Re: FedEx invoice for import to UK
"I never could get the hang of Thursdays¡± - lead character in "the hitchhikers guide to the Galaxy¡±
73 John F5VLF
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Re: #qmx Antenna Tuner Can Kill PAs
#qmx
Like Evan, I too have been unable to create a 60V high voltage failure
through high SWR, either in LTS simulation with a huge range of loads,
or by accidentally transmitting into an open circuit. I second all he
says, and reflect on Hans' affirming tests here as well.
I want to add though that low impedance loads are the bane of this PA.
A low-Z/High SWR condition maximizes the current in the BS170
transistors, maximizing their power dissipation, and also in the spike
generating inductor (L14 in QDX), maximizing the V= LdI/dt kick-back
voltage. It is the *Nightmare Condition* for QDX, without question.
Sadly, that conflates two causes of failure and creates much confusion
amongst the users.
I strongly recommend the L14 commutating diode as a means of taking
LdI/dt stress off the PA.
JZ KJ4A
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On Wed, Sep 13, 2023 at 3:05?PM Evan Hand <elhandjr@...> wrote:
John Zbrozek started the development of an LTSpice IV model of the QDX PA that he and I expanded to test a theory on what happens when the transmitter is turned off at the end of an FT8 cycle. The model and subsequent bench testing verified a voltage spike at the end exceeding 60 volts. I measured over 100 volts for a very short period on my Rev 1 QDX. This can be eliminated with a "commutating" diode to dissipate the built-up magnetic field. Subsequent tests indicate that the single diode does eliminate the spike.
Because of the minimal duration and normal variance on devices compared to specifications, the likelihood of your QDX suffering from this problem is minor. There are many QDX in service that have not exhibited the failure. The ones that are noticed are the ones that have failed. Consider that thousands of these radios are in operation, and we are seeing tens reported with a failure that could be power-related or severe operating conditions.
For myself, I have installed the diode on my QDX. This is not needed for the QMX, as the key shaping circuit removes the sudden cutoff of the PA supply. The QMX would not have the issue.
I have done some simulations of short and open loads on my most recent model of the QDX PA. I can not get an overvoltage with either of those conditions. This leads me to believe that the Zeners to protect the BS170s are most likely unnecessary. That is not to say that a high SWR would not cause a failure. It indicates that it is likely not voltage but a power or current-related issue. I have not looked into that failure mode. Since a voltage failure does not seem probable, adding the Zeners is not a fix for the problem. The Zeners would not hurt, but I doubt it will add much protection.
It is still good practice to check the antenna for high SWR before the first transmission in a session. I would also avoid applying full power to an ATU connected to a QDX.
A request to Hans would be a lower power tune mode for the QMX that could be done in software with the key shaping circuit already part of the QMX. This would need a hardware mod to work on the QDX.
The above are my observations and conclusions. Please let me know if any data goes against any of the above. I am ALWAYS open to constructive feedback. It is one of the methods I use to learn.
73
Evan
AC9TU
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Vacuum-tube final for QRP transmitters?
Hello--
Please note that I currently do NOT have a dog in any of the current digital dogfights
which are consuming quantities of various MOSFETs used as final amplifiers in
QRP equipment.
Has anyone considered experimenting with such vintage tubes as the 1T4, 3V4,
1U5, 1LN5, 1A5-GT ?. These are available in the $5.00-$10.00 NOS price range.
Objections in no particular order:
Filament power? 1.4 volts @ 50 mA -- 2.8V@ 100 mA (3V4)
Warm-up time? Consider running the filament at a fraction of full
power; switched by MOSFET
High voltage for the plate and screen?? Three 9-volt batteries connected in series = 27 V., falling to
18 volts at dropout.
Bulky, fragile tubes? Don't over-miniaturize the project, and don't use it as a football.
73--
Brad? AA1IP
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Re: Q: Destructive experiment on a dead BS
Hi Hans
The only load I can think of to cause a BS170 over-volt failure is something?hanging?off of the antenna connector that will induce a high SWR,?like some non-inductive resistors series-ed or paralleled to give a high SWR.? I have some coaxial relays that should be fast enough to switch between 1:1 SWR and 10:1 SWR, but I don't think I have a good way to send a measurable, measured, and consistent?"kill" pulse to switch between the two loads.
One thing we've seen empirically is that people who b;low up their BS170s tend to do it again ... and many aren't using the same BS170s that come from the QRPLabs assembly line.
I have a bunch of BS170s but I didn't remember to save the paperwork?on them, so I can't be sure if they came straight from Tier 1 disti, or from a third-party (gray market) that bought from Tier 1, or from some back-alley relabeler in a Chinese alley.? Googling the label on one of the sealed packages indicates that they're from Jameco, but the device markings are ... well, let's call them "agnostic".
In contrast, the unused BS170s in my unbuilt Rev 4 QDX google out to be On Semi devices.? My initial plan was to socket the BS170s ... I wonder whether I should use my generic BS170s first, to see if they blow up from the start (into a known-good 50 ohm dummy load). ?
73 Jim N6OTQ
Shaving down the TO-92 package should reduce its thermal resistance ... but that still doesn't manage the >60V voltage?excursions that are usually the killer of BS170s.? Those are generally just user error.?
If > 60V excursions are the usual killer of BS170s, do you have an actual defined load circuit that will by measurement, produce over 60V peaks at the drains of the BS170s? If so I'd love to know, because as yet I have not had time to rig up some tests. It would be very interesting to have an actual case to replicate and test.?
?
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Re: Q: Destructive experiment on a dead BS
On Wed, Sep 13, 2023 at 01:52 PM, Clive - G4KCM wrote:
The SOT23 package BS170 might actually be a better option as they have thicker and shorter terminations.
MMBF170 rated 417¡ãC/W (yikes!) vs BS170's 150¡ãC/W makes it a poor substitute, thermally.??https://www.onsemi.com/pdf/datasheet/mmbf170-d.pdf 73, Don N2VGU
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Re: #qmx Antenna Tuner Can Kill PAs
#qmx
John Zbrozek started the development of an LTSpice IV model of the QDX PA that he and I expanded to test a theory on what happens when the transmitter is turned off at the end of an FT8 cycle.? The model and subsequent bench testing verified a voltage spike at the end exceeding 60 volts.? I measured over 100 volts for a very short period on my Rev 1 QDX.? This can be eliminated with a "commutating" diode to dissipate the built-up magnetic field.? Subsequent tests indicate that the single diode does eliminate the spike.
Because of the minimal duration and normal variance on devices compared to specifications, the likelihood of your QDX suffering from this problem is minor.? There are many QDX in service that have not exhibited the failure.? The ones that are noticed are the ones that have failed.? Consider that thousands of these radios are in operation, and we are seeing tens reported with a failure that could be power-related or severe operating conditions.
For myself, I have installed the diode on my QDX.? This is not needed for the QMX, as the key shaping circuit removes the sudden cutoff of the PA supply.? The QMX would not have the issue.
I have done some simulations of short and open loads on my most recent model of the QDX PA.? I can not get an overvoltage with either of those conditions.? This leads me to believe that the Zeners to protect the BS170s are most likely unnecessary.? That is not to say that a high SWR would not cause a failure.? It indicates that it is likely not voltage but a power or current-related issue.? I have not looked into that failure mode.? Since a voltage failure does not seem probable, adding the Zeners is not a fix for the problem.? The Zeners would not hurt, but I doubt it will add much protection.
It is still good practice to check the antenna for high SWR before the first transmission in a session.? I would also avoid applying full power to an ATU connected to a QDX.?
A request to Hans would be a lower power tune mode for the QMX that could be done in software with the key shaping circuit already part of the QMX.? This would need a hardware mod to work on the QDX.
The above are my observations and conclusions.? Please let me know if any data goes against any of the above.? I am ALWAYS open to constructive feedback.? It is one of the methods I use to learn.
73
Evan
AC9TU
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Re: #qmx Antenna Tuner Can Kill PAs
#qmx
As a pilot of over 30 years in small aircraft (mine was C150) the concept of a parachute was?
reserved for the willful jumping out of an airplane.
The risk analysis is that most samll planes are overbuilt and a failure other than
power plant (engine) was unlikely.? And engine failure meant your a glider
not a rock.? Pilots that fly acrobatics do wear them as there is significant
possibility of over stressing the air-frame with potential for negative outcome.
In the realm of transmitters.? We need to keep in mind its not a critical risk
to life and property like a rocket engine failure.? We also know if a known?
load without mismatch is used failure is less likely.
So in the end if you using a ATU or a manual one you are stress testing with?
increased failure risk.? ?I see the basic solution, a matched antenna.
In the end do not blame the cow for soggy cereal.
--
Allison
------------------
Post online only,?
direct email will go to a bit bucket.
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Re: FedEx invoice for import to UK
It's always Blursday!
73, Willie N1JBJ
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On Sep 13, 2023, at 1:57 PM, Hans Summers <hans.summers@...> wrote:
What day is it today anyway.
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Re: Q: Destructive experiment on a dead BS
I'm still thinking squirrel cage blower - with a large Peltier Junction.
Lee KX4TT
On Wednesday, September 13, 2023 at 02:21:23 PM EDT, ajparent1/kb1gmx <kb1gmx@...> wrote:
That and the SOT23 part is? far lower power rating,? 300mW.
Data sheet posted to thread:
/g/QRPLabs/message/109864
--
Allison
------------------
Post online only,?
direct email will go to a bit bucket.
|
Re: Q: Destructive experiment on a dead BS
That and the SOT23 part is? far lower power rating,? 300mW.
Data sheet posted to thread:
/g/QRPLabs/message/109864
--
Allison
------------------
Post online only,?
direct email will go to a bit bucket.
|
Re: Q: Destructive experiment on a dead BS
Shaving down the TO-92 package should reduce its thermal resistance ... but that still doesn't manage the >60V voltage?excursions that are usually the killer of BS170s.? Those are generally just user error.?
If > 60V excursions are the usual killer of BS170s, do you have an actual defined load circuit that will by measurement, produce over 60V peaks at the drains of the BS170s? If so I'd love to know, because as yet I have not had time to rig up some tests. It would be very interesting to have an actual case to replicate and test.?
?
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Re: Q: Destructive experiment on a dead BS170
Hello Jim
Use to work in a shop about 30 years ago where we crammed 10 pounds of stuff into a 1 ounce bag.
This was before surface mount transistors became readily available. Without knowing it we kind of
made the precursor. We would fixture a TO-92 on the Bridgeport and start removing layers of the
epoxy with an end mill. The amount that could be removed was significant and when done with a?
production device the accepted thickness we used was nominally about 35% of the original
thickness. If memory serves me correct it worked out to 1.1 mm on each side. We then folded
the leads at 90 degrees from the stock plane by using the dull edge of an Xacto # 11? blade, then
bent the leads back 90 degrees to they could be attached to the pc board. We clipped the leads
off to leave about 0.75 - 1.0 mm of the lead that would lay flat on the board, allowing easy
attachment.
We did similar non-standard applications with glass diode packaged devices, cutting the leads as short as possible and milling a slot in the PC board for the diode to lay in.
On Sep 13, 2023, at 1:58 PM, N5SE <bwmoore@...> wrote:
Jim (N6OTQ),
I just checked Amazon and there are several vendors for the BS170. Most offer 10 for less than a dollar. I am willing to spend that kind of money for a joint experiment. What say?
Hi all
One of the limiting factors in heat dissipation on the BS170 is the plastic package.? The plastic case in its?existing geometry is to provide for easy handling with existing tools.? Since we're not robots, that physical parameter is no longer an issue.
Does anybody have a vertical mill and a few dead BS170s and is willing to mill off some of the plastic case?
This is to see how thick the plastic is before the die and/or leadframe is exposed.? The next step is to take a few good BS170s and mill off part of this thickness to see whether heatsinking becomes more effective.
Experimenters?
73
Jim N6OTQ
--
N5SE
Billy Wayne Moore
7066 Shady Knoll Ln
Willis, TX 77318-6324
Phone: 936-537-2975???
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Re: Q: Destructive experiment on a dead BS
Clive,
You're right that the SOT-23 package is probably better thermally than the TO-92.? More lead area, less plastic.
But you can't socket the SOT-23 and changing them is a PITA for most hams.
Shaving down the TO-92 package should reduce its thermal resistance ... but that still doesn't manage the >60V voltage?excursions that are usually the killer of BS170s.? Those are generally just user error.? But heat degradation sneaks up on you, and if the BS170s aren't thermally coupled to the radio case, you'd never know that they were running hot.
Between the over-volt failures and the overheating failures, it's no wonder that a few folks have experimented with changing the BS170s for something more rugged -- but in the case of the IRF510, less capable at the high end of HF and less suited to a 12VDC supply. ?
When I can afford a QMX or two to blow up I have a few of?RD16HHF1 to play with (and blow up).
73 Jim N6OTQ
Jim, you need to chase some of the guys dissecting and polishing various old chips.? My gut feeling with regards to the BS170 saga is that a well soldered joint with good penetration to the topside offers more thermal protection due to the relative transfer lags than anything done to the plastic case.? The SOT23 package BS170 might actually be a better option as they have thicker and shorter terminations.? As I say no science involved in this :)
Best 73, Clive G4KCM
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Re: FedEx invoice for import to UK
Hans (G0UPL),
I have been had. My head is hanging low, I have been beat at my own game, but by the master. What year is this anyhow?
Last comment on this topic!
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Whoooaaa?Billy
I had Tuesday off, what, when? What day is it today anyway.?Ah Wednesday. Well I guess I did sleep half of yesterday until post-lunchtime, after the good post-doctor visit feeling that I was in safe hands and perhaps the new stronger antibiotics might
actually work this week!
On Wed, Sep 13, 2023 at 8:41?PM N5SE < bwmoore@...> wrote:
Hans (G0UPL),
Strength, Pull it together! As you said, "I'm supposed to be on re-entering rolling ball phase AVOIDANCE." Ok you have had Tuesday off. I guess you deserve a vacation, you have had it. You are just going to have to quit looking at this topic.
If I am going where I should not go, tell me. You should know me well enuf now to tell me how the cow eats the cabbage. And I have a feel for humor so I recognize you might be enjoying a spate of humor. If so take the first few lines as humor and we are even.
Same fascination about Evoluon here, look someone has frozen time here?
Thanks, great stuff, yep that's the rolling ball sculpture?at 2:00 minutes in to the video; though you only see a small portion of it not the whole thing. OOOOhhh you shouldn't be showing that stuff to me, I'm supposed to be on re-entering rolling ball
phase AVOIDANCE. Whose side are you on anyway!
--
N5SE
Billy Wayne Moore
7066 Shady Knoll Ln
Willis, TX 77318-6324
Phone: 936-537-2975???
-- N5SE
Billy Wayne Moore
7066 Shady Knoll Ln
Willis, TX 77318-6324
Phone: 936-537-2975???
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Re: #QMX #QDX #QDX-M output transformers (WTST and RWTST) documentation
#qmx
#qdx
#QDX-M
Thanks Walt
I have corrected the typo on pages 1 and 11.
Hans,
Version 1.00a of the document has WSTS instead of WTST on pages 1 and 11.
Walt - KK4DF?
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Re: Q: Destructive experiment on a dead BS170
Jim (N6OTQ),
I just checked Amazon and there are several vendors for the BS170. Most offer 10 for less than a dollar. I am willing to spend that kind of money for a joint experiment. What say?
toggle quoted message
Show quoted text
Hi all
One of the limiting factors in heat dissipation on the BS170 is the plastic package.? The plastic case in its?existing geometry is to provide for easy handling with existing tools.? Since we're not robots, that physical parameter is no longer an issue.
Does anybody have a vertical mill and a few dead BS170s and is willing to mill off some of the plastic case?
This is to see how thick the plastic is before the die and/or leadframe is exposed.? The next step is to take a few good BS170s and mill off part of this thickness to see whether heatsinking becomes more effective.
Experimenters?
73
Jim N6OTQ
-- N5SE
Billy Wayne Moore
7066 Shady Knoll Ln
Willis, TX 77318-6324
Phone: 936-537-2975???
|
Re: FedEx invoice for import to UK
Whoooaaa?Billy
I had Tuesday off, what, when? What day is it today anyway.?Ah Wednesday. Well I guess I did sleep half of yesterday until post-lunchtime, after the good post-doctor visit feeling that I was in safe hands and perhaps the new stronger antibiotics might actually work this week!
On Wed, Sep 13, 2023 at 8:41?PM N5SE < bwmoore@...> wrote:
Hans (G0UPL),
Strength, Pull it together! As you said, "I'm supposed to be on re-entering rolling ball phase AVOIDANCE." Ok you have had Tuesday off. I guess you deserve a vacation, you have had it. You are just going to have to quit looking at this topic.
If I am going where I should not go, tell me. You should know me well enuf now to tell me how the cow eats the cabbage. And I have a feel for humor so I recognize you might be enjoying a spate of humor. If so take the first few lines as humor and we are even.
Same fascination about Evoluon here, look someone has frozen time here?
Thanks, great stuff, yep that's the rolling ball sculpture?at 2:00 minutes in to the video; though you only see a small portion of it not the whole thing. OOOOhhh you shouldn't be showing that stuff to me, I'm supposed to be on re-entering rolling ball
phase AVOIDANCE. Whose side are you on anyway!
-- N5SE
Billy Wayne Moore
7066 Shady Knoll Ln
Willis, TX 77318-6324
Phone: 936-537-2975???
|
Re: Q: Destructive experiment on a dead BS
Jim, you need to chase some of the guys dissecting and polishing various old chips. ?My gut feeling with regards to the BS170 saga is that a well soldered joint with good penetration to the topside offers more thermal protection due to the relative transfer lags than anything done to the plastic case. ?The SOT23 package BS170 might actually be a better option as they have thicker and shorter terminations. ?As I say no science involved in this :)
Best 73, Clive G4KCM
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Re: Best ways to measure output power w/ an o'scope and access ground
On Tue, Sep 12, 2023 at 10:11 AM, Stephan Ahonen KE0WVA wrote:
I have one of sitting in front of me right now. Very unsophisticated construction, regular old off the shelf 1-watt resistors, the nanoVNA tells me it's within 1 ohm of the bullseye on the smith chart all the way up to 20 MHz. Seems to me that HF and below is pretty forgiving
Absolutely so. As a further aside, the interesting if slighly simmering discussion around performance of typical amateur homebrew "bog standard" attenuators and dummy loads does leave me pondering quietly quite how much an error of, say, 1dB ever really matters.? They all "add up" of course and so we want to get the best we can out of every stage of a radio contact, but in absolute terms we're for the most part exploiting (battling?) an ionosphere that varies constantly in wonderful ways.? Signal to noise ratios, it seems to me, are the thing - and what's between our ears makes an ultimate measurement there, of intelligibility. The numbers in power measurements feel worrying perhaps, 7dBW plus or minus or dB is one thing, where the range from 4W through 5W and up to 6.3W may to some seem a huge uncertainty.? But it's just one dB.? The losses through the "aether" from one's QTH to our contact at the other end are likely to be much more uncertain (at HF at least) and we can work to do the best we can without knowing the absolute figures. Hans provides us with built in test equipment to get best performance out of our builds - it would be a great shame if beginners felt that they needed to invest a lot more to enjoy this wonderful hobby.? Just my two pennyworth. 73 Rod G0VKX one-time G8FJN
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Re: FedEx invoice for import to UK
Hans (G0UPL),
Strength, Pull it together! As you said, "I'm supposed to be on re-entering rolling ball phase AVOIDANCE." Ok you have had Tuesday off. I guess you deserve a vacation, you have had it. You are just going to have to quit looking at this topic.
If I am going where I should not go, tell me. You should know me well enuf now to tell me how the cow eats the cabbage. And I have a feel for humor so I recognize you might be enjoying a spate of humor. If so take the first few lines as humor and we are even.
toggle quoted message
Show quoted text
Same fascination about Evoluon here, look someone has frozen time here?
Thanks, great stuff, yep that's the rolling ball sculpture?at 2:00 minutes in to the video; though you only see a small portion of it not the whole thing. OOOOhhh you shouldn't be showing that stuff to me, I'm supposed to be on re-entering rolling ball
phase AVOIDANCE. Whose side are you on anyway!
-- N5SE
Billy Wayne Moore
7066 Shady Knoll Ln
Willis, TX 77318-6324
Phone: 936-537-2975???
|
Donald S Brant Jr
Lee
N5SE
Clive - G4KCM