Date   
Re: Winding QCX T1 #qcx #t1

Braden Glett
 

QRPguys use the easily burned off insulation wire, as well. If you download their manual for the regenerative SW receiver, it names the brand of wire.

328P #problem

dl8wkr@...
 

Hello qcx hobbyist.

I'm asking for your help!

A friendly hobbyist has given me his broken qcx. Before I go into the error search, the error image with solution request.

qcx R / TX works. The buttons and the rotary encoder show no or partial reaction. Visual inspection showed, except too much flux on the solder joints, no errors.

328 has already been exchanged, no change.

TNX Knut DL8WKR

Re: 328P #problem

Hans Summers
 

Hi Knut

What PCB revision? If 1 or 2, have you done this mod: http://qrp-labs.com/qcx/qcxmods.html#pwrup -lack of this mod can result in those synptoms.

73 Hans G0UPL 

On Sun, Aug 26, 2018, 19:37 <dl8wkr@...> wrote:
Hello qcx hobbyist.

I'm asking for your help!

A friendly hobbyist has given me his broken qcx. Before I go into the error search, the error image with solution request.

qcx R / TX works. The buttons and the rotary encoder show no or partial reaction. Visual inspection showed, except too much flux on the solder joints, no errors.

328 has already been exchanged, no change.

TNX Knut DL8WKR

Re: QSX radio feature requests

John VA7JBE
 

There was an autotuner project by Martin AE7EU published last year as part of a power amplifier that might be adapted to the QSX.  The details are here: http://ae7eu.com/index.php/quickie-50-amplifier/

Re: QSX radio feature requests

ajparent1/KB1GMX
 

I'm going to take a liberty to sane something....

There is the group Antennas (groups.io) where some of this coversation has migrated to.
It might be more appropriate there.

Allison

Re: QSX radio feature requests

jmh6@...
 

Hi All,

"It might be more 'appropriate' there."

Pretty sad commentary if you were to ask me....

Then again you didn't ask. Or did you?

John

On Sun, 26 Aug 2018, ajparent1/KB1GMX wrote:

I'm going to take a liberty to sane something....
There is the group Antennas (groups.io) where some of this coversation has
migrated to.
It might be more appropriate there.
Allison

Re: QSX radio feature requests

John VA7JBE
 

Hi John,

That's hurtful, non-constructive, and negatively impacts our sense of community.

Other John

Re: QSX radio feature requests

ajparent1/KB1GMX
 

What you missed is the conversation is already spread across the two sites.
Its hard to have community when its hard to figure out who is replying to whom
and where.

Other than its was a suggestion.  That what might, rather shall or should means.

Allison

Re: Winding QCX T1 #qcx #t1

Steve in Okinawa
 

Also the KD1JV kits sold by Pacific Antenna. Made the toroid installation very easy. 73 from Okinawa

Pushing the QCX (T1 question) #qcx

John VA7JBE
 

I'm interested in trying to push my QCX into being usable on both the 20m and 30m bands, with some obvious reductions in efficiency.  The parts that would affect the performance seem to be the LPF, the BPF, and the number of turns on the T1 transformer.  The LPF will just be what it is, though I might try to use a slightly different configuration to get a steeper attenuation curve above 14 MHz, the BPF I can adjust by switching in some parallel capacitance the way that Steve G4EDG has done (see builders' gallery), but the primary windings on T1 are something I can only speculate about. 

The manual calls for 3 turns each on the primary and secondary T1 windings for 20m, and 4 turns each for 30m.  Considering this is a transformer and that lower frequencies call for even more turns I'm guessing that the extra windings are a matter of efficiency.  If I were to use 4 windings on T1 (not counting the 30 BPF turns) instead of 3, would this adversely impact the performance on 20m?  Conversely, how much efficiency would I drop if I were to try and operate on 30m with 3 windings, as per the 20m configuration?  In either case my guess is not much, but if anyone has any insight or experience trying this then I'd be keen to hear it. 

My kit is still in the mail and I'll be building it almost exclusively for portable SOTA work so having an extra band would really help for those days when the atmospheric conditions are challenging.  Steve has reported good results from his 17m/20m build, but I suspect with propagation the way it is these days I'd get more use out of a 20m/30m split. 

Cheers,
John VA7JBE

Re: Pushing the QCX (T1 question) #qcx

Alan G4ZFQ
 

I'm interested in trying to push my QCX into being usable on both the 20m and 30m bands, with some obvious reductions in efficiency.  The parts that would affect the performance seem to be the LPF,
John,

Hans makes his RX kits quite narrow compared with other SDRs that use similar circuitry.
The Softrock RXTX for example had a version covering 40 - 30 - 20m with only the need to add a LPF for 20m.
I do not think you would find a wider BPF in the QCX RX would make any great difference. Nor would the small difference in the windings on T1.
The PA is a different thing. It is designed as a single band class E. I'd imagine that the 20m LPF, again tighter than Softrocks, would still be adequate at 30m although that would need testing depending how concerned you are.
As for optimising L4 and C30 for two bands I guess reasonable results could be achieved.
In view of a few reports of catastrophic failure due to PA breakdown I would suggest isolating IC3 pin 3 with a capacitor. Use a resistor to keep the gates low when not driven.

73 Alan G4ZFQ

Re: Pushing the QCX (T1 question) #qcx

Hans Summers
 

Hi John, Alan
 
Hans makes his RX kits quite narrow compared with other SDRs that use
similar circuitry.

;-)   I think a narrow BPF improves the performance. Even with a strong mixer such as in the QCX (high dynamic range and IP3), it is good to keep strong out of band signals away from the mixer. Having a wide BPF which covers several bands makes the radio cheaper and less complex (fewer filters) but it is a compromise, in my opinion. 
 
As for optimising L4 and C30 for two bands I guess reasonable results
could be achieved.

The Class-E resonance is quite broad. There should not be any major problem, operating the Class E PA stage on two adjacent bands such as 20m and 30m. 
 
In view of a few reports of catastrophic failure due to PA breakdown I
would suggest isolating IC3 pin 3 with a capacitor. Use a resistor to
keep the gates low when not driven.

It won't work... if you capacitatively couple IC3 pin 3 to the PA gate, then the peak-peak squarewave will be 5V BUT, it will be centered on 0V. The resulting peaks at the BS170 gate will be only 2.5V above ground and will not drive the BS170 into full conduction. The power output would be greatly diminished. One of the key criteria for obtaining Class-E operation is to drive the PA device hard off/on as a switch. 

73 Hans G0UPL

Re: Pushing the QCX (T1 question) #qcx

Alan G4ZFQ
 

;-)   I think a narrow BPF improves the performance.
Hans,

Yes, I do not dispute that. But may I suggest the difference would not usually be noticed without careful comparison.

I would suggest isolating IC3 pin 3 with a capacitor.
It won't work... if you capacitatively couple IC3 pin 3 to the PA gate, then the peak-peak squarewave will be 5V BUT, it will be centered on 0V.
Oh yes, I see...
But it seems there have been a couple of cases where PA device failure has resulted in 12V being sent back through IC3. One of those affected have reported failure of the Si5351 and another has said IC2 required replacing.
If that really is the case then I'm wondering how to buffer IC3 to avoid this rare occurrence.

73 Alan G4ZFQ

Re: Pushing the QCX (T1 question) #qcx

Alan
 

Simple problem, Coupling C then resistor with parallel diode to ground. Fet gate goes to ground with no drive, drive loss is Vf of diode.  DC restoration circuit  used in  AC coupled video amplifiers from 70 years back .

 

Alan

G8LCO

 

Sent from Mail for Windows 10

 

From: Alan G4ZFQ
Sent: 27 August 2018 08:38
To: QRPLabs@groups.io
Subject: Re: [QRPLabs] Pushing the QCX (T1 question) #qcx

 

> ;-)   I think a narrow BPF improves the performance.

 

Hans,

 

Yes, I do not dispute that. But may I suggest the difference would not

usually be noticed without careful comparison.

 

>>> I would suggest isolating IC3 pin 3 with a capacitor.

> It won't work... if you capacitatively couple IC3 pin 3 to the PA gate,

> then the peak-peak squarewave will be 5V BUT, it will be centered on 0V.

 

Oh yes, I see...

But it seems there have been a couple of cases where PA device failure

has resulted in 12V  being sent back through IC3. One of those affected

have reported failure of the Si5351 and another has said IC2 required

replacing.

If that really is the case then I'm wondering how to buffer IC3 to avoid

this rare occurrence.

 

73 Alan G4ZFQ

 

 

 

Small Receiver improvements (was:Receiving on harmonics of Receiver LO?)

erik@...
 

Alan,

Thanks for the excellent article!
Some learnings from it: 

  • If I want a wide detection bandwith (say 192kHz of HDSDR I/Q detection) I need to reduce C3 till C6 from 100nF to say 3nF.
  • To reduce noise I should remove (short) resistors R26 and R27 (now 82 ohm)
  • To even further reduce noise I could remove R9, R10, R14 and R15 (10k) and short C9-C12 (1uF). Can this work with the opamps at 12V? I can keep IC5A/B biased at 6V but the instrumentation opamps (IC3 and IC4) seem to do the bulk of the amplification so these preferably also should be kept  at 12V to increase dynamic range, but with bias at 2.5V (instead of 6V) I will not get extra dynamic range.

I'm using the receiver with a magnetic loop amplified with 2 stage balance Norton amplifier. 




--
Erik@Home

Re: Pushing the QCX (T1 question) #qcx

Hans Summers
 

Hi Alan
 
> ;-)   I think a narrow BPF improves the performance.

Hans,

Yes, I do not dispute that. But may I suggest the difference would not
usually be noticed without careful comparison.

Yes, I agree. But many people have a noisy receiver and don't ever know it... the mixture of lots of unwanted intermodulation products raising the noise floor sounds the same as any other noise. Unless there are particular strong spurii caused by certain stations' mixing products. 

Remember the QCX constructor who complained his QCX has very low audio, low volume... but, when he tuned to a station it did sound very loud? He was used to a more noisy receiver ;-)   Noise that wasn't even really there, just added by the radio itself.  
 
>>> I would suggest isolating IC3 pin 3 with a capacitor.
> It won't work... if you capacitatively couple IC3 pin 3 to the PA gate,
> then the peak-peak squarewave will be 5V BUT, it will be centered on 0V.

Oh yes, I see...
But it seems there have been a couple of cases where PA device failure
has resulted in 12V  being sent back through IC3. One of those affected
have reported failure of the Si5351 and another has said IC2 required
replacing.
If that really is the case then I'm wondering how to buffer IC3 to avoid
this rare occurrence.

Yes, an interesting question. Something between IC3 output and the BS170 gate, which does not alter the sharp edges of the waveform, nor does it reduce the 5V "on" voltage, since that would mean the BS170's not being driven ON so hard, which would reduce the efficiency and power output. It's a tall order... 

73 Hans G0UPL
 

Re: U3S on 630M "crashes" the system. #u3s #630m

Stig oz8pz-oz8wsp-oz8wsr
 

Hi, have you put small capacitors rigt on the leg of the 7805? I alwais put
1 uf tantal right on the 7805 and for that low frequency perhaps 10 uf tantal also.
It could be that 7805 osc. on the low frequency.
73, Oz8pz, stig

Sendt fra min iPad

Den 26. aug. 2018 kl. 07.32 skrev Brian - VA7BBG <brianrbutler@...>:

Thanks for the idea Roger.

I run from a battery with an LM7805 bypassed and filtered (3000uF) on the input. I added 4400uF to the output side and the problem is still there (sadly).

I'm wondering now if my bypassing is sufficient for this frequency. The mods page (http://qrp-labs.com/ultimate3/u3mods.html) lists a couple of 630M mods. Toni also changed the bypass capacitors (and C5). I'm wondering if my bypass capacitors on the regulator are sufficient as well..
 

Thanks for the thoughts Roger, I'm now on a bypass quest!
--
73

Brian
VA7BBG

Re: Pushing the QCX (T1 question) #qcx

Alan de G1FXB
 

RE: QCX PA Failures:-
there comes a time where you cannot protect for every eventuality?

(If you not already seen it, have a look at the PA circuitry in the NC2030 design,
I guess something similar was not included for reason of cost, both component and also PCB  size increase?)
It's an example of when potentially it costs more for the protection circuit than the likely failure scenario,

In the QCX It's Q1->3, Q6 and possibly IC3, they add up to something sub $4 to replace??
(Q6 Should never fail spectacularly as often as it's being reported, it's rated at 2A dissipation.
The QCX on TX consumes circa 500mA TOTAL. Why doesn't a fuse save it?)
the failure of the si5351 is 1 in 5,500+ QCX's that have being built occurrence?



The best protection is afforded by the operator him / her self, perhaps think before pushing a QCX hard..
Remember there is no fancy SWR mismatch or over temp protection on long duty cycle modes.

"Without any protection circuits the QCX  will try it's very best to fulfil it's purpose,
right up to the point of failure."


Alan



On 27/08/2018 08:38, Alan G4ZFQ wrote:
;-)   I think a narrow BPF improves the performance.

Hans,

Yes, I do not dispute that. But may I suggest the difference would not usually be noticed without careful comparison.

I would suggest isolating IC3 pin 3 with a capacitor.
It won't work... if you capacitatively couple IC3 pin 3 to the PA gate, then the peak-peak squarewave will be 5V BUT, it will be centered on 0V.

Oh yes, I see...
But it seems there have been a couple of cases where PA device failure has resulted in 12V  being sent back through IC3. One of those affected have reported failure of the Si5351 and another has said IC2 required replacing.
If that really is the case then I'm wondering how to buffer IC3 to avoid this rare occurrence.

73 Alan G4ZFQ




Re: Pushing the QCX (T1 question) #qcx

Hans Summers
 

Hi Alan 

Yes, protection circuits would have added cost and complexity. And it is hard to protect against every possible failure mode. In my opinion it wasn't necessary. During all my QCX development, I never managed to break any IC3, Q6 (the earlier MPS2907 0.6A version), or any of the BS170s. Not by mismatched load, nor open load, nor short-circuit, nor continuous duty-cycle. Not even by temporarily increasing the supply voltage to around 20V and getting 10W out. Not a failure on any of the six bands. Not with a detuned Class-E resonant circuit either. If I couldn't cause any failures while I was working on the development... I didn't see the need to unnecessarily increase the cost and complexity if it was so hard for me to break something.

73 Hans G0UPL 

On Mon, Aug 27, 2018, 17:27 Alan de G1FXB via Groups.Io <g1fxb=yahoo.co.uk@groups.io> wrote:
RE: QCX PA Failures:-
there comes a time where you cannot protect for every eventuality?

(If you not already seen it, have a look at the PA circuitry in the NC2030 design,
I guess something similar was not included for reason of cost, both component and also PCB  size increase?)
It's an example of when potentially it costs more for the protection circuit than the likely failure scenario,

In the QCX It's Q1->3, Q6 and possibly IC3, they add up to something sub $4 to replace??
(Q6 Should never fail spectacularly as often as it's being reported, it's rated at 2A dissipation.
The QCX on TX consumes circa 500mA TOTAL. Why doesn't a fuse save it?)
the failure of the si5351 is 1 in 5,500+ QCX's that have being built occurrence?



The best protection is afforded by the operator him / her self, perhaps think before pushing a QCX hard..
Remember there is no fancy SWR mismatch or over temp protection on long duty cycle modes.

"Without any protection circuits the QCX  will try it's very best to fulfil it's purpose,
right up to the point of failure."


Alan



On 27/08/2018 08:38, Alan G4ZFQ wrote:
;-)   I think a narrow BPF improves the performance.

Hans,

Yes, I do not dispute that. But may I suggest the difference would not usually be noticed without careful comparison.

I would suggest isolating IC3 pin 3 with a capacitor.
It won't work... if you capacitatively couple IC3 pin 3 to the PA gate, then the peak-peak squarewave will be 5V BUT, it will be centered on 0V.

Oh yes, I see...
But it seems there have been a couple of cases where PA device failure has resulted in 12V  being sent back through IC3. One of those affected have reported failure of the Si5351 and another has said IC2 required replacing.
If that really is the case then I'm wondering how to buffer IC3 to avoid this rare occurrence.

73 Alan G4ZFQ




Re: Pushing the QCX (T1 question) #qcx

Alan de G1FXB
 

Thanks Hans,
I don't know how some manage it...

10W @ 20V, lets do the maths.   :-[
But it lived.......


Alan

On 27/08/2018 15:41, Hans Summers wrote:
Hi Alan 

Yes, protection circuits would have added cost and complexity. And it is hard to protect against every possible failure mode. In my opinion it wasn't necessary. During all my QCX development, I never managed to break any IC3, Q6 (the earlier MPS2907 0.6A version), or any of the BS170s. Not by mismatched load, nor open load, nor short-circuit, nor continuous duty-cycle. Not even by temporarily increasing the supply voltage to around 20V and getting 10W out. Not a failure on any of the six bands. Not with a detuned Class-E resonant circuit either. If I couldn't cause any failures while I was working on the development... I didn't see the need to unnecessarily increase the cost and complexity if it was so hard for me to break something.

73 Hans G0UPL 

On Mon, Aug 27, 2018, 17:27 Alan de G1FXB via Groups.Io <g1fxb=yahoo.co.uk@groups.io> wrote:
RE: QCX PA Failures:-
there comes a time where you cannot protect for every eventuality?

(If you not already seen it, have a look at the PA circuitry in the NC2030 design,
I guess something similar was not included for reason of cost, both component and also PCB  size increase?)
It's an example of when potentially it costs more for the protection circuit than the likely failure scenario,

In the QCX It's Q1->3, Q6 and possibly IC3, they add up to something sub $4 to replace??
(Q6 Should never fail spectacularly as often as it's being reported, it's rated at 2A dissipation.
The QCX on TX consumes circa 500mA TOTAL. Why doesn't a fuse save it?)
the failure of the si5351 is 1 in 5,500+ QCX's that have being built occurrence?



The best protection is afforded by the operator him / her self, perhaps think before pushing a QCX hard..
Remember there is no fancy SWR mismatch or over temp protection on long duty cycle modes.

"Without any protection circuits the QCX  will try it's very best to fulfil it's purpose,
right up to the point of failure."


Alan



On 27/08/2018 08:38, Alan G4ZFQ wrote:
;-)   I think a narrow BPF improves the performance.

Hans,

Yes, I do not dispute that. But may I suggest the difference would not usually be noticed without careful comparison.

I would suggest isolating IC3 pin 3 with a capacitor.
It won't work... if you capacitatively couple IC3 pin 3 to the PA gate, then the peak-peak squarewave will be 5V BUT, it will be centered on 0V.

Oh yes, I see...
But it seems there have been a couple of cases where PA device failure has resulted in 12V  being sent back through IC3. One of those affected have reported failure of the Si5351 and another has said IC2 required replacing.
If that really is the case then I'm wondering how to buffer IC3 to avoid this rare occurrence.

73 Alan G4ZFQ