Date   

Re: 5W Tube Amp for QCX?

Steve Greffe - VE3SGV
 

And a couple of slipups on my part. The 5F2A is tweed era,  not blackface. And really,  it's a single ended Princeton, not a Champ. Still the best single ended class A circuit you'll find though. Still digressing here hi hi.

I've built about a dozen of 'em and I've only managed to hang onto one.

But this is ham radio. Build the Ameco AC1, you won't be disappointed.

73
Steve VE3SGV 


Re: No power output

Daniel Krompholz <dgkrompholz@...>
 

Thank you all!!!


On Fri, Jul 23, 2021, 6:12 PM Ronald Taylor <wa7gil@...> wrote:
Daniel, you don't need any solder in those 4 holes that are together on one edge of the board. Those are for some pins you did not install. The other ones look like some of the toroid leads. Some of them do look like they didn't get hot enough to melt the enamel coating off the wire. Put a hot iron right on the tip of the wire and add some solder and wait till it flows down the wire to the solder pad. Hope that helps ..

Ron

On Fri, Jul 23, 2021 at 3:04 PM Daniel Krompholz <dgkrompholz@...> wrote:
Sorry, do I understand you correctly if you mean apply solder in each of these spots?

On Fri, Jul 23, 2021, 5:58 PM N3MNT <bob@...> wrote:
Solder touch in the yellow areas.


Re: No power output

Ronald Taylor
 

Daniel, you don't need any solder in those 4 holes that are together on one edge of the board. Those are for some pins you did not install. The other ones look like some of the toroid leads. Some of them do look like they didn't get hot enough to melt the enamel coating off the wire. Put a hot iron right on the tip of the wire and add some solder and wait till it flows down the wire to the solder pad. Hope that helps ..

Ron

On Fri, Jul 23, 2021 at 3:04 PM Daniel Krompholz <dgkrompholz@...> wrote:
Sorry, do I understand you correctly if you mean apply solder in each of these spots?

On Fri, Jul 23, 2021, 5:58 PM N3MNT <bob@...> wrote:
Solder touch in the yellow areas.


Re: No power output

Daniel Krompholz <dgkrompholz@...>
 

Sorry, do I understand you correctly if you mean apply solder in each of these spots?


On Fri, Jul 23, 2021, 5:58 PM N3MNT <bob@...> wrote:
Solder touch in the yellow areas.


Re: No power output

N3MNT
 

Solder touch in the yellow areas.


Re: No power output

Daniel Krompholz <dgkrompholz@...>
 

1. Yes, maybe the meter is not appropriate.
2. Can you elaborate on what to look for in the circled yellow spots?

Thank you!!!


On Fri, Jul 23, 2021, 4:56 PM Karl Schwab <schwab.karl@...> wrote:
I have a MFJ -894 that is both, 1.6-525 MHz, 2/20/200 W. Works well, not a laboratory instrument. 

On Fri, Jul 23, 2021, 4:50 PM N3MNT <bob@...> wrote:
Watt meter appears to be  VHF meter not HF.


Re: No power output

Karl Schwab
 

I have a MFJ -894 that is both, 1.6-525 MHz, 2/20/200 W. Works well, not a laboratory instrument. 


On Fri, Jul 23, 2021, 4:50 PM N3MNT <bob@...> wrote:
Watt meter appears to be  VHF meter not HF.


Re: No power output

N3MNT
 

Watt meter appears to be  VHF meter not HF.


Re: No power output

N3MNT
 

A few spots to check  ( Circled in Yellow.)


Re: No power output

Daniel Krompholz <dgkrompholz@...>
 

Also, I meant to add the following:

I have already
4. Ensured the test watt meter and dummy load works with another radio 
5. Successfully received and decoded cw signals when connected to an antenna

On Fri, Jul 23, 2021, 4:37 PM Daniel Krompholz <dgkrompholz@...> wrote:
I cannot get qcx-mini to output any power. 

I have already:
1. Gone through the alignment process
2. Applied extra heat with the soldering iron to the toroid winding wire at the soldering points
3. Adjusted the windings with various configurations

Please advise!

Thank you


No power output

Daniel Krompholz <dgkrompholz@...>
 

I cannot get qcx-mini to output any power. 

I have already:
1. Gone through the alignment process
2. Applied extra heat with the soldering iron to the toroid winding wire at the soldering points
3. Adjusted the windings with various configurations

Please advise!

Thank you


Re: Receiver front-end filter #rcvr

cris blak
 

Nice idea Glen.
I think the variable capacitor is half the size of the QCX HI! but it will do.

Thank for sharing.

73 de YO3FFF
Cristi

Pe vineri, 23 iulie 2021, 21:27:23 EEST, Glen Leinweber <leinwebe@...> a scris:


Completed QRP-Labs receiver module, meant for most any band.
Hans supplies a fixed-tuned bandpass filter module between antenna & input for some RF selectivity.
Modules for most any HF band are available from QRP-Labs.
Why not attempt a similar module with a big dual-gang variable capacitor that tunes over all HF?
Hans conveniently does allow direct inputs right on the PCB from such a filter.

The circuit arrangement is exactly the same as Hans' filter: two toroids (tuned by each gang
of the big variable), coupled together by a fixed, small coupling capacitor. A link winding couples
antenna signals into one toroid, while the other toroid couples another similar link winding for output.

I used T50-2 toroid cores, with a 5-turn link winding on each....30 turn main winding #24 AWG.
Those dual-gang variable capacitors are rare today. You want one from an AM radio with equal
capacitance, of the 365 pf variety. I pulled one from an old transistor desktop AM/FM radio. The
20pf capacitance sections normally used for FM are left unused.
The fixed 6.8 pf coupling capacitor (hidden in the photo) couples signals from one gang to the other.

How wide a tuning range can such a filter accommodate? Those two toroids must be matched
carefully, especially at the high-frequency end. That 6.8pf coupling capacitor is a bit small at the
low frequency end (3.8 MHz) where capacitor plates are fully meshed. Attenuation is 6.5dB there,
but it is a very effective filter.
Filter losses were quite small at higher frequency, but filter bandwidth grew to be quite wide.
Frequencies from 3.5 - 23MHz were accommodated.
With a Si5351 VFO module, this makes a pretty nice general-coverage receiver.


Receiver front-end filter #rcvr

Glen Leinweber
 

Completed QRP-Labs receiver module, meant for most any band.
Hans supplies a fixed-tuned bandpass filter module between antenna & input for some RF selectivity.
Modules for most any HF band are available from QRP-Labs.
Why not attempt a similar module with a big dual-gang variable capacitor that tunes over all HF?
Hans conveniently does allow direct inputs right on the PCB from such a filter.

The circuit arrangement is exactly the same as Hans' filter: two toroids (tuned by each gang
of the big variable), coupled together by a fixed, small coupling capacitor. A link winding couples
antenna signals into one toroid, while the other toroid couples another similar link winding for output.

I used T50-2 toroid cores, with a 5-turn link winding on each....30 turn main winding #24 AWG.
Those dual-gang variable capacitors are rare today. You want one from an AM radio with equal
capacitance, of the 365 pf variety. I pulled one from an old transistor desktop AM/FM radio. The
20pf capacitance sections normally used for FM are left unused.
The fixed 6.8 pf coupling capacitor (hidden in the photo) couples signals from one gang to the other.

How wide a tuning range can such a filter accommodate? Those two toroids must be matched
carefully, especially at the high-frequency end. That 6.8pf coupling capacitor is a bit small at the
low frequency end (3.8 MHz) where capacitor plates are fully meshed. Attenuation is 6.5dB there,
but it is a very effective filter.
Filter losses were quite small at higher frequency, but filter bandwidth grew to be quite wide.
Frequencies from 3.5 - 23MHz were accommodated.
With a Si5351 VFO module, this makes a pretty nice general-coverage receiver.


Re: 5W Tube Amp for QCX?

VE3VXO
 

The champ will give you awesome tone though... the most recorded amp in history....rock on ;)


Re: QLGL2 - micro USB connection

Dan Reynolds
 

Thanks Dean. I've found some one Digi-Key that should work. Unfortunately I have to replace my display... I fat fingered it - so to speak. 
--
Dan Reynolds -- KB9JLO
<><


Re: New QCX Mini 17M completed - expected rx sensitivity (minimum detectable signal level)?

Jim Sheldon
 

Dave,
I'd be very careful replacing that diode with the inductor - the diode is there to prevent accidental polarity reverse power input from destroying the MINI. I'd seriously consider getting a power supply that was either an analog supply or guaranteed RF noise free from the manufacturer. Much safer and well worth the investment in the long run.

Jim, w0EB

------ Original Message ------
From: "David Feldman via groups.io" <wb0gaz=yahoo.com@groups.io>
To: QRPLabs@groups.io
Sent: 7/23/2021 9:54:27 AM
Subject: Re: [QRPLabs] New QCX Mini 17M completed - expected rx sensitivity (minimum detectable signal level)?

Thanks ---- I've been able verify 17M noise floor elevates when antenna attached, so at this point I'm going to declare victory on this issue for time being. TX power seems to be consistent with expectation. Brief foray onto 20 meters was successful as well.

One other question/concern - the radio is very (very) sensitive to electrical noise arriving on the DC power jack; has anyone discussed replacing (or supplementing, if enough space in which to work) the input diode with an inductor and a couple of shunt capacitors to reduce noise pick-up arriving via DC power source?

Thanks for any thoughts on this,

Dave


Re: New QCX Mini 17M completed - expected rx sensitivity (minimum detectable signal level)?

David Feldman
 

Thanks ---- I've been able verify 17M noise floor elevates when antenna attached, so at this point I'm going to declare victory on this issue for time being. TX power seems to be consistent with expectation. Brief foray onto 20 meters was successful as well.

One other question/concern - the radio is very (very) sensitive to electrical noise arriving on the DC power jack; has anyone discussed replacing (or supplementing, if enough space in which to work) the input diode with an inductor and a couple of shunt capacitors to reduce noise pick-up arriving via DC power source?

Thanks for any thoughts on this,

Dave


Re: New QCX Mini 17M completed - expected rx sensitivity (minimum detectable signal level)?

ajparent1/KB1GMX
 

For many decades the acid test for RX senstivity was:

Audio output with 50 ohm load.
With not other changes audio output when connected
to a dipole or other known working antenna.

Experience is if the second case has a noticeable increase
in noise to the ear the sensitivity has proven more than
adequate for the band.

Allison
-------------------------------
Please reply on list so we can share.
No private email, it goes to a bit bucket due to address harvesting


Re: Out of band on my QCX Mini 20

 

Please let us know how you go on 30m and what antenna you use in the park, sounds like great fun

On 22 Jul 2021, at 22:50, K9NUD-Steve <k9nud@...> wrote:

I'm planning to activate a park or two tomorrow. I'll give it a go on 30M, trusting the LPF will keep me from violating the rules. Thanks everyone, I now have a better understanding of the science. The fun never stops...


--
Love 30m and CW?
http://www.30cw.net


Re: QLGL2 - micro USB connection

Dean Smith
 

If I Had to choose bottom left or middle far right!
They seem to have better solder tags.

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