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Re: raduino for bitx 20

MVS Sarma
 

Once you have thought of using raduino, i suppose you could use one with nano and si5351. You could derive bfo and vfo also. On the bitx you could stop populating the crystal bfo, but use its buffer to amplify the raduino based .

In simple terms you could use bitx40 raduino changing the parameters to cover the band you need , for the bfo you decide upon.
Regards
Sarma vu3zmv



On Sun, 28 Apr 2019, 9:29 am N7QL <n7ql.us@... wrote:
I am trying to figure out what arduino modules I need to build the raduino. I found this display https://www.ebay.com/itm/2-4-inch-TFT-LCD-Touch-Screen-Display-Panel-Shield-For-Arduino-UNO-R3-MEGA2560/132795546292.  I also found this DDS module. I assume I'd also need the UNO R3 Mega 2560 module also. Would these work well together? What modules are normally used for the Bitx kits?

Re: Had audio, then no audio - looks like Q72 dead?

Mark Hatch
 

Thanks all for the encouragement.... So, yes that transistor was bad. I patched in a leaded part until the smt arrives from arrow this week. HOWEVER...

That wasn't the only problem.  I had a bad connection to my speaker and surprising, a bad pot for the volume control. Fixed all that, and the volume out the 16ohm speaker is adequate (not fantastic, but sufficient for me to think that a separate amp was unnecessary.

However, I still have an intermediate connection hanging around. If I squeeze the center of the top or bottom of the front of the enclosure, everything drops out. I suspect either a bad connection on the analog cable coming off the radiono or something else is grounding out. Should be easy, to find, but have not been able to duplicate it with the top off and pushing specific wires/boards....  I will eventually track it down.  ( I am using the front end board connection that amateurradiokits.in makes if someone has seemed something similar.

73
Mark
AJ6CU

Re: uBitx V5 Audio improvement

Ashhar Farhan
 

Yes, with diodes across the ep jack. This is to be done off-board.


On Tue 9 Apr, 2019, 12:04 PM Raj vu2zap, <rajendrakumargg@...> wrote:
Farhan,

For ear buds you should put a 100 ohms or so in series with the speaker output line. That will prevent blowing ears and ear buds!

Raj

At 09/04/2019, you wrote:
>LM386 distortion really increases with increased gain. gain is not sensitivity. a better idea might be to bypass pin 7 to ground with the 10 uf.
>either way, keep experimenting. I tried an external TDA2030 audio amp connected directly from the volume control. It can blow your ears if you are using earbuds, but it was really cool for speaker listening.




Re: Resistor wattage

Jerry Gaffke
 

I doubt very many Bitx40's have had R141 replaced,
only a few have reported this part to have failed.
Operating above 12.0v will improve your chances of seeing a failure here.

Another part that is dissipating more than it should is Q13, 
replacing it with a through hole (not surface mount) 2n3904 
should be sufficient.

Jerry, KE7ER


On Sat, Apr 27, 2019 at 09:02 PM, Adrian Chadd wrote:
is replacing that resistor a common mod for the bitx40?
 

Arduino modules for Bitx 20

N7QL
 

I am trying to figure out what arduino modules I need to build the raduino. I found this display https://www.ebay.com/itm/2-4-inch-TFT-LCD-Touch-Screen-Display-Panel-Shield-For-Arduino-UNO-R3-MEGA2560/132795546292.  I also found this DDS module https://www.ebay.com/itm/A401-AD9850-DDS-Signal-Generator-Module-0-40MHz-Test-Equipment-for-Arduino-YK/163426936824. I assume I'd also need the UNO R3 Mega 2560 module also. Would these work well together? What modules are normally used for the Bitx kits?

Re: Resistor wattage

N7QL
 

Thank you! Yeah with not the best vision I prefer through hole. 

Re: Resistor wattage

Adrian Chadd
 

is replacing that resistor a common mod for the bitx40?


-a


On Sat, 27 Apr 2019 at 20:39, MVS Sarma <mvssarma@...> wrote:
While homebrewing Sunil's bitx 20 or any other older version with through hole components , can better use quarter watt mfr and preferably mlc capacitors.

Sarma vu3zmv

On Sun, 28 Apr 2019, 7:35 am Jerry Gaffke via Groups.Io <jgaffke=yahoo.com@groups.io wrote:
The Bitx40 shipped by hfsignals is using all surface mount 1206 resistors, which are good for 1/4 Watt.
There are occasional reports of R141 burning up, the 10 ohm emitter resistor in the power amp driver,
so that one could be upped to 1/2 Watt (or two 20 ohm 1/4 Watt resistors in parallel)

Jerry, KE7ER

On Sat, Apr 27, 2019 at 06:55 PM, N7QL wrote:
What wattage resistors should I use to build the Bitx 20? I thought I saw the value of 1/2 watt thrown about somewhere but I cannot find it. I will be ordering the parts Monday that I don't already have so I am trying to be sure before I do any ordering. Thank you.

Re: Resistor wattage

MVS Sarma
 

While homebrewing Sunil's bitx 20 or any other older version with through hole components , can better use quarter watt mfr and preferably mlc capacitors.

Sarma vu3zmv

On Sun, 28 Apr 2019, 7:35 am Jerry Gaffke via Groups.Io <jgaffke=yahoo.com@groups.io wrote:
The Bitx40 shipped by hfsignals is using all surface mount 1206 resistors, which are good for 1/4 Watt.
There are occasional reports of R141 burning up, the 10 ohm emitter resistor in the power amp driver,
so that one could be upped to 1/2 Watt (or two 20 ohm 1/4 Watt resistors in parallel)

Jerry, KE7ER

On Sat, Apr 27, 2019 at 06:55 PM, N7QL wrote:
What wattage resistors should I use to build the Bitx 20? I thought I saw the value of 1/2 watt thrown about somewhere but I cannot find it. I will be ordering the parts Monday that I don't already have so I am trying to be sure before I do any ordering. Thank you.

Re: Resistor wattage

Jerry Gaffke
 

The Bitx40 shipped by hfsignals is using all surface mount 1206 resistors, which are good for 1/4 Watt.
There are occasional reports of R141 burning up, the 10 ohm emitter resistor in the power amp driver,
so that one could be upped to 1/2 Watt (or two 20 ohm 1/4 Watt resistors in parallel)

Jerry, KE7ER


On Sat, Apr 27, 2019 at 06:55 PM, N7QL wrote:
What wattage resistors should I use to build the Bitx 20? I thought I saw the value of 1/2 watt thrown about somewhere but I cannot find it. I will be ordering the parts Monday that I don't already have so I am trying to be sure before I do any ordering. Thank you.

Resistor wattage

N7QL
 

What wattage resistors should I use to build the Bitx 20? I thought I saw the value of 1/2 watt thrown about somewhere but I cannot find it. I will be ordering the parts Monday that I don't already have so I am trying to be sure before I do any ordering. Thank you.

Re: uBitx V5 Audio improvement

Steve MW0KST
 

John, as far as I understand, it's between pins 1 and 8 of the LM386 chip. You'd need to lift C75 and put these in series between the C75 pads.

Re: Kit-Projects ND6T Ubitx AGC

digger AB3XU
 

Tim, what kind of measurements are you getting with your v3?

Re: Kit-Projects ND6T Ubitx AGC

digger AB3XU
 

I did enough work for the day and said I could go out and play.

Did two sets of tests; first compared the level at vol-h and tp21. This was with ubitx set to 7.1MHz LSB. The levels weren't appreciably different.

The second was measured at vol-h and varied the ubitx receive freq and sideband. Again not an appreciable difference in level changing the freg from 7.1000 to 7.1MHz, but there was nothing measurable when swapping sidebands from lrb to usb on 7.101. I did hear a tone going below 7.100. I guess I should have taken some measurements there, but didn't.

Does getting nothing at 7.101 MHz USB mean I got the side bands swapped on the bfo? In any case it sounds good to my ear :)

-- digger AB3XU

Re: Had audio, then no audio - looks like Q72 dead?

Curt
 

Mark

Battle damage is part of the journey. Its no crime to use a leaded part to expedite repair.

You just might want another audio stage to drive a speaker decently.  recipes are around, and some folk use external amplified speakers. I plan to integrate a nescaf that has an output buffer.

Curt

Re: Kit-Projects ND6T Ubitx AGC

KE2GKB
 

yeah, If your putting an unmodulated carrier into the radio at the dial frequency you are not in the audio pass band. Which would explain why the math i was trying todo today was not working! When you get the chance can you test with these settings 7.101MHZ on the signal gen 7.100 Dial USB mode

That should throw a 1k tone out the speakers. Maybe even do it at 600hz offset or so pretending its CW.

-- Tim Keller - KE2GKB https://shop.kit-projects.com

Re: Kit-Projects ND6T Ubitx AGC

digger AB3XU
 

Should it have been offset?

Re: Kit-Projects ND6T Ubitx AGC

digger AB3XU
 

The signal generator and ubitx's frequency were set the same at 7.1MHz

Re: ubitx version 2 - expected rx background noise @ max AF gain, with antenna disconnected?

David Feldman
 

Curt - thank you for your reply as well (I did not see your reply until now.) My homebrew project is part of transverter system, and it is basically ubitx version 2 built from schematic, without the HF front end or power amplifier parts, a different microcontroller family/software, and slight change to DC bus power switching method. I have never used ubitx on HF and don't have HF antenna resource here anyway, so I am "flying blind" as this is my first experience with ubitx.

You and Sarma confirmed what I am observing - the overall gain seems just adequate for HF operation (I would not complain if my radio behaved this way for HF, as band noise would be the limiting factor). In my case, very weak signals may be expected, and I found that I could only hear my some-nanovolt synthesizer test carrier when ear very very close to speaker. I do not expect dynamic range concern in my application (in VHF/UHF, QRM is a treat, not a menace!)

This morning I tried temporarily replacing the audio preamp around Q70 (the MMBT3904 and it's surrounding parts) with an op amp, hoping I could obtain increased gain between the balanced modulator and the audio PA (using the now-shunned TPA2822), however, that resulted in less gain (even with the op amp running wide open), so was not successful.

Do you (or anyone) have any suggestions where I could increase the audio gain in the circuit area around Q70? It would be great if I can obtain another 6-10 dB in this area.

Thanks again!

Dave

Re: ubitx version 2 - expected rx background noise @ max AF gain, with antenna disconnected?

David Feldman
 

Thank you Sarma - I think you answered my question - receiver will be near silent when no antenna connected.

I realize it is normally obvious case (and of course I should have been more clear in my posting, because you made obvious observation!), however, I have unusual circumstance (no HF antenna and ubitx is not being built for HF application, instead it is part of transverter system where band noise is not limiting factor, but receiver internal noise is instead), so I want to find out normal user ubitx experience with HF antenna disconnected, to compare with my observation here.

Thank again!

Dave

Re: Kit-Projects ND6T Ubitx AGC

KE2GKB
 

Digger where in the AF band was your test conducted? Eg what was your dial frequency when your carrier was at 7.1mhz

-- Tim Keller - KE2GKB https://shop.kit-projects.com