Date   

Re: Problem with BPF

GM7
 

I'm struggling to see how this is a tuning issue?

I was towards the fully engaged end of the trimmers so I removed one turn.  I was then at the minimum of the trimmer so I had to compress the turns to get back to mid range on the trimmers.  This just put me back where I started.

Modifying the trimmers and the turns just moves the center frequency up and down and doesn't really change the loss.  No combination of trimmers and inductors puts the loss in a sensible place even when I try different frequencies.

Another example response after removing turns and lots of tweaking.  Again on the design frequency and a good looking curve?  Possibly too narrow?  Loss is over 30dB.

I also removed the inductors completely and re-measured them.  They are 2.1uH as per the manual.






Re: QCX+ alive!

David Fine
 

Hans,

The drilling of the spacers used on the LCD PCB would definitely make it easier to assemble.  I did that on mine after trying to assemble it per the instructions.  That took the pain out of assembly.

Dave, W0DF


Re: Si5351A'Synth & QCX+TCXO

Mike Besemer - WM4B
 

I buy from Mouser.

 

Mike

WM4B

 

From: QRPLabs@groups.io [mailto:QRPLabs@groups.io] On Behalf Of dl2arl@...
Sent: Sunday, July 5, 2020 4:47 PM
To: QRPLabs@groups.io
Subject: Re: [QRPLabs] Si5351A'Synth & QCX+TCXO

 

Mike, WM4B

yes, I read the manual of the Rev4 Synth where Hans gives hints on usalbe and available TCXOs to fit the pads provided on the PCB.

BUT

ordering one single TCXO from the usual providers will cost more on postage than the TCXO is worth. Do you know a good source?

Yours friendly, Razvan DL2ARL


Re: Si5351A'Synth & QCX+TCXO

DL2ARL
 

Mike, WM4B

yes, I read the manual of the Rev4 Synth where Hans gives hints on usalbe and available TCXOs to fit the pads provided on the PCB.

BUT

ordering one single TCXO from the usual providers will cost more on postage than the TCXO is worth. Do you know a good source?

Yours friendly, Razvan DL2ARL


Re: QCX+ alive!

Hans Summers
 

Hi Dean

Thanks for the nice feedback, glad you love the QCX+ kit! 

Yes, fitting the bolt in the bottom right corner of the LCD, right next to the rotary encoder, is tricky! But it DOES work with some effort. 

There wasn't really any alternative, to fit the enclosure and the controls in the desired positions, there wasn't another way to do it. No more mm spare in that area. 

The nylon nuts supplied are correct to use. 

The job can perhaps be made a bit easier by drilling the threads out of the 7mm spacers and four of the nylon nuts. Leaving only the thread on the final four nylon nuts intact to secure the assembly together. 

73 Hans G0UPL 

On Sun, Jul 5, 2020, 20:20 Dean Smith <bardezbiker@...> wrote:
Can't say i had any problems with IC/Resistor placement, i agree it is a little cozy as is C39, the nearest resistor to IC3 is R1 with R2 behind it.
Maybe something for a future revision, tbh i didn't notice on assembly.
IF.....,IF i had to have a grumble,, The LCD fitting nuts'n'bolts are more of a pressing concern. The bolt nearest the Encoder has little space for the nut/spacer ,between the back of the lcd and the backplane pcb. I used plastic M3 nuts all round here to avoid any shorts/overtightning ect. the 16 way molex pins plastic spacer provides the correct gap, anyhow. I'm sure if Han's has already assembled one without the air turning blue,then things will be ok. Just a personal preference:). the one good thing about a pluggable front on the radio, is it helps to assemble without half the kit hanging of it. And those of you still waiting for the kit, you'll not be disappointed! The kit IS the mutts nuts!
Dean (G7EOB)


Re: VFO Signal Generator with incorrect fundamental and sinusoidal contamination #vfo

Alan G4ZFQ
 

I know HDSDR is not as robust as other SDR SW for removing images. Recommendations for better SW?
Alan,

No, it is the one I use. Image rejection is not really a problem although a good audio card helps to keep rejection more flat across the spectrum rather than where you set it. (Usually at the LO offset.)
But, I do not understand why the presence of image artifacts is unpredictable; some days/time-of-day they seem nonexistent, other times very noticeable.
The trouble with SDRs is that they show all the minor spurii that are often not noticed on a conventional radio. I guess there are far more these days, much electronic equipment will not pass emission standards but the authorities do their best to ignore that.

73 Alan G4ZFQ


Re: OOPS ! 50 Watt Amp

Hans Summers
 

Hi Paul

This transistor is very non-critical here. 

The only important parameters of the transistor in this application is that it needs to be a P-channel type, and have a Drain Source breakdown rating of at least 160V. Many MOSFETs have 60V or 100V ratings and this is not enough. The current handling capability and power dissipation capability are of no consequence. It only passes microamps and dissipates microwatts. 

I chose this device just because it met the criteria (P type, high voltage) and was easily available and cheap. The large package and power handling are not a requirement. Only the P type and high voltage. 

73 Hans G0UPL 

On Sun, Jul 5, 2020, 20:26 K2DB Paul Mackanos <paul.mackanos@...> wrote:
Found  FQPF2N60C, TO220, MOSFET at DigiKey, $1.16 each + $4.99 shipping, ordered a few extras.
Paul K2DB

On Sun, Jul 5, 2020 at 1:12 PM K2DB Paul Mackanos via groups.io <paul.mackanos=gmail.com@groups.io> wrote:

Update on OOPS ! 50 Watt Amp

Here is a high def picture with a computer microscope showing a burn mark directly above  Q3 FQPF2N60C, TO220, MOSFET.
I hope I can find one, and pray that's all that went poof !
Paul K2DB



Re: Problem with BPF

GM7
 

Hi Allison,

That's interesting.  I was assuming that there was a more fundamental problem but it sounds like that might be wrong?

The initial curve I had looked like a good BPF response and was on the center frequency it was designed for.  Is it still possible to achieve that and be badly tuned?  I had assumed it wasn't but it is just an assumption.

I measured the inductors when I wound them and removed turns to get them to the correct values.  They have quite a bit of adjustment available by squeezing or compressing the turns.


Re: Problem with BPF

GM7
 

Ron, Geoff

I agree with you but I just can't see it.  I've attached some photos of the BPF.  It's tricky to photograph so I'm not sure how useful they will be.


Re: Problem with BPF

ajparent1/KB1GMX
 

Its just not tuned.

Double tuned band pass filter tend to be hard to get right as tuning one side does interact with the other.
Often I shows as a hump well off to one side is badly tuned and if close but not quite, high loss in
the desired band and maybe a badly shaped skirts.

Note the trimmers are relatively small value so if far off (inductor or padding cap) you will not have
enough range of variable cap to correctly tune.

Allison
-------------------------------
Please reply on list so we can share.
No private email, it goes to a bit bucket due address harvesting


Re: Problem with BPF

GM7
 

The BPF doesn't look so good.  

The BPF Out in particular is completely wrong with an impedance of 0.  

I'm not sure if the BPF In looks reasonable?


Re: OOPS ! 50 Watt Amp

K2DB Paul Mackanos
 

Found  FQPF2N60C, TO220, MOSFET at DigiKey, $1.16 each + $4.99 shipping, ordered a few extras.
Paul K2DB

On Sun, Jul 5, 2020 at 1:12 PM K2DB Paul Mackanos via groups.io <paul.mackanos=gmail.com@groups.io> wrote:

Update on OOPS ! 50 Watt Amp

Here is a high def picture with a computer microscope showing a burn mark directly above  Q3 FQPF2N60C, TO220, MOSFET.
I hope I can find one, and pray that's all that went poof !
Paul K2DB



Re: QCX+ alive!

Dean Smith
 

Can't say i had any problems with IC/Resistor placement, i agree it is a little cozy as is C39, the nearest resistor to IC3 is R1 with R2 behind it.
Maybe something for a future revision, tbh i didn't notice on assembly.
IF.....,IF i had to have a grumble,, The LCD fitting nuts'n'bolts are more of a pressing concern. The bolt nearest the Encoder has little space for the nut/spacer ,between the back of the lcd and the backplane pcb. I used plastic M3 nuts all round here to avoid any shorts/overtightning ect. the 16 way molex pins plastic spacer provides the correct gap, anyhow. I'm sure if Han's has already assembled one without the air turning blue,then things will be ok. Just a personal preference:). the one good thing about a pluggable front on the radio, is it helps to assemble without half the kit hanging of it. And those of you still waiting for the kit, you'll not be disappointed! The kit IS the mutts nuts!
Dean (G7EOB)


OOPS ! 50 Watt Amp

K2DB Paul Mackanos
 


Update on OOPS ! 50 Watt Amp

Here is a high def picture with a computer microscope showing a burn mark directly above  Q3 FQPF2N60C, TO220, MOSFET.
I hope I can find one, and pray that's all that went poof !
Paul K2DB


_._,_._,_


Re: Problem with BPF

geoff M0ORE
 

Looks like Ron beat me to it, I was about to suggest that one or both transformers were wired back to front.i.e. the primary and secondary windings were reversed. This could give a good frequency response but high loss.

On 05/07/2020 17:12, Ronald Taylor wrote:
Is it possible that on one end or the other you got the transformer primary wire in the secondary hole and vice versa? 

Ron

On Sun, Jul 5, 2020 at 08:52 HB9FIH <erich.rieder@...> wrote:
I also had issues with low pwr.
Now have a VNA and will soon check the BPF and fix them.
Own 2*20m and 2*40m.
I am enthusiastic operating with them, asap I moved to SV8 / TA3 and plan to partcipate by challenges again.
--
---
73 de Erich

HB9FIH

HS0ZLS


Re: Problem with BPF

GM7
 

Geoff, Your last post was really helpful.  I'm going to split my reply into two to avoid confusion between the LPF which works as expected and the BPF which is the one I'm struggling with.

I used the setup you described.  My first test was a dummy load.  While it's not an ideal response it does look good.  Note I still had the test fixture in place for this test with a straight-thru connection which explains part of the non-linearity.  This is probably more realistic because it's how I test the filters.

I then tested the LPF in both directions and got good response and good symmetry.  The impedance looks pretty much spot on too.  By 'LPF In' I mean the VNA connected to the IN of the LPF and the dummy load connected to the OUT.

Thanks to everyone else for their suggestions.

.



Re: QCX+ alive!

Hans Summers
 

There isn't any problem.
The supplied resistors fit just fine. 
I could move the resistors away a few mils yes but as it is, there is no problem with assembly. 
Try it and see :-)

73 Hans G0UPL 

On Sun, Jul 5, 2020, 19:10 John Baines via groups.io <jbaines=mac.com@groups.io> wrote:
Or use physically smaller resistors?

72/73
John
M0JBA

On 5 Jul 2020, at 17:05, Evan Hand <elhandjr@...> wrote:

Maybe mount the resistors on the other side of the board?

73
Evan
AC9TU


OOPS ! 50 Watt Amp

K2DB Paul Mackanos
 

Before I open it up, I installed Anderson Power poles on a 12 AWG red/black cable I purchased with the power pole kit and crimper.
Great move, but
DUMB operator, i put the black wire in the red connector and red one in the black connector.
You know what happened, right, reversed the polarity. 20 volts going the wrong way.
Heard a pop, and nothing happened. 
Fixed the error and powered it up again, no output, any ideas what i am going to find, YL just brought me a bite to eat, and asked me what's wrong :-)
Gonna eat, and then open it up and look.
Paul K2DB
p.s. It worked fine before the snafu.Got 50 watts out.


Re: Problem with BPF

Ronald Taylor
 

Is it possible that on one end or the other you got the transformer primary wire in the secondary hole and vice versa? 

Ron

On Sun, Jul 5, 2020 at 08:52 HB9FIH <erich.rieder@...> wrote:
I also had issues with low pwr.
Now have a VNA and will soon check the BPF and fix them.
Own 2*20m and 2*40m.
I am enthusiastic operating with them, asap I moved to SV8 / TA3 and plan to partcipate by challenges again.
--
---
73 de Erich

HB9FIH

HS0ZLS


Re: QCX+ alive!

John Baines
 

Or use physically smaller resistors?

72/73
John
M0JBA

On 5 Jul 2020, at 17:05, Evan Hand <elhandjr@...> wrote:

Maybe mount the resistors on the other side of the board?

73
Evan
AC9TU