Date   
Re: The new uBITX boards are here

Ashhar Farhan
 

The load on the Mosfet gates is of 130pf in parallel with the gate resistor : 220 ohms in this case. The reactance of the gate capacitance would be about - j50 towards, the higher end of the HF spectrum. Paralleling a resistor with the the gate produces a load impedance for the push-pull driver. As Allison noted, our driver chain does not have enough juice at the higher end of the spectrum, the higher impedance decreases the drive requirements. I came upon the 220 ohms experimentally. I tried values from 10K downwards. More than 1K rested in in-stability. The output starts tampering off below 1K and rapidly so below 470 ohms. I tabulated the results inthe logbook. I don't have access to it now.
- f

On Mon, 28 May 2018, 06:06 Kees T, <windy10605@...> wrote:
I think the 27 ohms has more to do with 50 ohm input impedance matching.

73 Kees K5BCQ

Re: BITX QSO Afternoon/Evening, Sunday, May 27, 3PM & 7PM Local Time, 7277 kHz in North America, 7177 kHz elsewhere.

Jack, W8TEE
 

Used to have a cabin north of North Bay. Black flies are just about zero fun.

Jack, W8TEE

On Sunday, May 27, 2018, 7:37:08 PM EDT, Tom VE3THR <muzzmobility@...> wrote:


greetings from black fly country guys...up in Sudbury Ontario EN96 tonight. End fed inverted L and a Buddy Stick vertical just ain't cuttin' it tonight. Weak sigs - worked John WA3FZW briefly so far. Will keep trying till dark.
73 Tom VE3THR

Re: LM380 vs TDA2822 audio quality

Ashhar Farhan
 

Good to know! 


On Mon, 28 May 2018, 07:18 w1eat via Groups.Io, <w1eat=yahoo.com@groups.io> wrote:
Since I replaced my audio amp with an LM380 I just can't be more pleased with the results.  The LM380 has much less distortion for me on CW.  The 2822 must have been having input limiting and/or inter-modular distortion, with that square-wave buzziness being very noticeable on QRN and multiple loud CW sigs at once.  I had thought that Q70 was just being over-worked but that appears wrong.  I did do the 16K resisitor to ground from the base of Q70 mod before the 2822 had to be replaced and it seemed to help some at the time, but for the price of a resistor anything is worth trying.

I built the LM380 amp on a small piece of circuit board dead bug style.  Be sure to bypass the V+ pin close to the pin.  You can hear a lot of unwanted AM radio with sloppy wiring. 

Re: BITX40 CW Carrier Mod - CW Waveform shaping ? #bitx40

Dexter N Muir
 

How about a clamping FET like the anti-thump? (for the forgetful most :)  )
73
Dex ZL2DEX

Re: Dead Mic

Mike Lichtman
 

Pacific Antenna has a mic kit that will work.73 Mike Kf6kxg

Re: audio dropping out

 

It should refer to uBitx! Unless you tell us which board you are referring to then only someone can answer your questions!

At 27/05/2018, you wrote:

Raj,

I've seen many many references to the uBITX here. Allison is working on a mod to flatten the power curve across bands. So, I am confused what does the "u" stand for in "Bitx20/40/u"?. This is where Ashar sent me to ask questions? Was I mistaken?



Thanks,

Re: The new uBITX boards are here

Jerry Gaffke
 

As I say, it's curious.
And I still haven't figured any of this out.
My simulations often gave results that I found counterintuitive.
Never did graduate to messing with actual parts.

In the fourth paragraph of post 22597, Allison warns against too high of a drive impedance.
Though that likely pertains mostly with DC supplies well over 12v.
 
In post 41227 I report simulating the uBitx final in LT spice.  When driving the FET's with 
a 1:1 transformer I saw the input impedance drop from around 50 ohms at 7mhz
down to around 12 ohms at 30 mhz.  So 220 ohms seemed out of the ballpark. 

The Vishay datasheet says the IRF510 has an input capacitance of 180pf typical
when Vds is held constant at 25v.  I assume it's much more in this amp due to the Miller effect.

But I can't argue with what works. 

Jerry


On Sun, May 27, 2018 at 07:54 pm, Ashhar Farhan wrote:
The load on the Mosfet gates is of 130pf in parallel with the gate resistor : 220 ohms in this case. The reactance of the gate capacitance would be about - j50 towards, the higher end of the HF spectrum. Paralleling a resistor with the the gate produces a load impedance for the push-pull driver. As Allison noted, our driver chain does not have enough juice at the higher end of the spectrum, the higher impedance decreases the drive requirements. I came upon the 220 ohms experimentally. I tried values from 10K downwards. More than 1K rested in in-stability. The output starts tampering off below 1K and rapidly so below 470 ohms. I tabulated the results inthe logbook. I don't have access to it now.
- f

Re: The new uBITX boards are here

Ashhar Farhan
 

Jerry, 

This is science at work. We often get unexpected results. Those are the ones that pump up our adrenalin, the game is afoot, Watson! Something unexpected has shown up. Often times, in our bid to functionally decompose, we ten to ignore that the results from string up all the blocks together is also a result of how well they keep working to the spec under changed conditions. 
There is some interactivity between the driver output behaviour and the FET finals. This needs investigations on a rainy day.
- f

On Mon, May 28, 2018 at 9:35 AM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:
As I say, it's curious.
And I still haven't figured any of this out.
My simulations often gave results that I found counterintuitive.
Never did graduate to messing with actual parts.

In the fourth paragraph of post 22597, Allison warns against too high of a drive impedance.
Though that likely pertains mostly with DC supplies well over 12v.
 
In post 41227 I report simulating the uBitx final in LT spice.  When driving the FET's with 
a 1:1 transformer I saw the input impedance drop from around 50 ohms at 7mhz
down to around 12 ohms at 30 mhz.  So 220 ohms seemed out of the ballpark. 

The Vishay datasheet says the IRF510 has an input capacitance of 180pf typical
when Vds is held constant at 25v.  I assume it's much more in this amp due to the Miller effect.

But I can't argue with what works. 

Jerry


On Sun, May 27, 2018 at 07:54 pm, Ashhar Farhan wrote:
The load on the Mosfet gates is of 130pf in parallel with the gate resistor : 220 ohms in this case. The reactance of the gate capacitance would be about - j50 towards, the higher end of the HF spectrum. Paralleling a resistor with the the gate produces a load impedance for the push-pull driver. As Allison noted, our driver chain does not have enough juice at the higher end of the spectrum, the higher impedance decreases the drive requirements. I came upon the 220 ohms experimentally. I tried values from 10K downwards. More than 1K rested in in-stability. The output starts tampering off below 1K and rapidly so below 470 ohms. I tabulated the results inthe logbook. I don't have access to it now.
- f


Re: Raduino 4 Line Single Sided PCB boards

Rahul Srivastava
 

Thanks ..!! for the suggestion yes its a very useful addition given the variants of code available. I will update the pcb in couple of days.

73

Rahul VU3WJM 

Re: Need a Customs Form for import of Kees AGC and Pop-Thump kits into Canada. Can anybody let me know off-line? #ubitx-help

Peter LB0K
 

Wouldn't the Canadian Customs and Excise organisations website be a good place to start?
Alternatively check with the part of the postal service who probably deal with these matters.

Receive FM Radio Station #bitx40

qonita.salimah@...
 

Hello everyone..

Finally my bitx, showing some audio signal, but the sound that I've got is FM Radio, at 89-90 MHz.. Any clue why this could happen?

I didn't attach the DDS.

Thankyou very much

Re: RF power chain mods and improvements..

Kelly Jack
 

Hi all,

I've been following the various power train mod threads and trying stuff along the way.

So far this is where I am at:

Band                            Power with lowest band set for 5W                      Max power
80                                 5                                                                           15
40                                 10                                                                         20
30                                 10                                                                         20
20                                 9                                                                           19
17                                10                                                                          22
15                                10                                                                          18
12                                8                                                                            16
10                                6                                                                            16

Measurements should be taken as relative more than accurate absolute values as this is just using the power meter in my SWR meter but somewhat validated by measuring peak voltages across a simple diode cap meter (QRPlabs 20W dummy load).

Voltage 13.6V

Modifications:

Q90 replaced with sot23 version of 2n2222
C81 replace with 1.1n - see comments below
Q912, 911 replaced with MPSH10
R86 20uH added in series
R87, 88 add 330pf caps in parallel
Q92, 93, 96, 97 replace with 2n2222 (plastic TO92)
R941, 942, 911, 96 - add 330pf in parallel
R261, 262 - remove
T11 replaced with BN43-202 2:4 (primary:secondary) of 0.7mm coated solid copper
100pf silver mica across the primary.

Some comments about variations tried long the way but noting that some of this may be path dependent (ie may vary if order of mods changes).

C81 at 470pf reduced the lower bands quite significantly (peaking was in place for everything pre PA at this stage) - many incremental values tried to get the lower bands up. May be capable of further tweaking.
I had no luck with the MPSH10 at Q92 and friends.

Mods were focussed on even-ness across the bands rather than max power at any particular point.

Transformer does not get warm.

Have some 2n3866 on the way.

Larger values of the silver mica produced a more pronounced lump on the power profile in the mid lower of these bands.

Power on 160m is very low (2W).

Happy to take suggestions on what to try next.

I do not have equipment to test IMD at various stages of other more complex measurements.

Some weird peaking at 17M.

73




Simon
VK3ELH


















Oz uBITX in a Beautiful Wooden Box

Bill Meara
 

Re: W8TEE vft/tft questions

John P
 

To follow up on my post from last night, the "Rotary" library I've been using is from "// https://github.com/brianlow/Rotary"; I think this is the same one Jack used in his antenna analyzer code.

In the "Rotary.h" file for that library, you will find:

    // Enable this to emit codes twice per step.
    // #define HALF_STEP

or, I suppose you can define the symbol in your own code. When "HALF_STEP" is defined, the encoder will generate an interrupt at each detent and halfway in between. If the symbol is not defined, the encoder will only generate interrupts on the detents.

--
John - WA2FZW

Re: Oz uBITX in a Beautiful Wooden Box

Mike aka KC2WVB <rb5363@...>
 

Sweet, I had the same idea but have not implemented it.

Re: Receive FM Radio Station #bitx40

Mike aka KC2WVB <rb5363@...>
 

Well, I don't know what you have done since you first posted having an issue with audio and perhaps microphone but it seems you have audio coming to the headphone jack from the audio amp and that's in general what you want, just not with an FM station providing the audio.

First this disclaimer - I am a math guy professionally, electronics is my hobby -so I am about to wildly guess. It seems that you are in close proximity to a strong commercial FM radio station. I wonder if the wires associated with the radio you are building are behaving like an antenna for the FM signal and allowing the FM signal to be injected into the system. Another possibility is the source of power that eventually feeds the radio is not well grounded and acting as the FM signal's antenna thus allowing the FM signal into your rig.


So, I am thinking - if you give the FM signal an easier path to follow other than through your audio amp will the issue  disappear? Maybe, so how would you do this? I am thinking try these ideas:

Make sure that the source you use for power is well grounded. If you can't do this switch to a battery for power to the rig and ground its negative terminal to a cold water pipe.
If the rig is in a metal enclosure ground the chassis too.

Good luck.

On May 28, 2018 5:55 AM, <qonita.salimah@...> wrote:

Hello everyone..

Finally my bitx, showing some audio signal, but the sound that I've got is FM Radio, at 89-90 MHz.. Any clue why this could happen?

I didn't attach the DDS.

Thankyou very much


µBITX Shuts Down on 80 M

Arvo W0VRA
 

Good Morning, All!

I loaded Ian KD8CEC's software on the µB and started checking WSPR.  It works great.

The only problem is that when I do the 80 M check, on PTT the unit loses power for a second or two, then restarts normally, back in LSB mode on the last frequency I used.

Any ideas?  Bad relay shorting something out?

It works fine on the other bands.

Thanks in advance for any help!

Re: µBITX Shuts Down on 80 M

 

Arvo,

uBitx as I know has the highest output (probably in yours too) on 80M and due to current drawn is your power supply
shutting down or current limiting?

Raj

At 28/05/2018, you wrote:
Good Morning, All!

I loaded Ian KD8CEC's software on the µB and started checking WSPR. It works great.

The only problem is that when I do the 80 M check, on PTT the unit loses power for a second or two, then restarts normally, back in LSB mode on the last frequency I used.

Any ideas? Bad relay shorting something out?

It works fine on the other bands.

Thanks in advance for any help!

Re: µBITX Shuts Down on 80 M

Arvo W0VRA
 

On Mon, May 28, 2018 at 06:31 am, Raj vu2zap wrote:
current drawn is your power supply shutting down or current limiting?
Wow, that's exactly what it is!  When I try 80 M phone TX, the µB is on until I talk loudly into the mic, then the power supply light turns off.  It's supposed to be 12V, 2.08A, 25W.  I bought that power supply for the BITX40, but apparently it's not quite enough for the lower frequencies on the µB.  I am surprised.

Thanks for the suggestion!

I also found out that if you run a WSPR transmission with the antenna disconnected, the finals get very, very hot!  Don't do it!

Re: µBITX Shuts Down on 80 M

M Garza <mgarza896@...>
 

" also found out that if you run a WSPR transmission with the antenna disconnected, the finals get very, very hot!  Don't do it!"

You are transmitting with an infinite SWR.  I am surprised your MOSFET finals survived.

Marco - KG5PRT 

On Mon, May 28, 2018, 9:01 AM Arvo KD9HLC via Groups.Io <arvopl=yahoo.com@groups.io> wrote:
On Mon, May 28, 2018 at 06:31 am, Raj vu2zap wrote:
current drawn is your power supply shutting down or current limiting?
Wow, that's exactly what it is!  When I try 80 M phone TX, the µB is on until I talk loudly into the mic, then the power supply light turns off.  It's supposed to be 12V, 2.08A, 25W.  I bought that power supply for the BITX40, but apparently it's not quite enough for the lower frequencies on the µB.  I am surprised.

Thanks for the suggestion!

I also found out that if you run a WSPR transmission with the antenna disconnected, the finals get very, very hot!  Don't do it!