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Re: uBitx and QCX review in QST August 2019
¿ªÔÆÌåÓýARRL isn't a marketing firm, and I believe the video is kept behind a paywall for subscribers only.Again, you can't buy the uBitx without going to HF Signals, who makes it very clear what is included and what the user must supply. The video the ARRL produced meets the needs of the ARRL - I've never seen any of their 'in depth' videos get used as marketing collateral by any manufacturer, that's not what they are made for. If someone chooses to repurpose it outside the ARRL it is on that person to overcome any shortcomings the video may have in its new role. My $0.02 worth, Ken, N2VIP On Aug 11, 2019, at 11:26 AM, Robert McClements <gm4cid@...> wrote:
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Re: Calibration success
#ubitx
#calibration
Dean,
I assume that you were whistling or saying "Helloooooo" into the mic when measuring.? My v4 and v5 uBitx both do not register power out until audio is applied. If you were able to calibrate with the stock firmware, it went into transmit mode for the calibration.? Did that register on the watt meter? Dan's suggestion on CW as a test is the correct course.? It will verify if you have an RF or Audio issue. If the CW checks out, then you wight want to wire up the supplied mic and button to the supplied 3.5 mm plug and try it.? I am pretty sure that the case kit that you got has both the 4 pin and 3.5 mm connections for the mic/PTT. 73 Evan AC9TU |
Re: Want to increase audio gain in Q70 stage of Ubitx - ideas?
After a short discussion on EMRFD regarding the "minimalist DC receiver" (which uses the same gain stage design) resulting in a detailed explanation from W7ZOI (see there if interested), and previously more experimentation on my bench around different devices and bias settings, I've realized that I cannot solve the problem in the single NPN stage as originally envisioned.
As an alternative approach, I am taking the output of the AGC driver from the TDA2822 (U1-3 that ends up delivering output across R72), then coupling that signal into the audio gain pot which in turn drives U1-7. This provides a surplus of gain in this path (it puts the two stages of the TDA2822 in cascade) so that the audio gain control is now useful and can easily drive the output section of TDA2822 into clipping on no-signal noise (my original goal). Some further work will be needed to ensure that the AGC detector (D10 etc.) does not adversely influence the audio at that point. Dave |
Re: uBitx and QCX review in QST August 2019
Robert McClements
?Ken Hansen, yes, agreed,? the QST article does make these points.
The video will be seen by many who do not have access to QST and who are not familiar with the uBitx and they will get??information about the product. that is a very incomplete and potentially open to misinterpretation. As I stated earlier, ARRL could have done much better, disappointing. Bob GM4CID |
Re: Calibration success
#ubitx
#calibration
Thanks Dan -
I will give CW try. I have a watt meter on the antenna output so that is how I know there is no RF out. The mic is a cobra/uniden electret CB mic.? I believe the element is essentially identical to the element that came with the kit. ? Dean |
Re: Calibration success
#ubitx
#calibration
¿ªÔÆÌåÓýDeanIf you haven¡¯t tried it you might go into cw mode and see if you get RF power out in that mode. You can just use a piece of wire for the key if needed.? If you get CW power and the mike ppt works it is likely the Mike or audio amp isn¡¯t driving the modulator. Does your mike need a dc bias voltage to generate audio? ?? Sounds like you are on the right track.? Dan W3BU? On Aug 11, 2019, at 10:12 AM, Dean Souleles <dsouleles@...> wrote:
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Re: uBitx and QCX review in QST August 2019
¿ªÔÆÌåÓýThey make it clear in the print article that the case was optional, citing the source, cost, and shipping, as well as including a stand-alone photo of everything that comes with third-party case they selected.In addition, HF Signals does a good job explaining what is and is not included with their semi-kit. I think confusion will be minimal, and the alternative would have been to 'review' the board without a case. Ken, N2VIP On Aug 11, 2019, at 9:52 AM, Doug W <dougwilner@...> wrote:
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Calibration success
#ubitx
#calibration
Hi all -
Thank you for all the suggestions and advice.? Here is my The solution to my garbled audio turned out to be adjusting the BFO -? Factory was 11.054.220 My setting: 11.056.220 Master calibration is unchanged from factory: 131250 I upgraded to the CEC firmware and? used ubitx memory manager. Next step - transmitting - my radio doesn't appear to transmit. ? I'm using a uniden/cobra mic connected through the 4 pin connector that came with the amateurradiokits.in case.? Mic is wired pin 1 shield, pin 2 mic audio, pin 3 tx control/ptt, pin 4 not wired.? The PTT kicks in but as far as I can tell, there is no RF out.? Need to recheck the wiring - but after that I don't quite know where to start. ? Dean KK4DAS |
Re: uBitx and QCX review in QST August 2019
On Sun, Aug 11, 2019 at 02:39 AM, Robert McClements wrote:
Review video not up to usual ARRL standards - could have done better.Glad to see more coverage for the ?BITX but the video showing an aftermarket enclosure as if it is standard is only going to create confusion. ? -- |
Re: Zero beating / calibration using old Drake method
Definitely by the time I got my novice (late 70s) VFOs were allowed; I quickly came to appreciate the value of that VFO.
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On Sat, Aug 10, 2019 at 09:35 AM, Jack Purdum wrote:
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Re: Voltage for finals
MVS Sarma
Definitely the LM317 is more power hungry. Have a good sized heat sink on it. It has to adsorb 5 volts at maybe 150-200 milliV But a linear is quiet and I thought that the having the receive quiet was worth it. Not measured however. The computer power supply is linear I am pretty sure. I was not sure whether to change the settings the bias so I left it alone. The uBITX puts out more than 20w on 40 and higher on 80 which I hardly ever use. It is a v3 radio. It also has large computer heat sinks At least 4x heavier than the stock heat sinks. a 80mm low speed fan and a printed shroud. The output transistors don't go above ambient in digital mode at 20 watts with 1:1 SWR. My technique is to touch the transistors. I figure the less heat the less degradation there will be. |
Re: Tuning Potentiometer
Actually, the value of the pot is not that important and a 10K will work as well as a 100K. The pot is between 5v and ground and you are just adjusting the voltage when "tuning" and that doesn't depend on the pot value.
The "jumping" is part of the original design. Since the ability to tune (especially with a single turn pot) gets very hard with the small adjustment available, the program is design to start jumping at either end (voltage close to zero or 5v) to step to a new tuning range. There are some fixes for that if you don't like it. One is to add resistors and shorting push buttons so it never reaches the end of rotation range, but you can step up or down with the buttons. Another is to modify the code to change the range you want to tune and even eliminate the jumping. I suggest loading Allard Munter's sketch for the BitX40 as it allows you to easily change the range you are tuning from the menu and offers a better tuning resolution through the technique of quickly averaging a bunch of readings for more accuracy. It really makes a fine improvement on the BitX40 and his illustrated instructions for some simple hardware mods (not required) add even more flexibility. =Vic= |
Measurements of Finals Temp changes with and without Fan shroud...
A couple weeks ago I released a fan shroud for the "tall" Sunil case. See?
Since then, I was curious on its effectiveness vs just heat sinks or heat sinks and a fan.? So here are the results.... Test Setup: - ubitx v4 with stock PA transistors and the new larger heat sinks being shipped with the case. - Noctua 1800RPM 80mm 12V fan (Blowing in) - Little Volt/Temp guage that I mounted on my front panel (unfortunately, I accidentally purchased the fahrenheit version...) Search for: " DROK Car Voltage Temperature Display" on amazon. - Unfortunately I took the "shroud measurements" on a different day than "no shroud". So focus on temp gain from "ambient" as a comparison - First set of tests were 5 minutes @ 40m into a dummy load - Second set was FT8 CQ into a dummy load until the watchdog timer terminated transmissions. The Results.... No Shroud .? ? ? ? ? ? Ambient? ? ? ? ? ? ? ? ? After 5 Min Xmit? ? ? ? ? ? ?Temp Gain Fan Off? ? ? ? ? ? ? ? ? ?81F? ? ? ? ? ? ? ? ? ? ? ? ? 128F? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?+47? Fan On? ? ? ? ? ? ? ? ? ?76F? ? ? ? ? ? ? ? ? ? ? ? ? ?94F? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? +18 WITH Shroud .? ? ? ? Ambient? ? ? ? ? ? ? ? ? After 5 Min Xmit? ? ? ? ? ? ?Temp Gain Fan Off? ? ? ? ? ? ? ? ? ?83F? ? ? ? ? ? ? ? ? ? ? ? ? 128F? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?+45 Fan On? ? ? ? ? ? ? ? ? ?81F? ? ? ? ? ? ? ? ? ? ? ? ? ?98F? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? +17? ? ? It looks like 5 minutes into a dummy load implies that a Fan is probably as good as a Fan and a Shroud.? However, I went on to measure FT8 CQ (into Dummy, until watchdog kicked me out) WITH Shroud .? ? ? ? Ambient? ? ? ? ? ? ? ? ? After 5 Min Xmit? ? ? ? ? ? ?Temp Gain Fan Off? ? ? ? ? ? ? ? ? ?84F? ? ? ? ? ? ? ? ? ? ? ? ? 105F? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?+21? ? ? ? ? ? ? ? ? ? ?? Fan On? ? ? ? ? ? ? ? ? ?82F? ? ? ? ? ? ? ? ? ? ? ? ? ?88F? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? +6? ? Of course the missing measurement is the FT8 CQ with just a Fan. Thought of this test *after* I put everything back together. :-( . Next time I tear things apart I will update with this missing result. Meanwhile, if anybody out there wants to run this test, I would sure be interested in the gain. 73 Mark AJ6CU |
Re: Want to increase audio gain in Q70 stage of Ubitx - ideas?
On Sat, Aug 10, 2019 at 11:46 AM, Gordon Gibby wrote:
It¡¯s a simple biasing circuit, if the collector voltage rises a bit then more base current will be injected to bring the collector voltage lower.Gordon covered the Q70 biasing arrangement very well, too. Tom, wb6b |
Re: New build - setup / calibrartion question
#calibration
#ssb
So there is a early draft users guide in the folders section with the following calibration steps. There may be better instructions in some other guide.? I am way too lazy to do a complete search.?
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Re: New build - setup / calibrartion question
#calibration
#ssb
Gordon Gibby
¿ªÔÆÌåÓýThe fact that you have to turn into a higher frequency indicates the internals of the microbitX may be at too lower frequency but you will figure it out. ?Try anything, it will either get better or worse.Once you get it close, you can fiddle with the audio spectrum analyzer to get it within a couple of Hz.?
The crystal is not in an oven, so it¡¯s going to move just a bit with temperature.
Every single one of them that I have seen is off, because the circuit does not provide exactly the capacitance they were cut for. ? The oscillator is supposed to be around 20 MHz I believe and every single one I have seen is off by about 4 kHz
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Re: Want to increase audio gain in Q70 stage of Ubitx - ideas?
Hi,
Usually I'm bothered when I see a transistor amplifier without an emitter resistor. The gain should be set by the ratio of the collector resistor to the emitter resistor and be set significantly below the gain of the transistor. This is so things will be stable and you can do large production runs of products and not have to stop production to determine how to fix the product (or add adjustable pots that will cost labor time to adjust) every other time you get parts from a different supplier or batch. The other important thing the emitter resistor provides in stability of the bias point of the transistor. As the emitter provides a negative feedback based on how much current flowing through the collector. This works to keep the voltage around 1/2 the Vcc with wide variations in the gain of the transistors. In the case of Q70 the next stop for the audio is a volume control, so if the gain is higher or lower in various batches, so be it. Likely nobody will notice. In the case of the "wide open" Q70 it is important to note that the bias resistor is connected from the collector to the base. That is an alternative form of negative feedback for keeping the bias level from going out of bounds. If a batch of transistors with higher gain were used, the gain of the transistor would tend to want to conduct more and drive the collector voltage down. Maybe so close to ground, the amplifier would not work. But, the collector voltage goes down, also reducing the bias current. That limits how far the collector voltage can go off from the optimal middle point. Low gain transistors would be the same idea but the reverse would happen, keeping the collector voltage from going too high from center. The impedance of the audio feeding Q70 from the mixer is low enough that the 100K bias resistor should not provide much negative feedback at audio frequencies and lower the audio gain. It is surprising that higher gain transistors did not make a noticeable difference. Although they would need to be more than twice the gain to be noticeable to the ear, per common wisdom. Maybe changing Q70 to a darlington and adding an emitter resistor to tame it down some might work.? Another thing that has been discovered by folks that have had low transmit power, or trying to boost it further, is the supply voltage (especially below 12/13 volts) has a major effect on the obtainable transmitter power. A large contributor to that seems to be that the gain of the IF chain drops significantly below these voltages. As the same IF chain is used for transmit and receive, running those circuits at 9 volts may be a problem. Your measurements on your radio will let you know if this is an issue. Tom, wb6b |