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I am not as experienced as many of you out there but feel that some recent experiences and issues?may be?useful?for some others completing a?kit for the first time
Firstly, I managed to build the QCX 80?and got it working first time thanks to the excellent instructions in the manual.
Key Issues
As I am learning CW (now 10wpm)?I am still using a straight key (Kent and Palm Radio PPK).
Both these keys switched on the tx when the key jack was inserted in the stereo socket and I resolved these issues as follows:
1) I changed the mono jack to a stereo jack for the Kent connecting to?tip and common/ground
2) I disconnected the green wire inside the PKK which connects to middle ring of stereo?jack?(Hannes advises that this modification is required for KX3 and similar rigs)
Please note that in this configuration the keys no longer work properly?in my LNR?MTR-3B where the middle ring needs to be connected to ground for straight keying
As an alternative, a mono socket can be connected to the PCB which I have also done.
"Stray RF"
As this was my first rig construction, I decided to place all components "onboard" and use the set on the bench.
The set is connected to a Resistive Bridge, L Tuner and an random length end fed Wire (no feeder) - I know this is not ideal but it works for the MTR
The resistive bridge has 3 positions: dummy load, tune and transmit.
In dummy load position, the tx keys properly.
However,?in tune and tx positions (RF applied to the antenna) the QCX appears to become unstable?after initial keying?with loud "hissing" (feedback ?)?and RF indicated on a FS meter.
Switching back to dummy load stops the effect
After re-positioning the tuner, bridge and key away from the QCX the problem appears to be resolved and keying can?takes place normally. It may be my imagination but this phenomenon appears worse with Kent key (with all that brass).
Consequently, I have concluded that there is stray RF from antenna feeding back into the QCX etc which is causing to run out of control.
Again, I have not experienced this with the MTR.
Obviously one possible solution would be to put the QCX in an metal/metal lined enclosure but I wonder whether this phenomenon is to be expected or whether it could be indicative of something within the QCX.I would be interested in receiving your comments.
Robin
G4DNP
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Robin; ? ? Now I am no expert in this area but what what I would suggest it appears you are not well grounded.? I have the QCX-20 and don't experience the issues you are.? However I have a Yaesu FT-920 which will cause me issues from time to time with stray RF.?? ? ? It would be best to find a good grounding location and to tie all of your equipment (rig, tuner, power supply & antenna) to it.? This should minimize the issues you are experiencing.??
.... or at least I'd start there...
best 72; Kurt - W2MW
-------- Original Message --------
Subject: [QRPLabs] QCX 80, key and stray RF Issues
From: robin.travis@...
Date: Thu, December 21, 2017 2:11 pm
To: [email protected]
I am not as experienced as many of you out there but feel that some recent experiences and issues?may be?useful?for some others completing a?kit for the first time
Firstly, I managed to build the QCX 80?and got it working first time thanks to the excellent instructions in the manual.
Key Issues
As I am learning CW (now 10wpm)?I am still using a straight key (Kent and Palm Radio PPK).
Both these keys switched on the tx when the key jack was inserted in the stereo socket and I resolved these issues as follows:
1) I changed the mono jack to a stereo jack for the Kent connecting to?tip and common/ground
2) I disconnected the green wire inside the PKK which connects to middle ring of stereo?jack?(Hannes advises that this modification is required for KX3 and similar rigs)
Please note that in this configuration the keys no longer work properly?in my LNR?MTR-3B where the middle ring needs to be connected to ground for straight keying
As an alternative, a mono socket can be connected to the PCB which I have also done.
"Stray RF"
As this was my first rig construction, I decided to place all components "onboard" and use the set on the bench.
The set is connected to a Resistive Bridge, L Tuner and an random length end fed Wire (no feeder) - I know this is not ideal but it works for the MTR
The resistive bridge has 3 positions: dummy load, tune and transmit.
In dummy load position, the tx keys properly.
However,?in tune and tx positions (RF applied to the antenna) the QCX appears to become unstable?after initial keying?with loud "hissing" (feedback ?)?and RF indicated on a FS meter.
Switching back to dummy load stops the effect
After re-positioning the tuner, bridge and key away from the QCX the problem appears to be resolved and keying can?takes place normally. It may be my imagination but this phenomenon appears worse with Kent key (with all that brass).
Consequently, I have concluded that there is stray RF from antenna feeding back into the QCX etc which is causing to run out of control.
Again, I have not experienced this with the MTR.
Obviously one possible solution would be to put the QCX in an metal/metal lined enclosure but I wonder whether this phenomenon is to be expected or whether it could be indicative of something within the QCX.I would be interested in receiving your comments.
Robin
G4DNP
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-- What are you using for a power supply?? Battery or AC supply?? You might be getting RF into the supply. Also, that antenna is going to use the rig as a counterpoise if you are not grounded well or the ground is at a high impedance at 80 meters.? Just a guess.
de K2TL.. since 1964
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I'm using a 3S LiPo battery (+/- 11.3V).
Antenna is located in an attic and equipment is in a first floor room.
A?short?counterpoise is connected at the L Tuner and runs around the floor.
(I'm working on the principle "a poor antenna is better than no antenna").
My interest is work portable whenever possible.
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Well, on 80 meters you probably need more than a short counterpoise, and you do not mention how long the random wire is.? A tuner can load up all kinds of poor antennas and just results in RF trying to go someplace it shouldn't.? I understand the antenna dilemma if you are dealing with restrictions.? But if you want your QCX to work then you will need to reconsider that antenna system...
de K2TL.. since 1964
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de K2TL.. since 1964
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Robin, let me say that if you are comfortable a 10 WPM you are not 'learning' CW, you are now a CW OP. Congrats. Now you are just increasing your speed! Like all the res of us. Regarding your RF problems, that is an age old issue with transmitters. Back in the tube (valve) days, we just called it RF in the shack. Was a time when I got RF burns on my lips if I let the mike touch them. A good perspective is to view everything outboard (antenna side) of a matching unit (so called tuner) as being antenna. It may look like a feedline, but it is radiating. Old radios just shrugged off RF in the shack until it was biting you too hard to put up with. However, with solid state gear, much less RF is tolerated. Shielding the radio in metal is good, getting all RF outside the shack is even better. Remember that a counterpoise is radiating too. The more work your 'tuner' is doing, the more RF in the shack. -- Wes ( I'm so old when I pass gas nothing comes out but dust)
AE6ZM
Hereford, AZ
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Thank you all for the input and comments - it has re-assured me to a great extent that the problem is external to the QCX.
I should add that?as inadequate as the?antenna system is, I have obtained RBN spots with the QCX?in continental Europe and Scandanavia as far as 1500km.
The same antenna even gave me a QSO with a K station a couple of months ago on 20m with my MTR-3B.
Many thanks again
Robin
G4DNP
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At some point I might want to ask you how you wound T1.? I have a 80 QCX being shipped now.? T1 looks like a challenge.? Congrats on your results!
--
de K2TL.. since 1964
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Jim;
Not sure about the 80m coil but I will say the 20m wasn't difficult at
all. After reviewing Han's manual I was able to wrap mine with ease.
For starters, you use one continuous wire. After winding the large
secondary I made a loop about 1 1/2" in length before starting the next
set of windings. I did this for all 4 windings. After I completed the
windings I snipped the end of the long loop between the windings and
removed the varnish. I used 320 grit wet/dry paper, dry. After all of
the legs were snipped and varnish removed I simply started inserting all
of the legs in their appropriate holes in the PCB. I snugged each lead
using a pair of ling nose pliers as I soldered it to the board.
I know the 80m coil has quite a bit more windings than the 20m but the
sequence with winding and installing should be the same.
best 72;
Kurt - W2MW
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-------- Original Message -------- Subject: Re: [QRPLabs] QCX 80, key and stray RF Issues From: "K2TL Jim" <k2tl@...> Date: Fri, December 22, 2017 8:20 am To: [email protected]At some point I might want to ask you how you wound T1. I have a 80 QCX being shipped now. T1 looks like a challenge. Congrats on your results! -- de K2TL.. since 1964
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Jim,
???? I wound mine with #34 wire for the long winding.? I used #26 for the other 3 windings.? I had to remove 6 turns from the core to get the capacitor to center when properly tuned, but it seems to work.? On a strong band like 80 it's hard for me to tell fine sensitivity differences, so I can't say if the slightly higher resistance of this wire matters.
Bill
W2EB
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Kurt/Jim
This is going a little off the original subject matter and there are in fact?a number of messages in the last month or so, including one of mine, regarding the winding of T1 for the QCX80
In any case, I ran out of the 28swg supplied and finally resorted to 30swg as I found that?27swg was not really feasible.
There will be some overlap and it looks a bit messy but it did work
The manual is clear about not winding one layer neatly over another.
Also, as reported by others, it may be worth adding a?few extra turns in case of adjustment during alignment as it would be easier to remove turns rather than add turns once the transformer is soldered in place.
I've added a photo below - it's a bit dark but you should get the idea.
It's is great fun building the kit?and I have just ordered a kit for 18m
Robin
G4DNP
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If you ever get the chance, I would appreciate a closer and brighter pic of T1..a picture tells a thousand words, as the saying goes. Thanks!
--
de K2TL.. since 1964
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Thanks Bill..but not sure how you did that.? Did you wind the other 3 over the long winding, or leave a space where the other 3 go, if I make my self clear..this is my problem.? I can't seem to conceptualize it.? can't even verbalize it, Hi!
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de K2TL.. since 1964
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Jim
Here is a slightly larger and lighter photo.
I think you can see the other 3 windings do not overlap the large secondary wing.
This long winding is wound first and you can get an idea of how much space to leave for the three short windings.
This is not necessarily the best example but it does work.
Make sure you choose a quiet time without interruptions !
Regards
Robin
G4DNP
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Here is my T1 from my QCX-20
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-------- Original Message -------- Subject: Re: [QRPLabs] QCX 80, key and stray RF Issues From: "K2TL Jim" <k2tl@...> Date: Fri, December 22, 2017 10:36 am To: [email protected]If you ever get the chance, I would appreciate a closer and brighter pic of T1..a picture tells a thousand words, as the saying goes. Thanks! -- de K2TL.. since 1964
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Thanks.. I think I am a hopeless case with this T1, Hi.. when I get my kit I'll be back to bother everyone, be assured!
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de K2TL.. since 1964
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Thanks..20 and even 40 is a no brainer, but 80 is going to be interesting.? I think I'm going to invest in some 34 awg :)
--
de K2TL.. since 1964
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Jim; ? Don't loose sleep over it... You will do fine.
Kurt
-------- Original Message --------
Subject: Re: [QRPLabs] QCX 80, key and stray RF Issues
From: "K2TL Jim" < k2tl@...>
Date: Fri, December 22, 2017 11:10 am
To: [email protected]
Thanks..20 and even 40 is a no brainer, but 80 is going to be interesting.? I think I'm going to invest in some 34 awg :) -- de K2TL.. since 1964
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Kurt Zimmerman
Wes WB7BR