Date   

Re: A simple QCX AGC #mods #qcx

Gregg Myers
 

Hi Jim,

Thanks for the thoughtful replies! I am travelling so I was not able to take the mini measurements myself. The potentiometer on the layout I put together is the hi-lighted green square shown in the picture here


So I think it should be accessible with the display removed. The SMD pot I picked out is this one, which Mouser has listed 81-PVG3A103C01R00:

The ground pad is highlighted in purple. I wonder if that might be just the right spot for the ground point you highlighted in your picture. The top of the board has all components except the big 100uF cap and the FET, both of which are on the bottom side. I could move the FET over to the topside and make the board a little longer, but then again I wasn't too worried about components on the bottom since I thought I would just put electrical tape over them so they don't short anything.

73,
Gregg W7GRM

On Thu, Mar 18, 2021 at 11:10 AM Jim AJ8S <aj8s@...> wrote:
Gregg and Jack,

8 x 23 mm is small enough. In fact I measure 10 x 30 mm of space is available. See the attached photo.

I don't see where the potentiometer goes on Gregg's board but you need it to be someplace where it can be adjusted. Mine is accessible from the side over the top of the paddle jack so I can access it when the radio is fully assembled. But the display does not have to be installed for the receiver to run so the pot could lay flat on the board and be accessed from the top. This might be an advantage as vertical real estate is also quite limited. From the top of the TXCO to the underside of the display board is only a little more than 8 mm. If XTAL2 is installed then it is likely even less. Hans might actually have these measurements if he has a mechanical CAD model.

I wonder if making the board single-sided and a little larger might work better? That way it would not have as much vertical extent and the non-conductive underside could be in direct physical contact with components on the main board underneath. 

How to secure the new board in place is another question. There is a ground pin (marked "GND") next to C24 on the main board. There is also one at one corner of the TXCO (or on the main board at the same location if XTAL2 is installed). These points could be used to anchor the added PC board in place with vertical wires. At the transistor end this would mean adding another solder pad on the new board.

Just some thoughts... Hope it helps.

73, Jim AJ8S

.


Re: 10W PA and HackRF #pa

Jim Allyn - N7JA
 

On Thu, Mar 18, 2021 at 04:07 AM, Eike Lantzsch wrote:
mVss is german for mV peak-to-peak

Thanks, Eike!  Looking at possible German words for "peak', I'm guessing in this case the 's' stands for 'Spitze'?


Re: 10W PA and HackRF #pa

Jim Allyn - N7JA
 

On Thu, Mar 18, 2021 at 02:40 AM, Jim Mcilroy wrote:
Vss is ground for many digital chips and FETs
I am aware of that, but clearly that isn't related to measurements of RF power output.


Re: Wowed by WSPR!

N3MNT
 

Glad you are enjoying the magic of small signal propagation. 


Re: Does QCX Mini have DIY emission indication function? #qcxmini

Arv Evans <arvid.evans@...>
 

If connecting a resistor and a diode to output of your transmitter, you
should probably put the resistor between the transmitter output.  This
provides isolation and neatly steps around the ancient myth of diodes
in SWR bridges and RF voltmeters causing harmonics.

There is also the possibility of using a single transistor or mosfet
amplifier to increase output of the diode detector.

Arv
_._


On Thu, Mar 18, 2021 at 9:57 AM <jakob@...> wrote:
Interesting! Are you sure the diodes are 1N4148? I will experiment with this circuit to find out how the led current is generated. Whatever it is, it is most likely a non-linear circuit and induces harmonics, as every non-linear component does in RF. But not a problem if applied before the LPF. BTW, what band is this QCX Mini?


Re: Wowed by WSPR!

tony.volpe.1951@...
 

Great fun isn't it. I did a search and you got 20 hits from VK in this afternoon as the grey line came in. Outstanding for an antenna at the height you describe.

I'd just warn that it's a good idea to keep checking your swr. The pa won't like it if it changes much from bang on perfect. The QCX+ has some heat sinking, but my old school qcx has blown a few PA fets when the antenna went out of tune. This happened because of rain wind and snow on my forty meter horizontal loop. On that I can feel with my finger tip when it is off song. HOT is the word... I'm thinking of soldering transistor sockets to the board so I can just pull them out and replace them. 


Re: 10W PA and HackRF #pa

Karsten Benz
 

Yes, correct, a little bi-lingual mishap: I meant Vpp.

I'll check my my HackRF...

Thanks for all the answers!




--
Karsten Benz - ZL1KPB


Re: Cost of shipping and customs ? ?

Albert Tatlock's Greatest Hits - Vol 1
 

Last month I ordered a U3S.

All arrived fine, 5 days to the UK into my letter box.
All parts present and correct.
Took an hour to build and worked first time.

It's yonks since I've built a QRP Labs kit.
Built U1's, U2's, U3's, GPS, a squillion LPF's in the past.

When I built U3S last week I'd actually forgotton just how easy they were, and how much I was getting
out of such a simple low cost bit of kit.

Me happy !


Re: FS: 40m and 20m QCX Mini

Anthony Luscre
 

I am interested in buying the pair.
What is g&s for 44224?

Anthony

On Thu, Mar 18, 2021 at 2:06 PM mike <w1mt.qrp@...> wrote:
I finished up two (a 40m and a 20m) QCX minis over last weekend. They are built, cased, aligned, calibrated and ready to go. Over 5 watts at 12.5v.
$120 per mini paypal g&s.

If you want both, save a little on shipping  $225 paypal g&s. I will wait 24 hours before splitting them up in case someone really wants a set.

Prefer USA shipping. Others inquire.
 
Please reply off list  w1mt(dot)qrp(at)gmail(dot)com
 
mike/w1mt



--
Anthony Luscre

K8ZT
Ohio Section Section Youth Coordinator & Education Outreach
ARRL - The National Association For Amateur Radio™
 
k8zt@... (best for Amateur Radio)

The Web Resource Hoarder- www.ZTLearn.com

K8ZT Radio Website- www.k8zt.com

Amateur Radio Resources for Students/Youth - www.k8zt.com/hry


Re: A simple QCX AGC #mods #qcx

Jim AJ8S
 

Gregg and Jack,

8 x 23 mm is small enough. In fact I measure 10 x 30 mm of space is available. See the attached photo.

I don't see where the potentiometer goes on Gregg's board but you need it to be someplace where it can be adjusted. Mine is accessible from the side over the top of the paddle jack so I can access it when the radio is fully assembled. But the display does not have to be installed for the receiver to run so the pot could lay flat on the board and be accessed from the top. This might be an advantage as vertical real estate is also quite limited. From the top of the TXCO to the underside of the display board is only a little more than 8 mm. If XTAL2 is installed then it is likely even less. Hans might actually have these measurements if he has a mechanical CAD model.

I wonder if making the board single-sided and a little larger might work better? That way it would not have as much vertical extent and the non-conductive underside could be in direct physical contact with components on the main board underneath. 

How to secure the new board in place is another question. There is a ground pin (marked "GND") next to C24 on the main board. There is also one at one corner of the TXCO (or on the main board at the same location if XTAL2 is installed). These points could be used to anchor the added PC board in place with vertical wires. At the transistor end this would mean adding another solder pad on the new board.

Just some thoughts... Hope it helps.

73, Jim AJ8S

.


FS: 40m and 20m QCX Mini

mike/w1mt
 

I finished up two (a 40m and a 20m) QCX minis over last weekend. They are built, cased, aligned, calibrated and ready to go. Over 5 watts at 12.5v.
$120 per mini paypal g&s.

If you want both, save a little on shipping  $225 paypal g&s. I will wait 24 hours before splitting them up in case someone really wants a set.

Prefer USA shipping. Others inquire.
 
Please reply off list  w1mt(dot)qrp(at)gmail(dot)com
 
mike/w1mt


Re: Battery Indicator Showing Zero Bars

ON7DQ Luc
 

Hi Phil,
No plans really, but there is a short description of how I made it in this thread on the SOTA Reflector
https://reflector.sota.org.uk/t/homebrew-mini-cw-paddles-and-video/15044
That is where I got the idea, after watching the great video by Ignacio, EA2BD, and reading the remark by John, G4YTJ.
Several other nice ideas there as well, enjoy reading.
I used that paddle during many SOTA activations, and also for the two QSO's in the QCX WARC Party last Monday.
Luc ON7DQ


Re: Does QCX Mini have DIY emission indication function? #qcxmini

John Pagett G4YTJ
 

Jakob,

Mine is a 40m QCX+. 
I think it works because of stray capacitance between the LED and ground.
The diodes are from the junk box. One is a 1N914, so similar to 1N4148. I think the other is 1N4148.

73
John
G4YTJ 

On 18 Mar 2021, at 15:56, jakob@... wrote:

Interesting! Are you sure the diodes are 1N4148? I will experiment with this circuit to find out how the led current is generated. Whatever it is, it is most likely a non-linear circuit and induces harmonics, as every non-linear component does in RF. But not a problem if applied before the LPF. BTW, what band is this QCX Mini?


Wowed by WSPR!

G3SPL
 

I decided to find out what this WSPR was all about mentioned in the QCX documentaition.  After a bit of Googling and reading Hans' excellent operating instructions I had my 30m QCX+ set up to go.
Now I should say that my antenna for 30m is the proverbial piece of wet string.  Quarter wave 2m high at one end and 4m high at the other and with a quarter wave counterpoise, fed by a feeder of twisted flex.  Needless to say, not particularly impressive!  So, I wasn't expecting much when I logged onto WSPRnet.org and checked the map.  Imagine my surprise when i found my 4W of RF had been heard all over Europe and as far as Iceland and right across the "Pond" in New York!  A few frames later I had 5 Stateside stations with the longest distance at 6900 km.  After my daily exercise walk and a spot of lunch, I fired up the WSPR again and this time was absolutely gobsmacked  (Northern English expression!) to see that I had been detected in Australia by VK7JJ at 17313 km.

My rubbish antenna normallly allows me to work around Europe on CW, but it just staggers me that 4W of RF can get to Australia using the extreme narrow band WSPR coding. Awesome!
(Picture attached showing the 3 Australian stations receiving my signals.)
--
Peter Lee
G3SPL


Re: QCX firmware

Jim Painter
 

Hey Ted, I upgraded my QCX and QCX+ using two different chips.xml files. I had trouble updating the QCX because the chips.xml file only had the 328P version and my QCX was 328. I found the older version of the chips.xml file somewhere but I can’t remember where. I think the files on groups.io are the newer version.

Thanks...Jim...KQ3S


On Mar 13, 2021, at 1:56 PM, Ted 2E0THH <qrp@...> wrote:

Brilliant Jim!
Any future updates are only 4 clicks from here on in.
Glad you got it sorted.

73s from a pretty chilly Cambridge, UK


Re: Does QCX Mini have DIY emission indication function? #qcxmini

jakob@...
 

Interesting! Are you sure the diodes are 1N4148? I will experiment with this circuit to find out how the led current is generated. Whatever it is, it is most likely a non-linear circuit and induces harmonics, as every non-linear component does in RF. But not a problem if applied before the LPF. BTW, what band is this QCX Mini?


Re: Does QCX Mini have DIY emission indication function? #qcxmini

John Pagett G4YTJ
 

Well I’ve just lashed up the LED indicator using a 3.3pF capacitor, two junk box signal diodes and a random LED.

The 3.3pF takes a feed from the hot side of my dummy load.

With the diode in free air the LED does not light, but if I place a finger next to it then a dim glow is seen. The LED I’m using is not particularly efficient; on diode test on my meter the glow is similar and I know that high efficiency LEDs will light up nicely on the diode test (1mA?).

So with a high efficiency LED mounted into a grounded metal case I’m quite certain that it will work.

An interesting diversion.

John
G4YTJ

On 17 Mar 2021, at 19:57, John Pagett via groups.io <john.pagett@...> wrote:

Alan,

You are right, that there can’t be a single ended indicator. But what the circuit diagram shows and what is reality can differ. Let’s assume there’s some capacitance to ground at the LED. To charge this capacitance, current would flow through one diode (with a smaller amount through the junction capacitance of the other diode). To discharge the stray capacitance, the current will then pass through the other diode, passing through the LED on the way.

I’m not saying that this is what happens, just that it’s a possible explanation.

Tomorrow afternoon happens to be a “do some electronics / radio” session over Zoom with a couple of friends. I’ll lash something up and see what results I get.

Pagett’s axiom - When reality and theory differ, reality takes precedence.

73
John Pagett
G4YTJ

On 17 Mar 2021, at 17:19, Alan G4ZFQ <alan4alan@...> wrote:



So chucking a "single ended" indicator to it is quite safe, it when you make it a "double ender" that it becomes a problem.
There can be no "single ended" indicator. If it indicates it is consuming power that has to be returned, just like an antenna.

I would think that any harmonics would be low but they could well be there.

73 Alan G4ZFQ










Re: Cost of shipping and customs ? ?

Bill M
 

Mine finally arrived via TNT/Fedex.  Took about a month total.  No fees.
TNT Tracking showed it in Jamaica and delivered in PR on the same day - haha.


Re: 10W PA and HackRF #pa

Eike Lantzsch
 

On Donnerstag, 18. März 2021 04:33:12 -03 Jim Allyn - N7JA wrote:
I wonder if perhaps your HackRF is bad. Specs say it should put out 5
dBm minimum, which would be 400 mV RMS. You say you are seeing
50mVss output from the HackRF. I'm not sure what Vss is, ordinarily
mVss is german for mV peak-to-peak

I would expect voltages to be given in Root Mean Square (RMS) or peak
to peak (p-p). Either way, it appears you aren't getting anything
approaching rated output from the HackRF. How are you measuring the
HackRF output level?

If the HackRF is meeting its output spec and the 10Watt PA is meeting
its gain spec, you should be seeing somewhere between a little over 1
Watt and a little over 10 Watts out of the PA. Clearly something is
horribly wrong here.


--
Eike Lantzsch ZP6CGE


Re: 10W PA and HackRF #pa

Jim Mcilroy
 

Vss is ground for many digital chips and FETs


On 18/03/2021 07:33, Jim Allyn - N7JA wrote:
I wonder if perhaps your HackRF is bad.  Specs say it should put out 5 dBm minimum, which would be 400 mV RMS.  You say you are seeing 50mVss output from the HackRF.  I'm not sure what Vss is, ordinarily I would expect voltages to be given in Root Mean Square (RMS) or peak to peak (p-p).  Either way, it appears you aren't getting anything approaching rated output from the HackRF.  How are you measuring the HackRF output level?

If the HackRF is meeting its output spec and the 10Watt PA is meeting its gain spec, you should be seeing somewhere between a little over 1 Watt and a little over 10 Watts out of the PA.  Clearly something is horribly wrong here.