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Re: Wire-up (Almost) Done #bitx40

Pat Anderson
 

No Radio Shacks around here either, I just search Amazon for "project box." This one seemed to be about the right size. Do you think taking the PA and Raduino grounds to the ground tab on the BNC rather than the ground on the power socket will be OK?


On Thu, Mar 14, 2019 at 2:21 AM Vic WA4THR via Groups.Io <vhklein=[email protected]> wrote:
Nice! That is an interesting housing selection, it has been so long since we had a Radio Shack around here that I did not recall they had a case big enough. I used to get all sorts of cases, plastic and metal, at the shack.

After you get it running, you may want to upgrade the software to Allard's version. It helps the tuning and reduces the clicking a lot.

=Vic=

Re: Xiegu agc board

 

Its possible to use with a uBITX - but here is the complexity -- need to replace the 12 MHz IF bidirectional amplifier with that board, a separate board on transmit -- and 2 switches.? a few have actually done this.?

I am finding just being able to attenuate the S9 and higher signals is delightful.? Try the ND6T circuit (I honestly think my problem was connecting it improperly maybe) - two versions available.? I am now thrilled with the VK3YE solution that I have installed.? Neither of these come pre-assembled at the moment, but each uses very few parts so these can be homebrewed.?

Meanwhile one of those boards could be great in a homebrew receiver or transceiver, if you don't want to do the surgery on the ubitx (honestly this rig is so cool why not if you are willing).?

73 Curt
Re: Opinions on 510 replacement?

 

Hi Allison,

Yes -- I already replaced the 3904s with metal can 2222s and q90 with a bpf102 plus changed the resistors and stuff.? Great mod -- plenty of power!? Thank you for that!

What I'm wondering about now is the power fluctuation between bands.? ?If I adjust RV1 for each band I can get way more power out than required, but if I set it for say 7W on 40M, I'll get 10W on 80, 15 on some other band, etc.? ?What I'd like to do is 5-7 on all bands.
Re: Opinions on 510 replacement?

 

The hugest mod for me -- reducing the CW sidetone volume.? Wow - this I hear each time I use the rig.?

Spurs, well I don't notice them myself !? Still I addressed this with a relay board and LC filter - looking forward (I think) to measurement to see if it works!?

On output power? - there is both what your S-meter shows and what makes contacts -- a small change in output power (< 25%) just isn't worth a huge effort.? Each S-unit is supposed to be 6 dB, even if its 4 dB on a rig -- the PA mods just don't have that big of a jump.?

AGC -- been fun to not have to touch the volume control for S9+ signals any more.? Playing with a meter circuit to show me what AGC is doing, although might be easier to observe the LED in the circuit (no I wired up a meter anyway).?

audio filter.? NESCAF is doing it, my rig hears as well as my other rigs on CW or SSB.?

when you run out of mods - time to play with a new rig maybe.? or maybe integrate in a digital mode capability direct from USB.? have fun with mods you will notice!?

73 Curt
Re: Opinions on 510 replacement?

 

Brutus,

Changing the IRF510s will not fix the issues.? They can easily do good power and gain to past 6M
but the rest of the amp can't.? The last things I'd change is the IRF510s and the RD parts cost about
10X and if you lucky you might get something for the cost.

To get power out of the finals you need drive and its not there as the 3904s can't do it and
at 20m and up they have limited (and decaying with increasing frequency) gain.

This is all in the wiki.

Allison
Re: Balanced Mixer Audio Input Impedance

 

Tom,

That last post of yours is definitely a keeper!
Thanks!

Perhaps it's not obvious to all forum members why a 1 Watt peak AM phone signal must be
transmitting 0.25 watts of carrier with no modulation.? Reason being that that power
goes up with the square of the voltage.? The RF voltage into the 50 ohm antenna system
is zero on negative audio peaks, half way to the peak RF voltage with no modulation,
and at the peak RF voltage on positive audio peaks.? Half the peak RF voltage
is one quarter of the peak RF power.? (I'm assuming we have mike gain as high as
it can go without causing distortion in the transmitted AM signal..)

Here is Tom's key insight:

> The RF envelope of the transmitter modulated by the sideband modulator is
> almost like what the audio fed (through) a full wave rectifier would look like.
> The big difference is the phase of the RF carrier will be the opposite
> for the positive and negative parts of the audio waveform cycle. ?

Expanding on that a bit:?
Assume we just have a 50 ohm resistor to ground at the output of 2 diode modulator,
the modulator drives that resistor with a square wave of 12mhz, the square wave
is above ground at positive audio peaks, below ground at negative audio peaks.
That square wave is always at ground when the 12mhz local oscillator reverse biases
the diodes, the phase of the 12mhz LO at which this happens is always the same.
But due to the fact that the audio drive causes the peak of the square wave to be
positive or negative with respect to ground, we get phase reversals of the 12mhz
square wave out of the modulator at the audio rate.

The local oscillator port of this singly balanced modulator is "balanced",
so we get no 12mhz component coming through that does not get affected by this phase reversal.
However the audio port is not balanced, so the square wave into the 50 ohm resistor
is going above and below ground at the audio rate.? This low frequency component is easily
removed with a high pass filter,? passing only a 12mhz square wave that is centered about ground,
whose amplitude varies with the audio amplitude, and with a phase reversal at the audio rate.

I can sort of intuit how those phase reversals would balance out the 12.000mhz carrier.
But I think it is still a matter of following the math to understand how the phase reversals and amplitude variations?
result in two constant sidebands at 11.999mhz and 12.001mhz as seen on a spectrum analyzer.
(I'm assuming Tom's 1khz audio signal is driving the modulator.)

This gives some insight into how the EER system of generating an SSB can work..
? ??/g/BITX20/topic/29625421
However, EER is somehow generating single sideband, not double sideband.

With four diodes in a ring (as we find in the other two uBitx mixers), the mixer is doubly balanced
and that audio component would not be present in the mixer output.
Being symmetrical, and presenting a constant load to the audio port, those doubly balanced mixers
would be easier to analyze.? In particular, with a resistive 50 ohm load on the output of the mixer,
I can believe that the audio port would present a 50 ohm load to the mike amp as Allison suggested.?

Jerry, KE7ER



On Wed, Mar 13, 2019 at 10:45 PM, Tom, wb6b wrote:

Hi,

?

As a side note, this topic is interesting and thinking about it could lead to a somewhat intuitive understanding of sideband modulation (in this case double sideband) rather than the mathematical frequency mixing mystery that is usually presented.

?

Imagine a transmitter with a 1 watt peak output. It is interesting to observe is in AM modulation when no audio is presented the power output is 0.25 watts.? Lets say we modulate with a 1 Khz sine wave, with positive voltage increasing the transmitted output power. At the positive peak of the audio the power is 1 watt and the negative peak of the audio just drives the transmitter power to zero.?

?

So even with no modulation the transmitter is wasting 0.25 watts.

?

With the balanced mixer, when there is no modulation the transmitter is putting out zero watts. When the audio reaches the positive peak the transmitter (in this example) is putting out 1 watt.

?

However, when the audio reaches the negative peak, once again the transmitter is putting out 1 watt.?

?

So at zero modulation the sideband modulator of transmitting 0 watts verse 0.25 watts.?

?

The RF envelope of the transmitter modulated by the sideband modulator is almost like what the audio fed trough a full wave rectifier would look like. The big difference is the phase of the RF carrier will be the opposite for the positive and negative parts of the audio waveform cycle. ?

?

In this very special case, lets say the transmitter was transmitting on 1 Mhz. Lets say a receiver is trying to receive this signal and to do so it supplies a 1 Mhz reference to replace the carrier removed in the sideband modulation. And in this special case the 1 Mhz oscillator in the receiver just happens to be locked in phase with the original transmitter¡¯s 1 Mhz original carrier.?

?

Then with no modulation, the voltage the receiver might be supplying to a detector might be 0.5 volts.?

?

When the receiver receives the signal from the transmitter on the positive half of the audio waveform, the transmitter RF will be in phase with the 1 Mhz oscillator in the receiver and added together would increase the voltage sent to the detector.?

?

When the receiver receives the signal from the transmitter on the negative half of the audio waveform, the transmitter¡¯s RF will be out of phase with the 1 Mhz oscillator in the receiver, and ¡°added¡± together, the out of phase signal will decrease the voltage sent to the detector.?

?

The 0.5 volts, added to or subtracted from by the received transmitter¡¯s envelope strength and phase, becomes the audio that is heard.

?

Leave it to the fancy math to quantify the power in the envelope and power not wasted in the carrier, and how all this can be explained as sidebands around a carrier that once was. But the idea that the transmitter is not constantly sending 0.25 watts, but only sending a signal when there the modulation, telling the receiver how much to increase or decrease the ¡°carrier¡± signal being keep locally in the receiver, may somewhat explain the efficiency gain from the transmitter not needing to transmit the carrier; as in SSB.

?

Of course in the real SSB system the receiver¡¯s local carrier oscillator in not necessarily in exact phase and frequency, and additionally one of the two sidebands is removed. Outside of this special case the math is a more reliable choice as the basis of designing SSB radios and balanced modulars.

?

Tom, wb6b
Re: Opinions on 510 replacement?

 

I favor that approach as well, if for no other reason than cheapness . Lol.? The other replacements served a purpose.

I guess what I'm wondering is if replacing those would make it so there's no need to do an rv1 mod.? But if not I'll just leave them.??

I love this little rig.? The coolest thing since sliced bread!
Re: Opinions on 510 replacement?

 

If you wamt to replace just for sake of replacement, no comment. Otherwise, just enjoy using the rig.

One of my contemporary late om Rajan (vu2knn) used to comment that " a sleeping dog and a working rig shoul not be disturbed".

On Thu, 14 Mar 2019, 6:49 pm Brutus Laurentius <markhamfarm14@... wrote:
I have a v4 . Did lots of mods -- replaced the relays, l5/l7, if transistors, driver transistors (and related r changes etc), put a t filter in place of r27.??

Rv1 can be adjusted to give plenty (maybe even way too much) power out on all bands .?

Before a do a mod to adjust drive based on band, I am wondering if at this point there's a benefit to replacing the finals, and if so, whether the rd15 or rd16 is a better choice?

Thoughts?

Brand new unbuilt V4 for sale #bitx40

 

Hi?all,

I¡¯m simply not finding the time to build and modify this kit.?

Still sealed in the original box. Needs a good home. $100 and its yours. I¡¯ll pay ground shipping in the US.?

Or make a reasonable offer.?

73s Dave W7BOT
Re: Xiegu agc board

 

There's a nice list of agc boards and mods for the ubitx here:?https://ubitx.net/category/agc-mod/
Re: Broadcast Interference filter for Ubitx

Laurence Oberman
 

Thanks Gary and Skip

On Thu, Mar 14, 2019 at 9:13 AM Gary Anderson <gary.ag5tx@...> wrote:

A quick look at the V5 schematic (relay changes over v3 and v4), it appears that the K3 relay pinout numbers now match standard relay pinout numbers (coil on 1,16). The K1 relay has not been updated in the schematic (old numbering scheme). It's not a big deal, if you are aware of it. K1 is drawn differently too (still the old way). It might be at first confusing to those that don't have tribal/historical knowledge and engage on V5.

Anyways, insert the BCI filter in the receive path board trace between K1 "pin 12" and K3 as Skip highlighted. (K3 no longer has a "pin 14", rather a "pin 11")

Rgds,
Gary
Re: Xiegu agc board

Jimmy Capizzi
 

dang! i ordered one too hoping it would work on my bitx40.....
Opinions on 510 replacement?

 

I have a v4 . Did lots of mods -- replaced the relays, l5/l7, if transistors, driver transistors (and related r changes etc), put a t filter in place of r27.??

Rv1 can be adjusted to give plenty (maybe even way too much) power out on all bands .?

Before a do a mod to adjust drive based on band, I am wondering if at this point there's a benefit to replacing the finals, and if so, whether the rd15 or rd16 is a better choice?

Thoughts?
Re: Broadcast Interference filter for Ubitx

 

A quick look at the V5 schematic (relay changes over v3 and v4), it appears that the K3 relay pinout numbers now match standard relay pinout numbers (coil on 1,16). The K1 relay has not been updated in the schematic (old numbering scheme). It's not a big deal, if you are aware of it. K1 is drawn differently too (still the old way). It might be at first confusing to those that don't have tribal/historical knowledge and engage on V5.

Anyways, insert the BCI filter in the receive path board trace between K1 "pin 12"? and K3? as Skip highlighted.? (K3 no longer has a "pin 14", rather a "pin 11")

Rgds,
Gary
Re: How to get 5W on 10m?

 

What about adding a small cap, say from 180 to 330pf across R911, R96, R941 and R942 to add a little bit more PWR on the higher bands (15-12-10m)?


Il 09/mar/2019 17:16, "iz oos via Groups.Io" <and2oosiz2=[email protected]> ha scritto:

Thanks Arv, I will try it! I had installed under Linux via wine so following your hints I can start with it!


Il 09/mar/2019 15:46, "Arv Evans" <arvid.evans@...> ha scritto:
Iz Oos

Using LTSpice is not all that difficult (I learned it and I'm not that brilliant).

There are two parts to learn.? First is the schematic editor that is intuitive once you know some basic select-and-place moves.? After you have the schematic complete you would select voltage sources and measuring points.? The rest is mostly automatic when you select "RUN" mode.

Start with a small circuit segment to get a feel for how it works and then build on that experience.? In a few hours you will be an expert.

LTSpice is FREE and will run on Windows or any version of Linux with Wine installed.??

Arv
_-_


Sent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------
From: iz oos <and2oosiz2@...>
Date: 3/9/19 12:04 AM (GMT-07:00)
Subject: Re: [BITX20] How to get 5W on 10m?

What about adding a capacitor (like a 180pf or maybe a higher value) in parallel with r83? Would it increase the 10m power output without decreasing the output in the other bands (I wish I knew how to use LTspice)?


Il 02/mar/2019 11:47, "iz oos via Groups.Io" <and2oosiz2=gmail.com@...o> ha scritto:

I replaced the cap at the emitter of Q90 with a 470pf instead of the 0.1nF. In the meanwhile I replaced the bifilar antenna wire with a short coax. Output power on 40 marginally diminished from 15 to 12.5w about. The power on higher bands marginally increased from nearly 2w to nearly 2.5w. But the 'instability' issue with full throttle noise on SSB on 10m has disappeared and I can also not attenuate the Vogad output. Overall I am happy with this one component replacement.


Il 01/mar/2019 08:40, "iz oos via Groups.Io" <and2oosiz2=gmail.com@...o> ha scritto:

Thanks for all the replies. According to the old schematics of my ver. 3 ubitx C81 should be 0.1nF, so I will see what changes with a 470pf as suggested by Farhan.


Il 28/feb/2019 23:58, "ajparent1/KB1GMX" <kb1gmx@...> ha scritto:
BITX V5 as distriibuted.? I believe its part of the Zip file on github.
Here is a copy attached.

As far as power amp there were no changes and is the same for emitter cap (c81) on Q90
going back to V3.

Allison

Re: Maximum and minimum voltages for uBitX V5?

 

John

nice work!? I suggest not getting too fancy, and its not a huge difference between 12 and 13.8 volts.? the latter gives a fraction of an S-unit more transmit power and a little more heating in the 5 volt regulator feeding the raduino.?

much fun to be had in customizing (or even less so than the max) to make the rig what you want.? I may be a bit counter-culture in not wanting a 'high current' display - as I mostly care for the receive and transmit functions!?

some folk are running the PA at a higher bias voltage - and there is already a split 'bus' in the board design to facilitate this.?

73 Curt
Re: Maximum and minimum voltages for uBitX V5?

 

Answering part of my own post. ?

The LM386 in my V5 unit is from UTC (Unisonic Technology Corp) and the absolute maximum voltage is 15 volts. ?It should be OK on most "12 volt" supplies which are often 13.8 volts.

Solar power from a 12 volt system using flooded lead-acid batteries might be a problem as some of the flooded batteries have an equalization charge of more than 15 volts (varies by manufacturer, with a series pair of Trojan T-105s having an equalization voltage of 15.5).
Re: CEC< 1.122 For V5 CW BFO adjustment

 

Vic,

?I was trying to do all of this with the Nextion screen and didn't even think of the Memory manager program. I will give that a try.

Thank you!

73's
Mike WA3O
Re: Wire-up (Almost) Done #bitx40

 

Nice! That is an interesting housing selection, it has been so long since we had a Radio Shack around here that I did not recall they had a case big enough. I used to get all sorts of cases, plastic and metal, at the shack.

After you get it running, you may want to upgrade the software to Allard's version. It helps the tuning and reduces the clicking a lot.

=Vic=
Re: CEC< 1.122 For V5 CW BFO adjustment

 

Assuming you are using the Memory Manager, you need to check the box for CW receive offset. Then you will transmit on the displayed frequency when in CW.



=Vic=

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