Re: FT8 problem solution ...??? sBITX V2
Upgrade to V3. It sorts all these problems. - f
On Thu, Nov 2, 2023 at 4:00?PM Jens < hb9joi@...> wrote: I have the same big problem with the FT8 transmit-receive-time-slot management from the FT8 software .
Anybody knows a solutions how the FT8 program-code must be edited / new programmed that FT8 will work correct ???
Thanks in advance ... ! Jens / HB9JOI
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Re: v3 software, alpha is here
Thanks. ?This is what I was looking for.?
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Bob AA4FJ
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Re: strange behaviour of IRF MOSFETs
Ashhar, can I first of all congratulate you on all the work on the sbitx V2 and V3. This new V3 I have upgraded to is superb and has gone well above all my expectations. It must surely has made the project more appealing to the new and old enthusiasts.
Farhan;
I switched out the silpads in my DE for Alumina Ceramic insulators. The attached thermal image photos show the stock silpad under the right FET and an Alumina Ceramic insulator under the left FET. The transmitter was key-down at 30 Watts for maybe 5 seconds. I saw a pretty dramatic difference between the two. I had planned to take some better images, as well as make a short movie showing the temperature difference resulting from an insulator change-out, but the FET on the right was having no more of it and shorted out.
No doubt that Aluminum Nitride insulators would work even better. I was able to get a lifetime supply of Alumina Ceramic insulators from Amazon in two days for not a lot of $$, so I'm happy with this solution.
My conclusion is that there is room for improvement from the stock silpads.
I posted a video in the files section a couple months ago - it shows that the FETs stabilize in temperature relatively quickly.
73; Steve, N3SB
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Re: strange behaviour of IRF MOSFETs
Farhan;
I switched out the silpads in my DE for Alumina Ceramic insulators. The attached thermal image photos show the stock silpad under the right FET and an Alumina Ceramic insulator under the left FET. The transmitter was key-down at 30 Watts for maybe 5 seconds. I saw a pretty dramatic difference between the two. I had planned to take some better images, as well as make a short movie showing the temperature difference resulting from an insulator change-out, but the FET on the right was having no more of it and shorted out.
No doubt that Aluminum Nitride insulators would work even better. I was able to get a lifetime supply of Alumina Ceramic insulators from Amazon in two days for not a lot of $$, so I'm happy with this solution.
My conclusion is that there is room for improvement from the stock silpads.
I posted a video in the files section a couple months ago - it shows that the FETs stabilize in temperature relatively quickly.
73; Steve, N3SB
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Re: strange behaviour of IRF MOSFETs
Gordon, I failed to mention but I have tried it with Aluminium Nitride, Silpads (Grey and Blue) and Mica insulators, there was no difference at all. I should get a contact sensor to measure the rise of the heatsink temperature to know how these two are related. I will further document this over the next few days.
It would be interesting to see if the drop in power is reduced with aluminum nitride insulators.? Previous work has suggested it will decrease the rise in temperature of the die
For a very simplified transmitter, it does reasonably well!? Different goals and different constraints on different designs.? Each has its place. ??
Gordon Kx4z? On Nov 18, 2023, at 13:40, ajparent1/kb1gmx <kb1gmx@...> wrote:
?I put a copy of the full article in the files area under my call.
--
Allison
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Please use the forum, offline and private will go to bit bucket.
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Re: strange behaviour of IRF MOSFETs
It would be interesting to see if the drop in power is reduced with aluminum nitride insulators.? Previous work has suggested it will decrease the rise in temperature of the die
For a very simplified transmitter, it does reasonably well! ?Different goals and different constraints on different designs. ?Each has its place. ??
toggle quoted message
Show quoted text
On Nov 18, 2023, at 13:40, ajparent1/kb1gmx <kb1gmx@...> wrote:
?I put a copy of the full article in the files area under my call.
--
Allison
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Please use the forum, offline and private will go to bit bucket.
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File /SBITX KB1GMX-mods ideas./Bias Circuit for LDMOS Amplifiers.pdf uploaded
#file-notice
The following files and folders have been uploaded to the Files area of the [email protected] group.
By: ajparent1/kb1gmx <kb1gmx@...>
Description:
Complete W1GHZ, N1JEZ article.
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Re: strange behaviour of IRF MOSFETs
I put a copy of the full article in the files area under my call.
--
Allison
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Please use the forum, offline and private will go to bit bucket.
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Re: strange behaviour of IRF MOSFETs
Farhan,
You didn't specify where or details.? This is the revised sBitx or some proto?
What the bias when cold and after immediately after a keydown session?
While my amps do not exhibit this, I've seen it in others especially when??
heating is an issue.? ?
Examples are the usual Ebay "70" watt amps?and similar copies.
--
Allison
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Please use the forum, offline and private will go to bit bucket.
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Re: strange behaviour of IRF MOSFETs
DJ9BFC,
Yes it could and no not in that circuit.? However to get the needed thermal
coefficient it needs to be two diodes in series.
The npn is a 2n3904 that is mounted on the heatsink near the device.
It was picked as well characterized, doesn't hurt that its cheap.
--
Allison
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Please use the forum, offline and private will go to bit bucket.
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Re: Ubitx v6 extremely low power audio transmit, cw transmit ok
Make sure meter is set to ¡°peak¡± power, not average power.
bob
wd8lic
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Re: strange behaviour of IRF MOSFETs
why is there an npn transistor used as temp sensor?? would not a
simple 1n4148 also do the same thing??
dg9bfc sigi
Am 18.11.2023 um 19:13 schrieb
ajparent1/kb1gmx:
toggle quoted message
Show quoted text
Added is the bias circuit that I use and created by W1GHZ and
N1JEZ
for use with high power amps? using RF rated LDmos parts.? Its
posted
to show an example, not the only way.
I could only post an excerpt as groups.Io seemed to have a fit.
--
Allison
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Please use the forum, offline and private will go to bit bucket.
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Re: strange behaviour of IRF MOSFETs
Allison, This is for two IRF510s in push pull. Each draws about 2A. Input is 4Ax 13.5v = 54watts. The 100v peak to peak is at the secondary of the PA transformer. The drain swing is about 35v peak to peak. - f
On Sat, Nov 18, 2023, 11:25 PM ajparent1/kb1gmx < kb1gmx@...> wrote: Several things...
One IRF510 spec is 100V breakdown.? More than that and poof.
Also sustained current should be 4A or less (the 5.6A is for
saturated switch mode).
So the question is why it it 100V P-P?? It suggests an open relay,
wrong band LPF selected or seriously bad SWR.? ?Last case is that
the Drain load (transformer) is too high.
100V P-P across 50 ohms is well over 25W,? if its across a 50 ohm
load thats about 35W.? At 13V that's pushing the device really hard
to saturation most likely.? Load current at that power is likely near
a indicator and heating will be significant (for small heatsinks) if linear.
I have several linears using IRF510 mosfet, and I do not see that.
Be wary as when the die heats the gate threshold decreases at
roughly 10mv/degree-C and at that power its likely 100C++ if
not higher.
--
Allison
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Please use the forum, offline and private will go to bit bucket.
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Re: strange behaviour of IRF MOSFETs
Added is the bias circuit that I use and created by W1GHZ and N1JEZ
for use with high power amps? using RF rated LDmos parts.? Its posted
to show an example, not the only way.
I could only post an excerpt as groups.Io seemed to have a fit.
--
Allison
------------------
Please use the forum, offline and private will go to bit bucket.
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Re: v3 software, alpha is here
I got it, it is just a matter of adding another record edit form. I will get to it. - f
On Sat, Nov 18, 2023, 11:37 PM HA3HZ < gyula@...> wrote: ps.: I want to make corrections in the saved file, because I cannot get involved in the process of automatic logging.
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Gyula HA3HZ
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Re: v3 software, alpha is here
ps.: I want to make corrections in the saved file, because I cannot get involved in the process of automatic logging.
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Gyula HA3HZ
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Re: v3 software, alpha is here
On Sat, Nov 18, 2023 at 06:05 PM, Ashhar Farhan wrote:
Can you explain what the bug is between the keyboard and the logger?
I correct the errors in the database, because the font size of the 7" screen is small. Therefore, when I want to correct it, I copy the sbitx.db file to a USB stick. Then I installed the DB Browser (SQLite) program on the PC in the same way, so I can correct it mistakes afterwards. If I could correct the log data on the spot, then I wouldn't have to copy it back and forth. So the question is: how can I use a line or an input with the keyboard to fix the Chromium LOG page? ? -- Gyula HA3HZ
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Re: strange behaviour of IRF MOSFETs
Several things...
One IRF510 spec is 100V breakdown.? More than that and poof.
Also sustained current should be 4A or less (the 5.6A is for
saturated switch mode).
So the question is why it it 100V P-P?? It suggests an open relay,
wrong band LPF selected or seriously bad SWR.? ?Last case is that
the Drain load (transformer) is too high.
100V P-P across 50 ohms is well over 25W,? if its across a 50 ohm
load thats about 35W.? At 13V that's pushing the device really hard
to saturation most likely.? Load current at that power is likely near
a indicator and heating will be significant (for small heatsinks) if linear.
I have several linears using IRF510 mosfet, and I do not see that.
Be wary as when the die heats the gate threshold decreases at
roughly 10mv/degree-C and at that power its likely 100C++ if
not higher.
--
Allison
------------------
Please use the forum, offline and private will go to bit bucket.
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Ubitx v6 extremely low power audio transmit, cw transmit ok
Hello All,
? ? I hardly see any power out on transmit on SSB on any band. I can hear the relay click when I press the PTT button and speak into the mic and I see TX on the display but no forward power movement on the needle in my manual tuner. I connected an auto tuner that has a digital display and I saw 0W to maybe 0.3W sometimes.
I tested the mic, I connected the mic to the computer and opened BFO tuning aid web page and I am able to see audio when I speak. I made sure there is no internal mic activated on the computer to prevent a false positive test.
I tested cw transmit on 10, 40 meter bands and I saw 6+ watts on 10m and 15+ watts on 40m. I tested? using manual and auto tuner and got the same readings.
I am able to listen to cw signals and digital signals, I did not hear SSB signal yet but when I did the freq calibration process I was able to listen to and zero beat an AM station so I guess SSB reception should work.
What else should I check to determine why I get this extremely low to no power out using audio on SSB?
Thank you,
73,
Mubeen. KN6KRR
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Re: strange behaviour of IRF MOSFETs
Joel, The all the IRF series exhibit this behavior. Just monitor the RF Output over 1 minute of key down.?
On Sat, Nov 18, 2023, 10:15 PM Joel Caulkins/N6ALT < caulktel@...> wrote: Farhan,
I know you have always preferred the IRF510s, but have you considered the IRF530s? I have noticed that most of the cheap Chinese Linear amps use them to get a good 45-50 watts. I just bought a Micro 50 Plus amp that uses a set of 530s. From all the research I have done on the amp, it seems that it is pretty stable and reliable as long as we don't exceed 50 watts. Might work great for a steady 40 watts on the V3.
Joel
N6ALT
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HA3HZ