Date   

Re: 50 Watt Amp Final Transistors

George Korper
 

Thank you;

will do!


On Sat, Feb 29, 2020, 12:26 PM Hans Summers <hans.summers@...> wrote:
Hi George 

I tested 6 different supplier IRF510 before choosing the one used in the QRP Labs kits. It's not one you will be able to buy in single quantities without going through all that extensive testing again. I think you should just get the Digikey IRF510 made by Vishay, Digikey part number IRF510PBF-ND, I'm sure it will be fine. 

73 Hans G0UPL 

On Sat, Feb 29, 2020, 20:28 George Korper <georgekorper@...> wrote:
Hi,
I need a trusted source and part number with link for the best replacement 
IRF 510 finals. 
Thanks,
George


Re: 50 Watt Amp Final Transistors

Hans Summers
 

Hi George 

I tested 6 different supplier IRF510 before choosing the one used in the QRP Labs kits. It's not one you will be able to buy in single quantities without going through all that extensive testing again. I think you should just get the Digikey IRF510 made by Vishay, Digikey part number IRF510PBF-ND, I'm sure it will be fine. 

73 Hans G0UPL 

On Sat, Feb 29, 2020, 20:28 George Korper <georgekorper@...> wrote:
Hi,
I need a trusted source and part number with link for the best replacement 
IRF 510 finals. 
Thanks,
George


50 Watt Amp Final Transistors

George Korper
 

Hi,
I need a trusted source and part number with link for the best replacement 
IRF 510 finals. 
Thanks,
George


Re: LED question

George Korper
 

Thanks Alan. Just the answer I needed.


On Sat, Feb 29, 2020 at 10:06 AM Alan G4ZFQ <alan4alan@...> wrote:
George

> What is the spec for 3 mm LED that is on the board?

It must be an ordinary high brightness LED. 470 ohms in series from 5V
is not going to damage any other LED. Ones that are not so high
brightness will just be dimmer.

Bending the leads must be done carefully, hold the wire close to the LED
with fine-nose pliers. Do not overheat when soldering.

73 Alan G4ZFQ

> There seems to be  differences in quality for this 'Generic" part,
> I was careful in bending the original, Not sure bending the lead as
> pictured
> is the best method. I think I should have  bent it around a knife blade.
> I could have also left  it a teeny tiny bit above the board, to keep
> from stressing it in alignment with the case
> and used a tweezer in the process.




Re: LED question

Alan G4ZFQ
 

George

What is the spec for 3 mm LED that is on the board?
It must be an ordinary high brightness LED. 470 ohms in series from 5V is not going to damage any other LED. Ones that are not so high brightness will just be dimmer.

Bending the leads must be done carefully, hold the wire close to the LED with fine-nose pliers. Do not overheat when soldering.

73 Alan G4ZFQ

There seems to be  differences in quality for this 'Generic" part,
I was careful in bending the original, Not sure bending the lead as pictured
is the best method. I think I should have  bent it around a knife blade.
I could have also left  it a teeny tiny bit above the board, to keep from stressing it in alignment with the case
and used a tweezer in the process.


Re: clock and gps #clock

Carl NQ3U
 

Don,
when I built mine, being a typical guy, I didn't read the manual very closely.  When I powered it on and got past the diagnostic screen the clock started and I was getting indications that the GPS was receiving signals, but no LAT/LON displayed!!!  I spent some time looking at all the boards, components, soldering, and everything looked correct to my eyes.  It was a little confounding until I RTFM, Page #8 GPS mode Settings are initially 0 - GPS is not used at all. The kit is in free-running mode, it will run from it's 20MHz crystal oscillator.  I changed that setting to 2 and PRESTO, I magically got LAT/LON displayed.
There are also some programming hints and examples of how others have programmed their displays on the QRP Lab Web site.
I immediately upgraded my display from the 2 line display to the 4 line display and love it.
I'm still working on a custom case layout for it.  The case is the difficult part for me.

73,
Carl
NQ3U 


Re: clock and gps #clock

David G4DMG
 

And you need to set the GPS flag in the menu.


LED question

George Korper
 

I want to replace a defective LED in my 50 watt amp, 
I purchased a replacement that is much less intense and burns out.
What is the spec for 3 mm LED that is on the board?
There seems to be  differences in quality for this 'Generic" part,
I was careful in bending the original, Not sure bending the lead as pictured 
is the best method. I think I should have  bent it around a knife blade.
I could have also left  it a teeny tiny bit above the board, to keep from stressing it in alignment with the case
and used a tweezer in the process. 


NoGaQRP Stands

Paul Kelley
 

I wanted to announce changes to the North Georgia QRP Club (NoGaQRP) NoGa Stands. This includes hand crafted stands for the Elecraft KX2, KX3 and other QRP rigs.  There are several choices that hold both the KX3 and PX3 panadapter as a single unit.  Also, there is now available a new stand designed specifically for the QCX Transceivers offered by QRP Labs  (https://www.qrp-labs.com/).   NoGaQRP Stands can be viewed and ordered on their website at www.nogaqrp.org/mainmenu.html#products



Re: clock and gps #clock

Don Blachura
 


Got it.

Tu
...w2xb


Re: clock and gps #clock

N3MNT
 

You should see “Diagnostic Mode on start up until you program it.
You decide what you want in the 16X2 blocks on the screen then have to program it per operation manual.  If you want the heartbeat you need to program it using the two sets of buttons.  Take an hour or so and read the operation manual it pretty easy.


Re: clock and gps #clock

Don Blachura
 

When do I see the lil heart beat?
Getting the green flashing light. Do 

















When do I see the heart beat from sat? After I set it up?
All this is very new to me.

Don..w2xb








Re: clock and gps #clock

N3MNT
 

Decide what you want to display on the 2 lines).  Write it down on paper, 16 characters/ spaces long by two lines.
Print the Operation Manual and us it to program when you want on the display.  Write the program steps on paper then just follow the program steps.


Re: BPF 80m

DL2ARL
 

Hello,
I can confirm the insertion loss stated above for the 80m BPF, the one intended to work with the U3S Rx (not the one in the QCX). As you can see in the picture attached , my BPF had even slightly more insertion loss than that the 5dB of DK3UW above.

I can not confirm the behavior of the trimmers: mine worked as intended, did what they are supposed to do. But one has to know where to look after the effect of turning the trimmers: the S21 transmission curve (red in the picture attached) does hardly changes it's absolute position. To see what the trimmers do you have to watch the S11 reflection curve (blue in the picture). The effect of the individual trimmers is clearer to be seen watching the two distinct "dips" of the S11. This is the nature of the beast.

The blue curve showing the reflection factor S11 at the input of the BPF also tells us something else. The reflection factor in the middle of the curve is about 30% on the linear scale chosen (corresponding to a 10dB Return Loss or, if you prefer, to a VSWR of abt. 1,8).  With these figures in mind one can say that the mismatch is the cause of some of the insertion loss. This assumption is right, but the loss due to a VSWR so low is only about 0,4dB, not more.

Probably the rest of the uncommon high insertion loss comes from the red toroids used. I have experimented changing the fixed capacitors with no success and the trimmers will be the same (not checked).

The -3dB bandwidth of the BPF being almost a half of MHz (well suited for the purpose), increasing the coupling to decrease the insertion loss is not an option. There must be something in there eating up the Q Factor: the design is straight forward and can not be blamed.

But the issue is of no concern, at least not for me. As Hans states in the manual, the filters are a huge field for experiments. Myself, intending to use the Rx together with an U3S WITH a LPF multi band switching board, I think of replacing the BPF with a HPF. What do I mean by that? Let me explain:

Using a multi-band U3S with a monoband Rx would be a "no-brainer". Unless there will be somewhen a switching board for the BPF's too, I think of following: Replacing the BPF  with a 5 or 7 pole High Pass Filter (HPF) with a cut-off frequency of about 3,2..3,3MHz would get me rid of that nasty QRM coming from below, all those switching power supplies, computers and what's left from the poor good old AM Radio.

Together with the LPF that is in front of the U3S, the "combo" would give me some sort of Band Pass Filtering, at least for the lower bands (80..60..40..30m) near the cut-off frequency of the HPF. Yes, I know, there is lots of QRM in-between those HPF-LPF corners, but ... I think I can live with this and I prefer this solution to having to manually change the BPF each time I change the band of the U3S. Used for band observation, his Rx is not supposed to become my ultimate DXCC chaser. Any better ideas welcomed however.

Thank you for the bandwidth!
73, Razvan DL2ARL


clock and gps #clock

Don Blachura
 

Hello Folks,
I need a hand on setting the clock and gps. The clock and gps works(getting 3 lights  green and yellow blicking),
and dashed lines in the beginng. What is the first thing I should do?

Don..w2xb


Re: OLED screen for QCX

Dean Smith
 

Ok noted Luis! Proves there's more than one manufacturer of these devices.


Re: OLED screen for QCX

Luis Fernandez
 

BEWARE that Raystar has identical OLED modules than Winstar. BUT they reversed the +5V and GND pins
So, if you just insert is as a replacement of a standar LCD or Winstar you will get some smoke

I have been testing a Raystar REG010016DYPP5N00000 with U3S (not QCX) and timing is so different that it doesn't work

73 de Luis
EA5DOM


Re: How much power to drive 50W amp?

Ronald Taylor
 

John, the input pad is only 3 dB loss and is there to protect the transistors from overload. It has another purpose though, which is to provide a reasonable approximation of 50 ohms to the QCX driving it to keep things stable. It is best practice to leave it in. You may see 25-30 watts output anyway but if you want full performance your best bet is to try for more power out of the QCX by adjusting turns on the lowpass filter toroids (L1-L3). Start by spreading the windings as far apart as you can. If that doesn’t work try removing one turn from each. 

Good luck .... Ron

On Fri, Feb 28, 2020 at 06:49 John Brock <brock71@...> wrote:
My 20M QCX is a little low on power. About 2.8W.
Wondering if that is enough to drive the 50W amp?
I see there is an attenuator on the amp input. Could modify that for lower input power.

John
WA8US


Re: Qcx 40 meter with 50 watt amp

ohwenzelph
 

Can you post a pic?


How much power to drive 50W amp?

John Brock
 

My 20M QCX is a little low on power. About 2.8W.
Wondering if that is enough to drive the 50W amp?
I see there is an attenuator on the amp input. Could modify that for lower input power.

John
WA8US