Date   
Re: New ideas for the Audio TX/RX pop and PA output stage improvements on ubitx.net

Jerry Gaffke
 

History with the Bitx40 doesn't mean much if we're building a LPF for 30mhz.
Especially if we get the power up to 20 or 30 Watts.
But after poking around some I think brand name np0/c0g's from reputable vendors should be fine, 
you don't want junk.  Smaller caps in parallel are a good idea if experiencing trouble with currents.

This guy seem to know what he's doing.  His 1.5kW 30mhz LPF uses a the "1kV type MC22 Mica Capacitor",
perhaps Mouser 598-MC22FF101J-TF.  Can get them at a reasonable price if you want to take this to extremes..  
  http://w6pql.com/a_1.5kw_lpf_for_160-6m.htm


Jerry, KE7ER


On Sun, Feb 18, 2018 at 12:06 am, Jerry Gaffke wrote:
I think most builders just try some np0's and if they get warm then replace with a bunch of smaller value caps in parallel.
I'm not aware of any Bitx40 LPF caps blowing out, and I doubt they are anything special.

Re: New ideas for the Audio TX/RX pop and PA output stage improvements on ubitx.net

K9HZ <bill@...>
 

Yes, I suppose for the amateur builder, applying power to your design in and finger testing is an option.  If it doesn’t burst into flames, I suppose its ok?  (In commercial designing we don’t often have that option so we’ll have to stick to our calculus).  It might be wise to invest in one of those IR temperature guns from Harbor Freight Tools for $20 to save your fingertips though!

 

For LP design work at the approx.. 10 watt level… this just isn’t gonna be an issue unless you are using the wrong filter for the band and the filter is dissipating all of the power.  Once you get to the kW+ region… best use your math.

 

Like I said in my original note, if you are uncomfortable with the math, there are many calculators on the internet that work.  Just google them.

 

To be clear about the specification… it says that you would be operating at 0.1% of the full/ capable dissipation properties of the capacitor if it were used in a 50 VRMS circuit at 1 MHz  Using this one data point, you can translate that to any voltage/ frequency point and ratio it to this point to determine what % of dissipation you are operating (designing) at.

 

 

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From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of Jerry Gaffke via Groups.Io
Sent: Sunday, February 18, 2018 2:06 AM
To: BITX20@groups.io
Subject: Re: [BITX20] New ideas for the Audio TX/RX pop and PA output stage improvements on ubitx.net

 

I find that train of thought rather confusing.
Not sure where that 0.3amps average comes from, I'd think you could just find
the impedance from 1/(2*pi*Hz*Farads) and divide that into the 50 volts RMS to find current
rather than bother with the calculus.
Not at all clear how a 0.1% dissipation spec somehow means a max of 0.2 Amps at 30mhz.
A few more details would be appreciated.

I think most builders just try some np0's and if they get warm then replace with a bunch of smaller value caps in parallel.
I'm not aware of any Bitx40 LPF caps blowing out, and I doubt they are anything special.

Jerry


On Sat, Feb 17, 2018 at 02:11 pm, K9HZ wrote:

The current through a capacitor is given by I=C*dV/dt so the average current over time is I=C*int[dV/dt]/t… For your example: let’s use a 100pf capacitor in an 30 MHz circuit at 50 VRMS which is 140V P-P.  Iavg = 0.42 * 0.707 = 0.3 amps average.  Now the spec from that capacitor in your finding is 0.1% at 1 VRMS at 1MHZ which is 0.00028A * 0.707RMS *1000% = 0.2 Amps continuous at 30 MHz.  Yikes we are over by 50%!  Note that this DOES vary with capacitance… that’s why the larger the capacitor, the more current capacity is needed.

 


Virus-free. www.avg.com

Re: New ideas for the Audio TX/RX pop and PA output stage improvements on ubitx.net

Jerry Gaffke
 

I'm fine with math, and in fact prefer it over some web calculator.  Especially if that calculator
doesn't show formulas or state assumptions. 

I suspect this is quite opaque to most everyone on the forum except perhaps the person who wrote it:
    "0.1% at 1 VRMS at 1MHZ which is 0.00028A * 0.707RMS *1000% = 0.2 Amps continuous at 30 MHz"
 
Jerry


On Sun, Feb 18, 2018 at 08:40 am, K9HZ wrote:
Like I said in my original note, if you are uncomfortable with the math, there are many calculators on the internet that work.  Just google them.

Replacing T11 with a BN43-202 #ubitx

M Garza <mgarza896@...>
 

Just trying to get ideas on the best place to actually put the bn43-202.  I am curious to know what others have done.  Looking at my board, i think I might put it underneath, affixing it with some silicone.  I will run both the primary and secondary out of the same side.

I am also curious if anyone has just changed T11 and kept the IRF510s.  I wonder if just changing this to a 2:3 turns ratio transformer and adding in the 47pf capacitor will tame the frequency response.

I have a new appreciation for the ladies that actually assemble these radios.   

Thanks for any and all replies.

Marco - KG5PRT

Re: New ideas for the Audio TX/RX pop and PA output stage improvements on ubitx.net

Eric KE6US
 

It's funny until the caps pop and the FETs explode...then it's hilarious.

I've always tried to observe the working voltage spec. If that's more than sufficient, that seems to be all the cap engineering I've ever needed for ham work. I've never seen a current rating for caps I'm likely to use. When I want to calculate RF current, reactance in Ohms Law works well as you point out.

Eric KE6US


On 2/18/2018 12:06 AM, Jerry Gaffke via Groups.Io wrote:
I find that train of thought rather confusing.
Not sure where that 0.3amps average comes from, I'd think you could just find
the impedance from 1/(2*pi*Hz*Farads) and divide that into the 50 volts RMS to find current
rather than bother with the calculus.
Not at all clear how a 0.1% dissipation spec somehow means a max of 0.2 Amps at 30mhz.
A few more details would be appreciated.

I think most builders just try some np0's and if they get warm then replace with a bunch of smaller value caps in parallel.
I'm not aware of any Bitx40 LPF caps blowing out, and I doubt they are anything special.

Jerry


On Sat, Feb 17, 2018 at 02:11 pm, K9HZ wrote:

The current through a capacitor is given by I=C*dV/dt so the average current over time is I=C*int[dV/dt]/t… For your example: let’s use a 100pf capacitor in an 30 MHz circuit at 50 VRMS which is 140V P-P.  Iavg = 0.42 * 0.707 = 0.3 amps average.  Now the spec from that capacitor in your finding is 0.1% at 1 VRMS at 1MHZ which is 0.00028A * 0.707RMS *1000% = 0.2 Amps continuous at 30 MHz.  Yikes we are over by 50%!  Note that this DOES vary with capacitance… that’s why the larger the capacitor, the more current capacity is needed.

 


Re: Bitx40 - receiver works great, but do not transmit #bitx40help

Ivan Ilyichev
 

Good evening,
Thanks all for helping, transceiver works great, with a short vertical antenna Comet UHV-6 i have a lot of QSO up to 1300 kilometers during this weekeng.

Re: uBITX AGC - Adafruit TPA2016, A Success! #ubitx

 

Thanks Nik,

One more thing.  It appears we need a function:

setNoiseGateThreshold(0);

that you may have also added.

Aug
AG5AT

Re: New ideas for the Audio TX/RX pop and PA output stage improvements on ubitx.net

Mike Woods
 

Erhard DF3FY has confirmed that the correct binocular core is the  BN42-202.  It was a typing error on his part, and he apologises.

The wire is uncritical, it is simple hookup wire 0.5 mm in diameter.  The completed toroid fits in the original pad holes.

A corrected diagram and a photo of the PA, which clarifies everything better than 100 words, will be added to ubitx.net shortly.

73 Mike ZL1AXG 


Erhard On 17/02/18 10:10 AM, Mike Woods wrote:

If you look on the home page of http://www.ubitx.net you will find suggestions from Erhard Haertel DF3FY that address:

  • Audio Pops on transitions from RX to TX
  • Improved output on all bands from the PA stage (using RDF16HHF1s and a new output transformer and minor changes to the circuitry).

Erhard had difficulty posting to the BITX20 iogroups list so wrote to me directly.  I have not tested these mods, but these are two concerns about the uBITx (loud audio pops and lower power out above 40m) so I am sure that Erhard would be as interested as me in any feedback from those trying out his mods.

73 Mike ZL1AXG

--
Mike Woods
mhwoods@...


--
Mike Woods
mhwoods@...

Re: New ideas for the Audio TX/RX pop and PA output stage improvements on ubitx.net

Rob Snow
 

What would the impact be, or changes required, to use a BN43-202?  Again, I'm trying to learn here...so math is appreciated.  My newbie guesstimate (interested to see if I'm right or why I'm wrong) is that they are close enough physically and of the same material that they can be considered the same, especially in light of the +/- 20% AL

Here are the physical stats:

BN42-202
43 material
0.523" wide
0.296" thick
0.575" high
0.147" diameter holes.
AL=(can't find any)

BN43-202
43 material
0.525" wide
0.296" thick
0.565" high
0.150" holes
AL=2200 +/-20%
uH=(AL*Turns2)/1000


Re: New ideas for the Audio TX/RX pop and PA output stage improvements on ubitx.net

Philip
 

Still confused. I am sure its meant to be a  BN43-202.

Philip G7JUR

Re: uBITX AGC - Adafruit TPA2016, A Success! #ubitx

Hank W6IR <w6ir@...>
 

Where did you insert the board?

Re: uBITX AGC - Adafruit TPA2016, A Success! #ubitx

Nick VK4PP
 

My Appologies.
In my haste I pasted in the wrong function, I will get the correct one tonight...

I connected the board to the TDA side of the volume control, basically eliminating the TDA chip completely.

Please be aware that the output from the TPA2016 is to be connected directly to the speaker, and NOT grounded at all, this is due to the fact that these outputs are Bridge Tied Load which means you must connect the speakers directly - do not try to connect these outputs to another amplifier!

73 and good luck.

Re: Replacing T11 with a BN43-202 #ubitx

Nick VK4PP
 

Re: Replacing T11 with a BN43-202 #ubitx

M Garza <mgarza896@...>
 

Nik,
Thank you!


bitx40 amatures srccode build error

Richard E Neese
 

I am having build issues with the current code

Re: BITX QSO Afternoon/Night, Sunday, February 18, 3PM/7PM Local Time, 7277 kHz in North America, 7177 kHz elsewhere

John P
 

Sorry I missed the afternoon session. I'm on 7277 now.
--
John - WA2FZW

Re: Second batch of uBITX shipping? #ubitx

VE7WQ
 

Is it stuck in Canada?

S.F. Express International
http://intl.sf-express.com

2018-01-29    20:10:00
The item is at the Europe Distribution Center,
item arrived at facility

2018-01-31    08:04:00
The item is on transport to the country of destination,
shipment in transit,CANADA

2018-02-06    14:38:00
The item has arrived in the country of destination,
shipment in transit,CANADA

Today is: 2018-02-18    16:38:00
The item is NOT received yet.

It took 6 days for the item to reach Canada from India,
22 days past since then, but it is still traveling in Canada. (:

BIT40 Roter Encoder Mod

Richard E Neese
 

Anyone have a link to the rotar encoder mod for the bitx40 . I dont like the pot and would like to change out.

HFsignals no longer selling just vfo

Richard E Neese
 

we wanted a replacement vfo but it looks like hfsigs stopped selling just the vfo kit anyone know why ?

Re: HFsignals no longer selling just vfo

Ken
 

no idea but this is a reply I received from them when I inquired Dec 24.

'Yes. But you have to wait till our website is changed.

HfSignals Team'

73

Ken VA3ABN


On Sun, Feb 18, 2018 at 8:03 PM, Richard E Neese <kb3vgw@...> wrote:
we wanted a replacement vfo but it looks like hfsigs stopped selling just the vfo kit anyone know why ?