Date   
LSB signal looking more like AM

joshuaclough@...
 

My SDR shows my BITX40 signal looking more like AM. Has the carrier and USB when it should not. The USB does look weaker than the LSB that's actually supposed to be there, but still way too strong.
I've tried adjusting the two pots thinking that something was overdriving the signal to create this, but those in any combination don't seem to change the sideband supression (or lack there of).
I even tried changing the raduino sketch (which being evidently a clone was fun in itself) without any change.
I've previously tested a lot of stuff already on the board because It stopped transmitting before and stuff tested fine, which drove me nuts. Eventually figured out it was the incompatible microphone type I had hooked up. Had simultaneously changed the power supply and thought that had damaged something and never thought about the mic.

Re: Is push pull hf amp has higher spectral purity

Brian
 

Jerry,
I agree with what you have written and detailed. The transmit spur varies with frequency. Away from 7.2MHz it is outside of the band. Feeding the Raduino into the disabled vfo is not optimal as regards signal purity.
The start of this thread was a suggestion that the Bitx40 might be easier to get fcc compliant. Being single band that might be true but it is not without its own problems. There has been little reported on the Bitx40 since the uBitx was released.
Brian VK4BAP

Re: FS: SotaBeams Laserbeam DSP Variable Filter

Richard Spohn
 

No apology necessary, David. I just need to use my eyes the way they
were meant to be used. Link showed up fine. - Rich

On 12/4/18, N8DAH <@N8DAH> wrote:
Sorry gents should have made the link more obvious. I sold it this afternoon
to a group member
--
David

 N8DAH
Kit-Projects.com ( http://www.kit-projects.com )

Shop is open! ( Https://Shop.Kit-Projects.com )



Re: Desoldering tool suggestion

Art Olson
 

Just took my relays off in 20 minutes using a 
ECG J-045-DS Electric Corded De-Soldering Iron, 420 Degree C Tip Temperature, 45W

From Amazon. Didn’t even need to clean the holes

73
Art


On Dec 5, 2018, at 3:18 PM, bill@... wrote:

I've used the GC Electronics 12-2157 desoldering tool for a number of rework jobs, and it's always worked very well. I have not yet desoldered the relays on my v3 uBITX, perhaps this weekend if some time opens up (I have the Axicom relays ready to go).

Bill N2RKL

Desoldering tool suggestion

Bill
 

I've used the GC Electronics 12-2157 desoldering tool for a number of rework jobs, and it's always worked very well. I have not yet desoldered the relays on my v3 uBITX, perhaps this weekend if some time opens up (I have the Axicom relays ready to go).

Bill N2RKL

Re: Ashhar Farhan #ubitx

Lee
 

Using a toothpick to open the holes is a great idea. 
--
Lee - N9LO  "I Void Warranties"

 

Re: Ashhar Farhan #ubitx

Lawrence Galea
 

Link?


On Wed, Dec 5, 2018 at 6:42 PM Rob Bleumer <Bleumer@...> wrote:
It was a  very easy swap with the relays. They came to me im Europe from Alibaba in 3 weeks 18$ for 10. 5 for my friend. Taking the old ones out with normal solder pump. Just one of the old relays lost a leg. With wooden toothpiks and soldering iron I opend the holes.
Total work 20 minuts for all 5 relays. I' m not a professional.
So just try and do it! It's not so difficult at all.
Rob PA0RBL

Re: Is push pull hf amp has higher spectral purity

Jerry Gaffke
 

Regarding the Bitx40 spur, I previously wrote:

>  I'd say the best solution is to use Allard's v2 firmware and mods, 
>  stay with a high side VFO up around 19.2mhz instead of down at 4.8mhz.

It's possible that a low pass filter on the VFO is sufficient, allowing through 4.8mhz
but not the harmonic at 19.2 mhz.  However, the diode ring mixer is non-linear,
might somehow recreate that 4'th harmonic for us.

Jerry, KE7ER


On Wed, Dec 5, 2018 at 09:56 AM, Jerry Gaffke wrote:
There is a way in which the Bitx40 can produce a spur, as Brian reports.
Look over the last few posts in this thread:
    https://groups.io/g/BITX20/message/21998

The thread has to do with images received when using a low side VFO on the Bitx40.

Example:  
When receiving 7.1mhz, the VFO is at 12 - 7.1 = 4.9mhz.  
The 4'th harmonic of the VFO is at 4 * 4.9 = 19.6mhz, effectively a high side VFO.
We will receive an image if there is a shortwave broadcaster at 19.6 - 12 = 7.6mhz

Not stated in that particular thread, but this can happen on transmit as well.
When transmitting at 7.1mhz, we will have a faint spur at 7.6mhz.
When transmitting at 7.21mhz, we will have a faint spur at     4*(12 - 7.21) - 12 = 7.16mhz
Note that this transmitted spur can easily pass through the 7mhz bandpass filter
and the transmit low pass filter..
The only factor that keeps the spur in check is that the 4'th harmonic of the VFO 
is much weaker than the fundamental of the VFO, and this may vary from board to board,
the VFO drive level programmed into the si5351, and how the VFO wires get routed.

The curious thing is that when transmitting at 7.2mhz, the spur is at 7.2 mhz.
The spur is a valid SSB signal, but on the opposite sideband.
So there's a vague connection with the 7.2mhz Bitx40 birdie,
but the math behind the two is quite different.

I'd say the best solution is to use Allard's v2 firmware and mods, 
stay with a high side VFO up around 19.2mhz instead of down at 4.8mhz.
  https://github.com/amunters/bitx40-raduino-v2
As Brian points out, this cures the spur, but when transmitting an LSB signal
we have the not-so-sharp skirt of the 12mhz crystal filter facing the carrier and opposite sideband.
So we will have additional carrier leakage, and the opposite sideband is not suppressed quite as well.
However, that's a perfectly legal signal anywhere AM phone is allowed.
Especially if only transmitting 5 or 10 watts.

I am of the opinion that if transmitting at 5 or 10 watts, the spur with a stock low side VFO
is likely down far enough to be more or less acceptable.  
But to fully meet regulations with a Bitx40, use Allard's v2 firmware and mods, and a high side VFO.

Jerry, KE7ER

Re: Is push pull hf amp has higher spectral purity

Jerry Gaffke
 

There is a way in which the Bitx40 can produce a spur, as Brian reports.
Look over the last few posts in this thread:
    https://groups.io/g/BITX20/message/21998

The thread has to do with images received when using a low side VFO on the Bitx40.

Example:  
When receiving 7.1mhz, the VFO is at 12 - 7.1 = 4.9mhz.  
The 4'th harmonic of the VFO is at 4 * 4.9 = 19.6mhz, effectively a high side VFO.
We will receive an image if there is a shortwave broadcaster at 19.6 - 12 = 7.6mhz

Not stated in that particular thread, but this can happen on transmit as well.
When transmitting at 7.1mhz, we will have a faint spur at 7.6mhz.
When transmitting at 7.21mhz, we will have a faint spur at     4*(12 - 7.21) - 12 = 7.16mhz
Note that this transmitted spur can easily pass through the 7mhz bandpass filter
and the transmit low pass filter..
The only factor that keeps the spur in check is that the 4'th harmonic of the VFO 
is much weaker than the fundamental of the VFO, and this may vary from board to board,
the VFO drive level programmed into the si5351, and how the VFO wires get routed.

The curious thing is that when transmitting at 7.2mhz, the spur is at 7.2 mhz.
The spur is a valid SSB signal, but on the opposite sideband.
So there's a vague connection with the 7.2mhz Bitx40 birdie,
but the math behind the two is quite different.

I'd say the best solution is to use Allard's v2 firmware and mods, 
stay with a high side VFO up around 19.2mhz instead of down at 4.8mhz.
  https://github.com/amunters/bitx40-raduino-v2
As Brian points out, this cures the spur, but when transmitting an LSB signal
we have the not-so-sharp skirt of the 12mhz crystal filter facing the carrier and opposite sideband.
So we will have additional carrier leakage, and the opposite sideband is not suppressed quite as well.
However, that's a perfectly legal signal anywhere AM phone is allowed.
Especially if only transmitting 5 or 10 watts.

I am of the opinion that if transmitting at 5 or 10 watts, the spur with a stock low side VFO
is likely down far enough to be more or less acceptable.  
But to fully meet regulations with a Bitx40, use Allard's v2 firmware and mods, and a high side VFO.

Jerry, KE7ER


On Tue, Dec 4, 2018 at 07:36 PM, Jerry Gaffke wrote:
Brian,

So when operating between 7.1 and 7.3 mhz on the Bitx40 we have a transmit spur at 7.2mhz?
That would be weird, especially if the spur didn't move as we tuned across that range.

The receive birdie at 7.2mhz is due to the  12mhz - 7.2mhz = 4.8mhz low side VFO
having a 5'th harmonic at 5*4.8=24mhz which beats with the second harmonic of the 12mhz BFO.

Anybody see any way that this might go out as a transmit spur?
Has anybody else seen this spur?

Jerry, KE7ER


toggle quoted message. . .

 

On Mon, Dec 3, 2018 at 01:23 PM, Brian wrote:
The stock Bitx40 has a problem with the 7.2MHz birdie not only on receive but also it produces a spur on transmit which does not meet fcc spec.
You could use it on 7.1MHz and below or change the vfo to high side and move the carrier oscillator to the other side of the filter (Allard's software). Whether you can do that depends on the xtal filter in your Bitx40. You may get lots of carrier and poor sideband rejection.
The Bitx is a good entry into homebrew. You might get away with using it barefoot but take care if you want to push to higher power.
73 Brian.

Re: Is push pull hf amp has higher spectral purity

Rob Bleumer <Bleumer@...>
 

In Europe the birdey on 7.2Mhz is a nice end of band signal🤓
Rob

Re: Ashhar Farhan #ubitx

Rob Bleumer <Bleumer@...>
 

It was a  very easy swap with the relays. They came to me im Europe from Alibaba in 3 weeks 18$ for 10. 5 for my friend. Taking the old ones out with normal solder pump. Just one of the old relays lost a leg. With wooden toothpiks and soldering iron I opend the holes.
Total work 20 minuts for all 5 relays. I' m not a professional.
So just try and do it! It's not so difficult at all.
Rob PA0RBL

Re: Lee's complaints

MVS Sarma
 

Don't say that John. It was never our intention to spam him.
 Perhaps he is impatient that Ashar Farhan did not reply to his query, but all others.
 After all he is also like all of us. I was dam impatient in my 20s.
  OK , Let him come out of his feelings.
  All the best to him.in his hobby and HAM operations.


On Wed, Dec 5, 2018 at 5:02 AM John <johnk5mo@...> wrote:
Lee, you're spamming the group. Please stop.
John K5MO

Re: Ashhar Farhan #ubitx

bill wright
 

Folks
As you modify these PCB's to correct spurs and such remember;

Adding new PCB's and or daughter boards often inject new noise sources.
and may disrupt existing signals.  Placement  and integrity of new boards
will affect the UBITX.  So approach this effort with care.
73 Bill de kd5yyk



From: Jerry Gaffke via Groups.Io <jgaffke@...>
To: BITX20@groups.io
Sent: Tuesday, December 4, 2018 12:04 PM
Subject: Re: [BITX20] Ashhar Farhan #ubitx

Curt wrote
>  Do expect you will need some mods to correct spurious - the conservative approach
>  seems to be a daughter board hosting an added set of relays, and some additions to the 45 MHz filter.

Harmonics could be fixed by an external daughter board with relays and transmit low pass filters,
duplicating what KT1,KT2,KT3 and L11 through L22 are supposed to be doing.
Some forum members have created circuit boards that they sell as a kit to do this.

Alternately, just replace the KT1, KT2, KT3 relays with Axicom relays,
This is probably the preferred method for fixing harmonics if you can figure out
how to remove the old relays.

Harmonics are unwanted transmissions that occur at integer multiples of the desired frequency.
Some might use the term "spurs" to refer to harmonics.
Most people here use the term "spurs" to refer to any unwanted transmission that is not a harmonic.
Spurs are addressed in this thread of 60+ posts:
    https://groups.io/g/BITX20/message/61645

In that first post of the thread, Farhan writes:
>  4. With the relays that are now used for ubitx,  the harmonics at 3.5, 7 and 10 are in under -45 dbc. we don't need the axicom relays.

From that, I assume that a uBitx shipped today from HFSignals has new relays, appropriate for RF switching.
Unfortunately, no mention there of how to determine if your uBitx has old or new relays. 

The relays on my first run v3 board of a year ago are of the "Virtual" brand,
model VRS2H-S-DC12V-C.
I'd guess that if the relays on your rig are some other brand, then you have the new relays.

None of this is really nailed down yet well enough for somebody with a uBitx and DVM
to be sure his rig is legal. 

We need to know:
1)  Exactly which uBitx boards need the relays swapped out to Axicom?
2)  Exactly what parts should we procure for relay replacements and spur filters?
3)  Exactly how should those spur fix parts be installed on the board?  (With photos)

Farhan recommended toroids for the spur filter inductors,
Raj has found that shielded surface mount inductors work.
Cheap standard issue surface mount inductors are apparently not sufficient.
 
Rather absurd that this has not yet all been resolved
to a recommended list of part numbers and step by step procedure for installing them.
It's been months.

Jerry, KE7ER
 



Re: Ashhar Farhan #ubitx

Curt
 

All good info, I did not wish to stir up a hornet's nest.  Remember this rig is not produced by a full-time, for-profit enterprise.  Please respect the efforts by lots of people world-wide as we work this.  I do imagine that for many builders it is best not to remove relays from the board - hence I suggest consideration for a daughter-board solution using more inexpensive relays (note a separate board may improve SOME layout considerations, depending upon implementation).  I respect there may be more than one workable solution for each malady, but with varying degree of difficulty.  Please respect the providers of the ubitx board, and that for some users it may be their main rig out of necessity.  Expect that solutions will come, and be sufficiently validated before someone, somewhere offers them as a kit.  I agree there are several threads and lots of varying info dispersed, and different degrees of construction skill.  In our group build we are majoring on solutions that do not require 'leading edge' tools and skills. 

very 73

Curt

Re: UbitX audio hiss but no rx

Sean Pearce
 

I have double checked the connector...  I'm confused...  Doesn't take much to do that.


From: BITX20@groups.io <BITX20@groups.io> on behalf of AA9GG <paul.aa9gg@...>
Sent: 05 December 2018 00:38
To: BITX20@groups.io
Subject: Re: [BITX20] UbitX audio hiss but no rx
 
I had the same issue.  When putting things together, I forgot to connect the antenna connector to the pcb..... D'oH!!!!

--
Paul Mateer, AA9GG
Elan Engineering Corp.
www.elanengr.com
NAQCC 3123, SKCC 4628

Re: 7277 Bitx >Bitx Today 12/2/18

iz oos
 

I had a couple of QSOs on 7.177mhz looking for QRP. None of them was. On 7.277 there were only strong AM stations at least here in the Euro side. To be on the safe side a General should call at 7.178.


Il 05/dic/2018 04:16, "d balfour" <davesters@...> ha scritto:
I will listen to 7180 but find it crowded on Sunday afternoon at times. 40 can be bad with AM Carriers. 7.285 is a fairly recognized qrp frequency. I had a 20m qso last Sunday on 14.285 They were in Florida about 1000 miles away.  20 of course is not friendly to those with Bitx40s.

Although technically US Generals can go as low as 7175. On LSB that will put one in violation of the rules.



Re: Great Results with Mic Preamp

Paul Dobosz <pjdobosz@...>
 

I suspect that RF is getting into the base emitter junction and causing problems.  The preamp was designed to be located inside of the microphone with nearly zero lead length between the mic cartridge and the input.  Adding a mic cable with considerable  length that couples directly to the emitter changes the situation quite dramatically as you have placed an antenna on the emitter of the 2N3904.  You are also inside the same enclosure in closer proximity to the RF output stage.

As I mentioned, the preamp circuit was a minimal design meant to fit inside of the diecast mic body so no RF bypass capacitors or ferrites were needed or included in my application.  Some measures I might suggest to mitigate are adding 1000pF bypass capacitors to the base and collector leads of the 2N3904.  If more help is needed, ferrite beads can be added in series with the collector and emitter leads.  Finally, if the issue persists, shielding may be needed to attenuate RF energy that is radiated directly into the device.  Also make sure your internal preamp grounding in low impedance at RF.

73 - Paul - K8PD

Re: Ashhar Farhan #ubitx

iz oos
 

As for older boards that need relay replacement I have to say they were all but an easy swap. Using just a solder iron, copper braid and a pump I could not remove any of them. They were useful but not enough. I had to use a rework SMD station (and a screwdriver for leverage to pull them out) , something I was discouraged here using it, but it worked well. And no other component fell or burn. Using the recommended Axicom I have seen the 3rd harmonics further down by something like 15db. I can only measure it using an sdr receiver, so not a real spectrum analyzer. Having said this what is lacking is a real aftermarket shop for the mods required depending on the version of various boards. Even some Drake rtx were not perfect and kits have greatly improved their performance, becoming legendary in some cases. This 'absurd' situation is just a business opportunity for others.


Il 05/dic/2018 04:25, "Jerry Gaffke via Groups.Io" <jgaffke=yahoo.com@groups.io> ha scritto:
Between Raj and Farhan, we have some nice minimalist solutions for spurs.

A number of fixes for the harmonics have been proposed,
I like swapping out the relays if that works well enough. 

If inductors are involved, a specific ready made and easily obtained part would be ideal. 
But the toroids Farhan used in his filters would be acceptable.

Would be nice to resolve this to a recommended set of fixes.
Fully described   
List of exactly what parts to buy.
Schematics and photos. 

> It cleans up the act only on the higher bands. 

I guess that means it cleans up the spur we have trouble with on 15m, 12m and 10m.
This spur is at   45mhz - DialFreq.
At 17m and bands below that, the spur is sufficiently above the transmit frequency
that the transmit low pass filters take care of it.

Farhan also had a fix for the 12mhz spur that's due to crosstalk from clk0  into  clk2 at the si5351.
One issue was that his fix knocked out 30m, which may not be an issue on a a mostly SSB rig.
Another issue is that the part values he gave would resonate closer to 10mhz that 12mhz,
though there may be a reason for that.
A third issue is that Jerry Gaffke kind of thinks a HPF on clk2 with a corner at 30mhz or so 
might be a better, less finicky solution. But he's not to be trusted on this stuff.

Jerry Gaffke


On Tue, Dec 4, 2018 at 06:50 PM, Raj vu2zap wrote:
The 45MHz filter fix of mine and the LP filter of Farhans does the same thing. It
cleans up the act only on the higher bands. I tested it on a new board last
week.

Change to AXICOM relays is a must. Spurs are further reduced with change of
L5 and addition of 45MHz LP filter.

Re: Is push pull hf amp has higher spectral purity

Jerry Gaffke
 

Brian,

So when operating between 7.1 and 7.3 mhz on the Bitx40 we have a transmit spur at 7.2mhz?
That would be weird, especially if the spur didn't move as we tuned across that range.

The receive birdie at 7.2mhz is due to the  12mhz - 7.2mhz = 4.8mhz low side VFO
having a 5'th harmonic at 5*4.8=24mhz which beats with the second harmonic of the 12mhz BFO.

Anybody see any way that this might go out as a transmit spur?
Has anybody else seen this spur?

Jerry, KE7ER


On Mon, Dec 3, 2018 at 01:23 PM, Brian wrote:
The stock Bitx40 has a problem with the 7.2MHz birdie not only on receive but also it produces a spur on transmit which does not meet fcc spec.
You could use it on 7.1MHz and below or change the vfo to high side and move the carrier oscillator to the other side of the filter (Allard's software). Whether you can do that depends on the xtal filter in your Bitx40. You may get lots of carrier and poor sideband rejection.
The Bitx is a good entry into homebrew. You might get away with using it barefoot but take care if you want to push to higher power.
73 Brian.

Re: Documentation on uBitx help

Curt
 

Bret try ubitx calibration or zerobeat into search engine, that should take you to hfsignals page. My bfo setting was way off, I needed a clue on it to get it close enough to align.

If you happen to be using Sunil's case, check out ubitx.com for latest info.  its a different site than ubitx.net. assembly is a snipe hunt, so patiently work it.

Curt