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Re: U3S drift/chirp - again!

 

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I assume you are using a 'standard' QRP-Labs synth board and not the OCXO version.

What Park Mode type are you using Ian??

Examples:? In mode 2 the park mode is inactive during that rather long calibration time you have, there may not be enough time after calibration ends and the QRSS starts for the park mode to 'warm up' the synth again.? In mode 4 the park mode is active all the time (during TX, between transmissions, and during calibration).? Keeping the Si5351A 'busy' with continuous park mode activity might help that 'initial hook' of drift.

Another possibility if the QRSS transmission is the first in the sequence, is to add a 'dummy transmission' as another "mode" before the QRSS "mode" (e.g. maybe a CW ident?) to take up the initial drift hook.

No idea why the transmission might appear to be 20Hz off.? The 20 240 Cal Time setting should set the U3S to within a couple of Hz at 28 MHz ... but now the Ref Freq has settled you might try something a little finer, like 01 240? (and as above, 240 is longer than is probably necessary).

73, Bob? ZL1RS
QCX Enclosure idea

 

? ? So I don't have access to a 3d printer and what I've seen it is amazing.? I have considered welding one together using a?Polycarbonate material.? Has anyone gone this route? With any success?? Any reason why it wouldn't work?

73;
Kurt - W2MW
Re: QCX 3D print

 

OK so I an new to 3d printing although I certainly understand the
technology. What is the 3d printer of choice these daya?

Thanks in advance.
73;
Kurt - W2MW

-------- Original Message --------
Subject: Re: [QRPLabs] QCX 3D print
From: "DAVE JAMES" <dave.james@...>
Date: Thu, November 30, 2017 12:44 pm
To: QRPLabs@groups.io

Dear group,
I have added a V2 top front case file to Thingiverse. I had some print
problems with the original although it worked ok with some cleanup. This
version prints great for me with 20% grid support. You need to cut out
the very thin disk in the Gain control recess after printing. Based on
much good forum feedback. Thanks guys.



QRP Labs QCX case by G8XUL






QRP Labs QCX case by G8XUL This is my attempt at a case for
the very excellent QRP Labs QCX transceiver. I'm very new to this so
maybe...








73
Dave G8XUL







On Tuesday, 21 November 2017, 16:06, DAVE JAMES
<dave.james@...> wrote:



My QCX in 3D printed case. The objective was to case the QCX with all
controls mounted on the board and without shaft extensions. The box has
room for a LIPO battery and has a connector for my GPS.

73,

Dave
G8XUL
Re: Low audio gain and no power out with 20m QCX

 

I found the audio also too loud. But in a menu I reduce the volume to 70 %
Re: U3S drift/chirp - again!

 

Ian,

Have you tried with NO PA voltage?
Of course I am assuming you can hear the U3S on a local RX rather than a remote report??

73 Alan G4ZFQ
Low audio gain and no power out with 20m QCX

STEVE NICHOLS
 

Hi,

I had my 20m QCX working perfectly, but after four or five cycles of WSPR TX the display went blank and the receiver stopped working. As I couldn't detect 5V anywhere I presumed the 7805 regulator had gone and ordered some more (it was very hot). They arrived this afternoon, but having replaced it the problem didn't go away. Anyway I eventually found a solder splash between two pins on Q3 (this must have happened after I took a turn off a nearby toroid). The radio is now back to life, but receive audio is low (unless the gain control is fully clockwise) and there is no TX output. It is hearing DX (K1RM in CT from the UK), but only with the volume virtually fully clockwise.

The sidetone is still incredibly loud, so sounds like the audio amp is OK.

Could it be that Q3 has blown (I thought that this would only impact the TX power) or is there another problem? I've ordered some more BS170s just in case.

My thanks to Hans for an incredible kit.

Steve G0KYA
Re: U3S drift/chirp - again!

 

Two problems: Look at the switch-on drift. It drops by about 10Hz in the fist couple of seconds! It's got the separate power regulator for FET PA. A heatsink and ?1 coin glued on to the crystal and still it 'chirps'.
Ian,

Have you tried with NO PA voltage?
That looks more like a voltage change than temperature related. It seems to stabilise too quickly.

The second problem is the frequency. The U3S readout shows 28.000.770 MHz, but I'm clearly transmitting a full 20Hz low. (Remember, Chris's grabber is not 20 Hz out.)
Is that related? It looks as if it might start correctly but quickly shoots down.


I've tried all the tricks regarding park frequency (150.000.000)? and
And all possible park frequencies? Once the rapid drop is cured maybe you'll get the heat drift down.

73 Alan G4ZFQ

the ref frequency has settled to 27.004.555, cal step time 20 240. The rig is in the U3S case on a shelf with a stable temperature and a decent 3A power supply.
U3S drift/chirp - again!

ian liston-smith
 

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Ian Liston-Smith has shared a?OneDrive?file with you. To view it, click the link below.

Not sure if the attached image will appear on the list, but it's me on 10m QRSS 200mW (the stray lines are aircraft reflections - please ignore) as grabbed by Chris's station a few miles away. His frequency calibration is pretty accurate, as can be confirmed by other 10m QRSS stations.


My U3S has the GPS QLG1 module which appears to be working - at least I'm getting the locator on WSPR transmissions and the clock is accurate.


Two problems: Look at the switch-on drift. It drops by about 10Hz in the fist couple of seconds! It's got the separate power regulator for FET PA. A heatsink and ?1 coin glued on to the crystal and still it 'chirps'.


The second problem is the frequency. The U3S readout shows 28.000.770 MHz, but I'm clearly transmitting a full 20Hz low. (Remember, Chris's grabber is not 20 Hz out.)


I've tried all the tricks regarding park frequency (150.000.000)? and the ref frequency has settled to 27.004.555, cal step time 20 240. The rig is in the U3S case on a shelf with a stable temperature and a decent 3A power supply.


Is there ANYTHING left to try to get the frequency right and reduce the drift? On 10m WSPR the drift is 3 to 4Hz and possibly higher, limiting my readability.


Thanks,


Ian, G4JQT



Re: Some L1 pictures?

w2eb@arrl.net
 

Jim,

???? As far as you can tell, did using a smaller diameter wire change the number of turns at all?? I'd rather not have to desolder the primary to add or remove turns.

Bill
W2EB

Re: Some L1 pictures?

 

On 11/30/2017 10:56 AM, Russ@va3rr via Groups.Io wrote:
Bill

K8IQY (Jim Kortge!) was kind enough to post a photo of his 80m QCX T1 wound with #30 AWG wire

/g/QRPLabs/message/17717?p=,,,20,0,0,0::Created,,k8iqy,20,2,0,6265682
And I have purchased some #34 wire with the thought of redoing T1 for my 80-Meter rig.? I suspect the change in wire size has little effect on performance, although, I've not measured it.? It took about 4 feet of #32 to wind it and less with #34, but I don't know the length at the moment.? I have more? photos that I can post of my T1 windings if someone would like to see them.

72,

Jim, K8IQY

Re: 17 meter QCX output issue.

cwfingertalker@gmail.com
 

Dennis,

The collector current limit for the 2N3906 is around 200ma. ?The suggested replacement PNP transistor MPS751 is around 2000ma. ?I think the kit draws 500ma on transmit so you need to find a PNP that will at least do 500ma.

Follow the suggestions in the previous post. ?Also check the continuity from the RF connector through L1, L2 and L3 with a VOM. ?That will confirm they are connected up to C29. ?

The other thought is one of the power FETs is not soldered in good. ?Reheat all three final FETs.

Keep poking around. ?

Bill N7EU

Re: Some L1 pictures?

 

Bill

K8IQY (Jim Kortge!) was kind enough to post a photo of his 80m QCX T1 wound with #30 AWG wire

/g/QRPLabs/message/17717?p=,,,20,0,0,0::Created,,k8iqy,20,2,0,6265682

Re: 17 meter QCX output issue.

 

Denny, if it turns out that you need an want an MPS751, I'll be glad to stick one in an envelope and mail it to you. (I bought a few extra when I replaced mine)

?

Steve, N4IAG

Some L1 pictures?

w2eb@arrl.net
 

All,

???? I have a 80M and a 40M QCX on the way.? The description of how to wind the "long" section confuses me slightly. Do you: "scramble" the windings as you progress along the length of the winding...wind to the end of the allotted space, then just pile the rest of the windings near that end...wind to the end of the space, then scramble the remainder over the entire area of the winding...???

Does anyone have a picture of their final result to illustrate a functional method?

Or, I was thinking of using smaller diameter wire and making it a typical single winding (only for that winding, the other 3 would stay their original size).? Would that lower the Q enough to degrade performance at all?? The PITA factor of using very fine wire is less of an issue to me than a performance hit.? Opinions?

Bill
W2EB?

Re: JT-9 working well tans Atlantic on 2200 meters, but no spots uploaded?

 

Using "CQ 2E0ILY IO82" will get you on pskreporter .
Jim

Re: 17 meter QCX output issue.

 

Thanks, yeah I did poke around with a plastic tool looking for a poor or cold solder joint on the inductors and any of the transmitter parts, as mentioned above. I also did bend the tab away from the coil. However the MPS2907 sounds interesting. Looking for a substitute, but it seems although it's a general purpose PNP, the common ones I have around don't seem to cross. I assume the common 2n2907 probably won't work. Anyone try a 2n3906? I may have some of them around?

On Thu, Nov 30, 2017 at 9:04 AM, Daniel Ekman SA2KNG <knegge@...> wrote:
Also, check Q6, the voltage at L4 should not be a solid ~12V. If this transistor is broken the envelope shaping does not work, the sharp rise times can lead to instability.
If it's broken (and MPS2907) you should change it to the new type, it has been replaced by MPS751 in the later kits.
Perhaps a smell test, or with lights off, if there's insulation problems in the LPF and arcing. This has happened when the metal tabs on the display shorted to the coil windings.


One more comment on QCX toroids - number of turns

 

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I went back to the original article in the G-QRP technical pages design by Ed Whetherhold W3NQN referenced under low pass filter kit.? The direct link is here: ? It appears the number of turns for the QCX low pass filter toroids agree with those in the referenced article for the 20 meter filter and the 30 meter filter (the ones I checked) but do not agree with the 40 meter filter. For 40 meters, The QCX manual calls out 24 turns for L2 and 21 turns for L1, L3. The referenced article (In terms of QCX low pass filter designations) calls out 21 turns for L2 and 19 turns for L1 and L3.? In addition, the article recommends filling the toroids with approximately 75 percent coverage.? Also note, the toroids should be wound counterclockwise to make the wires directly fit the pcb holes.? I also noticed that for the LPF kit, for 40 meter numbers of turns are the same as those called out in the QCX kit, which is too many turns.
?
Steve K1RF.

Virus-free.

Re: 17 meter QCX output issue.

 

Also, check Q6, the voltage at L4 should not be a solid ~12V. If this transistor is broken the envelope shaping does not work, the sharp rise times can lead to instability.
If it's broken (and MPS2907) you should change it to the new type, it has been replaced by MPS751 in the later kits.
Perhaps a smell test, or with lights off, if there's insulation problems in the LPF and arcing. This has happened when the metal tabs on the display shorted to the coil windings.

Re: 17 meter QCX output issue.

 

Denny,

Trouble shoot the interment problem with an insulated tool such as an 1/8 inch dowell rod. With key down and meter attached first poke around the coils for poor solder joint (lack of enamel scrapped off coil wire).

Sometimes the ground side of bypass capacitors do not solder well because of the extra circuit board mass, hence more heat required to form a good joint.

72 73
John
N3AAZ

Re: Low Power fix on QCX 80 and a suggestion for a possible addition to QCX test gear to measure inductance.

 

That would be fantastic. Speculations and possibly too obvious stuff follows:
With the LPF unpopulated you could place the resonant LC under test between the C28 and C27 points and use the already present signal injection to sweep and detect the peak. BPF would need to be disabled, like disconnecting C1 or similar.
If you want to have the entire LPF fitted it would be possible to redirect R34 to get the signal off board via the LC under test and fed into the BNC, or perhaps after C29.
The rest is firmware (: Auto/manual sweeping for finding the peak and perhaps tuning the coils etc.

On Thu, Nov 30, 2017 at 4:38 AM, Hans Summers <hans.summers@...> wrote:

Yes, adding an inductance meter would be a nice feature... or some way of measuring/checking the toroids. I am thinking about how that could be done.?


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