Date   

QRP-LABS Low Pass Filter upgrade

J P Watters
 

Hans,

I found in past posts that your LowPass Filters could safely handle 10 Watts.

I have a 1.8mhz-54mhz 100W amplifier that I am searching to add switchable LPF's to it.

Is it possible to update your LPF's to handle 100W? If so can you recommend the components to do so.

..jpw J P Watters
KC9KKO
Morris, IL USA


Re: getting high voltages #problem #building

will.koenig.rn@...
 

Alan,
I'm not sure if the display still works, I unplugged power as soon as I saw smoke, and IC3 immediately starts smoking once power is supplied.  I will replace Q1-3, Q6, and IC3 and then try. 
Thanks
Will


Re: getting high voltages #problem #building

will.koenig.rn@...
 

KN6HGG,
  I did have a dummy load attached. I had plugged the GPS in prior to plugging in power, but the lights on the GPS didn't power up, so when I wiggled the leads from the GPS, they slipped out of the pads and must have shorted something.  


Re: 80 meter bpf toroid winding 30 turns givel 4.3 micro Henrys, not 3.8

@CurtisM
 

take another careful look - if any apparent damage is limited to the low pass filter section of the board, with a little wire you can replace the traces.  many of us struggle somewhere on these kits.  also, note most of us assemble and get things working without a nanoVNA (I need to learn how to use the calibration functions - even though I have been using VNA's since 1979 !).  best to slow down and figure things out, and maybe not presume that things are way off (I did remove one turn from the end toroids on my 80m QCX, but I think I gained less than a half watt - I am thinking they are okay as is - especially when I decide to drive the PA, being assembled just now - but it was doing nicely last evening at 3.5 watts out). 

I hope you are regrouping - and perhaps ordering another QCX+ for a different band?  oh yes my original 40m QCX sits in sick bay awaiting a PLL chip ... best to keep a reasonable pace with these things. 

73 curt wb8yyy


Re: Alignment Troubles #qcx #20m #alignment #bpf

@CurtisM
 

Conner

let us know what it up with your rig, and okay to email me direct (see qrz) if you are still having issues. 

C1 tends not to be extremely sharp - but I have no personal experience with the 20m QCX.  its purpose is to match the receive input to the antenna and it forms a bandpass filter.  the other controls are much more vital to receive performance. 

when you mentioned the trimmer cap resonating on each end it got our attention, but perhaps I over-reacted. let us know where things are with your rig. 

73 curt wb8yyy


Re: QCX+ and N1MM+

Bruce K1FFX
 

I also was unable to get N1MM+ to run reliably with my QCX+ 40m.  I found the QCX+
CAT feature was very stable with just about any other logging software (and I tried
lots of them ... I just really disliked them all after several years of using N1MM).

However, in today's experiment, I discovered that N1MM+ has a rig definition named
KENWOOD-SLOW.  With that setting, N1MM+ and the QCX+ have been happily
talking to each other for a half-hour now, whereas with the TS-480 setting, the
connection would time out within a minute or two.

I installed a port sniffer to try to understand what was going on.  For the TS-480
setting, N1MM+ sends a bundle of commands:

IF;FA;FB;AG0

With N1MM+ set to its slowest poll setting ("100% slower"), this would work for a while,
and then the QCX+ would stop responding.

With the KENWOOD-SLOW setting, N1MM+ sends one command at a time:

IF;
FA;
FB;

at whatever the polling interval.  Even with the polling interval set to "normal", the connection
has not timed out.  However, I did find that occasionally, setting the frequency in N1MM+
would set the new frequency and then bounce back to whatever the QCX+ had been set to
previously ... probably some race condition between the SET and GET commands (?).

Anyway, with the radio set to KENWOOD-SLOW and polling rate set to "50% slower", it's
been running fine for close to an hour now.

FIngers crossed that this is a permanent solution!

I thought other N1MM users would be interested.

- Bruce K1FFX

 


Re: Select Button on Alignment QCX+ 20m

Steven Dick
 

The buttons are all multiplexed on a single line to share a single ATMega328p pin due to pin limitations.  See schematic explanation page 163 of the QCX+ manual.  If you have power on and, on the front panel,  you look at the ungrounded side of R46 (10K), you should see zero volts if nothing is depressed, +5V is the rotary encoder button is depressed, about 4.5 volts if the right button is depressed, and about 3.76 volts if the left button is depressed. You cal also look at the ATMega328p pin 26 for these voltages. There may be a bad solder joint or wrong values or intermixed R44, R45, or R46 resistors. If the voltages all look good, then with power off, do a direct resistance measurement from the ungrounded side of R46 right to the ATMega328, pin  26. It should be zero ohms or you have a bad solder joint or front panel connectors not fully mated.

-Steve K1RF

------ Original Message ------
From: "Glen Sr" <ghazen1@...>
Sent: 9/7/2020 4:22:21 PM
Subject: Re: [QRPLabs] Select Button on Alignment QCX+ 20m

Richard. I have the same problem. I can raise and lower the audio noise also. Glen n8we
 
From: Richard M0AUW
Sent: Monday, September 7, 2020 1:11 PM
To: QRPLabs@groups.io
Subject: [QRPLabs] Select Button on Alignment QCX+ 20m
 

I’ve Just completed my 20m QCX+, it booted up fine showing 20m in the LCD, but when I went to press the select button to get Preset nothing happens. The LCD is working and showing the correct freq and when pressing the other buttons, I get a reaction. So, it seems to be just the select button. If the LCD is working could it be a problem with the 328 microcontroller?

I have checked R44 and R45 and searched the whole board for any bad solder joints, especially the button joints, all seems OK. Any ideas?

 

Many thanks Richard M0AUW


Virus-free. www.avast.com


Re: Select Button on Alignment QCX+ 20m

Glen Sr
 

Richard. I have the same problem. I can raise and lower the audio noise also. Glen n8we
 

From: Richard M0AUW
Sent: Monday, September 7, 2020 1:11 PM
To: QRPLabs@groups.io
Subject: [QRPLabs] Select Button on Alignment QCX+ 20m
 

I’ve Just completed my 20m QCX+, it booted up fine showing 20m in the LCD, but when I went to press the select button to get Preset nothing happens. The LCD is working and showing the correct freq and when pressing the other buttons, I get a reaction. So, it seems to be just the select button. If the LCD is working could it be a problem with the 328 microcontroller?

I have checked R44 and R45 and searched the whole board for any bad solder joints, especially the button joints, all seems OK. Any ideas?

 

Many thanks Richard M0AUW


Re: Select Button on Alignment QCX+ 20m

@CurtisM
 

Richard

also check the solder where this path connects with the microcontroller - few of us complete a QCX+ without missing one solder joint at least partially (for me it was a connection to the highpass pot).  glad you are almost there - look and check carefully - and enjoy the wonderful alignment experience. 

73 curt


Re: QSX+ on 10m or even 6m?

geoff M0ORE
 

Another typo??

On 07/09/2020 15:52, Dean Smith wrote:
Anyone managed it? or are there limitations ie LO frequency, deafness ect?


Re: Select Button on Alignment QCX+ 20m

Alan G4ZFQ
 

I have checked R44 and R45 and searched the whole board for any bad
Richard,

Check voltages on pin 25 of the 328 when pressing the buttons. Button presses give different voltages.
I'm not sure but they should be mentioned somewhere in the manual.

73 Alan G4ZFQ


Re: Select Button on Alignment QCX+ 20m

Gary Bernard
 

I had the same problem, turned out it was a cold joint on the button.


-----Original Message-----
From: Richard M0AUW <cotswoldgent@...>
To: QRPLabs@groups.io
Sent: Mon, Sep 7, 2020 11:11 am
Subject: [QRPLabs] Select Button on Alignment QCX+ 20m

I’ve Just completed my 20m QCX+, it booted up fine showing 20m in the LCD, but when I went to press the select button to get Preset nothing happens. The LCD is working and showing the correct freq and when pressing the other buttons, I get a reaction. So, it seems to be just the select button. If the LCD is working could it be a problem with the 328 microcontroller?
I have checked R44 and R45 and searched the whole board for any bad solder joints, especially the button joints, all seems OK. Any ideas?
 
Many thanks Richard M0AUW


Select Button on Alignment QCX+ 20m

Richard M0AUW
 

I’ve Just completed my 20m QCX+, it booted up fine showing 20m in the LCD, but when I went to press the select button to get Preset nothing happens. The LCD is working and showing the correct freq and when pressing the other buttons, I get a reaction. So, it seems to be just the select button. If the LCD is working could it be a problem with the 328 microcontroller?

I have checked R44 and R45 and searched the whole board for any bad solder joints, especially the button joints, all seems OK. Any ideas?

 

Many thanks Richard M0AUW


Re: Unknown component board

KN6HGG
 

Yep, boost or buck converter with adjustable voltage+current, and a high wattage one judging by the inductor size. Most likely boost converter, but the easiest way to find out is to hook it up and use a multimeter!


Re: Alignment Troubles #qcx #20m #alignment #bpf

Ronald Taylor
 

Connor, 
"Added a 104 cap where C5 goes, and the BPF moved to an "8" and stayed there. Did not change at all in reaction to trimmer setting with the extra cap in place." - 

A 104 capacitor is 0.1 uF or 100,000 pF. Putting that across a 30 pF (max) trimmer in a circuit meant to be tuned to 14 MHz will drop the resonant frequency of that circuit to about 240 KHz. And the little 30 pF trimmer will have no additional effect on that much capacitance no matter where you set it.

Make sure that when you measured for T1 winding continuity across C1, you didn't measure between the two outside pins of the trimmer. These are connected together and will indicate 0 ohms. Measure between one of the outside pins and the center one. Better yet, just measure across the new 104 that you added. Or the open pads for C6 would work as well. In this way, you are looking for continuity through the large winding of T1. I still don't think you have it.

I'm glad you were able to do the 3 null adjustments and you got to 8 on the BPF but the BPF is not tuned at this point and will not be an effective bandpass filter, so if you want it to be correct, remove the 104 capacitor, find this issue with the large winding on T1 and tune it up. If it receives well as is and doesn't suffer from interference from broadcast stations, then enjoy it as is... Your choice ... Good luck ...Ron


On Mon, Sep 7, 2020 at 12:03 AM <connor.mike7986@...> wrote:
Just re-checked across C1, 0ohms. 
Added a 104 cap where C5 goes, and the BPF moved to an "8" and stayed there. Did not change at all in reaction to trimmer setting with the extra cap in place.
Remelted the solder on the volume pot and double checked connections, so it is fully connected now if it was not before(I didn't check this one prior). Afterwards was able to at least to set the 3 nulls to their minimums.
I will need to wait till the band gets more traffic in the morning to see if I can receive anything.

Connor, W7AOE


Re: Unknown component board

Bruce K1FFX
 


Re: Unknown component board

jjpurdum
 

Pretty sure it's a step-down buck converter.

Jack, W8TEE

On Monday, September 7, 2020, 12:29:11 PM EDT, K2DB Paul Mackanos <paul.mackanos@...> wrote:


Does anybody have any idea what this is, I ordered two of them at one point in time, can’t remember what it was, or what it is for.

Just wondering if anybody can tell me what it is, and how to adjust it because there are two Multiple turn pots on it ?

I’m going to guess a DC voltage buck or boost converter.

Paul K2DB


Re: Unknown component board

Gregg Myers
 

On Mon, Sep 7, 2020 at 10:29 AM K2DB Paul Mackanos <paul.mackanos@...> wrote:
Does anybody have any idea what this is, I ordered two of them at one point in time, can’t remember what it was, or what it is for.

Just wondering if anybody can tell me what it is, and how to adjust it because there are two Multiple turn pots on it ?

I’m going to guess a DC voltage buck or boost converter.

Paul K2DB


Unknown component board

K2DB Paul Mackanos
 

Does anybody have any idea what this is, I ordered two of them at one point in time, can’t remember what it was, or what it is for.

Just wondering if anybody can tell me what it is, and how to adjust it because there are two Multiple turn pots on it ?

I’m going to guess a DC voltage buck or boost converter.

Paul K2DB


Re: 80 meter bpf toroid winding 30 turns givel 4.3 micro Henrys, not 3.8

Arv Evans
 

As mentioned earlier by someone else,  compressing or spreading 
the turns on a toroid core probably does not change the inductance
very much (the number of turns remains the same).  What it does 
do is to change the distributed capacitance between turns.  

Also mentioned by others is that the apparent inductance of metallic 
cores does change with frequency.  This could be a factor if you are 
operating the core at widely different frequencies.

DC loading also causes toroidal cores to change apparent 
inductance.  While probably not an issue with DC isolated 
filters, it could be problematic for tank circuits that carry DC
current.

Arv
_._



On Mon, Sep 7, 2020 at 8:56 AM Kees T <windy10605@...> wrote:
KI7MWA,

If xx turns of #28 wire do not allow moving the turns around a little, try #30 wire.

73 Kees K5BCQ

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