I noticed that the CEC firmware has an SDR mode but this seems to be where the audio as as well are transmitted to the SDR and handled there.? Seems to be a good method for digital or recording but is there a way to just use the SDR as a waterfall display and still have the radio function as normal (i.e. have audio come out the radio speakers)?

Brad

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I have not tried it,but from the circuit description the first conversion is at 45 MHz.? I would try laying a short insulated wire near Q10.? You may even be able to tap off the emitter of q12 with a low value capacitor.?

Then tune the SDR ( I assume we are talking the about $ 15 TV dongle, but does not matter)? to around 45 MHz.??

There may be more out now, but the two that I bought a number of years ago, one goes from about 25 MHz up and the other starts at 50 some MHz.

de ku4pt

On Wed, May 30, 2018 at 3:06 PM, brad martin <emclinux@...> wrote:

I noticed that the CEC firmware has an SDR mode but this seems to be where the audio as as well are transmitted to the SDR and handled there.? Seems to be a good method for digital or recording but is there a way to just use the SDR as a waterfall display and still have the radio function as normal (i.e. have audio come out the radio speakers)?

Brad

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I think mine bottoms out at 52mhz but I can probably put the rf through the direct sample mod on the rtlsdr. I assume if I transmit that the RF is not going to go directly into the sdr as in the rf out is a different path

On Wed, May 30, 2018 at 3:42 PM Ralph Mowery <rmowery42@...> wrote:

I have not tried it,but from the circuit description the first conversion is at 45 MHz.? I would try laying a short insulated wire near Q10.? You may even be able to tap off the emitter of q12 with a low value capacitor.?

Then tune the SDR ( I assume we are talking the about $ 15 TV dongle, but does not matter)? to around 45 MHz.??

There may be more out now, but the two that I bought a number of years ago, one goes from about 25 MHz up and the other starts at 50 some MHz.

de ku4pt

On Wed, May 30, 2018 at 3:06 PM, brad martin <emclinux@...> wrote:

I noticed that the CEC firmware has an SDR mode but this seems to be where the audio as as well are transmitted to the SDR and handled there.? Seems to be a good method for digital or recording but is there a way to just use the SDR as a waterfall display and still have the radio function as normal (i.e. have audio come out the radio speakers)?

Brad

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So I’ve actually done this… I used this SDR:? ?? which tunes down to 24 MHz.? I tapped into the uBITx IF at TP14 on the rev4 schematic… before the 45 MHz roofing filter so the IF spectrum is still wide banded… used a 5pf cap as not to load the IF.? I ran that into an IF amplifier made from a MC1350P circuit for 45 MHz right out of the app note.? The response from 1-30 MHz is not flat, so I took an analog pin from the Arduino to set the AGC on the MC1350P and developed a table that generates an AGC voltage for each band as selected that is calibrated basis a known input signal to give dBm on the waterfall.? The software I used for the spectrum display is Freq-show from here: .? It works very well.? I will post a video when my ubitx is back together (currently adding… yes… a “second” receiver… ohhhhh!).? I’m not an expert coder, but once this Python app can be coded into the Teensy, I think we have an all-in-one solution!

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Dr. William J. Schmidt - K9HZ

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From: [email protected] [mailto:[email protected]] On Behalf Of Ralph Mowery
Sent: Wednesday, May 30, 2018 2:43 PM
To: [email protected]
Subject: Re: [BITX20] SDR as Waterfall display

?

I have not tried it,but from the circuit description the first conversion is at 45 MHz.? I would try laying a short insulated wire near Q10.? You may even be able to tap off the emitter of q12 with a low value capacitor.?

?

Then tune the SDR ( I assume we are talking the about $ 15 TV dongle, but does not matter)? to around 45 MHz.??

?

There may be more out now, but the two that I bought a number of years ago, one goes from about 25 MHz up and the other starts at 50 some MHz.

?

de ku4pt

?

?

On Wed, May 30, 2018 at 3:06 PM, brad martin <emclinux@...> wrote:

I noticed that the CEC firmware has an SDR mode but this seems to be where the audio as as well are transmitted to the SDR and handled there.? Seems to be a good method for digital or recording but is there a way to just use the SDR as a waterfall display and still have the radio function as normal (i.e. have audio come out the radio speakers)?

?

Brad

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Virus-free.