Looking for Completely Functional Dual-Band 20/(17/15/10/6) Meter QRP Rig with SSB/PSK
#bitx20help
There is a degree of Elmering here that I have been very impressed with since I joined the group. Some threads are way to esoteric or deep for me and others are spot on. The beauty is that I can pick and choose what to move to my mini wiki and what I choose to delete. Given the experimental nature of the Bitx, the Elmering is really appreciated. What a fantastic learning platform.
I hope the bandwidth doesn't get too narrow.
Tim
WB7UVH
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On 2018-02-25 21:39, Jerry Gaffke via Groups.Io wrote:
There are plenty of threads here I'd just as soon skip over, and often do.
Perhaps you can do the same.
I for one am fine with discussions of antennas (that seems very appropriate)?
and with discussing the pros and cons of the Bitx radios vs others.?
Jerry, KE7ER
On Sun, Feb 25, 2018 at 08:13 pm, Rod Self wrote:
I, for one, am very tired of off-topic general discussions about radios and antennas on the bitx20/ubitx group.
Please let this thread die, or move it to another discussion group.
A good guideline: if it does not involve a bitx or utibx, it probably does not belong here.
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Re: Looking for Completely Functional Dual-Band 20/(17/15/10/6) Meter QRP Rig with SSB/PSK
#bitx20help
Might want to check out MIG welding wire.? It is copper coated steel, so
both strong and conductive.?
_._
On Sun, Feb 25, 2018 at 5:37 PM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote: Anything that doesn't break in the weather is thick enough, within limits.
Drive 1000 Watts into 28 gauge copper, it may fall out of the sky into little molten puddles on the ground.
And kind of a bummer to have to go out and climb trees to fix broken antenna wire during an ice/wind/rain storm.
Galvanized steel is less conductive than copper,? I doubt you would notice the difference, except it's stronger.
Copper clad steel is available, seems a good idea, I've never used it:??
Hard drawn copper is stronger than standard copper wire, often used for antennas.
You may have a local HRO storefront:?
they have lots of different antenna products.
Disconnect your equipment if an electrical storm is in the area.
On Sun, Feb 25, 2018 at 03:59 pm, Mark wrote:
For QRP I'd only need #17?
There's a write-up on this type of wire purchased from tractor supply stores, entitled, Does wire gauge (size) make any difference for vertical antenna radials?, at eHam.net.
They say that some antenna manufactures suggest 14. I guess that is possibly because it is used for base stations with 100 or more watts.
However, for my specific QRP & mobile situation, maybe 17 would be fine. It would also be a bit lighter.
Would reception improve if it were copper? Or, maybe for something like this it wouldn't really matter.
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Re: RD16HHF1 power curve flattening...some
Thank you Bill.
I was intrigued by the low value of the capacitor value across T11. So that makes more sense.
I find interesting the size of the output transformer on the PennyWhistle compared to the BN43-202. It might explain the warm temperature of the T11 transformer at 18-15 Watts. I will try a BN43-3312 as it should still fit in the space between the finals.
I will definitely try your suggestions.
All the best,
73, John (VK2ETA)
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Well I guess the question to ask is what is your goal?? Do you want to maintain a constant audio level with varying signal strength, or do you want to maintain a constant RF/IF/Audio gain in your radio.? They are much different¡ have much different impact on the radio.? Limiting and compression can occur at any stage.? So far you have demonstrated an audio gain level control.? If you want t TRUR and traditional AGC, you need to start at the front end of the radio to prevent it from over-loading with strong signals. ? ? Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ ? Owner - Operator Big Signal Ranch ¨C K9ZC Staunton, Illinois ? Owner ¨C Operator Villa Grand Piton ¨C J68HZ Soufriere, St. Lucia W.I. Rent it: Like us on Facebook! ? Moderator ¨C North American QRO Yahoo Group. ? email:? bill@... ? ?
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From: [email protected] [mailto:[email protected]] On Behalf Of John
Sent: Sunday, February 25, 2018 11:10 PM
To: [email protected]
Subject: [BITX20] Three (and a Half) AGC schemes #ubitx-help ? I have tried three (and a bit) AGC schemes with the uBitx with the following results:
1. TPA2016 from Adafruit in replacement of the standard audio chain after the potentiometer. Thank you Nik (VK4PLN) for sharing the code.
Like mentioned in another thread recently I also had low volume. To get more signal in I changed R51 to 10K and R50 to 330K. It worked to a point but to get enough "AGC effect" I had to reduce the setgain( ) to close to zero.? This meant lower volume.
I tried multiple combination of parameters, but it felt more like a limiter than an AGC.
I take an FT-817 as a reference, although of course I don't expect to get to the same AGC performance, just to be able to listen to a net without adjusting the volume every time a new station comes on.
The final straw for the TPA2016 was when I discovered hash generated on the 40M band. This meant probably more shielding and filtering although I had it mounted on top of a double sided epoxy circuit board the same size as the uBitx main board and connected to ground in the four corners.
So I moved on the next solution.
2. I tried the 2n7000 AGC circuit as shown in the pre-production uBitx schematic.
I noticed that the gain control would come only on loud signals as there is a significant threshold in the circuit before the MOSFET reaches it conductive state.
I therefore replaced the half wave rectification with a voltage doubler version and changed the 1N4148a to BAT46 (Schotky) but still not enough sensitivity to the trigger the AGC on medium signals.
Since I needed low power to drive the MOSFET I used an 8 Ohms to 500 Ohms 350mW audio transformer with the low impedance side connected to the 2nd output of the TDA2822. This gives plenty of voltage even on low signals to control the MOSFET. The AGC action was good but I had distortion, especially on low signals.?
I tried to decouple the drain of the MOSFET to the Vol-H input but to no avail.
I read on the internet about "adding half of the signal voltage to the gate of the FET to reduce distortion" for these type of AGC schemes, but I am not sure it applies to depletion of enhancement FETs.
So any experience using this "pre-production" AGC circuit in the uBitx would be greatly appreciated.
3. I also tried and I currently have a MAX9814 from Adafruit in place for AGC, connected strait between VOL-H and the top of the volume potentiometer with decoupling capacitors in and out, through an input and output trimmer pot for adjustment.
I also added a 390nF capacitor in parallel to the 100nF at the time constant terminal (TC) to slow the reaction down to about 1ms.
That solution too is not proving that great. The variable gain range seems too small (although the specs says 60dB dynamic range) as it quickly gets overwhelmed by large signals and introduces strong distortion, or, if adjusted lower, only comes into play on very? strong signals.
It is a shame as the TC connection of the MAX9814 give a DC voltage related to the AGC action and could have been used for an S meter input.?
So my questions are:
A. Is the pre-production 2N7000 solution (circuit attached below) producing distortion in your uBitx (where implemented) and if not did you modify the circuit in any way?
B. Any other good proven AGC scheme tested with uBitx?
C. Am I asking too much of an audio AGC circuit?
Thanks for reading.
All the best,
73, John (VK2ETA)
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uBITX I want to know when ?
Hello My name is Hwang-Chan? Bae.
We have paid $ 109 to Paypal as a credit card to DEC-21-2019 to purchase uBITX.
But uBITX has not arrived yet.
I want to know when it is coming.
Receipt Number: 5494-5763-6907-3144.
name: Hwang-chan? Bae
Address: Banyan Road 177 (205-1104) Hyundai Apartment
Changwon City Seongsan-gu, Gyeongsangnam-do
51425
Republic of Korea.
Please let me know when you arrive.
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I have tried three (and a bit) AGC schemes with the uBitx with the following results:
1. TPA2016 from Adafruit in replacement of the standard audio chain after the potentiometer. Thank you Nik (VK4PLN) for sharing the code.
Like mentioned in another thread recently I also had low volume. To get more signal in I changed R51 to 10K and R50 to 330K. It worked to a point but to get enough "AGC effect" I had to reduce the setgain( ) to close to zero.? This meant lower volume.
I tried multiple combination of parameters, but it felt more like a limiter than an AGC.
I take an FT-817 as a reference, although of course I don't expect to get to the same AGC performance, just to be able to listen to a net without adjusting the volume every time a new station comes on.
The final straw for the TPA2016 was when I discovered hash generated on the 40M band. This meant probably more shielding and filtering although I had it mounted on top of a double sided epoxy circuit board the same size as the uBitx main board and connected to ground in the four corners.
So I moved on the next solution.
2. I tried the 2n7000 AGC circuit as shown in the pre-production uBitx schematic.
I noticed that the gain control would come only on loud signals as there is a significant threshold in the circuit before the MOSFET reaches it conductive state.
I therefore replaced the half wave rectification with a voltage doubler version and changed the 1N4148a to BAT46 (Schotky) but still not enough sensitivity to the trigger the AGC on medium signals.
Since I needed low power to drive the MOSFET I used an 8 Ohms to 500 Ohms 350mW audio transformer with the low impedance side connected to the 2nd output of the TDA2822. This gives plenty of voltage even on low signals to control the MOSFET. The AGC action was good but I had distortion, especially on low signals.?
I tried to decouple the drain of the MOSFET to the Vol-H input but to no avail.
I read on the internet about "adding half of the signal voltage to the gate of the FET to reduce distortion" for these type of AGC schemes, but I am not sure it applies to depletion of enhancement FETs.
So any experience using this "pre-production" AGC circuit in the uBitx would be greatly appreciated.
3. I also tried and I currently have a MAX9814 from Adafruit in place for AGC, connected strait between VOL-H and the top of the volume potentiometer with decoupling capacitors in and out, through an input and output trimmer pot for adjustment.
I also added a 390nF capacitor in parallel to the 100nF at the time constant terminal (TC) to slow the reaction down to about 1ms.
That solution too is not proving that great. The variable gain range seems too small (although the specs says 60dB dynamic range) as it quickly gets overwhelmed by large signals and introduces strong distortion, or, if adjusted lower, only comes into play on very? strong signals.
It is a shame as the TC connection of the MAX9814 give a DC voltage related to the AGC action and could have been used for an S meter input.?
So my questions are:
A. Is the pre-production 2N7000 solution (circuit attached below) producing distortion in your uBitx (where implemented) and if not did you modify the circuit in any way?
B. Any other good proven AGC scheme tested with uBitx?
C. Am I asking too much of an audio AGC circuit?
Thanks for reading.
All the best,
73, John (VK2ETA)
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Re: Erratic tuning with my new uBitx
One way to visualize how an encoder works is to think of 20 speed bumps arranged in a circle. Floating above the speed bumps is a wire. Now imagine a contact arm anchored in the center of the circle and a second contact arm 90 degrees out of phase with the first arm. As a shaft turns, the contact hits a speed bump and make contact with the wire above it. Therefore, every 18 degrees (360 / 20 = 18) a contact is made and a pulse chain is form by the two contact arms. By looking at those signals, you can determine if the shaft is rotating CCW or CW. Therefore, you will see a pulse chain of binary values coming from the encoder. A better description can be seen on YouTube:
Jack, W8TEE
From: Jerry Gaffke via Groups.Io <jgaffke@...>
To: [email protected]
Sent: Sunday, February 25, 2018 11:29 PM
Subject: Re: [BITX20] Erratic tuning with my new uBitx
As you rotate the encoder shaft, the enocder alternately grounds ENC_A and then ENC_B. The timing in how it shorts one and then the other tells the Raduino which direction you are turning the shaft. So this grounding is not an error. You should see a regular pattern of 5v and 0v on those pins as you turn the shaft, and the two patterns should look very similar (just slightly shifted in time) On Sun, Feb 25, 2018 at 07:34 pm, DrZ wrote:
It does seem weird that I would have this problem even with the original sketch. ?I'll try the test you suggest. ?Are you saying that the occasional short to ground is an error?
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Re: Looking for Completely Functional Dual-Band 20/(17/15/10/6) Meter QRP Rig with SSB/PSK
#bitx20help
There are plenty of threads here I'd just as soon skip over, and often do.
Perhaps you can do the same.
I for one am fine with discussions of antennas (that seems very appropriate)?
and with discussing the pros and cons of the Bitx radios vs others.?
Jerry, KE7ER
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Show quoted text
On Sun, Feb 25, 2018 at 08:13 pm, Rod Self wrote:
I, for one, am very tired of off-topic general discussions about radios and antennas on the bitx20/ubitx group.
Please let this thread die, or move it to another discussion group.
A good guideline: if it does not involve a bitx or utibx, it probably does not belong here.
|
Re: Looking for Completely Functional Dual-Band 20/(17/15/10/6) Meter QRP Rig with SSB/PSK
#bitx20help
Yes Mark, just bent -- actually looped back upon itself. Say you need
to shorten each leg by 6 inches. Bend the wire back on itself at the
6-inch mark; you can then twist that 6 inches around the antenna wire
it is bent back onto, but you can just as well simply clip the extra
wire onto the antenna using a wire clip. Either way, the antenna
"ignores" the 6 inches that is bent back onto the antenna leg. - Rich
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On 2/25/18, Mark via Groups.Io <mboston72@...> wrote: Hi Rich,
Thanks for the suggestion. Yes, I've heard that before. They don't
necessarily need to be clipped. They can just be bent? More information for
my antenna book. Great!
Mark
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Re: Erratic tuning with my new uBitx
As you rotate the encoder shaft, the enocder alternately grounds ENC_A and then ENC_B.
The timing in how it shorts one and then the other tells the Raduino which direction you are turning the shaft.
So this grounding is not an error.
You should see a regular pattern of 5v and 0v on those pins as you turn the shaft, and the two patterns should look very similar (just slightly shifted in time)
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On Sun, Feb 25, 2018 at 07:34 pm, DrZ wrote:
It does seem weird that I would have this problem even with the original sketch. ?I'll try the test you suggest. ?Are you saying that the occasional short to ground is an error?
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Re: RD16HHF1 power curve flattening...some
Here¡¯s what I found... if you change R85 from 100 to 470 ohms (pre-driver stage bias), change R261 and R262 from 100 to 1K ohm (Although 820 ohms will work too¡ it¡¯s not that critical), run RV1 wide open (full drive) and then use a compensating capacitor (your 33pf at 14 MHz) across T11 primary with a 1:4 transformer: ? 6M - 48pf 10M - 110pf 20M - 320pf 40M - 680pf 80M - 1,500pf 60M - 4,700pf ? It shows at least 20 watts out on each band except for 6 meters... where it peaks at 12 watts.? My calculations show that the 3:2 is not optimal for this pair. You might want to have a look at:? ? ? ? ? Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ ? Owner - Operator Big Signal Ranch ¨C K9ZC Staunton, Illinois ? Owner ¨C Operator Villa Grand Piton ¨C J68HZ Soufriere, St. Lucia W.I. Rent it: Like us on Facebook! ? Moderator ¨C North American QRO Yahoo Group. ? email:? bill@... ? ?
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From: [email protected] [mailto:[email protected]] On Behalf Of John
Sent: Sunday, February 25, 2018 7:59 PM
To: [email protected]
Subject: [BITX20] RD16HHF1 power curve flattening...some ? Having read with interest the information provided by Erhard Haertel (DF3FY) on ubitx.net regarding the changes to the finals circuit I decided to try to improve the flatness or lack thereof of the power curve over frequency on my uBitx unit. I therefore performed his proposed changes (final's transformer, cap across drains, feedback resistors) with one exception: the feedback resistors between drain and source of the final was changed from 220 Ohms to 820 Ohms instead of 1K Ohms. I got the following result at 13.8V, with idle current at 250mA per final, RV1 unchanged at approx 60% as before: Freq.? ? ? Power? ? ?Total Current ?7Mhz? ? ? ? 18W? ? ? ? ?2.8A 14Mhz? ? ? ? 16W? ? ? ? ?2.7A 21Mhz? ? ? ? ?9W? ? ? ? ?1.5A 24Mhz? ? ? ? 11W? ? ? ? ?1.9A 28Mhz? ? ? ? 11W? ? ? ? ?2.2A Hmmmm...not bad but still that dip at 21 and not that high on the high frequencies. But the good news was that I would get power improvement all the way to the end of the RV1 pot and it looked like no compression was occurring. Good news as this means that I have spare power for frequency compensation. Using the LTSpice simulation done by Jerry Gaffke (thanks Jerry) with a replacement of the finals with the RD16HHF1 model found on the internet and I got some interesting pointers (reality is always different, but I find this is a good starting point). I simulated capacitors in parallel with the 22 Ohms emitter resistors in the pre-driver and driver stages alternatively. Since I had "free gain" left by turning RV1 this meant that none of the stages were limiting at 60%, therefore I could increase the gain anywhere in the chain, including at RV1 for that matter.
LTSpice gave me a flat curve with caps of 150-200pf in the pre-driver stages, and more importantly a rapid drop in power above 40Mhz which I hope may prevent V-UHF oscillations of the power train (linear amplifier specialists can comment on that point).
So I experimented with various caps values across the R87 and R88 resistors and found that I would not get more gain above 330pf. Results as per above conditions (RV1 back at 60%): Freq.? ? ? Power? ? ?Total Current ?7Mhz? ? ? ? 18W? ? ? ? ?2.8A 14Mhz? ? ? ? 16W? ? ? ? ?3.0A 21Mhz? ? ? ? 10W? ? ? ? ?1.6A 24Mhz? ? ? ? 11W? ? ? ? ?not recorded 28Mhz? ? ? ? 14W? ? ? ? ?1.9A Not perfect but at least now 10W on the high bands, and above 15W at and below 14 megs. One minute key down then "finger heat test": the finals new transformer is a little warm but not much. The filters the same. The finals and the heat-sink (thermally coupled to the metal case) are fine. So the question is: can the filters handle that kind of power over time? Short of doing and LTSpice simulation is there an easier way to calculate the current and therefore the flux density in the filters cores to check if we are getting to saturation or not?? No instability and oscillation detected with a separate radio, but again I don't have a spectrum analyser.? So in summary this is what I have in the circuit now: Finals as RD16HHF1s, feedback resistors R261/R262 as 820 Ohms, Tranformer 2T primary / 3T secondary on BN43-202, 33pF across the output transformer primary and 330pf across R87/R88. I haven't tried capacitors across the driver stage emitter resistors (R941/942/911/96), nor from the high to the middle side of RV1 for the following reasons: I wanted to leave the drivers alone and not modify the way they drive the finals (impedance change), and at RV1 it meant that the capacitor value would need to change with the adjustment of RV1, although this could be the simplest way to correct the power curve.? Interestingly enough for the units with the IRF510s, LTSpice reports a flat power curve with 800pf caps across these four drivers resistors....it could be just theory...and stability could be an issue as we reduce negative feedback. Is anyone game enough?
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Re: Looking for Completely Functional Dual-Band 20/(17/15/10/6) Meter QRP Rig with SSB/PSK
#bitx20help
Rod,
This thread started as a ¡°is this a good radio for me¡± thread regarding the ?bits or BiTX40. It has wandered a bit, but I would still rather follow this thread than another ¡°Mine shipped¡± ¡°I got mine¡± ¡°I haven¡¯t got mine¡±
Thomas Noel
KF7RSF
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Re: Raduino Replacemnt, COMING SOON!
Another update on Rev.01 board, I have added components to fit a optional voltage divider connected to A06 for measuring input voltage. Obvously once you have moved the origional function over to a free digital port after doing I2C display..
73 Nick, VK4PLN
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Re: Looking for Completely Functional Dual-Band 20/(17/15/10/6) Meter QRP Rig with SSB/PSK
#bitx20help
I, for one, am very tired of off-topic general
discussions about radios and antennas on the bitx20/ubitx group.
Please let this thread die, or move it to another discussion group.
A good guideline: if it does not involve a bitx or utibx, it
probably does not belong here.
Rod KM6SN
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Re: #ubitx and 6 meters
#ubitx
how high will the mixer function? could it be used to gain access to 2 Meters??
Justin N2TOH?
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I need to calibrate the Raduino.? I've reviewed the instructions and it seems fairly simple.?? My only question is where do most people attach the red wire to ground.?? It appears that one of?the 4 mounting holes on the Raduino board may be the most convenient as I did a continuity check and I found that they seem to have continuity with each other and the negative side of the DC connector.??
Thanks,??? Jim??? W6yxy
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Re: Erratic tuning with my new uBitx
It does seem weird that I would have this problem even with the original sketch. ?I'll try the test you suggest. ?Are you saying that the occasional short to ground is an error?
Thanks
Howard K4LXY
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Re: Erratic tuning with my new uBitx
Thanks, Nik. ?I plan to do that, though it seems weird that I would have this problem with the original firmware if the encoder is OK.
73
Howard K4LXY
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Re: Looking for Completely Functional Dual-Band 20/(17/15/10/6) Meter QRP Rig with SSB/PSK
#bitx20help
Antennas have always befuddled me. What does work for me is the presence of a decent tuner. Without a tuner, it is pretty much of shoot-and-pray.?
An antenna tuner is just a variable capacitor from an old broadcast radio and a coil with taps on it. You need an SWR indicator. Tayloe's LED indicator is better than nothing. Once you have that with you, then you can tune up just about anything. Keep moving the wires around until you hit a sweet spot.?
About the feedline, the less said, the better. Literally, keep it as short as you can.
- f??
On Mon, Feb 26, 2018 at 7:11 AM, Patrick G <KC9RGE@...> wrote: Wow that's pretty impressive! Got some research to do!
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I have described how to reduce or eliminate PTT carrier burst in BITX40. Please search!
Raj
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At 26/02/2018, you wrote: Hi Dale, I disconnected D20 from the input of the attenuation pad going into the tx amp and the carrier was reduced but still there. I was wondering if the 12 MHz oscillator output could be leaking into the tx amp. I also get a large burst of of RF when the ptt is pressed. I read in earlier posts that they never found a solution to the ptt RF burst problem. I also read that with the diodes and the pot that it was normal to get a 1vpp output at the antenna with no audio input. Would you mind you mind discussing this problem on the land line. Thank You Bob WB2TFG ex
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K9HZ
Nick VK4PP
Raj vu2zap