Hi,

I recently completed my QCX 80 kit, followed the instructions to the letter and even measured the resistor/capacitor values prior to installing them. The kit worked first time.? Unfortunately I did not measure the inductor values prior to fitting in the PCB. Because of the s-p-r-e-a-d in characteristics with the inductor cores my QCX suffered a lower than expected output power. It still worked OK but it "niggled" at me that the PA did not meet expectations so I decided the only way to get peace-of-mind was to fix it.

Reading some of the past posts on this forum I see the lower than expected power is quite a common problem and the fix (also described in the build manual) is to remove a couple of turns from each of the inductors.? I have no doubt this works but I did not want to risk damaging the PCB with re-soldering a number of times during the cut-n-try operation. So having a reasonably well stocked junk box I took a spare set of T37-2 cores and wound the number of turns specified for the QCX 80 (L1 25 turns, L2 27 turns, L3 25 turns and L4 24 turns) but this time around I used the QCX as a signal source with a kitchen table lash-up to measure resonance and therfore the value of each inductor with sufficient accuracy so that they matched the values quoted in the build manual.? The result was an instant increase in output power from the much less than 2 Watts I started with to 5 Watts as measured on the QCX. Now my power output-v-supply Voltage curve is close to that shown on page 129 of the manual plus I only had to desolder/replace the inductors ounce. So very happy :-)

While measuring the inductors, removing turns and re-checking the values a number of times the thought struck me that since the QCX already has an in-built signal source it would only take a small number of additional components (and software) to make some sort "peak detector" such that the resonance of each PA stage inductor can be checked while building. This (in conjunction with some simple math and a pocket calculator) would permit the measurement of the inductor values prior to fitting in the kit and also add a usefull bit of test gear to boot. The only "critical" component is a capacitor of reasonable close tollerance to resonate the inductors with (I used 820pF +/- 2%? for resonances around 3 to 3.5 MHz) but the value of the capacitor or the frequency are not that critical so long as both are known in order to work out the value of inductance. It might add a few 10's of cents to the cost of the kit but perhaps well worth it. So, what do you think?

73,s

Des (M0AYF)

On 08/05/2017 00:51, z_ kevin wrote

Sorry, I was too quick,

Actually too slow, I had the posts sorted by sender and I replied to one that showed "unread" from MAY...

73 Alan G4ZFQ

On 08/05/2017 00:51, z_ kevino wrote:

What is the max power I could TX through one of the QRPLabs bandpass filter kits? Will 10w be okay?

Kevin,

Sorry, I was too quick,

The BPFs not much, they are designed for RX.

73 Alan G4ZFQ

On 08/05/2017 00:51, z_ kevino wrote:

What is the max power I could TX through one of the QRPLabs bandpass filter kits? Will 10w be okay?

Kevin,

If you look here it says 10 Watts.

73 Alan G4ZFQ

Paul

Most model aircraft shops or online sell them. I got mine from hobby king.

73

Kevin
G8MXV

Sent from my iPad

Unfortunately, the only cure is to buy a BITX40 and convert it to a multi-band radio with QRP Labs Filters!


--
Ryan Flowers W7RLF

?

?

I could have asked Hans, but I thought I would throw
it out here. A friend is looking for an accurate
10 MHz reference oscillator.

Keith,

How accurate?
I do not think a QRP Labs device is going to compare with a purpose-built GPS or Rubidium. That's what some want.
A good OCXO can give good accuracy and not need an antenna.

73 Alan G4ZFQ

Would the HF Sinewave VFO/SigGen followed by a 30M
LPF with the QLG1 GPS Receiver be a good candidate?
I also thought about the ProgRock, also disciplined
with a GPS receiver, which might be a better choice
as the intended use is for a single frequency.

开云体育

Not perfect but priceless.

I reprogrammed the chip that wasn't working right and it's fine. I used one of my U3s boards. I removed the display, removed the synth board, and used it for programming the chip. I used AVRDudess, followed the steps in the documents section of this site, and it programmed the first time around. "One of these days" I'm going to learn how to use Atmel software and my AVRISP MKII. And then Microchip will release something to replace all of it :o)?

This helped me,but only speaking for myself using 328p chips and Pocket AVR programmer -

After reading everything else...you eventually get it figured out.
Jim,N2NXZ

On Sat, Nov 25, 2017 at 02:34 pm, John Kirby wrote:

There can be no perfect QRP radio.....Except the one you design and build yourself...Priceless !

Jim

;

开云体育

For my part I folded flat the locking tab of the metal frame of the display it remains at least 5mm I followed the manual hi 73 jo.

?... my uncurable disorder ...

by Observation
??? There can be no perfect QRP radio
??? and even if there were
??? finding it would not be half as much fun as the search for it;

QCX 80, 40, 20 ... sn 1166, 7, 8 ...arrived 2017nov25

Cricket 80
Pixie 80, 20
ELAD FDM DUO SDR All band, all mode
MFJ 92xx 80, 40, 30, 20, 17, 15, 12
WSPR 30
FT 817 HF, VHF, UHF, All mode
Rock Mite-s, 80, 40, 30, 20
NorCal Sierra All band CW plus n3aaz FSK RTTY mod
NE 40-40 plus n3aaz CW filter es AGC mods
Heath HW 8
RAHB 6L6 40 XTAL plus 80, 40 via VF1
Heathkit VF1 80, 40 (stand alone)

72 73
John
N3AAZ

开云体育

In replying to you Keith, I just convinced myself to order a ProgRock!? I already have the GPS so don't need an extra one of those here.?

I have a GW Instek GSP-810, 150KHz to 1.2GHz spectrum analyzer with tracking generator that I picked up off eBay for under $500 US early last year.? It has provisions for a 10MHz external standard input and I just realized that the ProgRock was a far better option that pulling the GPS DO off my K3S every time I wanted to use the spectrum analyzer - LOL!? If the one on the K3S ever dies, I'll replace it with a ProgRock and then I would get a second QLG1, put it in a plastic box and hang it on the wall.? (It's plenty sensitive to get a good lock even in the house).

Jim - W0EB

The ProgRock would probably be the better candidate but either will work.? I used the QLG1 GPS to do the frequency calibrations on my QCX40 and it matches my K3S which has a GPS Disciplined Oscillator 10 MHz standard on it that cost a heck of a lot more than a QLG1 and ProgRock.

If you decided to go the VFO route, you could get by a bit cheaper by getting the square wave VFO and just adding the 1 30 meter LPF.? The square wave one is the basis of the sine wave one anyway.? They just add the LPF rack and 60-10 meter LPF's (or the LPF's of your choice).?

For that application though, the ProgRock would most likely be the better choice since it's going to be used as a GPS DO on 10 MHz.

Jim - W0EB

I could have asked Hans, but I thought I would throw
it out here. A friend is looking for an accurate
10 MHz reference oscillator.

Would the HF Sinewave VFO/SigGen followed by a 30M
LPF with the QLG1 GPS Receiver be a good candidate?

I also thought about the ProgRock, also disciplined
with a GPS receiver, which might be a better choice
as the intended use is for a single frequency.

--
73 Keith VE7GDH

I followed?Simon's, VK3ELH, guide posted on QRP Labs website. After a few stumbling blocks, I did run AVRDudess tied to a Arduino Uno and goat an error message about the device signature of the chip. The instructions to use ATmega328 but checking the QCX's parts list it turns out being a ATmega328P.? After making that change in AVRDudess the flash process happened and I'm at rev. 1.00d and QCX is working.

The reason I did the firmware update was seeing the wrong frequency in the window during while transmitting a preset message.

Whew! Best of luck flashing!

--Al
WD4AH

"does a failed attempt with USBasp and AVRDude result in a bricked chip, or just another do-over?

As far as I know whatever you use the only way to make a chip inaccessible is to play with the fuses.

? I'm unclear on what drivers (Win7) or firmware the USBasp device /itself/ requires.
I haven't seen the tutorials to which you refer, though I've looked.

My attempt for the USBasp is here tells you the driver and gives two possible programs.

But the group files themselves have options /g/QRPLabs/files and there are others mentioned in past posts.

73 Alan G4ZFQ