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sbitx v3 circuit and performance details

 

I completed a comprehensive test of sbitx v3 using IRF510s and all the modifications and performance figures are in a document.
To put it in a nutshell, the IRF510 PA provides 25 watts upto 10 MHz, 20 Watts to 21 Mhz, and 10 watts on 28 MHz. The power chain is very resilient and useful even for other projects.
You can read the details on?
The complete circuit diagram?(it is same as v2 except for a few resistors) is on?

- f
 

I have included rf voltages at various points to make it easier for folks to troubleshoot the PA chain.
- f

On Sun, Nov 19, 2023, 6:20 PM Ashhar Farhan via <farhanbox=[email protected]> wrote:
I completed a comprehensive test of sbitx v3 using IRF510s and all the modifications and performance figures are in a document.
To put it in a nutshell, the IRF510 PA provides 25 watts upto 10 MHz, 20 Watts to 21 Mhz, and 10 watts on 28 MHz. The power chain is very resilient and useful even for other projects.
You can read the details on?
The complete circuit diagram?(it is same as v2 except for a few resistors) is on?

- f
 

Great work as usual.? ?Providing the VOLTAGES is a great step for folks experiencing "issues"
Congrats.

I think I will stick with the existing MOSFETS but I'll look into the transient suppressor you suggest.? ?Thanks!
Gordon KX4Z



On Sun, Nov 19, 2023 at 7:55?AM Ashhar Farhan <farhanbox@...> wrote:
I have included rf voltages at various points to make it easier for folks to troubleshoot the PA chain.
- f

On Sun, Nov 19, 2023, 6:20 PM Ashhar Farhan via <farhanbox=[email protected]> wrote:
I completed a comprehensive test of sbitx v3 using IRF510s and all the modifications and performance figures are in a document.
To put it in a nutshell, the IRF510 PA provides 25 watts upto 10 MHz, 20 Watts to 21 Mhz, and 10 watts on 28 MHz. The power chain is very resilient and useful even for other projects.
You can read the details on?
The complete circuit diagram?(it is same as v2 except for a few resistors) is on?

- f
 

Farhan,

Would there be any benefit to installing the Transient suppressor diodes if I choose to just keep my PA section using the IRFZ24N FETs?

Joel
N6ALT
 

Digikey has 134,000 of those diodes, and they are dirt cheap.? ?$0.64
 

Buy 10 and get them for $0.53 each!

Joel
N6ALT
 

Joel -- leave a few for me!!
Ashhar has found great solutions.? ? I'm sorry to see the power go down slightly, but I'm guessing the purity got even better.? ?This radio continues to improve!

I hope to box mine up when I get back home in several days.? ? I'll order the TVS diodes and add them later.? ? Make copies of my operating chip and start installing V3 software.

Gordon KX4Z


On Sun, Nov 19, 2023 at 2:50?PM Joel Caulkins/N6ALT <caulktel@...> wrote:
Buy 10 and get them for $0.53 each!

Joel
N6ALT

 

Joel,
I would highly recommend it. The maximum gate voltage of the IRFZ24N is half that of the IRF510s and it is more prone to breakdown.
- f


On Sun, Nov 19, 2023, 9:55 PM Joel Caulkins/N6ALT <caulktel@...> wrote:
Farhan,

Would there be any benefit to installing the Transient suppressor diodes if I choose to just keep my PA section using the IRFZ24N FETs?

Joel
N6ALT

Pierre FK8IH
 

Do I understand well? I do not yet own a sBitx but I'am very much interested in this development (using currently mainly a Hermes Lite 2 and a QDX Hi-Band).
If I want to use a sBitx I must buy a V2, make myself the modifications () and upgrade to V3 software?
One last question: in a near future will the sBitx sold by HF Signals be directly V3 hardware versions?
Congratulations for your work. I remember having followed the uBitx development and been amazed by the involvment of many Hams, bringing their own mods and improvements but after a lot of hesitations I finally decided I would run SDR and bought a Hermes Lite 2. The sBitx with its revolutionary concepts absolutely deserves my full attention.
73 - Pierre - FK8IH

?
 

Pierre,
The new production run will be v3. We expect the boards anytime soon, Diwali is a huge deal in India and our pick and place guy was shutdown for a week!
We will first start with v3 boards alone and then the full radio.
- f

On Mon, Nov 20, 2023, 7:06 AM Pierre FK8IH <jb.gallauziaux@...> wrote:

Do I understand well? I do not yet own a sBitx but I'am very much interested in this development (using currently mainly a Hermes Lite 2 and a QDX Hi-Band).
If I want to use a sBitx I must buy a V2, make myself the modifications () and upgrade to V3 software?
One last question: in a near future will the sBitx sold by HF Signals be directly V3 hardware versions?
Congratulations for your work. I remember having followed the uBitx development and been amazed by the involvment of many Hams, bringing their own mods and improvements but after a lot of hesitations I finally decided I would run SDR and bought a Hermes Lite 2. The sBitx with its revolutionary concepts absolutely deserves my full attention.
73 - Pierre - FK8IH

?
 

Joel,
I bought CDSOD323-T03C diodes in connection with building another sdr.
The Minimum Breakdown Voltage of this diode is 4.0V.
As Ashhar recommended in message #106236, this is just right for the IRFZ24.
--
Gyula HA3HZ
 

Hi Gyula,

I kind of figured that and already ordered me 10 of them, I can install them on both my DE and V2. I really look forward to the V3 software next.

Joel
N6ALT
 

Hi Joel,
If you want to try v3 like Evan did on his modified DE, you can easily do that.
It is described in one of the messages of 'v3 software, alpha is here'.
--
Gyula HA3HZ
 

Put me down please for a V3 (h/w version) Richie 4Z4DR
 

On Sun, Nov 19, 2023 at 05:20 PM, Ashhar Farhan wrote:
would highly recommend it. The maximum gate voltage of the IRFZ24N is half that of the IRF510s and it is more prone to breakdown.
None of the datasheets for the IRFZ24 confirms that.? Its the same for all of the class
of mosfets being typical at 20V,? most will be fully saturated at 10V.

Allowing for the device Gfs more than a few volts gate to source (plus DC bias ) will be
well under 5V.

The IRF510 is not any different.? The difference? are the max current and higher Rds-ON .
The latter is not a factor for linear operation, only saturated switching.? That and
total power.? ?But the IRF510 has a far lower Gate to source capacitance making
for higher driving impedance.? Additionally a far lower Crss at 20pf wher the
IRFz24 is 65pf.? That Miller capacitance makes the latter harder to drive and?
resulting in lower input impedance.


--
Allison
------------------
Please use the forum, offline and private will go to bit bucket.
 

The big problem case is that the IRFz24 is a 55V (DS) device and the IRF510 is a 100V part.

At the 100V level the IRF520 is a 10A device with 100V DS max making it a more robust
at the cost of higher input and output capacitance making driving it and matching it
somewhat more difficult but generally better than the IRFZ24.

--
Allison
------------------
Please use the forum, offline and private will go to bit bucket.
 

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Allison, even with infinite swr, can more than 28 volts reach one of the mosfet finals??

Gordon Kx4z?


On Nov 20, 2023, at 14:42, ajparent1/kb1gmx <kb1gmx@...> wrote:

?The big problem case is that the IRFz24 is a 55V (DS) device and the IRF510 is a 100V part.

At the 100V level the IRF520 is a 10A device with 100V DS max making it a more robust
at the cost of higher input and output capacitance making driving it and matching it
somewhat more difficult but generally better than the IRFZ24.

--
Allison
------------------
Please use the forum, offline and private will go to bit bucket.

 

maybe depending on the specific load.
And 28V is way below the tolerance for the mosfet.

IRF510 a is a 100V part and the IRFZ24 is a 55 volt part.

Generally its reasonable to keep the drain voltage below that.

That has little to do with gate voltage as that is only from the divers.
Id expect that to be well under 10V P-P at the gates.

--
Allison
------------------
Please use the forum, offline and private will go to bit bucket.
 

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I found an article that discusses vswr testing. ?While I think the fundamental can only ?induce twice it’s voltage (by 100% reflection) I forgot there are harmonics to think about also!?

The author suggests that 2.5 times the drain voltage DC is a reasonable maximum to expect



If that’s true, then our 55 or 60 V devices should be fine.?

Gordon Kx4z?





On Nov 20, 2023, at 19:38, ajparent1/kb1gmx <kb1gmx@...> wrote:

?maybe depending on the specific load.
And 28V is way below the tolerance for the mosfet.

IRF510 a is a 100V part and the IRFZ24 is a 55 volt part.

Generally its reasonable to keep the drain voltage below that.

That has little to do with gate voltage as that is only from the divers.
Id expect that to be well under 10V P-P at the gates.

--
Allison
------------------
Please use the forum, offline and private will go to bit bucket.

 

Gordon,

That is true...? save for there is a transformer between the transmission line and the Drains.
If its 1:4 (impedance) step up going out it will work the opposite ways for the return
signal for a total return loss.? So the voltage is 1/2. (sqrt(4)).? Its greater for a
1:9 (1:3 turns) case.

Still I've used 3x to 4x as a safety margin.? The 100V irf510 is fairly resistant at 24V
and less so at 32.? For nominal 12V (13.8V DC) that means 55-60V device has
enough voltage margin.

However blowing devices is often a symptom of other things going on such
as RF instability or DC instability.

--
Allison
------------------
Please use the forum, offline and private will go to bit bucket.

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