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Re: Smoking Genie

M Garza
 

Hi John,
It is a double sided board.
I would just remove the resistor and put in a 1/2 watt in its place.? Also, check the transistor (Q14) to make sure it didnt sacrifice itself also.

Good luck

Marco - KG5PRT

On Thu, Feb 15, 2018 at 4:02 PM, John 2e0eii <2e0eii@...> wrote:
Hi Guys

can you give me some help i have popped R141 ,whilst working a station near Inverness who gave me 5/8/9 ,

Then Smoke !! luckily R141 let go ,

I would like to replace with a bigger value Resister by drilling 2 holes through the board to support the Resister with solder..

My question is : is the b40 board single or double printed circuit, my unit is shoehorned into its cabinet i don't want to pull it all out to find out ,

and don't want to do any more damage,

--
Regards John 2E0Eii
Smoking Genie

 

Hi Guys

can you give me some help i have popped R141 ,whilst working a station near Inverness who gave me 5/8/9 ,

Then Smoke !! luckily R141 let go ,

I would like to replace with a bigger value Resister by drilling 2 holes through the board to support the Resister with solder..

My question is : is the b40 board single or double printed circuit, my unit is shoehorned into its cabinet i don't want to pull it all out to find out ,

and don't want to do any more damage,

--
Regards John 2E0Eii
Re: uBITX AGC - Adafruit TPA2016, A Success! #ubitx

August Treubig
 

Nick,
Did you ever post the sketch for the TPA2016 AGC?

Aug
AG5AT
Re: RD16HHF1 in the uBITX #ubitx

John
 

Thank you all for your kind words and valuable feedback.

I will then leave the idle PA current near 500mA per device despite the current drain.

I have contemplated adding some series capacitor/resistors in parallel to the emitter resistors in the driving stage or pre-driving stage either at R911/R941/R942/R96 or R87/R88 to increase the gain in the upper frequencies.

If someone with an oscilloscope could determine where the saturation occurs along the chain after RV1 when this pot is turned up, it would help decide where to put the frequency compensation.

But based on data on the web and this group's feedback it seems that extracting 16 to 20W from a pair of RD16HHF1s at 13.8V is pretty much it, so the uBitx design with 13.5W out is not that sub-optimal from that regard when we substitute the finals IMHO.

I have an SSM2167 board on order hoping that the compression will deliver the 3 to 6dB average power gain we seem to see with good compressors. I think it beats doubling or quadrupling the power on SSB, especially with a flatter power curve like the one I got.

Happy hacking.

All the best,

73, John (VK2ETA)
Re: RD16HHF1 in the uBITX #ubitx

 

¿ªÔÆÌåÓý

Well if you look closely there is some reactance at high frequency in the gate circuit to compensate for high capacitance loading at higher frequency. ?Thats a real tight rope to walk though because making that broad-banded is a real trick.?


Dr.?William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

?

Owner - Operator

Big Signal Ranch ¨C K9ZC

Staunton, Illinois

?

Owner ¨C Operator

Villa Grand Piton - J68HZ

Soufriere, St. Lucia W.I.

Rent it:


email:??bill@...

?


On Feb 15, 2018, at 2:02 PM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:

The WA2EBY amp has also been simulated, including notes on what those inductor values are:
? ??/g/BITX20/message/41269

Somehow WA2EBY managed to get good performance without any switching or tuning when changing bands.

Jerry

On Thu, Feb 15, 2018 at 11:47 am, Henning Weddig wrote:

Gordeon, please have a lok on the "famous" WA2EBY amp. He is using inductors in series with teh gate-bias resistors. My explanation is that this inductor of unknown value together with the gate-souce capacitance of the IRF 510 forms a parallel resonator, i.e. cancelling out the high gate capacitance. This may be the reason why he gets a flat(er) frequency response as shown in part 2 of his paper.? ?

Re: RD16HHF1 in the uBITX #ubitx

Gordon Gibby
 

¿ªÔÆÌåÓý

?Didn't realize he has L3 in there.? ? I have the boards and parts somewhere and may eventually get around to building it!


This would form a series circuit (to AC ground) with the gate-source capacitance.? ?In series circuits as the frequency nears resonance the voltage across individual components SOARS.? ? ? ?I haven't evaluated where he chose to put resonance but this may be a compensatory effort.? ?


Experimentation often beats out simulation.


Gordon



From: [email protected] <[email protected]> on behalf of Henning Weddig via Groups.Io <hweddig@...>
Sent: Thursday, February 15, 2018 2:47 PM
To: [email protected]
Subject: Re: [BITX20] RD16HHF1 in the uBITX #ubitx
?

Gordeon, please have a lok on the "famous" WA2EBY amp. He is using inductors in series with teh gate-bias resistors. My explanation is that this inductor of unknown value together with the gate-souce capacitance of the IRF 510 forms a parallel resonator, i.e. cancelling out the high gate capacitance. This may be the reason why he gets a flat(er) frequency response as shown in part 2 of his paper.? ?


In addition: the driving transistors hav e arelativly low ft, they must roll off.
LTSPICE simualtion of the bidi amp show a gain reduction of about 1 dB at 45 MHz, but for the driver stages in teh transmitter section things my be a bit different.
Simulation will schow!

BTW: I can confirm that the audio preamp in the receiver clips in reallity (on my BIOTX40) at output voltage swings as LTSPICE predicted.
Henning Weddig
DK5LV

Am 15.02.2018 um 18:58 schrieb Gordon Gibby:

?The old fashioned solution for capacitive loading was simply to put an inductor in parallel tuned to the desired frequency, to cancel it out.? ?


In my ancient vacuum tube rigs, they do that in the driver and final amplifier stages, and I get about the same power all the way from 80 meters through 15 meters, and in some rigs through 10 meters.? ??


Maybe they were on to something?? ?Perhaps there is a way to take that technique and apply it to semiconductor systems with some semiconductor switches to adjust component choices?



From: [email protected] <[email protected]> on behalf of Jerry Gaffke via Groups.Io <jgaffke@...>
Sent: Thursday, February 15, 2018 12:41 PM
To: [email protected]
Subject: Re: [BITX20] RD16HHF1 in the uBITX #ubitx
?
As reported here:??
an LTSpice model of Q90, Q911,Q912, Q92,Q93,Q96,Q97
shows that with the IRF510 gates clipped free of the circuit,
the signal available to the final in volts is about 77% at 30mhz what it is at 7mhz.
Power available is down by the square of the voltage, or about 60%.
LTSpice is probably assuming worst case 2n3904 parameters.
This result will not be fixed by going to RD16HHF1's.

With the IRF510 gates tied back in, the drop in signal became much more pronounced
due to capacitive loading by the IRF510's.? They need to be driven harder for good results at 30mhz.

Jerry, KE7ER

Re: RD16HHF1 in the uBITX #ubitx

 

The WA2EBY amp has also been simulated, including notes on what those inductor values are:
? ??/g/BITX20/message/41269

Somehow WA2EBY managed to get good performance without any switching or tuning when changing bands.

Jerry


On Thu, Feb 15, 2018 at 11:47 am, Henning Weddig wrote:

Gordeon, please have a lok on the "famous" WA2EBY amp. He is using inductors in series with teh gate-bias resistors. My explanation is that this inductor of unknown value together with the gate-souce capacitance of the IRF 510 forms a parallel resonator, i.e. cancelling out the high gate capacitance. This may be the reason why he gets a flat(er) frequency response as shown in part 2 of his paper.? ?

Re: RD16HHF1 in the uBITX #ubitx

 

¿ªÔÆÌåÓý

Gordeon, please have a lok on the "famous" WA2EBY amp. He is using inductors in series with teh gate-bias resistors. My explanation is that this inductor of unknown value together with the gate-souce capacitance of the IRF 510 forms a parallel resonator, i.e. cancelling out the high gate capacitance. This may be the reason why he gets a flat(er) frequency response as shown in part 2 of his paper.? ?


In addition: the driving transistors hav e arelativly low ft, they must roll off.
LTSPICE simualtion of the bidi amp show a gain reduction of about 1 dB at 45 MHz, but for the driver stages in teh transmitter section things my be a bit different.
Simulation will schow!

BTW: I can confirm that the audio preamp in the receiver clips in reallity (on my BIOTX40) at output voltage swings as LTSPICE predicted.
Henning Weddig
DK5LV

Am 15.02.2018 um 18:58 schrieb Gordon Gibby:

?The old fashioned solution for capacitive loading was simply to put an inductor in parallel tuned to the desired frequency, to cancel it out.? ?


In my ancient vacuum tube rigs, they do that in the driver and final amplifier stages, and I get about the same power all the way from 80 meters through 15 meters, and in some rigs through 10 meters.? ??


Maybe they were on to something?? ?Perhaps there is a way to take that technique and apply it to semiconductor systems with some semiconductor switches to adjust component choices?



From: [email protected] <[email protected]> on behalf of Jerry Gaffke via Groups.Io <jgaffke@...>
Sent: Thursday, February 15, 2018 12:41 PM
To: [email protected]
Subject: Re: [BITX20] RD16HHF1 in the uBITX #ubitx
?
As reported here:??
an LTSpice model of Q90, Q911,Q912, Q92,Q93,Q96,Q97
shows that with the IRF510 gates clipped free of the circuit,
the signal available to the final in volts is about 77% at 30mhz what it is at 7mhz.
Power available is down by the square of the voltage, or about 60%.
LTSpice is probably assuming worst case 2n3904 parameters.
This result will not be fixed by going to RD16HHF1's.

With the IRF510 gates tied back in, the drop in signal became much more pronounced
due to capacitive loading by the IRF510's.? They need to be driven harder for good results at 30mhz.

Jerry, KE7ER

Re: Toshiba Output Transistors for ubitx #ubitx

 

Farhan is actually referring to Mitsubishi transistors. See this message posted earlier today for some information:?/g/BITX20/message/41910--
Karl Heinz - K5KHK
Re: RD16HHF1 in the uBITX #ubitx

 

¿ªÔÆÌåÓý

That 40% drop explains a lot. ?I would still like to see that confirmed by test. ?It could also be compensated for on board to keep the drive level flat.?


Dr.?William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

?

Owner - Operator

Big Signal Ranch ¨C K9ZC

Staunton, Illinois

?

Owner ¨C Operator

Villa Grand Piton - J68HZ

Soufriere, St. Lucia W.I.

Rent it:


email:??bill@...

?


On Feb 15, 2018, at 11:41 AM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:

As reported here:??/g/BITX20/message/40938
an LTSpice model of Q90, Q911,Q912, Q92,Q93,Q96,Q97
shows that with the IRF510 gates clipped free of the circuit,
the signal available to the final in volts is about 77% at 30mhz what it is at 7mhz.
Power available is down by the square of the voltage, or about 60%.
LTSpice is probably assuming worst case 2n3904 parameters.
This result will not be fixed by going to RD16HHF1's.

With the IRF510 gates tied back in, the drop in signal became much more pronounced
due to capacitive loading by the IRF510's.? They need to be driven harder for good results at 30mhz.

Jerry, KE7ER

Re: Advice on selling Bitx40 on EBay

Vince Vielhaber
 

If you elect to set a reserve price, be warned that it turns off a lot of potential buyers and therefore will not bid. I usually just set a starting price for about the lowest I would take and let the bidding go where it's gonna go.

Vince.

On 02/15/2018 01:00 PM, wishbone_aaa wrote:
You have a few options. You can list with a buy it now price that you set, or list it for bids and let the bidders drive the price. You can set a reserve price on the bid that has to be met before it sells. Usually the bidders will drive the item to a fair price. Make sure that you provide good quality pictures and a full description and you will usually do better than expected.

--
Michigan VHF Corp.

Re: Advice on selling Bitx40 on EBay

 

You have a few options. You can list with a buy it now price that you set, or list it for bids and let the bidders drive the price. You can set a reserve price on the bid that has to be met before it sells. Usually the bidders will drive the item to a fair price. Make sure that you provide good quality pictures and a full description and you will usually do better than expected.
Re: RD16HHF1 in the uBITX #ubitx

Gordon Gibby
 

¿ªÔÆÌåÓý

?The old fashioned solution for capacitive loading was simply to put an inductor in parallel tuned to the desired frequency, to cancel it out.? ?


In my ancient vacuum tube rigs, they do that in the driver and final amplifier stages, and I get about the same power all the way from 80 meters through 15 meters, and in some rigs through 10 meters.? ??


Maybe they were on to something?? ?Perhaps there is a way to take that technique and apply it to semiconductor systems with some semiconductor switches to adjust component choices?



From: [email protected] <[email protected]> on behalf of Jerry Gaffke via Groups.Io <jgaffke@...>
Sent: Thursday, February 15, 2018 12:41 PM
To: [email protected]
Subject: Re: [BITX20] RD16HHF1 in the uBITX #ubitx
?
As reported here:??
an LTSpice model of Q90, Q911,Q912, Q92,Q93,Q96,Q97
shows that with the IRF510 gates clipped free of the circuit,
the signal available to the final in volts is about 77% at 30mhz what it is at 7mhz.
Power available is down by the square of the voltage, or about 60%.
LTSpice is probably assuming worst case 2n3904 parameters.
This result will not be fixed by going to RD16HHF1's.

With the IRF510 gates tied back in, the drop in signal became much more pronounced
due to capacitive loading by the IRF510's.? They need to be driven harder for good results at 30mhz.

Jerry, KE7ER

Advice on selling Bitx40 on EBay

Bob Dritz
 

I have an unbuilt Bitx40 and many accessories that I no longer have the time to build and am looking for advice about setting a price on EBay.?
It is one of the early versions, Serial Number 156, that came without a Raduino, which I purchased later and would be included.?
I also purchased a 10:1 potentiometer with a companion turns counter, a Buck Booster to boost the voltage for the final stage, a QRPguys Digital Dial Frequency Counter and two PLJ-6LED Frequency Displays (one in Red and one in Blue. Finally there is a nice square gold tone aluminum cookie tin measuring 6x6x2 3/4.?
Altogether I spend over $100 for all these items. My question is, if I ask $100 for all one EBay, is that too much or too little?
Any advice would be most appreciated.?
Re: RD16HHF1 in the uBITX #ubitx

 

As reported here:??/g/BITX20/message/40938
an LTSpice model of Q90, Q911,Q912, Q92,Q93,Q96,Q97
shows that with the IRF510 gates clipped free of the circuit,
the signal available to the final in volts is about 77% at 30mhz what it is at 7mhz.
Power available is down by the square of the voltage, or about 60%.
LTSpice is probably assuming worst case 2n3904 parameters.
This result will not be fixed by going to RD16HHF1's.

With the IRF510 gates tied back in, the drop in signal became much more pronounced
due to capacitive loading by the IRF510's.? They need to be driven harder for good results at 30mhz.

Jerry, KE7ER
Re: RD16HHF1 in the uBITX #ubitx

 

¿ªÔÆÌåÓý

Thanks vk2eka. Very informative study of the rd16hhf1 in a microbitx!?
72/73 de Chas ai4ot


On Feb 15, 2018, at 9:16 AM, Gordon Gibby <ggibby@...> wrote:

John, thank you for that extremely well documented information. Makes me much more interested in considering this. I wonder if the efficiency indicates that the circuit design could be improved?


On Feb 15, 2018, at 08:39, John <passionfruit88@...> wrote:

I have done a strait replacement of the IRF510s with RD16HHF1s.?
?
Here are the before and after values I got.
?
All tests done with uBitx VR1 drive level in the same position of approx 60% of range.
?
1. IRF510s and main board at 12.1V. PA idle current checked at 0.20A total (factory setting) so assume 100mA in each final.?
(For info, Rx currents: 164mA no volume, about 209mA "normal" volume).?
- At 7.1Mhz:? ?10W, total current: 1.79A, of which PA current: 1.31A, therefore main board current 0.48A
- At 14.2Mhz: 5.5W, total current: 1.39A, of which PA current: 1.0A,? therefore main board current 0.39A
- At 21.2Mhz: 2.2W, total current: 0.95A, of which PA current: 0.53A, therefore main board current 0.42A
- At 28.1Mhz: 1.3W, total current: 0.95A, of which PA current: 0.53A, therefore main board current 0.42A
?
?
2. IRF510s with 16.5V, 13.8V for main board. PA total idle current checked at 0.21A.?
(For info, Rx currents: 188mA no volume, about 230mA "normal" volume).?
- At 7.1Mhz:? 19W, total current: 2.65A, of which PA current: 2.09A, therefore main board current 0.56A
- At 14.2Mhz: 11W, total current: 2.20A, of which PA current: 1.80A, therefore main board current 0.40A
- At 21.2Mhz: 5.5W, total current: 1.40A, of which PA current: 1.00A, therefore main board current 0.40A
- At 28.1Mhz: 2.2W, total current: 1.02A, of which PA current: 0.60A, therefore main board current 0.42A
?
?
I haven't found a definitive reference for the safe and optimum values of the RD16HHF1s idle bias current but it seems to range from 200 to 500mA. So I would not recommend long term usage of the 500mA bias I used for these measurements.
I will reset mine to probably the 400-450mA value I read from some articles.
?
3. RD16HHF1s and main board at 12.1VDC, 250mA idle bias each (Total 0.5A PA idle current).?
- At 7.1Mhz:? 10W,? PA current: 1.20A
- At 14.2Mhz: 9W,? ?PA current: 1.21A
- At 21.2Mhz: 4.5W, PA current: 0.65A
- At 28.1Mhz: 5.5W, PA current: 0.95A
?
?
4. RD16HHF1s and main board at 12.1VDC, 500mA idle bias each (Total 1A PA idle current).?
- At 7.1Mhz: 10W, PA current: 1.18A
- At 14.2Mhz: 9W, PA current: 1.26A
- At 21.2Mhz: 5W, PA current: 0.71A
- At 28.1Mhz: 6W, PA current: 1.11A
?
?
5. RD16HHF1s and main board at 13.8VDC, 500mA idle bias each (Total 1A PA idle current).?
- At 7.1Mhz:? 13.5W, PA current: 1.95A
- At 14.2Mhz: 13.5W, PA current: 1.93A
- At 21.2Mhz: 6W,? ? PA current: 1.38A
- At 28.1Mhz: 9.5W,? PA current: 1.79A
?
?
?
Interesting observations:
?
A. The RD16HHF1 produces a much flatter power curver over frequency (in my device), although it shows a dip somewhere near the 15m band.
?
B. The IRF510 can produce some nice power in the lower frequencies when increasing the PA supply voltage, but it comes at the price of a steep power drop at higher frequencies.
?
C. The bias does not seem to influence the efficiency of the finals at full power with RD16HHF1, since biasing at 250 and 500mA produces essentially the same output for the same DC power input. Assuming distortion reduces with higher bias, can we assume a higher bias (within limits) is preferable? Any risk of thermal runaway?
?
D. The board main current (which includes the current in the driving stages of the power amplifier) does not seem to change with frequency from 20m onwards. Is this because the gain is pretty constant? If so, most of the drop in power with increasing frequency seems to be in the IRF510s, supporting the results obtained with the RD16HHF1s.
?
E. With the current uBitx PA circuit the RD16HHF1 seems limited in output, although not having the proper test equipment I can't say where the limitation occurs.
?
F. When I increased the drive through VR1 I noticed that at around 40% for the lower frequencies and at around 60% for the top frequencies I get a compression effect and the output does not increase much more from there on. I left it at 60% and got a positive feedback on the voice quality on my first QSO on 40m. Therefore I assume that the compression/clipping is not significant at that level (but I can't measure the sprectral purity).
?
?
So since my target was around 10W on 10m and 10 to 15W on 40m minimum I can say I have reached my goal just by changing the finals to RD16HHF1s and supplying the board with 13.8VDC (below the 15.2/15V stated in the respective datasheets of the RD16HHF1 and TDA2822).
?
To replace the finals I simply cut the legs of the IRF510s about 3mm above the board and correspondingly cut and crossed over the drain and source pins of the RD16s to match, then soldered in place.
?
It would be interesting to compare these results with others who performed the finals swap on the stock uBitx.
?
Next is the installation of the TPA2016 audio amplifier with I2C controllable AGC.

This is a lot of fun.
?
All the best,
?
73, John (VK2ETA)
?
<IMG20180215233124.jpg>
Re: Toshiba Output Transistors for ubitx #ubitx

 

Re: Aluminum enclosure

 

I believe option #2 will work with 4 powerpoles?as well - at least that's how I used 'em. Cheaper, too.

To increase stiffness, you'll have to pin each of the sets together - I use the little black pin to lock each pair, although I understand you can use zipties too.
And yeah - works fine and looks better if the two clamps are on the interior.

Mike Yancey, KM5Z
Dallas, Texas
Re: RD16HHF1 in the uBITX #ubitx

 

John,

Thanks for this great info!

I like your cross legged RDs :-)

Raj

At 15-02-2018, you wrote:

I have done a strait replacement of the IRF510s with RD16HHF1s.
?
Here are the before and after values I got.
?
All tests done with uBitx VR1 drive level in the same position of approx 60% of range.
?
1. IRF510s and main board at 12.1V. PA idle current checked at 0.20A total (factory setting) so assume 100mA in each final.
(For info, Rx currents: 164mA no volume, about 209mA "normal" volume).
- At 7.1Mhz:?? 10W, total current: 1.79A, of which PA current: 1.31A, therefore main board current 0.48A
- At 14.2Mhz: 5.5W, total current: 1.39A, of which PA current: 1.0A,? therefore main board current 0.39A
- At 21.2Mhz: 2.2W, total current: 0.95A, of which PA current: 0.53A, therefore main board current 0.42A
- At 28.1Mhz: 1.3W, total current: 0.95A, of which PA current: 0.53A, therefore main board current 0.42A
?
?
2. IRF510s with 16.5V, 13.8V for main board. PA total idle current checked at 0.21A.
(For info, Rx currents: 188mA no volume, about 230mA "normal" volume).
- At 7.1Mhz:? 19W, total current: 2.65A, of which PA current: 2.09A, therefore main board current 0.56A
- At 14.2Mhz: 11W, total current: 2.20A, of which PA current: 1.80A, therefore main board current 0.40A
- At 21.2Mhz: 5.5W, total current: 1.40A, of which PA current: 1.00A, therefore main board current 0.40A
- At 28.1Mhz: 2.2W, total current: 1.02A, of which PA current: 0.60A, therefore main board current 0.42A
?
?
I haven't found a definitive reference for the safe and optimum values of the RD16HHF1s idle bias current but it seems to range from 200 to 500mA. So I would not recommend long term usage of the 500mA bias I used for these measurements.
I will reset mine to probably the 400-450mA value I read from some articles.
?
3. RD16HHF1s and main board at 12.1VDC, 250mA idle bias each (Total 0.5A PA idle current).
- At 7.1Mhz:? 10W,? PA current: 1.20A
- At 14.2Mhz: 9W,?? PA current: 1.21A
- At 21.2Mhz: 4.5W, PA current: 0.65A
- At 28.1Mhz: 5.5W, PA current: 0.95A
?
?
4. RD16HHF1s and main board at 12.1VDC, 500mA idle bias each (Total 1A PA idle current).
- At 7.1Mhz: 10W, PA current: 1.18A
- At 14.2Mhz: 9W, PA current: 1.26A
- At 21.2Mhz: 5W, PA current: 0.71A
- At 28.1Mhz: 6W, PA current: 1.11A
?
?
5. RD16HHF1s and main board at 13.8VDC, 500mA idle bias each (Total 1A PA idle current).
- At 7.1Mhz:? 13.5W, PA current: 1.95A
- At 14.2Mhz: 13.5W, PA current: 1.93A
- At 21.2Mhz: 6W,??? PA current: 1.38A
- At 28.1Mhz: 9.5W,? PA current: 1.79A
?
?
?
Interesting observations:
?
A. The RD16HHF1 produces a much flatter power curver over frequency (in my device), although it shows a dip somewhere near the 15m band.
?
B. The IRF510 can produce some nice power in the lower frequencies when increasing the PA supply voltage, but it comes at the price of a steep power drop at higher frequencies.
?
C. The bias does not seem to influence the efficiency of the finals at full power with RD16HHF1, since biasing at 250 and 500mA produces essentially the same output for the same DC power input. Assuming distortion reduces with higher bias, can we assume a higher bias (within limits) is preferable? Any risk of thermal runaway?
?
D. The board main current (which includes the current in the driving stages of the power amplifier) does not seem to change with frequency from 20m onwards. Is this because the gain is pretty constant? If so, most of the drop in power with increasing frequency seems to be in the IRF510s, supporting the results obtained with the RD16HHF1s.
?
E. With the current uBitx PA circuit the RD16HHF1 seems limited in output, although not having the proper test equipment I can't say where the limitation occurs.
?
F. When I increased the drive through VR1 I noticed that at around 40% for the lower frequencies and at around 60% for the top frequencies I get a compression effect and the output does not increase much more from there on. I left it at 60% and got a positive feedback on the voice quality on my first QSO on 40m. Therefore I assume that the compression/clipping is not significant at that level (but I can't measure the sprectral purity).
?
?
So since my target was around 10W on 10m and 10 to 15W on 40m minimum I can say I have reached my goal just by changing the finals to RD16HHF1s and supplying the board with 13.8VDC (below the 15.2/15V stated in the respective datasheets of the RD16HHF1 and TDA2822).
?
To replace the finals I simply cut the legs of the IRF510s about 3mm above the board and correspondingly cut and crossed over the drain and source pins of the RD16s to match, then soldered in place.
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It would be interesting to compare these results with others who performed the finals swap on the stock uBitx.
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Next is the installation of the TPA2016 audio amplifier with I2C controllable AGC.

This is a lot of fun.
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All the best,
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73, John (VK2ETA)
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Re: Toshiba Output Transistors for ubitx #ubitx

M Garza
 

Do you have a link to the video?

Thanks

Marco - KG5PRT?

On Feb 15, 2018 8:17 AM, "Walter" <W9KJO@...> wrote:
Recently on a youtube video it was suggested that Toshiba output transistors might provided a little more power out for the ubitx.

Does someone have the actual part number for the transistors being referred to??

What other changes would be required in the ubitx for this modification?

73, thanks
Walter
W9KJO

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