Date   
Re: ubitx calibration

Alan de G1FXB
 

In addition to choosing a higher frequency carrier to zero beat, remember the Human deficiency......
The "perfect" Human hearing is generally specified as 20Hz to 20KHz so will not directly hear the zero beat (0Hz error), in a perfect world you should get to within 20Hz........
It's hit or miss to manage to get closer by ear.

Observe the zero beat using the S meter wobble / use a scope to look for the resultant 0Hz trace
Also the response of the IF, filter(s) / skirt, demod and audio stages will all play a part especially if the VFO is off when looking for zero beat?

The workaround for precision is to choose a convenient audible beat tone say 500Hz or 1KHz to make the measurement and some arithmetic to get the true carrier freq.
Best check the methods of the ARRL FMT / K5CM, even an SDR dongle can make the grade.....


Alan



On 08/08/2019 23:51, Tom, wb6b wrote:
I believe that what you did, calibrating to a medium wave signal is a suggested alternative in the uBITX calibration instruction. It should work OK.

The higher the frequency you use to do the calibration, the better the accuracy will be with a given amount of zero beat as accurately as can be determined by ear. Of course, the signal you calibrate to, whatever frequency, should be accurate themselves.

Tom, wb6b

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Re: ubitx calibration

Tom, wb6b
 

I believe that what you did, calibrating to a medium wave signal is a suggested alternative in the uBITX calibration instruction. It should work OK.

The higher the frequency you use to do the calibration, the better the accuracy will be with a given amount of zero beat as accurately as can be determined by ear. Of course, the signal you calibrate to, whatever frequency, should be accurate themselves.

Tom, wb6b

 

UBitX V3 Nextion and no receive

V Zecchinelli
 

Good Afternoon,
My UBitX V3 was working fine and I decided to install the Nextion display using ubitx_lcd_nextion.ino.  All seems to work fine but I am unable to receive any stations.  I am using A3 Beam at 60' elevation.  I am able to hear tones around 14.273.6 on UBitX and Kenwood TS2000 but unable to distinguish and other signals with UBitX.  Through the headphones it sounds more like electrical static than atmospheric noise.  Same symptoms with 2 different Raduinos.  Not sure where to look for the issue.  BTW, UBitX does transmit.
Thanks,
Vince

Re: CH340 Driver Install

Tom, wb6b
 

On Thu, Aug 8, 2019 at 11:39 AM, Gary Anderson wrote:
You weren't the only one.
https://groups.io/g/BITX20/message/65276
Yet another twist on the tormenting USB cables. Poor tolerances could be another issue with some of the cables I've had issues with. 

Tom, wb6b

Re: CH340 Driver Install

Gary Anderson
 

JT,
You weren't the only one.
https://groups.io/g/BITX20/message/65276
Gary

Re: CH340 Driver Install

Tom, wb6b
 

On Thu, Aug 8, 2019 at 10:23 AM, JT Croteau wrote:
Solved cable problem 
I'm having this same issue more and more. Many of the gadgets now days are shipping with a power only USB cable that has no markings or other indications it is not a complete USB cable (has the full USB compliant logo and everything). I've endured frustration many times when I accidentally grab and use one of these cables and try to debug or program a processor board. I've put a label on everyone I've found so far, but, surely, there is one more lurking in my cable box to get me late at night and torment me when I just want to get something done and get to sleep.

Tom, wb6b

Re: Full QSK for a uBITX

Tom, wb6b
 

Hi Jerry,

In the video, when enough current to assure full conduction was used, all was good. Also, as the frequency was raised the amount of current needed was less.

When the current was lowered to a level that full conduction was not happening (the variable resistance region used when a PIN diode is used as a variable attenuator) there was not much useful range in this region before lowering the current a little more, let the PIN diode "run out" of stored carriers on the negative (in the case of his test setup) side of the waveform.

However, I believe in retrospect that the signal levels passing through a PIN diode variable attenuator in applications such as a receiver input attenuator, would be orders of magnitude less than in his test setup, as he was interested in power RF switching, and dancing around the part of the curve that produced the distortion would produce less dramatic effects in the case of very low signals embedded on the forward current biasing the PIN diode.

How close you can dance on the edge of the curve is likely the major part of the maximum signal level and IM specs of PIN diode variable attenuators.  

Tom, wb6b

Re: CH340 Driver Install

MVS Sarma
 

JT Croteau,
Congrats . All the while we were thing only software and compatibility !!

 All the best


On Thu, Aug 8, 2019 at 10:53 PM JT Croteau <jt.tobit@...> wrote:
Solved cable problem   I found another cable in my junk box and it works fine.

Thanks

On Mon, Aug 5, 2019, 22:52 Tom, wb6b <wb6b@...> wrote:
Hi,

There were a number of threads last year about where to find drivers (ones that didn't crash, were signed, etc). I think the manufacture's website is now the best place to get the driver. Just Google the chip number and try to find the actual manufacture's site and their driver download area.

Tom, wb6b

Re: Si5351 minimalist routine

GM4CID
 

Jerry, thank you for the explanation which I also stumbled accross in the CEC sketch comments.
Works well, starting with a divisor of 4 to generate a fixed output of 200kHz
then rdiv back to 0 to give normal frequency generation above 500kHz.

73, Bob GM4CID

Re: CH340 Driver Install

JT Croteau <jt.tobit@...>
 

Solved cable problem   I found another cable in my junk box and it works fine.

Thanks

On Mon, Aug 5, 2019, 22:52 Tom, wb6b <wb6b@...> wrote:
Hi,

There were a number of threads last year about where to find drivers (ones that didn't crash, were signed, etc). I think the manufacture's website is now the best place to get the driver. Just Google the chip number and try to find the actual manufacture's site and their driver download area.

Tom, wb6b

Re: Fan Shroud for Sunil's "taller" cases

Mark Hatch
 

So been testing this on ft8 and using CQ's until watchdog kicks in (occasionally picking up a QSO!)

Warning:

If you use this shroud, you must have a fan on when transmitting. Otherwise, the shroud captures the heat and the finals heat up higher than they would with no fan!

I am going to install a temp sensor and relay to turn the fan on and off. But until it gets here in 3 weeks, I am going to turn the fan on when I am transmitting. (BTW: I have seen other suggestions on driving the fan off the transmit relay, that is another option. The problem is when you go out of transmit, the fan goes off and you don't get a cool down period in preparation for next transmit.)

73
Mark
AJ6CU

BTW: With these larger heat sinks, my finals on ft8 don't go above 30C (ambient 22C) with no fan and no shroud even with lengthly ft8 duty cycles.

Re: Full QSK for a uBITX

Jerry Gaffke
 

I haven't watched the video but "the bottom end dropped out" suggests to me that he is operating at too low a frequency for his particular PIN diode.
The idea of a PIN diode is that it need only be forward biased for part of the waveform, for the remainder of the waveform there are residual charge carriers available in the diode to carry the current.  Minimum frequency is determined by the "charge carrier life time", which is the average amount of time that those charge carriers remain available.  Take a look at the spec's for NXP's BAP64Q attenuator.  PIN diode attenuators get used successfully in many many places.  In a normal diode such as the 1n4148, there are virtually none of these charge carriers available once the diode gets reverse biased.

Jerry, KE7ER


On Thu, Aug 8, 2019 at 03:00 AM, Tom, wb6b wrote:
Also, from the video, it looks like if you use PIN diodes as a variable attenuator the design will need to carefully consider the forward current through the PIN diode throughout the full RF cycle. It looks like it requires a careful balance to keep the PIN diode acting as a "linear" current controlled resistor rather than reverting to not conducting on half the RF cycle and introducing severe waveform distortion.  

Re: Voltage for finals

Don - KM4UDX
 

Here is a pic of the dc-dc which makes 12v for the board (and a few other accessories).  The "native" power from the old laptop brick goes straight  through a fuse and to the finals. Note the LC filter after the dc converter.  I'm not sure it makes any difference, but it looks cool.  

Re: Full QSK for a uBITX

Tom, wb6b
 

On Thu, Aug 8, 2019 at 12:14 AM, kh6sky wrote:
W2AEWs video on PIN diode switching
Very good video.

Also, from the video, it looks like if you use PIN diodes as a variable attenuator the design will need to carefully consider the forward current through the PIN diode throughout the full RF cycle. It looks like it requires a careful balance to keep the PIN diode acting as a "linear" current controlled resistor rather than reverting to not conducting on half the RF cycle and introducing severe waveform distortion.  

You could see that on his scope display where, as he lowers the current, the amplitude of the positive half of the waveform decreased for a while. But, soon, rather dramatically, "the bottom end dropped out" and the scope was displaying a very distorted waveform. This must limit the useful range of PIN diodes as variable attenuators. Many designs do use multiple PIN diodes to improve the attenuation obtainable. Just looks like PIN diode variable attenuators might be dancing closer to the edge of distortion than I'd imagined. Maybe I'll stick to using them in step attenuators. 

Tom, wb6b

Re: Another uBITX v5 FT8 success story #ft8 #v5 #ubitx

David Wilcox <Djwilcox01@...>
 

Does anyone know if overheating the finals causes damage to them if on cooling they still work........ I would wonder if the output is the same as when they were new.

David J. Wilcox K8WPE’s iPad

On Aug 7, 2019, at 10:31 PM, Don - KM4UDX <dontAy155@...> wrote:

Arvo -- hahah.  

Q: do you have to worry about the fan current if you hack into the TX 12v line, namely at pin 3 on U2?

Don
km4udx

ubitx calibration

terryhugheskirkcudbrifght@...
 

hi

i have calibrated my ubitx to a medium wave station on 1485 k hz.

can anybody tell me if the calibration will be good up to 40 mtr

i cannot hear www hear in scotland

terry gm4dso

Re: calibrating ubitx to www

terryhugheskirkcudbrifght@...
 

hi
i have calibrated mu ubitx to a medium wave station on 1485.k hz

can anybody confirm that it will be good calibrated up to 40 metre

i cannot hear www on 10 m hz

terry gm4dso

Re: Full QSK for a uBITX

kh6sky
 

Take a look at W2AEWs video on PIN diode switching for a good intro to the subject.  Using the simple test setup in this video you could check the suitability of the 1n4007s for this purpose.  Interesting that the turn on characteristic of the PIN diodes is so strongly affected by frequency.

https://www.youtube.com/watch?v=XpYsCM_Wf50

Jim KH6SKY

Re: Full QSK for a uBITX

Jerry Gaffke
 

Thanks for finding that, seems right.
I think D3 and D4 are drawn backwards.


On Wed, Aug 7, 2019 at 08:20 PM, Vince Vielhaber wrote:
According to the voltage chart on the next page, that junction is going to have a large negative voltage on it. That would stop the transmit from going to the receiver.

Vince.
Hide quoted text

 

On 08/07/2019 07:35 PM, Jerry Gaffke via Groups.Io wrote:
Here's a manual for the Argosy, T/R switching (and SWR metering) is on
page 51:

http://www.tentec.com/wp-content/uploads/2016/05/Argosy_II_Model_525_Manualf933.pdf
;;; D1,D2 look to me like they would be forward biased during transmit,
which would not work at all.



 

Re: Full QSK for a uBITX

Vince Vielhaber
 

According to the voltage chart on the next page, that junction is going to have a large negative voltage on it. That would stop the transmit from going to the receiver.

Vince.

On 08/07/2019 07:35 PM, Jerry Gaffke via Groups.Io wrote:
Here's a manual for the Argosy, T/R switching (and SWR metering) is on
page 51:

http://www.tentec.com/wp-content/uploads/2016/05/Argosy_II_Model_525_Manualf933.pdf
The full transmit RF waveform goes through C1, diode D4 ensures the
bottom of that
waveform is at DC ground, diode D3 then rectifies it to create a DC
voltage across C2 that
is equal to the peak-to-peak voltage of the transmitted RF. The notes
then say that this
relatively high DC voltage available during transmit is used to reverse
bias diodes D1 and D2
such that no transmit signal goes through them to the RCV connector
(which then goes into
the receiver front end).

I'm still staring at it, almost have it figured out.
But D1,D2 look to me like they would be forward biased during transmit,
which would not work at all.

Note that the PIN diodes at D1,D2 are called out as 1n4007's.
And that this transceiver works up through 30mhz.

Another thing to note, the final remains connected to the antenna during
receive,
shunting some of the receive energy to ground.
Some of the other T/R switches use additional PIN diodes to isolate the
final
from the antenna during receive.

Jerry, KE7ER


On Wed, Aug 7, 2019 at 01:37 PM, John Seboldt K0JD wrote:

This is quite interesting, with a nice sophisticated full-tilt
switch. Interestingly, the Ten Tec Argosy (50W) derives the high
voltage back bias from the RF itself with some silicon diodes and
filter capacitors, so providing a full high-voltage power supply is
a bit of an overkill.

John K0JD