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Bitx40v3: Analog Alley questions

 

So I bought one of the original $47 Bitx40's but I have been working away from home and fisrt wire do it up yesterday. I did order an ioLabs VFO for it and then got a raduino for it but have touch¨¦ neither. My first thought is to put in NPO caps and see if I can make the analog VFO stable enough to use as is. First mod is a polarity protection fuse and diode (been there).

So, I?have a couple of questions. I hooked it up and powered it on it ha dummy load and was surprised by the amount of noise a single I turned up the volume with no antenna. (#1)Where is this noise coming from?

Is it the LM386? Or some place else? Can the LM386 be replace with a TDA2822 And would that make a significant difference?


Second question: on earth of the first mods was to replace some of the resitors to reduce current and heat. Mine came with the extra resistors. So, (#2)is there any down side to doing this replacement?

Tnx & 73/72

Jer aa1of
 

On 30/04/17 03:09, ohwenzelph via Groups.Io wrote:

[lots of mods snipped] is there any down side to doing this replacement?

The main downside is your project will stop working and you won't be
able to fix it, then you will give up.

Put it in a box and build an antenna for it, and get on the air.

S
 

Already built an antenna for it, just not in the air yet, and won't be till I get back home again. And did hook it up to small loop, it receives well, CW and SSB. ?Or sure of the exact range yet. The supplied pot would be very touchy tuning but I have some ten-turn pots.?

Steve wrote "the main downside is that your project will stop working", well that is a risk but I am pretty sure I could do the exchange without breaking it.

So, is there any OTHER downside to putting in the higher ohm resistors????

Jer aa1of
 

NOT sure of the exact tuning range yet. ( I hate automatic spell "correction")
 

On 30/04/17 16:47, ohwenzelph via Groups.Io wrote:
Steve wrote "the main downside is that your project will stop
working", well that is a risk but I am pretty sure I could do the
exchange without breaking it.

So, is there any OTHER downside to putting in the higher ohm resistors????
What I mean to say here is, "putting higher ohm resistors in it" isn't
the valid electronics you announce it to be, but I was trying to be polite.

To be direct, if you pull your kit apart and "put higher ohm resistors
in it", it will stop working or else you will severely cripple it, plain
and simple.

Steve
Thomas Noel
 

¿ªÔÆÌåÓý

Steve et al,

This mod was recommended by A. Farhan himself as a means of reducing the heat from the BiDi amplifiers. This was way back in December?? as an attempt to decrease the frequency instability of the non-raduino first copies of the BitX40 with analog VFO. HFSigs was kind enough to even provide the resistors for those who wished to do the mod. I still have mine as I proceeded to buy the Radiono to go with my kit.

Still a valid way to deal with the analog VFO, but this gentleman has a synthesized VFO so unless he is looking for a small gain in field operation battery life, not much point in swapping the resistors.

Thomas W Noel
KF7RSF

On Apr 29, 2017, at 9:58 PM, Steve Wright <SteveWrightNZ@...> wrote:

On 30/04/17 16:47, ohwenzelph via Groups.Io wrote:
Steve wrote "the main downside is that your project will stop
working", well that is a risk but I am pretty sure I could do the
exchange without breaking it.

So, is there any OTHER downside to putting in the higher ohm resistors????


What I mean to say here is, "putting higher ohm resistors in it" isn't
the valid electronics you announce it to be, but I was trying to be polite.

To be direct, if you pull your kit apart and "put higher ohm resistors
in it", it will stop working or else you will severely cripple it, plain
and simple.

Steve
 

Jer,

Check if the board is already stable before you change to NP0 or change to 220 Ohms.

One of my early boards was very unstable and Np0's cured it.
A later board is very stable does not need the NP0's

Turn the volume down and does the noise go away or it is "motor boating" which happens if the audio volume wiring is wrong!

Raj

At 29-04-2017, you wrote:

So I bought one of the original $47 Bitx40's but I have been working away from home and fisrt wire do it up yesterday. I did order an ioLabs VFO for it and then got a raduino for it but have touch?? neither. My first thought is to put in NPO caps and see if I can make the analog VFO stable enough to use as is. First mod is a polarity protection fuse and diode (been there).

So, I have a couple of questions. I hooked it up and powered it on it ha dummy load and was surprised by the amount of noise a single I turned up the volume with no antenna. (#1)Where is this noise coming from?

Is it the LM386? Or some place else? Can the LM386 be replace with a TDA2822 And would that make a significant difference?


Second question: on earth of the first mods was to replace some of the resitors to reduce current and heat. Mine came with the extra resistors. So, (#2)is there any down side to doing this replacement?
 

On 30/04/17 17:48, Thomas Noel wrote:
Steve et al,

This mod was recommended by A. Farhan himself as a means of reducing
the heat from the BiDi amplifiers.
Well how about that. :) Stuff I never knew.

As you were, and apologies.

Steve
Thomas Noel
 

¿ªÔÆÌåÓý

No problem. It seems like it was 20,000 posts ago. ?;>)

Thomas W Noel
KF7RSF

On Apr 29, 2017, at 11:41 PM, Steve Wright <SteveWrightNZ@...> wrote:

On 30/04/17 17:48, Thomas Noel wrote:
Steve et al,

This mod was recommended by A. Farhan himself as a means of reducing
the heat from the BiDi amplifiers.

Well how about that. ?:) ??Stuff I never knew.

As you were, and apologies.

Steve
 

Hi Raj,

It actually seemed pretty stable to me but I did not park it on one frequency for a long time, nor did I have frequency counter on it, and it had warmed up for a while, and I did not try transmitting. Ashhar had said??"the six bidirectional amplifiers (Q1, to Q6) have increased current for better signal handling" so I wonder if there was a downside to switching out the 100 ohm (101) R's for 220 ohm (221) ones. "Better signal handling" sounds good though I am not sure how it is meant or how much of a practical change it makes. Otherwise, on the advantage side, besides generating less heat, the rig would need less current, an advantage if mobile and running on batteries.

The noise varies with the volume and goes away if the control is turned down enough. It is not motorboating. But it does seem to be a pretty loud noise floor for not having any signal at all. Perhaps it is picking up noise from the power supply or the environment and might be quieter running off batteries and inside a metal case. Note that I have not removed the 1uF cap (C113) between pins 1 and?8 of the LM386 and wonder if reduced background noise is part of the "improved audio" that comes with removing it.?

Thanks,

jer aa1or
 

On 30/04/17 18:48, Thomas Noel wrote:
No problem. It seems like it was 20,000 posts ago. ;>)
just about was ;)
 

Hi Jer,

First try an transformer PS or battery and see. Eliminate all obvious before jabbing the board.

I done a lot of mods to the VFO and got great performance. I am now tackling the BFO.

My next mod is to use TDA2822 which I swear by. I ordered some ready boards from BY with volume control.
The single channel 2W version sounds great, this is what I use in my projects.



Farhan has configured this chip into 1W amp with AGC. The second is used for AGC control.

Cheers
Raj

At 30-04-2017, you wrote:

Hi Raj,

It actually seemed pretty stable to me but I did not park it on one frequency for a long time, nor did I have frequency counter on it, and it had warmed up for a while, and I did not try transmitting. Ashhar had said? "the six bidirectional amplifiers (Q1, to Q6) have increased current for better signal handling" so I wonder if there was a downside to switching out the 100 ohm (101) R's for 220 ohm (221) ones. "Better signal handling" sounds good though I am not sure how it is meant or how much of a practical change it makes. Otherwise, on the advantage side, besides generating less heat, the rig would need less current, an advantage if mobile and running on batteries.

The noise varies with the volume and goes away if the control is turned down enough. It is not motorboating. But it does seem to be a pretty loud noise floor for not having any signal at all. Perhaps it is picking up noise from the power supply or the environment and might be quieter running off batteries and inside a metal case. Note that I have not removed the 1uF cap (C113) between pins 1 and 8 of the LM386 and wonder if reduced background noise is part of the "improved audio" that comes with removing it.

Thanks,

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