Date   

Re: RF power chain mods and improvements..

ajparent1/KB1GMX <kb1gmx@...>
 

On Sat, Jun 9, 2018 at 01:48 pm, Tim Gorman wrote:
As you predicted earlier, this is not optimum. While it increased my
output on 10m from 2w to 4w it also oscillates like crazy. The in/out
are just too close together for a 12db gain amp.
There is the are problem but the power increase didn't track either
as an additional 12DB should have driven the finals to well over 20W....
From 2-4W is only 3db increase.

Why didn't it?  First the pre-driver and driver have issues. and then 
the mmic took off oscillating as the input and output are way too close.

The amplifier from Q90 though the irf510s have to be taken as a system.
Every part of the chain has to meet some reasonable specs or the whole
mess fails.  This is why there is no simple fix.

Allison


External Amp

Howard Fidel
 

I have been working on a number of upgrades for the uBitx. One is an external amp. A number of people, including myself ordered an amp like this one: https://www.ebay.com/itm/70W-SSB-linear-HF-Power-Amplifier-For-YAESU-FT-817-KX3-Ham-Radio-DIY-Kits/401280684714?epid=579537921&hash=item5d6e3152aa:m:mTAXYtpMu9k-yfYI6Z1m1hQ

For the price it is a good deal, but it doesn't include the heat sinks or the needed low pass filters for each band. I currently have the unit running with my uBitx only on 20 meters. I temporarily but an appropriate filter on the board while I work on my uBitx daughter board that will be a collection of several improvements. I have attached my  version of the original schematic and also my revised schematic. I made one major change and a few minor ones. The major change is that I use two IRF520s in parallel instead of the original IRF530s. This came about accidentally, but it is a could change. When I put the amp together and started testing it, the FETs quickly self destructed, before I could shut it off. I looked through my parts been and found that I have a number of IRF520s but no IRF530. I checked the data sheet, and found that when you put 2 in parallel, the total capacitance increases by about 20%. But the thermal impedance for 2 in parallel is lower for the two, and the temperature rise in each is lower because the current is 1/2 for each, and the on resistance is not much higher in the IRF520. The bottom line, is you get much better thermal performance and can use a smaller heatsink. To the amp itself, I found that I get better performance by changing the 150 ohm feedback resistors to 235 ohm (to 470 in parallel) and I made the output transformer secondary 4 turns instead of 3. I got slightly better output power, and I believe a better antenna match, since my antenna is closer to 70 ohms then 50. Lastly, I changed R2 to 4.7K from 10 K and put a 6.8 volt zener in series with it so that the PTT can be put in parallel with the uBitx PTT switch. If you want to use the amp for both SSB and CW, then you will need to or the two lines together with a couple of diodes. I'm not running CW now, except for testing, so I didn't bother with it.

When I finish my daughter board design, I will post it. Probably in day or so. The amp is tested, the daughter board will be just the design at this point, with some parts breadboarded. 

Howard


Re: RF power chain mods and improvements..

ajparent1/KB1GMX <kb1gmx@...>
 

Hint the ADA4895 will not drive the IRF510s to full power.  It cannot produce enough power.

The PHA22 at 1DB compression is 22dbm almost 160mW  add IRF510 (assume low 13db gain)
and you get to almost 3.2W (if high maybe 6W).  The PHA22 is really power hungry and
regulated voltage.  If the board layout and pad are not right they can take off or melt.  Most
mmics trade power in for bandwidth. 


Allison


Re: RF power chain mods and improvements..

ajparent1/KB1GMX <kb1gmx@...>
 

Do not copy anything I wrote as its not done.

If you ask questions via email Before then I'm trying to be active
in the ARRL VHF/UHF contest.

IF you have different parts to try there are two possible paths send me enough
and I will consider trying them or try them yourself and report.  

Due board layout using SOT part for leaded is messy and hard to get the lead layout right.
Also asking me on new oddball pats gets the now standard answer.

                   Try it and report your results..

Allison


Re: RF power chain mods and improvements..

Tim Gorman
 

I put the board on the top side by removing C80 and hooking the
input/output to the pads there.

As you predicted earlier, this is not optimum. While it increased my
output on 10m from 2w to 4w it also oscillates like crazy. The in/out
are just too close together for a 12db gain amp.

When I applied TX power in CW mode it would jump immediately to 4w out
but when I let up on the key it would still be putting out 2w until the
TX relay dropped and removed the TX power.

I didn't even check it on any other band.

Next time I have the board out I'll try putting the amp on the
underside where I can separate the in/out so they are further apart.
Pin 5 on T8 and the top side of RV1 are further apart and, like you
say, that allows RV1 to control the output better.

Thanks,

tim ab0wr

On Wed, 06 Jun 2018 21:14:50 -0700
"Jerry Gaffke via Groups.Io" <jgaffke=yahoo.com@groups.io> wrote:

Tim,

The reason to add a stage of amplification like that is so we can
reduce the amplification of pretty much all the other stages.
With reduced gain, they have a much better chance of giving the same
gain at 30mhz as they do at 3.5mhz.

You could try patching this amp in when operating at 30mhz.
Turn RV1 down all the way, then slowly bring it up to get the power
you want. But you had best be ready to measure distortion in your
signal before getting on the air with it.

It could well be that Q90 will not work properly with the 10dB
increased input signal and will distort.  Having the amp after Q90
allows you to adjust RV1 down until any stage after the new amp does
not have too strong a signal, strong enough to distort.

I don't think you want this new amp in there at all when operating on
the lower frequencies with an otherwise stock rig.  Too much gain. 

I'm just kibitzing here, have not analyzed the Q90 stage.
You could take the LT-Spice model for the uBitx power amp from the
KE7ER directory in the files section, see what the simulation does
when Q90 is driven harder.

Jerry

On Wed, Jun 6, 2018 at 07:36 pm, Tim Gorman wrote:


Allison,
Jerry,

I have my little mmic board built. Would it be ok to add it before
Q90 by removing C80 and inserting the input and output on those
pads. Doing that would allow me to stick the board on top of the
relay that is right beside Q90. It would facilitate testing,
experimentation, and parts changeout if needed. It would also be
right beside my 7812 voltage regulator so I would have short power
leads.

Will another 10-12db of gain into Q90 be a problem?

tim ab0wr


Re: RF power chain mods and improvements..

Howard Fidel
 

Actually and reactive load, transformer or inductor, single ended or push pull.

On 6/9/2018 4:05 PM, Jerry Gaffke via Groups.Io wrote:
I'm learning here, never knew that a push-pull configuration for MMIC's was a thing.
But plenty of google hits, figure 2 on page 4 here shows one:
    https://www.modelithics.com/models/Vendor/MiniCircuits/PHA-22plus.pdf

Even configured for push-pull, there aren't many MMIC's that can deliver
the nearly 1W of power needed to drive those IRF510 gates at 30mhz.
There are MMIC's that could deliver the 100mW needed to replace Q911,912
when configured as a single.

I'm really curious how well that ADA4895-2 works for driving the the IRF510's.

Still not sure about the 2v.
The MMIC's are designed for a specific operating voltage, if designed for 4.0v and
you drop it to 2.0v, it won't draw any current from the supply and won't work.
My guess is that the 4.0v (4.5v absolute max) spec on the cheap BGA616 MMIC is the "supply voltage",
used in calculating how many ohms for the dropping resistor from your particular supply rail
to get the desired 60ma quiescent current into the MMIC.  Signal rides on top of that, so it's fair to 
have instantaneous voltages in excess of 4.5v on the output pin of the MMIC.

Jerry, KE7ER


On Sat, Jun 9, 2018 at 12:25 pm, Howard Fidel wrote:
Jerry:
When you use a transformer with the push pull configuration like Q93, Q97. the collector sits quiescent at the supply voltage. Then you add the + signal swing on to that to get the maximum voltage the device sees. So with a +2 V supply, you can't go lower then 0 volts, so you can't go higher then 2+2= 4 volts. That leaves a 1/2 volt margin for derating the device.

Howard



Re: RF power chain mods and improvements..

Jerry Gaffke
 

I'm learning here, never knew that a push-pull configuration for MMIC's was a thing.
But plenty of google hits, figure 2 on page 4 here shows one:
    https://www.modelithics.com/models/Vendor/MiniCircuits/PHA-22plus.pdf

Even configured for push-pull, there aren't many MMIC's that can deliver
the nearly 1W of power needed to drive those IRF510 gates at 30mhz.
There are MMIC's that could deliver the 100mW needed to replace Q911,912
when configured as a single.

I'm really curious how well that ADA4895-2 works for driving the the IRF510's.

Still not sure about the 2v.
The MMIC's are designed for a specific operating voltage, if designed for 4.0v and
you drop it to 2.0v, it won't draw any current from the supply and won't work.
My guess is that the 4.0v (4.5v absolute max) spec on the cheap BGA616 MMIC is the "supply voltage",
used in calculating how many ohms for the dropping resistor from your particular supply rail
to get the desired 60ma quiescent current into the MMIC.  Signal rides on top of that, so it's fair to 
have instantaneous voltages in excess of 4.5v on the output pin of the MMIC.

Jerry, KE7ER


On Sat, Jun 9, 2018 at 12:25 pm, Howard Fidel wrote:
Jerry:
When you use a transformer with the push pull configuration like Q93, Q97. the collector sits quiescent at the supply voltage. Then you add the + signal swing on to that to get the maximum voltage the device sees. So with a +2 V supply, you can't go lower then 0 volts, so you can't go higher then 2+2= 4 volts. That leaves a 1/2 volt margin for derating the device.

Howard


Re: RF power chain mods and improvements..

Howard Fidel
 

Jerry:
When you use a transformer with the push pull configuration like Q93, Q97. the collector sits quiescent at the supply voltage. Then you add the + signal swing on to that to get the maximum voltage the device sees. So with a +2 V supply, you can't go lower then 0 volts, so you can't go higher then 2+2= 4 volts. That leaves a 1/2 volt margin for derating the device.

Howard

On 6/9/2018 11:54 AM, Jerry Gaffke via Groups.Io wrote:
Howard,

Thanks for posting that!
I find it interesting that you got away without a transformer at T10.
You say flat to 30mhz, have you breadboarded it, or is that a result from simulation?

Those parts are likely a bit too expensive for hfsignals, but way more cost effective for most of us
than spending weeks trying to get some $0.15 parts to do the job.

>  The MMIC has a absolute maximum voltage of 4.5 VDC.
>  Assuming you use a transformer (actually you must to get the drive level  you need for the output stage)
>  you an only use a +2 volt supply for the device for a 4 v p-p swing.

Mouser summary for the BGA616 mmic says a 6v supply, but turns out that's the rail
feeding the resistor, the device sees 4.5v max.
Most of the new devices are shooting for very low power supply voltages. 
I can't quite follow the logic regarding the statement  "you can only use a +2 volt supply".
With a transformer between the mmic and the load it would seem the mmic supply could be most anything.
Data sheet suggests it would typically be a 33 ohm resistor from 6v, device drawing 60ma,
so 6v - 33*0.060 = 4.0v at the device if trying to use the BGA616 mmic.

At 18dBm, that mmic might just barely replace Q911,912.
But not drive the IRF510's.
Not a good choice for inclusion in the uBitx.
But still, an interesting and very cheap mmic.

Jerry


On Sat, Jun 9, 2018 at 06:00 am, Howard Fidel wrote:
Attached is my driver it goes between VR1 and the outputs of T10 you need to remove C84 and T10 and insert this circuit. I am using the AMP signal to reduce the overall power output when driving a linear amp which needs 5W not 10W. U7 is a current driver, I chose it because I have a number of them, I probably could select something better, or use an emitter follower but it should do the job at 0 cost for me. The same with the T13-1 transformer, I have them. The opamp was selected for its speed slew rate voltage and current drive capability. C45 is there because U7 needs a minimum load capacitance for stability. I will see if I need to add something there later. TX is the switched 12 volts that is there in transmit only.
I am working on a PCB with this being one part of a daughter board for the uBitx. I would be interested in any feedback. I am not suggesting that this is a cost effective way of improving the uBitx for production. I will post the entire schematic in a few days.



Re: KD8CEC Firmware S-Meter usage

Mark M
 

I'm planning to use the circuit on Ian's site that uses an LM386, just waiting to get the parts. Is there a simpler circuit?

Mark...     AA7TA


Re: The new uBITX boards are here

Ashhar Farhan
 

Yes, the mounting holes and the raduino are exactly where they earlier were. Yes, there are test points all over.
- f

On Sat, 9 Jun 2018, 20:36 John AD0WX, <ad0wx@...> wrote:
Oh, and one more question if I may:

4) Are there test points to provide audio in and out for digital modes?

Thanks again...


Re: RF power chain mods and improvements..

Jerry Gaffke
 

The ADA4895-2 that Howard chose to drive the IRF510's might turn out
to be a good high volume choice after all.
Can buy that dual op-amp from analog.com for $3.21@1000, presents almost
no load on the preceding stage, and apparently drives the IRF510's without a transformer.

Preceding stage with the HA-5002 is a voltage follower and a 1:13 impedance ratio transformer.
The HA-5002 is spendy for what it does here, should be plenty of other ways to implement that. 

Jerry


On Sat, Jun 9, 2018 at 08:54 am, Jerry Gaffke wrote:
Those parts are likely a bit too expensive for hfsignals, but way more cost effective for most of us
than spending weeks trying to get some $0.15 parts to do the job.


Re: PA transistor Heatsinking of a uBITX #ubitx

rcbuck@...
 

Ralph,

Did the RF16HHF1 change make the output more consistent across the frequency range of the transmitter?

Ray
AB7HE


Re: RF power chain mods and improvements..

IZ4SJP Carlo
 

I totally agree wit you
IZ4SJP carlo

Inviato da iPhone 5

Il giorno 09 giu 2018, alle ore 18:15, Bill Cromwell <wrcromwell@gmail.com> ha scritto:

Hi Allison,

This played a big part in my choice if the ubitx. I don't foresee any effort on my part to increase the power output at 10, 12, or 15 meters. I have used rigs on SSB with two watts and less on 10 and 15 meters to work the world. Of course, solar activity cycles influences that but I have worked a lot stations with power levels low enough that no meters were moving! Another way to express your point is - if we really wanted a radically different radio maybe that is what we should have bought.

Like you, I already have higher powered radios. Some of them weigh a pound per watt <evil grin>. Some are more reasonable. But 100 watt radios (even solid state rigs) on a park bench quickly burn through the batteries!

I do expect to make some minor mods involving CW keying, thumps, and a front panel "drive" control to manage the power levels. Ten watts is not *always* needed. One watt is not *always* enough. Sometimes one hundred watts is not enough. Change bands. The ubitx has all of the HF bands.

73,

Bill KU8H

On 06/08/2018 10:35 PM, ajparent1/KB1GMX wrote:
---snip------
As a QRP rig it is what it is for a good price. If I want 100W radio I
have it already.
Where the uBitx fits is the QRP replacement for a monoband only radio, its
multiband.

Allison
_._,_._,_
--
bark less - wag more



Re: RF power chain mods and improvements..

Bill Cromwell
 

Hi Allison,

This played a big part in my choice if the ubitx. I don't foresee any effort on my part to increase the power output at 10, 12, or 15 meters. I have used rigs on SSB with two watts and less on 10 and 15 meters to work the world. Of course, solar activity cycles influences that but I have worked a lot stations with power levels low enough that no meters were moving! Another way to express your point is - if we really wanted a radically different radio maybe that is what we should have bought.

Like you, I already have higher powered radios. Some of them weigh a pound per watt <evil grin>. Some are more reasonable. But 100 watt radios (even solid state rigs) on a park bench quickly burn through the batteries!

I do expect to make some minor mods involving CW keying, thumps, and a front panel "drive" control to manage the power levels. Ten watts is not *always* needed. One watt is not *always* enough. Sometimes one hundred watts is not enough. Change bands. The ubitx has all of the HF bands.

73,

Bill KU8H

On 06/08/2018 10:35 PM, ajparent1/KB1GMX wrote:
---snip------
As a QRP rig it is what it is for a good price. If I want 100W radio I
have it already.
Where the uBitx fits is the QRP replacement for a monoband only radio, its
multiband.

Allison
_._,_._,_
--
bark less - wag more


Re: RF power chain mods and improvements..

Jerry Gaffke
 

Howard,

Thanks for posting that!
I find it interesting that you got away without a transformer at T10.
You say flat to 30mhz, have you breadboarded it, or is that a result from simulation?

Those parts are likely a bit too expensive for hfsignals, but way more cost effective for most of us
than spending weeks trying to get some $0.15 parts to do the job.

>  The MMIC has a absolute maximum voltage of 4.5 VDC.
>  Assuming you use a transformer (actually you must to get the drive level  you need for the output stage)
>  you an only use a +2 volt supply for the device for a 4 v p-p swing.

Mouser summary for the BGA616 mmic says a 6v supply, but turns out that's the rail
feeding the resistor, the device sees 4.5v max.
Most of the new devices are shooting for very low power supply voltages. 
I can't quite follow the logic regarding the statement  "you can only use a +2 volt supply".
With a transformer between the mmic and the load it would seem the mmic supply could be most anything.
Data sheet suggests it would typically be a 33 ohm resistor from 6v, device drawing 60ma,
so 6v - 33*0.060 = 4.0v at the device if trying to use the BGA616 mmic.

At 18dBm, that mmic might just barely replace Q911,912.
But not drive the IRF510's.
Not a good choice for inclusion in the uBitx.
But still, an interesting and very cheap mmic.

Jerry


On Sat, Jun 9, 2018 at 06:00 am, Howard Fidel wrote:
Attached is my driver it goes between VR1 and the outputs of T10 you need to remove C84 and T10 and insert this circuit. I am using the AMP signal to reduce the overall power output when driving a linear amp which needs 5W not 10W. U7 is a current driver, I chose it because I have a number of them, I probably could select something better, or use an emitter follower but it should do the job at 0 cost for me. The same with the T13-1 transformer, I have them. The opamp was selected for its speed slew rate voltage and current drive capability. C45 is there because U7 needs a minimum load capacitance for stability. I will see if I need to add something there later. TX is the switched 12 volts that is there in transmit only.
I am working on a PCB with this being one part of a daughter board for the uBitx. I would be interested in any feedback. I am not suggesting that this is a cost effective way of improving the uBitx for production. I will post the entire schematic in a few days.


Re: CW transmit bandwidth #ubitxcw #ubitx

Tim Gorman
 

Nice job!

Did you try to capture two consective dits? Just to make sure the
trailing edge was being completed well before the next beginning edge?
If it is then just adding this capacitor would work for most purposes.

Thanks,

tim ab0wr

On Sat, 9 Jun 2018 13:48:04 +1000
"Allan Mason" <allan.vk2gr@gmail.com> wrote:

This email is for those interested in using the transceiver for CW.

Being mainly a CW operator, I was concerned about the V3 board uBitx
transmit CW wave shape being very hard with an almost square
waveshape and as expected, key clicks could be heard on either side
of the signal. A look at the circuit diagram and a little tinkering
today vastly improved the situation.

All that was required was to increase the value of C1 from 0.1uf to
1uf. Attached are some CRO photos of the end result showing the
leading edge and trailing edge of the transmitter output with a 1uf
connected across C1. The other photo shows where a short wire was
soldered to the hot side of C1 for the tests. In reality the wave
shape is now a little soft on the trailing edge, so 0.047 or 0.68uf
may be sufficient for some people. More work could possibly be done
with the CW keying RC network to the 1st balanced mixer, however this
one component simple fix will suit my needs.

The tests were contucted using the internal keyer set to 25wpm. The
CRO connection point was at the antenna BNC connector with a 50ohm
dummy load.

Regards,
Allan Mason, JP
Mobile: +61 401 324 058


On Fri, Jun 8, 2018 at 10:58 PM, Tim Gorman <tgorman2@cox.net> wrote:

How did you measure the bandwidth?

Remember that a square wave is a infinite series of odd harmonics.
Your keying is basically a square wave unless modified to have a
rounded up-slope and down-slope. Even then you will still have some
odd harmonics that cause the bandwidth of a repeating on-off dot or
dash to have a bandwidth increase over just the carrier itself.

tim ab0wr


On Thu, 07 Jun 2018 12:37:33 -0700
"K3OS" <garysch69@gmail.com> wrote:

Just got a v3 board running today. I was monitoring CW on my
IC7300 and noticed that when transmitting, i.e., a string of dots
or dashes, the bandwidth would widen to 1Khz then return to very
narrow. This occurred at a periodic rate if I held the dot or
dash lever. Internal keyer was used. When sending text the same
issue occurred but it was more difficult to spot. Initial test
was 40 meters, 12 watts out, but same results on 20, 8 watts out
all into a dummy. 12.2VDC power supply.

Any clues to why this happens and what can be done?

Gary K3OS



<http://www.avg.com/email-signature?utm_medium=email&;utm_source=link&utm_campaign=sig-email&utm_content=webmail>
Virus-free.
www.avg.com
<http://www.avg.com/email-signature?utm_medium=email&;utm_source=link&utm_campaign=sig-email&utm_content=webmail>
<#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>



Re: Spurs for Dummies? #ubitx-help

iz oos
 

The pa3ake are very good filters. However I am not sure they and any other BPF can filter enough the spur especially at the 15m band. What much down are the spurs at 15 and 12m bands?


Il 09/giu/2018 15:07, <ulf.jagfors@...> ha scritto:
Perhaps these practical BPF hints could be of value
https://martein.home.xs4all.nl/pa3ake/hmode/bpf_all.html
Ulf SM0CGL


Re: The new uBITX boards are here

John AD0WX
 

Oh, and one more question if I may:

4) Are there test points to provide audio in and out for digital modes?

Thanks again...


Re: Building homebrew ubitx: Need pre-v3 schematic PDF. Also, source for 45M15 (45 MHz IF) filter?

David Feldman
 

A couple of options (for making the crystal filter available to experimenters) come to mind -

1. Encourage the manufacturer to distribute via aliexpress (china->US small package shipping is very inexpensive, as the parcel volumes are very high)

2. Encourage a group buy in US (or other destinations) which could receive quantities sufficient to justify the China>India>X shipping route.

I think either (or an alternative) is worth considering, as it would encourage further experimentation and homebrewing, vs. drifting bitx towards a primarily commercial product.

Thank you,

Dave


Re: Another uBITX in a wooden box

IZ4SJP Carlo
 

Great!

Inviato da iPhone 5

Il giorno 09 giu 2018, alle ore 15:21, Lee <mr.olson@...> ha scritto:

Very nice.  I wood use a radio like that.
--
Lee - N9LO  "I Void Warranties"