Date   

Re: 50 Watt Amplifier for 80M. Minor error in assembly manual.

Glenn VE9GJ
 

Hi Steve
I see I am not the only campground kit builder! On our 2 weeks at a campground earlier this month I built a 40m mini and a U3S with GPS and 5 band relay kit. I put a photo of the U3s on my qrz page. I certainly get lots of stares and questions from passing campers!
I have been building kits at picnic tables for a few years now.

73
Glenn VE9GJ


On July 24, 2021 8:36:04 PM ADT, Steve Greffe - VE3SGV <sgreffe@...> wrote:
Just a heads up people. Not a big deal but save yourselves a bit of a headache. On page 13 of the assembly manual we're instructed to cut a 34cm length of .6mm wire to wind L6. For 80M we need 27 turns. 34cm of wire will only get you 22 turns. Not enough for L6 and not enough even for the 24 turns needed for L4 and L7. 
50cm is enough for L6 for 27 turns.
45cm is enough for L4 and L7's 24 turns.
There is still just enough .6mm wire left over to wind the bifilar and trifilar transformers.
I was able to salvage and straighten my initial 34cm piece of wire to use for the bifilar wind. After cutting 50cm and two 45cm pieces, I cut the leftover into 4 equal pieces. They were about 35cm each. 

(I'm building this amp on a picnic table while camping and I have very few other bits and pieces with me other than the kit contents themselves hi hi)

Disaster averted!

Hope this helps others.

73
Steve VE3SGV 


Re: Fried my qcx+ finals...

wa8yan.radio
 

Hi Harry.... I'm pretty new here too but have been here long enough to know that this is a great group of guys and gals from all over the world.  The problems that have been solved here are legendary HI HI. ANYHOW WELCOME TO THE GROUP
73 Phil WA8YAN



Sent from my Verizon, Samsung Galaxy smartphone


-------- Original message --------
From: "Harry Latterman via groups.io" <harrylatterman@...>
Date: 7/25/21 12:42 PM (GMT-05:00)
To: QRPLabs@groups.io
Subject: Re: [QRPLabs] Fried my qcx+ finals...

Nice write up and lots of true key points.  I am new here,  Very new.  My mini was shipped from Turkey yesterday and I just joined the group. It seem just like a few other groups, like the Xeigu G90 group.io, there are a few people who kind of spoil the pot. Most people, like myself, join to learn and if possible help others since many are new to ham radio.  I am not new. 56 yrs as a ham and still learning and having fun. I, like you, suspect that the vast majority of radio owners, here and other groups, don't have problems or resolve them without making a on line issue about what is going on. In the case of the OCX kits, I believe that many are not built or only part way, thus we don't here from them. Those who do have issues will naturally come to the group(s) for help.  That is what they should be doing and those who have issue with that need to move on and shut up and not put them down.  The only dumb question is the one not asked.  Being bullied by some self-righteous jerk does not help and makes the group look bad. I am hoping that this will be a good group to belong too. I am looking forward to my 20 meter mini and learning how it works, making contacts and doing WSPR to test out all sorts of QRP compromise antennas for portable use.

Thank you for the posting.

73 Harry K7ZOV


Re: QCX-mini simple audio limiter #qcxmini

 

Gunnar

Very nice idea and simple. I like simple! Need to order some of those diodes …
--
73, Bernie, VE3FWF
(most typos in this message have been generated by highly sophisticated auto-correction software)


Re: Fried my qcx+ finals...

Harry Latterman
 

Actually John you are partly correct about 100% duty cycle and modern radios. Most Yeasu radios are not happy with 100% duty cycle. Most Icom have no issue with 100% duty cycle. I am running my IC-7300 for many hours running FT8 and RTTY at 100 watts and the radio barely gets warm. Same was true with my IC-756PORII and K3/100.  All were designed to take the heat and get rid of it. I have run RTTY, Olivia, PSK31/63, JT-65 and now FT8 flat out and never blew a final nor had heating problem... With ICOM.. With the Yeasu F-450, FT-991A, and even the FTdx5000MPL beast you had to cut the power back on or have problems.  The OCX line does not have even close to safe heatsinking, thus they will be prone to final failure it not taken care of with low SWR and keeping high duty cycles low.

I am new here and my mini was sent from Turkey yesterday and I should see it by Friday. It was built factory built one and I know for a fact that Hans tested it.  With only a screw and washer and I think with no silicon heat sink added heating will always be a problem with the mini when doing WSPR. I plan on treating the radio as though it could blow at anytime. I do plan on doing a lot of WSPR for QRP testing, so 1 to 2 watts will be all I will ever use... I also plan on keeping the final transistors in stock in my radio shack, just in case.

73 Harry K7ZOV


Re: Fried my qcx+ finals...

Harry Latterman
 

Nice write up and lots of true key points.  I am new here,  Very new.  My mini was shipped from Turkey yesterday and I just joined the group. It seem just like a few other groups, like the Xeigu G90 group.io, there are a few people who kind of spoil the pot. Most people, like myself, join to learn and if possible help others since many are new to ham radio.  I am not new. 56 yrs as a ham and still learning and having fun. I, like you, suspect that the vast majority of radio owners, here and other groups, don't have problems or resolve them without making a on line issue about what is going on. In the case of the OCX kits, I believe that many are not built or only part way, thus we don't here from them. Those who do have issues will naturally come to the group(s) for help.  That is what they should be doing and those who have issue with that need to move on and shut up and not put them down.  The only dumb question is the one not asked.  Being bullied by some self-righteous jerk does not help and makes the group look bad. I am hoping that this will be a good group to belong too. I am looking forward to my 20 meter mini and learning how it works, making contacts and doing WSPR to test out all sorts of QRP compromise antennas for portable use.

Thank you for the posting.

73 Harry K7ZOV


Re: Fried my qcx+ finals...

John Kirby
 

p.s. 

Yes I run QCX WSPR and QCX BEACON by reducing battery Voltage

A variable power supply works best to reduce output power but more expense than several diodes (a drop of apx 1.3 V each) in series with Hans reverse polarity protection diode 

N3AAZ


Re: Fried my qcx+ finals...

John Kirby
 

 WSPR, RTTY, PSK31 ...etc...  are 100% duty cycle key down modes

Run any modern CW / SSB transmitter at full output key down for several minutes and it will melt down too. The cooling system is not designed for that much heat dissipation

Ever wonder why off the shelf 100 Watt SSB radios only OUT PUT 25 Watts AM Mode?   AM is 100% duty cycle key down !
 
Some manuals caution set power output at 50% OR less  while running long period duty cycle modes

Remember too ALC will not save a melt down, ALC has nothing to do with long duty cycle key down mode

72 73
John
N3AAZ


QCX Challenge - July 2021

ON7DQ Luc
 

Hi All,

Remember : tomorrow is the QCX Challenge, on the regular bands.

See http://www.qrp-labs.com/party.html

Not sure if I will make it for the 1300 session, but surely I will be QRV at 1900.

73 es GL,
Luc ON7DQ


Re: New QCX Mini 17M completed - expected rx sensitivity (minimum detectable signal level)?

Rob Giuliano
 

I agree with David (K8WPE).
With a little work, you can usually find free, used 12V backup batteries from businesses that are required to change them on a time basis.
Hospitals are probably the most common, but some business which require emergency lighting also use that practice.
My favorites were the 24 volt ones which were typically 2x 12v batteries in series with a fuse between them.
I am not ure why the fuse was between them, but when reqired in parallel, I had a 14 Ah battery or 2x 7 Ah, if you could get them apart.

A friend was close with a manager at a "Battery Plus" store.  He would bring home various 12v betteries for us, and take them back if they didn't work out.


Re: Fried my qcx+ finals...

Armin, DJ2AG
 

From „Operating Instructions -  6.7 WSPR power“

“The third and final parameter encoded into the WSPR message is the transmitter power, defined in dBm. Note that this parameter is manually edited here and is encoded into the WSPR message. It does NOT indicate a measured power which is actually transmitted. This is a common misconception. It only indicates what number the operator configured for the WSPR message encoding.“

73, Armin


Re: Receiver front-end filter #rcvr

Roelof Bakker
 

Hello Ton,

Varicaps can be used, but show a much lower Q than a normal capacitor.
In the previous century I have measured the Q of the BB112, a 20 - 500 pF varicap.
It varied from 50 (400 pF) to 70 (30 pF).

I build a pre-selector using a Wes Hayward, W7ZOI double Peak Low Pass Filter topology.
The beauty of this topology is that it offers very little loss variation over a 1 to 4
frequency range, typical 2 dB.

Using BB-112 varicaps to tune a 10 - 30 MHz pre-selector, the loss was:

MHz loss dB
=============
28 3 (3)
25 3 (4)
21 3 (5)
18 4 (6)
14 5 (8)
10 8

The figures between brackets apply to using two BB-112's back to back instead of a single
BB-112.

73,
Roelof, pa0rdt


Re: Fried my qcx+ finals...

Albert Tatlock's Greatest Hits - Vol 1
 

On Sun, Jul 25, 2021 at 04:37 AM, VK5EEE wrote:
QRP rig or QRO rig at more than 1W and should surely only be using 100mW or less, and this is easily achieved in the WSPR settings menu of the QCX.

No it can't.


Re: QCX-mini simple audio limiter #qcxmini

VE3VXO
 

Yes I tried similar but put the diodes in the feedback path of the first stage audio amp along with a series resistor which helps the op-amp have a graceful transition into clipping.  Simple is good!


Re: Fried my qcx+ finals...

Alan G4ZFQ
 


As mentioned earlier, the rig still seems to output about 200mW, is that consistent with just 1 or 2 BS170s that have faied?
Yannig,

It is possible but there are too many unknowns to be sure.
 How much of I risk do I take from replacing the 3 BS170s and ordering a MPS751 to have one in advance in cases it fails ?
Again, difficult. It should not cause damage.
I quite like the idea of sockets, especially the idea of having a few spare BS170s handy in case it happens again, just not too sure about the implementation, can you still squish the transistors against the PCB so that it acts as a heat sink?

 Clamping the flat surface to a strip of metal has been used by some. In normal CW use it should not be necessary, for WSPR some use a lower voltage

73 Alan G4ZFQ


Re: Fried my qcx+ finals...

Yannig - F4IUJ
 

On Sun, Jul 25, 2021 at 12:36 PM, VK5EEE wrote:
interesting as i was going to add but then decided not to as thought it would be off topic -- that i need to get hold of one myself as recommended by some others in this group before i try to debug another QCX which likely got static damage. it would be very nice to have even 10% of the knowledge of some of the folks in this group regarding electronics and radio circuitry, but to be honest, i am not sure i want to start learning too much now, but never say never! One has to find something to do as time goes on, if time permits, and it may as well be something useful.  At first i was thinking it wouldn't be useful to anyone except myself, but then it's dawning on me that being able to fix such things could also be helpful to others in future, and i also know some young unemmployed folks that otherwise are too busy smoking weed but have some interest in this sort of thing. This is a hobby too which crosses age gaps. 
 
Congratulations on your English, i wish my French was even half as good!  i do enjoy a french CW QSO though, honestly, to me CW sounds better in french, nice as the language sounds too, and after all, the development of the Gerke Code probably had some french considerations. Along with the di-dah-dah-di-dah and di-di-dah-di-dit etc :)  
 
Are you buying your own oscilloscope or using a "big one"? i'm aiming to purchase one of those semi-oscilloscopes that however are very helpful in analysing QCX and other rigs. 
 
77 de LouEEE
 
My oscilloscope is an old one that was used by French schools/universities during the 1990s, it is not up to modern standards but I still remember how to use it from when i was a student and I bought it from the grand sum of 40€ from an older ham.

As for my English i cheated as I lived and worked for 10 years in the UK. My daughter who was born there still find my accent embarassing ;-)

73

Yannig - F4IUJ


Re: Fried my qcx+ finals...

 

interesting as i was going to add but then decided not to as thought it would be off topic -- that i need to get hold of one myself as recommended by some others in this group before i try to debug another QCX which likely got static damage. it would be very nice to have even 10% of the knowledge of some of the folks in this group regarding electronics and radio circuitry, but to be honest, i am not sure i want to start learning too much now, but never say never! One has to find something to do as time goes on, if time permits, and it may as well be something useful.  At first i was thinking it wouldn't be useful to anyone except myself, but then it's dawning on me that being able to fix such things could also be helpful to others in future, and i also know some young unemmployed folks that otherwise are too busy smoking weed but have some interest in this sort of thing. This is a hobby too which crosses age gaps. 

Congratulations on your English, i wish my French was even half as good!  i do enjoy a french CW QSO though, honestly, to me CW sounds better in french, nice as the language sounds too, and after all, the development of the Gerke Code probably had some french considerations. Along with the di-dah-dah-di-dah and di-di-dah-di-dit etc :)  

Are you buying your own oscilloscope or using a "big one"? i'm aiming to purchase one of those semi-oscilloscopes that however are very helpful in analysing QCX and other rigs. 

77 de LouEEE

On 25 Jul 2021, at 10:28, Yannig - F4IUJ via groups.io <yannig.robert@...> wrote:

i forgot to add that tomorrow, I will have access to an oscilloscope, I could do some extra measures (for the "science" or because it helps the diagnostic)

73

Yannig


--
Love 30m and CW?
http://www.30cw.net


Re: Fried my qcx+ finals...

Yannig - F4IUJ
 

i forgot to add that tomorrow, I will have access to an oscilloscope, I could do some extra measures (for the "science" or because it helps the diagnostic)

73

Yannig


Re: Fried my qcx+ finals...

Yannig - F4IUJ
 

On Sun, Jul 25, 2021 at 09:00 AM, Alan G4ZFQ wrote:
Yannig,

The initial readings seem to show the PA is working properly but I'm not sure what causes the rapid drop.
Lou's guess may be right, one or more BS170s have failed. One BS170 is in there trying to work.

I do not advise replacing components randomly one by one, depending on the fault you could destroy the new components one by one.

Neither do I recommend using any of the original components. One may test good but have some internal damage which soon causes failure.
Not so important in this rig but it is best if the BS170s all come from the same batch.

Others, like Peter have suggested sockets for these components. It is your choice, some have cut the legs of the old devices and soldered to the remainder.

First, in case of a coincidence look carefully at the connections to C29, resolder them. Possibly C29 is faulty.
If nothing is found then component replacement is the next step.

At the moment Q6 seems to be working correctly but my suggestion is to replace it as well in case it fails in the future.

73 Alan G4ZFQ
Thank you Alan for the precise answer.

As mentioned earlier, the rig still seems to output about 200mW, is that consistent with just 1 or 2 BS170s that have faied?

I can source some BS170s locally but i will have to order the MPS 751 from far away. How much of I risk do I take from replacing the 3 BS170s and ordering a MPS751 to have one in advance in cases it fails ? Does this one tend to fail with collateral damages?

I quite like the idea of sockets, especially the idea of having a few spare BS170s handy in case it happens again, just not too sure about the implementation, can you still squish the transistors against the PCB so that it acts as a heat sink?

73

Yannig - F4IUJ


Re: Fried my qcx+ finals...

 

Thank you too for this Alan i learned many things from it -- some of which i'd actually been wondering about, such as the wisdom of not replacing them all together. Glad you mentioned that and the other points.

Hoping for good news from you Yannig.

77 de LouEEE

PS i wonder if you would happen to know on the BS170 out of circuit when i check resistance across legs (don't ask me which ones at this point) on good ones i get 80 k Ohms, and on one removed from a faulty (blown) set, got 50 k Ohms on one of them, i presume that would indicate it is not ok so i chucked it out. i've got enough new ones from a same batch now to replace.

On 25 Jul 2021, at 07:00, Alan G4ZFQ <alan4alan@gmail.com> wrote:


Continuity in LPF : OK (very little resistance across the 3 Toroids in serie)
Tension measurements from the ground taken at the top right corner of the PCB while the 50Ohms load is attached and I made all measures twice, one with the TRX in receiver mode and one while keying the receiver :
1. BS 170
* Source always 0V
* Gate : RX : 0V / TX : 2.57V
* Drain : RX : 0V / TX : my multimeter refuses to measure it (no
Oscilloscope), after keying off I see a very high tension (saw
70V once) then it goes down quickly to a few volts
2. MPS 751
* Emitter : RX : 11.89V / TX : 11.5V
* Base : RX : 11.89V / TX : 10.7V
* Collector : RX : 0V (after some time) / TX : 11.2V then decreases
Yannig,

The initial readings seem to show the PA is working properly but I'm not sure what causes the rapid drop.
Lou's guess may be right, one or more BS170s have failed. One BS170 is in there trying to work.

I do not advise replacing components randomly one by one, depending on the fault you could destroy the new components one by one.

Neither do I recommend using any of the original components. One may test good but have some internal damage which soon causes failure.
Not so important in this rig but it is best if the BS170s all come from the same batch.

Others, like Peter have suggested sockets for these components. It is your choice, some have cut the legs of the old devices and soldered to the remainder.

First, in case of a coincidence look carefully at the connections to C29, resolder them. Possibly C29 is faulty.
If nothing is found then component replacement is the next step.

At the moment Q6 seems to be working correctly but my suggestion is to replace it as well in case it fails in the future.

73 Alan G4ZFQ




--
Love 30m and CW?
http://www.30cw.net


Re: New QCX Mini 17M completed - expected rx sensitivity (minimum detectable signal level)?

David Wilcox K8WPE
 

With QRP I don’t even think of AC power supplies. 12 - 14 v batteries are so easily available and last so long that is all I use. Recharge occasionally. I get free 12 v 7 amp gel cells from the hospital when they change them out on a regular basis. They have to pay the recycler to take them so are very happy to give them away to hams and other interested parties.  Someday I will hook them up to my solar panel and have automatic charging. Maybe the 5th Tuesday of next month.  

Most wall warts are cheap and a pain and the lap top ones that are good are too high a voltage.

Dave K8WPE

David J. Wilcox’s iPad

On Jul 25, 2021, at 4:06 AM, tony.volpe.1951@... wrote:

Just to second Jim's remark; when I first fired up my original Classic QCX, I used a wall wart I had lying around. Everything worked like a charm, but people were calling me and I could barely read them. My first few qsos I was getting 559 reports from people 500 miles away on forty and I was struggling to hear them under the hash.I tried other switching supplies, from old computers, with more or less similar results and soon bought a traditional type, small, linear power supply of suitable output power for about £45. What a difference. It was like a different radio, I could easily read the faintest signals.

G0BZB 
Tony

9541 - 9560 of 77832