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Re: Adding speech compression.

 

Should work as expected if you increase the gain of the microphone amp: ?/g/BITX20/message/24437

Assume you raise the signal coming out of the microphone amp by 3dB (double the power). ?Assume the diodes conduct pretty severely on any voice peaks, and reduce them by a factor of 2, so your peak power into the crystal filter is back down to where you started out. ?But the quieter parts of your voice (for those of us that have any) have not been clipped back, and remain at twice the power. ?


On Sat, Apr 8, 2017 at 11:14 am, John Smith wrote:

I showed the schematic from Allard to someone, and he said the two diodes are shorting the AC signal to ground, and would result in a lower quieter signal.

?
Re: ubitx - stop press

 

This was always tricky when building multiband homebrew, that's why many went for single band design, building up a bank of boxes one for each band.

Good luck Ashhar.

73 Steve


G1KQH
Re: Adding speech compression.

 

I listened to it. Everything I have read and heard, all are the same. It's great to help being heard through QRN or QRM, There are different ways to do it like audio clipping or RF clipping. And lots of caution about using it poorly, or it amplifies all room noise, or so and so forth.

Bottom line- If you got it, try it. If it helps, great. Otherwise, leave it alone.

I showed the schematic from Allard to someone, and he said the two diodes are shorting the AC signal to ground, and would result in a lower quieter signal.

It's still a mystery to me how that would work. I am going to try out that circuit I posted a link to when I get the transistor it uses. Or maybe sub the part.?
Re: ubitx - stop press

 

Ash,

I'm still gathering parts for my first build of your uBitX (and your Specan!) and have not even started to draw the boards, so adding filters and tweaking the code for switching bands appears trivial.

" . . . replaced the two filter harmonic filters with four filters . . . it works."

You saved us some grief and perhaps FCC fines by telling us about your tests. We grumble, we complain, and we argue, but I believe most of us are having fun and accidentally learning some good stuff along the way.

Other than encouraging fellow hams to purchase from HFSigs, let us know how we can help you.

73 de w9ctw
Re: ubitx - stop press

 

i have measurer the input impedance of these stages to be appox 50 ohms when terminated in the 220 resistor in the output. i made these measurements with a homemade return loss bridge and the sweeperino.?
the original wes/kopski amps uses separate resistors for bias and feeback, i used just one. if you want to experiment with different feedback resistors while keeping the bias the same, you could use the original block.
the noise figure should be 14 db. i say that because i havent measured it. i do not have calibrated noise source. this figure is based on the accumulated (measured) losses of the lpf, first mixer and the first if amps figure of 6 db.
connecting the antenna brings up the noise on all bands at my qth. i must, though admit that i havent had any contacts in 28 mhz at all.
- f

On 8 Apr 2017 7:52 p.m., <selfy.dtp@...> wrote:
Farhan,

Let me first thank you for the projects and experience?you share with us. I am interested to find out how uBITX behaves in terms of selectivity and sensitivity?

I also support the idea, that if you want to cover all HF band a set of (at least) four LPF for the PA is a must.

Additionally, looking at the uBITX schematic, I couldn't?help but notice the bidirectional amps slightly differ form the original idea of W7ZOI and K3NHI. You used different?biasing approach, but it appears the input impedance is not 50 ohms. My LTSpice simulations?show 90 ohms at 10MHz and 50 ohms at 45MHz. And the "gain" transistor is biased at 15mA. Would you, please, share with us what your idea was for doing these mods.

73 de LZ1NEF
Re: ubitx - stop press

philip yates
 

Wow... Impressive, cannot wait for this.

Am following closely the uBitx. Better get space cleared for it.

Thanks Ashhar


Phil-G7BZD
Re: ubitx - stop press

 

with the 4 filters you get 3.5, 5, 7,10,14,18,21,24.9 and 29 mhz

- f

On 8 Apr 2017 5:05 p.m., "philip yates" <phil@...> wrote:

How many bands will this cover, and does selecting 80m rather than 40m make a difference.

Still very interested.


Phil G7BZD
Re: uBitx Prototype (PCB)

Jack Purdum
 

The cost of what I call Beta Boards is pretty high, as Jerry points out. However, once the design is set, the costs fall dramatically. I ordered 200 small boards (2"x3") at about $1 each for a recent project. These were similar to the quality seen in the Forty-9er assembly manual (www.farrukhzia.com/k2zia). I would think that boards made for SMD's would cost less, but I don't know as I have not purchased any.

Jack, W8TEE


From: Jerry Gaffke via Groups.Io <jgaffke@...>
To: BITX20@groups.io
Sent: Saturday, April 8, 2017 11:03 AM
Subject: Re: [BITX20] uBitx Prototype (PCB)

OSHpark is the best I've seen on small runs: ?
For $5 per square inch, you get three double sided boards with soldermask and silk at 6 mil design rules. ?The BItx40 at 4.5x5 inches would cost $5 * 4.5*5 = $112.50, or $37.5 per board. ?But the bidi amps are one square inch each, so could get three of them for a total of $5.
Could go to 0805 or 0603 or 0402 parts to drastically reduce the size of the Bitx40 (or uBitx). ?Take a look at 0201's if you are especially cheap and masochistic, but then you'll want access to a good binocular microscope.

On Sat, Apr 8, 2017 at 06:56 am, Jack Purdum wrote:
Finally, you could have a thru-hole board manufactured. I've done this with the Forty-9er and antenna analyzer project and if you have enough boards done, the cost isn't that bad.
?
Re: uBitx Prototype (PCB)

 

OSHpark is the best I've seen on small runs: ?

For $5 per square inch, you get three double sided boards with soldermask and silk at 6 mil design rules. ?The BItx40 at 4.5x5 inches would cost $5 * 4.5*5 = $112.50, or $37.5 per board. ?But the bidi amps are one square inch each, so could get three of them for a total of $5.

Could go to 0805 or 0603 or 0402 parts to drastically reduce the size of the Bitx40 (or uBitx). ?Take a look at 0201's if you are especially cheap and masochistic, but then you'll want access to a good binocular microscope.


On Sat, Apr 8, 2017 at 06:56 am, Jack Purdum wrote:

Finally, you could have a thru-hole board manufactured. I've done this with the Forty-9er and antenna analyzer project and if you have enough boards done, the cost isn't that bad.

?
Re: ubitx - stop press

 

Have you tried using the Mitsubishi RD16HHF1? ?

Thanks

Burton Ison
W5IAC




On Friday, April 7, 2017 11:59 PM, Ashhar Farhan <farhanbox@...> wrote:


peeps,

i did some more testing of the ubitx with the homebrew specan (as opposed to the rigol), i have some good news, bad news and good news.

1. good news : the homebrew specan does a better job than the rigol.

2. bad news : the specan revealed that the even order transmit harmonics will go down below -40dbc only if we carefullly balance the bias current between the IRF510s. it is very touchy. i can't see how anyone can get it right without a spectrum analyzer

4. good news : i have replaced the two filter harmonic filters ?with four filters. that also means, two more relays. it is more complicated, i know. but at least, it works.?

for those who want fewer bands (choose between 3.5 mhz and 7 mhz for the lower filter and 14 mhz and 28 mhz for the upper band), or they are alright to use external tx filters, the current design will do. for those who want all in one, wait a few days for me to update the ubitx page.

- f
Re: ubitx - stop press

 

Farhan,

Let me first thank you for the projects and experience?you share with us. I am interested to find out how uBITX behaves in terms of selectivity and sensitivity?

I also support the idea, that if you want to cover all HF band a set of (at least) four LPF for the PA is a must.

Additionally, looking at the uBITX schematic, I couldn't?help but notice the bidirectional amps slightly differ form the original idea of W7ZOI and K3NHI. You used different?biasing approach, but it appears the input impedance is not 50 ohms. My LTSpice simulations?show 90 ohms at 10MHz and 50 ohms at 45MHz. And the "gain" transistor is biased at 15mA. Would you, please, share with us what your idea was for doing these mods.

73 de LZ1NEF
Re: uBitx Prototype (PCB)

Jack Purdum
 

I agree that a Muppet board would be a great way to go, since it moves away from drilling holes. The only way I've had any success with thru-holes was when a friend availed his drill press for me to use. Plus, I went through drill bits like crazy...probably not the best bits and I seem to lack the patience for slowly drilling holes. Also, depending on how the board is laid out, you could use SMD's or standard components. Finally, you could have a thru-hole board manufactured. I've done this with the Forty-9er and antenna analyzer project and if you have enough boards done, the cost isn't that bad.

Jack, W8TEE


From: John Backo via Groups.Io <iam74@...>
To: BITX20@groups.io
Sent: Friday, April 7, 2017 11:39 PM
Subject: Re: [BITX20] uBitx Prototype (PCB)

Nice work, Jc.

I can see this as being easily made with automated equipment, but...
that's a lot of holes to drill at home. And all of them have to be precise.

Is it possible that a muppet style of board would work? I wonder since there are
so many traces on the bottom of the board... Maybe a more modular set of muppet boards?

Any idea of the production cost of this board?

john
AD5YE
Re: ubitx - stop press

 

Building for myself, I'd try leaving the extra filters out. ?Use an EFHW wire with a tuned impedance matching circuit. ?Though if mass produced, it really needs an output filter at the amp. ?Perhaps some holes in the board for either one band's worth of L"s and C's, ?or put socket pins into those holes and use plug-in filter boards. ?Can short across those holes with wires and use an external board with relays for a half dozen bands worth of filters, sell that as an option. ?Not too surprising, doubt anybody in the last 70 years has sold something that relies on such balance in a push-pull amp.?

I really have to build a basic spectrum analyzer. ? Perhaps just an Si5351 breakout board, a 50mhz lowpass filter, a level 7 mixer, a?PX1002 86.85mhz SAW filter, an MMIC gain stage, and an AD8310 into a Nano's ADC. ? ?Or do I need more gain stages for this to be useful? ?The PJRC 3.2 ARM has a 16 bit SAR ADC, maybe add a second mixer stage to create audio in the 20 to 50 khz range and analyze that in the ARM using DSP techniques.

Jerry, KE7ER


On Fri, Apr 7, 2017 at 09:59 pm, Ashhar Farhan wrote:

1. good news : the homebrew specan does a better job than the rigol.

?
Re: Lost all audio

 

She is alive again! ?I replaced the audio amplifier last night and she came right back to life. ?Thank you all for your help. ?
Re: Adding speech compression.

 

Speech Equalization, Compression and Processing

March 30, 2017


On Tue, Apr 4, 2017 at 12:26 PM, John VA7JBE via Groups.Io <va7jbe@...> wrote:

This has been an excellent conversation regarding clipping so far, but I feel that a little perspective might add to it further.? While the linked article does contain a good whack of opinion there's also some solid advice about how to talk into your microphone.? May it help you as it's helped me!
Re: ubitx - stop press

philip yates
 

How many bands will this cover, and does selecting 80m rather than 40m make a difference.

Still very interested.


Phil G7BZD
Re: ubitx - stop press

Rahul Srivastava
 

Hi! Farhan..

I guess your results hold true for other 510 PP amps as well when used with other exciters as well...!!!

Rahul VU3WJM
?


On Saturday, 8 April 2017 10:29 AM, Ashhar Farhan <farhanbox@...> wrote:


peeps,

i did some more testing of the ubitx with the homebrew specan (as opposed to the rigol), i have some good news, bad news and good news.

1. good news : the homebrew specan does a better job than the rigol.

2. bad news : the specan revealed that the even order transmit harmonics will go down below -40dbc only if we carefullly balance the bias current between the IRF510s. it is very touchy. i can't see how anyone can get it right without a spectrum analyzer

4. good news : i have replaced the two filter harmonic filters ?with four filters. that also means, two more relays. it is more complicated, i know. but at least, it works.?

for those who want fewer bands (choose between 3.5 mhz and 7 mhz for the lower filter and 14 mhz and 28 mhz for the upper band), or they are alright to use external tx filters, the current design will do. for those who want all in one, wait a few days for me to update the ubitx page.

- f
Re: USB/LSB operation

 

There are two ways to change fro USB to LSB and vice versa.

One is changing the BFO frequency from 19MHz (12+7) to 5 MHz (12-7).

The second is to change the BFO frequency in order to pick the 12MHz ladder filter to another side .... Assuming the filter width is 3khz .... (12,000 to 12,003)..the bfo can be set at 12.003 for one side and a12.00 for another (I use a switch, one inductor? and two trimmers) .... for the same frequency from the VFO.

73 from py2ohh miguel
Re: USB/LSB operation

 

This is just awesome thank you so much.

On Fri, Apr 7, 2017 at 5:10 PM, davetelling . <davetelling@...> wrote:

OK, here is where I am so far. I removed C91 and C92. I changed the 1.05 Raduino sketch by? adding code to read pin D7. In the original sketch, this was reserved for the TX/RX line monitor, which I don't use. You can use pretty much any other unused Arduino pin if you want. You also need to got through the code and remove references to that particular pin. Make sure you save your sketch under a new filename so as not to lose the original!!!

In the "setup" area, I made sure that pin D7 had the pullup enabled: pinMode(ULSB_SELECT,INPUT_PULLUP); (I #defined D7 as ULSB_SELECT previously)

Then, I added this code in the "loop" function:

if (digitalRead(ULSB_SELECT) == 1) /* if U/LSB switch is high, do LSB,
?if low, do USB */
{
? if (isUSB ==1)
? {
? isUSB = 0;
? setFrequency(frequency);
? updateDisplay();
? }
}
else
{
? if (isUSB == 0)
? {
? isUSB =1;
? setFrequency(frequency);
? updateDisplay();
? }
}

Finally, the little trick that allowed the displayed frequency to be correct for both LSB and USB: I modified this line in the setFrequency() function:

? if (isUSB){
??? si5351.set_freq((bfo_freq + f - 3100) * 100ULL, SI5351_CLK2);

The addition is the "- 3100" after the "freq + f". This keeps the displayed frequency the same, but shifts the actual VFO frequency to put the passband in the right spot.

Now - the caveat! I didn't have any definitive way to test this, as right now, I hear nothing on 7.076 (JT65 freq for 40m), even on the "big" radio. However, I took off the antenna connection of the bitx40, set my IC-718 to the lowest output I could, keyed it up in 7.150 MHz AM, and then tuned up & down from there on the bitx while trying both modes. In either mode, the frequency shift and volume of the received signal seemed to be pretty much the same, as I tuned up & down from the "center" frequency, certainly it should be pretty darned close! Hopefully, I'll see if I can hear some signals later & confirm the operation was a success!
Re: USB/LSB operation

 

This happens when the three wires of the volume control is wired wrongly.

Raj

At 08/04/2017, you wrote:

There's some sort of uncontrolled oscillation happening when I lower the volume control. I wish I understood why that was. Any comments about that?
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