Date   
Re: Harmonic performance - SSB vs CW

ajparent1/kb1gmx
 

Warren,
I it was soemthing easy to try but I'd call it the same as you.  Lots of harmonics
in square waves and little filtering.   

At frequencies below 20MHz the filters at the amp output are the only filter.
Not my favored way, either. 

If there were band pass filters at the amp input this would not be an issue
nor would spurs be an issue.

One way and likely there are many:
An improvement is to move the keying (CW_TX) to the product detector/ TX modulator
and move the BFO to the edge of the pass band and key that.    The easy way is
remove R105  and run a wire from the junction of C1/R104 under the board to
a replacement R105 at the modulator junction C222-1 and the transformer T7.   
Then both the 12 and 45mhz filters can clean it up.  That would be the wire changes.

Doing that requires a code change.  Actually any change that comes immediately
to mind requires that.    The code change would remove the mix of VFO switching
to only the BFO and the signal CW-key would drive the Balanced modulator.  That
works well as It has been done on many other radios.  Code is easier than solder.

Allison

Re: Harmonic performance - SSB vs CW

Warren Allgyer <allgyer@...>
 

The signal at TP1, the output of the first mixer is a pure square wave as it is derived directly from the Si5351 in CW mode. The signal in SSB mode is much closer to a sine wave as it is a mix of the Si5351 square wave and the 45 MHz drive that has been filtered by the roofing filter of Y1 and associated components. 

The only filter that the CW signal encounters before the output filters is the 30 MHz LPF between TP1 and TP2. It has a 2 dB point of about 34 MHz in my case so any harmonics below that are unattenuated until after the final.

The obvious way to fix this is to do the CW generation prior to the roofing filter. What is not obvious to me is the best way to do that. As it stands it is pretty messy.

WA8TOD

Additional Boards supplied with Case V3

Don Coulter
 

Hi everyone,
can anyone please supply the wiring diagrams or photos of the correct connections for thee small pcbs that came with my kit cant find any wiring details anywhere any help would be most gratefully received
73 de Don G4MTR

Re: RFI Problem related by routing audio through K3 (uBitx)?

Gwen Patton
 

From what I've been able to find, if it has silkscreened component locations, it's not a PWB, it's a PCB.

Most people use PCB nowadays.

http://www.circuitnet.com/experts/59367.html

Re: End Fed antennas w/ uBITX #ubitx

Chuck, N1KGY
 

On Tue, Jul 31, 2018 at 06:38 AM, Warren Allgyer wrote:
In actual operation these losses would be the best case and would be experienced only when the antenna is a resonant multiple of a half wave. The losses when not terminated in a 2470 ohm resistive load, which would be the case if the antenna were used on any band other than the single resonant band, are far higher. On the order of 8 - 10 dB.
Thank you Warren.  Your VNA and 'scope plots illustrate very clearly why in antenna literature, "all band" doesn't mean what most folks would have it mean - it almost always means "lossy".  Even commercial manufacturers have a difficult time producing a high transformation-ratio UNUN that operates across multiple octaves of frequency with acceptable losses - it's just not an easy set of design objectives to satisfy...  so for casual construction projects it a reasonable design constraint to limit (focus) yourself to making a transformer with minimal losses across ONE octave of frequency.  I.E 1.8~3.6Mhz; 6~12Mhz, and 14~28Mhz.  Even minimizing losses in the 14~28Mhz range can be challenging, due to the very high transformation ratio (1:49) - look very closely at your use case before choosing core materials -

Material #43 isn't  "the best" choice in many cases; in fact I try to avoid it whenever possible below 5Mhz and above 20Mhz because of it's high(er) losses. 
Material #61 yields lower losses than #43 for nearly every application in the 10~30Mhz; and Material #31 has lower losses than #43 in most applications at or below 5Mhz. 
In practical applications, the loss curves of materials #43 and #31 'cross each other' in the ~8Mhz range, so an UNUN | BALUN made for use on 40 Meters can utilize either core material and achieve a respectable loss figure, when all other design limitations are observed.

This is why I strongly recommend designing and building separate matching units for (80)/40/30 meters, and 20/17/15 meters - that way, each can be optimized for minimum losses in the specific band(s) it will be used on.

I would use matching techniques for 12/10/6 Meters which don't employ ferites or iron powdered toroids at all.  Air core coils and/or transmission-line sections are compact enough on these bands; yield very generous matched bandwidth figures; and have much lower losses when compared to the toroidal transformers [tuned and un-tuned] being discussed throughout this thread.

Cheers,
Chuck

Re: ubitx CW straight key wiring

Dave New, N8SBE
 

Wow.  I missed that completely by using the front panel PCB that came with the enclosure from amateurradiokits.in.

Seems like with online resources like that, the schematic and wire-up page could get updated.

Just sayin'...

73,

-- Dave, N8SBE

-------- Original Message --------
Subject: [BITX20] ubitx CW straight key wiring
From: dkuk@...
Date: Wed, August 01, 2018 9:29 pm
To: BITX20@groups.io

I've gone through 2 rounds of blowing finals before I finally found it mentioned that the wiring in the manual for the CW straight key was wrong.
It is also wrong on the website https://ubitx.net/wiring-up-a-paddle-and-straight-key/........
The resistor and blue wire must be wired to the upper right terminal in both pictures for it to work properly.
With the wiring as pictured my keyers essentially shorted the ring to the sleeve, hard keying the rig.

I would set up my keyer - plug it into the jack on the ubitx, then power the ubitx up,
unaware that as soon as I powered up, the ubitx was keyed until the finals finally fried.

This is the reference from the same web page mentioning the error in the schematic:
"There is an error on the circuit diagram and the wire up instructions for the CW Key.  The
diagrams show the key connected to pin 2 of the key jack. Pin 2 is the RING terminal, not the TIP."

Just wanted to put this out there in case anyone else is going through similar frustration.
I was so frustrated that I was ready to scrap my ubitx.

Re: experience with Sunil VU3SUA's enclosures #ubitx

Dave New, N8SBE
 

I found out that the MH3 mike that came with my KX2 works peachy plugged into the 3.5mm PTT/MIC jack.  No wiring, no fuss.  The up/down buttons, of course, don't work (they cause PTT), but otherwise, I won't have to come up with an adapter for anything.

So far, using my Picokeyer plugged in to the CW jack, and my Bulldog paddle for CW.  Works peachy, too.

Showed it off at the Detroit Maker Faire (special event station N8M) this past weekend, and it drew a lot of positive comments and questions.  Mine is dark green, and the green LCD sets it off nicely.  Left the lid off so everyone could see how it went together.

I'll be at the MI QRP club picnic this Saturday (1000 to 1400 ET), and running CW/SSB on likely 40 and 20 meters, using my Super Antenna on the picnic table with tuned counterpoise wires.

73,

-- Dave, N8SBE

-------- Original Message --------
Subject: Re: [BITX20] experience with Sunil VU3SUA's enclosures #ubitx
From: "Eddie Esserman" <ee@...>
Date: Wed, August 01, 2018 11:35 pm
To: BITX20@groups.io

Thanks Ian at ? for email.
Making good progress.  Don't think I will be using the digital connections on the back panel, but putting in the board.  Also switching from the panel.
Rest seems pretty well being resolved.  Need to find a good picture of the relay for the TX/RX LED connection.
And wiring the mic connector.  I'll learn Arduino on an easier board.  My first experience, and this is in place and seems to work.  That's another lesson.

Eddie

Re: click fix and squeal on transmit #ubitx

Ben AC1FG
 

Thanks, Don! In a surprise move, the problem turned out to be uncarefulness on my part. My confidence was misplaced, since I'd used wrong capacitors in a total of four places: both caps in the circuit were 10μf, not 10 nf, and my replacements for C50 and C63 were not polarized. Now that I've replaced all four with the correct caps, the squeal is gone. The click is still audible in the headphones when the volume pot is turned way up, but it's much less than before. I think I'm going to declare this a qualified success and put the radio back in its enclosure.

Re: Off Topic: Gap Antennas

Vince Vielhaber
 

If you can, put in 8.8.8.8 for your first name server and see if that does it. That's google's name server.

Vince - K8ZW.

On 08/02/2018 04:02 AM, DaveC wrote:
Thanks guys, Don't think it has anything to do with the EU privacy
issues also cleared out all cookies etc and no change.
It looks like a DNS issue and somewhere in the chain from the masters an
update error is occurring.

73 Dave G8PGO

Re: µB FT8 Success!

Rob Snow
 

I went a slightly different direction and picked up a cheap temp fan relay from Amazon:

https://www.amazon.com/gp/product/B00GWFK7FA

I superglued the probe to one of the finals heatsink and then played with ON temp and hysteresis temp, I settled on 50deg ON and 35deg OFF.  It was $5 for the fan relay + probe and ~$8 for a 12v 2wire fan.  Works great.

73 Rob de AG5OV

Re: click fix and squeal on transmit #ubitx

Don, ND6T
 

When the rig is not powered or in the receive mode there should be continuity from the Rx connection point to 12V. through relay K1 contacts 3 and 5. That is normal. The squeal is not!
First step in diagnosis is to check the voltage on the gate of Q3 when in transmit mode. It should be below 1 volt referenced to the ground connection on that board. If not, check to see that the ground connection there has the same potential as the ground plane of the BITX. Then track down the voltage discrepancy. The operation depends on Q3, acting as a gate, being turned off, thus opening that gate. If that gate is allowing the I/O (when in transmit, it is the microphone pre-amp output) to be leaking into the audio output then you will get enough feedback to oscillate. If the gate of Q3 is below 1 volt referenced to the source during transmit then Q3 may be bad. If there is voltage on the source, check your solder connections of R4.
Keep us informed, please. 73, -Don

Re: Ubitx will be here tomorrow. Any suggestions for a Bitx newbie #ubitx

Bill Cromwell
 

Hi there..

do step 3 before step 2. Install that resistor first. Then apply power.

4. The software is already 'loaded'.

After you install in a case you will have left me behind. I am not interested in touch screens, etc. Enjoy your new radio:)

73,

Bill KU8H

On 08/02/2018 01:38 PM, Truffies wrote:
I just received my ubitx building this weekend on cardboard to see if works.

Questions on steps

1. build on cardboard
2. power
3 place 4.7k in key jack
4 ? do you need to load software?
5. Final listern test to see bands turning rec.
6. Test in dumb load transmit
7. OK build into a case
8. now ready to modify - AGC
9. LCD touch screen add software first to use screen?
(load hex and how to do in steps please where to find) dumb all new to me


-----Original Message-----
From: ajparent1/KB1GMX
Sent: Aug 2, 2018 1:22 PM
To: BITX20@groups.io
Subject: Re: [BITX20] Ubitx will be here tomorrow. Any suggestions
for a Bitx newbie #ubitx

ITs been said but I will repeat.

Build it first and test. Insure you have the 4.7K in place on the
key jack. Double check wiring.

If you are bench testing before boxing it. Use care to avoid
accidental shorts or wires touching
the wrong thing and outside events like ESD (carpet static!). One
example seen was taped to
a piece of card board to keep everything from moving around, worked
well too.

Use 13.8 volts for testing as its likely a V4 board (discrete
transistor audio amp).

If all goes well you may want mods and to pick out what your box is
to look like.

Good luck!

Allison

--
bark less - wag more

Re: Harmonic performance - SSB vs CW

Warren Allgyer <allgyer@...>
 

Allison
I will try lowering the drive to see if it corrects the problem but I am skeptical. I first noted the problem when probing TP1 with the PA unpowered. The discrepancy is already visible at that point. It is pretty clear the harmonics are being generated at the unbalanced mixer.

WA8TOD

Re: Ubitx will be here tomorrow. Any suggestions for a Bitx newbie #ubitx

Truffies
 

I just received my ubitx building this weekend on cardboard to see if works.

Questions on steps

1. build on cardboard
2. power
3 place 4.7k in key jack
4  ? do you need  to load software?
5. Final listern test to see bands turning rec.
6. Test in dumb load transmit
7. OK build into a case
8. now ready to modify - AGC
9. LCD touch screen add software first to use screen?
  (load hex and how to do in steps please where to find)  dumb all new to me


-----Original Message-----
From: ajparent1/KB1GMX
Sent: Aug 2, 2018 1:22 PM
To: BITX20@groups.io
Subject: Re: [BITX20] Ubitx will be here tomorrow. Any suggestions for a Bitx newbie #ubitx

ITs been said but I will repeat.

Build it first and test.  Insure you have the 4.7K in place on the key jack.  Double check wiring.

If you are bench testing before boxing it.  Use care to avoid accidental shorts or wires touching
the wrong thing and outside events like ESD (carpet static!).  One example seen was taped to
a piece of card board to keep everything from moving around, worked well too.

Use 13.8 volts for testing as its likely a V4 board (discrete transistor audio amp).

If all goes well you may want mods and to pick out what your box is to look like.

Good luck!

Allison

Re: Ubitx will be here tomorrow. Any suggestions for a Bitx newbie #ubitx

ajparent1/kb1gmx
 

ITs been said but I will repeat.

Build it first and test.  Insure you have the 4.7K in place on the key jack.  Double check wiring.

If you are bench testing before boxing it.  Use care to avoid accidental shorts or wires touching
the wrong thing and outside events like ESD (carpet static!).  One example seen was taped to
a piece of card board to keep everything from moving around, worked well too.

Use 13.8 volts for testing as its likely a V4 board (discrete transistor audio amp).

If all goes well you may want mods and to pick out what your box is to look like.

Good luck!

Allison

Re: Harmonic performance - SSB vs CW

ajparent1/kb1gmx
 

Warren,

During my sessions testing the amp it was noticed but the 20Mhz and up spur was higher 
on the priority list.

Another thing I ran into with a friend was defective low pass filters.  The toroids had different 
numbers of turns from other units.  

First try lowering the drive (RV1) and look again.  If it drops its the amp flat topping (overdrive)
(can be any stage in the amp up to including the finals.).  That can be voltage starving (less than 
12V at the board) or other problem unnoticed.

It is possible that the first amp Q90 is being over driven as well and reducing RV1 will not help then.

Generally the CW drive was found to be higher than clean levels of SSB drive so it could 
be amp overdrive.  Lowering the DC bias to the mixer during CW TX can help that.  The
Mixer (DBM) is being used as a switch but they can also be used as a variable attenuator
as well.  R114 is the point of adjustment.  Non linear action by the diodes is not an issue
as the driving waveform is square to start with which is why the odd harmonics are stronger
on the display.  Add to that the push pull amps (driver and final) are balanced so the second
and forth are better suppressed but 3 and fifth tend to be the push pull amps weak spot.

Also sweep the 3-5mhz filter to insure its working as expected.  Easy to do with power off
and tracking generator as its then isolated.  Also make sure the correct filter is being
selected, TX-A/B/C should all be selected (relay active).

If the TX amp is at or near compression try turning up the DC power a Volt or so (caution TA2822!).
If the TA2822 is on separate regulated power its safe to go far higher than 13V.

Test first as there are many possible solutions depending on the problem.

Allison

Re: Harmonic performance - SSB vs CW

Jerry Gaffke
 

That's an interesting finding, and seems quite likely correct.
Thanks for looking into that.

One possible solution would be to unbalance either the modulator (as done on the Bitx40 by Allard's mods) 
or the second mixer at D3,D4.  In either case, those harmonics should be stripped out by the 45mhz filter
(also the 12mhz filter, in the case of unbalancing the modulator).  Would require minor hacks to the
firmware to set up the si5351 correctly for CW transmissions after this mod.

Jerry, KE7ER


On Thu, Aug 2, 2018 at 09:26 AM, Warren Allgyer wrote:

I am noting a significant difference in the harmonic suppression in SSB mode versus CW mode. 

The two signals are generated in a very different way. SSB is generated at 45 MHz and mixed down to the final transmit frequency by combining with the first oscillator in the balanced first mixer to make the SSB transmission. In CW the 45 MHz path is disabled and the first oscillator is simply moved to the transmit frequency. The first mixer is unbalanced with a DC bias to allow the first oscillator signal to leak through.

It appears the act of unbalancing this mixer produces harmonics, particularly high order odd harmonics that are clearly in excess of the -43 dBc requirement.

The screenshot shows  the harmonics of an 80 meter transmission at 10 watts. The purple trace is the CW and the blue trace is SSB. Signal source for SSB is a approximately -40 dBV 1 KHz tone with the level adjusted to match the CW carrier level. The SSB signal harmonic suppression is just adequate (green display line) however the CW signal is clearly non-compliant.

I am not sure what to do about it yet but wanted to raise the point. I have done a search on this board since I am new and I do not find this has been reported before..... perhaps I missed it?

WA8TOD

Harmonic performance - SSB vs CW

Warren Allgyer <allgyer@...>
 

I am noting a significant difference in the harmonic suppression in SSB mode versus CW mode. 

The two signals are generated in a very different way. SSB is generated at 45 MHz and mixed down to the final transmit frequency by combining with the first oscillator in the balanced first mixer to make the SSB transmission. In CW the 45 MHz path is disabled and the first oscillator is simply moved to the transmit frequency. The first mixer is unbalanced with a DC bias to allow the first oscillator signal to leak through.

It appears the act of unbalancing this mixer produces harmonics, particularly high order odd harmonics that are clearly in excess of the -43 dBc requirement.

The screenshot shows  the harmonics of an 80 meter transmission at 10 watts. The purple trace is the CW and the blue trace is SSB. Signal source for SSB is a approximately -40 dBV 1 KHz tone with the level adjusted to match the CW carrier level. The SSB signal harmonic suppression is just adequate (green display line) however the CW signal is clearly non-compliant.

I am not sure what to do about it yet but wanted to raise the point. I have done a search on this board since I am new and I do not find this has been reported before..... perhaps I missed it?

WA8TOD

click fix and squeal on transmit #ubitx

Ben AC1FG
 

Hi -- I have had my v3 ubitx working fine, and thought I would install the T/R click fix version 2 from http://www.nd6t.com/uBITX/TR%20Click%20Fix.htm. I'm fairly confident in the circuit I assembled, slightly less confident in the jumpers, trace-cutting, and attachment to the board. The click is still audible in the relay but not in headphones on either transition, and I get a loud squeal on transmit into a dummy load when the volume pot is more than slightly turned up. What should I be looking at to diagnose this?

I noticed continuity between the 12v line and the point marked Rx connection in this section after cutting the trace, which seemed odd:

Re: RFI Problem related by routing audio through K3 (uBitx)?

Mark M
 

Printed Wiring Board,  a.k.a. circuit board.