Re: QMX - smoke - another C107/Q108 failure
/I do remember reading about at least one other person who killed their QMX by toggling their power supply between 6 and 12 volts, in order to toggle their transmit power. This is similar to my own
By
Paul - AI7JR
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#108799
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Re: QMX - smoke - another C107/Q108 failure
The N-Channel FET Q101 will conduct ON if the Gate Threshold voltage is nominally 1.7V. That is with +12V, +9V, or +7.5V feeding the 78M33 regulator. This in turn causes Q102 to conduct and the 78M33
By
Kees T
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#108798
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Re: No receive QMX
I used three different colors of magnet wire so it was easy to figure out what wire went where.
--
73, Dan? NM3A
By
Daniel Walter
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#108795
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Re: BS170 Fail
Lately I am experimenting with FDT86256 mosfet in my design Class E PA rig and am quite happy with it over BS170.
Has a higher voltage tolerance and with one mosfet I can get 5
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Barb WB2CBA
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#108793
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Re: BS170 Fail
For best thermal contact between the round side of the transistor and the board, I recommend thermal pads ( https://www.amazon.com/thermal-pads/s?k=thermal+pads ) , which will better conform to the
By
Stephan Ahonen KE0WVA
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#108792
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Re: QMX - smoke - another C107/Q108 failure
Those are all good reasons the LTM8078 won't be the best choice for this particular application, I really just picked it by going on the Analog Devices web site and filtering for a dual-output
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Stephan Ahonen KE0WVA
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#108791
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Re: BS170 Fail
Wayne,
As Tony AD0VC pointed out, the commutating diode across L14 is definitely a
good idea regardless of which FET you use. The TN0106 produces a much
higher spike voltage than the BS170 because
By
Tony Scaminaci
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#108790
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Re: BS170 Fail
This is interesting, Tony. I'm gonna have to study the schematic to determine the direction of the diode. I think I read of this solution in another post.
For now...I live in the far SE corner of GA,
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Wayne KB4DSF
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#108789
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Re: BS170 Fail
My apologies to the group. I called out the wrong transistor - I meant to
spec the TN0106 as a good replacement for the BS170. Thanks Tony for
refreshing my memory, it’s been months since John Z and
By
Tony Scaminaci
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#108788
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QMX -- first try, first problems (bad sweeps, no output power)
Hi!
I received my QMX today, assembled it, and flashed latest firmware
(1_00_009). I didn't test it on air yet (only with a dummy load).
I have several issues with it. Two are serious, other are
By
Adam
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#108787
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Re: BS170 Fail
I ran a TN0106 in my high band QDX for several months and had no issues. I had better output on 10 meters than with the BS170 but nothing dramatically better. I also ran the VN0606 in my low band unit
By
mux_folder2001
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#108786
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Re: BS170 Fail
Lead shape and/or packaging.
Mike
WM4B
Sent: Tuesday, August 29, 2023 7:04 PM
To: [email protected]
Subject: Re: [QRPLabs] BS170 Fail
Thank you. Does anyone know if there is a real
By
Mike Besemer - WM4B
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#108785
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Re: BS170 Fail
Thank you. Does anyone know if there is a real difference between the variants of the BS170? I just ordered BS170P mosfets. There were other variants, but I went with this one since it was actually
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Wayne KB4DSF
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#108784
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Re: BS170 Fail
The TN0606 seems to have a much higher input capacitance than the BS170 and this may translate into slower switching and increased dissipation especially on higher frequencies .
Hard to say if they
By
Bruce Akhurst
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#108783
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Re: BS170 Fail
I have a QRPometer from NM0S. (It was originally a 4SQRP kit, and is now
offered by its designer.) It is both a power meter and an SWR meter, and
when used as an SWR meter has an absorptive
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Shirley Dulcey KE1L
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#108782
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Re: QMX: Kit Build complete - My observations
Hi,
my QMX is running well at +12V. Had to repair the Q103/Q104 short issue first by moving a bit the bigger one. Fortunately I measured the short before using it.
I went the assembly my way:
-
By
Bojan Naglic
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#108781
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Re: BS170 Fail
A resistive bridge, NOT the transformer kind, has 6dB of insertion loss which absorbs much of the reflected power, so the VSWR the transmitter "sees" is ~1.5:1 or less, regardless of what the load is
By
Donald S Brant Jr
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#108780
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Re: No receive QMX
Hi Chris,
when my QMX was very unsensitive (-53 dBm) I found my mistake, I have cross wired the two?of three trifilar pairs?(B-C and C-B instead of B-B and C-C).
When I repaired that I was
By
Bojan Naglic
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#108779
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Re: CAT port returns ` ` ` on QCXmini
Jerry, you can’t send characters one at a time to the mini, that why you are seeing the ‘ reply. you have to put the whole command together and send it as a block.
73 Ken g4apb
By
KEN G4APB
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#108778
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Re: CAT port returns ` ` ` on QCXmini
I tried USB to RS232 on my QCX Mini and it didn't work for me. USB to TTL worked like a charm.
Jim - W4BQP since 1953
By
Jim Campbell <jecspasc@...>
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#108777
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