Re: RF power chain mods and improvements..
first don't remove r2b..
I measure Voltage across the emitter resistor and then calculate it I=E/R.
I can run a calculator much faster than soldering iron.
The current is highest in Q22 and that will be under 20ma.? Q20 is somewhere about 8-15ma.
the amp has a max output below 1 milliwatt (about .1mW) so it needs only the current required?
to make the device work well.
First try the part and see where the currents land with existing values.
Allison
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I would like to drive the AGC board with 12V not 5V and assume this involves changing some resistor values. The voltage divider which biases the FET Q2 appears straightforward enough, changing R3 from 100k to around 380k.
The biasing circuit of the amplifier Q1 is more subtle. Changing R2 from 1K to around 2.2K (which seams reasonable) will reduce the slope of the load line, increasing the voltage gain of the amplifier and modify the behavior of the AGC. On the other hand, leaving R1 and R2 unchanged and increasing the voltage from 5 to 12 retains the voltage gain and relocates the quiescent point near the center of the new load line, where it should be. Am I wrong to assume that the only change needed is the value of R3??
?
Comments please. Mike N6CMY?
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I reversed the orange and purple leads and all is well.? Guess I had the mic wired opposite everyone else.
Thanks Howard and Bo!
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Re: The new uBITX boards are here
Hi, Farhan.What are the values of Diode 14, 15, 16 ? Thanks in advance.
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Re: RF power chain mods and improvements..
Allison
do you know how much current Q20, Q21, Q22 draws,the reason for asking is simple,i have a lot of BFR93 and?they only
handle 35ma and 300mw .i would like to avoid remove r2b to mesure it
OZ1LQB / Claus
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Re: Removing surface mounted resistor
#ubitx
For limited work my butane soldering iron (I think it is a Weller) has a hot air tip that works well. ?It is as hot or hotter than my embossing gun (cheap from Hobby Lobby or Joann's Fabric) and works for smd parts.
Dave K8WPE
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On Jun 6, 2018, at 10:17 AM, Ralph Mowery < rmowery42@...> wrote: There are lots of youtube videos on the SMD.? I would not worry about damaging the small parts as they cost almost nothing.
For a one time deal,you can put lots of solder on the part so it just sort of floats off and grab it with some stainless steel tweezers. Use the old standby of 60/40 or 63/37 tin/lead solder and stay away from the lead free stuff.
What I like to use is hot air.? For about $ 60 including shipping you can get one of the hot air rework stations.? While I doubt they would hold up for much usage, I have one and it works fine for hobby usage.? You get the hot air and a soldering pencil with some very small tips that you need.? It also works well on heat shink tubing.
Find some old computer boards that have the SMD on them and practice to you get the hang of it.??
If you plan on doing much smd work, plan on spending about $ 300 to $ 350 to get some equipment.? Look at an Amscope se400z microscope for just under $ 200, the $ 60 hotair rework station, and various? tweezers and a few other things.
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Re: Removing surface mounted resistor
#ubitx
Also, use solder wick to remove as much of the solder on the part as possible first.
Dave K8WPE
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On Jun 6, 2018, at 10:16 AM, Doug W < dougwilner@...> wrote: I probably reinvented the wheel but I figured out a trick that helps me with smd components.? I cut a small piece of plastic drinking straw and by sliding it down the tweezers they lock onto the component so you don't have to worry about dropping it.? Sure you can buy expensive tools that do that.? You can also buy an assembled radio.
--
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Re: RF power chain mods and improvements..
Dear Allison,? Thank you. Just a few clarifications please:
¡° I didn't? try 2n2963A as I didn't have any left in SMT but I suspect they would have been better.¡± I assume that¡¯s a 2N2369A, and what is a surface mount version called, if I wanted to find one?
?
Are the cores for T9 T10 & T11 the same toroids that it came with?? If one wanted to run more than ten watts would a different core be needed?
?
Is there any change in the chokes that feeds the finals? You didn¡¯t change to a bifilar wound choke?
?
¡°the 2n3904s in the predriver and driver replaced with 2n2222A¡± Instead of the TO-18 part, could I use these SOT-223s from Mouser: 512-PZT2222A? How about if I soldered a copper penny (pre 1982) to the large tab for a heat sink?
?
¡°Replaced Q10 with BFR106 for better receive gain at 20mhz and up.? (I may change out the two 3409s).¡± ?Are ¡®the two 3409s¡¯ Q11 & Q12?
?
¡°Add 1K resistor from negative side of C77 to ground¡± Is it C74?
Again, thank you for the experimentation and the information, I look forward to trying your mods.
jerry aa1of
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Re: Building homebrew ubitx: Need pre-v3 schematic PDF. Also, source for 45M15 (45 MHz IF) filter?
This appears to be a narrower 45MHz filter but impedance unknown
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Kj6etl, did you solve your tuning issue? I remember it as seeming similar to the issue I had. In my case it was what I first expected, ie a bum encoder and the new encoder made the issue disappear.?
Mike
On Jun 7, 2018 2:46 AM, "kj6etl" < pa1zz@...> wrote: Actually it was the fist time for me doing this with rather modest tools.
I clamped the board in a small vise and used a spring loaded solder sucker to remove the solder from all the pins on both sides.
Ended up using plyes to carefully pull the Arduino from the board. Then pulled the remaining pinns from the board one by one.
I think the the most challenging part is to solder the new Arduino back in place and avoid "bridges" between the solder joints. A magnifying desklamp is your biggest friend.
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I¡¯m trying to help you make it run on your Mac and for this have some questions, if you don¡¯t mind.
So you got a hex file or a ino file from Gary and you had to use Windows for uploading or compiling and uploading?
Did you use the Arduino IDE on Windows for this or used the ArduinoBuilder?
It¡¯s ?somewhat confusing.
i don¡¯t think it¡¯s a problem with your Mac if compilation fails. A lot of people, including me use Macs for Arduino development without problems.?
First you need to have a proper C ( ino) file, which according to the errors you posted is not the case. You are trying to compile a file with ?html content, so as already mentioned before obviously something went wrong with your download. The same file compiled under Windows would als have thrown errors.
Did you use the downloaded ?zip file from GitHub or used another method to fetch the files?
73 Armin, DJ2AG
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Actually it was the fist time for me doing this with rather modest tools.
I clamped the board in a small vise and used a spring loaded solder sucker to remove the solder from all the pins on both sides.
Ended up using plyes to carefully pull the Arduino from the board. Then pulled the remaining pinns from the board one by one.
I think the the most challenging part is to solder the new Arduino back in place and avoid "bridges" between the solder joints. A magnifying desklamp is your biggest friend.
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Re: Removing surface mounted resistor
#ubitx
Btw,? you don't have to remove anything to make the 'pop cure' mod. You can leave that resistor in and add another in series with it on an outboard circuit.?
- f
On Thu, Jun 7, 2018 at 3:25 AM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote: Could work.
But it's real easy to rip the pads off the board with any mechanical movement or pressure.
I use two soldering irons, one on each end.
Yes those surface mount parts are cheap.
And those those metal end pieces can separate away electrically when removing the part.
I avoid re-using them.
Jerry
On Wed, Jun 6, 2018 at 01:52 pm, K9HZ wrote:
I use a sharp awl to break them in the center easily.? Then remove each end.? Those parts are extremely cheap.
?
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Easy enough I suppose, but I do see a lifted pad there, 4 up from the bottom left. The biggest problem with most rework is damage to the board, though that one looks easy to deal with. How did you go about removing it?? My guess is a full blown rework station with vacuum solder sucker. If you clipped the pins first and pulled them out one by one,? I'm curious how you went about clipping them. A socketed Nano is nice, but then it mechanically interferes with the LCD display. I've socketed my Nano on the opposite side of the raduino as per this post ? ?? /g/BITX20/message/50027Quite happy with the result.
On Wed, Jun 6, 2018 at 09:08 pm, kj6etl wrote:
Its not that hard to replace the Arduino.I have done it on my uBitx and will do it soon on a Bitx40.
You can buy a
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Interesting. Did the
proposal go anywhere? Are you continuing development to
enhance the proposal or has the project now become a hobby in
itself, Mike?
Might have all sorts
of applications including home brew of the liquid variety.
Bill, VK7MX
On 7/06/2018 10:18 AM, Michael Hagen
wrote:
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Well, it is a Heater
Control.? Done with a Pic and Assembly done code.? Lots of
nice features.
I have not had a
paycheck in 3 yrs now, so this design was part of a
proposal.
This is the nth
change, I keeps going on and on?
A shot in the dark!
Mike, WA6ISP
On 6/6/2018 4:54 PM, William R
Maxwell wrote:
But now you
really should tell us what is, Mike.You have us all
curious.
Bill VK7MX
On 7/06/2018 9:30 AM, Michael Hagen
wrote:
A mistake,
sorry.? Went to group when I meant to send it to myself.
Mike, WA6ISP
On 6/6/2018 3:18 PM, Allen
Merrell via Groups.Io wrote:
I am lost
here, what is this.
--
Allen ?Merrell
--
Mike Hagen, WA6ISP
10917 Bryant Street
Yucaipa, Ca. 92399
(909) 918-0058
PayPal ID "MotDog@..."
Mike@...
--
Mike Hagen, WA6ISP
10917 Bryant Street
Yucaipa, Ca. 92399
(909) 918-0058
PayPal ID "MotDog@..."
Mike@...
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Re: RF power chain mods and improvements..
Tim,
The reason to add a stage of amplification like that is so we can reduce
the amplification of pretty much all the other stages.
With reduced gain, they have a much better chance of giving the same gain
at 30mhz as they do at 3.5mhz.
You could try patching this amp in when operating at 30mhz.
Turn RV1 down all the way, then slowly bring it up to get the power you want.
But you had best be ready to measure distortion in your signal before getting on the air with it.
It could well be that Q90 will not work properly with the 10dB increased input signal
and will distort.? Having the amp after Q90? allows you to adjust RV1 down until
any stage after the new amp does not have too strong a signal, strong enough to distort.
I don't think you want this new amp in there at all when operating on the lower frequencies
with an otherwise stock rig.? Too much gain.?
I'm just kibitzing here, have not analyzed the Q90 stage.
You could take the LT-Spice model for the uBitx power amp from the KE7ER directory in the
files section, see what the simulation does when Q90 is driven harder.
Jerry
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On Wed, Jun 6, 2018 at 07:36 pm, Tim Gorman wrote:
Allison,
Jerry,
I have my little mmic board built. Would it be ok to add it before Q90
by removing C80 and inserting the input and output on those pads. Doing
that would allow me to stick the board on top of the relay that is right
beside Q90. It would facilitate testing, experimentation, and
parts changeout if needed. It would also be right beside my 7812
voltage regulator so I would have short power leads.
Will another 10-12db of gain into Q90 be a problem?
tim ab0wr
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uBitx Encoder information needed.
I have 2 items I need info on.
first, does anyone have the specs for the stock encoder for the uBitx?
second, have any of you had to make software changes to get a KY-040 encoder to work properly?
Thanks for your help.
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Its not that hard to replace the Arduino.I have done it on my uBitx and will do it soon on a Bitx40. You can buy a  
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My ubitx was about 1600 to 1700 khz wide.? By changing the 5 capacitors from the crystals in the filter to ground from 100 pf to 82 pf the bandwidth widened out to about 2400 hz for the same reduction in power/audio bandwidth. ??
That may be slightly too wide, but was the next value down from 100 pf that had.? I did try the next value down first, but it was way too wide.? I have been thinking of paralleling the 82 pf ones with about 5 pf but have not done it.?
On Wed, Jun 6, 2018 at 6:11 PM, Eardan <ke4htb@...> wrote: Im currently using KD8CEC skecth and my audio is about 200-1800 and im want to change it to 200-2400 range. i have no problem using the IFS to get it into range but have had no luck changing it in the sketch so that i dont need to use IFS any help to figure this out would be nice
thankyou
KE4HTB
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Re: Removing surface mounted resistor
#ubitx
Another option is to use Chip Quik solder remover. This product is heated with your iron over existing solder joints forming a low temp melting point alloy whi ch stays liquid long enough to lift the part off with tweezers. Then remove the low temp stuff with removal braid.
--
Kevin B. G. Luxford
kbgluxford@...
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David Wilcox K8WPE
kj6etl