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QCX+ 40 meter bandpass tuning


The Crunchbird
 

I just finished my QCX+ for 40 meters and before I break out the test equipment can someone tell me if the peak reading I am getting with the BPF is too low or not? there is a single peak and it looks to be in the right place on the trimmer capacitor. The best I can get it to peak to is about 5 on the scale. I have changed the frequency and I can tune to a new peak so it looks OK but maybe the Q of T1 was lowered when I put clear nail polish on it? The peak seems too low to me based on the example that the manual provides. It's a simple circuit and I have ample test equipment to fix it as well as a spare toroid core for T1 but I am wondering if the reading is too low or not. I would hate to start chasing a non existent problem if it is OK. Thanks in advance for anyones time, Dave. N2SN ex G4FEB. PS: The quality of the kit is nothing short of superb. Hans is both a genius electronic and mechanical engineer. 


Jim Painter
 

If it were me, I think I would check the performance before fiddling with anything.

Jim....KQ3S


On Sep 19, 2020, at 4:54 PM, The Crunchbird <pulsedevil@...> wrote:

I just finished my QCX+ for 40 meters and before I break out the test equipment can someone tell me if the peak reading I am getting with the BPF is too low or not? there is a single peak and it looks to be in the right place on the trimmer capacitor. The best I can get it to peak to is about 5 on the scale. I have changed the frequency and I can tune to a new peak so it looks OK but maybe the Q of T1 was lowered when I put clear nail polish on it? The peak seems too low to me based on the example that the manual provides. It's a simple circuit and I have ample test equipment to fix it as well as a spare toroid core for T1 but I am wondering if the reading is too low or not. I would hate to start chasing a non existent problem if it is OK. Thanks in advance for anyones time, Dave. N2SN ex G4FEB. PS: The quality of the kit is nothing short of superb. Hans is both a genius electronic and mechanical engineer. 


@CurtisM
 

The peak adjustment is less critical and the numeric value changes with volume setting.  if you get a peak,  things are likely good. I would not fret the Q of this network its pretty much given by the wire and the core. Its the nulls that are more significant. If this test goes well, and you like what you are receiving all should he well.

73 curt


The Crunchbird
 

Thanks Curt. Shirley was kind enough to help me. She pointed out that the volume control affects the reading. When I checked it my volume control did nothing. I had not checked anything else out as my poor old wife just went sick on me. I only fired the rig up once during a half hour that I had free before taking her to the doctors office. Shirley is a great person and my hat is off to her. 

I disconnected the BPF winding for T1 and measured its inductance. With it disconnected I measure the capacitance of the trimmer cap and it's parallel capacitor. When I calculated the combination the result was an fc of 7.104MHz so I know I am in the ballpark. 

The trimmer was at about eight oclock. I really should have taken a look at the schematic first but there it is. It is way more than likely that the volume control has come loose. The unusual pin bending causes the pins to barely reach the board. 

Thanks for your input and of course, thanks again to Shirley, Dave. N2SN ex G4FEB. 





On Sun, Sep 20, 2020 at 10:04 PM wb8yyy via groups.io <wb8yyy=yahoo.com@groups.io> wrote:
The peak adjustment is less critical and the numeric value changes with volume setting.  if you get a peak,  things are likely good. I would not fret the Q of this network its pretty much given by the wire and the core. Its the nulls that are more significant. If this test goes well, and you like what you are receiving all should he well.

73 curt


Hans Summers
 

Hi Dave, Shirley

The volume control does NOT affect the BPF Peaking reading. 

The volume control DOES affect the reading of I-Q balance, Low phase and High phase adjustments. 

73 Hans G0UPL
http://qrp-labs.com

On Mon, Sep 21, 2020 at 5:30 AM The Crunchbird <pulsedevil@...> wrote:
Thanks Curt. Shirley was kind enough to help me. She pointed out that the volume control affects the reading. When I checked it my volume control did nothing. I had not checked anything else out as my poor old wife just went sick on me. I only fired the rig up once during a half hour that I had free before taking her to the doctors office. Shirley is a great person and my hat is off to her. 

I disconnected the BPF winding for T1 and measured its inductance. With it disconnected I measure the capacitance of the trimmer cap and it's parallel capacitor. When I calculated the combination the result was an fc of 7.104MHz so I know I am in the ballpark. 

The trimmer was at about eight oclock. I really should have taken a look at the schematic first but there it is. It is way more than likely that the volume control has come loose. The unusual pin bending causes the pins to barely reach the board. 

Thanks for your input and of course, thanks again to Shirley, Dave. N2SN ex G4FEB. 





On Sun, Sep 20, 2020 at 10:04 PM wb8yyy via groups.io <wb8yyy=yahoo.com@groups.io> wrote:
The peak adjustment is less critical and the numeric value changes with volume setting.  if you get a peak,  things are likely good. I would not fret the Q of this network its pretty much given by the wire and the core. Its the nulls that are more significant. If this test goes well, and you like what you are receiving all should he well.

73 curt


Shirley Dulcey KE1L
 

Yes. That was my error in a private message that I later corrected. Hans, of course, is correct.


On Mon, Sep 21, 2020 at 2:16 AM Hans Summers <hans.summers@...> wrote:
Hi Dave, Shirley

The volume control does NOT affect the BPF Peaking reading. 

The volume control DOES affect the reading of I-Q balance, Low phase and High phase adjustments. 

73 Hans G0UPL
http://qrp-labs.com

On Mon, Sep 21, 2020 at 5:30 AM The Crunchbird <pulsedevil@...> wrote:
Thanks Curt. Shirley was kind enough to help me. She pointed out that the volume control affects the reading. When I checked it my volume control did nothing. I had not checked anything else out as my poor old wife just went sick on me. I only fired the rig up once during a half hour that I had free before taking her to the doctors office. Shirley is a great person and my hat is off to her. 

I disconnected the BPF winding for T1 and measured its inductance. With it disconnected I measure the capacitance of the trimmer cap and it's parallel capacitor. When I calculated the combination the result was an fc of 7.104MHz so I know I am in the ballpark. 

The trimmer was at about eight oclock. I really should have taken a look at the schematic first but there it is. It is way more than likely that the volume control has come loose. The unusual pin bending causes the pins to barely reach the board. 

Thanks for your input and of course, thanks again to Shirley, Dave. N2SN ex G4FEB. 





On Sun, Sep 20, 2020 at 10:04 PM wb8yyy via groups.io <wb8yyy=yahoo.com@groups.io> wrote:
The peak adjustment is less critical and the numeric value changes with volume setting.  if you get a peak,  things are likely good. I would not fret the Q of this network its pretty much given by the wire and the core. Its the nulls that are more significant. If this test goes well, and you like what you are receiving all should he well.

73 curt