Thanks peter,
Leon at ozqrp puts these into all his rigs. I find them to be useful tools to show power output and sufficient SSB modulation.
Joel
N6ALT
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Re: Unbuilt uBITX Ver4 and Blue Cabinet for sale.
William, you could consider the road that SM0JZT has taken. He installed a G4HUP buffer amplifier and uses an RTL-SDR dongle externally. This gives you the best of worlds - a low-cost transmitter and an equally low-cost SDR receiver. I have also bought the buffer amplifier, but will wait with installing it until the winter.  
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Just to throw in another way of specifying microphoen sensitivities . 1V/Pascal is equal to 94 dB SPL.? So you may see either terms when looking at mic specs.
Greg
K1YW
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Re: Need a video on ubitx troubleshooting
On Wed, Jul 18, 2018 at 07:52 AM, Richard E Neese wrote:
I have a ubitx v4 it was workign fine on my 12v 3 amp power brick all fo a sudden whip transmitting the unit shut off and cam back on.
Mine did that, too, because the current draw was too much for the PS, and the PS turned itself off and back and on.? That can happen (at least in my case) on lower bands with a bad antenna mismatch. I did not have further issues like you describe.
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Re: RF power chain mods and improvements..
Sadly based on the data sheet I got some MPSH10s and as reported they didn't perform as expected.
The devices I found worked better for me are:
2n2222A(to18), I tried PN2222 and they?produced less power (better than 3904).
2n2219A,? the same as 2n2222A (they are the same die in different package)
2n3866
2n5109
I also tried a pair of irf510 as drivers with suitable mods for bias and they worked
fairly well. The transformers for predriver and driver were less than optimum using
those.? ?I also tried the 2n6661As and they were about the same as IRF510 and?
for those that might consider it 30* the cost of IRF510, and 9* the cost of 2n2222A.
Others that might work if you have or can find them are:
MRF495, 2sC799, 2sc1306, 2sc1307, 2sc2166
Most of the effort to get not more power as you will get that but more even power
ended up with changing the transformers for better impedance matching at higher
frequencies.? My goal was 10W plus or minus a few and decent power at 10M.
If your pushing for more power in the 80-17M range the 2n2222A is a winner?
in the driver and pre driver along with bias changes already discussed.
Allison
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Re: Need a video on ubitx troubleshooting
You might want to check the power supply too. If something in it died, you might be getting ac on the power lead which could cause this symptom.
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Mucking with RV1 could easily and quickly blow the IRF510.
Whenever adjusting RV1 (the IRF510 gate bias voltage), you should be monitoring?
the drain current into the IRF510 (12v into PA-PWR1) with an ammeter.
RV1 should be set for 100ma and no more (with no audio into the mike), it's very touchy.
At that point (100ma) the IRF510 is just starting to conduct, a little bit more and it will be several amps.
I'm a bit surprised it stopped at 1.6A, perhaps you have a weak power supply, could have been 10A.
Assuming 1.5A going up as heat in the IRF510, that's 12*1.5 = 18 Watts into a very inadequate heatsink.
Will be smoking hot.
This RV1 on the Bitx40 corresponds to RV2 and RV3 on the uBitx (there's two IRF510's on the uBitx).
Same rules apply, don't mindlessly twiddle those pots or you will blow the final.
Should be 100ma into each IRF510.
Twiddling R136 on the Bitx40 and RV1 on the uBitx adjusts the drive level into the transmit pre-amps.
Somewhat less dangerous, as it probably won't cause the IRF510's to blow across the room.
But turning up the gain too high there will cause distortion in your transmitted output
and you will be splattering across the band.
On commercial rigs, this is much like turning the mike gain up too high.
When going for more power by adjusting those pots or increasing the voltage into the IRF510 drain
or when going to long duty cycle transmissions (perhaps digital modes), a good idea to check if
the IRF510 heatsink is getting hot.? If it's too hot to hold your finger on it, that's too hot.
Jerry, KE7ER
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On Wed, Jul 18, 2018 at 07:07 AM, Allen Woolfrey wrote:
RV 1 set at about 30% on arrival.? Adjusting to full CCW raises draw to about 1.6 A on PTT, with no change when using mic.? Reset back to about 30%.? Also, adjusting R136 has no effect.
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Yes, low output when speaking or whistling into mic.
Power wiring correct AFAIK.
RV 1 set at about 30% on arrival.? Adjusting to full CCW raises draw to about 1.6 A on PTT, with no change when using mic.? Reset back to about 30%.? Also, adjusting R136 has no effect.
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Re: The new uBITX boards are here
Hi, I am not Mr Farhan, am just a user and an advanced qrm maker. As for ' Problems: great carrier in SSB mode TX, more then modulation speech signal!' I believe you should move up or down the BFO as it seems to be within the bandwidth of the filter. Most probably your modulation would sound extremely muffled.
Il 18/lug/2018 10:27, "George via Groups.Io" <rx3arg= [email protected]> ha scritto: Dear Mr Farhan
As about me for several days I was asking for help as I've lost the original soft for scale and control of the Si5351. At last I've? find HEX file by KD8CEC and I am happy that it works!( Used XLoader).
But till this time did not find the original file and besides this I am not the Arduino specialist. A lot of words but no FILE and how to load it!
To my mind the R50 feed back of the Q70 should be raised to 820K to raise collector U from 1.8 to 6 V - not to over load it by strong signals.?
Problems: great carrier in SSB mode TX, more then modulation speech signal! What is it? to use only in reception mode?
The final 12 MHz filter is too wide and do not have 6/60 dB features, + some out of channel signals! But stii very simple and original transceiver not noisy with good sound! Some raising of the price of something 140-150 will not be too much for it. Best regards to you and your team 73! George UR4CRG/RX3ARG
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You might try Allard's mod to transmit CW, drive the top of C107 from 5v through a 4.7k resistor:
? ??
If that gives power to your dummy load, then the problem is back in the mike amp or mike.
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Is the low output with you talking into the mic? The carrier is suppressed in SSB as you know and almost no output is expected without modulation.
I had a mic go bad on mine after a month.? ?Found a replacement in an old portable phone.
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R136 with Bitx40!
1: Power connector all wires connected properly ?
2: RV1 at center ?
At 18-07-18, you wrote:
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Thank you for quick
reply.
Re-checked soldered correctly, and confirmed continuity to board
connector.
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1: Power connector all wires connected properly ?
2: RV1 at center ?
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At 18-07-18, you wrote: Thank you for quick reply.
Re-checked soldered correctly, and confirmed continuity to board connector.
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Thank you for quick reply.
Re-checked soldered correctly, and confirmed continuity to board connector.
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Al, check the electret condenser mic element soldering. Polarity is important.
Raj
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At 18-07-18, you wrote: Just finished wiring my bitx40.
Draws ~350ma with PTT, but no change at all when yelling or whistling into mic. (Dummy load present at all times, so don't suspect final blown.)
I see lots of discussion around this issue, but would appreciate advice on how to troubleshoot.
72/3, Al - va3iaw
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Just finished wiring my bitx40.?
Draws ~350ma with PTT, but no change at all when yelling or whistling into mic.? (Dummy load present at all times, so don't suspect final blown.)
I see lots of discussion around this issue, but would appreciate advice on how to troubleshoot.
72/3, Al - va3iaw
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Re: receive works great, but no trans power,
#ubitx-help
That strap could cut Q90-base out of the circuit too, in case that causes RX spurs.
Probably OK to leave the back-to-back diodes in there near Q90-base (to the left of C80)
during transmit, as I doubt we have much more than 0.1vrms there.
Unfortunately, I've got a very long list of stuff to do while the weather is good.
Fiddling with the uBitx isn't on it.
Jerry, KE7ER
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On Wed, Jul 18, 2018 at 03:53 AM, Gordon Gibby wrote:
That would make for a very useful experiment! ? If you try it, let us know what you find out!
?
It¡¯s possible that different transistors have different reverse (base-emitter) break down voltages, which would dramatically change the amount of energy deposited on the base-emitter junction by a strong signals.... I just don¡¯t know enough about the devices to say for sure.
?
?
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Re: Need a video on ubitx troubleshooting
Check voltage at R104, should be 0v. Sounds like CW is on!
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At 18-07-18, you wrote: I have a ubitx v4 it was workign fine on my 12v 3 amp power brick all fo a sudden whip transmitting the unit shut off and cam back on. Now the reciever is working fine but when I transmit I het a loud carrier with a hum to it and no audio output ... I figure something in the transmit section went bottoms up but looking at it with a usb based microscope I see nothign blown on the board no bubbles on chips and no broken or burnt wires.
any input would be helpfull
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Need a video on ubitx troubleshooting
I have a ubitx v4 it was workign fine on my 12v 3 amp power brick all fo a sudden whip transmitting the unit shut off and cam back on. Now the reciever is working fine but when I transmit I het a loud carrier with a hum to it and no audio output ... I figure something in the transmit section went bottoms up but looking at it with a usb based microscope I see nothign blown on the board no bubbles on chips and no broken or burnt wires.
any input would be helpfull
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Re: receive works great, but no trans power,
#ubitx-help
That would make for a very useful experiment! ? If you try it, let us know what you find out!
It¡¯s possible that different transistors have different reverse (base-emitter) break down voltages, which would dramatically change the amount of energy deposited on the base-emitter junction by a strong signals.... I just don¡¯t know enough about the devices
to say for sure.
On Jul 17, 2018, at 23:30, Jerry Gaffke via Groups.Io < jgaffke@...> wrote:
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We have had a couple reports of Q90 frying, but not the mixer.
Perhaps as Gordon notes, these were due to a strong VHF signal.
I believe Gordon has suggested in the past the the failure mode might be?
due to reverse voltage at the BE junction, not forward current.
I have no idea if the back-to-back diodes would significantly contribute to the spurs.
Doubt it would cause trouble where I'm at, as there are no strong local broadcasters.
I should try it, include a strap to remove the diodes if curious about some new spur.
We've got plenty of electrical storms.
Jerry
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On Tue, Jul 17, 2018 at 01:28 PM, ajparent1/KB1GMX wrote:
It the signals are strong enough to fry Q90 the mixer will soon be gone too.
The BE junction is as robust as the mixer diodes.? so whatever you are seeing
is quite strong and could even be ESD.
For ubitx (V3 or 4) a pair of back to back 1n194/4148 diodes from K3 Pin14 to ground
is the best bet as then its only there for RX and has no impact on TX.
Bitx 20 and 40 the solution is different.
Its easily done on the back of the board.
Allison
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Joel Caulkins/N6ALT
Arvo W0VRA
_Dave_ AD0B
Raj vu2zap