Date   
Re: bitx v6 is here

Anthony Gomes
 

Thank you Farhan Sir.  Now we know what was brewing at HF Signals. I just completed my homebrewing of V5 ubitx from scratch, looks like time to go back to my bench again :)  I would love to come down to LARC meet but this year I have to give it a skip.

73
Anthony
VU3JVX

bitx v6 is here

Ashhar Farhan
 

People,

Here is what it looks like :
And of course, yoiu can buy it on hfsignals.com. The shipping will happen from Tuesday onwards. We have a limited supply of the first 200 boards. The rest is for after christmas.

The most important thing about this revision is that the  Radio circuitry is almost unchanged. We have incorporated the connectors on the PCBs. So, this kit needs none of the confusing soldering. You snap in the TFT Raduino onto the main board, plug the power and antenna from the back, snap on headphones, plug in the mic (supplied with the kit) and off you go!

It is offered in two kits now : The basic kit (150 USD) is without the box (like old times) but with a microphone and two acrylic templates for the front and back panels. 
The Full kit (199 USD) has the box with speaker, mounting hardware etc. Both are described on the website. 

Now, about the TFT display: 

For those who are using the 16x2 display and you would like to upgrade, you will have to do three things:
1. Add a heatsink to the 7805 of the raduino
3. Grab the new Arduino sketch from https://github.com/afarhan/ubitxv6

Background : 
I have been hacking away at adding a TFT display for the Arduino for sometime. Finally, I managed to do this with a really inexpensive 2.8 inch TFT display that uses a controller called the ILI9341. The display update is slow but, clever guy that I am, the display very usable. it uses the same pins that earlier connected to the 16x2 LCD display. This display is available everywhere for a few dollars. 

Re: Black Squares on Raduino Display Redux #bitx40 #raduino

 

Pat,

The last one (Bitx40 I built a few months back) I had put the display connection in on the wrong set of pins, a common issue with the current instructions.

I would check to make sure its in the right spot (post a pic maybe). It sounds like the nano is dead, I had the very same issues. Boots, screen on, black squares....death everything went blank.

While the nano leds will still work the rest is dead.

If you haven't get a spare nano clone or otherwise and try flashing the firmware before even plugging it into the radio.

Hope that helps

73
--
David

 N8DAH
Kit-Projects.com

Shop is open!

Re: µBITX & QRP labs 50W PA

Ashhar Farhan
 

Hans,
Even 25 ma idle current should be enough, given that it is a push pull amplifier and a large part of the power cycle keeps one or the other transistor switched on.
- f

On Fri, Dec 13, 2019 at 10:36 AM Hans Summers <hans.summers@...> wrote:

Hi all

Changing amplifier class is firstly a matter of altering the idle current. It requires an increase in bias to increase the idle current (NOT a decrease in bias). That is the first thing to try. 

But it would help to have capability to measure the results to see how good the linearity is and what the limitations are. Two tone audio test signal and RF spectrum analyzer. 

The circuit is essentially similar to my 10W Linear kit http://qrp-labs.com/linear 

Yes biasing the transistors for 125mA each (for example) would dissipate power straight away even with no input. That would be 2.5W per transistor at 20V supply. Whether it needs MORE cooling or not is not so straightforward to answer though. CW is a full power, intermittent carrier. SSB operates at a lower average level but without so many breaks (except when you take a breath etc). Any speech processing you have will increase the average power. Which is more, CW or SSB... I think it needs some experiment. Probably this amp can be biased to AB but I haven't had time to test all this as yet. 

73 Hans G0UPL 

Re: µBITX & QRP labs 50W PA

Hans Summers
 


Hi all

Changing amplifier class is firstly a matter of altering the idle current. It requires an increase in bias to increase the idle current (NOT a decrease in bias). That is the first thing to try. 

But it would help to have capability to measure the results to see how good the linearity is and what the limitations are. Two tone audio test signal and RF spectrum analyzer. 

The circuit is essentially similar to my 10W Linear kit http://qrp-labs.com/linear 

Yes biasing the transistors for 125mA each (for example) would dissipate power straight away even with no input. That would be 2.5W per transistor at 20V supply. Whether it needs MORE cooling or not is not so straightforward to answer though. CW is a full power, intermittent carrier. SSB operates at a lower average level but without so many breaks (except when you take a breath etc). Any speech processing you have will increase the average power. Which is more, CW or SSB... I think it needs some experiment. Probably this amp can be biased to AB but I haven't had time to test all this as yet. 

73 Hans G0UPL 

Re: V4 TX problems and new finals #ubitx-help

Jerry Gaffke
 

Don,

In RX mode, relay K1 is not providing 12v to the TX power rail,
so transistors  Q911,Q912, Q92, Q93, Q96 and Q97 are not powered up.

I suggest you disconnect PA-PWR from your power supply so the IRF510 drains
are not getting power.  Then press PTT to put the rig in transmit mode
and measure those voltages for Evan.  That way the IRF510's won't be getting hot, 
and there is no need to put a dummy load on the antenna port.

Some parts of the driver amps might get warm if you hold down PTT too long,
I really don't know.
I'd let up on the PTT switch when not actually looking at the voltmeter.

Jerry


On Thu, Dec 12, 2019 at 07:20 PM, Don - KM4UDX wrote:
Evan - for testing the transistors, do I have the board in normal RX mode?

Re: V4 TX problems and new finals #ubitx-help

Don - KM4UDX
 

Evan - for testing the transistors, do I have the board in normal RX mode?

Re: V4 TX problems and new finals #ubitx-help

Evan Hand
 

Two ways to go forward at this time:

1 - Measure the bias voltages on the transistors
2 - Remove the transistors and do typical diode check on each junction

I would do the bias voltage checks.

You are concerned with Q911,Q912, Q92, Q93, Q96 and Q97.

When I measured the voltages relative to ground I got aproximatly 12.3 volts on Q911 and Q912 collectors, 1.13 on the base and .46 on the emitter.

For Q92, Q93, Q96 and Q97 I measured 11.4 volts on the collectors, 1.12 volts on the bases and .46 on the emitters.

See if any of these transistors have the wrong bias voltages.  That would indicate which ones to pull to test.

Note, the values are approximate.  The important value is the difference between the base and the emitter.  Should be around .7 volts.  Indicates it is conducting properly and not shorted or open.

Only real test that I know is to measure the RF voltages, That is why I use a 100 MHz oscilloscope. 

Try the above and let us know.

73
Evan
AC9TU

Re: V4 TX problems and new finals #ubitx-help

Don - KM4UDX
 

I may get a scope next week. Of course I have  no idea how to use it, but my guru (Dan, W3BU) has kindly agreed to some brief training.

I have a DVM and lots of stick-2-it-tivness.  So they are my tools for now!

Re: V4 TX problems and new finals #ubitx-help

Don - KM4UDX
 

Evan and Co.  I opened RV1 all the way and that gave me a small momentary deflection of power meter.  But essentially RV1 setting doesn't appear to be the problem. 

Here is a short vid of RV1 full open and clicking the CW jack.

https://photos.app.goo.gl/X8NDwuquHK65rHoXA

At least nothing really bad happens?

Re: V4 TX problems and new finals #ubitx-help

Don - KM4UDX
 

I checked the IRF510 traces per diagram -- red checks indicate continuity with appropriate PA pin.  Looks okay? I now see why a shorted Q94 made the rig short the power supply on TX -- the Source pin goes to ground, and it was shorted internally due to my Chernobyl event. 

Re: V4 TX problems and new finals #ubitx-help

Don - KM4UDX
 

I got IFR510 from someplace. I can't track the order history. But using a simple set of DVM-based tests they check out for on/off state. I know that says nothing about the actual performance on the circuit. 

BITX40 -- Sold

Jack, W8TEE
 

All:

The BITX40 is sold. Thanks for your interest.

Jack, W8TEE

--
Jack, W8TEE

Re: V4 TX problems and new finals #ubitx-help

Evan Hand
 

The fact that you could do the bias adjustment implies that K1 is working.  It also implies that both of the IRF510s are OK.  Either could be false, but not likely.

That leaves the drivers from Q90 on. 

To progress from here it would be best to know what test equipment you have on hand.  We will need to trace the signal from the base of Q90 to the gates of the finals.  I find that an oscilloscope works best for me (assuming it can measure the frequencies to be used.

I use the CW mode to test the drivers, as the signal is constant, and easier than doing the single or two tone for SSB. (getting input levels correct can be a hassle) 

I will assume that you have the schematic from HFSignals.

In another thread I posted the waveforms that I measured on the test points up to the finals.  I will look them up if youi have a scope.

73
Evan
AC9TU

Re: V4 TX problems and new finals #ubitx-help

Anthony Gomes
 

Let me try to help you OM with my limited knowledge which I have gained after building my homebrew ubitx based on V5. Disclaimer: I don't own any version of ready made build ubitx :)

My first question will be where you have sourced your replacement IRF510. If it's from reputed source like Digikey or mouser then you can start the troubleshooting or else check if those IRF510 are genuine one.

Since you have replaced both the K1 relay and the MOSFETS at the same time. Check if there is any contact issue with the replaced K1 relay. Since your receiver is working, are you still able to listen to the receiver when to press the CW key ?

As the receiver is working fine I would focus on things located beyond C80.

73
Anthony
VU3JVX

Re: V4 TX problems and new finals #ubitx-help

pat griffin
 

Check the connection between the traces and the 510s. Check continuity between the 510 pins and the trace not just at the hole. 
73
Aa4pg


On Dec 12, 2019, at 11:47 AM, Don - KM4UDX <dontAy155@...> wrote:

Hello all!  I failed to pay attention and left my beloved V4 uBIX on TX into a high SWR situation with too many watts for too long while and things got sort of too hot. Like Africa hot.

After I got Chernobyl cooled off, every time I hit TX the rig went to ground, so I figured the 510s had gone to heaven. 

And K1 had been sticking randomly for a while. So removed the old K1 relay and put in a new guy. I don't know how to test the new K1 beyond hitting TX and seeing what happens?

I then removed the old 510s, and watched a bunch of uTuber on MOSFET DVM testing.  After testing, one of the two olds were clearly " totally dead". 

So I replaced both - a first for me!  Then adjusted bias to get to 100mA delta on each. So all good.  When I now hit TX with the CW key (I think this is full audio drive into the TX section), the amp draw increase by about 1 amp -- which I think (?) is fine.

Only problem is I get no RF out. When I use the mic input I get the same behavior. No RF. Ditto when I use WSJT-X tune function which triggers the TX and send a big audio tone into the rig.  No RF.

RX is perfect.

What can I check, or what is the likely issue?  I could have messed up the PA repair, or the K1 repair, or something else got whacked in the Chernobyl event that I haven't figured out?
Or am I doing something moronically stupid (which is an actual possibility..just saying...).

And thanks for all for all the help.

<IMG_20191209_215240_01.jpg>

V4 TX problems and new finals #ubitx-help

Don - KM4UDX
 

Hello all!  I failed to pay attention and left my beloved V4 uBIX on TX into a high SWR situation with too many watts for too long while and things got sort of too hot. Like Africa hot.

After I got Chernobyl cooled off, every time I hit TX the rig went to ground, so I figured the 510s had gone to heaven. 

And K1 had been sticking randomly for a while. So removed the old K1 relay and put in a new guy. I don't know how to test the new K1 beyond hitting TX and seeing what happens?

I then removed the old 510s, and watched a bunch of uTuber on MOSFET DVM testing.  After testing, one of the two olds were clearly " totally dead". 

So I replaced both - a first for me!  Then adjusted bias to get to 100mA delta on each. So all good.  When I now hit TX with the CW key (I think this is full audio drive into the TX section), the amp draw increase by about 1 amp -- which I think (?) is fine.

Only problem is I get no RF out. When I use the mic input I get the same behavior. No RF. Ditto when I use WSJT-X tune function which triggers the TX and send a big audio tone into the rig.  No RF.

RX is perfect.

What can I check, or what is the likely issue?  I could have messed up the PA repair, or the K1 repair, or something else got whacked in the Chernobyl event that I haven't figured out?
Or am I doing something moronically stupid (which is an actual possibility..just saying...).

And thanks for all for all the help.



Re: µBITX & QRP labs 50W PA

Jerry Gaffke
 

Like all of the stuff Hans sells, the manual is exceptional.
Lots of notes in there about design tradeoffs made.
And a bunch about what it would take to make it linear.

Should have a way to evaluate IMD if you give linear operation a try.

Price is right.
Has a very nice solution for QSK TR switching.

Jerry

Re: µBITX & QRP labs 50W PA

MadRadioModder
 

Ah ok….

 

Well if it’s “Class C” it’s not gonna work for SSB.  The only way to change that is to bring it to at least “Class AB2”… by reducing the bias and allowing the device more resting current.  That generates a lot more heat (because the devices are conducting more of the time) so the cooling needs to be increased.   You can make it happen but it’s gonna take some work.

 

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of iz oos
Sent: Thursday, December 12, 2019 11:24 AM
To: BITX20@groups.io
Subject: Re: [BITX20] µBITX & QRP labs 50W PA

 

Nice to know. I don't think it can be used for SSB as it is a class C amp unless some mods are done. Looking forward to seeing Allison's reply

 

Il 12/dic/2019 17:49, "Arvo W0VRA via Groups.Io" <arvopl=yahoo.com@groups.io> ha scritto:

Anybody considering using a QRP Labs 50W PA with their µBITX?

http://qrp-labs.com/50wpa

There's no band switching yet.


--

…_. _._

BITX40 for sale...again...

Jack, W8TEE
 

I have a BITX40 for sale in its original shipping box for $50, with free shipping to CONUS.Write to me privately if you are interested using my email address on QRZ.com. PayPal only please!

Jack, W8TEE

--
Jack, W8TEE