Does QCX Mini have DIY emission indication function? #qcxmini


BI8CZM
 

QCX Mini is great!  But in the process of use, the only drawback is that there is no launch indication. Do you have a way to add an emission indicator in QCX Mini DIY, or trouble Hans to modify the source program, add the emission indicator function in LCD, or any other good method. Please give some suggestions, thank you.
--
Jun


KN6HGG
 

Make yourself an LED indicator for the PTT jack. Remember to never plug/unplug anything on the jack while the radio is on!


BI8CZM
 

How to connect? Do you want to remove the PTT socket? thank you
--
BI8CZM


KN6HGG
 

https://www.etsy.com/listing/685833368/35mm-eurorack-led-modular-light-plugs

Something like this, but with the correct stereo (TRS) plug~


BI8CZM
 

thank you,73
--
BI8CZM


Mehmet Dinch
 

Hi Jun,

Take a look around Q7, audio mute on TX. I wonder if D5 could be replaced with an LED? Or put an LED in parallel maybe?

Regards,

Mel. M0KMD.


Mehmet Dinch
 

No that wont work. It would need to be an LED in series with, say, a 10K resistor from gate of Q7 to ground. However, this might have an adverse effect on the the audio mute control...

Mel. M0KMD


Mehmet Dinch
 

Yeah, don't do that mod. I just tried it.
1. the LED is dim. Would need reduce the resistor value to say 5k.. not sure..
2. it causes a horrible click in the in the audio on key release.

Mel. M0KMD,


Mehmet Dinch
 

I just tried that on the PTT line, 10K in series with an LED between PTT and ground. It's a lot cleaner, though the LED is still dim, just as an experiment.

However, in my humble opinion, a blinking LED is not affirming your TX anymore than the side tone that you hear on key down.
Equally, you could set TX decode on...

Regards,

Mel. M0KMD.


David
 

Transmission Indicator. (Thanks to Andy/G0FTD for his original information)
Here is the easiest circuit possible and works perfectly. It would mean having to drill a small hole in the case for a LED though.
see message #35449 or go to site https://sites.google.com/site/andyg0ftd/led-o-meter.
On my QCX20 I have the LED power indicator  connected via a 1pF cap to the centre pin of the BNC socket. No other connections. At 4 watts it lights brightly. If I reduce the supply  voltage to about 10 volts the power is about 2 watts.  The LED still lights.   I used a couple of germanium diodes but IN4148 work as well. 
You may be able to avoid having to connect the circuit to the QCX, it's possible that with a length of insulated wire wound around and near to the aerial socket that the pickup will be enough to light the LED. Try experimenting.
The advantage of this circuit is that when the LED lights it is an indication that you are actually transmitting RF.
73 Dave M3PMG


Alan G4ZFQ
 

On my QCX20 I have the LED power indicator  connected via a 1pF cap to the centre pin of the BNC socket.
Dave,

Has this been checked for harmonic generation?
I think diodes connected to RF should be avoided?

73 Alan G4ZFQ


Stephen Sherer
 

I have also been wrestling with WHERE to put the LED. Considering removing one of the front panel screws and installing the LED in the screw hole. 

David, your idea seems the best so far. For those of us with less knowledge, I would need a schematic as my knowledge is low in this arena.

Stephen 
--
KE4LJH
Steve, 
Florida


John Pagett G4YTJ
 

Good point, Alan.

A few weeks ago I posted harmonic plots from my QRP-Labs 50W amplifier. The dummy load I used (100W) had a -40dB tap for the spectrum analyser and also a power measuring circuit exactly the same as Hans uses in the dummy load kit. With the diode connected in the power measuring circuit the higher harmonics didn’t tail off in the expected way.

But...

Using the same configuration with a barefoot QCX the harmonics were essentially the same with or without the diode connected. Given the very small coupling capacitor used in this case I doubt if the harmonics would be increased, although personally I’d check anyway.

John
G4YTJ

On 17 Mar 2021, at 10:51, Alan G4ZFQ <alan4alan@...> wrote:



On my QCX20 I have the LED power indicator connected via a 1pF cap to the centre pin of the BNC socket.
Dave,

Has this been checked for harmonic generation?
I think diodes connected to RF should be avoided?

73 Alan G4ZFQ





David
 

Hi Alan, I would assume that the fact it is coupled to the QCX with a 1pF cap that it would not produce  harmonics that could be radiated. Also as I said the LED does not necessarily need to be connected,  even with a short length of wire the pickup may be enough to light the LED if placed in the vicinity of the aerial connector. Another way may be to connect the LED prior to the LPF so that any possible harmonics would be filtered out.
There are, of course, far greater experts who contribute to this group who may be able to offer advice.
73 Dave M3PMG


geoff M0ORE
 

And the effort used to generate the RF signal is wasted just to produce a few Lumens! ( or is it candlepower or candela )

At 14MHz, a 1pF capacitor has a reactance of about 11k Ohms so not a very high resistance.

On 17/03/2021 11:22, David wrote:
Hi Alan, I would assume that the fact it is coupled to the QCX with a 1pF cap that it would not produce  harmonics that could be radiated. Also as I said the LED does not necessarily need to be connected,  even with a short length of wire the pickup may be enough to light the LED if placed in the vicinity of the aerial connector. Another way may be to connect the LED prior to the LPF so that any possible harmonics would be filtered out.
There are, of course, far greater experts who contribute to this group who may be able to offer advice.
73 Dave M3PMG


Albert Tatlock's Greatest Hits - Vol 1
 

On Wed, Mar 17, 2021 at 03:35 AM, David wrote:
Here is the easiest circuit possible and works perfectly. It would mean having to drill a small hole in the case for a LED though see message #35449 or go to site https://sites.google.com/site/andyg0ftd/led-o-meter.

It's been moved to here - https://sites.google.com/view/andy-g0ftd/led-o-meter


jakob@...
 

Is that a prank or can you explain this circuit's method of operation?


Albert Tatlock's Greatest Hits - Vol 1
 

Diodes and harmonics.

HInt, solder one end of a diode to the output and observe the effects.

What, you mean there aren't any ? ;-)

Now solder the other end across the output (like some QCX user tried to).

Oh look, harmonics.

So chucking a "single ended" indicator to it is quite safe, it when you make it a "double ender" that it becomes a problem.

Incidentally the "diode double ender" can be made into a useful trick for old signal generators that lack VHF / UHF
coverage.

I keep a diode strapped across a connector, that in turn can be attached or un-attached to a t-piece on the output
of a 0 - 150Mhz sig genny in order to extend it's range up to UHF.


David
 

Is that a prank.  Ha Ha, well it isn't  April 1st yet.  No it isn't a prank and no I can't explain how it works.  It seems too simple.
Anyway I have moved the "circuit" from the BNC to the junction of C27, C29 and L3.  That way if there are any harmonics generated,  hopefully,  they will be attenuated when they pass through the LPF.  The photo shows my 20M QCX which is fitted to a copper clad paxolin board which is useful for carrying out experiments such as AGC etc. The QCX was putting out about 3.5 watts into a dummy load. The LED was brighter than it looks but didn't show up too well.   The original idea behind this circuit was to use it to test for the presence of rf and the components could be mounted inside a biro pen. Again, thanks to Andy/G0FTD for his idea in using it as a piece of test equipment. 73 Dave M3PMG






Alan G4ZFQ
 

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