Hi Michael,
?
Start by checking if the tab (drain) of Q9 switches between 0 and almost the input voltage (12).? Q9 provides the power to the driver and bias stages.
?
If the Q9 drain is not changing, verify that the TX signal (gate of Q10) changes between 0.6 volts and 3.3 volts.? That is the transmit signal from the Raspberry Pi.
?
Once you get the TR switching working, then verify the voltages on the transistor sides of R10 and R49.? R10 will indicate that the predriver Q11 is at its operating point.? R49 voltage indicates that the four drivers are at their operating point.
?
Once all the driver stages are verified to be at the operating point, switch to the RF probe sheet, CW mode, and the power settings to trace with the probe.
?
Good Luck, and happy hunting for the problems.
73
Evan
AC9TU
|
Also, I don't have voltage to any of the lpf switching diodes.?
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-------- Original message --------
From: "Michael Bales via groups.io" <mikebales73@...>
Date: 3/4/25 9:15 PM (GMT-05:00)
Subject: Re: [BITX20] reviving my sbitx v3
So I have made some mistake somewhere because I have .9v on the gate of Q9 and that voltage is on the base of the 2n2219s and the gate of Q11 and gate and drain of Q101, the bias adjust can vary this up to about 2v.?
-------- Original message --------
From: "Evan Hand via groups.io" <elhandjr@...>
Date: 3/4/25 8:23 PM (GMT-05:00)
Subject: Re: [BITX20] reviving my sbitx v3
Michael,
?
I put together this spreadsheet with voltage measurements of the PA section.? It requires a DMM and an RF probe.
?
Let me know if this helps.
?
73
Evan
AC9TU
--
Mike - K8MCB?
-- Mike - K8MCB?
|
So I have made some mistake somewhere because I have .9v on the gate of Q9 and that voltage is on the base of the 2n2219s and the gate of Q11 and gate and drain of Q101, the bias adjust can vary this up to about 2v.?
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-------- Original message --------
From: "Evan Hand via groups.io" <elhandjr@...>
Date: 3/4/25 8:23 PM (GMT-05:00)
Subject: Re: [BITX20] reviving my sbitx v3
Michael,
?
I put together this spreadsheet with voltage measurements of the PA section.? It requires a DMM and an RF probe.
?
Let me know if this helps.
?
73
Evan
AC9TU
-- Mike - K8MCB?
|
Homebrew satellite control system that can run on sBitx
Hi!
?
More work following the path that Ashhar suggested.? ?I have also bought an older Icom 810H that has full duplex VHF/UHF.
I'm doing initial experiments on Windows PC, but I have already demonstrated full Doppler shift control of sBitx acting as the 10m transceiver to a transverter, so this can all move to the sBitx....
?
?
GPREDICT re-installed due to better location, tracking any satellite I like.? Does all the trig and doppler MATH
RIGCTLD - previously studied and working; receives tcp/ip commands from GPREDIT? to do doppler shift adjustments of sBitx or Icom radio
?
Today:
ROTCTLD -- figured out how to run this on a windows machine.? ?Receives trig output of GPREDICT.? ?Converts (in this case) to Yaesu type rotator commands for Az/ elevation and sends out serial port (in my case, COM4, 9600 baud)
?
K3NG Rotator Controller -- I havent made a board for this yet.? ?So I took one of my homebrew WINKEYER ARDUINO simulators, and reprogrammed it using K3NG code to "act like" the controller, handling Az, El controls, reading the CW speed control as if it were an azimuth potentiometer; running the display and activating the "key" and "PTT" to rotate clockwise or counterclockwise.
?
The reprogramming of my Winkeyer Arduino appeard to be a huge success.? ?I properly set the pins to run the display, which worked FINE.
It was reading the speed pot as an azimuth reading, and if I pushed "buttons" it would read different elevations.
?
ROTCLD happily connected to it at 9600 baud, and the "rotator controller" accepted commands and displayed them.? ?I was not able on the first test to monitor whether it activated simulated motor controls (key output, etc) -- but that will come.? ??
?
So huge success here and soon (days, weeks?)? I should be able to lay out a board (many others have done so before me, but some just did crazy wiring between variuous "shields")? ?to put all this in a neat little package with relay outputs, possibly with PWM output (dunno)., to control available rotators for real.??
?
73
Gordon KX4Z
?
?
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Yes, thank you, the dc point voltages will at least give me an idea of where to look. If I can find out what is happening there, I will move to the rf measurements. Much appreciated!
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-------- Original message --------
From: "Evan Hand via groups.io" <elhandjr@...>
Date: 3/4/25 8:23 PM (GMT-05:00)
Subject: Re: [BITX20] reviving my sbitx v3
Michael,
?
I put together this spreadsheet with voltage measurements of the PA section.? It requires a DMM and an RF probe.
?
Let me know if this helps.
?
73
Evan
AC9TU
-- Mike - K8MCB?
|
Yep, now you're going to have to sniff out SIGNALS.? ?Welcome to the world of advanced radio repair (FCC Part 97.1 extraordinaire!)
gordon?
Michael,
?
I put together this spreadsheet with voltage measurements of the PA section.? It requires a DMM and an RF probe.
?
Let me know if this helps.
?
73
Evan
AC9TU
|
Michael,
?
I put together this spreadsheet with voltage measurements of the PA section.? It requires a DMM and an RF probe.
?
Let me know if this helps.
?
73
Evan
AC9TU
|
So, after replacing the power components of the PA section, and putting in a fresh pair of 510s, I put it all together, all is OK, except, ZERO output... At this point I'm running out of places to look. I have power to the finals, no heating
up, of anything. Wondering where the disconnect is now. Suggestions?
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-------- Original message --------
From: Michael Bales <mikebales73@...>
Date: 3/2/25 12:36 PM (GMT-05:00)
Subject: Re: [BITX20] reviving my sbitx v3
Yes! An ounce of prevention....
Well, who knows how it got damaged. Don’t forget to put D7 back in there, and it wouldn’t hurt to put something even a little beefier like two or three of the one amp diode in parallel.
This is fantastic that you’ve been able to figure this out
There are lots of different systems out there for polarity protection, use whatever you like.
Gordon kx4z?
On Mar 2, 2025, at 12:26, JJ - W9JES via groups.io <jj@...> wrote:
?
You can buy one prebuilt. ?
-- Mike - K8MCB?
|
Re: uBitxV6 -by transmitting resets-
Hi Ted,
?
One thing to remember is the difference in display current requirements.? The V6 is a touch screen with graphics capability, while the V5 is a 16x2 text display.?
?
Also, note that the v6 Raduino already has a heatsink on it.
?
I would be careful with the 10-ohm resistor.? If you use that on a v6, you may drop below the minimum input voltage for the 7805 (approx 7 volts).? This will depend on the supplied voltage.? Assume a 10-ohm resistor will drop the voltage by 10 volts at peak load.? A better value for 14 volts would be a 6 or 7-ohm resistor.? The resistor should have a 10-watt rating.? A more reasonable choice would be a 5-watt 5-ohm resistor or five 1-amp diodes.
?
73
Evan
AC9TU
|
Re: uBitxV6 -by transmitting resets-
I've been shouted down about using diodes in this way on other forums, but I still thing it is an easy solution to a potential problem, and it has the added advantage of preventing reverse polarity accidents in some situations.
Gordon and Ted are right; inline diodes do not produce noise unlike some other regulators. They are also ham-price-friendly AKA CHEAP! Daisy chain 5 and you are placing ~10-11 volts instead of 13.8 on the front end of that 7805, so it only has to deal with 60-70% (math done in my head) of the heat dissipation for a given current.
73 de Lee KX4TT
On Tuesday, March 4, 2025 at 12:17:08 PM EST, Ted via groups.io <k3rta@...> wrote:
Hello, Pieter.
?
I gather from commentary so far, that your 7805 is overheating from having to regulate down from 13.8 (down to 5v).? I don't have that problem and it may simply be that I have a heat sink on that regulator but I also have (what I believe is) a 10-ohm resistor in line with the B+ supply to the 7805. Thus, the ideas presented above to add diodes to the input of this regulator has merit. Dropping about 0.6v X 3 might help your regulator work less than it done at present.? As diodes are fairly cheap, use 4 if you like, even 5.?
?
I've got a few of the other form of voltage regulators and have yet to substitute one for the 7805 - though I've experimented for the radio supply itself and noticed no added RF noise.?
?
?
72,
?
Ted
K3RTA
?
?
|
Re: uBitxV6 -by transmitting resets-
Hello, Pieter.
?
I'm new to this discussion but not new to the MicroBITX.? I run a version 5 radio on a 16v internal battery bank - two sets of four, with a battery-management board in place.? This yields over 15 watts output on 40m CW, around 10w on 20m & 15m, and about 5w on 12/10m.
?
I gather from commentary so far, that your 7805 is overheating from having to regulate down from 13.8 (down to 5v).? I don't have that problem and it may simply be that I have a heat sink on that regulator but I also have (what I believe is) a 10-ohm resistor in line with the B+ supply to the 7805. Thus, the ideas presented above to add diodes to the input of this regulator has merit. Dropping about 0.6v X 3 might help your regulator work less than it done at present.? As diodes are fairly cheap, use 4 if you like, even 5.?
?
I've got a few of the and have yet to substitute one for the 7805 - though I've experimented for the radio supply itself and noticed no added RF noise.?
?
?
72,
?
Ted
K3RTA
?
?
?
?
?
?
|
Tom,
?
I've sent you an email.? I'm responding here so other people don't argue with my place in line.
?
Cheers,
Harris Butler, NN0Y
|
|
|
|
|
May i ask what resolved the low output on 20m what was it before and where is it now. Mine is also sluggish there at 13 watts while 40 is 22 watts. I expect it to be lower but??
Thank you?
--
Patrick?
|
?
Selling my sBitx V2 serial no. 0251. I assembled it, made a few ft8 and cw contacts, updated to 64-bit, #D printed a cover that allows for connection of mini HDMI cable to PI for extended display. Works great plugged into a 48" 1080P display (see pics on QRZ swapmeet). Was fun to play with, but now just sits.? Still has protective film on the screen and I installed Anderson power poles on the power cable. Includes everything that came in the box.
- Fully assembled and tested sBitx-v2 with the Raspberry 4 updated to 64-bit sBitx image.
- 7 inch capactive display
- 32 GB SD card installed with software
- XT60 power cable with power poles.
- Microphone
$275 shipped USPS Ground to lower 48 Cash in person or PayPal. ?
Also posted on QRZ, search my callsign for pictures.
|
Absolutely! I definitely am down for a kit. I'll reach out Thurs. I'm glad you caught me on this. I love Farhans ideas, But like you mentioned, it makes no sense to me why you wouldn't go the route of a MUCH needed sturdier PA section.
73
K8MCB
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Well thats the very reason i designed that little gem. ?It works without gain sag to 54 MHz… and you can short out or open the output 24/7 with no issues other than generating some heat. ?I gave Farhan a free board last FDIM but
he seemingly isnt interested in such robust designs. ?In any case just email me Thursday if you want a semi-kit (returning from my contest station J62K currently).
Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ
?
Owner - Operator
Big Signal Ranch – K9ZC
Staunton, Illinois
?
Owner – Operator
Villa Grand Piton - J68HZ
Soufriere, St. Lucia W.I.
Rent it: www.VillaGrandPiton.com
email:?
bill@...
?
On Mar 3, 2025, at 8:02?PM, Michael Bales via groups.io <mikebales73@...> wrote:
?
Yes, I understand trying to keep the cost of components down, but after further research, and my own experiences with a few bitx products, why keep chasing down a design around a MOSFET not intended for RF and spend a few more dollars on something like the
RD16HFF1, and be rid of the seemingly constant PA problems....
Yeah i bobbed the PAs out of all my BIT radios and use that 20W pa. ? Its got great specs and the semi-kit only cost about $20 plus shipping.?
Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ
?
Owner - Operator
Big Signal Ranch – K9ZC
Staunton, Illinois
?
Owner – Operator
Villa Grand Piton - J68HZ
Soufriere, St. Lucia W.I.
Rent it: www.VillaGrandPiton.com
email:?
bill@...
?
On Mar 3, 2025, at 11:37?AM, Evan Hand via groups.io <elhandjr@...> wrote:
?
Hi Mike,
?
Have you looked at the K9HZ amp that is part of the T41 project?
?
or
?
This might meet your needs.
?
You could couple it with the LPF and T/R switch the sBitx uses.
?
73
Evan
AC9TU
--
Mike - K8MCB?
-- Mike - K8MCB?
|
Well thats the very reason i designed that little gem. ?It works without gain sag to 54 MHz… and you can short out or open the output 24/7 with no issues other than generating some heat. ?I gave Farhan a free board last FDIM but he seemingly isnt interested in such robust designs. ?In any case just email me Thursday if you want a semi-kit (returning from my contest station J62K currently).
Dr.?William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ ? Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois ? Owner – Operator Villa Grand Piton - J68HZ Soufriere, St. Lucia W.I. Rent it: www.VillaGrandPiton.com
email:??bill@... ?
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On Mar 3, 2025, at 8:02?PM, Michael Bales via groups.io <mikebales73@...> wrote:
?
Yes, I understand trying to keep the cost of components down, but after further research, and my own experiences with a few bitx products, why keep chasing down a design around a MOSFET not intended for RF and spend a few more dollars on something like the
RD16HFF1, and be rid of the seemingly constant PA problems....
Yeah i bobbed the PAs out of all my BIT radios and use that 20W pa. ? Its got great specs and the semi-kit only cost about $20 plus shipping.?
Dr.?William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ
?
Owner - Operator
Big Signal Ranch – K9ZC
Staunton, Illinois
?
Owner – Operator
Villa Grand Piton - J68HZ
Soufriere, St. Lucia W.I.
Rent it: www.VillaGrandPiton.com
email:??bill@...
?
On Mar 3, 2025, at 11:37?AM, Evan Hand via groups.io <elhandjr@...> wrote:
?
Hi Mike,
?
Have you looked at the K9HZ amp that is part of the T41 project?
?
or
?
This might meet your needs.
?
You could couple it with the LPF and T/R switch the sBitx uses.
?
73
Evan
AC9TU
-- Mike - K8MCB?
|
The diode solution won’t make any noise either! Those switching systems might make noise!!?
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On Mar 3, 2025, at 20:14, WK4DS via groups.io <georgiaphotog@...> wrote:
? Simpler and less efficient?was would be to solder some 6A10 rectifier diodes in series till you get the voltage down to what you need. I have used this in the past and it works. I am sure there are better options out there, but if you have diodes and time, this will work. A LM317 and a simple circuit around?it would probably be better, but most likey?cost more too. A bag of the 6A10 diodes are one 6 or 7$ on Amazon...
David
Hello, we haven't received any zBitx yet and I'm already thinking about modifying something.
I don't really like the fact that it goes to a maximum of 9v, and I would like to know how to modify the device to make it work at 13,8vdc like the rest of the radio devices that most of us have.
I've looked at some components in the sBitx schematic and I think they are basically the same. So, what changes? I don't want to get more power (it wouldn't be bad to get 20w ;-) ) but I want to be able to have access to all the power sources I have.
thanks... I'm anxiously awaiting my shipment from India...
Jordi
From Catalonia.
|
Simpler and less efficient?was would be to solder some 6A10 rectifier diodes in series till you get the voltage down to what you need. I have used this in the past and it works. I am sure there are better options out there, but if you have diodes and time, this will work. A LM317 and a simple circuit around?it would probably be better, but most likey?cost more too. A bag of the 6A10 diodes are one 6 or 7$ on Amazon...
David
Hello, we haven't received any zBitx yet and I'm already thinking about modifying something.
I don't really like the fact that it goes to a maximum of 9v, and I would like to know how to modify the device to make it work at 13,8vdc like the rest of the radio devices that most of us have.
I've looked at some components in the sBitx schematic and I think they are basically the same. So, what changes? I don't want to get more power (it wouldn't be bad to get 20w ;-) ) but I want to be able to have access to all the power sources I have.
thanks... I'm anxiously awaiting my shipment from India...
Jordi
From Catalonia.
|
Lee
Ted
K9HZ
WK4DS