Two Tone Generator #two-tone


K5ESS
 

As mentioned in a previous posts by Farhan and Raj there is an online generator that can provide two tones for testing.  http://www.onlinetonegenerator.com/binauralbeats.html.
However if you would like to build your own there is an article in the latest QEX by Phil Salas AD5X describing a two tone generator fabricated from two Wien bridge oscillators that are available from Ebay.  I've put together a PDF that describes the generator for those that might want to build one but don't have access to QEX.
Mike
K5ESS


Ashhar Farhan
 

The often neglected requirement of a two tone generator is that it should have very very low distortion of its own. 
Let's imagine that you have a 2 tone generator with 1% distortion. This would be considered modestly good in audio work. However, this distortion in power terms is just -40dbc. Effectively, you will not get any useful measurements beyond about -35 dbc.
The modern sound cards on laptops are equipped with 24-bit sound cards that have more than 16 bits of useful range. They can generate very clean audio.
- f

On Sun 31 Mar, 2019, 12:23 AM K5ESS via Groups.Io, <k5ess.nothdurft=verizon.net@groups.io> wrote:
As mentioned in a previous posts by Farhan and Raj there is an online generator that can provide two tones for testing.  http://www.onlinetonegenerator.com/binauralbeats.html.
However if you would like to build your own there is an article in the latest QEX by Phil Salas AD5X describing a two tone generator fabricated from two Wien bridge oscillators that are available from Ebay.  I've put together a PDF that describes the generator for those that might want to build one but don't have access to QEX.
Mike
K5ESS


bobolink <rwhinric@...>
 

The often neglected requirement of a two tone generator is that it should have very very low distortion of its own. 
I don’t get QEX but wonder what method he used to measure the distortion of his circuit. I think the HP334A was useful for that (THD I guess). They still want quite a high price for them on eBay.


K5ESS
 

He used a digital oscilloscope with FFT capability.  Claims that with adjustment, harmonic content is below -50 dB.

Mike

K5ESS

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of bobolink
Sent: Monday, April 1, 2019 7:16 AM
To: BITX20@groups.io
Subject: Re: [BITX20] Two Tone Generator #two-tone

 

The often neglected requirement of a two tone generator is that it should have very very low distortion of its own. 

I don’t get QEX but wonder what method he used to measure the distortion of his circuit. I think the HP334A was useful for that (THD I guess). They still want quite a high price for them on eBay.


 

Hi,

There are many free Android apps that will generate whatever tones you want.

On desktops and laptops, the Linux program "Audacity" is very good for making whatever tones you want too.  It will also do very nice spectrum analysis of audio input from your rig (for viewing filter passband shape so you can set your BFO correctly).

73,


Mark.