Date   
Re: Series Diode in Power Supply Line #ubitx

Jerry Gaffke
 

An LM2940T-12 is similar to an LM7812 except that it is low dropout, offers polarity protection, and is not quite so prehistoric.
I'd recommend a 3A fuse between power supply and the rig, use an LM2940T-12 inside the rig to power the main board.
Have the power supply with 3A fuse drive the IRF510's directly to avoid overloading the LM2940T-12.
If the supply is reversed, the intrinsic diodes in the IRF510 will conduct and blow the fuse.
With that arrangement, you could supply 20vdc to the rig if you want more power, the main board will still only get 12v.

For a really cheap solution on a high volume project where we can assume the power supply voltage
does not exceed the maximum that the rig can handle, replace the LM2940T-12 with a small shottky diode.
Offers polarity protection, and a short on the board will blow the diode.

A search for "reverse polarity" in this forum will find long discussions with dozens of ways to do this.
One of those things that everybody seems to have an opinion on.
Including me.

Jerry, KE7ER


On Wed, Aug 7, 2019 at 08:21 AM, Ashhar Farhan wrote:
I would second that. A voltage regulator is best. However, the generic ones like 7812 will need at least 15v (3v more than the output) as their inpit voltage. A small 1uf and a couple of 0.1u caps across the output makes for a nice, low noise supply.
 

Re: Voltage for finals

Evan Hand
 

Did not use it for the finals, though did try one for the full system.  Generated some noise, so you do have less sensitivity compared to the normal QRN.  If only used on the finals, may not be an issue.

Since there are 30+ amp switching supplies for other rigs, I would think that if you found the right unit the noise would not be significant.  It is just that the units that I tried did generate noise.  Might also be able to filter out the noise with active or passive filters.

My 2 cents
73
Evan
AC9TU

Re: Full QSK for a uBITX

John Seboldt K0JD
 

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

On 8/6/2019 15:01, Tom, wb6b wrote:
On Tue, Aug 6, 2019 at 08:26 AM, Jerry Gaffke wrote:
including "ElectronicAntenna Switching" by Wes Hayward 
I was able to find the Wes Hayward article on-line. 
https://archive.org/stream/QEX19812016/QEX%201995/QEX%201995-05#page/n3/mode/2up

Tom, wb6b

Re: Full QSK for a uBITX

Jerry Gaffke
 

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

Re: Transmit Trouble

Curt
 

harry

you are doing well with all that advancing, and i sense you are close with the ubitx. did you install that 4.7k resistor that is needed for transmit?  I call there is also a menu setting to tell it to expect a manual key and not a paddle.  with the proper menu setting and that resistor a short circuit across the key should place it into cw transmit.  note you need to speak or whistle into the microphone to get any ssb transmit output.  check things patiently and I expect you will solve it.  maybe we can qso via ubitx this fall. 

73 Curt

Re: Transmit Trouble

harryoliver196410@...
 

Thanks Curt,
That makes sense - yes I have the resistor there but I haven't specifically checked the menu settings so I shall definitely do that. It's 1:30am here so I think I should probably leave it till the morning but I will let you know how I get on. 
Thanks again. 
Harry

Re: Voltage for finals

 

My plan is to use them only on the battery circuit, and possibly to power something that needs a stable 5v supply with proper filtering.

Matthew N8OHU


On August 7, 2019 1:31:55 PM EDT, John Faivre <wa9sgd@...> wrote:
Has anyone tried using a buck boost module to raise the finals voltage supply? I’m worried about the noise from the supply ending up causing spurs on my output.

How high have you successfully run the final voltage, and with what heat sink setup.

thanks for you help 

--
Sent from my Android device with K-9 Mail. Please excuse my brevity.

Re: Voltage for finals

Don - KM4UDX
 

John -- do it the reverse.  Start with an old 15-20v laptop power supply. Put a 2a fuse and drive the finals direct from the laptop brick voltage.  Use the buck converter to generate 12v for the board from whatever the laptop brick squrts out.  I added a simple LC ripple filter (used in RC drones) to the 12v output, but it made no detectable difference to anything I could observe. With 17v, I get ~28 watts on 80m, and the normal 3 watts on 10m.  Good enough for all the digital modes, and yes, marginal for SSB DX, says me. Others disagree. 

Increase the size of the heat sinks, or go active if you up the final voltage. Not that the finalls need it in normal operation, but to cover a likely bone-head move by the operator. Don't ask me how I know this. 

In anycase, it is (largley) over driving which generates spurs and uggly bits.  Not the PSU ripple.

Don
km4udx

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

Don - KM4UDX
 

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

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

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

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: 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

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

David Wilcox
 

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

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: 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

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: 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: CH340 Driver Install

JT Croteau
 

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