Date   
Re: Another uBITX in a wooden box

Lee
 

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

 

Re: Another uBITX in a wooden box

Jack, W8TEE
 

Groan...

Jack, W8TEE

On Saturday, June 9, 2018, 9:21:57 AM EDT, Lee <mr.olson@...> wrote:


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

 

Re: The new uBITX boards are here

John AD0WX
 

My Yaesu HF rig is jealous.  Since I received my uBITX v3, I have been spending all of my ham radio time with it instead of my main rig - it's so much fun.  Thank you Ashhar for such a great product at an affordable price!

So much fun that I have ordered the v4 board.  I tried to make some of the mods to my v3 but I don't have the tools to work with surface mount devices (and I damaged my board trying to remove a capacitor - some creative soldering got it back working again).

Questions:

1) Is the mounting hole pattern for the v4 board the same as the v3?
2) Were the Raduino and analog connectors moved?

I ask about the board hole pattern and the connectors because I bought one of the 'amateurradiokits.in' enclosures to house my uBITX.

3) Is there a test point where an S-meter signal could be obtained?  So I can use this feature in KD8CEC's firmware.

Thanks,
John

Re: PA transistor Heatsinking of a uBITX #ubitx

Don, ND6T
 

Peter,

Aside from logistics (a plastic case, rear of cabinet too far from board, etc.) there is no downside. I do this on most of my BITX's, whenever possible, and it is the superior choice. No need for a heat-sink other than the metal case itself. It hardly gets warm at all at maximum power. Much more robust mounting. Lighter weight. Just use standard TO-220 mounting hardware including the insulators, a little heat-sink compound if you use a mica insulator. Cooler than the supplied heat-sinks by far.
73, Don

Re: PA transistor Heatsinking of a uBITX #ubitx

Ralph Mowery
 

I switched to the RF16HHF1 output transistors and this allowed me to directly bolt them to the heat sink.  I used one large heat sink for the two of them. This heat sink is bolted to the box I put it in.  I was lucky in one sense in that the box was just the right size to have the display out the front and the board just fit to the back of the box.

While not as nice looking as many of the others, you can see what I did here:  One pix is with the original transistors and one is with the larger heat sink.


Mine is near the end under my call of KU4PT



On Sat, Jun 9, 2018 at 8:06 AM, Peter LB0K <lb0k@...> wrote:

I can see the insulation argument to why these are installed hanging on to the IRF510s but this puts a large mechanical load on the transistor legs and increases the risks of damage, especially if one tried to use the uBITX as a portable, even as a SOTA rig.

 

One could fit a larger common heatsink that was fixed to the chassis/casing or PCB and one would then have to include rectangular insulating washers between the transistors and the heatsink.
These changes would increase the parallel drain(s) capacitance to ground, etc. etc.

 

I envisage these positive results:-

-       better mechanical strength

-       a more robust construction

-       easier to provide controlled cooling of the heatsink.

 

 

What sort of negative results should/could one expect from these measures?

 And how to fix'em?

 I envisage these negative results:-

-       a slight increase of weight

 


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"

 

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: 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: 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: 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@...> 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@...> 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@...> 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



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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: 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..

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@...> 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: 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..

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: 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: 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: 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: 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
 

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