1. BITX20@groups.io
   Date   
Re: Transmitter Mods

Jerry Gaffke
 

The parallel resonance helps us to a point, though an ideal inductor would generally be better.
For example, if the inductor is self resonant at 14mhz, we'd see much more power out on 20m
than we see on 10m.  I'd prefer to keep gain vs freq somewhat controlled and predicatable.

The caps are easier to add, easier to obtain, have a higher self resonance:
    https://electronics.stackexchange.com/questions/193608/self-resonance-frequency-for-mlcc-capacitor
Maybe add 220pF caps across all six of the 22 ohm emitter resistors, and forget the inductor?
Then add a variable cap somewhere around Q90 that can be tweaked to give the flattest response,
that setting may vary given your particular 2n3904 transistor characteristics. 
 
But the inductor in series with the negative feedback is a good idea.
If this can all be done with just 3 extra components and get good enough results across
the different uBitx's out there, I'm fine with that.

One other issue:
As Henning notes in post 45035, the chokes L8 and L9 are best wound on a single core:
See the discussion below figure 4 on this webpage, where he discusses how the bifiliar
approach works, though he does not discuss the individual choke solution:
    http://ludens.cl/Electron/mosfetamps/amps.html
I was seeing significantly worse results in how the uBitx final worked compared
to the WA2EBY final in my LTSpice simulation, could be due to these chokes.
    https://groups.io/g/BITX20/topic/9615903
I may have to play with that further, not obvious to me how or if the individual chokes
at L8, L9 would impact the results..

Jerry, KE7ER


On Thu, Apr 19, 2018 at 11:00 am, Jerry Gaffke wrote:
Good question.
It's a parallel resonance:  
    https://www.everythingrf.com/community/what-is-self-resonant-frequency
Re: ubitx is available for $109, there are a3 catches

M Garza <mgarza896@...>
 

You will receive a message from PayPal with a tracking number when it ships.  They are running 4 to 6 weeks behind.

Marco - KG5PRT 

On Thu, Apr 19, 2018, 8:14 AM RMV <W8RMV@...> wrote:
Ashhar Farhan,
Made my payment weeks ago.  Haven't heard anything aside from the Paypal payment notification.  Do I ever get a confirmation from you/uBITX prior to shipment?
Thanx - Bob W8RMV

Re: Transmitter Mods

Gordon Gibby <ggibby@...>
 

Aha!!! 

Thanks.  Didn’t realize it was parallel. 

Much appreciated.  Learn something every day!

Gordon




On Apr 19, 2018, at 14:00, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:

Good question.
It's a parallel resonance:  
    https://www.everythingrf.com/community/what-is-self-resonant-frequency



On Thu, Apr 19, 2018 at 10:55 am, Gordon Gibby wrote:
How is a series resonance 30,000 ohms?   
 
I’m kind of dumb, but I thought at series resonance , reactive components cancel and all that is left is the tiny ohmic resistance of the wire. 
 
What am I missing?
 
Re: Transmitter Mods

Jerry Gaffke
 

Good question.
It's a parallel resonance:  
    https://www.everythingrf.com/community/what-is-self-resonant-frequency



On Thu, Apr 19, 2018 at 10:55 am, Gordon Gibby wrote:
How is a series resonance 30,000 ohms?   
 
I’m kind of dumb, but I thought at series resonance , reactive components cancel and all that is left is the tiny ohmic resistance of the wire. 
 
What am I missing?
 
Re: Transmitter Mods

Gordon Gibby <ggibby@...>
 

How is a series resonance 30,000 ohms?   

I’m kind of dumb, but I thought at series resonance , reactive components cancel and all that is left is the tiny ohmic resistance of the wire. 

What am I missing?

Thanks

Gordon



On Apr 19, 2018, at 13:22, Howard Fidel <sonic1@...> wrote:

Gordon:
Very high, about 30 K. It actually helps us.

Howard

On 4/19/2018 1:03 PM, Gordon Gibby wrote:

​I found some on digikey with a self resonaance 40 Mhz or higher....


probably does matter.   At the self resonant point the series impeane will be very low....



From: BITX20@groups.io <BITX20@groups.io> on behalf of ohwenzelph via Groups.Io <Ohwenzelph@...>
Sent: Thursday, April 19, 2018 12:59 PM
To: bitx20@groups.io
Subject: Re: [BITX20] Transmitter Mods
 
does it matter that most 27uH inductors seem to have a self resonant frequency below 28MHz?
Re: ubitx is available for $109, there are a3 catches

K5ESS
 

No

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of RMV
Sent: Thursday, April 19, 2018 8:15 AM
To: BITX20@groups.io
Subject: Re: [BITX20] ubitx is available for $109, there are a3 catches

 

Ashhar Farhan,
Made my payment weeks ago.  Haven't heard anything aside from the Paypal payment notification.  Do I ever get a confirmation from you/uBITX prior to shipment?
Thanx - Bob W8RMV

Re: show your mic

Bill KC5SB
 

Here's mine.  I made it from an old 9 volt flashlight.
Re: Transmitter Mods

Howard Fidel
 

Gordon:
Very high, about 30 K. It actually helps us.

Howard

On 4/19/2018 1:03 PM, Gordon Gibby wrote:

​I found some on digikey with a self resonaance 40 Mhz or higher....


probably does matter.   At the self resonant point the series impeane will be very low....



From: BITX20@groups.io <BITX20@groups.io> on behalf of ohwenzelph via Groups.Io <Ohwenzelph@...>
Sent: Thursday, April 19, 2018 12:59 PM
To: bitx20@groups.io
Subject: Re: [BITX20] Transmitter Mods
 
does it matter that most 27uH inductors seem to have a self resonant frequency below 28MHz?
Re: Transmitter Mods

Howard Fidel
 

That is a good question. In our application, the impedance is still high, it just becomes more capacitive then inductive. If you look at the impedance plot, the resonance is about 20 MHz, but the reactance at 30 MHz is still 2000 ohms, so the gain goes up. On the 15 meter band, it looks like 30K ohms, so the amp runs open loop.
The bottom line is that the design is not that robust to begin with, and what I have made is a patch. I would never have designed the signal path myself this way. I would have use an opamp to drive the transformer to replace everything from C80 to T10.
The fix works, and has been validated by others. It would be smaller, probably not cheaper, but robust.

Howard

On 4/19/2018 12:59 PM, ohwenzelph via Groups.Io wrote:
does it matter that most 27uH inductors seem to have a self resonant frequency below 28MHz?
Re: Tx frequency selection for FT8 on BITX40 running Allard's sketch #bitx40

Gerry Hull
 

Hi Doug,

Agreed.  I operate remotely from the Yukon as VY1AAA a lot... when on FT8, it generates Big pileups.  Those people who understand how to use split in FT8 get through faster.  Technique is still important.

I’m excited to try FT8 on the uBitX (which arrives Friday) from the home QTH in NH.  10w + FT8 has provided many DXCC in short order.

Gerry W1VE


On Thu, Apr 19, 2018 at 11:32 AM Doug W <dougwilner@...> wrote:
Thanks Gerry.  Interestingly enough I did some searching on the topic of operating FT8 in split mode.  Turns out it is a hotly contested topic in certain circles with very strong opinions on both sides.  I think it is time for me to shift from theoretical to practical and leave the details to the guy with the medal from Sweden.

Re: Transmitter Mods

Gordon Gibby <ggibby@...>
 

​I found some on digikey with a self resonaance 40 Mhz or higher....


probably does matter.   At the self resonant point the series impeane will be very low....



From: BITX20@groups.io <BITX20@groups.io> on behalf of ohwenzelph via Groups.Io <Ohwenzelph@...>
Sent: Thursday, April 19, 2018 12:59 PM
To: bitx20@groups.io
Subject: Re: [BITX20] Transmitter Mods
 
does it matter that most 27uH inductors seem to have a self resonant frequency below 28MHz?
Re: UbitX I2C GPIO Breakouts?

Gerry Hull
 

Understood.  I’m wanting to put transverters in my ubitx; would love to control the I/O switching, as well as have the display show the transverted frequency. So, these would not be signals that needed to be switched rapidly.   I would not use it to key CW, but I might use these I/Os for a keying sequencer.

Gerry, W1VE



On Thu, Apr 19, 2018 at 12:45 PM Jerry Gaffke via Groups.Io <jgaffke=yahoo.com@groups.io> wrote:
Could work fine.
The library to speak i2c is already getting loaded for the si5351.

Primary issue I see is that i2c links take a millisecond or so,
vs under a microsecond for direct access of an IO pin.
At some point as we load up the Nano with i2c peripherals, it will get bogged down.
This applies to i2c displays as well.
Hasn't been an issue yet.

Another possible issue is that the common i2c bus provides an easy way
for RFI and birdies to find their way into the receiver.

Jerry, KE7ER


On Thu, Apr 19, 2018 at 09:28 am, Mark Kesner wrote:
Looks like a great idea to me.  I googled the mentioned boards and there is a lot of info on how to use these.  Sparkfun has breakout boards for a similar device for $5 as well as examples and links to the library, etc.

I guess it depends on the firmware you are using and whether there is room to load the library. (?)

Thanks!

Mark
KC4GIA
Re: Transmitter Mods

ohwenzelph
 

does it matter that most 27uH inductors seem to have a self resonant frequency below 28MHz?
Re: anybody tried softrock and hdsdr with Ubitx?

Paul Schumacher
 

Has anyone tried a softrock and hdsdr with Ubitx to get the spectrum and
waterfall display?  (or something similar?)

If so, can you please describe how to go about doing it?

thanks,

Paul K0ZYV
Re: UbitX I2C GPIO Breakouts?

Jerry Gaffke
 

Could work fine.
The library to speak i2c is already getting loaded for the si5351.

Primary issue I see is that i2c links take a millisecond or so,
vs under a microsecond for direct access of an IO pin.
At some point as we load up the Nano with i2c peripherals, it will get bogged down.
This applies to i2c displays as well.
Hasn't been an issue yet.

Another possible issue is that the common i2c bus provides an easy way
for RFI and birdies to find their way into the receiver.

Jerry, KE7ER


On Thu, Apr 19, 2018 at 09:28 am, Mark Kesner wrote:
Looks like a great idea to me.  I googled the mentioned boards and there is a lot of info on how to use these.  Sparkfun has breakout boards for a similar device for $5 as well as examples and links to the library, etc.

I guess it depends on the firmware you are using and whether there is room to load the library. (?)

Thanks!

Mark
KC4GIA
Re: UbitX I2C GPIO Breakouts?

Mark Kesner
 

Looks like a great idea to me.  I googled the mentioned boards and there is a lot of info on how to use these.  Sparkfun has breakout boards for a similar device for $5 as well as examples and links to the library, etc.

I guess it depends on the firmware you are using and whether there is room to load the library. (?)

Thanks!

Mark
KC4GIA
Re: need Linux users to debug a document

Rod Davis <km6sn@...>
 

Hi Tim,

Thank you for the offer.

I think it would be more useful if you have the actual uBITX radio
in-hand for testing.

You could email me when your rig is on-line.

Thanks,

Rod KM6Sn



On 04/19/2018 08:15 AM, Tim - M0THM wrote:

Hi Rod, I don't have my radio yet awaiting shipping. But if it's just a software thing I will be more than happy to help. I run Ubuntu x64 and Debian 9 and 8 but can spin up some other distros via my hyper-visor if you need.


Tim


M0THM

 


On 2018-04-19 13:50, Rod Davis wrote:

Hi All,

I need one or two Linux users to help debug a uBITX software manual.

All you need to do is follow the instructions in the manual that I will
supply, and report any problems encountered.

Any help would be appreciated.

Please contact me via private email.

Thank you,

Rod KM6SN
Re: Tx frequency selection for FT8 on BITX40 running Allard's sketch #bitx40

Doug W
 

Thanks Gerry.  Interestingly enough I did some searching on the topic of operating FT8 in split mode.  Turns out it is a hotly contested topic in certain circles with very strong opinions on both sides.  I think it is time for me to shift from theoretical to practical and leave the details to the guy with the medal from Sweden.
Tx frequency selection for FT8 on BITX40 running Allard's sketch #bitx40

Gerry Hull
 


Doug,

A picture is worth a thousand words:


No need, or reason, to use offset in the transmitter.  In fact, if you have CAT, WSJT controlls the transmitter frequency.

73, Gerry W1VE


On Thu, Apr 19, 2018 at 10:59 AM, Gerry Hull <gerry@...> wrote:
Within WSJT-X, you pick the transmit and receive frequencies, via the WSJT UI.  These are audio frequencies in your passband, not RF frequencies.

73, Gerry W1VE

On Thu, Apr 19, 2018 at 10:55 AM, Doug W <dougwilner@...> wrote:
First off, thank you both for the replies.  Secondly, if my response came across as harsh that was not the intention.  I think we are now splitting hairs on common practice vs best practice.  Right from K1JT himself in the WSJT-X user manual "To avoid QRM from competing callers, it is frequently desirable to answer a CQ on a different frequency from that of the CQing station. Choose a Tx frequency that appears to be not in use."  I realize for a manually controlled rig it wouldn't be practical to change the Tx frequency every time in a fast action digital mode but wouldn't it make sense to operate in split mode with an arbitrarily selected offset above 7.074.000 but still within 3kHz to reduce noise right at x.xxx.000?




Re: need Linux users to debug a document

Tim - M0THM
 

Hi Rod, I don't have my radio yet awaiting shipping. But if it's just a software thing I will be more than happy to help. I run Ubuntu x64 and Debian 9 and 8 but can spin up some other distros via my hyper-visor if you need.


Tim


M0THM

 


On 2018-04-19 13:50, Rod Davis wrote:

Hi All,

I need one or two Linux users to help debug a uBITX software manual.

All you need to do is follow the instructions in the manual that I will
supply, and report any problems encountered.

Any help would be appreciated.

Please contact me via private email.

Thank you,

Rod KM6SN
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