I'm curious if folks have identified a cure for this.

I'm running my QLG1 through a fairly long cable (QLG is upstairs in the kitchen) to my VFO/SigGen (it's in the
basement).? I am, like other posters here, hearing that pulse across a broad spectrum (don't have a precise
definition of that).

I tried wrapping the cable in ferrite cores, but that didn't help.

What I found was that if I disconnected the serial data line, the problem went away.? So, I can accurately
calibrate the VFO/SigGen, and I can show the 1pps heartbeat, but I can't show any of the data (date/time,
for example) that comes in the serial data stream.

Any hints would be appreciated.

- Bruce K1FFX

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Hi, Jarda

Here is a little circuit I added to my QCX. Not shown on the schematic is a 2.2k ohm resistor that I added between the middle leg of the volume control and the board. The 2N7000 transistor is installed between the ground end of the volume control and the board connection where the volume control middle connection goes.

To set it up, connect an antenna to the radio and set the volume to max, tuned to a clear channel (no signal). Starting with the 1K control set to the ground end, slowly rotate the control clockwise until you hear the band noise drop slightly. Back up slightly so the noise is not reduced.

Using the component values listed there is no "pumping", no loud blast and then reduce. It sounds like a "big radio", with signals against a quiet background, and background noise coming up when the signal fades to a bar or two on the signal indicator.

Jim W4JED

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Mr. Abeza

Menu item 8.5 sets the synthesizer reference frequency. Tweak the number a couple hundred hertz, SAVE and exit the menu. Try listening again. If the receive frequency has changed in the correct direction but not enough, tweak again in the same direction, judging how much to change it by the previous change. Etc. You should be able to get it within a few hertz of exact.

Jim W4JED

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??? ??? Dr OM Jarda ,

Indeed, Digital AGC will solve you problem .

This is a project based on a digital POT and a PIC12F683 Pic ?P .

Pass me your E-mail address and I will send you the full doc .

Note this project is open for hardware and software .

WD9HNU reproduced this 3weeks ago with success . Maybe you can ask him for a duplicate of the PCB , however this is also proposed in the doc , basedd on Kicad .

It's your choice .

in attachement the response curves of this project .

on5kn@...

73 Willy ON5KN

Hi Kurt. Looks like you got the first issue solved. I had a similar issue as you are now seeing with one of mine. PLEASE connect a dummy load before turning it on again ... and then check to see if it's transmitting. Listen for it on a receiver or look with your scope, or feel if the 3 power transistors are getting hot. It could be stuck in transmit mode and you are hearing the side tone. That's what happened to me. The issue on mine turned out to be a bad microswitch (the built in key) which was causing it. If it is stuck in transmit you need to trace out the keying circuit and see what's causing that. Good luck

73,

Ron WA7GIL

I have built and tested the digital AGC designed by Willy, described at this link.
Works quite well.
72 Fred WD9HNU

Thanks Alan,? I resolved my LCD display problem per your valuable assistance.
I went to the web site you indicated, and learned how to fixed my problem by changing
the 8.5 Ref Freq from 27,004,000 to 27,006,000. You made my day.
August WA2HTF

Generally there are three ways...

*Audio compressor in the audio stream.? The problem here is while the audio is?
kept from getting too loud if the station is strong the audio system will overload
and the use hears distortion.? There is a limit to dynamic rage of such a system.
Getting the levels and time constants correct for best possible dynamic range
is tedious.

*Use the audio to control a diode or fet based variable attenuator at the RX input.
This is before the receiver and both protects from overload and distortion
as well as keep loud signals from causing ear pain.? Biggest thing is connecting
to the receiver after the TR switching and before the receiver input.? Second is
getting the agc time constants correct.?

Manual switched RF attenuator (or variable) to lower the RF in for strong signals.
Its manual, just like volume control.

All work and both have the specific issues to implement.

I've implemented the RF AGC in a similar receiver using diodes with good result.
The system samples audio from the volume control rectifies it to DC that varies
with audio level and after amplification applies that to the electronic attenuator
(in my case using diodes).? ?Obviously I had to design it.? ?However it was easier
to do as I controlled the board layout and allowed room.? ?

The insertion point for such a circuit would be between Q5 and T1.

Allison

I wonder if anyone has an idea how to implement the AGC into QCX.....Tnx for hints !

Jarda

/g/QRPLabs/message/26070?p=,,,20,0,0,0::Created,,agc,20,2,0,24613271

73 Alan G4ZFQ

You're using the wrong ohmmeter. The black foam that semiconductors are packaged with can be used to make strain gauges. As you compress, twist, or stretch the foam the resistance changes.

Jim,
Or, maybe I had a piece of fake foam:-)
It certainly does work as you say.

73 Alan G4ZFQ

receiver to a specific frequency, the LCD display is indicating 500 hz lower then it should be.
As an example, W1AW is display as 07.0470 instead of 07.0475, this occurs on all selected frequencies.

The calibration is mentioned in the manual. Menu 8.5
And answered recently read /g/QRPLabs/message/26706 but look at the following post, I got it a little wrong.
Also you could see all of that topic.

73 Alan G4ZFQ

Assembled the QCX 40M kits, performed all the alignments, receiver
and transmitter functions properly. Transmitter output with 12.3 VDC applied,
indicates 2.65 Watts. The only problem I am experiencing, is when I adjust the
receiver to a specific frequency, the LCD display is indicating 500 hz lower then it should be.
As an example, W1AW is display as 07.0470 instead of 07.0475, this occurs on all selected frequencies.
Any help to resolved this problem will be greatly appreciated.

Hi Gents,
I wonder if anyone has an idea how to implement the AGC into QCX.....Tnx for hints !
Jarda OK1MKX

If it's still howling

Was there something said about the wrong earpiece impedance causing oscillation?

73 Alan G4ZFQ

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Hi, Kurt

Before panicking (don't forget your towel), I would try a factory reset, just in case some signal thingy is left turned on. If it's still howling at you, then divide and conquer. See if it varies with the volume control, etc.

Jim W4JED

Hi, Alan

You're using the wrong ohmmeter. The black foam that semiconductors are packaged with can be used to make strain gauges. As you compress, twist, or stretch the foam the resistance changes.

Jim W4JED

Greetings all me again;
? So by the time I get my QCX/30 on the air I think I will be totally bald from pulling my hair out.

The low audio issue was discovered and resolved. If I would of realized the swap of R21 and R35 I would not have replace IC9 (which was a pain).?

After triple checking all the traces and component values I applied power only to discover yet a new problem. Somehow the audio stage is now in a self oscillating state emitting a tone.?

So a new day a new challenge.

Any suggestions?

73;
Kurt -W2MW?

Happily I can annouce: complete success!

Andre,

And may you have lots of fun!
I wonder what sort of foam? Even the black anti-static does not normally seem to conduct.

73 Alan G4ZFQ

The antenna on the GPS module is so nice I would not rule out its use. I mounted the entire gps is a deluxe plastic kitchen container. The lid is a fine radome, the clear body presents the flashing LEDs nicely. No issues at all using it next to a lower level window, and its nicely portable. If you must go with an external antenna I suggest this same patch antenna design.

Curt