Date   

Re: #wspr #u3s My first U3S ... WSPR not quite working #wspr #u3s

Alan G4ZFQ
 

What is the recommended TCXO?
Bruce,

There is no recommended, as you say the one mentioned, the FOX, is a jumper. Some use it on HF with no apparent problems although my obsevations suggest that under poor propagation spots could be lost on the higher bands.

I've kept notes on those reported here:- https://sites.google.com/site/g4zfqradio/incircuitprogramatmel168#Testing%20TCXOs
Would it be better for me to order up a new synthesizer kit, rather than
try to remove the crystal from my current board?

I have about 5 I play with. They also fit the VFO and, depending how you build it, the Progrock.

73 Alan G4ZFQ


Re: U3S Case front panel push buttons

Brian Summers
 

Mouser list a switch 629-GPB023B05BR which looks like it will fit the same diameter hole. Probably much better quality I would think.

Brian VE7JKZ

On 12/6/2018 9:44 AM, Alan de G1FXB via Groups.Io wrote:
To prevent excess heat reaching the switch body, clamp a haemostat* between the switch and the tag.
*A pair of needle nose or pointed pliers held shut with an elastic band is a good substitute.

Alan
On 06/12/2018 17:02, Curt M. wrote:
I'm sure there's probably something else out there but it seems like the key with those switches is not put too much heat on the terminals when you solder the wires in place.  They seem to act very similar to relay contacts when you put too much current across them.  We used to always say that the contacts were "gulled", not sure if that is the correct spelling or even the correct term but that's what we used to say where I worked a number of years ago.

When I solder those terminals I quickly push and release the button multiple times as soon and I pull the soldering iron tip away.  There were times a while back that the button would stick on the in position and it was from too much heat.  Now they seem to hold up better with a lighter touch with iron but those switches are not good quality right out of the gate so I know what you are saying.


Re: QCX CW transceiver

N3MNT
 

I used thin strips of masking tape to keep coil neat.  One possible for those having issues getting the TI wires in the correct holes would be a thin piece of mica about 1" x 1" with the proper hole spacing so wires could  be properly spaced making it easier to mount .


Re: No GPS data with U3S - For Hans

geoff M0ORE
 

First send appeared here OK .

On 12/6/2018 10:39 PM, Brian Summers wrote:

Strange, I sent this several hours ago but it never appeared. Let me try again.

Brian VE7JKZ



-------- Forwarded Message --------
Subject: Re: [QRPLabs] No GPS data with U3S - For Hans
Date: Thu, 6 Dec 2018 09:32:23 -0800
From: Brian Summers <ve7jkz@...>
Reply-To: QRPLabs@groups.io
To: QRPLabs@groups.io


I've managed to come up with a procedure for repeating my problem. I've got the unit mode indices programmed so it operates as follows:

1. Power on U3S. Ultimate3S 3.12a appears. Then the display switches to GPS data as it should.

2. Press the Menu button once and the display reads:

0]-0-000,473,000
TX CW-------00-0

3. Press the menu button again and the displays reads:

1]-0-000,473,000
TX CW-------00-0

4. All the above really shows is that I have the same message in mode index 0 and 1. Not intentionally I might add. I'm new to the U3S so this is all happenstance.

5. Now power off/on. Once again the Ultimate3S screen appears followed by GPS data.

6. Press the menu button once and see the display as para 2 above.

7. Now press the edit button twice to enable. The display will show:

0] 0 000,473,000
TX CW       00 0

8. Power off/on. The Ultimate 3S screen appears, the GPS data does not appear and instead the display shows as follows. The beating heart appears where it should.

0] 0 000,473,000
TX CW

9. Press the menu button again and see:

0] 0 000,473,000
TX CW       00 0

10. Press the menu button again and see:

1]-0-000,473,000
TX CW-------00 0

11. You can see from 8 and 9 that I've created two messages identified with mode index 0]. Now you can repeat from para 8. The unit goes directly from the Ultimate 3S screen to the first mode setting every time, bypassing the GPS data screen. It all repeats.

12. To recover from this situation power off/on as para 8, go to the screen shown in para 9, then press the edit button twice to disable the mode setting. Now power off/on and GPS data will follow the Ultimate 3S screen.

Doubtless there are other ways of demonstrating this but the above is repeatable for me. Here's hoping that when I post this the formatting does not change........

Brian VE7JKZ



On 11/30/2018 8:34 AM, Brian Summers wrote:
GM Alan,

For the record my notes show the following when trying to set up for 473Khz.

0] 0 000,473,000 then on the line below, TX CW.  Call this message A

now press the menu key and the display shows:

0] 0 000,473,000 then on the line below, TX CW      00 0.  Call this message B.

Under these conditions there is no GPS data. Now disable message B, switch off/on, then GPS data appears immediately following the Ultimate 3S information screen.

I suppose I could spend more time on this trying other modes and messages but it can be very time consuming particularly with the case mounted push button switches which I find to be very flimsy and troublesome. For now I'm content to know that if I have no GPS data and scroll the menu to find two messages with the same number, I know what to do about it.

73 Brian VE7JKZ


On 11/30/2018 2:42 AM, Alan G4ZFQ wrote:
Strange thing is, no error message appears.

 Brian,

I guess if Hans knew it would happen there would be no error message because he had put it right!

>when two almost identical modes are set with the same band number

Maybe let Hans know exactly what settings, what are "almost identical" modes?

73 Alan G4ZFQ










Re: si5351a #synth

Dave New, N8SBE
 

Hans,

Had a crystal oscillator issue a few years ago that cause a lot of head scratching.  We had been producing said module for several years with no problems, when suddenly we had a rash of dead modules (no oscillation) after they had been outside overnight in desert air that veered toward freezing, but not below.

We found ultimately that the oscillator was failing to start under low temperature conditions, but our modules are meant to operate over -40C to 85C and had been tested to that repeatedly over the current production runs.

Long story short (too late), we found that the original design had been marginal, in that the recommendation of the microprocessor manufacturer didn't line up with the recommendations of the crystal supplier.  Production variation had exposed the margin, and thus, we started seeing failures at low temperature.  So, after a lot of back and forth, we lowered the value of the ballast resistor in the tank circuit to increase the feedback, and voila! all the issues went away.

Several more years (and a few million) modules later, we have never seen another oscillator failure in the field.

Lesson:  Every component has a data sheet, and often, they DON'T agree with those components' datasheets they need to interface to.  Sometimes it takes a whole engineering team (and their OEM customer breathing down their back) to bash heads (and those of the component suppliers) until an optimal solution is found.

73,

-- Dave, N8SBE

-------- Original Message --------
Subject: Re: [QRPLabs] si5351a #synth
From: "Hans Summers" <hans.summers@...>
Date: Wed, December 05, 2018 11:30 am
To: QRPLabs@groups.io

Hi Richard

Thanks for your comprehensive reply. How do you find time - do you ever sleep?

A lot more than I used to, unfortunately... until I'm fully back to normal health levels I sleep all I can!

2. What spec are the crystals you use? I looked at Farnell, RS, Rapid, Mouser and Digi-Key. Only Digi-Key have non-SMD in stock - all the others only have them with much higher load capacitance.

No particular spec. Just generic 27MHz fundamental-mode crystals.

I stopped believing in adding capacitors to crystals a few years back. The Ultimate3S kit still has pads for the originally supplied 22pF capacitors but they are no longer supplied or recommended. It was found that sometimes the 20MHz crystal wouldn't oscillate with the capacitors in place. But it always oscillates without them. So on the principles of the guy who designed TVs in ye olde days and used to remove one component at a time until it stopped working... same theory, I stopped putting capacitors in the circuit.

The fact the 27MHz Si5351A crystal tends to oscillate around 27.004 and the 20MHz Atmel AVR crystal at around 20.006MHz... indicates ideally a bit of capacitance would be needed. But stray PCB capacitance etc is enough to make sure everything always works, and we don't need them to be precisely on frequency either. 

One way to have trimmed the reference oscillator would be a trimmer capacitor on one side of the crystal, commonly seen. But we just do it in software... as long as the software knows the oscillation frequency it just takes it into account when calculating Si5351A values and everything comes out on frequency. It saves physical parts (the trimmer capacitor) and it also means you can employ a GPS to let the software accurately measure the actual oscillation frequency itself. Just perfect all round.

So just buy any 27MHz crystal and proceed regardless. Do make sure it is a fundamental mode one though not 3rd harmonic type.

4. I now understand why level shifters are not needed - I will remove them from my project. The outputs are open-collector as it requires wired AND so, as long as the pull-ups are to the lower voltage, it is safe. The only consideration is if the lower logic levels are OK for the higher voltage device. I have a feeling there are a very large number of unnecessary I2C level shifters in the world. As long as I am in control of the hardware design I can guarantee there are no pull-ups to 5V.

Hahaha I like that thought, but the large number of unnecessary I2C level shifters in the world! I'd add, a lot of other logic level shifters also unnecessary. It's important not to design recklessly but it sometimes seems there's a tendency to be too conservative!

73 Hans G0UPL 


Re: QCX CW transceiver

John VA7JBE
 

What I did on my T1 was to leave the tails end of all the wires at different lengths, going from longer to shorter in a clockwise direction.  That way I was able to insert one or two wires at a time, pull them through, and then move on to the next pair without having to worry about running out of space or getting the wires mixed up.  I got the idea from Hans' method of building the 50-ohm Dummy Load kit.  If there's ever an update to the QCX manual, it might be worth including this method.

You can find a better illustrated explanation here, starting at step 3.5  https://qrp-labs.com/images/dummyload/dummyload.pdf

Cheers,
John VA7JBE


Re: No GPS data with U3S - For Hans

Brian Summers
 

Strange, I sent this several hours ago but it never appeared. Let me try again.

Brian VE7JKZ



-------- Forwarded Message --------
Subject: Re: [QRPLabs] No GPS data with U3S - For Hans
Date: Thu, 6 Dec 2018 09:32:23 -0800
From: Brian Summers <ve7jkz@...>
Reply-To: QRPLabs@groups.io
To: QRPLabs@groups.io


I've managed to come up with a procedure for repeating my problem. I've got the unit mode indices programmed so it operates as follows:

1. Power on U3S. Ultimate3S 3.12a appears. Then the display switches to GPS data as it should.

2. Press the Menu button once and the display reads:

0]-0-000,473,000
TX CW-------00-0

3. Press the menu button again and the displays reads:

1]-0-000,473,000
TX CW-------00-0

4. All the above really shows is that I have the same message in mode index 0 and 1. Not intentionally I might add. I'm new to the U3S so this is all happenstance.

5. Now power off/on. Once again the Ultimate3S screen appears followed by GPS data.

6. Press the menu button once and see the display as para 2 above.

7. Now press the edit button twice to enable. The display will show:

0] 0 000,473,000
TX CW       00 0

8. Power off/on. The Ultimate 3S screen appears, the GPS data does not appear and instead the display shows as follows. The beating heart appears where it should.

0] 0 000,473,000
TX CW

9. Press the menu button again and see:

0] 0 000,473,000
TX CW       00 0

10. Press the menu button again and see:

1]-0-000,473,000
TX CW-------00 0

11. You can see from 8 and 9 that I've created two messages identified with mode index 0]. Now you can repeat from para 8. The unit goes directly from the Ultimate 3S screen to the first mode setting every time, bypassing the GPS data screen. It all repeats.

12. To recover from this situation power off/on as para 8, go to the screen shown in para 9, then press the edit button twice to disable the mode setting. Now power off/on and GPS data will follow the Ultimate 3S screen.

Doubtless there are other ways of demonstrating this but the above is repeatable for me. Here's hoping that when I post this the formatting does not change........

Brian VE7JKZ



On 11/30/2018 8:34 AM, Brian Summers wrote:
GM Alan,

For the record my notes show the following when trying to set up for 473Khz.

0] 0 000,473,000 then on the line below, TX CW.  Call this message A

now press the menu key and the display shows:

0] 0 000,473,000 then on the line below, TX CW      00 0.  Call this message B.

Under these conditions there is no GPS data. Now disable message B, switch off/on, then GPS data appears immediately following the Ultimate 3S information screen.

I suppose I could spend more time on this trying other modes and messages but it can be very time consuming particularly with the case mounted push button switches which I find to be very flimsy and troublesome. For now I'm content to know that if I have no GPS data and scroll the menu to find two messages with the same number, I know what to do about it.

73 Brian VE7JKZ


On 11/30/2018 2:42 AM, Alan G4ZFQ wrote:
Strange thing is, no error message appears.

 Brian,

I guess if Hans knew it would happen there would be no error message because he had put it right!

>when two almost identical modes are set with the same band number

Maybe let Hans know exactly what settings, what are "almost identical" modes?

73 Alan G4ZFQ










Re: QCX CW transceiver

Ray Worrall
 

Hi David,

Nail polish works just fine.  Did this on two kits.  On the primary winding try to keep it under a bit of tension, to prevent unraveling, while drying

72

Ray VE7AVG/VA7SK



From: David Wilcox via Groups.Io <Djwilcox01@...>
To: QRPLabs@groups.io
Sent: Thursday, December 6, 2018 2:03 AM
Subject: Re: [QRPLabs] QCX CW transceiver

Has anyone used any Q Dope or finger nail polish on the ends of the wires on the coil to hold the wires in place to make it easier to insert on the board?  In other kits the wires started to loosen while fiddling with them trying to get them all in the correct holes.

David J. Wilcox K8WPE’s iPad

On Dec 5, 2018, at 2:39 PM, Dave Redfearn <n4elm@...> wrote:

Ken,
I used 32 ga wire for my 80 & 60 Meter QCX builds on the main winding of T1 to get the winding to fit on the core.
I used the supplied wire for the three 5 turn links.

Tune up was normal.
I did have to remove 2 turns from the main T1 winding on the 60 Meter radio to have the capacitor set properly at ~ 3/4 mesh.

73 - Dave, N4ELM



Re: #wspr #u3s My first U3S ... WSPR not quite working #wspr #u3s

Bruce K1FFX
 

I think I've gotten the U3S/WSPR at, or close to, what I can achieve with a heat sink, foam, and rubber bands ... and it's pretty good.  I'm interested in doing the TCXO experiment ... a bit more kit building, and more entertainment as the daylight gets shorter and shorter here (Dec. 14 is the first later sunset by 1 minute, but still losing sunrise daylight until the solstice).

What is the recommended TCXO?  I've read that some parts have this frequency jump behavior which must be avoided for WSPR usage.  I don't know if the part mentioned in the synthesizer assembly manual exhibits this behavior or not.  For my ability, a part that can be mounted to the pads on the top of the synthesizer board would be preferable.

Would it be better for me to order up a new synthesizer kit, rather than try to remove the crystal from my current board?

Thanks for any suggestions!

Bruce K1FFX


Re: #wspr U3S for 2m WSPR: How to remove the frequency-swing at start of transmission #wspr

Alan G4ZFQ
 

Changed to basic crystal reference.

I show my RX at ~27.005MHz of the crystal frequency with Park mode 3 at the end of one TX/beginning of another. And two using Park mode 0, one at the start after idle, one between two transmissions.
"Start of TX from Parkmode3" shows a small section of the cyclic movement on 2m.

The initial jump at the start of the transmission is quite fast, probably what Henning sees on 2m.
Personally I do not think the initial rapid frequency shift is of any real consequence for WSPR.
After another hour or so 1032 13 -0.5 144.490529 2 G4ZFQ IO90 0 a drift of 2Hz, not yet as good as Henning but not too bad.
And 1042 13 -0.8 144.490540 0 G4ZFQ IO90 0 Zero drift.
But after that it began to drift again, temperature? Not really, more a slow cyclic drift. Removed Synth module LM317, fitted low drop 3V3 regulator AMS1117, an Ebay module. No difference.
I am thinking this is not entirely a heat-related problem, switching inside the Si5351 as the frequency is changed alters the capacitive loading on the 27MHz crystal? The cyclic drift could be associated with the pattern of WSPR tones.
Now in another thread Hans reminds me that there are no loading capacitors on the crystal (apart from those inside the Si5351 which are lower than specified) Is the crystal therefore more sensitive to loading?
So, in goes my Adafruit module with a 25MHz SM crystal.
This is looking promising. Even though 25MHz means the WSPR frequency shift is compromised it is decoding reliably on 2m with drift 2 or 3Hz. Any fluctuation due to WSPR frequency changes was not obvious.
Now back to the basic 27MHz crystal Synth, put in two 15pF loading capacitors, hoping that would overwhelm the cause of the "modulation" of the 27MHz. It started almost dead on 27MHz, drifting down, settling about 60Hz down. But this was far worse, the 27MHz was not stable even when the U3S was idle.
That is about as far as I can go the Adafruit shows a simple crystal can work on 2m but my Synth board does not.
It is better to use a TCXO and, presumably, the QRP Labs OCXO.

(This is a U3S run with one BS170 and ~5V on the drain so not much heat generated. I have it in a custom box with the display on top, the synth module therefore at the bottom.)

Maybe Park mode needs to be considered carefully? Mode 0 gives an output, my observations see less than 30dB below the WSPR signal level at 144MHz. A setting of 150MHz works OK but if my figure is correct a signal will go out.

> You wonder about the source of 50 Hz sidebands. May I posit a cause?....

Glen,

Thanks for your thoughts. It is OT if my observations are of locally created spurii but I thought I should mention it so others may check.
I still observe spurii on HF with a different RX system all 50Hz apart, worst -44dB on 10m.
2m not noticed this time, in fact seems fairly clean. Strange, possibly just my test method.

73 Alan G4ZFQ


Re: U3S Case front panel push buttons

Alan de G1FXB
 

To prevent excess heat reaching the switch body, clamp a haemostat* between the switch and the tag.
*A pair of needle nose or pointed pliers held shut with an elastic band is a good substitute.

Alan

On 06/12/2018 17:02, Curt M. wrote:
I'm sure there's probably something else out there but it seems like the key with those switches is not put too much heat on the terminals when you solder the wires in place.  They seem to act very similar to relay contacts when you put too much current across them.  We used to always say that the contacts were "gulled", not sure if that is the correct spelling or even the correct term but that's what we used to say where I worked a number of years ago.

When I solder those terminals I quickly push and release the button multiple times as soon and I pull the soldering iron tip away.  There were times a while back that the button would stick on the in position and it was from too much heat.  Now they seem to hold up better with a lighter touch with iron but those switches are not good quality right out of the gate so I know what you are saying.


Re: No GPS data with U3S - For Hans

Brian Summers
 

I've managed to come up with a procedure for repeating my problem. I've got the unit mode indices programmed so it operates as follows:

1. Power on U3S. Ultimate3S 3.12a appears. Then the display switches to GPS data as it should.

2. Press the Menu button once and the display reads:

0]-0-000,473,000
TX CW-------00-0

3. Press the menu button again and the displays reads:

1]-0-000,473,000
TX CW-------00-0

4. All the above really shows is that I have the same message in mode index 0 and 1. Not intentionally I might add. I'm new to the U3S so this is all happenstance.

5. Now power off/on. Once again the Ultimate3S screen appears followed by GPS data.

6. Press the menu button once and see the display as para 2 above.

7. Now press the edit button twice to enable. The display will show:

0] 0 000,473,000
TX CW       00 0

8. Power off/on. The Ultimate 3S screen appears, the GPS data does not appear and instead the display shows as follows. The beating heart appears where it should.

0] 0 000,473,000
TX CW

9. Press the menu button again and see:

0] 0 000,473,000
TX CW       00 0

10. Press the menu button again and see:

1]-0-000,473,000
TX CW-------00 0

11. You can see from 8 and 9 that I've created two messages identified with mode index 0]. Now you can repeat from para 8. The unit goes directly from the Ultimate 3S screen to the first mode setting every time, bypassing the GPS data screen. It all repeats.

12. To recover from this situation power off/on as para 8, go to the screen shown in para 9, then press the edit button twice to disable the mode setting. Now power off/on and GPS data will follow the Ultimate 3S screen.

Doubtless there are other ways of demonstrating this but the above is repeatable for me. Here's hoping that when I post this the formatting does not change........

Brian VE7JKZ



On 11/30/2018 8:34 AM, Brian Summers wrote:
GM Alan,

For the record my notes show the following when trying to set up for 473Khz.

0] 0 000,473,000 then on the line below, TX CW.  Call this message A

now press the menu key and the display shows:

0] 0 000,473,000 then on the line below, TX CW      00 0.  Call this message B.

Under these conditions there is no GPS data. Now disable message B, switch off/on, then GPS data appears immediately following the Ultimate 3S information screen.

I suppose I could spend more time on this trying other modes and messages but it can be very time consuming particularly with the case mounted push button switches which I find to be very flimsy and troublesome. For now I'm content to know that if I have no GPS data and scroll the menu to find two messages with the same number, I know what to do about it.

73 Brian VE7JKZ


On 11/30/2018 2:42 AM, Alan G4ZFQ wrote:
Strange thing is, no error message appears.

 Brian,

I guess if Hans knew it would happen there would be no error message because he had put it right!

>when two almost identical modes are set with the same band number

Maybe let Hans know exactly what settings, what are "almost identical" modes?

73 Alan G4ZFQ










Re: QCX CW transceiver

Roland Williams
 

I used clear nail varnish on the two I built and usually do that for anything that’s likely to move; it’s also good for stopping nuts from unscrewing to rattle around without making them impossible to remove. When I install transformers (the eight legged one is a great example) I just cut the wires to different lengths and use tweezers to put them in one at a time. Yes it’s fiddly but patience works fine. 

Roland AE6VL

On Dec 6, 2018, at 2:03 AM, David Wilcox via Groups.Io <Djwilcox01@...> wrote:

Has anyone used any Q Dope or finger nail polish on the ends of the wires on the coil to hold the wires in place to make it easier to insert on the board?  In other kits the wires started to loosen while fiddling with them trying to get them all in the correct holes.

David J. Wilcox K8WPE’s iPad

On Dec 5, 2018, at 2:39 PM, Dave Redfearn <n4elm@...> wrote:

Ken,
I used 32 ga wire for my 80 & 60 Meter QCX builds on the main winding of T1 to get the winding to fit on the core.
I used the supplied wire for the three 5 turn links.

Tune up was normal.
I did have to remove 2 turns from the main T1 winding on the 60 Meter radio to have the capacitor set properly at ~ 3/4 mesh.

73 - Dave, N4ELM


Re: U3S Case front panel push buttons

Curt M.
 

I'm sure there's probably something else out there but it seems like the key with those switches is not put too much heat on the terminals when you solder the wires in place.  They seem to act very similar to relay contacts when you put too much current across them.  We used to always say that the contacts were "gulled", not sure if that is the correct spelling or even the correct term but that's what we used to say where I worked a number of years ago.

When I solder those terminals I quickly push and release the button multiple times as soon and I pull the soldering iron tip away.  There were times a while back that the button would stick on the in position and it was from too much heat.  Now they seem to hold up better with a lighter touch with iron but those switches are not good quality right out of the gate so I know what you are saying.


Re: Active Aerials

ajparent1/KB1GMX
 

John, VA7JBE

No, That's designed for VHF and UP.  it would be terrible for a whip.

The amrad whip was a project maybe 10 years ago and use the CP600 series JFET.
The article is posted with this message.  FYI the fest are still available from teh source listed
as of last year when I ordered some.

For loops I included a copy of Chris Trask's paper, its a very good design.

FYI most MMIC amp including the PGA103 suck at less than VHF.  The coupling caps
are too small, The output choke used is too small a value for HF and the Phemt based
devices used are not very good at HF.

Allison


Re: Active Aerials

Alan de G1FXB
 

Perhaps it's the AMRAD active antenna featured QST Sept 2001 ?

Alan


On 06/12/2018 13:51, Karl Heinz Kremer - K5KHK wrote:
Allison,

do you have a title or an author for the QST article?

On Wed, Dec 5, 2018 at 01:10 PM, ajparent1/KB1GMX wrote:
AMSAT active antenna

 
--
Karl Heinz - K5KHK


Re: Active Aerials

Karl Heinz Kremer - K5KHK
 

Allison,

do you have a title or an author for the QST article?


On Wed, Dec 5, 2018 at 01:10 PM, ajparent1/KB1GMX wrote:
AMSAT active antenna

 
--
Karl Heinz - K5KHK


Re: Active Aerials

Graham, VE3GTC
 

Try the PGA-103 MMIC (Mini-Circuits brand).

while not targeted for MF/HF use it does work remarkably well at that
frequency range.

VHF and up oriented but a good all round intro to the device:

http://www.w1ghz.org/small_proj/Simple_Cheap_MMIC_Preamps.pdf


https://www.sv1afn.com/pga103m.html

Active antenna preamp for HF use:

http://www.g8jnj.net/activeantennas.htm


cheers, Graham ve3gtc

On 12/6/2018, "erik@kaashoek.com" <erik@kaashoek.com> wrote:

I did try a MICC as amplifier for an broadband loop but I found they either have insufficient gain (as their 50 ohm input impedance is badly matched with the loop) or when cascaded tend to get overloaded due to the huge dynamic range of the received signals.
But maybe you can find better MICC's then I tried.
Get one with the highest device voltage as second amp

--
Erik@Home





U3S Case front panel push buttons

Vernon Matheson
 

Hi all,

 

Has anyone found a better quality push button . I replaced the original with ones from Ebay…same type and they have not lasted that long. Get loose inside and start skipping and double clicking etc.

 

Vernon


Re: #qcx #problem Radio newbie and QCX large audio hum... #qcx #problem

KB3USG
 

Hey everyone,

I appreciate everyone's feedback and suggestions.

On 2018-12-03 18:09-0700, Ronald Taylor wrote:
First, No it is not right for this kit to have huge hum by touching the pot
and most stuff around it. Normally I would think you could get some hum by
touching the high side or the center pin (wiper) of the pot or by touching
the input pin 6 on IC10 But touching the pot shaft or housing or other
spots should not necessarily create lots of hum. This is grounded to the
circuit board.
Thanks for this, Ron. I did check out the pot as you suggested, and I
couldn't determine anything really physically amiss. However ...


My current plan is to:
* Recheck the board voltages and see whether anything has changed
radically from before.
I did this, and nothing was really very different from the readings in
the manual (or from my first check-out of the voltages across the
board).

However... when I was holding the board on one edge and my fingers
touched the case of the 7805 regulator, the hum went away. Really
sounding like a grounding issue.

I'm thinking that I've done some irreversible damage to the pot that was
not recoverable when I backed off the tension on the pot (I wouldn't
think this possible, so I'm grateful for some of the remarks in the
manual).

I'll hunt down a pot to put in place for now and see whether that makes
everything better.

And then get to this:

* (As part of my work peaking the BPF), take a couple of winds off
the T1 coil.
I'll keep updating the thread as I make progress.

Again, thanks to everyone who's reading these messages and musing to
themselves, and to those who have spoken up with some advice for me.

Thanks,
Paul
KB3USG