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Re: QSX 10W HF Linear PA kit

 


> I have just seen it on your website.?
> Really nice. How much gain does it?
> have if we exclude the first stage?

Well you know how these things are, every time you vary one thing, something else changes... so it's hard to be totally precise. But approximately the gain is split equally between the two stages. 13dB each.

> This kit won¡¯t make the spur and?
> bandpass problems of the uBITx?
> go away.? Period.? Those problems?
> occur in the early stages of the?
> uBITx.? To the contrary it has the?
> opportunity to make them worse?
> since the gain of the amp is flat?
> from 3-20 MHz? It may, however?
> be a nice replacement for the final?
> two stages in the uBITx if you want?
> to maintain a fairly flat gain in?
> those two stages.? That¡¯s all.

Yes, exactly what I said in my initial post on this topic. The uBITX has many problems (or depending on your viewpoint, challenges, minor issues, what you get in an experimenter's radio etc etc.). This amp kit fixed at best, the final two stages only. Garbage in, garbage out...

What it does show is:

1) Good PCB layout, short traces and short leads work wonders

2) IRF510's are good for the job - it isn't necessary to spend $$ on fancy RD15HVF1 or its brothers and sisters or uncles and cousins...

3) Surface mount components aren't necessary to assure stability either.

Note... even Chinese IRF510's do a great job - once you find the right and reliable supplier. All Ferrites in the kit are sourced from Diz at , I'm a highly satisfied (and not insignificant) customer!

73 Hans G0UPL?
?
Re: QSX 10W HF Linear PA kit

 

¿ªÔÆÌåÓý

Jerry,

I agree that we need more than one MMIC for the TX gain stages.

My initial idea was/is? to replace the "famous" Q90 with a three transistor W7ZOI amp (gain = 15 dB) may be using even BFR106 instead of the MMBT3904.

The output power of this stage may be limited to about +3 dBm as W7ZOI?? stated when using this amp in bidirectional mode. used in a single direction the linear oputput may be higher.?? The next stage has to deliver the necessary +14 dBm or even a bit more for "headroom") -- for this stage a MMIC could be one choice or another suitable "medium power transitor" with a high ft.?

Henning

Am 09.10.2018 um 20:06 schrieb Jerry Gaffke via Groups.Io:

First off, the uBitx as is does pretty well on 80/40/20 meters.
Power drops off on the stock uBitx as we go up to 15 and 10 meters.
There's 6 months worth of discussion in this forum about how best to?
get power up to where it should be on those high bands.
Tough to do, most attempts failed when modifying the existing uBitx power amp.
Grafting the QSX amp into the uBitx could mostly solve that.
Could also solve issues of power amp energy coupling back into the IF amps,
especially if the power amp is off in it's own box.

But the current signal levels in the IF amps and mixers create trouble with spurs
on those upper bands.? Not too much point in going to the QSX power amp unless
we clean that stuff up first.? And while we're at it, improve IMD and carrier leakage
in those IF amps and mixers as well.
?
If we assume we increase local oscillator CLK2 into the first mixer at D1,D2 up to 7dBm,
then the maximum signal into it from the 45mhz IF during transmit should be at least 10dB down
from that, or about -3dBm.? The mixer probably has a loss of around 6dB, and the 30mhz LPF
might lose another dB.? So if we replace everything from Q90 on out to the IRF510's with a
new power amp, that new amp will see a max of -10dBm, or 0.1mW going in.
This new QSX amp has 26 dB of gain for 10W out (where 10W out is +40dBm),
so needs 40dBm-26db = 14dBm going into the QSX amp (as Henning has said).
We need at least an additional 24 dB of gain to go from -10 dBm out of the 30mhz LPF
to +14dBm into the QSX amp.? That could easily be done with two MMIC stages,
and there are many such MMIC's capable of delivering 14dBm of power to the QSX amp.

Some extra gain in those two MMIC's would be good so we?can keep the signal through
the mixers even lower, and have some headroom for an adjustment such as RV1 of the uBitx.

Mouser 630-ADA-4743-TR1G

If you plan to bring the power up to 20W by boosting the supply voltage into the QSX amp,
then you will need another 3dB of power going in, so 14dBm+3dB=17dBm into the QSX amp.
And at 20W, you would want heavier transmit LPF's than the ones provided on the uBitx.

Also, it may be a good idea to have a 3dB attenuator between the MMIC's and the QSX amp
to keep it stable.

It will be interesting to see how clean we can make the uBitx as an exciter.
May need better transistors in the 45mhz stage, certainly want less gain
on the two transmit side IF amps.? Want 7dBm of drive from the local oscillators.
Perhaps the transformers in the mixers are not ideal, especially at 45mhz.
Raj has made considerable progress in sorting this some of this out.
?
I've got a QSX amp on order.?
Looking forward to playing with it.
But the uBitx has other issues to fix before we make use of the QSX amp
to increase power out on those upper bands.

Jerry, KE7ER



On Tue, Oct 9, 2018 at 07:54 AM, Henning Weddig wrote:

Hans,

I just ordered one of Your 10 W PA kits and quickly read over the assembly instruction.

Concerning the UBITX: the PA delivers 26 dB of gain, so for 10 W output the input power for the PA is +40 dBm - 26 dB = +14 dBm This power can be easily achieved with only one MMIC e.g. one of the GALI amps--- or a discrete verions (BS170)?

As You also offer LPF kits, the problems of the uBITX can be obsolete, but requires extra space for these extra boards.

One thing I m missing are the information about the P1dB pointz ( 40 dBm)? and IMD performance.?

Henning Weddig

DK5LV
Re: ubitx s-meter #smeter #firmware #ubitx #ubitx-help

David Berkompas
 

You could update the firmware, 1.1 is out.

A few things. Are you using a Nextion, have you built the extra stuff necessary (ie, another arduino nano?).

(I have a question about that, there's got to be a script/hex specifically for the 2nd nano, right?)

I have yet to put my uBitx all together, getting everything together first (Nextion 3.2")

But I think you need to use Memory Manager in order to get the s-meter working.

Or I could be completely off-base, as I'm very new to all this.


Dave - AI6K
Re: Harmonics and Relay Replacement

 

Kees

Has anyone tried adding a 0.1 mfd across each of the relay coils, and additional 0.1 mfd
to ground from various places in the DC going to these relays.? Suspicion is that some of
the unwanted coupling might be via the relay coils and connecting traces.

Arv
_._


On Tue, Oct 9, 2018 at 11:20 AM Kees T <windy10605@...> wrote:
Seems like most of these larger relays have the long armatures which run parallel to the coil and the coil is not shielded??

Re: QSX 10W HF Linear PA kit

 

Hmm, thought I had edited out the reference to the ADA4743 MMIC.
It has appropriate power out and gain and price, but unfortunately is now obsolete.
And the WYSIWYG browser based editor on groups.io is unfortunately not quite WYSIWYG.

Jerry, KE7ER
Re: QSX 10W HF Linear PA kit

 

First off, the uBitx as is does pretty well on 80/40/20 meters.
Power drops off on the stock uBitx as we go up to 15 and 10 meters.
There's 6 months worth of discussion in this forum about how best to?
get power up to where it should be on those high bands.
Tough to do, most attempts failed when modifying the existing uBitx power amp.
Grafting the QSX amp into the uBitx could mostly solve that.
Could also solve issues of power amp energy coupling back into the IF amps,
especially if the power amp is off in it's own box.

But the current signal levels in the IF amps and mixers create trouble with spurs
on those upper bands.? Not too much point in going to the QSX power amp unless
we clean that stuff up first.? And while we're at it, improve IMD and carrier leakage
in those IF amps and mixers as well.
?
If we assume we increase local oscillator CLK2 into the first mixer at D1,D2 up to 7dBm,
then the maximum signal into it from the 45mhz IF during transmit should be at least 10dB down
from that, or about -3dBm.? The mixer probably has a loss of around 6dB, and the 30mhz LPF
might lose another dB.? So if we replace everything from Q90 on out to the IRF510's with a
new power amp, that new amp will see a max of -10dBm, or 0.1mW going in.
This new QSX amp has 26 dB of gain for 10W out (where 10W out is +40dBm),
so needs 40dBm-26db = 14dBm going into the QSX amp (as Henning has said).
We need at least an additional 24 dB of gain to go from -10 dBm out of the 30mhz LPF
to +14dBm into the QSX amp.? That could easily be done with two MMIC stages,
and there are many such MMIC's capable of delivering 14dBm of power to the QSX amp.

Some extra gain in those two MMIC's would be good so we?can keep the signal through
the mixers even lower, and have some headroom for an adjustment such as RV1 of the uBitx.

Mouser 630-ADA-4743-TR1G



If you plan to bring the power up to 20W by boosting the supply voltage into the QSX amp,
then you will need another 3dB of power going in, so 14dBm+3dB=17dBm into the QSX amp.
And at 20W, you would want heavier transmit LPF's than the ones provided on the uBitx.

Also, it may be a good idea to have a 3dB attenuator between the MMIC's and the QSX amp
to keep it stable.

It will be interesting to see how clean we can make the uBitx as an exciter.
May need better transistors in the 45mhz stage, certainly want less gain
on the two transmit side IF amps.? Want 7dBm of drive from the local oscillators.
Perhaps the transformers in the mixers are not ideal, especially at 45mhz.
Raj has made considerable progress in sorting this some of this out.
?
I've got a QSX amp on order.?
Looking forward to playing with it.
But the uBitx has other issues to fix before we make use of the QSX amp
to increase power out on those upper bands.

Jerry, KE7ER



On Tue, Oct 9, 2018 at 07:54 AM, Henning Weddig wrote:

Hans,

I just ordered one of Your 10 W PA kits and quickly read over the assembly instruction.

Concerning the UBITX: the PA delivers 26 dB of gain, so for 10 W output the input power for the PA is +40 dBm - 26 dB = +14 dBm This power can be easily achieved with only one MMIC e.g. one of the GALI amps--- or a discrete verions (BS170)?

As You also offer LPF kits, the problems of the uBITX can be obsolete, but requires extra space for these extra boards.

One thing I m missing are the information about the P1dB pointz ( 40 dBm)? and IMD performance.?

Henning Weddig

DK5LV
Re: Harmonics and Relay Replacement

 

Pictures are always nice, Glenn.

Since most of these larger relays have the long armatures which run parallel to the coil and the coil is not shielded? (right ?), there would be RF coupling between the armature and the coil. It would also seem that, for a given voltage, higher current relays would imply larger wire, fewer turns, and less inductance for Port to Port coupling (right ?).?

Can't do much to reduce inner relay coupling but you could reduce relay to relay coupling by using a small RF choke (100uH) in the both existing relay coil leads. I like the WireWound ones from Bourns (CM322522-101K1).?

73 Kees K5BCQ
Re: QSX 10W HF Linear PA kit

jim
 

Interesting that you used ferrite type #61 for the T201/T202 interstage coupling ...Helge Granberg (as far as I can research) always used type #61 for his designs ..From what I've cobbled together, the #61's work where the #43 stuff does not

Jim


On Tuesday, October 9, 2018, 5:38:15 AM PDT, Hans Summers <hans.summers@...> wrote:


Hi all

It has been mentioned on this group a number of times in this discussion group so I am posting details here.?

I have now made available the QRP Labs 10W HF Linear PA kit, providing 26dB of gain with +/-1dB gain flatness from 2-30MHz, 10W output all the way up to 10m band from 12V supply. This amplifier uses two BS170 in push-pull as the driver and two IRF510 in push-pull as the final stage. This kit shows that two IRF510 MOSFETs can produce excellent results in a high performance yet low cost ($26) linear amplifier kit.?

See for details.?

I am not suggesting that this amplifier will solve all problems and without wishing to be offensive, the "garbage in, garbage out" rule always applies - in particular, if you feed it a signal containing spurs, harmonics, or other problems... then you will get the same thing at the other end, just amplified 26dB. It also still applies that all stages leading up to the final amplifier must have flat gain. If the pre-drivers cannot provide a big enough signal then you won't get full power output.?

But, it could be useful or interesting, in the BITX context, to look at the details of this amplifier kit and see the short lead lengths, symmetric PCB and extensively "stitched" groundplanes.?

I am very grateful to Allison KB1GMX for very valuable advice during the design and development of this amplifier, beta-testing prototypes, measurements and moral support.

73 Hans G0UPL
Re: Toroidal transformer values, toroids, windings, #ubitx #ubitx-help #parts

jim
 

From the uBITX website "circuit details" section :

Coil Details

  • L5, ?L7?: 12 turns on T30-6
  • L1, L2, L3, L4, L11, L12, L13?: 9 turns on T30-6
  • L14, L15, L16: ?10 turns on T30-6
  • L14, L15, L16: ?14 turns on T30-6
  • L20, L21, L22: 19 turns on T30-6

All the RF transfomers are 8-10 trifilar turns on FT37-43

Jim

On Monday, October 8, 2018, 11:24:09 AM PDT, cburf1@... <cburf1@...> wrote:


Hi all,

I'm about to embark on my first homebrew transceiver and have chosen the uBITX. I am lucky to have been given access to a large collection of unwanted though-hole components as we have gradually moved to surface mount at my company. For this reason, I am looking to do a project similar to this:??

My questions for now all regard the toroidal transformers. I can't find any info about these.

1. What toroids are used?
2. How many wraps of wire?
3. Are there any off-the-shelf alternatives anyone knows of should I choose to buy them?

Thanks for the help.

?

Re: QSX 10W HF Linear PA kit

 

¿ªÔÆÌåÓý

Best get after the rest of the radio then first.

?

?

From: [email protected] [mailto:[email protected]] On Behalf Of iz oos
Sent: Tuesday, October 9, 2018 11:27 AM
To: [email protected]
Subject: Re: [BITX20] QSX 10W HF Linear PA kit

?

Remember this commandment MadRadioModder: 'if you want even performance 3-30mhz you need to design that predriver section to be flat'

Il 09/ott/2018 17:56, "MadRadioModder" <madradiomodder@...> ha scritto:
>
> This kit won¡¯t make the spur and bandpass problems of the uBITx go away.? Period.? Those problems occur in the early stages of the uBITx.? To the contrary it has the opportunity to make them worse since the gain of the amp is flat from 3-20 MHz? It may, however be a nice replacement for the final two stages in the uBITx if you want to maintain a fairly flat gain in those two stages.? That¡¯s all.
>
> ?
>
> MRM
>
> ?
>
> ?
>
>
> --
>
> ¡­_. _._


--

¡­_. _._
Re: QSX 10W HF Linear PA kit

 

Remember this commandment MadRadioModder: 'if you want even performance 3-30mhz you need to design that predriver section to be flat'

Il 09/ott/2018 17:56, "MadRadioModder" <madradiomodder@...> ha scritto:
>
> This kit won¡¯t make the spur and bandpass problems of the uBITx go away.? Period.? Those problems occur in the early stages of the uBITx.? To the contrary it has the opportunity to make them worse since the gain of the amp is flat from 3-20 MHz? It may, however be a nice replacement for the final two stages in the uBITx if you want to maintain a fairly flat gain in those two stages.? That¡¯s all.
>
> ?
>
> MRM
>
> ?
>
> ?
>
>
> --
>
> ¡­_. _._
QSX 10W HF Linear PA kit

 

¿ªÔÆÌåÓý

This kit won¡¯t make the spur and bandpass problems of the uBITx go away.? Period.? Those problems occur in the early stages of the uBITx.? To the contrary it has the opportunity to make them worse since the gain of the amp is flat from 3-20 MHz? It may, however be a nice replacement for the final two stages in the uBITx if you want to maintain a fairly flat gain in those two stages.? That¡¯s all.

?

MRM

?

?


--

¡­_. _._
Re: QSX 10W HF Linear PA kit

 

Been meaning to buy some of the QRP Labs filters. So just purchased the Linear kit along with the filters. This will let me experiment with lowering the drive through the whole uBITX TX chain, most likely by greatly reducing the audio level, and see if and what improvements are made.

Most likely I'll mount the amp and filters in a stand alone box with an Arduino that will measure the TX frequency and automatically select the correct filter.

I'll include a small dummy load for the TX power to go until the correct filter is selected. Because the description of the amp claims the amp will survive large mismatches, I'll probably use something significantly higher than 50 ohms for the spurious output safety dummy load.

Tom, wb6b
Re: QSX 10W HF Linear PA kit

 

I have just seen it on your website. Really nice. How much gain does it have if we exclude the first stage?


Il 09/ott/2018 16:39, "Hans Summers" <hans.summers@...> ha scritto:
> Congrats for the amplifier. Surely interesting for TX homebrewing?
> at a reasonable cost. Is there any evidence that it would improve?
> the PA of the uBitx?

Evidence, no. I don't have a uBITX and the Linear kit has only just become available this afternoon.?

Theoretically: yes, it would improve the PA on the uBITX - a lot of care was spent on the board layout, keeping traces symmetric and leads as short as possible (look at the 1mm or so between the IRF510 body and the PCB, for example!). It has very flat gain from 2-30MHz and can even produce 10W on 4m band (70MHz) though gain is 8dB down by then... during testing this amplifier could not be made to exhibit any instability (oscillation). It also has a much larger heatsink than the stock uBITX amp, and the heatsink is grounded which also prevents feedback.?

BUT - the problems of the uBITX are not all in the driver and final PA stages. Earlier stages are overdriven and don't have flat gain with frequency. Spurs are generated but not filtered. Simply replacing the final two stages of uBITX only fixes some of the problems, not all.?

So yes, this amp would improve the PA... but at the end of the day it can only amplify what you give it: if what you give it is already unclean, it won't fix that.?

73 Hans G0UPL
Re: QSX 10W HF Linear PA kit

 

¿ªÔÆÌåÓý

Hans,

I just ordered one of Your 10 W PA kits and quickly read over the assembly instruction.

Concerning the UBITX: the PA delivers 26 dB of gain, so for 10 W output the input power for the PA is +40 dBm - 26 dB = +14 dBm This power can be easily achieved with only one MMIC e.g. one of the GALI amps--- or a discrete verions (BS170)?

As You also offer LPF kits, the problems of the uBITX can be obsolete, but requires extra space for these extra boards.

One thing I m missing are the information about the P1dB pointz ( 40 dBm)? and IMD performance.?

Henning Weddig

DK5LV

Am 09.10.2018 um 16:38 schrieb Hans Summers:

> Congrats for the amplifier. Surely interesting for TX homebrewing?
> at a reasonable cost. Is there any evidence that it would improve?
> the PA of the uBitx?

Evidence, no. I don't have a uBITX and the Linear kit has only just become available this afternoon.?

Theoretically: yes, it would improve the PA on the uBITX - a lot of care was spent on the board layout, keeping traces symmetric and leads as short as possible (look at the 1mm or so between the IRF510 body and the PCB, for example!). It has very flat gain from 2-30MHz and can even produce 10W on 4m band (70MHz) though gain is 8dB down by then... during testing this amplifier could not be made to exhibit any instability (oscillation). It also has a much larger heatsink than the stock uBITX amp, and the heatsink is grounded which also prevents feedback.?

BUT - the problems of the uBITX are not all in the driver and final PA stages. Earlier stages are overdriven and don't have flat gain with frequency. Spurs are generated but not filtered. Simply replacing the final two stages of uBITX only fixes some of the problems, not all.?

So yes, this amp would improve the PA... but at the end of the day it can only amplify what you give it: if what you give it is already unclean, it won't fix that.?

73 Hans G0UPL
Re: QSX 10W HF Linear PA kit

 

> Congrats for the amplifier. Surely interesting for TX homebrewing?
> at a reasonable cost. Is there any evidence that it would improve?
> the PA of the uBitx?

Evidence, no. I don't have a uBITX and the Linear kit has only just become available this afternoon.?

Theoretically: yes, it would improve the PA on the uBITX - a lot of care was spent on the board layout, keeping traces symmetric and leads as short as possible (look at the 1mm or so between the IRF510 body and the PCB, for example!). It has very flat gain from 2-30MHz and can even produce 10W on 4m band (70MHz) though gain is 8dB down by then... during testing this amplifier could not be made to exhibit any instability (oscillation). It also has a much larger heatsink than the stock uBITX amp, and the heatsink is grounded which also prevents feedback.?

BUT - the problems of the uBITX are not all in the driver and final PA stages. Earlier stages are overdriven and don't have flat gain with frequency. Spurs are generated but not filtered. Simply replacing the final two stages of uBITX only fixes some of the problems, not all.?

So yes, this amp would improve the PA... but at the end of the day it can only amplify what you give it: if what you give it is already unclean, it won't fix that.?

73 Hans G0UPL
Re: QSX 10W HF Linear PA kit

 

¿ªÔÆÌåÓý

,'
Il 09/ott/2018 14:38, "Hans Summers" <hans.summers@...> ha scritto:?

Hi all

It has been mentioned on this group a number of times in this discussion group so I am posting details here.?

  1. I have now made available the QRP Labs 10W HF Linear PA kit, providing 26dB of gain with +/-1dB gain flatness from 2-30MHz, 10W output all the way up to 10m band from ?supply. This amplifier uses two BS170 in push-pull as the driver and two IRF510 in push-pull as the final stage. This kit shows that two IRF510 MOSFETs can produce excellent results in a high performance yet low cost ($26) linear amplifier kit.?

See for details.?

I am not suggesting that this amplifier will solve all problems and without wishing to be offensive, the "garbage in, garbage out" rule always applies - in particular, if you feed it a signal containing spurs, harmonics, or other problems... then you will get the same thing at the other end, just amplified 26dB. It also still applies that all stages leading up to the final amplifier must have flat gain. If the pre-drivers cannot provide a big enough signal then you won't get full power output.?

But, it could be useful or interesting, in the BITX context, to look at the details of this amplifier kit and see the short lead lengths, symmetric PCB and extensively "stitched" groundplanes.?

I am very grateful to Allison KB1GMX for very valuable advice during the design and development of this amplifier, beta-testing prototypes, measurements and moral support.

73 Hans G0UPL
Re: Blew Audrino or LCD - How to fault find #bitx40help

 

Thank you for you comments

Gary
ZS5GI
Re: Harmonics and Relay Replacement

 

Can these good relays be bought through ebay? If so could you provide a link to a ebay vendor of the exact type you have?


Il 09/ott/2018 16:19, "Clark Martin" <kk6isp@...> ha scritto:
Per the Axicom and Virtual spec sheets, the Axicom draws about 20% more power.? That could mean a larger gap and thus lower contact to contact capacitance.

Clark Martin
KK6ISP

On Oct 8, 2018, at 9:38 PM, Mike Doty via Groups.Io <mikedoty@...> wrote:

Looking at the 3 rigs I have I found two different brands of relays installed, Hongfa and Virtual.? Readingt the datasheets for both brands and the Axicom relays the only difference I can see in the specs presented is a difference in coil resistance.? Notably though, neither datasheet for the installed brands gives a spec for RF isolation which makes me wonder whether they are actually rated for RF usage.? The datasheet for the Axicom indicates -39dB at 100 MHz.? I can't think of any other explanation for the results I'm getting but, as I also said in an earlier post, these are MY results that I have passed along for consideration.? For me, I'm satisfied with what I'm seeing.
Re: Harmonics and Relay Replacement

 

¿ªÔÆÌåÓý

Per the Axicom and Virtual spec sheets, the Axicom draws about 20% more power. ?That could mean a larger gap and thus lower contact to contact capacitance.

Clark Martin
KK6ISP

On Oct 8, 2018, at 9:38 PM, Mike Doty via Groups.Io <mikedoty@...> wrote:

Looking at the 3 rigs I have I found two different brands of relays installed, Hongfa and Virtual.? Readingt the datasheets for both brands and the Axicom relays the only difference I can see in the specs presented is a difference in coil resistance.? Notably though, neither datasheet for the installed brands gives a spec for RF isolation which makes me wonder whether they are actually rated for RF usage.? The datasheet for the Axicom indicates -39dB at 100 MHz.? I can't think of any other explanation for the results I'm getting but, as I also said in an earlier post, these are MY results that I have passed along for consideration.? For me, I'm satisfied with what I'm seeing.
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