Date   
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

Re: µBITX & QRP labs 50W PA

iz oos
 

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.

Re: µBITX & QRP labs 50W PA

MadRadioModder
 

Single band

 

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of Arvo W0VRA via Groups.Io
Sent: Thursday, December 12, 2019 10:50 AM
To: BITX20@groups.io
Subject: [BITX20] µBITX & QRP labs 50W PA

 

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

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

There's no band switching yet.


--

…_. _._

Re: µBITX & QRP labs 50W PA

Jerry Gaffke
 

Ok, I sort of take that back.

The webpage also says:

######################################

2. Can it be used as a Linear for SSB and other modes? 

NOT SSB as it is - it is designed as a Class-C amplifier, for CW operation (or FSK modes). Single Sideband (SSB) requires a Linear. If you want to experiment using this amplifier as a Linear, you can try setting the bias trimmer potentiometer to achieve a higher "idle" current during transmit, of around 250mA. This will dissipate some watts of heat even when there is no signal, and is normal for Linears. The efficiency will also be lower. Accordingly, heat dissipation may be higher too (depending on the average power output and other factors). So proceed with caution if you want to modify the amplifier for LINEAR operation - you will be in experimental territory. 

.......

6. Could it be modified for multi-band operation? 

 

Certainly. Just bypass the Low Pass Filter section of the design, and use an external switched Low Pass Filter for the bands of interest. There are no other band-specific components except for the Low Pass Filter components and it will work across all HF. As usual... everything gets harder at higher frequencies so expect the power output to start to fall off (see also the measurements section of the manual). 

##################################################



So multiband should be possible with just an appropriate LPF as a lump in your antenna feed line.
I would guess you will have to adjust the drive into the amp whenever you switch bands, the upper bands will require more drive.

As he says, linear operation for SSB might be possible but is not designed in.
You're on your own.

Jerry

Re: µBITX & QRP labs 50W PA

Jerry Gaffke
 

That's a class C amp.
As it says on the web page you pointed to:
>    This amplifier is not intended to be a Linear (for SSB use) - it is designed for single-band CW operation only. 

Jerry


On Thu, Dec 12, 2019 at 08:49 AM, Arvo W0VRA wrote:
Anybody considering using a QRP Labs 50W PA with their µBITX?

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

There's no band switching yet.

µBITX & QRP labs 50W PA

Arvo W0VRA
 

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

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

There's no band switching yet.

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

Erwin Serlé
 

And solved issue for me, thanks for posting
--
PE3ES - F4VTQ - Erwin
73

Re: Active antenna into uBITx V5 gives some smoke on the coax #ubitx #v5 #antennas

Skip Davis
 

Erwin I was meaning the power adapter for the active antenna not the uBITX. 

Skip Davis, NC9O

On Dec 12, 2019, at 06:17, Erwin Serlé via Groups.Io <waterwin2@...> wrote:

Reversing the power would not make my uBITx work I think.
And it is working (still ;-)
--
PE3ES - F4VTQ - Erwin
73

Re: My #ubitx build from scratch #ubitx

Jerry Gaffke
 

Anthony,

Thanks for letting us know about the spot weld cutter drill bit.
Looks ideal, perhaps the easiest way to prototype a circuit. 

The almost solid ground plane on the top side is good enough in most cases.
For a radio, especially in critical sections, I might drill a bunch of holes through the board,
then solder wire into those holes to connect the top and bottom ground planes.
Can't have too good of a ground when dealing with large gains and several watts of RF.

Jerry, KE7ER


On Wed, Dec 11, 2019 at 11:15 PM, Anthony Gomes wrote:
What you said " I'd first try taking an angle grinder with a cutoff disk to an old drill bit, leaving the center and a "wing" on each side " this does work but I found a better tool which does the work very easy and clean way. https://www.banggood.in/38-or-516-Inch-HSS-Double-Sided-Rotary-Spot-Weld-Cutter-Drill-Bit-Welds-Remover-Tool-p-1496043.html?rmmds=search&ID=516896&cur_warehouse=CN
as you can see they are quite cheap and available on amazon.com also, you don't need to get the best as we are not going to use it for spot welding so even the cheap one will cut like butter on copper board, good thing is that you can change the side of the cutter which you will hardly require.

Re: Audio isolation w/ digital modes #ubitx

Jonas Sanamon
 

Hi Erwin,

Did You perhaps use a linear potentiometer instead of a logarithmic ?   That can cause the effect of the volume id very sensitive at one end of the scale.

Best Regards,
Jonas - SM4VEY


Den tors 12 dec. 2019 kl 12:31 skrev Erwin Serlé via Groups.Io <waterwin2=yahoo.com@groups.io>:

Hi Arvo,

I have something like it on a ugly build uBITx V5. It is very difficult to control the volume of Audio Out. Very sensitive at the beginning of the volume knob. Did you (or somebody else) think of making gears for that knob 1 : 10 or so for better handling. Or install an extra resistor in series or so?

The volume should be very low as to not overdriving the pc soundcard/external sound card.
--
PE3ES - F4VTQ - Erwin
73

Re: My #ubitx build from scratch #ubitx

Anthony Gomes
 

QRPme style pads created using the bits as shown in the picture (attached incorrect picture in my previous post). I would recommend using the 3/8 inch bit to cut the pads and using the 5/16 inch to cut the island with a hand drill (if you have a cordless even better). Usually they sell it as set of 2 bits (3/8 inch & 5/16 inch) easy to get in your local shop/online. Hope then don't run out of stock after the discussion on this forum :)



From my personal experience I can say with this tool you can lay down any schematic in matter of no time. I have even build a FT8 digital interface in no time for my Yeasu FT-450D. I was even able to fix the relay in correct orientation after bending the pins side ways but I won't recommend doing so with IC's and hence you can see the vero board build in the in the middle of my ubitx build as I have used TDA2822 for audio and the circuit was simple one.

Re: Audio isolation w/ digital modes #ubitx

W4MWD
 

The potentiometers provided with the case kits and maybe even for the board kits are both linear.   For audio volume control purposes, an audio taper will provide the logarithmic progression necessary for the human ear's response curve.  Sounds like this could be your problem with sensitivity at the beginning of the control.  Try replacing the control with an audio taper control.  

Re: STM32F769-FT8-Transceiver

 

My FT8 system is working, thanks to Charley's help! 
There was a connection discrepancy in my wiring! 
Now I have to mount everything into a functional case.
Photos later.
Your mileage may vary,
Jim

Re: My #ubitx build from scratch #ubitx

Anthony Gomes
 

One more thing I should have mentioned. If you use those "Spot welding" bits and cut it through the board you can create your own 5/16 inch tiny pads in no time out of some scrap PCB.

Anthony
VU3JVX

On Thu, 12 Dec 2019, 14:01 Ian Reeve, <ian.radioworkshop@...> wrote:
In the UK the GQRP club sell a pcb island cutter.Using a drill preferably in a drill press this tool isolates a circular island of copper from the rest of the pcb.circuits can be built using this design,components fixed between islands. Years ago I had a set of stick in copper islands,squares,oblongs etc which could be stuck as desired.No longer made but so useful.


From: BITX20@groups.io <BITX20@groups.io> on behalf of vu3jvx@... <vu3jvx@...>
Sent: Thursday, December 12, 2019 7:15:13 AM
To: BITX20@groups.io <BITX20@groups.io>
Subject: Re: [BITX20] My #ubitx build from scratch
 
Thank you Jerry. You always ask the questions which matters and that's what I like about you. Because of this I never felt like asking any question on this forum while building the ubitx, people can get 99% answers to their queries if they do a search on this forum.

Coming back to your questions:
Yes, I thought of sharing the island cutter process which I did. Most of the time I use to give up on any DIY project looking at the schematic unless the PCB was available as a kit and I can completely understand why members on this forum look for PCB gerber file to build ubitx. Yes, I have those hole saw bit as you have mentioned but using those bits without drill press is impossible even with a drill press it slip over copper board and I don't have any drill press so i made a wrong choice.

What you said " I'd first try taking an angle grinder with a cutoff disk to an old drill bit, leaving the center and a "wing" on each side " this does work but I found a better tool which does the work very easy and clean way. https://www.banggood.in/38-or-516-Inch-HSS-Double-Sided-Rotary-Spot-Weld-Cutter-Drill-Bit-Welds-Remover-Tool-p-1496043.html?rmmds=search&ID=516896&cur_warehouse=CN
as you can see they are quite cheap and available on amazon.com also, you don't need to get the best as we are not going to use it for spot welding so even the cheap one will cut like butter on copper board, good thing is that you can change the side of the cutter which you will hardly require.

I use the 5/16 inch bit to cut the island with a hand drill, it's so easy that I even did the process in middle of the build (not recommended as the copper dust can bridge the island) when I thought that I missed to cut an island. The trick is that the center pin is spring loaded so you should get a good hold of it before you start cutting the island and since the center pin is spring loaded it will not not make any hole at the center of the island. I believe all those extra ground plane around the island does help the RF signals if I remember correctly those basic fundamentals of RF signals.

Regarding the crystal I made a simple jig to sort out from bunch 11.059 Mhz crystal and keep them within 100Hz as done in ubitx factory. It worked without making any crystal change except the 12Mhz as mentioned on my original post.

As it is unfortunate that they make fake IRF510. Maybe it is not detected while it is used for their primary application (switching motor drivers as they say :) ), but when we use the fake IRF510 for RF work we take a hit immediately. One thing I have observed while working with the fake IRF510 is that if you increase the Drain voltage (PA PWR) to 28V then you get more RF output which you should have got at 12V using original IRF510 (others mileage may vary).

Attaching the test picture of my original IRF510 using cheap component tester, the fake one was showing 600+ pf. Hope that will help others, it will be interesting to know about others findings also. I believe awareness about original IRF510 will help the home brewers avoid frustrating moment while building or troubleshooting their ubitx.



Anthony
VU3JVX

Re: My #ubitx build from scratch #ubitx

Ian Reeve
 

Hi Alan,  I have not checked my latest qrp sprat magazine is expected soon.The pcb cutters are very popular and last well.Using a small multipurpose drill at medium speed you get perfect results.The pads and squares you mention must be the modern equivalent of the ones I have which are at least 10 years old and came in assorted sizes in a plastic tray with dividers and teasers to facilitate handling.Many many happy hours constructing using these and island or pad cutters. 73. Ian M0IDR


From: BITX20@groups.io <BITX20@groups.io> on behalf of Alan de G1FXB <g1fxb.groups@...>
Sent: Thursday, December 12, 2019 11:09:13 AM
To: BITX20@groups.io <BITX20@groups.io>
Subject: Re: [BITX20] My #ubitx build from scratch
 
Ian,
I think they were (temporary) out of stock, MePads & MeSquares are currently listed on the club sales pdf
Have you tried recently?

Alan

On 12/12/2019 08:30, Ian Reeve wrote:
In the UK the GQRP club sell a pcb island cutter.Using a drill preferably in a drill press this tool isolates a circular island of copper from the rest of the pcb.circuits can be built using this design,components fixed between islands. Years ago I had a set of stick in copper islands,squares,oblongs etc which could be stuck as desired.No longer made but so useful.



Re: Audio isolation w/ digital modes #ubitx

Erwin Serlé
 

Hi Arvo,

I have something like it on a ugly build uBITx V5. It is very difficult to control the volume of Audio Out. Very sensitive at the beginning of the volume knob. Did you (or somebody else) think of making gears for that knob 1 : 10 or so for better handling. Or install an extra resistor in series or so?

The volume should be very low as to not overdriving the pc soundcard/external sound card.
--
PE3ES - F4VTQ - Erwin
73

Re: Active antenna into uBITx V5 gives some smoke on the coax #ubitx #v5 #antennas

Ashhar Farhan
 

Qrp pops has some really great stuff on active antennas


On Thu 12 Dec, 2019, 4:47 PM Erwin Serlé via Groups.Io, <waterwin2=yahoo.com@groups.io> wrote:
Reversing the power would not make my uBITx work I think.
And it is working (still ;-)
--
PE3ES - F4VTQ - Erwin
73