Date   
Re: It stopped transmitting

John Backo
 

Note that you still haven't figured out what caused the problem in the first place. It may be that there is too much current flowing through the transistor and the emitter resistor may have to be adjusted. This can happen with too long a hold on the PTT. Maybe a heavier transistor is called for...

It may be that there is too much residual carrier coming through which would put a greater load on the transistor...

Or there is too great an (unanticipated) impedance mismatch...

These are the usual suspects. Think about it.

john
AD5YE


---In BITX20@..., <bill@...> wrote :

I replaced q13 ( wasn't every easy for my old eyes) it fixed the problem.  I now have normal output power.  Thanks guys. 

Re: Band Pass Filter High Attenuation

John Backo
 

---In BITX20@..., <marktbaldridge@...> wrote :

Okay. That is helpful information.

A couple questions: 

1: Can I assume that I will for the most part tune the inductors together? To make the correct bandpass, they must all be the same value, right?

[john]  More or less. Please note that the 82 pF. caps in the original schematic are wrong. Most people get by with about 33-39 pF. Those and 4-5 uH. seems to tune 20m well. Note that the tuning for the middle transformer is a bit different than for the outer ones. This is normal for a LC filter.

2: Can I attach a 50 ohm spectrum analyzer as I showed in the link? Or will the impedance mismatch cause the filter to not function properly?

[john]  If it does, a simple 4:1 transformer. or even an inline resistor at each end, will probably straighten it out. Experiment. I assume you are disconnecting the BPF temporarily from the circuit anyway. Include an attenuator to control your input signal. Tune for the LEAST coherent signal level.

What I did was build a new BPF based on the one in the BITX20A. It works very well and is a bit easier to adjust. You can also build a new one if you have 3 or 4 FM IF transformers handy. YRMV. Hi.


john
AD5YE

Re: Got my BITX40 Yeay!!

Roy Appleton
 

Tony, what date did you get shipping notification? 

Roy 
WA0YMH

On Jan 4, 2017 7:33 PM, "k6alf@... [BITX20]" <BITX20@...> wrote:
 

Mr. USPS delivered my BITX40 today..


Appears to have survived the trip.  Packaging took a beating but it looks intact.


Will post pic's of packaging.


TonyF, K6ALF

Re: Si5351 VFO - Low Pass?

Ken
 

Joel when you say noisier, do mean sounds noisier or scope trace is noisier? I built the top filter and I didn't hear any difference. On the scope, the signal cleaned up good, but I could see some phase noise.

73

Ken VA3ABN

On Wed, Jan 4, 2017 at 8:26 PM, Joel Caulkins caulktel@... [BITX20] <BITX20@...> wrote:
 

Andy,

Mine was noisier too until I put a LPF inline with the Si5351. I got the idea here. Scroll down the page a ways to find the filter table.

On Jan 4, 2017, at 5:01 PM, ahecker@... [BITX20] <BITX20@...> wrote:

 

I noticed that my receiver got noisier when I disconnected the built-in VFO and added the Si5351.  I get that a filter re-shapes the waveform, but I'm wondering about whether it's useful to clean the output signal a bit before injecting it into the radio.



I guess this is where the 'experiment' and 'learning' parts of the game happen. :)

Andy


Got my BITX40 Yeay!!

Tony Franco
 

Mr. USPS delivered my BITX40 today..


Appears to have survived the trip.  Packaging took a beating but it looks intact.


Will post pic's of packaging.


TonyF, K6ALF

Re: Si5351 VFO - Low Pass?

 

Andy,

Mine was noisier too until I put a LPF inline with the Si5351. I got the idea here. Scroll down the page a ways to find the filter table.

On Jan 4, 2017, at 5:01 PM, ahecker@... [BITX20] <BITX20@...> wrote:

 

I noticed that my receiver got noisier when I disconnected the built-in VFO and added the Si5351.  I get that a filter re-shapes the waveform, but I'm wondering about whether it's useful to clean the output signal a bit before injecting it into the radio.



I guess this is where the 'experiment' and 'learning' parts of the game happen. :)

Andy

Re: Si5351 VFO - Low Pass?

AndyH
 

I noticed that my receiver got noisier when I disconnected the built-in VFO and added the Si5351.  I get that a filter re-shapes the waveform, but I'm wondering about whether it's useful to clean the output signal a bit before injecting it into the radio.


I guess this is where the 'experiment' and 'learning' parts of the game happen. :)

Andy

Re: missing c103

AndyH
 

You're welcome!

   Sorry...this didn't appear to mention C103...I forget where he covered the purpose of that.  Sorry also for missing an H in Ashhar's name. 


---In BITX20@..., <billy.shepherd@...> wrote :

Thanks so much!











[Non-text portions of this message have been removed]

Re: It stopped transmitting

Bill Kittilson <bill@...>
 

I replaced q13 ( wasn't every easy for my old eyes) it fixed the problem.  I now have normal output power.  Thanks guys. 





On Jan 3, 2017, at 10:54 PM, jgaffke@... [BITX20] <BITX20@...> wrote:

 

I'd expect a 2n3904 to work fine at Q13, it looks a little tougher than the BC849.

A 2n2222 could work too, and be tougher still.
Though I haven't fully analyzed the circuit, and am very curious why two units have failed here. 

After removing the old Q13, I suggest you measure ohms from the emitter pad to ground (make sure that 100 ohm resistor isn't shorted out somehow which would cause excessive collector current)
Verify that there's 100 ohms from the R136 side of C134 (if that coil current has nowhere to go when Q13 turns off then the Q13 collector voltage will rise way up and blow the transistor.)
Then power it up and hit the PTT button, see if the bias at the base pad is around 3.8v (this bias is determined by the 2 resistors: 470 * 12v/(1k+470)  = 3.8v)
Check all those parts for cold solder joints that might open up when the board it flexed.
Then install the new transistor, see if it works. 

Jerry, KE7ER


---In BITX20@..., wrote : 
What's a good replacement? 2N3904? 

Re: missing c103

Billy Shepherd <billy.shepherd@...>
 

I looked around for something like that video…hidden in plain sight. Thanks again and sorry for being such a newb.

Billy

From: BITX20@... [mailto:BITX20@...]
Sent: Wednesday, January 04, 2017 7:23 PM
To: BITX20@...
Subject: [BITX20] Re: missing c103



Billy - Ashar's receiver troubleshooting video gives an overview of the board and talks about where and why some of the parts might be missing. My recent pre-Raduino didn't need C103 either.

Cheers,
Andy


Troubleshooting the BITX40 board's receiver<https://www.youtube.com/watch?v=R8G8XAwq38A>


[Image removed by sender. image]<https://www.youtube.com/watch?v=R8G8XAwq38A>

Troubleshooting the BITX40 board's receiver <https://www.youtube.com/watch?v=R8G8XAwq38A>
A short video showing how to troubleshoot the receiver of the BITX40 with a piece of wire

View on www.youtube.com <https://www.youtube.com/watch?v=R8G8XAwq38A>

Preview by Yahoo

Re: missing c103

Billy Shepherd <billy.shepherd@...>
 

Thanks so much!


From: BITX20@... [mailto:BITX20@...]
Sent: Wednesday, January 04, 2017 7:23 PM
To: BITX20@...
Subject: [BITX20] Re: missing c103



Billy - Ashar's receiver troubleshooting video gives an overview of the board and talks about where and why some of the parts might be missing. My recent pre-Raduino didn't need C103 either.

Cheers,
Andy


Troubleshooting the BITX40 board's receiver<https://www.youtube.com/watch?v=R8G8XAwq38A>


[Image removed by sender. image]<https://www.youtube.com/watch?v=R8G8XAwq38A>

Troubleshooting the BITX40 board's receiver <https://www.youtube.com/watch?v=R8G8XAwq38A>
A short video showing how to troubleshoot the receiver of the BITX40 with a piece of wire

View on www.youtube.com <https://www.youtube.com/watch?v=R8G8XAwq38A>

Preview by Yahoo

Re: missing c103

AndyH
 

Billy - Ashar's receiver troubleshooting video gives an overview of the board and talks about where and why some of the parts might be missing.  My recent pre-Raduino didn't need C103 either.

Cheers,
Andy


Troubleshooting the BITX40 board's receiver

 



missing c103

Billy Shepherd <billy.shepherd@...>
 

Missing C103 (the potentiometer  for the balanced modulator) from my recently received Bitx40. Is this normal? Mine is the unit without the Raduino. If it’s an error would adding it myself be considered a novice task? Thanks.

 

Billy

 

Re: Si5351 VFO - Low Pass?

Mark Baldridge
 

Very informative.

On Wed, Jan 4, 2017 at 4:55 PM, steve@... [BITX20] <BITX20@...> wrote:
 

The diode-ring mixer operates by switching the RF signal straight through to the IF port on one half-cycle of the local oscillator, then switching an inverted version of the RF signal through to the IF port on the next half-cycle. It doesn't depend on the non-linearity of the diodes for its operation - it treats them as switches. Best inter-modulation performance comes from keeping the diodes hard on or hard off, minimizing the time for which they are in an intermediate state.

Steve G3TXQ




--
Mark Baldridge
608.561.3853

Re: the arrival

Billy Shepherd <billy.shepherd@...>
 

December 16th. Waiting to here back…the potentiometer for the balanced modulator is missing…not sure if this is just a redesign. Mine came without the Raduino.

Billy Shepherd
Bartholomew Co 911 Center
131 S Cherry St.
Columbus, IN 47201

From: BITX20@... [mailto:BITX20@...]
Sent: Wednesday, January 04, 2017 5:52 PM
To: BITX20@...
Subject: Re: [BITX20] the arrival


Great! What date did you order it?

Rich
KC8MWG

On Wednesday, January 4, 2017 2:13 PM, "Billy Shepherd billy.shepherd@... [BITX20]" <BITX20@...> wro te:


2 weeks to ship for free from India to Indiana, awesome!
[cid:image001.jpg@...][cid:image002.jpg@...]
[cid:image003.jpg@...]

Re: Si5351 VFO - Low Pass?

Steve Hunt
 

The diode-ring mixer operates by switching the RF signal straight through to the IF port on one half-cycle of the local oscillator, then switching an inverted version of the RF signal through to the IF port on the next half-cycle. It doesn't depend on the non-linearity of the diodes for its operation - it treats them as switches. Best inter-modulation performance comes from keeping the diodes hard on or hard off, minimizing the time for which they are in an intermediate state.

Steve G3TXQ

Re: the arrival

Richard Andrew Knack
 

Great! What date did you order it?

Rich
KC8MWG


On Wednesday, January 4, 2017 2:13 PM, "Billy Shepherd billy.shepherd@... [BITX20]" wrote:


 
2 weeks to ship for free from India to Indiana, awesome!
[cid:image001.jpg@...][cid:image002.jpg@...]
[cid:image003.jpg@...]

[Non-text portions of this message have been removed]



Re: Band Pass Filter High Attenuation

Mark Baldridge
 

Okay. That is helpful information.

A couple questions: 

1: Can I assume that I will for the most part tune the inductors together? To make the correct bandpass, they must all be the same value, right?

2: Can I attach a 50 ohm spectrum analyzer as I showed in the link? Or will the impedance mismatch cause the filter to not function properly?


On Tue, Jan 3, 2017 at 12:41 AM, iam74@... [BITX20] <BITX20@...> wrote:
 

As I recall, this BPF is about 200 ohms in and out. If you used the IF transformers supplied with the kit, suspect first the coils of these transformers.  They are quite fragile and it is easy to get a poor or nonexixtent connection through them.

First, were they oriented right?

Second, it is easy to pull one of the pins out of alignment and even break the connection internally. Check them very carefully.

Third, there is a specific and quite narrow window which creates the bandpass. Triple check your alignment. The proper final inductance should be about 4 uH (for 20m).

Hope this helps.

john
AD5YE


---In BITX20@..., wrote :

Greetings all.

I seem to have an issue with my Band Pass Filter.

This was built using the components from Sunil Lakhani on eBay.

----

The entire schematic is here: 




--
Mark Baldridge
608.561.3853

Re: Si5351 VFO - Low Pass?

Mark Baldridge
 

THIS WAS MY QUESTION ALSO. Very curious what people have to say. :)

On Wed, Jan 4, 2017 at 2:49 PM, steve@... [BITX20] <BITX20@...> wrote:
 

Isn't it better to drive a diode-ring mixer with a square-wave local oscillator? You're wanting to switch the diode pairs hard on, then hard off.

Steve G3TXQ




--
Mark Baldridge
608.561.3853

Re: BITX40: Delay of PTT, RX amp keeps active too long

Jerry Gaffke
 


I doubt my previous suggestion of "Swap  pins 3 and 5 of relay K2, add a 100k resistor from K2-1 to ground" would do anything but make the transition noisier.