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Re: Alignment Troubles #qcx #20m #alignment #bpf

connor.mike7986@...
 

Just re-checked across C1, 0ohms. 
Added a 104 cap where C5 goes, and the BPF moved to an "8" and stayed there. Did not change at all in reaction to trimmer setting with the extra cap in place.
Remelted the solder on the volume pot and double checked connections, so it is fully connected now if it was not before(I didn't check this one prior). Afterwards was able to at least to set the 3 nulls to their minimums.
I will need to wait till the band gets more traffic in the morning to see if I can receive anything.

Connor, W7AOE


Re: 80 meter bpf toroid winding 30 turns givel 4.3 micro Henrys, not 3.8

KI7MWA
 



Here's my setup.  The two cal standards lying over are the open and through.  If you're familiar with QRP Labs products you will recognize the band pass filter, with the toroids unmounted.  This is an 80 meter kit, 30 turns of #28 wire on a T37 doesn't leave much room for bunching or squeezing.


Re: 5 Volt Supply

Jim Broyles
 

Geoff,

 

Good point about the mounting tab not being at ground potential on the LM317T and LM338T.

It is at output voltage potential in both, and must be isolated from your heatsink if grounded..

Those regulators (7805, 7809, 7812, etc.) with the mounting tab at ground potential

Have all lulled us into bad heatsinking practices.

 

73, Jim K9GCS

 

 

 

 


Re: getting high voltages #problem #building

KN6HGG
 

Surely you had a dummy load attached before connecting the GPS?? Also, if you just plug it in without being in the right mode, it will start keying your transmitter.


Re: 80 meter bpf toroid winding 30 turns givel 4.3 micro Henrys, not 3.8

Bob Benedict, KD8CGH
 

I second Kees advise on tuning by turn spacing.

I have also had to remove turns from LPF torroids. I put a small modeling study in the files section
https://groups.io/g/QRPLabs/files/LP.pdf
that you can use to compare your sweep to.

One issue with a VNA is calibration. You should calibrate at the point of device test. I built a LPF test holder along with plug in calibration devices for open, short, 50 ohm load and through. Here is a post on it
https://groups.io/g/QRPLabs/message/49978
and a nice commercial version here
https://groups.io/g/QRPLabs/message/49980

Finally here are two posts I found helpful from Allison
https://groups.io/g/QRPLabs/message/51788
https://groups.io/g/QRPLabs/message/49853

--
  73
    KD8CGH


Receiver module

Chris Waldrup
 

Hi,
I am wanting to get the receiver module tested tonight or tomorrow. 

I understand the LO has to be 4 times the frequency so for my 40 meter filter installed now I will need a 28 Mhz VFO. 

What is the amplitude that I need to drive the module? Is it a normal 7 dBm? I am going to test it with my HP8640 generator but might switch to a Si5351 for the finished product.  

Thank you. 


Chris
KD4PBJ


Re: 80 meter bpf toroid winding 30 turns givel 4.3 micro Henrys, not 3.8

Kees T
 

Try spreading the turns and/or bunching them together and see what the variation is. It may surprise you.

73 Kees K5BCQ 


Re: getting high voltages #problem #building

will.koenig.rn@...
 

I found the problem, I think.  I had left out R19 and R54.  After that it seemed to work correctly. 
Then I plugged in my GPS.  And smoke. First I think I saw brief smoke from Q6, then from the area of pin 10 of IC3.  I have used the GPS on 3 other QCX units, so the GPS itself is fine. Maybe I crossed a wire or something on connection? The smoke was pretty immediate as I inserted the leads into the JP1 pads.  I'm guessing I should just get a new Q6 and IC3 and try again?  Any suggestions on ordering such parts--if I type in 74ACT00N in Mouser, there are 4 options? And 3 options for MPS751.
Thanks,
Will


Re: 80 meter bpf toroid winding 30 turns givel 4.3 micro Henrys, not 3.8

KI7MWA
 

So, I wound it again and got the design value (3.83 uH).  The problem, really, is that, tuning with the nanovna, I have to reduce the turns to 28 (I've done this 3 times now), and when I trim the extra wire and check it again, I've passed the tuning point (trimmer cap is no longer about half way open).  I am aiming for a center frequency of 3.75 MHz (too high?).  Best insertion loss I've achieved is around -3.5 dB.


80 meter bpf toroid winding 30 turns givel 4.3 micro Henrys, not 3.8

KI7MWA
 

Been assembling an 80 meter band pass filter, and have consistently had to remove 6 turns during the tuning phase (using a nanovna).  This most recent attempt, I used my Peak LCR45 to measure the initial inductance, before installing the toroid.  With the recommended 34 turns (4 more than the design "design" number, 30), I get 5+ uH.  Pulling the extra 4 turns gives me 4.3 uH.  The design value is 3.8 uH.

Anyone with similar experience?  Or am I doing something wrong here?


Re: QCX+ T1 Toroid Wire Length? #20m #qcx+ #20m #toroid

@CurtisM
 

Walt

I respect this toroid is a huge hurdle, but success is sweet.  These windings make this receiver bring signals cleanly into your ears.  if it makes you feel slightly better, I did mine twice from my 80m QCX+. 

There is no right or best technique, but the electric and magnetic fields require all those windings to go the same direction.  So think in you mind they are continuous, just broken into sections.  Now as for how to do it - find what works for you.  Vital that you can clearly see the windings to get them to the proper spot - the nice picture in the QCX+ manual helped me to figure this out, and those lines on the board identify the mounting holes for the separate windings - and the two holes without the line service the single long winding. 

Yes its recommended to do this winding first.  If it helps, wind the other toroids first and set them aside - then go for it,  This transformer with its 4 different windings is a key element of why this receiver sounds so wonderful. 

Sit back and enjoy the build.  if you already have a rig, be patient in working this one.  as needed, the gang here can even inspect your work if you supply a clean picture - but I suspect when you work matches Hans picture you should be just fine. 

73 curt wb8yyy


Re: Clock/TMP36 Connect

Bob ZL1RS
 

Yes x 3.


Re: #u3s QCXPTXCO install #u3s

Jim Mcilroy
 

Hi

C2 is removed so the TCXO can be a close fit onto the board basically.


On 06/09/2020 18:32, KEN G4APB via groups.io wrote:

Hi Hans,

on the QCX+, you say to remove C2 before fitting this tcxo module but it appears to be just supply decoupling. Does any similar capacitor need to be removed when modifying the Si5351A module?

73 Ken G4APB


Re: QCX+ T1 Toroid Wire Length? #20m #qcx+ #20m #toroid

Jim Painter
 

I think the purpose of winding t1 from a single continuous piece of wire is to make sure all 4 winding are wound in the same direction. That insures the proper phase relationship of all 4 windings.

Jim....kq3s

On Sep 6, 2020, at 12:38 PM, tron eee <troneeee@gmail.com> wrote:

Hi,

Hah! So I received the QCX+ package, fast ship, really nice kit.

I read the instructions on how to wind the T1 toroid RF input transformer. I also used a 'shuttle' idea that I learned on utoobski, which works rather nicely To make toroid wire-shuttle, I cut a wood chopstick about 2 1/2 Inches (6,35cm) long, carved a deep V-notch on each end and wound the magnet wire end-to-end on the chopstick into the V-notches. Works good.

Heh heh, the toroid looks really good. It was my very first toroid, but I wound the toroid backwards and the wires don't align properly with the PCB holes! Damn! And as I already cut the loops, I can't unwrap it to rewind it properly.

Once again hah! I found in my goodie box a 1Lb spool of #28 PE enamel wire!

So, anybody know the length of the wire for winding QCX+ T1? I guess I could unwrap it and measure the length?

Thanks in advance (as Hans says...don't be a hero!),

walt - KM6OYH



Re: QCX+ T1 Toroid Wire Length? #20m #qcx+ #20m #toroid

Gary Bernard
 

That's helpful to all. Hans should incorporate lengths of each toroid in Inches and MM.


-----Original Message-----
From: tron eee <troneeee@...>
To: QRPLabs@groups.io
Sent: Sun, Sep 6, 2020 12:08 pm
Subject: Re: [QRPLabs] QCX+ T1 Toroid Wire Length? #20m #qcx+ #toroid

All,

Ok...I stopped being lazy and I measured the #28 ga enamel magnet wire peices...34 inches/86,36cm long, fyi.

KM6OYH



Re: QCX+ T1 Toroid Wire Length? #20m #qcx+ #20m #toroid

tron eee
 

For 20m...


Re: QCX+ T1 Toroid Wire Length? #20m #qcx+ #20m #toroid

tron eee
 

All,

Ok...I stopped being lazy and I measured the #28 ga enamel magnet wire peices...34 inches/86,36cm long, fyi.

KM6OYH


Re: Alignment Troubles #qcx #20m #alignment #bpf

Ronald Taylor
 

Mike, this symptom sounds more like a problem with the large winding of T1. Like it's not in the circuit. Please check with your ohm meter to see that it is soldered property. Especially check the ground connection as that is the one that usually causes issues. You can check for D.C. continuity across C1 since the coil winding and C1 are in parallel.

I have built one QCX with no large winding on T1 and no C1 installed, in order to get multi-band receive capability and the BPF measurement shows about 6 or 7 on the display and receive sensitivity is very good. I don't live near any major RF sources so I don't have any interference issues without the BPF in the circuit. Other's results may vary. 

In one and only one case out of many, I found C1 to be intermittent. This was the earlier plastic capacitor that couldn't take a lot of heat and probably had done so in this case. But the symptoms were more erratic tuning in nature. The manual does say to shoot for level 9 readings but I usually see levels in the 8 range which are fine as long as the capacitor is not fully open or fully meshed. 

Whether or not you get the BPF sorted out, there should be plenty of signal preset to do the 3 null adjustments. if you can't get those to work, the most likely issue to look at first are all three pins on the volume control must be soldered to the board well. Use your ohm meter to make sure. Visual inspection isn't always enough.

Good luck ... 73 ... Ron


Re: #u3s QCXPTXCO install #u3s

KEN G4APB
 

Hi Hans,

on the QCX+, you say to remove C2 before fitting this tcxo module but it appears to be just supply decoupling. Does any similar capacitor need to be removed when modifying the Si5351A module?

73 Ken G4APB


Re: 5 Volt Supply

geoff M0ORE
 

If using a LM317 regulator, remember that the mounting tab is NOT at ground potential.

On 06/09/2020 10:45, Greg Winterflood wrote:
Jim K9GCS,

Tnx for including mention of the need for a heatsink.  In the photo attached to my previous post, a heatsink can be seen as a piece of alminium bolted to the regulator. It does get hot and could be larger, but so far so good. 
--
Greg Winterflood VK8KMD
Alice Springs, Central Australia
PG66wh

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