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Re: Amplifier chain design - best practices
Jim,
Replacing RV1 with a 10K is not good as it would put all the adjustment in the last 5 degrees of rotation. A 500 ohm may be better. But you begging 1 db of gain increase for what reason?? ?Replace the 3904 in that stage prior and the performance jumps a greater degree and fixes the actual problem there. Allison |
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Re: Amplifier chain design - best practices
On Fri, Sep 21, 2018 at 09:19 AM, Jeff Omundson wrote:
1)Keep amplifier intos and outofs away from each other. This also applies to all RF systems.?? 2)Keep amplifier gain stages reasonable.? Add more stages instead of upping gain. This is a serious and common error, forcing or wishing for gain that is not predictably there. Conservative design rules insure that. 3)Pick the right device for the desired frequencies.? Obviously 2n3904's don't work for this application.? First the 2n3904 can if one does not apply wishful thinking and employs it within the devices capability. ***Does picking a part with an fT about 40 times the highest desired frequency a safe bet?? Oddly the answer is yes if the stages has to deliver at least part of the gain desired.? For a? 30mhz amp with a 20db stage gain you will need an Ft of something approaching 3000mhz! The real question is does it makes sense when two 3904s at 10DB each can also do that? at 30mhz.?? ***Can you pick an FT that is too high (like a npn transistor with and fT of 10 gHz for a 3-30mHz radio)??? The answer is yes and maybe.? IF you using resistive feedback amps (nearly the entire transmitter and both IFs) the required FT is a product of the gain and the frequency so at some point you really have to ask is that much gain per stage reasonable and stable.? IT might be prudent to back down the gain and use a more reasonable transistor.? Also for higher power stages the cost for a supergain high power device might break the bank. A lot of QRP designs more so older one try to be minimal and get the most out of a very few parts. If you making one this is ok as you can dial it in and hand pick parts.? For quantity builds this is terrible. You want every one to be the same as the last.? So care in not trying to get 101% of capability is advised.. This shows more often in transmitter circuits as out of a group most doe the expected watts, a few do more and a bunch never do that.? Multiband transmitters due to bandwidth, power and layout require greater attention. 4)Keep RF wires/traces away from each other and from the dc path. Again this works for RX and TX circuits.? We do not want o induce unwanted signals into the receiver. From Crystal Sets to Sideband, a very good starting place.? My Favorite are Solid State Design For Radio Amateurs, and Experimental Methods in RF Design (Both ARRL).? Neither are light bits and do require several reading through passes to pick up that what was mentioned here is often elaborated and related to things there. ***Makes me wonder how the ft817 does hf, vhf and uhf...? Lots of tuned filters, careful layout the use of the chassis as cooling, shielding, and mechanical support. Its worth looking at Elecraft K1 and K2 as the manuals and detail in them is very good as examples. I'd add KNQ7A? and the KD1JV Sopbucket 20 as a simple monoband, and a few other as well.? Generally the designers are creative people so watch for solutions to problems not outwardly discussed as its often not featured but important.? Cooling and layout are often not obvious without analysis.? Same can be said for component choices. Allison |
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Re: Amplifier chain design - best practices
Jeff
great question on what's a good transmit path design.? since I have the K2 manual here -- predriver is a 2n5109, feeding a (;3 transformer on a FT37-43 driver is a 2SC2166 NPN feeding a 12:8 transfomer on a FT37-43 maybe some soft equalization network here ?? that's all I see that might seek to flatten RF performance the PA is push-pull pair of 2SC2166 into a transformer to achieve the desired output power to feed 50 ohms these devices fit the original K2 price target but not now the primary, global uBITX users. the FT817 uses different PA devices for VHF/UHF than HF I think.? I imagine the VHF/UHF PA module may cost more than a uBITX.? obviously the climb for HF to 50 MHz requires more savvy PA devices.? on the uBITX PA, when details are revealed on the IRF510 PA designed by Allison and Hans for the QSX there will be something of value here for v5, and to see if we can improve use of the v4 board.? 73 Curt |
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Re: Amplifier chain design - best practices
jim
Just as a suggestion, before you start ANY mods ...Consider replacing RV1 with a 10k or so pot .... All the preamp gain is getting eaten up by C82/100 ohm RV1 to ground .,,
Sometimes the simplest things are hardest to see Jim
On Friday, September 21, 2018, 9:19:44 AM PDT, Jeff Omundson <jeffomundson@...> wrote:
For me at least, this is more conceptual, but I am interested in understanding more after reading about the issues? with the uBitx power amp driver and predriver problems.? What are the best practices for designing this portion of a transmitter when it is to cover such a wide range of frequencies?? I imagine it also applies to a monoband radio. This is what comes to mind based on my limited knowlege and what I've gathered from reading stuff here. 1)Keep amplifier intos and outofs away from each other. 2)Keep amplier gain stages reasonable.? Add more stages instead of upping gain. 3)Pick the right device for the desired frequencies.? Obviously 2n3904's don't work for this application.? Does picking a part with an fT about 40 times the highest desired frequency a safe bet?? Can you pick an fT that is too high (like a npn transistor with and fT of 10 gHz for a 3-30mHz radio)?? I ask this last bit after looking through the digikey transistor offerings... I suppose any device needs to be tested and tweaked for its application. 4)Keep rf wires/traces away from each other and from the dc path.?? Makes me wonder how the ft817 does hf, vhf and uhf...? I suppose it could be a good exercise to look at how others have done it successfully, like elekraft with the k2.? It will be interesting to see how the QSX does it. Would making a transceiver optimized for one band and then making transverters for the other bands avoid some of these problems?? I'm thinking of what is outlined in the From Crystal Sets to Sideband book. -Jeff AG7NW |
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Re: JackAl System Preview
Jack Purdum
We haven't noticed those problems, but we're going through our board for that. Al and I are taking the JackAl to an off-the-grid site in TN for three days next week and I'll be able to give the CW elements a "real" test then. I think JackAl will like getting out of the basement... Jack, W8TEE
On Friday, September 21, 2018, 12:28:54 PM EDT, Mark Kesner <kc4gia@...> wrote:
I wonder if the JackAl will overcome the CW issues?? I have agc and 'thump' mods in place which help.? I still have issues with a delay on transmit, losing about half of the first letter sent and issues with getting the IF aligned properly. Granted, that last part is likely me.? Thanks Mark KC4GIA? |
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Re: JackAl System Preview
Those issues were solved a week after version 1 was released!? rOn On September 21, 2018 at 12:28 PM Mark Kesner <kc4gia@...> wrote: |
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Re: JackAl System Preview
I wonder if the JackAl will overcome the CW issues?? I have agc and 'thump' mods in place which help.? I still have issues with a delay on transmit, losing about half of the first letter sent and issues with getting the IF aligned properly. Granted, that last part is likely me.?
Thanks Mark KC4GIA? |
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Amplifier chain design - best practices
For me at least, this is more conceptual, but I am interested in understanding more after reading about the issues? with the uBitx power amp driver and predriver problems.? What are the best practices for designing this portion of a transmitter when it is to cover such a wide range of frequencies?? I imagine it also applies to a monoband radio.
This is what comes to mind based on my limited knowlege and what I've gathered from reading stuff here. 1)Keep amplifier intos and outofs away from each other. 2)Keep amplier gain stages reasonable.? Add more stages instead of upping gain. 3)Pick the right device for the desired frequencies.? Obviously 2n3904's don't work for this application.? Does picking a part with an fT about 40 times the highest desired frequency a safe bet?? Can you pick an fT that is too high (like a npn transistor with and fT of 10 gHz for a 3-30mHz radio)?? I ask this last bit after looking through the digikey transistor offerings... I suppose any device needs to be tested and tweaked for its application. 4)Keep rf wires/traces away from each other and from the dc path.?? Makes me wonder how the ft817 does hf, vhf and uhf...? I suppose it could be a good exercise to look at how others have done it successfully, like elekraft with the k2.? It will be interesting to see how the QSX does it. Would making a transceiver optimized for one band and then making transverters for the other bands avoid some of these problems?? I'm thinking of what is outlined in the From Crystal Sets to Sideband book. -Jeff AG7NW |
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Re: uBITX schema relay K1
#ubitx
Acknowledged, I'll have a look to the wiki then. Il 20/set/2018 20:45, "ajparent1/KB1GMX" <kb1gmx@...> ha scritto: Iz oos, |
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Re: Ubitx evolving fixes updated to wiki?
#ubitx
#ubitx-help
Thanks for putting this info on the wiki and for adding the descriptive pictures!? It is very clear!
-Jeff |
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Re: V3 uBitx Very Shrill Audio
BFO is off!
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Show quoted text
At 21/09/2018, you wrote: Thank Raj, I'll have to look at that tonight.? Here is a link to a short video on You Tube if someone whats to hear what it sounds like make further comment.? I went to frequencies on 80 & 40 where I knew there were strong signals at least form one station in a QSO.? This is what I hear. |
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Re: JackAl System Preview
Jack Purdum
My bad...did not know that. Truly sorry... Jack, W8TEE
On Friday, September 21, 2018, 10:31:23 AM EDT, Buddy Brannan <buddy@...> wrote:
Yeah, it¡¯s that extra 5% when you¡¯re blind though. ¡ > On Sep 21, 2018, at 9:22 AM, Jack Purdum via Groups.Io <jjpurdum=[email protected]> wrote: > > I felt exactly the same way when Al suggested using TS instead of a menu system. Now, I like it. Keep in mind you rarely actually "use" the TS system, with probably 95% of the time you're only using the Tuning and ALS encoders. Indeed, once you do the setup to set the "factory defaults" to your preferences (e.g., DSP filters, WPM, sidetone frequency and volume, equalizer, etc.), there's little need to use the TS system. Think about it. > > Jack, W8TEE > > On Friday, September 21, 2018, 9:51:05 AM EDT, Buddy Brannan <buddy@...> wrote: > > > Sounds great, except, and understanding I¡¯m in a minority of 1 here, the touch screen. I¡¯d love this tied to a menu if needed plus a 4X4 keypad or such. ¡ > > > On Sep 19, 2018, at 10:28 AM, Jack Purdum via Groups.Io <jjpurdum=[email protected]> wrote: > > > > If we went to a screen that small, I think we'd drop the touch screen feature and do complete menu system. The costs aren't cheap compared to those display sizes (e.g., > $10 versus $34), but 5" at 800x480 is nothing to throw rocks at and is easier on the eyes for us old people. Also, quite a few have adopted the Nextion display and they cost twice as much as ours and are about half the size. Also, we give you an experimenters platform with a dozen empty pins and idle resources to play with (see feature set below). Also, we have a pretty robust feature set: > > > > 5¡± or 7¡± TFT Touch Screen 800x480 TFT Color Display > > Dual VFO > > RIT > > S Meter > > Real Time Clock (add optional battery) > > 50 CW Preset Messages, selectable at runtime > > Touch Screen Band Selection > > Touch Screen Buttons for function selection and control > > Dual Encoders: Frequency Tuning, ALS Tuning, Program Input > > Frequency Tuning: > >? ? Standard > >? ? ALS Tuning--ALS Tuning: Special tuning using the second encoder. If the > >? ? ? ? ? ? frequency increment is set to 1KHz, ALS Tuning sets the second > >? ? ? ? ? ? encoder to one-tenth the increment of the primary tuning rate. This > >? ? ? ? ? ? allows for rapid tuning to an approximate frequency using the main > >? ? ? ? ? ? encoder and then using ALS Tuning with the second encoder to fine > >? ? ? ? ? ? tune the signal. Once you use it, you'll wonder how you lived without it. > > Filter Selection: > >? ? CW presets (3dB bandwidth): 150 Hz, 300 Hz, 400 Hz, 600 Hz > >? ? SSB presets (3dB bandwidth): 1500 Hz, 1800 Hz , 2200 Hz, 3000 Hz > > EEprom storage of user preferences and CW code presets > > 3 external hardware buttons for CW code messages (e.g., contest exchanges) > > Based on Teensy 3.6 Microcontroller with Audio Shield > > Hardware AGC using IF take-off > > Mic Compressor with adjustable threshold > > Mic 8-band equalization > > Receive Audio Filter > > 48 dB/octave (8 pole equivalent DSP filters) > > 2 Variable bandwidth filters ¨C user-defined knee frequencies with Rotary Encoder control > > Audio AGC with adjustable threshold > > Variable Notch filter, encoder adjustable, use specified Q > > CW code to Text converter > > Code Practice Oscillator Mode > > About a dozen I/O pins to play with plus 800K of free flash memory, 200K of free SRAM, > >? ? ? all clocked at 180MHz > > > > > > Finally, this is Rel. 1.0 of the software. We think we can do some pretty clever stuff with Rel. 2.0. You can see these board in the video here: > > JackAl uBITX Add-on > > > >? ? > > JackAl uBITX Add-on > > This is a preview of the up-coming uBITX add-on board. Centered around a high-resolution touch screen TFT displa... > > > > We also think the system is flexible enough to adapt to other inexpensive rigs. Al and I plan to experiment with this after JackAl is released. > > > > Jack, W8TEE > > > > > > > > > > On Wednesday, September 19, 2018, 1:18:36 AM EDT, Ashhar Farhan <farhanbox@...> wrote: > > > > > > can this be adapted to small tft displays? the cost of going from a 2.4 inch to this display is quite high. > > > > - f > > > > On Wed, Sep 19, 2018 at 5:34 AM, Jack Purdum via Groups.Io <jjpurdum=[email protected]> wrote: > > If you can run the Arduino IDE, I don't see why not. The software is all on the board. If you can't run the IDE, go to a school lab, borrow a Windows machine, ciompile/upload, take home and plug in...done! > > > > Jack, W8TEE > > > > On Tuesday, September 18, 2018, 3:58:45 PM EDT, Mike Lichtman via Groups.Io <tchrme=[email protected]> wrote: > > > > > > Jack and Al, > >? ? I concur. I also would prefer a ¡°all in one place¡± maxi purchase. Many of us have Macs and cannot use Ian¡¯s utility program. Will we also be able to utilize the Jackal? 73 Mike KF6KXG > > > > > > > > > > > > > > |
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Re: JackAl System Preview
Yeah, it¡¯s that extra 5% when you¡¯re blind though. ¡
toggle quoted message
Show quoted text
On Sep 21, 2018, at 9:22 AM, Jack Purdum via Groups.Io <jjpurdum@...> wrote: |
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Re: JackAl System Preview
Jack Purdum
I felt exactly the same way when Al suggested using TS instead of a menu system. Now, I like it. Keep in mind you rarely actually "use" the TS system, with probably 95% of the time you're only using the Tuning and ALS encoders. Indeed, once you do the setup to set the "factory defaults" to your preferences (e.g., DSP filters, WPM, sidetone frequency and volume, equalizer, etc.), there's little need to use the TS system. Think about it. Jack, W8TEE
On Friday, September 21, 2018, 9:51:05 AM EDT, Buddy Brannan <buddy@...> wrote:
Sounds great, except, and understanding I¡¯m in a minority of 1 here, the touch screen. I¡¯d love this tied to a menu if needed plus a 4X4 keypad or such. ¡ > On Sep 19, 2018, at 10:28 AM, Jack Purdum via Groups.Io <jjpurdum=[email protected]> wrote: > > If we went to a screen that small, I think we'd drop the touch screen feature and do complete menu system. The costs aren't cheap compared to those display sizes (e.g., > $10 versus $34), but 5" at 800x480 is nothing to throw rocks at and is easier on the eyes for us old people. Also, quite a few have adopted the Nextion display and they cost twice as much as ours and are about half the size. Also, we give you an experimenters platform with a dozen empty pins and idle resources to play with (see feature set below). Also, we have a pretty robust feature set: > > 5¡± or 7¡± TFT Touch Screen 800x480 TFT Color Display > Dual VFO > RIT > S Meter > Real Time Clock (add optional battery) > 50 CW Preset Messages, selectable at runtime > Touch Screen Band Selection > Touch Screen Buttons for function selection and control > Dual Encoders: Frequency Tuning, ALS Tuning, Program Input > Frequency Tuning: >? ? Standard >? ? ALS Tuning--ALS Tuning: Special tuning using the second encoder. If the >? ? ? ? ? ? frequency increment is set to 1KHz, ALS Tuning sets the second >? ? ? ? ? ? encoder to one-tenth the increment of the primary tuning rate. This >? ? ? ? ? ? allows for rapid tuning to an approximate frequency using the main >? ? ? ? ? ? encoder and then using ALS Tuning with the second encoder to fine >? ? ? ? ? ? tune the signal. Once you use it, you'll wonder how you lived without it. > Filter Selection: >? ? CW presets (3dB bandwidth): 150 Hz, 300 Hz, 400 Hz, 600 Hz >? ? SSB presets (3dB bandwidth): 1500 Hz, 1800 Hz , 2200 Hz, 3000 Hz > EEprom storage of user preferences and CW code presets > 3 external hardware buttons for CW code messages (e.g., contest exchanges) > Based on Teensy 3.6 Microcontroller with Audio Shield > Hardware AGC using IF take-off > Mic Compressor with adjustable threshold > Mic 8-band equalization > Receive Audio Filter > 48 dB/octave (8 pole equivalent DSP filters) > 2 Variable bandwidth filters ¨C user-defined knee frequencies with Rotary Encoder control > Audio AGC with adjustable threshold > Variable Notch filter, encoder adjustable, use specified Q > CW code to Text converter > Code Practice Oscillator Mode > About a dozen I/O pins to play with plus 800K of free flash memory, 200K of free SRAM, >? ? ? all clocked at 180MHz > > > Finally, this is Rel. 1.0 of the software. We think we can do some pretty clever stuff with Rel. 2.0. You can see these board in the video here: > JackAl uBITX Add-on > > ??? > JackAl uBITX Add-on > This is a preview of the up-coming uBITX add-on board. Centered around a high-resolution touch screen TFT displa... > > We also think the system is flexible enough to adapt to other inexpensive rigs. Al and I plan to experiment with this after JackAl is released. > > Jack, W8TEE > > > > > On Wednesday, September 19, 2018, 1:18:36 AM EDT, Ashhar Farhan <farhanbox@...> wrote: > > > can this be adapted to small tft displays? the cost of going from a 2.4 inch to this display is quite high. > > - f > > On Wed, Sep 19, 2018 at 5:34 AM, Jack Purdum via Groups.Io <jjpurdum=[email protected]> wrote: > If you can run the Arduino IDE, I don't see why not. The software is all on the board. If you can't run the IDE, go to a school lab, borrow a Windows machine, ciompile/upload, take home and plug in...done! > > Jack, W8TEE > > On Tuesday, September 18, 2018, 3:58:45 PM EDT, Mike Lichtman via Groups.Io <tchrme=[email protected]> wrote: > > > Jack and Al, >? ? I concur. I also would prefer a ¡°all in one place¡± maxi purchase. Many of us have Macs and cannot use Ian¡¯s utility program. Will we also be able to utilize the Jackal? 73 Mike KF6KXG > > > > > |
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Re: Startied using uBit-x-Happy-Happy
Hi Dave, yes I am excited about the touch screen.- Its called a NEXTION
Dr. Ian has several websites on how to wire up, Here is where I bought on ebay.? I paid a little more because I wanted it sooner ($21) Make sure you get the size you want- a 2.4" was all that would fit in mine, but they make 2.8", 3.2" it all the way to 7" (which is about $70) Here is the url for Dr. Ian Lee's website (KD8CEC Read everything before you start. There are step by step procedures. You have to download the software to the radino-then copy his software and download on a microdisc(about $10) and put the microdisk in the display to download that. It took me about a day of fussing around.? I downloaded the hex fiiles to the arduino so I had to download the bootloader.? I think I could have used the arduino code from github, so I don't know why he perferes to work with Hex Andy - KM4TRT |
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Re: JackAl System Preview
Sounds great, except, and understanding I¡¯m in a minority of 1 here, the touch screen. I¡¯d love this tied to a menu if needed plus a 4X4 keypad or such. ¡
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On Sep 19, 2018, at 10:28 AM, Jack Purdum via Groups.Io <jjpurdum@...> wrote: |
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Re: Center Carrier (uBitx)
Hi Joe, I do have the the same result and pictures as you have and having in hands FT-950, and 2 SDRs all 0,5 m away from mBITX.
But with oscill parallel to dummy load you can get carrier level as -26 /-30 dB(my results) or even better. Allison has good understanding and hope she is right. But still for me hard to get how to solve the problem in practice. Go out to band with such SSB signal or use PA is not good idea. But still I like not noisy receiver! The idea is good but may be PCB layout and Si5351 has someting? George UR4CRG/RX3ARG( sorry for no pictures I am not good in PC) |
Raj vu2zap
George
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