Date   

looking for a ubitx board

Richard E Neese <kb3vgw@...>
 

My ubitx got hit by a power surge and I am looking for a board locally before ordering from hfsignals. SO if you have a ubitx unbuilt and willing to part let me know.


Re: Heat proofing the ubitx.

_Dave_ AD0B
 

I think I can blame android for the 4th paragraph.
Basically I meant to say that I had to redesign the shroud to fit the larger heatsinks and that I only have very slight warming with prolonged ft8 tx. 

A wood case fits over the bright red parts. 
73 
Dave


Re: Transmitter Mods

Howard Fidel
 

I did not get good results with this mod, I found 80 meters had reduced output. It is also difficult to implement, since to remove some of the parts, you need to remove the FETs first to get to them, at least I would have had to do that.
I did another mod that was easy, and also helped, along the same idea as Ashar's. I put a small cap from the top of VR1 to the wiper. The value needed depends on where you set the pot. If the pot is set to the top end, then it won't help at all. The problem with all these transmitter mods is that we are pushing the parts to there limits, and when you design without margin, you don't get consistent results. This is kind of how we got in trouble with the original design to begin with, where the design compromises were made to keep the cost down. My original 3 part mod, which you did works fairly reliably. Allison is working on replacing the existing parts with new parts to improve the performance, which is great. I have taken a different track and am working on a new transmitter power train. The problem with that is you need a new PCB.


On 5/31/2018 6:49 AM, Rob Bleumer wrote:
Hi all,
I did the same mod as Nigel G4ZA did but using FT37-43 giving 30uH  in series with R86 
and 2 ceramic disk C's 220 pF.

And  al with exact the same power output results!!

Now I see another mod by Ashar Fahran  changing C81 to 470pF.in the new uBITX.

Could I do the mod by Ashar too and will this give a better result???
Who can advise me about this?
Rob PA0RBL



Amazon

joe camilli
 

Any chance the ubitx could be offered via Amazom with the price to reflect the additional fees. The reason I ask is I have some Amazon gift cards to use up.

Tx Joe N7QPP


Re: Transmitter Mods

Kelly Jack
 

There are a number threads with the power train mods being discussed and I've lost track of where I read some comments I think between Farhan and Allison about using easily obtainable parts in the tens of thousands in the transmit chain as being a limitation on part choices.  What seems to emerging as an issue is that replacing components in the current transmit chain circuit to increase output at higher freqs is that the current architecture requires finding parts closer to the unobtanium end of the spectrum.

So my question is could this be solved by adding another amp stage allowing for lower gain at each stage but still using parts from the generic end of the spectrum?

73



Simon

VK3ELH


Re: New VK4PLN Audio Daughter Board + BCI

Paul Galburt - K2AYZ
 

I believe there are many pin-compatible replacements for the LM324 for those who want better audio noise performance. For example MC33179, MAX414 - although many through hole DIP parts are reaching end of life for manufactureres. No need to change to two dual parts.


Re: Transmitter Mods

Rob Bleumer <Bleumer@...>
 

Hi all,
I did the same mod as Nigel G4ZA did but using FT37-43 giving 30uH  in series with R86 
and 2 ceramic disk C's 220 pF.

And  al with exact the same power output results!!

Now I see another mod by Ashar Fahran  changing C81 to 470pF.in the new uBITX.

Could I do the mod by Ashar too and will this give a better result???
Who can advise me about this?
Rob PA0RBL


Re: New VK4PLN Audio Daughter Board + BCI

Kelly Jack
 

Hi Nik,

You could put the audio amp on there like a 2n3904 replacement version per the new ubitx version. Or some AGC circuitry?

Or one of the more sophisticated pop suppression circuits (admittedly not a clean installation as what you have designed here given need to link to traces on the board).

Could the SMM2167 stand vertically to conserve space for other stuff?

73



Simon
VK3ELH


Re: boosting the power on 28 MHz #ubitx

iz oos
 

Depends on the regions. In Europe 10 meters are open for e-sporadic in may and June every year. Anyway many vhf and uhf transverters have the IF at 28, so I'm my opinion it is important to have it fully functional even when the band is closed.


Il 31/mag/2018 09:39, "Terry Morris" <terry.kb8amz@...> ha scritto:
In the late 80's too.
KB8AMZ


Re: The new uBITX boards are here

MVS Sarma
 

lovely recollection of my 1st job doing optical design by using  BIG "BIBLE" LIKE 7 FIGURE LO AND SINE COSINE ETC BOOK -- WAY BACK IN 1964-65

 Thaniks Kevin

Regards
MVS Sarma
 

On Thu, May 31, 2018 at 12:45 PM, Kevin Luxford <kbgluxford@...> wrote:
Well you will just have to fall back on your Chambers Seven Figure Mathematical tables.  Or perhaps you can get your hands on a Monroematic electric calculator or even one of those crank and shift jobs we used in Physics labs 60 years ago.

73, Kevin VK3DAP / ZL2DAP






Re: boosting the power on 28 MHz #ubitx

Terry Morris
 

In the late 80's too.
KB8AMZ


Re: The new uBITX boards are here

Kevin Luxford
 

Well you will just have to fall back on your Chambers Seven Figure Mathematical tables.  Or perhaps you can get your hands on a Monroematic electric calculator or even one of those crank and shift jobs we used in Physics labs 60 years ago.

73, Kevin VK3DAP / ZL2DAP


Re: Need Clarification on uBitx v. 4 Schematic

MVS Sarma
 

i suppose that RD16HHF1 are to be used.  Some people experiment with RD15HVF1 too. They feel that 21 and 28 mhz performance would improve.
but you might suffer poor performance at 80m band etc


Regards
MVS Sarma
 

On Thu, May 31, 2018 at 9:50 AM, Mike <msmith@...> wrote:
Regarding the new version 4 schematic:

Do new components Q942 and Q952 connect in parallel with the IRF510's as per schematic or
are the RD15HV's meant to be used as an alternative to the IRF510's?

Thanks,
Mike



-Mike



Re: uBitx calibration #ubitx

Tom, wb6b
 

Hi Jerry,

Thanks for the additional information. I've been reading many of your explanations of the interworking of the si5351 with interest. Especially the tidbit about it using a variable delay line to implement non-integer dividers. 

Tom, wb6b


Re: New VK4PLN Audio Daughter Board + BCI

Nick VK4PP
 

Hi.

I'm thinking I'll make the board so it reaches all the way to the LPF relays.
One end is supported by the connector and then you can just glue a couple of 12mm stand offs on the first and last relay for the board to screw to.
Ill leaver the extra area blank for prototyping...

What would be best in the area? Me-Squares? or Through holes?
Thanks for the feedback.

73, Nick VK4PLN


Re: uBitx calibration #ubitx

Jerry Gaffke
 

Sounds like the CEC firmware uses about the same math as the stock uBitx code:
    https://groups.io/g/BITX20/message/37973

What calibration does is to set the value of si5351bx_vcoa
This is the frequency of the nominally 875mhz  oscillator inside the si5351
that is locked to the 25mhz reference crystal.
So if if it is being adjusted in steps of 8750, that's in increments of 10 parts per million.
As the value of si5351bx_vcoa is moved, the clk0,1,2 outputs from the si5351
get adjusted proportionally on any subsequent calls to si5351bx_setfreq()
 
With an operating frequency of 7.0 mhz, each increment in that "calibration number" of 10ppm would move it by 70 hz.
At 30mhz, the shift per calibration number increment is 300hz.

Jerry


On Wed, May 30, 2018 at 09:11 pm, Tom, wb6b wrote:
I only know about the CEC firmware. In that case it is the offset of the 25mhz crystal. The calibration number would be 0 if the 25mhz crystal was exactly correct.

If you use the CEC uBITX Manager, the master calibration number, in the Manager, is the calibration number you zero beat on times 8,750. So, the Master Calibration can vary from zero to large values. In my case I zero beat at 18, so 18 x 8,750 = 157,500.
[For sake of completeness, I'll add that in my case the "USB Calibration" sounded best at at 11,995,655.]
 
Also, I discovered you need to turn the power off to the uBITX and back on after each attempt to calibrate. (If connected, be sure to disconnect the USB cable, too, to remove that source of power to the processor.) Otherwise, the calibration (I think it is the value of the second LO frequency) shifts farther away from center each time you repeat the calibration step. 

The calibration steps appear to be 10hz with the CEC firmware. It may be different with the factory firmware.

Tom, wb6b


Need Clarification on uBitx v. 4 Schematic

Mike
 

Regarding the new version 4 schematic:

Do new components Q942 and Q952 connect in parallel with the IRF510's as per schematic or
are the RD15HV's meant to be used as an alternative to the IRF510's?

Thanks,
Mike



-Mike


Re: Connector Error in Schematic #bitx20help #bitx40help

Dexter N Muir
 

The standard 8-way looms are colored per resistor code, 0 - 7. These correspond to pins 1 - 8 then 9 - 16. Smaller connectors similarly color 0  onward for numbers 1 up. I don't have a ubitx so I can't comment on labelling, but I presume a close relationship to the bitx-40.


Re: Connector Error in Schematic #bitx20help #bitx40help

Dexter N Muir
 

Sorry, disregard. ubitx doesn't use the wiring looms. my bad ... :(


Re: SDR as Waterfall display

K9HZ <bill@...>
 

So I’ve actually done this… I used this SDR:   https://www.adafruit.com/product/1497  which tunes down to 24 MHz.  I tapped into the uBITx IF at TP14 on the rev4 schematic… before the 45 MHz roofing filter so the IF spectrum is still wide banded… used a 5pf cap as not to load the IF.  I ran that into an IF amplifier made from a MC1350P circuit for 45 MHz right out of the app note.  The response from 1-30 MHz is not flat, so I took an analog pin from the Arduino to set the AGC on the MC1350P and developed a table that generates an AGC voltage for each band as selected that is calibrated basis a known input signal to give dBm on the waterfall.  The software I used for the spectrum display is Freq-show from here: https://github.com/adafruit/FreqShow .  It works very well.  I will post a video when my ubitx is back together (currently adding… yes… a “second” receiver… ohhhhh!).  I’m not an expert coder, but once this Python app can be coded into the Teensy, I think we have an all-in-one solution!

 

 

Dr. William J. Schmidt - K9HZ

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of Ralph Mowery
Sent: Wednesday, May 30, 2018 2:43 PM
To: BITX20@groups.io
Subject: Re: [BITX20] SDR as Waterfall display

 

I have not tried it,but from the circuit description the first conversion is at 45 MHz.  I would try laying a short insulated wire near Q10.  You may even be able to tap off the emitter of q12 with a low value capacitor. 

 

Then tune the SDR ( I assume we are talking the about $ 15 TV dongle, but does not matter)  to around 45 MHz.  

 

There may be more out now, but the two that I bought a number of years ago, one goes from about 25 MHz up and the other starts at 50 some MHz.

 

de ku4pt

 

 

On Wed, May 30, 2018 at 3:06 PM, brad martin <emclinux@...> wrote:

I noticed that the CEC firmware has an SDR mode but this seems to be where the audio as as well are transmitted to the SDR and handled there.  Seems to be a good method for digital or recording but is there a way to just use the SDR as a waterfall display and still have the radio function as normal (i.e. have audio come out the radio speakers)?

 

Brad

 

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