Date   
Re: No Boot-Up (after spikes)

Sam Tedesco
 

Nextion shows callsign/ver and all zeros on freq?

Re: No Boot-Up (after spikes)

Ted
 

Thanks for the tip, John.  Thing is that I've tried no fewer than four Nano replacements and two other, known operational Raduino boards.  That's the part that makes no sense. Bad outputs or clock readings should have been eliminated by now due to component-swapping.

But I will look at readings for the experience & to learn more about these things.


Tnx agn,

Ted
K3RTA

Re: No Boot-Up (after spikes)

John (vk2eta)
 

Hello Ted,

Sorry about the mishap, but it has happened to quite a few of us before.

I would try the Raduino off the main board but connected to a PC for supply via USB.

If it is gets stuck at firmware version I would suspect either a defective si5351 clock generator or an issue with the i2c bus (A4/A5 from memory). Check for shorts, and if you have a scope check that you get a 3.3v swing on the two i2c signal wires.

73, John

Re: Attenuator function in CEC firmware #nextion #ubitx #firmware

Tom, wb6b
 

On Thu, Apr 18, 2019 at 04:26 PM, Jerry Gaffke wrote:
You could easily control that attenuation from a processor, perhaps
These may be a little overboard for the purpose but I have one of each of these digitally controlled attenuators that I bought to build up my tool set for making RF measurements. 

This one had the part number of the attenuator chip ground off. Depending on the manufacture of the part, the specified low frequency cutoff could be 9Khz, 1Mhz or 10Mhz. For HF measurements a possible 10Mhz cutoff is an issue.
https://www.ebay.com/itm/New-OLED-6G-Digital-Programmable-Attenuator-30DB-step-0-25-RF-Module-Micro-USB-/263584061842
However, the construction with the machined aluminum body is impressive.

This one specifies the part number in the description and the number on the attenuator chip matches. It is a 9Khz to 4Ghz attenuator. It doesn't have a display, so would be a better choice for installing into the uBitx. 
https://www.ebay.com/itm/PE4302-Digital-RF-Step-Attenuator-Module-High-Linearity-0-5dB-50-ohm-RF-DSA/121830578745

You can also buy the current version of the Peregrine attenuator chip from Digikey, mount it on a SMD adaptor board and add it to your uBitx IF chain. But, the modules are easier to work with.

These parts have an actual 50 ohm impedance (when the other end is 50 ohm terminated). It might be that the 50 ohms is a bit more load that the IF chain was designed for. 

Tom, wb6b


 

No Boot-Up (after spikes)

Ted
 

It came to pass that,  in the process of inserting a 7809 between the Raduino daugterboard and its B+ pin-to-mainboard, that I failed to notice a solder blob shorting out the 7809. I made a 90-degree header change at the Raduino mounting point on this build, making this relatively painless [or not].

It was realised, when turning on the (1-metre-long) remote power switch whereupon an added power relay chattered on and off [due to low relay supply voltage for the instant of the short],  graciously saving my 5-amp fuse.   Don't ask....

Since then, the radio powers up but the Nextion screen would not get past simply powering on and showing the basic screen graphics (as if in the PC editor). The obvious have been performed:

- Replace Nano.
- Try different brand of Nano
- Try Nextion screen from redundant uBitx radio
- Replace Raduino (in stock, known)
- Replace 5-volt regulator on oruginal Raduino.
- Swap Raduino from redundant uBitx radio
- Try swapped Raduino with different Nano
- Restore Raduino with original, 2-line LCD display (shows opening call sign and firmware edition, nothing more)

So: should not a Raduino board power up by itself when given 12v & (-) , and respond to the original LCD display or a Nextion screen, that is, respond to manual display inputs even without a mainboard present? 

If a mainboard is required for Rauino/screen operation past initial lighting, what might fail specifically which will stall further brain function like that? 

V3 board; whole rig seen in my Photos folder.


73,

Ted
K3RTA

Re: next ubitx

Ashhar Farhan
 

There are several ways to do this. ALC is just one way. An easier approach is to do it in software. This needs a software that can control the 'mic volume'. you could set the value differently for each band.

there is another pay-off with software mic gain, it can make a major difference to the tx IMD. At voice peaks, the tx linear chain compresses. The gain is not constant between low and high levels of modulation. This is what the in-channel IMD is. Now, if we have a look up table that amplifies the peaks more than the lows, we can 'correct' the gain back to being linear.  This simple concept goes by the name of 'pre-distortion' in the SDR world.

-f

On Thu, Apr 18, 2019 at 9:21 AM Jerry Gaffke via Groups.Io <jgaffke=yahoo.com@groups.io> wrote:
If you want to electronically adjust TX power out on the uBitx, talk to John, VK2ETA

He's got that working with no hardware mods for SSB:
    https://groups.io/g/BITX20/message/45781
and now with some minor mods for CW:
    https://groups.io/g/BITX20/message/67981
    
Jerry, KE7ER

On Wed, Apr 17, 2019 at 07:49 PM, Adrian Chadd wrote:
Honestly though, if we had an ALC input to drive low to decrease TX gain and thus output, we could create our own power control loopbacks and SWR protection. It'd make 100W operation less.. crazy.
 
(I'd like to do this, but I'm still diagnosing the basics on the v4 board; I'd like the TX drive out to be clean before i feed it into an amp and waste more power..)
 
 
-adrian

Re: Trial to control CW power (and reduce harmonics as a result) by unbalancing the 2nd mixer #ubitx

Joe Puma
 

I found another kit and info for the AD8307


Joe
KD2NFC


On Apr 19, 2019, at 12:08 AM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:

I like the display on the QRP Guys RF probe.
However, the input to the AD8307 is not well protected,
and any DC at the probe tip will blow the diodes.

Here's a cheaper AD8307 RF probe with what looks like a better front end, but no display:
    https://www.ebay.com/itm/RF-Active-Probe-0-1-500-MHz-with-AD8307-detector-/332405976109
Cheaper still, but without the better front end:
    https://www.ebay.com/itm/AD8307-RF-Power-Detector-Module-DC-to-500MHz-Transmitter-Power-Test-92dbm/263868813801



On Thu, Apr 18, 2019 at 07:03 PM, Jerry Gaffke wrote:
I'm liking the looks of this AD8307 RF probe, very clever how they make use of a cheap digital voltmeter module:
    https://qrpguys.com/qrpguys-digital-field-strength-meter

Re: Trial to control CW power (and reduce harmonics as a result) by unbalancing the 2nd mixer #ubitx

Jerry Gaffke
 

I like the display on the QRP Guys RF probe.
However, the input to the AD8307 is not well protected,
and any DC at the probe tip will blow the diodes.

Here's a cheaper AD8307 RF probe with what looks like a better front end, but no display:
    https://www.ebay.com/itm/RF-Active-Probe-0-1-500-MHz-with-AD8307-detector-/332405976109
Cheaper still, but without the better front end:
    https://www.ebay.com/itm/AD8307-RF-Power-Detector-Module-DC-to-500MHz-Transmitter-Power-Test-92dbm/263868813801



On Thu, Apr 18, 2019 at 07:03 PM, Jerry Gaffke wrote:
I'm liking the looks of this AD8307 RF probe, very clever how they make use of a cheap digital voltmeter module:
    https://qrpguys.com/qrpguys-digital-field-strength-meter

Re: Trial to control CW power (and reduce harmonics as a result) by unbalancing the 2nd mixer #ubitx

Jerry Gaffke
 

Signal level into the D1,2 mixer can be a bit higher than it is into the D3,4 mixer
when transmitting SSB.  But not by much.

Assume the D3,4 mixer has a signal loss of 6dB, the 45mhz crystal has a loss of 4dB,
and that the 2n3904 based v3,v4 uBitx 45mhz IF amp has a gain of 10dB.
(Gain is less than the designed for 16dB because the 2n3904's
can't give that much gain at 45mhz.  I have no idea what v5 does.)
We wind up with the same level of SSB signal into the D1,2 mixer
as we had going into the D3,4 mixer.  


On Thu, Apr 18, 2019 at 08:15 PM, John (vk2eta) wrote:
Yes that gives me good reference points. So assuming the clocks #1 and #2 are at the same level, it looks like after this mod the signal at T2 (3,5) could be around 10 to 16dB too high.

Re: Trial to control CW power (and reduce harmonics as a result) by unbalancing the 2nd mixer #ubitx

John (vk2eta)
 

Thanks Jerry,

Yes that gives me good reference points. So assuming the clocks #1 and #2 are at the same level, it looks like after this mod the signal at T2 (3,5) could be around 10 to 16dB too high.

I like that QRPGuys probe.

All the best,

73, John

Re: Confused about how AGC works?

Jerry Gaffke
 

A poorly designed AGC circuit could oscillate exactly as you describe.
Whether or not it will oscillate depends on the delays through each element
and the gain of each element.  Both can vary depending on the frequency
at which they are calculated. 
    https://en.wikipedia.org/wiki/Barkhausen_stability_criterion

Jerry, KE7ER



On Thu, Apr 18, 2019 at 06:00 PM, digger AB3XU wrote:
To begin with I can follow along with the theory and it does makes sense. Very simply, the signal from Vol-Hi via Q1 is used to control the conduction of Q2 and how much Q3 shunts the IF signal. Ideally RF levels below S9 are left relatively untouched, however if greater than that, the action of Q2 conducting less and Q3 acting as a shunt  results in reducing clamping (reducing) the IF level.

So here's where I get lost.  As the IF level gets attenuated by the action of the AGC doesn't that in turn:
  1. attenuate the level you will see at Vol-HI
  2. which will then decreases the effect of the AGC
  3. leading to an increased IF signal level
  4. and increasing Vol-HI
  5. which then increases the AGC's effect
  6. reducing the IF signal level
  7. resulting in a feedback loop of the IF level going up and down...
Am I describing my confusion/question in a way that makes sense?

73, digger AB3XU

Re: Menu Sequence for CEC Firmware v1.200 #ubitx #firmware

John (vk2eta)
 

Hello Dan,

After coffee the two and half neurons left seem to start working together..hihi: in fact you should only need to do the second part of the changes since the switch statement does not care about the order of tests. It is only a code optimization issue.

So only the #define FN_xxxx section should need to be adjusted.

73, John

Re: POP!!

Sam Tedesco
 

C97 was bad. Failing under load. PITA!

Re: Trial to control CW power (and reduce harmonics as a result) by unbalancing the 2nd mixer #ubitx

Jerry Gaffke
 

John,

Yes, the 45mhz crystal filter should strip out the harmonics coming out of that mixer,
leaving just a pure 45mhz carrier when transmitting CW

For SSB, both of the level 7 diode ring mixers want an incoming signal that is 10 dB or so below
the 7dBm local oscillator, so about -3 dBm max.  Beyond that it starts to distort. 
The output of the mixer is about 6 dB below the signal coming in.
The 45mhz crystal has a loss of 3 to 5 dB I'd think, the 45mhz IF amp has a gain
somewhere between 10 and 16 dB (the hot transistors on v5 might put that one 
closer to 16 dB).  

Of course, our si5351 can't quite deliver 7dBm, but the uBitx pushes things a bit, driving the mixers
hard because we don't have enough gain in the power amp.
Anyways, the paragraph above should get you in the right ballpark regarding signal levels.

I'm liking the looks of this AD8307 RF probe, very clever how they make use of a cheap digital voltmeter module:
    https://qrpguys.com/qrpguys-digital-field-strength-meter
That thing could be calibrated, you could read dBm from it using a hand calculator.
Better yet would be if the uBitx had pads for an optional AD8307 feeding a Nano analog pin.
There are AD8307 chips at $0.50 each on ebay, and they generally work fine.

Jerry, KE7ER
 


On Thu, Apr 18, 2019 at 05:23 PM, John (vk2eta) wrote:
Also please tell me if that statement is correct: since the clock #1 signal passes through the xtal filter this should strip its harmonics to pretty low levels (xtal filter overload excepted as you mentioned above. Not sure at what levels this starts occurring).

Re: Confused about how AGC works?

Curt
 

check this out - this is a similar version of the same circuit

http://www.nd6t.com/bitx/AGC

the main idea is sampling the audio, feeding the transistor to boost this signal.  the 2 diodes develop a rectified signal based upon the audio, and this is used to bias a MOSFET used as a variable resistor. 

Curt

Confused about how AGC works?

digger AB3XU
 

Hello All,

(sorry if this topic has been hashed to death elsewhere, if so I couldn't find it).

As the subject says I'm a bit confused about how AGC, and specifically the ND6T version, works. There must be something I'm missing because it doesn't make sense. Here's a link to the basic circuit and how it works.


To begin with I can follow along with the theory and it does makes sense. Very simply, the signal from Vol-Hi via Q1 is used to control the conduction of Q2 and how much Q3 shunts the IF signal. Ideally RF levels below S9 are left relatively untouched, however if greater than that, the action of Q2 conducting less and Q3 acting as a shunt  results in reducing clamping (reducing) the IF level.

So here's where I get lost.  As the IF level gets attenuated by the action of the AGC doesn't that in turn:
  1. attenuate the level you will see at Vol-HI
  2. which will then decreases the effect of the AGC
  3. leading to an increased IF signal level
  4. and increasing Vol-HI
  5. which then increases the AGC's effect
  6. reducing the IF signal level
  7. resulting in a feedback loop of the IF level going up and down...
Am I describing my confusion/question in a way that makes sense?

73, digger AB3XU

Re: Menu Sequence for CEC Firmware v1.200 #ubitx #firmware

John (vk2eta)
 

Hello Dan,

Not tested since I use my own customized version, so just by reading his code therefore that solution could be buggy but should point to what you need to do.

Example swap around the position of toggle VFO and Mode in the menu:

in ubitx_menu.ino change from:

#if FN_VFO_TOGGLE == 1
      case FN_VFO_TOGGLE_IDX :
        menuVfoToggle(btnState);
        break;
#endif       
#if FN_MODE == 1
      case FN_MODE_IDX :
        menuSelectMode(btnState);
        break;
#endif       

To (swap around):

#if FN_MODE == 1
      case FN_MODE_IDX :
        menuSelectMode(btnState);
        break;
#endif       
#if FN_VFO_TOGGLE == 1
      case FN_VFO_TOGGLE_IDX :
        menuVfoToggle(btnState);
        break;
#endif       

AND change from:

  #define FN_VFO_TOGGLE_IDX   (FN_BAND_IDX         + FN_VFO_TOGGLE)
  #define FN_MODE_IDX         (FN_VFO_TOGGLE_IDX  + FN_MODE)
  #define FN_RIT_IDX             (FN_MODE_IDX                  + FN_RIT)

To (re-sequence from menu item position to menu item position):

  #define FN_MODE_IDX                 (FN_BAND_IDX                + FN_MODE)
  #define FN_VFO_TOGGLE_IDX   (FN_MODE_IDX               + FN_VFO_TOGGLE)
  #define FN_RIT_IDX                      (FN_VFO_TOGGLE_IDX  + FN_RIT)

That should do the trick I suspect.

All the best,

73, John

Re: Trial to control CW power (and reduce harmonics as a result) by unbalancing the 2nd mixer #ubitx

John (vk2eta)
 

Thanks Jerry, all very good points.

I really need to invest in a scope and an SA.

I didn't notice any difference in the CW output power after this mod (but I didn't record the before power).

I will check if there is a difference between SSB and CW power levels. That should give me an indication.

Also please tell me if that statement is correct: since the clock #1 signal passes through the xtal filter this should strip its harmonics to pretty low levels (xtal filter overload excepted as you mentioned above. Not sure at what levels this starts occurring).

All the best,

73, John

Re: Attenuator function in CEC firmware #nextion #ubitx #firmware

Jack Brabham - KZ5A
 

Funny you should mention the ND6T AGC, I just got one in the mail today from kit-projects.com.

My uBITX V.5 will be here tomorrow (love the DHL tracking).  Nextion 3.5 has been here for a few days.

The nice Cheval SA case from Bangkok probably won't be here for a month.  Hopefully by then I will have figured out how many and what sized holes it needs where.

I intend to go thru stock operation for a while (probably a short while) before loading the CEC firmware, just so I can better appreciate the differences.

As far as the ATTN goes, I try to follow the wisdom of "If it ain't broke, don't fix it".  I may or may not decide it needs fixin',  as the approach obviously works but seems a little "non-optimal".  I'm not one to fret over increasing the parts count and the digital attn idea is very compelling.  We'll see, I've got a lot of learning curve to wade thru first.

73 Jack KZ5A











On 4/18/2019 5:26 PM, Jerry Gaffke via Groups.Io wrote:
The clever person is John, VK2ETA.
Here's where it started:
    https://groups.io/g/BITX20/topic/16737180
    https://groups.io/g/BITX20/topic/17009424

And we have an active thread right now about doing this with CW:
    https://groups.io/g/BITX20/topic/30997272

And a mention of it yesterday here:
    https://groups.io/g/BITX20/message/67982

It works by adjusting the si5351 to move the frequency at which the desired signal
hits the 45mhz crystal filter.  The filter has shoulders gradual enough that this serves
as an effective attenuator.  Works great for transmitting, where you set it once based
on the operating frequency and desired output power.  Using this method to dynamically
shape the receive attenuation would be sort of possible but not very satisifying
since there would be a pop heard every time the si5351 is updated.

There have been a half dozen different schemes for implementing simple AGC schemes
on the uBitx (and Bitx40).  I'd recommend Don's (ND6T) scheme as was kitted up
by Kees (K5BCQ).    http://www.nd6t.com/uBITX/AGC.htm
The kits are no longer available, but would be simple enough to dead bug it.
Others here will have their own favorites.
They pretty much all rectify the recovered audio to determine the amount of attenuation,
applying a DC voltage to some attenuation device.
You could easily control that attenuation from a processor, perhaps using pulse-width-modulation
to determine the amount of attenuation, though better would be an small ADC hanging off the I2C lines.

Jerry, KE7ER


Re: Attenuator function in CEC firmware #nextion #ubitx #firmware

Jerry Gaffke
 

Good, thanks for the correction.
And good to know the ND6T scheme is still available as a kit.

I think I probably knew that once, but I'm not sure I can remember even that!

Jerry


On Thu, Apr 18, 2019 at 05:10 PM, KE2GKB wrote:

Just to comment here and pass some info on, Don's (ND6T's) AGC is available as a kit from N8DAH and my Self over at https://shop.kit-projects.com We are still working on talking to Don to get him to update his web page. We have his blessing but nothing has been updated yet on his end.

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