Thanks guys. I’ll probably install it them after I get done painting and shielding the case. I was sure it was a log and went out and tested it and yep it sure was I think it came out to 500 ohm mid range or something. Definitely wasn’t 2.35k.
Brad
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Show quoted text
You should go way-way back, Clark, to find true log rotary potensiometers.
Vacuum tube era, when power amplification was voltage related.
They were also higher value units, typically 47 to 100 KOhms, as far as I remember.
Then came the transistor, a current amplification device.
Using a tube log pot in a transistor circuit was something equivalent to a rollercoaster ride in sound (I know first hand).
Succeded by low impedance linear pots, or dual slope linear ones for closer correlation of angular position to output sound level.
Linear (long) throw faders* was another story until VCAs where established.
(*) Penny & Giles faders were the most expencive part in a pro console.
73 Nikos
|
Re: BITX40 CW Carrier Mod - CW Waveform shaping ?
#bitx40
During receive and during SSB transmit, the high side vfo (clk2) is at 45mhz plus the operating frequency.
On CW transmit, the VFO is moved to the operating frequency, and we can shut down clk0 and clk1 entirely if we wish.
If clk0 and clk1 remain active during CW transmit, we could be transmitting stuff from the mike at at 45mhz minus the operating frequency.
On the low bands that won't matter much, as the transmit LPF will take it out.
But if transmitting CW at 28mhz, we could have stuff from the mike going out on the air at 45-28 = 17 mhz?if clk0 and ckl1 remain active.
Regarding key shaping, the keying envelope will be determined by the voltage at T2 pins 3 and 5.
The shape and max amplitude is determined by R104, C1, R105, C10, C22 plus the quiescent voltages at Q10-base
and Q22-emitter.? Not a trivial network.? I would start by messing with R104 and C1 for proper rise and fall times,?
add a resistor from R104-C1 node to ground if rise and fall times are not symmetrical enough.
Generally on QRP rigs key shaping is not to critical so long as it isn't just too abrupt, but something better
might be needed for those feeding this to a 100W amp.
Figure 6.114-E on page 6.63 of EMRFD shows a single transistor integrator that creates a nice trapezoidal
keying envelope.? A similar scheme using a PFET is used in the KD1JV MTR rigs, and many other such CW rigs.
Jerry, KE7ER
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Show quoted text
On Sat, May 26, 2018 at 06:43 am, Michael Babineau wrote:
I am curious if anyone has looked at the shape of the CW waveform generated by the BITX40 using the CW Carrier Mod associated with PE1NWLs Bitx40 sketch ?
It seems to me that there might be room for some improvement by modifying this to provide some simple waveform shaping via an R/C network.?
According to what I have read the rise and fall times for the CW envelope should be something in the order of 5mS or greater for good sounding CW, free of clicks.?
The output from the Raduino via D6 through the 4K7 resistor is essentially a square wave.?
I had a friend record my BITX40 CW signal and send the wav file back to me and I don't actually hear anything that sounds like key clicks, but the keying does sound a?
bit hard.?
Using an online R/C time constant calculator, I calculated that adding approximately 1 uF of capacitance to ground in this circuit (assuming a 4k7 series resistor) would
give the desired 5mS rise time on the?leading edge of the waveform, but I am not sure how to handle the trailing edge ? (I am software guy not an engineer).
Also would adding this additional capacitance to ground have any negative impact on the balanced modulator circuit ??
?Any suggestions ??
While pondering this I had another related thought. ?While keying the BITX40 with the carrier mod the mic amplifier is still active. Does this imply that we should?
be unplugging our microphones while operating CW on the BITX40 to avoid picking up any stray noise ????
Cheers
Michael VE3WMB?
|
Re: The new uBITX boards are here
Ron, C81 was changed to 470pf this is located on the base of Q90 the first driver stage.
toggle quoted message
Show quoted text
On May 26, 2018, at 18:43, w7hd.rh < w7hd.rh@...> wrote:
What capacitor was changed to what value?
Ron W7HD
On 05/26/2018 12:19 PM, Ashhar Farhan
wrote:
Peeps,?
HF Signals has rolled out the new (r4) version of the PCBs.
Here are the changes:
1. A new, low distortion audio amplifier made from discrete
transistors. This is one is optimized for head-phones and
connecting to PCs for digital modes. It does work with the
small speakers as well. Builders with the earlier versions can
try this audio amplifier as an outboard amplifier.
2. The audio thump issue during T/R switching has been
fixed.
3. At 28 Mhz, the output is about 4 watts. (this involves a
single capacitor change from the
earlier PCB).
4. I have included some 'jump' points to add interesting
stuff like CW filters to the board. There are a large number
of test points to help you debug and understand the board.?
All in all, the changes are 'backward compatible' . That
is, you can hack these changes to the previous boards to get
in the new functionality. I have updated the circuit diargrams
on .
The earlier board's circuit diagram has moved to?
The bad news is that we had to bump up the price of the
board by 20 dollars. We fought long and hard to keep the price
down. My personal ambition was to keep the price inside (or
at) $100. This is price rise has to do with three things : The
recent changes in the Indian import duty and sales tax; Our
own increasing costs to preorder the parts. Lastly, we also
increased our payout to those who wind the coils, assemble and
test the boards. They were working at the same rate for the
last two years. It was about time.?
The new boards cost $129 USD with shipping. $139 USB with
DHL option.?
The good news is that from now on, these boards will be
available on order. The waiting queue is gone.
On a personal note, I am happy with the new audio. It is so
much sweeter and cleaner on the headphones.? Far less fatigue
after hours of CW work. I am also using the FT8 extensively, I
have bagged almost twenty countries, testing the new firmware.
- f
--
Ron W7HD - NAQCC#7587 OMISS#9898 KX3#6966 LinuxUser#415320
Editor OVARC newsletter
|
Re: KD8CEC uBITX firmware 1.071
#ubitx
... the download link on Github only had the 1.08 version available. If, at , you click the "releases" link just above the red line above the green "clone or download" button, you get the prior releases. This is a direct link: Daniel KB3MUN
|
Re: KD8CEC uBITX firmware 1.071
#ubitx
|
I have one of those cases, bought is specifically with the uBITX in mind. The case is great value. A tight fit-- they have a larger version, also a good value.
I may use the non-waterproof "Aluminum" case 69316 because it might be possible to put the uBITX in the bottom half, and squeeze a Raspberry Pi and display in the top half.?
Tom, wb6b
|
KD8CEC uBITX firmware 1.071
#ubitx
I am having trouble with the 1.8 firmware calibrating the unit. LSB and USB are reversed no matter what I do.
I have been told that the older 1.071 version did not have this problem and I very much would like to give that a try. However the download link on Github only had the 1.08 version available. There is a Google drive with the HEX file but that is not what I am looking for.
Does anyone have the software package for me ?-)
Thanks!
Rogier
|
Re: The new uBITX boards are here
This sounds very good, I should have waited a couple of weeks before I ordered mine now I will have to order ?another one (was going to anyway). Hope to see new schematic ?and pictures ?soon.
--
Allen ?Merrell
|
Great!
I'll? be checking emails and such, so will stay in touch.?
|
Re: The new uBITX boards are here
How about a picture showing the new test points?
Still waiting for the deluxe CQ hall of famer collector's edition...
--
|
You should go way-way back, Clark, to find true log rotary potensiometers.
Vacuum tube era, when power amplification was voltage related.
They were also higher value units, typically 47 to 100 KOhms, as far as I remember.
Then came the transistor, a current amplification device.
Using a tube log pot in a transistor circuit was something equivalent to a rollercoaster ride in sound (I know first hand).
Succeded by low impedance linear pots, or dual slope linear ones for closer correlation of angular position to output sound level.
Linear (long) throw faders* was another story until VCAs where established.
(*) Penny & Giles faders were the most expencive part in a pro console.
73 Nikos
|
Re: The new uBITX boards are here
What capacitor was changed to what value?
Ron W7HD
On 05/26/2018 12:19 PM, Ashhar Farhan
wrote:
Peeps,?
HF Signals has rolled out the new (r4) version of the PCBs.
Here are the changes:
1. A new, low distortion audio amplifier made from discrete
transistors. This is one is optimized for head-phones and
connecting to PCs for digital modes. It does work with the
small speakers as well. Builders with the earlier versions can
try this audio amplifier as an outboard amplifier.
2. The audio thump issue during T/R switching has been
fixed.
3. At 28 Mhz, the output is about 4 watts. (this involves a
single capacitor change from the
earlier PCB).
4. I have included some 'jump' points to add interesting
stuff like CW filters to the board. There are a large number
of test points to help you debug and understand the board.?
All in all, the changes are 'backward compatible' . That
is, you can hack these changes to the previous boards to get
in the new functionality. I have updated the circuit diargrams
on .
The earlier board's circuit diagram has moved to?
The bad news is that we had to bump up the price of the
board by 20 dollars. We fought long and hard to keep the price
down. My personal ambition was to keep the price inside (or
at) $100. This is price rise has to do with three things : The
recent changes in the Indian import duty and sales tax; Our
own increasing costs to preorder the parts. Lastly, we also
increased our payout to those who wind the coils, assemble and
test the boards. They were working at the same rate for the
last two years. It was about time.?
The new boards cost $129 USD with shipping. $139 USB with
DHL option.?
The good news is that from now on, these boards will be
available on order. The waiting queue is gone.
On a personal note, I am happy with the new audio. It is so
much sweeter and cleaner on the headphones.? Far less fatigue
after hours of CW work. I am also using the FT8 extensively, I
have bagged almost twenty countries, testing the new firmware.
- f
--
Ron W7HD - NAQCC#7587 OMISS#9898 KX3#6966 LinuxUser#415320
Editor OVARC newsletter
|
Re: The new uBITX boards are here
I looked on , specifically at? and the schematic it shows it still v3,?.
toggle quoted message
Show quoted text
On May 26, 2018, at 12:19 PM, Ashhar Farhan < farhanbox@...> wrote:
Peeps,?
HF Signals has rolled out the new (r4) version of the PCBs. Here are the changes:
1. A new, low distortion audio amplifier made from discrete transistors. This is one is optimized for head-phones and connecting to PCs for digital modes. It does work with the small speakers as well. Builders with the earlier versions can try this audio amplifier as an outboard amplifier. 2. The audio thump issue during T/R switching has been fixed. 3. At 28 Mhz, the output is about 4 watts. (this involves a single capacitor change from the earlier PCB). 4. I have included some 'jump' points to add interesting stuff like CW filters to the board. There are a large number of test points to help you debug and understand the board.?
All in all, the changes are 'backward compatible' . That is, you can hack these changes to the previous boards to get in the new functionality. I have updated the circuit diargrams on . The earlier board's circuit diagram has moved to?
The bad news is that we had to bump up the price of the board by 20 dollars. We fought long and hard to keep the price down. My personal ambition was to keep the price inside (or at) $100. This is price rise has to do with three things : The recent changes in the Indian import duty and sales tax; Our own increasing costs to preorder the parts. Lastly, we also increased our payout to those who wind the coils, assemble and test the boards. They were working at the same rate for the last two years. It was about time.?
The new boards cost $129 USD with shipping. $139 USB with DHL option.?
The good news is that from now on, these boards will be available on order. The waiting queue is gone.
On a personal note, I am happy with the new audio. It is so much sweeter and cleaner on the headphones.? Far less fatigue after hours of CW work. I am also using the FT8 extensively, I have bagged almost twenty countries, testing the new firmware.
|
It will work but for best results it should be a log (AKA audio) taper, not linear. If you can’t tell, hook up an ohmmeter to the wiper and either end, set the pot to the midway point. The meter should NOT read around 2.35K ohms. It’s hard to say what the proper value for a log pot is, it depends on which side of the pot is connected and I don’t know the formula for resistance vs shaft position off hand.
Clark Martin
KK6ISP
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Show quoted text
On May 26, 2018, at 8:48 AM, brad martin <emclinux@...> wrote:
I see that the ubitx uses a 10k pot for the volume but I can’t seem to find a good knob for it. I do however have a 4.7k pot with a switch that has a more standard shaft size. Would I experience any ill effects by swapping the 10k for a 4.7k?
|
No, you won't face any surprises.
For the same reason I used a 4K7 /A (linear) I had with dual pole power switch.
Really a robust pot from another era.
Naturally, the AF IC was toasted, but this has nothing to do with the pot.
Replaced it with an equivalent type and works ok since.
I also hooked up an RCA terminated audio cable at the extremes of this pot in order to connect my ADC sound converter at a fixed audio level for digital work. The ADC is high impedance input, but none the less it is in parallel with the 4,7KOhms of the pot.
No loading problem to the preceding stages, Cleaner audio signal is a bonus.
73 Nikos
|
|
|
Re: The new uBITX boards are here
Hi,
There are references to 'New code' by various members of this group but the links all seem just descriptive. Can't see any 'Download Ver_xx here' on the sites.
I have mine built and tested as standard with the WX chip, but audio sounds good on earphones.
?
Peter Paul Fox G8HAV
Mid-Cheshire Amateur Radio Society
5 Llandovery Close
Winsford
Cheshire CW7 1NA?
Group Controller
Dane Valley?RAYNET?
Tel: 01606553401 (H)
Tel: 07919315547 (M)
toggle quoted message
Show quoted text
Peeps,?
HF Signals has rolled out the new (r4) version of the PCBs. Here are the changes:
1. A new, low distortion audio amplifier made from discrete transistors. This is one is optimized for head-phones and connecting to PCs for digital modes. It does work with the small speakers as well. Builders with the earlier versions can try this audio
amplifier as an outboard amplifier.
2. The audio thump issue during T/R switching has been fixed.
3. At 28 Mhz, the output is about 4 watts. (this involves a single capacitor change from the earlier PCB).
4. I have included some 'jump' points to add interesting stuff like CW filters to the board. There are a large number of test points to help you debug and understand the board.?
All in all, the changes are 'backward compatible' . That is, you can hack these changes to the previous boards to get in the new functionality. I have updated the circuit diargrams on
. The earlier board's circuit diagram has moved to?
The bad news is that we had to bump up the price of the board by 20 dollars. We fought long and hard to keep the price down. My personal ambition was to keep the price inside (or at) $100. This is price rise has to do with three things : The recent changes
in the Indian import duty and sales tax; Our own increasing costs to preorder the parts. Lastly, we also increased our payout to those who wind the coils, assemble and test the boards. They were working at the same rate for the last two years. It was about
time.?
The new boards cost $129 USD with shipping. $139 USB with DHL option.?
The good news is that from now on, these boards will be available on order. The waiting queue is gone.
On a personal note, I am happy with the new audio. It is so much sweeter and cleaner on the headphones.? Far less fatigue after hours of CW work. I am also using the FT8 extensively, I have bagged almost twenty countries, testing the new firmware.
- f
|
Re: RF power chain mods and improvements..
Sorry for the late reply (was traveling).? The MPSH10’s give a very flat profile up to about 60 MHz and beyond.? I’m struggling with the pre-driver(s) choice at the moment… Q92,Q93, Q96, Q97.? I’m waiting to hear how the 2N5109’s pan out.? They have a favorable fte for this service, and can make enough power to drive the RD parts in the PA fine.? I’m spending some time on the interstage transformer (T10) because I don’t believe it’s designed properly.? I replaced T11 with a BN61-002… a little overkill but extremely efficient.
?
?
Dr. William J. Schmidt - K9HZ
?
From: [email protected] [mailto:[email protected]] On Behalf Of Nick VK4PLN
Sent: Thursday, May 24, 2018 9:08 PM
To: [email protected]
Subject: Re: [BITX20] RF power chain mods and improvements..
?
Hi Dr William,
How is your radio performing with the mpsh10 and rd16hff1 ?
73.
?
|
Glad it went smoothly, and worked so well. I still have thousands
of parts left, so I probably can give the parts out for a few
years.
Howard
On 5/26/2018 2:07 PM, RowlandA wrote:
toggle quoted message
Show quoted text
I did the mod
(thanks Howard for the parts!) and here's what I got:
80M? 11W before 13W after
40M? 11W? ? ? ? ? ? ?14W
20M? 7.8W? ? ? ? ? ? 11W
17M? 4.7W? ? ? ? ? ? 6.8W
15M? 4.0W? ? ? ? ? ? 5.6W
12M? 3.0W? ? ? ? ? ? 5W
10M? 2.5W? ? ? ? ? ? 4.3W
My test was using the Tune button in WSJT-X, and a dummy load.
I applied the parts the same way the Nigel G4ZAL did, including
the tee-pee'd inductor to R86.? This was my first excursion into
SMD soldering; I used a headband with a drop-down magnifier and
LED light, and seeing the parts was easy.? Actually the whole
process was a lot easier than I expected.??
73,
Rowland K4XD
|
Re: The new uBITX boards are here
I just picked one up thanks, wanted a second ubitx anyway.
Still the best value @129.00 absolutely.
Thank you!!
Laurence
toggle quoted message
Show quoted text
On Sat, May 26, 2018 at 3:19 PM, Ashhar Farhan <farhanbox@...> wrote: Peeps,
HF Signals has rolled out the new (r4) version of the PCBs. Here are the
changes:
1. A new, low distortion audio amplifier made from discrete transistors.
This is one is optimized for head-phones and connecting to PCs for digital
modes. It does work with the small speakers as well. Builders with the
earlier versions can try this audio amplifier as an outboard amplifier.
2. The audio thump issue during T/R switching has been fixed.
3. At 28 Mhz, the output is about 4 watts. (this involves a single capacitor
change from the earlier PCB).
4. I have included some 'jump' points to add interesting stuff like CW
filters to the board. There are a large number of test points to help you
debug and understand the board.
All in all, the changes are 'backward compatible' . That is, you can hack
these changes to the previous boards to get in the new functionality. I have
updated the circuit diargrams on www.hfsignals.com. The earlier board's
circuit diagram has moved to
The bad news is that we had to bump up the price of the board by 20 dollars.
We fought long and hard to keep the price down. My personal ambition was to
keep the price inside (or at) $100. This is price rise has to do with three
things : The recent changes in the Indian import duty and sales tax; Our own
increasing costs to preorder the parts. Lastly, we also increased our payout
to those who wind the coils, assemble and test the boards. They were working
at the same rate for the last two years. It was about time.
The new boards cost $129 USD with shipping. $139 USB with DHL option.
The good news is that from now on, these boards will be available on order.
The waiting queue is gone.
On a personal note, I am happy with the new audio. It is so much sweeter and
cleaner on the headphones. Far less fatigue after hours of CW work. I am
also using the FT8 extensively, I have bagged almost twenty countries,
testing the new firmware.
- f
|
Skip Davis
kj6etl
K9HZ
