Date   

Re: U3S remaining issues I have

LUCIEN WILDER
 

Hi Dave,
I put the cover on my homebru 50dB pad, there was no difference. It could be that there is not enough shielding still.


Re: GPS Port Bama Enclosure

Shirley Dulcey KE1L
 

Thanks for letting us know. Adafruit is not currently shipping except for essential orders, but you can order Adafruit products from Digikey or Mouser; those distributors are still shipping.


On Thu, Apr 2, 2020 at 12:53 PM Mike Besemer - WM4B <mwbesemer@...> wrote:

For everyone’s info, Adafruit is not currently shipping.

 

Mike

WM4B

 

From: QRPLabs@groups.io [mailto:QRPLabs@groups.io] On Behalf Of Jim - W7EZN via groups.io
Sent: Wednesday, April 1, 2020 1:35 PM
To: QRPLabs@groups.io
Subject: Re: [QRPLabs] GPS Port Bama Enclosure

 

Update--

I've decided to go with these
According to the data sheet the 4-pin model should fit the opening spot on.
--
Jim, W7EZN    73!


Re: VFO Signal Generator with incorrect fundamental and sinusoidal contamination #vfo

Hans Summers
 

Hi Alan

Those PX27.000T crystals are exactly the ones I am talking about - they are 3rd overtone crystals, so they oscillate in the circuit at about 9MHz and this is why your frequency is 1/3 the expected value. This is also the reason for the rather large frequency error (13kHz). It could also cause poor spectral purity because the Si5351A PLL is designed to operate with reference frequencies in the range 25-27MHz. 

I will contact you off list about sending you a replacement crystal. I still have a whole bag of "real" fundamental mode 27MHz crystal (the inscription on the case of these reads "27.000") from that time some years ago when the batch got "polluted" by 3rd harmonic crystals. 

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

On Fri, Apr 3, 2020 at 6:14 AM alan bohne <alan.bohne@...> wrote:

Hello Hans

I purchased the VFO/Signal Generator kit in the 2018 timeframe.  It has firmware version S1.04.  The 27 MHz crystal has the chars “PX27.000T” imprinted on the canister top; I added a picture in my photo file.  I hooked up the VFO/SG to a well calibrated transceiver thru a resistive 101 dB (max) attenuator.  I reset the “multiplier” on the VFO/SG to “1” and the IF Offset to 3.5 MHz (i.e. clk1 set to anything nonzero).   I ran 4 quick tests and in each test a strong fundamental and third harmonic signal were observed, other signals (many detected) were between 30 - 50 dB lower in power, as estimated by adjusting the attenuator settings.  As noted in a prior post, the third harmonic was offset from the VFO setting by a stable value of approximately 13 khz/3.5 Mhz of VFO setting.  The short table below includes a rough estimate of the strength (+ =>  stronger) of the fundamental as compared to the third harmonic ( ~ VFO setting).  Note that the LPF automatically switched into use was that assigned to that band (e.g. 80m LPF for VFO setting of 3.5 MHz, etc.), so the reduction of third harmonic power due to the LPF should be minimal.    When the transceiver was tuned to the VFO (LCD) setting, only nominal noise was detected.  

                                           Observed                     Observed

VFO setting          Fundamental frequency    Third harmonic

  3.500                           1.172   (+10 dB)                  3.513

  7.000                           2.343   (+ 10 dB)                 7.027

10.000                           3.345   (+10 dB)                10.037

21.000                           7.027   (~ same)                21.081

 

While I did not post the clk1 squarewave images from the usb Osc, the waveforms were quite good with only a very minor ripple, immensely better than the waveforms from clk0.  Finally, I still did not see any clk1 freq displayed on the LCD in accordance with the “#C1” descriptor.  

 

Aside: I will read your discussion re using an Osc to view HF waveforms.  Despite your misgivings, I did find this exercise with the Osc very helpful.  I would not have unraveled the observed VFO behavior, the differing behavior between clk0 and clk1, and the presence of a predictive offset otherwise.  Hopefully, I can ultimately use the VFO/SG for its intended purpose of calibrating my other transceivers and as a source of good sinusoids for other testing purposes.

Tnx, Alan, K1ARW


Re: GPS Port Bama Enclosure

scot forshaw
 

From my experience I found that shielding the cable was pretty much essential in weak signal conditions, might be worth factoring in for others.


On Thu, Apr 2, 2020 at 5:53 PM Mike Besemer - WM4B <mwbesemer@...> wrote:

For everyone’s info, Adafruit is not currently shipping.

 

Mike

WM4B

 

From: QRPLabs@groups.io [mailto:QRPLabs@groups.io] On Behalf Of Jim - W7EZN via groups.io
Sent: Wednesday, April 1, 2020 1:35 PM
To: QRPLabs@groups.io
Subject: Re: [QRPLabs] GPS Port Bama Enclosure

 

Update--

I've decided to go with these
According to the data sheet the 4-pin model should fit the opening spot on.
--
Jim, W7EZN    73!


Re: Question regarding measuring power output.

Andy V. Borisenko
 

gentlemen, you confuse the concepts of measurement and some indications on some display of some indicator.
the oscilloscope is, in principle, not a device for measuring RF power. only by indirect formulas is it possible to somehow approximately determine the power.
I am not a snob, but I work specifically with measuring equipment and I know well that many factors influence the correctness of measurements (and not indications on some kind of scoreboard).
the easiest way at home is to roughly determine the power of the QCX by the method of current consumption by the transceiver. since this is a typical and well-known transceiver circuit, the readings should be approximately the same for all cases.
I apologize if someone didn’t like my message :)


Re: QCX 40 No Sidetone and output is raspy

Gregg Myers
 

Hello Mike,

Is is possible you are picking up some RF interference from the higher power output of the Amp? I had a similar bad sounding sidetone and then made sure I cleaned up my rats nest of RF cables and put the DC power cables through a couple of EMI toroids. That cleaned my sidetone right up.

73,
Gregg 
w7grm

On Thu, Apr 2, 2020 at 9:17 PM Michael Lloyd <mikell@...> wrote:
:-/ Well, I put the QCX signal into a 50 ohm pass thru terminator then to the scope and the sine wave is gorgeous. 7.020 Mhz, which is exactly the frequency I set. About 2.5W out. No problems at all. I'll hook the amp up tomorrow and take a look at it's sine wave. I don't know what the lack of sidetone is about but I'll keep digging. I'll try another headset too...
--
73
NE5U

Mike


Re: QCX 40 No Sidetone and output is raspy

 

:-/ Well, I put the QCX signal into a 50 ohm pass thru terminator then to the scope and the sine wave is gorgeous. 7.020 Mhz, which is exactly the frequency I set. About 2.5W out. No problems at all. I'll hook the amp up tomorrow and take a look at it's sine wave. I don't know what the lack of sidetone is about but I'll keep digging. I'll try another headset too...
--
73
NE5U

Mike


Re: VFO Signal Generator with incorrect fundamental and sinusoidal contamination #vfo

alan bohne
 

Hello Hans

I purchased the VFO/Signal Generator kit in the 2018 timeframe.  It has firmware version S1.04.  The 27 MHz crystal has the chars “PX27.000T” imprinted on the canister top; I added a picture in my photo file.  I hooked up the VFO/SG to a well calibrated transceiver thru a resistive 101 dB (max) attenuator.  I reset the “multiplier” on the VFO/SG to “1” and the IF Offset to 3.5 MHz (i.e. clk1 set to anything nonzero).   I ran 4 quick tests and in each test a strong fundamental and third harmonic signal were observed, other signals (many detected) were between 30 - 50 dB lower in power, as estimated by adjusting the attenuator settings.  As noted in a prior post, the third harmonic was offset from the VFO setting by a stable value of approximately 13 khz/3.5 Mhz of VFO setting.  The short table below includes a rough estimate of the strength (+ =>  stronger) of the fundamental as compared to the third harmonic ( ~ VFO setting).  Note that the LPF automatically switched into use was that assigned to that band (e.g. 80m LPF for VFO setting of 3.5 MHz, etc.), so the reduction of third harmonic power due to the LPF should be minimal.    When the transceiver was tuned to the VFO (LCD) setting, only nominal noise was detected.  

                                           Observed                     Observed

VFO setting          Fundamental frequency    Third harmonic

  3.500                           1.172   (+10 dB)                  3.513

  7.000                           2.343   (+ 10 dB)                 7.027

10.000                           3.345   (+10 dB)                10.037

21.000                           7.027   (~ same)                21.081

 

While I did not post the clk1 squarewave images from the usb Osc, the waveforms were quite good with only a very minor ripple, immensely better than the waveforms from clk0.  Finally, I still did not see any clk1 freq displayed on the LCD in accordance with the “#C1” descriptor.  

 

Aside: I will read your discussion re using an Osc to view HF waveforms.  Despite your misgivings, I did find this exercise with the Osc very helpful.  I would not have unraveled the observed VFO behavior, the differing behavior between clk0 and clk1, and the presence of a predictive offset otherwise.  Hopefully, I can ultimately use the VFO/SG for its intended purpose of calibrating my other transceivers and as a source of good sinusoids for other testing purposes.

Tnx, Alan, K1ARW


Re: Question regarding measuring power output.

Ham Radio
 

Here is a Basic program that you  that you can use.


--
73, Bernie, VE3FWF


Re: #QCX40 Rev5 LCD contrast adjustment appears to cause massive current draw #qcx40

Ham Radio
 

Had a quick look at the pics.  I noticed there are some possible shorts on the bottom of the board between traces.

I suggest fixing  those up and then verify with an ohmmeter on low range.


Good luck.


--
73, Bernie, VE3FWF


Re: Problem with 50W amp..

George Korper
 

Hi, I don't mind going too far. There was one other thing I learned 
in the process. After you snug up the IRF 510 in the heatsink, cut the protruding leads
down before you solder. THEN FOLLOW THE PIN SOLDERING ORDER IN THE MANUAL
THAT HANS RECOMMENDS. RIGHT, CENTER, etc. Don't deviate because the fist pin takes a
long time not necessarily a big iron. With the lead cut down, you can get the heat into the hole and let it blossom around the pin. 
If you do that and scrape every transformer lead, tin it, and then  solder, everyone comes out perfect and consistent and is easy. 
Since doing the above two things I have made six without incident. 


QCX 40 No Sidetone and output is raspy

 

I finally installed a jack in my QCX so I can could the 50W amp and test it all as a package. All of that worked. Just for grins I turned my FT-891 on to see what the QCX sounded like (transmitting into a dummy load). I was.. how should I say this, horrified at what I heard. I plugged in my headphones and also discovered that there is no sidetone. Just a thump sound. I'm about to take a look at the schematic but I thought I would see if anyone had any ideas.

I think that the QCX was working before I wired in the switching wire for the amplifier. It's been a few months since I finished the kit. I am not sure I didn't screw up one of the IC's. We'll see.
--
73
NE5U

Mike


Re: Question regarding measuring power output.

Jim Allyn - N7JA
 

On Thu, Apr 2, 2020 at 10:51 AM, Ed Kwik wrote:
Take a look at section 1.10 RF Power Measurements

 Just curious, what book is that from?  It looks like it could be a good book for several beginner  friends of mine.

Here's an RF detector I built about 35 years ago. It used to have an adhesive sticker with a calibration chart stuck to the back of the board, but apparently it fell off somewhere along the line.  The diode is probably a 1N34A.


Re: Receiver board frequency response

Phil Frost <indigo@...>
 


On Thu, Apr 2, 2020 at 8:26 AM Hans Summers <hans.summers@...> wrote:
The polyphase network manual http://qrp-labs.com/images/polyphase/polyphase2.pdf has a graph of measured audio response vs frequency and it is flat to about 2.5kHz. The primary intention of the receiver module was as a receiver for QRSS and WSPR signals at 1000-1600Hz audio.

Thanks Hans for confirming the frequency response is a deliberate design: this gives me greater confidence that there isn't some other issue with the hardware. I don't have the polyphase module so I had not seen that frequency response plot. Instead I'll be feeding the output to a USB audio interface and doing the DSP on a Raspberry Pi with some custom software.

For the sake of experimentation I did try eliminating the transformers, and the result does seem to be an improvement. Right off the bat I noticed the noise visible in the screenshots around 19 kHz went away. I'll try to do some more careful measurements after I get everything boxed.

It's looking like my remaining problems are software related. Oh, the joys of SDR :-) Thanks again for the great kits.


Re: Question regarding measuring power output.

Jim Allyn - N7JA
 

On Thu, Apr 2, 2020 at 12:30 PM, James Daldry W4JED wrote:
I guess I pulled it out of my navel.
I've probably done that a time or two myself!


Re: Question regarding measuring power output.

fred.g3srf@...
 

There seems to be confusion both with the difference between V p-p and V p and with the calculations.
A handy little program from DL5SWB called mini dB calculator can be found on the web and installed on your computer. There are several tabs to use. To calculate power from voltage you need the one labeled " U --> dB,uV,W,dBm"  and this has a very clear diagram showing the relationship between p-p, p and rms. You select which one you are using and the impedance, then input the voltage and it gives the power in Watts and dBm. The input volts can be nV up to kV so plenty of scope for QRP.


Re: Problem with 50W amp..

George Korper
 

But wait there's more: Not every IRF 510 works in the amp. So make sure you get them from 
a good house. Just pay shipping and handling, Hi Hi. 


Re: Problem with 50W amp..

George Korper
 

Gwen, forgot one more thing. Always do this into a dummy load. The Amp cannot handle SWR of certain
types depending on the load. above 1.6 to 1 things get dicey.  Especially if the bias is set even a tad too high, 

On Thu, Apr 2, 2020 at 5:29 PM Gwen Patton <ardrhi@...> wrote:
Hey, All.

I finished building the QCX amp best I could, but I'm running into a serious issue, and think I MAY have fried one or both of the finals...or messed something else up, I'm not sure.

It powers up ok. No smoke. Nothing seems to be getting overly warm. With the QCX in practice mode and the keying line connected, when I key the QCX the red light comes on in time with the key. I did what the instructions say about adjusting the trimmer, and it seems to be okay. But when I take the QCX OUT of practice mode and try to key the amp, things get weird.

On the QCX, it seems fine for the space of two dahs. Then the letter "P" comes up to the left of the S-meter graphic (I know this is also on when in practice mode, but that mode is definitely OFF at this point) and the unit ceases transmitting. It takes a few seconds for the QCX screen to clear, then it will key up again, but once more, it's only very briefly, then it fails again, same thing.

I've tried THREE different power sources for the amp. I've tried it at 12v, I've tried it at 20v, no difference whatsoever. It just falls over a second or so after being keyed, and it doesn't seem to have anything to do with the QCX end or the power supply. So I'm pretty sure I munged something up in construction. Now, the reason I think I may have fried at least one of the final transistors is that I got a $^@#$ consarned solder bridge on one transistor's connections, and it was a total pain in the ARSE to get rid of. I probably wound up heating the transistor too much in the process, but even with my heavier iron, it was really hard to get the solder enough to flow and get out of the bridge, even with lots of flux and fresh braid. I finally got it, but I think the damage was done at that point.

I don't SEEM to have shorts to ground or anything. One leg of course is connected to ground, so that's understood. Checking for shorts with the other legs, one has no reaction, the other shows continuity for about half a second, then it stops. That's on BOTH transistors, so if that's a sign of being blown, I blew 'em both. :/

IF, however, this sounds familiar, and I have some other issue going on, or anyone can think of some checks I can do with meter or wiggle scope, let me know what to check and to look for, and I'll try it and post back. I think I have some of those finals in my stock in case I need to replace them, but I want to narrow it down a bit before I go that route.

73,
Gwen, NG3P


Re: Problem with 50W amp..

George Korper
 

Allison had a great post on how to clear the hole after you snip the IR510 out,
Remove the leads, and heat the hole and tap quick on a table. Whamo the holes are like new. 
 Then start meticulously restoring the pads. 
And fuse the supply with a 4 amp fuse even if using a current limited supply. 
All that said look for the problem, but it may have actually been corrected in the process. 
It could be there was a problem in the mounting to the heat sink. That happened to me 4 TIMES!
Check that and don't tighten the screws too hard. 

On Thu, Apr 2, 2020 at 6:03 PM George Korper via groups.io <georgekorper=gmail.com@groups.io> wrote:
Ok this i have done. First after removing IR 510's you must clean the bridges in between the pads. 
I use M.G. Chemical solder braid # 452, but once you get a bridge between pads, it takes a magnifier and 
maybe an Exacto knife.You had to fry the finals and just go in there and bring everything back to where it was. 
You can check the transistors but the sad fact is it is easier to remove and go back to an initial condition than screw around. 
I have built quite a few and the last thing you want to do is rush and burn out all the traces. One slip and a cascade of trouble can happen so never probe around with the final in operation. Also bad finals can cause the problems you are seeing. The keying circuit can be
affected...not sure how but I've seen it. But check the keying circuit with a DVM any way.
And cool down, you'll find it. Take it easy but take it. Sometimes I just break em in half an order another one. 
Lately though they seem easy after the first half dozen. YOU ARE NOT ALONE!

On Thu, Apr 2, 2020 at 5:29 PM Gwen Patton <ardrhi@...> wrote:
Hey, All.

I finished building the QCX amp best I could, but I'm running into a serious issue, and think I MAY have fried one or both of the finals...or messed something else up, I'm not sure.

It powers up ok. No smoke. Nothing seems to be getting overly warm. With the QCX in practice mode and the keying line connected, when I key the QCX the red light comes on in time with the key. I did what the instructions say about adjusting the trimmer, and it seems to be okay. But when I take the QCX OUT of practice mode and try to key the amp, things get weird.

On the QCX, it seems fine for the space of two dahs. Then the letter "P" comes up to the left of the S-meter graphic (I know this is also on when in practice mode, but that mode is definitely OFF at this point) and the unit ceases transmitting. It takes a few seconds for the QCX screen to clear, then it will key up again, but once more, it's only very briefly, then it fails again, same thing.

I've tried THREE different power sources for the amp. I've tried it at 12v, I've tried it at 20v, no difference whatsoever. It just falls over a second or so after being keyed, and it doesn't seem to have anything to do with the QCX end or the power supply. So I'm pretty sure I munged something up in construction. Now, the reason I think I may have fried at least one of the final transistors is that I got a $^@#$ consarned solder bridge on one transistor's connections, and it was a total pain in the ARSE to get rid of. I probably wound up heating the transistor too much in the process, but even with my heavier iron, it was really hard to get the solder enough to flow and get out of the bridge, even with lots of flux and fresh braid. I finally got it, but I think the damage was done at that point.

I don't SEEM to have shorts to ground or anything. One leg of course is connected to ground, so that's understood. Checking for shorts with the other legs, one has no reaction, the other shows continuity for about half a second, then it stops. That's on BOTH transistors, so if that's a sign of being blown, I blew 'em both. :/

IF, however, this sounds familiar, and I have some other issue going on, or anyone can think of some checks I can do with meter or wiggle scope, let me know what to check and to look for, and I'll try it and post back. I think I have some of those finals in my stock in case I need to replace them, but I want to narrow it down a bit before I go that route.

73,
Gwen, NG3P


Re: U3S remaining issues I have

DL2ARL
 

Hello group, hello Andrew G8UUG,
I am a little confused about your advice above:

"make sure you have the highest frequency you are using in slot 5."

Well, OK, I would NOT have placed the highest frequency module in slot 1, the one that is far away from the PA. But I would have placed it in slot Zero, directly on the U3S, thinking that it will be closest to the PA transistors.
Am I wrong?
Thank you for the advice.

Otherwise, a splendid explanation. Because the group software here is so "dynamic" an I will probably never find the posting again, I will make a snapshoot of it.
Have a good time, 73 de Razvan, dl2arl