but has some nice features. They also have the assembly manual that
? ? ? ? ? ? ? ? ? ? ? ? you can download to see what it does. This was supposed to be in the Sept., 2017, issue of QST, but I just got a notice about 10 days ago that it has been "bumped"?
? ? ? ? ? ? ? ? ? ? ? ? to a later issue. No mention of when that will be.
? ? Forty-9er: This was published in the March, 2016, issue of QST and is a $10 40M 3W CW transceiver to which we added an LCD display and VFO. The original xcvr was by ? ? ? ? ? ? ? ? ? ? ?????????????Wayne Burdick and Doug Hendricks and built as part of the NorCal QRP group back in the '90's. My goal was to make a frequency-agile xcvr that could be built for? ? ? ? ? ? ? ? ? ? ? ? ?under $50. The rig is pictured below:
 ? ? ? ? ? ? ? ? ? ? ? ? This also used a custom PCB, which Farrukh Zia sells (www.farrukhzia.com/k2zia) for about $6.50.
Finally, some members here have mentioned two of my books: Beginning C for Arduino and Arduino Projects for Amateur Radio. The programming book is written for the true beginning programmer and assumes no prior programming experience. The second has a number of ham radio related projects using microcontrollers. You don't have to know programming to make the projects work and full source code is available for all projects at:?
????????https://www.mhprofessional.com/9780071834056-usa-arduino-projects-for-amateur-radio-group
Both books are available (and reviewed) on Amazon.com. You can click on the "Look Inside" banner on the book cover and read the Table of Contents and even some of the narrative.
I think that covers it.
Jack, W8TEE
From: John Smith via Groups.Io <johnlinux77@...>
To: [email protected]
Sent: Friday, July 28, 2017 2:23 PM
Subject: [BITX20] Hey Jack!
I have been coming to this site everyday and reading what's new, and little by little I see your other stuff creeping in. And was wondering if would post a link to your "other stuff" so I can get the full rundown on your for BITX40 DDS VFO, and the antenna analyzer, and so on. I am only getting pieces of it here, and would like to know more about it. I also wondered if you might be planning a book or something free with "Other stuff for the BITX'er". I can't just buy, I have to brew. And it's nice to find a funnel for all the information.
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I assume this is the circuit you are referring to: ? /g/BITX20/message/21876Dumping 12v into the bypass pin of the LM386 to quiet it down is a bit unorthodox, but apparently works. The LM386 does not have much of anything to do with transmit, hard to imagine why you are getting this result. I suspect something else is going on. Jerry
On Fri, Jul 28, 2017 at 12:20 pm, KC8WBK wrote:
Unfortunately I have to withdraw my recommendation for this circuit, it is doing something odd to the transmit.
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Unfortunately I have to withdraw my recommendation for this circuit, it is doing something odd to the transmit.? I am still using it, and have built three of the circuits to find out if it is my construction that is the problem or if it the circuit.? I am coming to the conclusion that the circuit is adding noise or carrier of some kind to the transmit signal.? I don't have a confirmation on this yet.
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Re: Front End Protection Diodes?
The BITX40 vs3 is what I'm running and I purchased it about 2 or so months ago. I'm not sure what the older models require but I will say it really helped my rig to add the capacitor (100pf) to the L7 coil.? My second order harmonic (14Mhz) was only 12dbm lower than the primary frequency. To be in compliance with the FCC you should be 40dbm lower than the primary frequency or in this case 7Mhz band. To make matters worse the 3rd order component (21Mhz) was even more disturbing. Now with the addition of the capacitor across L7 I'm down -50dbm from the primary frequency including all spurious signals and well within FCC compliance. The person who started this thread had an attachment with full instructions showing where to place the diodes and the cap. Great hobby have fun! Dale Kg7ssb
On Fri, Jul 28, 2017 at 9:55 AM, David <dokrent@...> wrote: I am a bit confused. I just recently bought the kit and from this thread I can't tell if you are referring to current or older units, or both. Seeking clarity.
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