Re: Low output Bitx40


1: Power connector all wires connected properly ?

2: RV1 at center ?

At 18-07-18, you wrote:
Thank you for quick reply.

Re-checked soldered correctly, and confirmed continuity to board connector.

Re: Low output Bitx40


R136 with Bitx40!

1: Power connector all wires connected properly ?

2: RV1 at center ?

At 18-07-18, you wrote:
Thank you for quick reply.

Re-checked soldered correctly, and confirmed continuity to board connector.

Re: Low output Bitx40

_Dave_ K0MBT

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.

Re: Low output Bitx40

Jerry Gaffke

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.

Re: The new uBITX boards are here

iz oos

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" <> 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

Re: Low output Bitx40

Allen Woolfrey

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.

Re: Low output Bitx40

Jerry Gaffke

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

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.

Re: Need a video on ubitx troubleshooting

R. E. Klaus

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.

Re: RF power chain mods and improvements..

ajparent1/KB1GMX <kb1gmx@...>

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)

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.


Re: Need a video on ubitx troubleshooting

Arvo W0VRA

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.

Re: Mike element

Greg Wasik

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.


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.

Re: Simple RF actuated LED Tx indicator #ubitx #bitx40


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.


AGC kit working great after a big "DUH!" moment

Bill Carpenter <nz0tham@...>

I built and installed the Kees AGC kit yesterday but dang thing would not work.  Waited until today to check it out.  A close look at the board showed that every component was soldered properly with no solder bridges or other issues.  But then, I noticed that pins 1 and 2 at the top of the board hat a "J" printed above them with a jumper symbol.   That's when I re-read the instructions from Don that stated "if you are not installing an RF gain control you must jumper pins 1 and 2".

Well, DUH!  I chose to not install an RF gain control.  Once a jumper was soldered all is good

Posting in case anyone else has a tendency to not read instructions slowly enough......

73, Bill NZ0T

Re: Simple RF actuated LED Tx indicator #ubitx #bitx40


Guess I should have watched your video first as you said everything I just said:-(


Re: receive works great, but no trans power, #ubitx-help


Allison wrote:

"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." 

If there is a possibility that these diodes could cause spurs during TX (which I doubt), then it seems the safer approach is to connect the back-to-'back diodes from K1 pin 12 to ground.  K1 pin 12 is grounded and isolated from the RX/TX circuitry connected to K1 pin 14  during TX, which guarantees that the diodes can't cause spurs during TX.  Placing the the diodes from K1 pin 12 to ground should still provide the same protection for Q90 during receive as connecting them from K1 pin 14 to ground. 


Carl,  K0MWC

Re: Unbuilt uBITX Ver4 and Blue Cabinet for sale.

Mike Short

So I would need a 70MHz buffer board for this?



Re: Mike element

Jerry Gaffke

The "dB SPL" gives the Pascal part of 1V/Pascal, but it does not specify the 1V part.

94 dB SPL means 94 dB above the reference sound pressure level of 20 uPa,
where 20 uPa is around the bottom threshold of human hearing.
When somebody says a rock concert has a sound level of 110 dB, they mean 110 dB SPL.

So  a complete spec for microphone sensitivity might say how many "dB SPL" to give 1V out.
Or they might say how many "dB" to give 1V out, and mean the same thing.
Those acoustic engineers only deal with one kind of dB, and assume any such figure is for dB SPL,
and describes a measured sound pressure level, not a ratio.

In radio work, "dB" refers to a ratio, perhaps the output power of an amp divided by the input power.
To give a power measurement we might say 20 dBm, which is the ratio of the 100 milliwatts we measured
divided by an inferred reference of 1 milliwatt:      10**(20/10) = 100. 
So dB is a ratio of two powers, and dBm is a specific power level. 

While I'm on a rant, here's a bit more for those still puzzled but vaguely curious.

I've said that dB in radio work means a ratio.
A good receiver might have a dynamic range that can simultaneously deal with incoming
signals of both one microvolt and one volt at the antenna, and still allow us to hear
the small signal.  Since power is the square of voltage divided by resistance,
that's a power ratio of 1,000,000,000,000 between the big and the little signal.
These numbers quickly got out of hand, especially for those folks back in 1930 working
with a slide rule.

It might be easier to say that the big signal has 12 more zeros after it than the little signal.
Though that isn't very precise, if the receiver front end was improved to deal with
a big signal of up to 2 volts it would then have 12.6 more zeros than the little signal.
(Those who remember high school algebra will understand how to deal with a fractional power of ten.)
Rather than deal with fractional numbers like that, they decided to just multiply the zero count by 10,
so we can now say that a receiver capable of dealing with signals between 1uV and 2V has 
a dynamic range of 126 dB. 

Through the magic of logarithms, when the gains of two amps in series are expressed in dB we can
determine the total gain of the amp by adding a couple 2 digit numbers in our head instead of multiplying
out a couple larger numbers.  You don't see dB used much in hard science such as a physics textbook,
they just deal with the big numbers.  But radio engineers who live and breathe this stuff 12 hours/day
needed an easier way to do the calculations in their head, and dB won out.

The formula to go from a power ratio to dB is  10*log(P1/P2).
Here, "log" is base ten, and log(1000) is 3.
For even powers of 10, the log() function just tells us how many zeros.  
In the case above, we have 10*log(2000000*2000000/1) = 126 dB
(where voltages are expressed in microvolts).

I usually use python as my calculator when figuring out this sort of thing.
It's available for almost every computer (unfortunately a Nano is too small)
and fully interactive, highly recommended.  The log function comes from an
external library called "math", so we must first bring in that library to make it available.
Here's a python session to test the above formula, it gives a more precise result
than my approximation of "126 dB".:

import math
>>>  126.02059991327963

We can go from dB back to a power ratio with this:
>>>  4000000079872.417

and go back to the voltage ratio by taking the square root of the power ratio:
>>>  2000000.019968104

Jerry, KE7ER

On Wed, Jul 18, 2018 at 08:14 AM, <k1yw@...> wrote:
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.

Re: RD16HHF1 power curve flattening...some

Kevin Rea

How long does it take you to receive things from polida2008 ?





From: <> On Behalf Of Ashhar Farhan
Sent: Tuesday, July 17, 2018 10:44 PM
Subject: Re: [BITX20] RD16HHF1 power curve flattening...some


Are you sure that the pins are not shorting? 


On Wed, 18 Jul 2018, 10:23 Mvs Sarma, <mvssarma@...> wrote:

I too suspect the devices  OP bought.  He could remove them and test with a DMM for the correctness of pinout.


 I am currently depending for my RD hhf and hvf devices, on an ebay seller " polida2008" after having suffered fake ones from another seller.

 This seller is now operating with another seller name " 5hk1584 "

 While i have no business deal with this seller(s), I do enjoy genuine devices for my hobby.  Hope it helps.


MVS Sarma



On Wed, Jul 18, 2018 at 9:02 AM, Kevin Rea <reakevinscott@...> wrote:

On Thu, Mar 8, 2018 at 05:14 PM, "John" <passionfruit88@...> wrote:

Hi John,

did you mount the new pot in the front or  back or just leave it on the breadboard ?
kevin rea
lancaster, calif.


Re: I think this will work for the Ubitx...microphone

Kevin Rea

Thanks !



From: <> On Behalf Of Mike Woods
Sent: Tuesday, July 17, 2018 11:43 PM
Subject: Re: [BITX20] I think this will work for the Ubitx...microphone



If you search on you will find the wiring diagram for the Baofeng speaker/mic.

You will need to modify the mic to work with the uBITx (but not the BITX40 or BITX20) because the T/R switch is on high with 5v on it.

Separate out the switch from the mic internally.


On 18/07/18 9:53 AM, Kevin Rea wrote:

Hi guys,
I am just getting ready to build my first Ubitx.
I am going to use a Baofeng Microphone to do it.. so I bought one and took it apart..
and this is what I came up with after tracing the wires..
I am just using the microhone part of the mike, not the speaker.

I think this will work......????

Kevin Rea


Mike Woods