Date   
Re: Are these output watt rating crazy?

 

Hi Jerry,

Thank you for the information on the code.  Here is a simulation of the 750nH filter:



It looks like a good filter for 30m and 40m.  Input impedance showed 50 ohms on 30m and 40 ohms on 40m.

Sorry the image isn't bigger -- in linux the filter program only prints to either a printer or to "Microsoft XPS Document Printer" which I don't have going in linux so I have to do a screenshot.

Cheers,


Mark.

FLDIGI setup

John Faivre
 

I use omnirig with com3 to communicate with WSJTx but I cannot get Hamlib to connect
--
John Faivre WA9SGD

Re: Are these output watt rating crazy?

Bill Cromwell
 

Hi,

I haven't had any luck on 160 meters so far due to a compromised antenna. But rest assured that I am using and external low pass filter that starts to rolloff a little above 2 MHz. The filters inside the radio are definitely *not* for 160 meters.

It hears pretty well on 160 for all I can tell:)

73,

Bill KU8H

On 11/11/19 12:07 PM, Jerry Gaffke via Groups.Io wrote:
---snip-----
However, the stock uBitx definitely does not have a low pass filter appropriate for 160m !!!!!
We've had a number of folks here who assumed it did, since the firmware allowed them to spin down and transmit on 1.8mhz.
The third harmonic of 1.8mhz at 5.4mhz will go out on the air almost as strong as the fundamental.

--
bark less - wag more

Re: Are these output watt rating crazy?

Jerry Gaffke
 

Mark,

Interesting.   

You might be right that the filter with the 900nH inductors has an incorrectly implemented corner frequency.
Worth exploring further.
Your simulation shows a corner at around 7mhz, not the expected 5mhz.
That would let a 3.5mhz second harmonic leak by.
The second harmonic will be quite weak due to the push-pull topology of the IRF510 finals,
this 7mhz corner may not matter.

However, the stock uBitx definitely does not have a low pass filter appropriate for 160m !!!!!
We've had a number of folks here who assumed it did, since the firmware allowed them to spin down and transmit on 1.8mhz.
The third harmonic of 1.8mhz at 5.4mhz will go out on the air almost as strong as the fundamental.

The filter with the 900nH inductors that you simulated is definitely the lowest LPF on the uBitx.
When I said it had a 5mhz corner, I was going by Farhan's circuit description notes.
I had assumed this had been gone over thoroughly, since lots of folks in the forum
were trying to figure out how to reduce the problematic v3 harmonics from leaking past the relays.

I don't think the apparent 7mhz corner you found has anything to do with lack of power on 40m as seen by some.
I think it is more likely that some of the uBitx boards have incorrectly wound 750nH inductors.
When operating on 40m, both the v3 and v5 versions of the uBitx are using the LPF with the 750nH inductors.
At least, when operating with Farhan's code as archived on github.
There are other firmware releases out there, but I suspect they mostly copied
the code to control the LPF relays from Farhan.



Here's the v3 schematic:
  https://github.com/afarhan/ubitx/blob/master/ubitxv3.pdf

And here's the v3 code from
  https://github.com/afarhan/ubitx/blob/master/ubitx_20/ubitx_20.ino
that switches the relays around to select an appropriate LPF:

void setTXFilters(unsigned long freq){

  if (freq > 21000000L){  // the default filter is with 35 MHz cut-off
    digitalWrite(TX_LPF_A, 0);
    digitalWrite(TX_LPF_B, 0);
    digitalWrite(TX_LPF_C, 0);
  }
  else if (freq >= 14000000L){ //thrown the KT1 relay on, the 30 MHz LPF is bypassed and the 14-18 MHz LPF is allowd to go through
    digitalWrite(TX_LPF_A, 1);
    digitalWrite(TX_LPF_B, 0);
    digitalWrite(TX_LPF_C, 0);
  }
  else if (freq > 7000000L){
    digitalWrite(TX_LPF_A, 1);
    digitalWrite(TX_LPF_B, 1);
    digitalWrite(TX_LPF_C, 0);
  }
  else {
    digitalWrite(TX_LPF_A, 1);
    digitalWrite(TX_LPF_B, 1);
    digitalWrite(TX_LPF_C, 1);
  }
}
 
So when operating on 40m (unless you are tuned to be exactly on the lower band edge, don't do that!),
the signals A,B,C  (driving the KT1,KT2,KT3 relays) are driven with 1,1,0 respectively.
KT1 and KT2 are in bypass mode (relay on), and KT3 (off) selects the 7mhz LPF (has 750nH inductors).
So no, on a v3 uBitx, the LPF with the 900nH inductors is only used when operating below (or exactly on) 7mhz.

The v5 uBitx wires up the relays much differently to avoid having harmonics leak around the relays.
    file:///home/chronos/u-ba688dba5e13d507cb8c8d472169a2b5e212d72b/MyFiles/Downloads/ubitx_v5.pdf
The code for v5
    https://github.com/afarhan/ubitx_v5/blob/master/ubitx_v5.1_code.ino
drives the LPF relays with A,B,C == 0,1,0  when operating in the 40m band:

  else if (freq > 7000000L){
    digitalWrite(TX_LPF_A, 0);
    digitalWrite(TX_LPF_B, 1);
    digitalWrite(TX_LPF_C, 0);
  }
This powers the middle relay on the v5 to select the filter with the 750nH inductors,
the other two relays are left unpowered in bypass mode.
Note that the highest freq LPF with the 330nH inductors (for 15m,12m,10m) is always inline on the v5.

Jerry, KE7ER




On Sun, Nov 10, 2019 at 09:08 PM, Mark - N7EKU wrote:
I used the AADE filter simulation/design program.  I posted because I had seem some comments on the power outputs and was curious to simulate the low filter to see if that might impact some of the power levels.  I simulated the lowest filter I saw on the ubitx v3 schematic.  Did I miss a lower one?  This one seems to be the lowest and used for both 40m and 80m with a cutoff very close to 7MHz (actually showed -2dB at 7.3MHz).

Re: S meter locking up

Maurice Bersan
 

SOLVED
I just saw a post by a clever person who discovered a wiring error in the wiring diagram.
I am using one of those universal case kits by inkits with the extra front mounted circuit board for Ptt, audio and CW.
The volume high wire that goes to the volume pot is not the black wire, it's the brown one. The connections diagram appears to be incorrect. I have swapped the two wires and the problem is fixed. I think the post was on Facebook but I can't find it again, so whoever that clever person is, thankyou!
Maurice
Vk6hly

S meter locking up

Maurice Bersan
 

I have just installed a nextion 2.8 screen to my ubitx v5 and I noticed when I tap the screen to select, the s meter shoots up to s8 and sticks there until I either reboot or speak loudly into the mike. I have tried both TFT files with and without s meter but still the same fault. No problems with the old 2 line display screen. I have the kit projects ALC board fitted which works fine with the 2 line display.
Any ideas folks?
Maurice
Vk6hly

Re: Wiring question - Nextion case

Ian Reeve
 

This is true,my board came with the 4k7 resistor and the wire link in place but not soldered.


From: BITX20@groups.io <BITX20@groups.io> on behalf of Robert Freeman <michmasher@...>
Sent: Sunday, November 10, 2019 10:59:30 PM
To: BITX20@groups.io <BITX20@groups.io>
Subject: Re: [BITX20] Wiring question - Nextion case
 
If you want audio into both sides of the headphones, a jumper needs to be soldered from one side to the other.  

73s de NQ0T, Robert

Re: Nextion 5" display noise #noise #ubitx #nextion

MVS Sarma
 

I had simar issue even wirh 2.8 nextion.

 I placed a 2uH inductor in series with 5v line goingbto nextion and a decoupling capacitor of 100uF16v at the nextion side to ground.  

That has reasonably reduced the rumbling noise created after introduction of Nextion display.  Hope it helps.

Sarma vu3zmv




On Mon, 11 Nov 2019, 9:54 am Justin Phillips K5AXL, <dolmdemon@...> wrote:
I have a v5 uBITX in Sunil's 5" case with audio amp kit. Audio sounds just fine until I power the Nextion display. It's got a terrible buzz, and you can hear digital noises when the display changes, or when you turn the encoder. 

I've run separate power for the display and the noise remains. I Also tried powering the display with a battery pack, the noise is just as bad. How do you get this noise out? 

Also, my audio (when not influenced by the display) sounds very tinny and a bit high pitch, and it doesn't seem to change when adjusting the BFO much at all.. any ideas?

Re: Nextion 5" display noise #noise #ubitx #nextion

Mike Kilpatrick
 

My long lost twin brother !

 

 

From: Justin Phillips K5AXL
Sent: Monday, November 11, 2019 16:38
To: BITX20@groups.io
Subject: Re: [BITX20] Nextion 5" display noise #ubitx #nextion #noise

 

So, what has two thumbs and is a huge doomarse? <- this guy.

I was on LSB but adjusting the USB setting. 95% of the display noise is gone now.

 

Re: Nextion 5" display noise #noise #ubitx #nextion

Justin Phillips K5AXL
 

So, what has two thumbs and is a huge doomarse? <- this guy.

I was on LSB but adjusting the USB setting. 95% of the display noise is gone now.

Re: Are these output watt rating crazy?

 

Hi,

I used the AADE filter simulation/design program.  I posted because I had seem some comments on the power outputs and was curious to simulate the low filter to see if that might impact some of the power levels.  I simulated the lowest filter I saw on the ubitx v3 schematic.  Did I miss a lower one?  This one seems to be the lowest and used for both 40m and 80m with a cutoff very close to 7MHz (actually showed -2dB at 7.3MHz).

Yes the design environment is 50 ohms.  That does not mean the filter will show that for all frequencies.  At the design frequency, they should show that (as this one does for 40m).  At other frequencies they can present higher or lower impedances which will affect power output.  This one does also show around 50 ohms at 80m.  However at 60m it shows to be about 20 ohms and at 160m about 10 ohms.  Even using another filter on the output, with this filter inline it may cause trouble.  So it would be best to have a designed 160m filter linked directly to the output of the PA if one wants to use that band.  My thoughts anyway.

Of course it would be good to see an actual measurement of the filter with a VNA etc.  My equipment is packed away from a move at the moment so I have to rely on software at the moment.

I just thought people may be interested in what I had found.   I can work on my own no problem.




Cheero,


Mark.

Nextion 5" display noise #noise #ubitx #nextion

Justin Phillips K5AXL
 

I have a v5 uBITX in Sunil's 5" case with audio amp kit. Audio sounds just fine until I power the Nextion display. It's got a terrible buzz, and you can hear digital noises when the display changes, or when you turn the encoder. 

I've run separate power for the display and the noise remains. I Also tried powering the display with a battery pack, the noise is just as bad. How do you get this noise out? 

Also, my audio (when not influenced by the display) sounds very tinny and a bit high pitch, and it doesn't seem to change when adjusting the BFO much at all.. any ideas?

Re: Are these output watt rating crazy?

Jerry Gaffke
 

Mark,

I assume you posted to this old thread because
you wanted to tell us about your simulation results.

Yes, the uBitx should not be used on 160m without a suitable LPF
inline with the antenna.  Without that LPF the third harmonic will be
nearly as strong as the fundamental.

Not sure exactly how you went about simulating the filter
or exactly what corner frequency you saw.
Regardless of what your filter program thinks, the 80m LPF
is being used in a more or less 50 ohm environment.
Changing the impedances will change the frequency response.

Attenuating some harmonic by 13dB may or may not be sufficient.
If that particular harmonic coming out of the final amp is already 30dB down
from the fundamental, then the extra 13dB of attenuation from the filter
will be sufficient to meet FCC regs.  Due to the push-pull configuration
of the IRF510 final, it is mostly the 3rd harmonic that gives us grief.

Would be interesting to measure (not simulate) the response of the 80m LPF
using something like the Antuino, driving the filter from a 50 ohm source
and terminating it into 50 ohms.

I believe the 3dB corner frequency of the 80m LPF is around 5mhz,
so if you tried to use it on 40m you would not be putting out much of a signal.
 
Here's the post you quoted    https://groups.io/g/BITX20/message/68292
It happens to be in the same thread as our current conversation,
though this thread hasn't been active for over 6 months.,

Jerry, KE7ER


On Sun, Nov 10, 2019 at 05:30 PM, Mark - N7EKU wrote:
Jerry Gaffke
Apr 25  
The 80m LPF is also used for 60m, so the cut-toff freq is high enough to pass the third harmonic of 160m.This is not a sine wave:    https://groups.io/g/BITX20/message/48122
Hi,

I just entered the lowest ubitx LFP into a filter program and see that it is actually a 40m LPF.  It has a pretty good cutoff, so it cuts off what it need to for 60m and 80m, but would do almost nothing for 160m as it won't cutoff anything until the 4th harmonic and will only do about a 13dB cut there so not really effective until the 5th harmonic.  So basically useless on 160m.

Besides that, the input impedance to the filter on 160m comes out to about 10 ohms so not what the PA is designed to see.  On 60m it shows as 20 ohms a little better, but not great.

73,


Mark.

Re: Wiring question - Nextion case

mgassman@...
 

Thanks guys. 


I ran into the front panel board problem - after I’d soldered the board (I built it first since it was “simplest”j.  The front of the jacks are set back from the edge of the board.  Thankfully, I have a Dremmel and the trace was far enough from the edge that I could ground the board back so things would fit. 

Looking at the pictures for powering the audio amp, agc board and fan (and expecting to add a CW filter later), I’m not crazy about having all those wires soldered to the small contacts below the relay on the bottom of the ubitx board.  I’m thinking about pulling gnd, 12v xmit and 12v rcv to a terminal strip so I can add only one wire each below the board and connect the 3-4 others on the strip. 

Re: Are these output watt rating crazy?

 

Jerry Gaffke
Apr 25  
The 80m LPF is also used for 60m, so the cut-toff freq is high enough to pass the third harmonic of 160m.This is not a sine wave:    https://groups.io/g/BITX20/message/48122
Hi,

I just entered the lowest ubitx LFP into a filter program and see that it is actually a 40m LPF.  It has a pretty good cutoff, so it cuts off what it need to for 60m and 80m, but would do almost nothing for 160m as it won't cutoff anything until the 4th harmonic and will only do about a 13dB cut there so not really effective until the 5th harmonic.  So basically useless on 160m.

Besides that, the input impedance to the filter on 160m comes out to about 10 ohms so not what the PA is designed to see.  On 60m it shows as 20 ohms a little better, but not great.

73,


Mark.

 

Re: Wiring question - Nextion case

Robert Freeman
 

If you want audio into both sides of the headphones, a jumper needs to be soldered from one side to the other.  

73s de NQ0T, Robert

Re: Using Vacuum Tube heathkit as Linear Amplifier for QRP

Robert D. Bowers
 

I've played around with a Kenwood TS520... using a softrock connected in through the filter board.  The combination was in a word AWESOME... if a different radio even thought on frequency, I probably would have heard it (voice QRM became the limiting factor - static and hiss less of a barrier).  I plan on eventually using the softrock as an IF and the filters (and so on) for transmission.  The good thing is that the tuned circuits in the old radio are going to greatly improve the signal, one way or another.  In fact, they should be at least as clean as the best modern unit.

There are more powerful old tube rigs 'out there' - I can think of a KW rig right now that would be awesome as an amp (plus great filtering) for a BitX (or softrock).

Right now I'm trying to get something on the air with 2m SSB/FT8.  Then other projects will follow...

Bob

On 11/9/19 5:01 PM, Gordon Gibby wrote:


Finally got a chance to try my idea of using a heathkit ssb rig as a power amplifier for a QRP rig.   I've seen "amplifiers" for these rigs going for many hundreds of $$$.  I happen to be swimming in ancient heathkits with 2x6146 linear finals and tuned plate circuits on the driver as well (all good for getting rid of unwanted harmonics.....)

Allison gave some much needed advice on this crazy idea months back, and I finally got the chance to try it:

1 watt output from an exciter [I used an icom 718 that was readily availalbe] -- my only "power measurements" are ancient SWR meters with built in diode detectors so these measurements may be fairly INaccurate.

coax over to a 49:1 homebrew balun our group made for matching resonant half-wave antennas:   ours is a simple autotuner with 14 turns total of #18 teflon wire around a FT-240-43 (or FT-140-43) tapped at turn 2 to give us 7:1 turns ratio, 49:1 impedance ratio, and that checked out roughly with an antenna analyzer and some resistors

I loaded the output with 2500 ohms (temporarily made out of 4 10K resistors in parallel because that is all i had)
output of that via 6 inches of small coax to a 0.01 1kv ceramic capacitor connecting to the PLATE circuit of the removed 6CL6 driver, and to a nearby ground.

Output tested only with very brief bursts of CW -- on 80 meters and 20 meters, got approx 40-50 watts output measured also with an ancient swr meter/wattmeter into a 50 ohm load, everything on the Heathkit peaked for output.   Plate current rose appropriately.   Tuning circuit all appeared appropriately.

No obvious signs of any instability in this pilot test.    
Did not make any measurements with spectrum analyzer.   (In due time......)

That heathkit has other problems elsewhere but the finals appeared in fine shape.   Earlier VERY CRUDE measuresments with a siglent oscilloscope and some math suggested that the drive required at the INPUT to the 6CL6 stage would be less than 100 milliwatts, and that the drive required at the output of 6CL6 would be in the single digit watts range.    The above test appears to confirm those crude measurements.   Since it appeared the two 6146's could be driven adequately with single digit watts I opted to temporarily just remove the 6CL6 driver and connect to its (DC powered!!!!!!!  High voltage!)  plate circucit with a 1kv .01 blocking capacitor.   

Quite pleased with this very very initial test.   
At some point I'll repeat with a uBitx, but that's all for right now.
Gordon Gibby

Attachments:


Re: Wiring question - Nextion case

Ian Reeve
 

The pcb does need a little talc to make everything fit.The connectors I suggest are not soldered in until the jacks are fitted and a assembly dry run done.on mine the edge of the pcb needed to be filed back to ensure jacks sufficiently poke through to be fixed with the round threaded fixings.Once that is done assemble the connectors and make sure there is sufficient room for the main pcb.Again on mine the holes for some connector pins was not in perfect alignment.Hope this helps


From: BITX20@groups.io <BITX20@groups.io> on behalf of Justin Phillips K5AXL <dolmdemon@...>
Sent: Sunday, November 10, 2019 9:41:13 PM
To: BITX20@groups.io <BITX20@groups.io>
Subject: Re: [BITX20] Wiring question - Nextion case
 
On an aside, if you haven't assembled the front panel board yet make sure you solder the digital and analog sockets pulled back towards the edge as much as you can. And when you solder the jacks on, make sure they're pulled forward as much as you can, however much play in the holes you have. Mine is so tight i have to press the harnesses in and a bit of an angle to squeeze them in behind the jacks. The jacks are so far back i couldnt get the nuts to get any thread, I wound up using the old ones from the stock ubitx kit, they seemed to get more thread to bite.

Re: Wiring question - Nextion case

Justin Phillips K5AXL
 

On an aside, if you haven't assembled the front panel board yet make sure you solder the digital and analog sockets pulled back towards the edge as much as you can. And when you solder the jacks on, make sure they're pulled forward as much as you can, however much play in the holes you have. Mine is so tight i have to press the harnesses in and a bit of an angle to squeeze them in behind the jacks. The jacks are so far back i couldnt get the nuts to get any thread, I wound up using the old ones from the stock ubitx kit, they seemed to get more thread to bite.

Re: Wiring question - Nextion case

Justin Phillips K5AXL
 

Yes, which is normally connected to pins 5/2 of the phones jack when no plug is inserted, completing the connection to pin 7 on analog J1 connection. Inserting a plug disconnects J4 (if im observing it correctly). Mine is wired this way and I have audio to the amp with no plug in the jack and no audio to the amp/speaker with phones plugged in.