Re: QCX 17m PA problem

Axel

Hi,

I had problems with low output power, too, and want to report what I did to fix my problem. Maybe it helps other people.

My QCX is for 20 m.

I removed c29 and measured the LPF with a VNWA. Edge frequency of the LPF was a little to low and I removed 2 windings from L1, L2, L3 each to get the desired filter response. This didn't increase output power significantly.

You can transmit even with the LCD module removed.

I reinserted C29 and put 50 Ohms to output.
With an oscilloscope, I measured voltages at output (Vout) and across C25 (V25) and C26 (V26).

For ideal components (exact value, no losses) it should be (20 m):

V26 = V25
V25/Vout = 1.36

I measured:

V26/V25 = 1.27

Power loss is approximately:

(V26/V25)^2 = 1.6
meaning about 60% of power is lost between C26 and C25. That's much.

V25/Vout = 1.44
should be 1.36

Power loss:
(1.44/1.36)^2 = 1.13
meaning 13% of power is lost from C25 to output, not to much.

I replaced C25 and C26 by NP0 (C0G) SMD capacitors (NP0 SMD was easier to get than THT).

I damaged (not completely destroyed) 74ACT00, resulting in high somewhat lower output power and about 0.22 A RX current. (78L05 getting hot).
I replaced 74ACT00 and put it on a cheap socket (seems to be no problem).

Now:

(V26/V25)^2 = 1.23
meaning about 23% of power is lost between C26 and C25. Significantly better now.

Other measurements now (20m):
Vdc = 12.1 V (at output of reverse polarity protection diode)
Idc = 0.35 A (TX minus RX)
Pin  = 4.2W (Tx minus RX)

V26 = 26Vp
V25 = 24Vp
Vout = 17Vp

Pout = 2.9W

Hope it helps
Axel DF1ET

Re: #QCX : Is toroid's manufacturer Amidon?

Axel

Thank you for the hint. - I now found out, that while doing my measurements I accidentally damaged (not completely destroyed) the driver IC 74ACT00 and hence missinterpreted the result. Significant power loss didn't result from toroid cores but from capacitors.

Axel

Re: VFO Output – Is This Right???

Richard G4TGJ

What's the bandwidth of your scope? A square wave is formed from a lot of harmonics so if they are being attenuated then it won't stay square.
--
73
Richard
G4TGJ

Re: QCX Message Preset Programming

Alan G4ZFQ

What is the procedure to program the QCX message program using paddles?
Marc,

Reading the manual 4.17, 4.18 might help.

73 Alan G4ZFQ

Re: Add Power Switch to my QCX Enclosure

Steve in Okinawa

These cutting drills make short work of irregular holes in plastic and soft metal. This set was only a few dollars on eBay.

Re: Add Power Switch to my QCX Enclosure shapes

Steve in Okinawa

these cutting drills also make short work of irregular shapes in plastic and soft metals. They are best used in a drill press. The set was only a few dollars on eBay.

VFO Output – Is This Right???

pietromartini2007@...

I built the VFO/Signal Generator kit with no problems, and it started up right away. However, the output waveforms and amplitudes are not what I expected; according to the manual, they should be square waves with an amplitude of 3.3V p-p. Taking the output from the CLK0 pad, what I see on my scope is sort of a square wave at 3.5 MHz with a lot of overshoot and undershoot, and as the frequency increases the waveform becomes more of a triangle and the amplitude steadily decreases, until it’s only 246 mV at 150 MHz, and the waveform is almost a sine wave. I don’t have any load on the output, and I attached the scope probes directly to the CLK0 pads. If I had to guess I’d say stray capacitance may be the culprit. So can someone tell me if I have a problem with my build? I’m attaching a few photos of the scope images.

10 watt amplifier by KA6PSD

rbeswick@...

I just finished the transformers this evening. Had to put on my glasses to see clearly,  the toothpick trick worked flawlessly. Now to find a quiet time to solder them in. Used a sharpie to color the primary wires for easy identification and marked the torrid wire the sharpie to identify the 5 from the 6 winded transformers. It will be a slow build as the eyes need breaks, and slow and steady wins the race.
I will keep everyone informed as I go along.
Robert KA6PSD

QCX Message Preset Programming

MA

What is the procedure to program the QCX message program using paddles?

Marc
call: WA9ZCO
cell: (920)671-4266

--
Marc

Re: Shipping route question

ajparent1/KB1GMX

Start in Turkey as theat is the home of QRPLabs..

The Jamaica NY center is likely one of the busiest for international
shipments.

3 weeks is normal.    Two weeks would be incredible luck.

Allison

Re: Shipping route question

N3MNT

See shipping information on the QRP labs web site.  It explains the Turkey question and also gives very current min avg and max ship times to all over the globe.

Shipping route question

This probably comes off as whining but it's not. It'll get here when it gets here. I'm in no particular hurry. I just thought the starting point and time spent in NY was odd. It's been a while since I've ordered so maybe this is the new normal?

Back on the 8th I ordered a few things from QRP Labs (and again today). According to tracking, here's the route it has taken so far:

June 11, 2019, 8:52 am
Acceptance
TURKEY

June 13, 2019, 2:28 pm
Processed Through Facility
ISTANBUL PAKET MERKEZI, TURKEY

June 13, 2019, 4:42 pm
Processed Through Facility
ISTANBUL ULUSLARARASI POSTA ISLEM, TURKEY

June 19, 2019, 2:10 pm

Processed Through Facility
ISC NEW YORK NY(USPS)

Customs (doesn't say where)

June 21, 2019, 7:31 am
Arrived at USPS Regional Facility
JAMAICA NY INTERNATIONAL DISTRIBUTION CENTER

13 days and counting. This is looking like a 3 week ship time. Is that normal? I just ordered a couple of QCX kits. Based on the order I placed on the 8th I decided to lead the target a bit and aim for where I think I will be in 3 weeks, not two.

Why did it start in Turkey?

It's been hanging around NY for a while. Maybe that's the norm for international shipments these days? In the US, the longer something stays in the shipping system, the greater the likelihood of it being destroyed or lost so that's a concern. Hopefully time spent in NY isn't a direct correlation to travel time remaining.

--
73
NE5U

Mike

Alan de G1FXB

Joe,
Good to hear it's back to full health.

regards alan

On 21/06/2019 19:45, Joseph B Cotton wrote:
Alan
Thanks for the update.? My rig is one of the early models, I think my serial number is 700 something.? I was able to get the rig to be as sensitive as my "big" rig - FT-891.? I have an antenna switch and can switch my antenna back and forth between both rigs.? Both seem to hear the same weak signal evenly.??
Joe W3TTT

Re: Add Power Switch to my QCX Enclosure

Ken KM4NFQ

This is how I cut a rectangular hole in a plastic box lid for an LCD. You might be able to adapt this method to making a rectangular hole for a rocker switch?

Regards,
Ken, KM4NFQ "Not Fully Qualified"

On Thu, Jun 20, 2019 at 3:54 PM John <johnk2jhu@...> wrote:

Thanks to those that replied to my on-off switch question. I am defiantly going to make this mod. I have a small rocker switch I’d like to use but will require a rectangular hole and not sure I can cut it in the plastic case. I’ll have to contact the builder if the case for his advice.

Have a great Field Day weekend.

73 John K2JHU…

Re: Add Power Switch to my QCX Enclosure

Tim Glennon

The way I added a power switch is by replacing the volume control pot with one that has a switch on the back. Now I just turn the volume control from the stop to the listening level I want. When done I just turn the control down until it clicks and the unit is OFF

73
Tim
KQ4TQ

Joe Cotton

Alan
Thanks for the update.  My rig is one of the early models, I think my serial number is 700 something.  I was able to get the rig to be as sensitive as my "big" rig - FT-891.  I have an antenna switch and can switch my antenna back and forth between both rigs.  Both seem to hear the same weak signal evenly.
Joe W3TTT

Re: Add Power Switch to my QCX Enclosure

Joe Cotton

Very Nice.  I used a toggle switch, cause thats what I had in the parts box.  Also, I like your KEY button.  Looks like you used hardware similar to the other two buttons.
73 Joe W3TTT

Re: Pneumatic antenna lanuchers

HF

I made and used one like Braden's for a while until I borrowed my friend's pneumatic launcher.  I'm too weak to shoot an antenna higher than 15 meters with my slingshot.  Building my pneumatic launcher required learning how to glue PVC pipe together which was much easier than I expected.  I used a \$15 sprinkler valve meant for 24V operation (it works with much lower voltage than that). I put some nuts and bolts into an eye drops bottle and tied the fishing line to it as a weight.  It fits perfectly into the nominally 1-inch schedule 40 output pipe.  I used a \$7 fishing reel with the 8-pound test line that came with it.  This launcher shoots higher than the very tall cedars and firs around here in northern Cascadia.  The 40-gram weight pulls the fishing line down over the branch, then I tie stronger line to it and pull it back.  Finally, I tie 1/8 inch polyester rope as a halyard to the stronger line and pull it through the third time.  I hope this summary helps the next person launch waves from the top of the canopy.  If anyone has ideas on how to make one of these launchers with total mass less than 500g, please chime in!  I want to build a version to take on backpacking trips with the QCX.
-Halden VE7UTS

Re: Large inductors in GPS supply and data lines ?

It appears I may have lapsed a bit in my thinking, and created a problem.

Hopefully this weekend I will try another way of reducing noise.

73 de Andy

Re: Pneumatic antenna lanuchers

DK

I had a student once ask me if he could bring his Linear Vegetable Accelerator (LVA) to my college chemistry lab.

We turned his LVA into a lab experiment ( more of a physics experiment, but what the heck) by estimating the flight path of a potato as a function of air pressure used in the LVA.

We abruptly stopped the experiment when the potatoes flew over the distant trees and into moving traffic.

Science is fun!!!

DK. KD6TK

On Jun 21, 2019, at 6:44 AM, jjpurdum via Groups.Io <jjpurdum@...> wrote:

I used one of these a long time ago and I'm pretty sure the lead weight is in near-Earth orbit as we speak...

Jack, W8TEE

On Friday, June 21, 2019, 9:18:08 AM EDT, Braden Glett <bradenglett@...> wrote:

Here is my trusty antenna launcher that has served me long and well. Lightweight, cheap (all parts available at the sporting section of Walmart), and accurate. Also easy to prevent overshooting.