Re: ?BITX & QRP labs 50W PA
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. ? ?
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From: [email protected] [mailto:[email protected]] On Behalf Of iz oos
Sent: Thursday, December 12, 2019 11:24 AM
To: [email protected]
Subject: Re: [BITX20] ?BITX & 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=[email protected]> ha scritto: Anybody considering using a QRP Labs 50W PA with their ?BITX?
There's no band switching yet.
-- ¡_. _._
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BITX40 for sale...again...
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
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Re: ?BITX & 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= [email protected]> ha scritto: Anybody considering using a QRP Labs 50W PA with their ?BITX?
There's no band switching yet.
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Re: ?BITX & QRP labs 50W PA
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
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Re: ?BITX & QRP labs 50W PA
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
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On Thu, Dec 12, 2019 at 08:49 AM, Arvo W0VRA wrote:
Anybody considering using a QRP Labs 50W PA with their ?BITX?
There's no band switching yet.
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Anybody considering using a QRP Labs 50W PA with their ?BITX?
There's no band switching yet.
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And solved issue for me, thanks for posting
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PE3ES - F4VTQ - Erwin
73
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Erwin I was meaning the power adapter for the active antenna not the uBITX.?
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On Dec 12, 2019, at 06:17, Erwin Serl¨¦ 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
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Re: My #ubitx build from scratch
#ubitx
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
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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.?
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.
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Re: Audio isolation w/ digital modes
#ubitx
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 Serl¨¦ via Groups.Io <waterwin2= [email protected]>:
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
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Re: My #ubitx build from scratch
#ubitx
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.
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Re: Audio isolation w/ digital modes
#ubitx
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.??
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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
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Re: My #ubitx build from scratch
#ubitx
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
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.
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.?
as you can see they are quite cheap and available on 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
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Re: My #ubitx build from scratch
#ubitx
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
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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.
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Re: Audio isolation w/ digital modes
#ubitx
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
|
Qrp pops has some really great stuff on active antennas
On Thu 12 Dec, 2019, 4:47 PM Erwin Serl¨¦ via Groups.Io, <waterwin2= [email protected]> wrote: Reversing the power would not make my uBITx work I think.
And it is working (still ;-)
--
PE3ES - F4VTQ - Erwin
73
|
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
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:
toggle quoted message
Show quoted text
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.
|
MadRadioModder
Arvo W0VRA
Skip Davis
Alan de G1FXB