Re: Audio pre-amplifier for microphone?

Ian Reeve

开云体育

Thx Nikos, I will take a look at the specifications of this, I tried one similar a while ago and found the gain far too much.Anything is worth a try,the modulation level on Ssb is far too low only producing around ,2 watts output on speech peaks.? Cheers. Ian M0IDR

Get

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From: [email protected] <[email protected]> on behalf of SV9CVJ Nikos <sv9cvj@...>
Sent: Thursday, August 22, 2019 12:28:08 PM
To: [email protected] <[email protected]>
Subject: Re: [BITX20] Audio pre-amplifier for microphone?

?

I use this ?? ? ? ....... analog output.

Re: Audio pre-amplifier for microphone?

#71274

I use this ?? ? ? ....... analog output.

Re: Audio pre-amplifier for microphone?

Ian Reeve

#71273

开云体育

Hi Tom,

?

Thankyou very much for pointing me towards this neat little circuit.

?

I have a dynamic mic insert so I will give it a go later today

?

Thx and 73

?

Ian M0IDR

?

Sent from for Windows 10

?

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From: [email protected] <[email protected]> on behalf of Tom, wb6b <wb6b@...>
Sent: Thursday, August 22, 2019 10:54:28 AM
To: [email protected] <[email protected]>
Subject: Re: [BITX20] Audio pre-amplifier for microphone?

?

On Thu, Aug 22, 2019 at 01:15 AM, Ian Reeve wrote:

how do you arrange a one transistor amplifier to work

Here is a possibility that was posted some time ago.

Tom, wb6b

Re: WSPR and APRS mobile

#71272

Ted

Check qrp-labs website. Some folk are launching expendable balloon payloads that go around the world. They offer a wonderful transmitter that does wspr called U3S. Even with 200 mW mine has reached VK, ZL and Antarctica.

Your ubitx should be a great wspr receiver. And psk31 etc. SSB voice will do better in the fall.

Curt

Re: Isolate any jacks/controls from metal chassis? #ubitx

#71271

On Wed, Aug 21, 2019 at 11:44 PM, iz oos wrote:

My front and back panels are plastic

Even though it has been considered the best practice to use metal chassis for RF designs (and sensitive audio or other types of sensitive projects), many modern designs include a very sound ground distribution on the PC board itself and often some kind of additional shielding via a conductive coating on the inside of the plastic case or other techniques. That being said, a large number of folks have built their uBitx transceivers into 3D printed or other plastic cases with remarkable success.?

Tom, wb6b

Re: Audio pre-amplifier for microphone?

#71270

On Thu, Aug 22, 2019 at 01:15 AM, Ian Reeve wrote:

how do you arrange a one transistor amplifier to work

Here is a possibility that was posted some time ago.

Tom, wb6b

Re: Audio pre-amplifier for microphone?

Ian Reeve

#71269

开云体育

The uBITX as it stands sends a positive voltage to the unit that sends the mic signal,how do you arrange a one transistor amplifier to work without a separate supply.I have tried and failed.Any help or a schematic would be great. Thx. Ian M0IDR

Get

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From: [email protected] <[email protected]> on behalf of Gordon Gibby <ggibby@...>
Sent: Wednesday, August 21, 2019 10:26:40 PM
To: [email protected] <[email protected]>
Subject: Re: [BITX20] Audio pre-amplifier for microphone?

?

A simple one transistor preamp makes a huge improvement, but don’t overdrive the amplifier!

On Aug 21, 2019, at 16:52, Neil Tolman via Groups.Io <k1nbt@...> wrote:

Has anyone used a mono pre-amp for the mic on the v5 uBITX?

Any thoughts or references would be helpful.

Thank you and 73,

Neil K1NBT

Re: Bitx40 very loud, high-pitched, low frequency noise

#71268

Woody, you got me thinking maybe it was just voltage, so i pulled out my adjustable bench supply and when I hooked it up at 12 V there was? a slight oscillation.? I stuck a 1000 MF cap crudely across the power leads and that oscillation ceased.? This the same the same BitX40 radio that runs quietly off my 12V battery, but goes operatic on my 13.8V rig supply.? So I think it is something about the impedance of the power supply.? I tried every voltage from 9V to 14V with the bench supply and 1000MF cap and it never broke back into oscillation.? Back on the 12V battery and no capacitor is needed.? There isn't a hint of oscillation.

Re: Isolate any jacks/controls from metal chassis? #ubitx

#71266

My front and back panels are plastic, all the rest is metal. So all connectors are isolated. I used a small piece of coax for the RF connection from the board to the panel instead of the stock twisted line. I think it is doing a good job as well. I chose this enclosure either because I had it for a long time, it was easy to drill and just to exclude the possibility of ground loops if any.

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Il 22/ago/2019 04:15, "Tom, wb6b" <wb6b@...> ha scritto:
>
> A metal chassis provides a very good low impedance ground reference to all the circuitry. Best to ground everything, including making sure the screws holding down the circuit board have a good connection to the chassis in all four corners.?
>
> The wires to each of the various jacks and controls should be fairly short and twisted together to reduce RF pickup within the metal box. Such as twisting the volume control wires in a set, the encoder in a set, microphone in a set, the antenna wires in a set. Best to let the antenna connector be at one side of the box, close to where the antenna is connected to the PC board, the power connector close to where it connects to the PC board, and the audio/digital at the other side. That would minimize the very slight possibility of the minimal ground loops (minimized by the low impedance of the chassis ground) having any effect. But the big common ground should be a benefit virtually in all cases.?
>
> Tom, wb6b

Re: raduino crystal question

#71264

On Wed, Aug 21, 2019 at 10:37 PM, Jerry Gaffke wrote:

Yes, the 25mhz crystal on the Raduino from hfsignals is throughole,
has a parallel capacitance of around 20pf.
That causes the reference oscillator to be off by a few hundred hertz,
but this is easily corrected by calibrating the frequency in software.

Jerry, KE7ER

On Wed, Aug 21, 2019 at 09:02 PM, <ashok.das81@...> wrote:

I am planning to build a clone of raduino. I needed to know what type of crystal is used in original raduino that used through hole parts. Si5351A datasheet says only smd crystals with capacitance less than 10pf are recommended, i am wandering what crystal raduino used ? I wanted to make using through hole crystal and no through hole crystal i could find having less than 10 pf capacitance. So can i make raduino using ordinary microprocessor crystals?

?Thanks KE7ER, thats enough for me to start building.? May I ask for some insight into calibration process ?

Regards
Ashok

Re: raduino crystal question

#71263

Yes, the 25mhz crystal on the Raduino from hfsignals is throughole,
has a parallel capacitance of around 20pf.
That causes the reference oscillator to be off by a few hundred hertz,
but this is easily corrected by calibrating the frequency in software.

Jerry, KE7ER

On Wed, Aug 21, 2019 at 09:02 PM, <ashok.das81@...> wrote:

Show quoted text

I am planning to build a clone of raduino. I needed to know what type of crystal is used in original raduino that used through hole parts. Si5351A datasheet says only smd crystals with capacitance less than 10pf are recommended, i am wandering what crystal raduino used ? I wanted to make using through hole crystal and no through hole crystal i could find having less than 10 pf capacitance. So can i make raduino using ordinary microprocessor crystals?

raduino crystal question

#71259

Dears,
I am planning to build a clone of raduino. I needed to know what type of crystal is used in original raduino that used through hole parts. Si5351A datasheet says only smd crystals with capacitance less than 10pf are recommended, i am wandering what crystal raduino used ? I wanted to make using through hole crystal and no through hole crystal i could find having less than 10 pf capacitance. So can i make raduino using ordinary microprocessor crystals?

Regards
Ashok

Re: Where many of the ICs we still use today were born.

jim

#71258

Someone posted about that (MC12) the other day ...maybe not here, but for all us (L)inux (USERS) ...it seem to load and run just fine on Wine ...Linux Mint 19.1 / wine packages from their repository ..

and thanks for posting about MicroCAP ..Ran ver 4 for years (cause thats all I could afford)

Jim

On Wednesday, August 21, 2019, 9:19:30 PM UTC, Graham <planophore@...> wrote:

speaking of SPICE and circuit simulations, another similar tool Microcap is now a free download. Seems the author has decided to retire or otherwise close shop and has made the tool freely available.

cheers, Graham ve3gtc

On 2019-08-21 04:10, Tom, wb6b wrote:

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HI,

This interesting article shows prototypes like I see in projects in this group, are like the test and development prototypes for many analog ICs. A look into the days before SPICE simulations became the standard.

Tom, wb6b

Re: Isolate any jacks/controls from metal chassis? #ubitx

#71257

A metal chassis provides a very good low impedance ground reference to all the circuitry. Best to ground everything, including making sure the screws holding down the circuit board have a good connection to the chassis in all four corners.?

The wires to each of the various jacks and controls should be fairly short and twisted together to reduce RF pickup within the metal box. Such as twisting the volume control wires in a set, the encoder in a set, microphone in a set, the antenna wires in a set. Best to let the antenna connector be at one side of the box, close to where the antenna is connected to the PC board, the power connector close to where it connects to the PC board, and the audio/digital at the other side. That would minimize the very slight possibility of the minimal ground loops (minimized by the low impedance of the chassis ground) having any effect. But the big common ground should be a benefit virtually in all cases.?

Tom, wb6b

Re: Bitx40 very loud, high-pitched, low frequency noise

#71253

I have a BitX40 that has the same issue.? When I run from a battery, the problem disappears.? . I tried lots of different bypassing caps with no luck.? ?As I prefer running it from a battery, it has not been a pressing issue

Re: Bitx40 very loud, high-pitched, low frequency noise

Woody

#71247

开云体育

The PC supply is also a switcher.? It may also require a "power good" signal to operate and a minimum load to work properly.
I recommend trying a linear regulated supply or battery for trouble shooting.? Your wall-wart switcher may work if the problem is gone with good pure DC if a big filter capacitor (like >1000 uf) and enough ferrite choke beads/sleeves are added to the feed line - and it is not dropping out of regulation.
Woody?

--

Re: Audio pre-amplifier for microphone?

Gordon Gibby

#71246

开云体育

A simple one transistor preamp makes a huge improvement, but don’t overdrive the amplifier!

On Aug 21, 2019, at 16:52, Neil Tolman via Groups.Io <k1nbt@...> wrote:

Show quoted text

Has anyone used a mono pre-amp for the mic on the v5 uBITX?

Any thoughts or references would be helpful.

Thank you and 73,

Neil K1NBT

Re: Where many of the ICs we still use today were born.

Graham

#71245

开云体育

speaking of SPICE and circuit simulations, another similar tool Microcap is now a free download. Seems the author has decided to retire or otherwise close shop and has made the tool freely available.

cheers, Graham ve3gtc

On 2019-08-21 04:10, Tom, wb6b wrote:

Show quoted text

HI,

This interesting article shows prototypes like I see in projects in this group, are like the test and development prototypes for many analog ICs. A look into the days before SPICE simulations became the standard.

Tom, wb6b

Audio pre-amplifier for microphone?

Neil Tolman

#71244

Has anyone used a mono pre-amp for the mic on the v5 uBITX?

Any thoughts or references would be helpful.

Thank you and 73,

Neil K1NBT

Re: Bitx40–Apollo Quindar Tones #bitx40

#71243

Hi Paul,

A local repeater uses a "roger beep". Personally, I find it annoying.

73,

Jim