Date   
GPS lights on constantly ... Is it working?

Liam Kingsmill <lumetters1@...>
 

Please, HELP!.  Using V3.12a Ultimate3S with QRPlabs GPS unit and the receiver.   Cleaned up all Error messages.  Still. WSPR mode seems not to be transmitting and the QRPlabs GPS seems not to be calibrating anything.   All three LEDs on the GPS unit stay lit ... no flashing.  No sound in headsets.

Perhaps I would benefit with a list of settings for WSPR transmissions.   Signed, DeeplyConfused.

Re: #qcx Linear vs Logarithmic: a note on the QCX volume control #qcx

Dave New, N8SBE
 

Hans,

Wonderful explanation and suggested 'fixes'.  Hopefully this writeup will find its way to the QCX 'mods' page on your web site, for future reference.

73,

-- Dave, N8SBE

-------- Original Message --------
Subject: [QRPLabs] #qcx Linear vs Logarithmic: a note on the QCX volume
control
From: "Hans Summers" <hans.summers@...>
Date: Sun, August 18, 2019 9:19 am
To: qrplabs@groups.io

Hi all

This came up a few times. Several people commented that they typically only use the first 10% of the audio gain pot, after that it is too loud. People also mentioned that the manual says the pot is a logarithmic one (also known as "audio taper") but the 5K pot supplied is actually Linear. 

We prefer Logarithmic for a volume control because this is how our ears perceive loudness.

I grew up thinking, all my life until relatively recently, that a pot labeled A is Linear and a potentiometer labeled B is Logarithmic. So 5KB (as in the QCX) would be 5K logarithmic. It probably actually WAS really like that. But not any more! Or perhaps, in some parts of the world but not others. The most common "standard" now appears to be that A means Log and B means Linear. I think that there are enough old pots and enough confusion that I would never again trust the A or B to tell me anything; best to refer to datasheets or in the case of scavenged (unknown) components, measure them. 

Most "audio taper" potentiometers aren't really logarithmic, they often contain two linear tracks over different parts of the rotation so that they appear reasonably close to logarithmic. "Audio" potentiometers are hard to find and expensive and if it really is a true logarithmic pot then it is even more rare and expensive.

At the time of designing the QCX I really thought that the 5KB pot supplied was a log pot and I didn't measure it. But I was wrong and it is actually a Linear characteristic type. I should have known from the fact it wasn't unreasonably expensive, that the chosen potentiometer wasn't logarithmic ;-)

However, all is not lost. It turns out that if you put a resistor in parallel between the wiper and ground, the characteristic of the combination can be made to closely approximate logarithmic. The value of the fixed resistor determines the extent of the deviation from linear characteristic. I have seen recommendations that the fixed resistor should be 1/4 or 1/5 of the value of the potentiometer value (in the QCX case, the potentiometer is 5K so a fixed resistor of 1K would match these suggested values). 

Now look at the op-amp stage following the volume control, which is IC10b. This is configured as an inverting amplifier with a gain of 120. The input resistor R37 is 1K and this is also the effective input resistance of this amplifier. 

What this means is that by good fortune, the Linear track 5K potentiometer is loaded by 1K, which is to say, it already exactly meets the R/5 recommendation (you can find this mentioned on some audio forums). So despite having a Linear volume pot, the overall effect (combined with the 1K load of the following stage) results in a characteristic which is closer to a logarithmic curve than to a linear straight line. 

Therefore the linear potentiometer is not the reason for you only using the lower 10% of the potentiometers adjustment range. 

The real reason is that the QCX receiver has a low noise front end, that gives it good sensitivity, and the overall gain of the receiver is a little on the high side. 

Ok the other hand... the R/5 recommendation that is suggested often isn't actually closest to a logarithmic trace. For that, you need R/10. This could be achieved by adding a 1K resistor from the volume control wiper (center connection) to ground. Then this 1K combined with the 1K input resistance of the op-amp that follows, would result in an 0.5K load on the wiper, which is 1/10th the value of the potentiometer track resistance. 

So in conclusion there are two possible minor modifications that could be considered:

1) if you feel that the QCX at maximum volume is ear-splittingly loud and you would never ever use that much gain... then you need to reduce the gain of the QCX receiver. The easiest and best way to do this is to reduce the value of R38 (120K). You could half it, by taking on another 120K in parallel on the bottom side of the board. Or you could replace R38 with a lower value such as 47K or 56K. Or less! If you half the value of R38 that's like removing to the top 50% of the gain of volume control. 

2) if you are a real perfectionist and want to be as close as possible to a real logarithmic volume control function, then solder a 1K fixed resistor between the volume control potentiometer wiper and ground. 

73 Hans G0UPL 

Re: #qcx Linear vs Logarithmic: a note on the QCX volume control #qcx

Paul Galburt - K2AYZ
 

Thanks, Hans for an excellent explanation. Funny comment "all my life" about the A/B convention. I think I first understood about Log vs. Linear at the age of perhaps 11 or 12 yrs. About the same time I wondered how VA was different from Watts. 

BTW, I was in the audio business for a long time and considered "A" as log taper (as in audio) and "B" as, well, the other kind. We had some Alps Stereo Master dual pots that were specified to be within 1 dB from 0 to about -72 db, but relatively large and expensive, as you said. These were build with multiple internal trimmed load resistors on a sort of linear track. Spec sheets and testing are your friends.

73,

Paul K2AYZ

A few 20m sigs copied by the modified QCX-17 over the last 24 hrs

n4qa at_hotmail.com
 

This is just too easy ! You know, I'd bet that a feller could use WSJT-X to decode FT8 sigs using only a radio receiver comprising a diode detector and a weak xtal osc rf bfo !
But it *is* nice that the modified QCX-17 will do the trick on 80-10m...maybe other bands too !
It does a dandy job transmitting CW as well!
72 / 73,
Bill, N4QA

Re: ProgRock won't program correctly

Alan G4ZFQ
 

Re: ProgRock won't program correctly

geoff M0ORE
 

BEWARE...ProgRock does not using RS232 voltage levels. Proper RS232 has 12 volt logic, ProgRock has 5 volt logic. Hence the suggestion to use the Arduino. The Sparkfun adaptor supports 5 volt logic but others may not.

Geoff

On 19/08/2019 01:29, Robin Midgett wrote:
I found that the USB to serial adapter from SparkFun was the ticket to easy programming on the ProgRock. Any terminal program will provide the communications.
Thanks,
Robin Midgett K4IDC


On Sun, Aug 18, 2019 at 6:31 PM Floyd Hollister <fhh11@...> wrote:
Thanks to Bruce, Geoff and Alan.  I appreciate you counsel.  I will dig out an Arduino and see where that leads me.

When I either solve the problem or surrender and build another, I will let the forum know the resolution.

Floyd

Re: 10 watt linear amp problems

chrislacey21
 

Rod
I hope your rebuild goes well and thanks for your comments on my problem about heat being my main issue. I have an IR thermometer and used it carefully to see temp rises in all transformers.

Alison
Many thanks for your expertise and suggestions on probable causes
Firstly R216 and R217 did run hot - very hot. I have replaced R217 twice when it burned out. I thought that reducing the input would help and it did. I also replaced the LPF (on the Linear) with  carefully measured inductors in case that was the problem.
If I use an LPF on the U3S output the power measured on an AA5TB Wattmeter is hardly measureable so I need to investigate the output FET's on the U3S and again measure the LPF values.
My measuring equipment is not sufficient for this work at 50MHz. My scope is an old Telequipment D34 - a 20MHz scope, a digital multimeter and an Oskerblock SWR-200B for power measurements. But now I have some clues to work with. Thanks.
You mentioned some heating effects of trying to drive the Linear with a square wave input. And you were right.
Now with the U3S fitted with an LPF and the linear with 13.6v supply the current drawn by the linear was 0.41A for a measured 100mW output into a dummy load. At the same time I used my IR thermometer to check for hotspots - T204 51C;  T203 61C;  T202 56C;  L201 42C;  T201 36C. 
I don't understand why this should happen as the output from the U3S should have been a sine wave and the supply 13.6v. I need to test at a frequency that my scope can measure to check again. As I had removed and rewound T201, T202 and L201 there is inevitably some damage to the PCB so it is possible that despite continuity checks something is amiss. I am also wondering about the hours of transmission at full power using the U3S and linear on a frame of 10 for WSPR could have damaged the input Q203 and Q204 which I haven't touched yet.
So I have more testing and checking to do - many thanks for your help with this problem.
73
Chris G0IMX

Re: Irony #qcx

Paul AI4EE
 

Some people cross-stitch, some scrapbook, some collect funny-looking rocks or pull tabs. Hobbies don't have to have a reason. In fact a hobby with a reason can become an obsession. Amateur radio is so broad we can have many niches to fill for no reason other than we like a nice, well-filled niche.


On 8/19/2019 12:01 AM, Old Dog wrote:
If a young one asked me why I do CW I would say simply because I can and I enjoy it.  Barring the solar flare that pushes us back to the stone age or the EMP from some angry neighbor;  CW is going to go the way of the dinosaur, the dodo, and the Tasmanian Tiger.  It is as inevitable as drought in Arizona.

On the other hand if we are hit by that solar flare or that EMP CW will be the first radio technology that gets turned back on simply because the technology is the easiest to duplicate with a sharp rock and a sewing needle =).

It is a skill to do between your ears what John Q needs to do on his computer and that is as good as any reason to practice CW, I think.

73 Guys and by the way.  I have revised the QCX case I print.  Here is a link to the video:

w4mHz

Virus-free. www.avast.com

Re: Irony #qcx

Old Dog
 

If a young one asked me why I do CW I would say simply because I can and I enjoy it.  Barring the solar flare that pushes us back to the stone age or the EMP from some angry neighbor;  CW is going to go the way of the dinosaur, the dodo, and the Tasmanian Tiger.  It is as inevitable as drought in Arizona.

On the other hand if we are hit by that solar flare or that EMP CW will be the first radio technology that gets turned back on simply because the technology is the easiest to duplicate with a sharp rock and a sewing needle =).

It is a skill to do between your ears what John Q needs to do on his computer and that is as good as any reason to practice CW, I think.

73 Guys and by the way.  I have revised the QCX case I print.  Here is a link to the video:

w4mHz

Re: ProgRock won't program correctly

Robin Midgett
 

I found that the USB to serial adapter from SparkFun was the ticket to easy programming on the ProgRock. Any terminal program will provide the communications.
Thanks,
Robin Midgett K4IDC


On Sun, Aug 18, 2019 at 6:31 PM Floyd Hollister <fhh11@...> wrote:
Thanks to Bruce, Geoff and Alan.  I appreciate you counsel.  I will dig out an Arduino and see where that leads me.

When I either solve the problem or surrender and build another, I will let the forum know the resolution.

Floyd

Re: ProgRock won't program correctly

Floyd Hollister <fhh11@...>
 

Thanks to Bruce, Geoff and Alan.  I appreciate you counsel.  I will dig out an Arduino and see where that leads me.

When I either solve the problem or surrender and build another, I will let the forum know the resolution.

Floyd

Concerning C5 on the U3S #mods #pa #u3s

Nik
 

In the instructions for connecting the U3S to the 5W PA, C5 is removed to break the circuit to allow the RF to be routed out to the 5W PA and back into the Band Pass Filter circuit and then out through the antenna socket to the antenna or dummy load. 

I've noticed that this cap decouples the DC from the BS170, and when removed, the output has the DC drive voltage of the BS170 present.  Could this cause problems (Using an RD16HHF in place of the BS170 and feeding it 13.8V heats my little 12W dummy load up a lot, when in circuit.  To combat this I've put the 100nf 50V MLCC cap back in the circuit between the centre of the coaxial feed from the BPF board to the BNC socket.  This also means in the event of  a short in the antenna feed the unit does not clamp the input power feed.  If my calculations are correct, 50V is good up to 10W at 50 Ohms.  So possibly a 100V cap would give a better margin for error.

OK, here are my questions for the experts among us (pin your ears back Allison I'd value your opinions greatly);

1.  Does this voltage pose any threat to the 5W PA if not blocked?

2.  Will it cause any problems I would need to fix if I put my replacement RD16HHF1 or an RD06HHF1 in circuit to drive the 5W PA?

TIA

Nik M1DOX.

P.S. I've also discovered that around 6W of RF at 7MHz or thereabouts put back into the BPF feed seems to screw up WSPR DT times.  The timing seems to go off by anything up to 15 seconds, Stretching them to over 2 minutes and thus making them invalid.  This needs more investigation.

Re: 10 watt linear amp problems

ajparent1/KB1GMX
 

Rod,

Yes, 180khz the amp is way out of the useful range.  As is the ferrite is showing pain
below 1mhz.  Going to 73 and bigger helps but the whole winding scheme then
needs to be redone.

However at 180 khz the larger IRF series fets are a better choice and would be more robust.
However the 20DB gain requirement can be met but with great care and the driver has to
be stable as well.

As to built by less experienced people bad idea, better to have assembled in volume.
then again there is a lot more hardware to MRI systems.

Allison

Re: LightAPRS Tracker

Mustafa Tan
 

Yes. Either we should add a display or use a new CPU such as ESP32 which has Bluetooth.


On Mon, Aug 19, 2019 at 12:23 AM Tait VK1FTRA <tait.leaney@...> wrote:
Not necessarily, a bluetooth interface may be suitable to work with aprsdroid. 

I have seen the picoaprs which does have an oled. Were you going to suggest that?



Re: #40m #TVI #DTV #U3S #WSPR Freeview Interference #40m #tvi #dtv #u3s #wspr

Alan de G1FXB
 

In days of olde....
(pre Astra? / SKY) analogue satellite receivers
, a common sets own Intermediate Frequency was 70Mhz
maybe freeview boxes use similar?


Alan


On 16/08/2019 06:40, KEN G4APB via Groups.Io wrote:
I recently bought a bt youview box and kept getting that problem and returned it for a refund as i thought it was faulty, I realised now that I was running my U3S on 4m (70mhz) ?= 7mhz x 10?? at the time. I wonder now if the youview box has a particular problem with this freq.

73 Ken g4apb?

-- 
Light travels faster than sound this is why 
some people appear bright until you hear them

Re: ProgRock won't program correctly

Alan de G1FXB
 

As you have substituted the "chip" and DIP switch & the synth daughter board it doesn't leave much else.....

I read the manual instructions as depressing the programming enter button as " do it positively ",
but not for an artificially long period of time else you will clash with the timeout and receive the solid light of death.....
Also you need to ensure the led is extinguished before programming serial bits. See pages 4 &5 of the op's manual
As others indicate, the serial access option make programming a lot more painless.

If all else fails, as sometimes you receive the "all OK" ACK pother times you don't the microprocessors really appreciate a clean power supply.


Alan


On 18/08/2019 16:39, Floyd Hollister wrote:
I have a ProgRock with program chip pr 1.02. The 1pps pin is grounded,? At first it worked very well and I was able to program it correctly at my desired frequency of 151.700.? Then, it would not program correctly.? By this I mean that attempts to program it to 151.700 MHz would result in what appeared to be random outputs around 277 MHz.? I then used 010enter to return the unit to its factory settings.? This produced the expected 10 MHz output but attempts to change this resulted in outputs around the clock frequency of 27 MHz.? I then replaced the Si 5351A synthesizer board another one and? I had with the same results.? This suggested that there was a problem with the ProgRock motherboard or the pr 1.02 programming chip.? Replacing the pr 1.02 chip with another led to the same result.? ?

I observe that when I power up the ProgRock, I? get the four flashes indicating successful communications with the synthesizer daughter board.?When I then try to enter the frequency using the 4-bit slide switch and pushbutton,? I some times get the desired flashing red response other times I get just solid red light as long as I hold down the pushbutton.? In this manner programming seems to be an unsuccessful random process.? I changed to 4-bit switch with the same result.? I suspect some problem with the debouncing circuit. As mentioned above, the? 1 pps pin? has been grounded throughout the above experience. And I am careful to press the pushbutton solidly for about one second. The ProgRock register values may be corrupted but I would expect the 010enter factory reset to set them correctly. Since I am using the slide switch to program I canno look at the register contenets.

Next step will be to build another ProgRock motherboard unless someone can suggest another approach to solving the problem.? Any help would be much appreciated.

Floyd

-- 
Light travels faster than sound this is why 
some people appear bright until you hear them

Re: 10 watt linear amp problems

Alan de G1FXB
 

Chris,
It's perhaps better if you start a fresh thread for your problems as it's a different, band you are utilising & different symptoms as your build initially gave the full 10W on 6Mtrs.

A few other builders have noted that extended periods of transmissions have resulted in R216 & R217 burning up, maybe worth a nose test or getting the meter out?
I don't think there was an explanation beyond replace it with a higher wattage.

I don't know the duty cycle you are envisaging, perhaps double check the manual description 100% duty cycle is only for 20 minutes, not anything close to 2 minute WSPR cycles 24/7 ?
In normal use, the heatsink is not expected to operate significantly above ambient temperature.


Alan

On 18/08/2019 14:11, chrislacey21 via Groups.Io wrote:
Hi Rod,
I am interested because I am also having problems with my Linear kit. I am trying to feed the output from my U3S at 50 MHz WSPR into the linear. At first I got a full 10W out - after I had increased the supply to 20v and about 1.8A (maybe not enough drive) but after a few days the output dropped from 10W to 8W and then reducing over the 2 minute transmission to 6W. After checking many connections and changing the LPF on the output of the linear there were some small improvements but then the output dropped still further to less than 1W at which point I decided to check the components in the linear.
After testing supply voltages to the FETs and bias I removed first the IRF510s and tested them - both OK. Then I removed T201, L201 and T202. I sympathise with your comment about removing them! After rewinding them and doing all the continuity checks I am at the point of removing Q203 &Q204. Tested in circuit at 12v supply and bias to the IRF510s turned off I measured source 0.06v , gate 2.64v and drain 12v. No apparent problems there.
The only other comments I can make are that the symptoms here for the low power seem consistent with over-heating. As power decreases so does the current which may or may not be a clue. The supplied heatsink got hot but soon cooled off after every transmission. Apart from the heat from the IRF510s nothing else seems to be overheating. My only other idea is the input from the U3S - it's very low output at this frequency and I had to remove the U3S LPF and use the square wave output to get enough drive for the linear. I have measured the U3S output which is similar to when I first started but I cannot read this accuirately.
If it helps my tests of the IRF510s in circuit were - Source- 0v Gate 3.87v and 4.18v and Drain - 12v . But my linear is not working properly either!
Does any of this sound familiar?
I hope someone else can suggest possible reasons for the low output to help both of us.
73
Chris G0IMX

-- 
Light travels faster than sound this is why 
some people appear bright until you hear them

Re: LightAPRS Tracker

Tait VK1HAB
 

Not necessarily, a bluetooth interface may be suitable to work with aprsdroid. 

I have seen the picoaprs which does have an oled. Were you going to suggest that?

Re: 10 watt linear amp problems

Rod Kreuter
 

Allison,

You are absolutely correct.

I found what was most likely my problem but it is of no importance.

Perhaps if I give you some background my purpose will become more apparent.

I don't need this amplifier and will not use it. I saw it and thought it could fill a gap.

I was tasked with finding an amplifier with about 20 Db of gain for 180 KHz that would produce 6 to 10 watts pulsed at a low duty cycle.Low cost was a must. I decided that this kit would provide two things. Most of the parts and a PCB.

Naturally the transformer material would have to be replaced so I ordered a bunch of 73 material for the cores. Also some 77 and 75 material. I have all of the parts here and I got a prototype (dead bug on ground plane)  running before the kits actually showed up. Fifteen watts with no problem.

You see we are planning to send many (100's) of these kits to Africa where they will be used in an MRI system that will be used to test infants for hydyocephalus. The boards will have to be built by people with very little experience. These boards will not work for this application.

Thanks for your insight.

73

Rod





Re: LightAPRS Tracker

Mustafa Tan
 

Hi Tait,

Unfortunately not :( But if it was, would you need an OLED display on the module ?

TA2MUN

On Sun, Aug 18, 2019 at 11:10 AM Tait VK1FTRA <tait.leaney@...> wrote:
Based on the Dorji Transceiver, it the LightAPRS capable of receiving as well as transmitting?