Mic eq device?

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gatorjj
 

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Joined: 11 Oct 2022, 00:06

Mic eq device?

Post by gatorjj »

I've been testing a couple different microphones through web-sdr when propagation is okay, and today compared my FT-991A at 5 watts (with the eq and processing) which was much clearer and easier to understand than the (tr)usdx. The (tr)usdx audio sounds more bottom heavy, not bad but that energy seems to be lost especially with QRP and lower signal levels.

So I did an experiment running a mic through my computer music stuff and software eq to roll the bottom off and peak up around 1.2Khz, and send it into the (tr)usdx. The result was much clearer and easier to understand. I captured a before and after if anybody would like to hear it.

This is not a request for EQ to be part of the (tr)usdx itself. Rather, I'm asking the forum if anyone has or knows of a simple electronic design for a couple bands of EQ that could sit between the mic and radio? Basically a high-pass filter and a peak in the voice range.

I'm not much of an electronic design guy, but I know some of you here are so thanks in advance 8-)

J.J. KF4VE
Constrainted
 

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Joined: 20 Dec 2022, 20:51

Re: Mic eq device?

Post by Constrainted »

gatorjj wrote: 08 Mar 2023, 01:28 The result was much clearer and easier to understand. I captured a before and after if anybody would like to hear it.
I would like to hear it, if it is not too much trouble for you to post a link. Thanks for this work you have done to improve the sound quality.
gatorjj
 

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Re: Mic eq device?

Post by gatorjj »

After I posted this initially, I had a thought. I always bring a laptop with me for POTA logging, so why not use that as the mic with EQ?

So these samples are first with the internal (tr)usdx mic, then through the laptop mic (above the screen I think), through a software EQ, and into the (tr)usdx. I have 2 other mics wired up but the internal (tr)usdx one seems to come through the clearest though the difference is slight.

Here's a couple A/B's. I think I shared them correctly but if they don't work let me know.

First one has a little better propagation so you can hear the quality of both.
https://www.dropbox.com/s/r98oj8ji9150y ... 9.mp3?dl=0

Second one propagation is a little worse, but might actually make the point better of what I'm trying to accomplish. More contacts especially when propagation is not great!
https://www.dropbox.com/s/0ivla20xpf2hc ... 9.mp3?dl=0

There's a little "kerchunk" at the start of the laptop sample, there's latency through the laptop and it picks up the last little bit of radio speaker noise before transmitting. I think I can reduce it but will worry about that later.

J.J. KF4VE
Ohwenzelph
 

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Re: Mic eq device?

Post by Ohwenzelph »

Excellent
Ohwenzelph
 

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Re: Mic eq device?

Post by Ohwenzelph »

See http://www.w1aex.com/mic/mic.html
Don’t know if this would apply or work, I do not understand it well enough and have not tried it.
But it seems like one would cut the link between C17 and C18 on the main board, and then reestablish the connection with a 4.7k resistor in parallel with a 0.047uf capacitor. 603 size or maybe 402 size.
fwiw
73
Jerry aa1of
0ED734F3-E241-4B98-AA2C-6DA9CD5BFCDF.jpeg
0ED734F3-E241-4B98-AA2C-6DA9CD5BFCDF.jpeg (55.04 KiB) Viewed 3887 times
(This would apply if the signal arrives at the right side pad of C18 in the first photo, left side in the second)
6A14E08E-157B-42C8-8F8D-57033E53262C.jpeg
6A14E08E-157B-42C8-8F8D-57033E53262C.jpeg (77.17 KiB) Viewed 3856 times
Last edited by Ohwenzelph on 10 Mar 2023, 21:34, edited 1 time in total.
gatorjj
 

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Joined: 11 Oct 2022, 00:06

Re: Mic eq device?

Post by gatorjj »

Thanks for the info Jerry!

I don't want to mess with the board at this point so I will try to build a couple filters outboard to see what happens. While I understand the basics of electronics somewhat, accurately designing something even this simple is way above my head. So I'll just put a few things together outside and see what it sounds like :mrgreen:

I did try using the laptop & SW eq out in a park yesterday, it actually worked great...like doing a Zoom call for POTA, just talking to the laptop screen. Not the long term solution, but the PoC stage is at least positive!

J.J. KF4VE
gatorjj
 

Posts: 50
Joined: 11 Oct 2022, 00:06

Re: Mic eq device?

Post by gatorjj »

I decided to buy some little breadboards, a bag of parts, and start surfing the internet to learn a little electronics. After a lot of learning and plugging, I came up with this which seems to work okay to help the SSB audio get through better (samples below). I would bet someone with knowledge could design a much better version of this, but hey I'm just amazed I got it to work!

Here's a couple back to back A/B audio compares over a webSDR (~400 miles away), first using a Retevis mic and then this circuit at TX drive of 4 and 5 (I was trying to optimize the output for TX drive of 5 to try and get some compression from the radio). And at the end, my FT-991A at 5w to remind me that I'm trying to improve readibility on the (tr)usdx, not catch a Yaesu! :roll:
https://www.dropbox.com/s/nusmb0nll9tmj ... s.mp3?dl=0

The jist is an outboard circuit with a lowpass filter around 10Khz, to a highpass filter around 480Hz, and into a 2 stage amp before going to the radio. Using whatever designs I could find that matched my new bag of parts :mrgreen: It powers from the same battery that powers the (tr)usdx so I added a Y-cable for that.

Here's the schematic, hopefully I caught everything correctly. (Edit: added a voltage divider to the mic)
Screen Shot 2023-03-27 at 11.35.18 AM.png
Screen Shot 2023-03-27 at 11.35.18 AM.png (46.06 KiB) Viewed 3677 times
Please let me know what you think, or if you have a better way to do this!

J.J. KF4VE
Last edited by gatorjj on 27 Mar 2023, 15:37, edited 1 time in total.
Ohwenzelph
 

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Re: Mic eq device?

Post by Ohwenzelph »

You have blown way past me, wish I knew enough to understand it and comment but I do not.
Another phone audio reference:
https://www.ti.com/lit/an/slyt155/slyt155.pdf
gatorjj
 

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Joined: 11 Oct 2022, 00:06

Re: Mic eq device?

Post by gatorjj »

I decided to try some contacts using this circuit in the CQ WPX SSB contest, not expecting much with all the kilowatt stations and QRM everywhere. But, made 150 QSO's across 41 entities with my classic band version and a vertical dipole :o

I have this mic thing wired up in a box now and have used it a few times for POTA, it could be my sense of accomplishment but it sure feels easier to make SSB contacts now even when conditions aren't that great.
Love this little radio more every day :mrgreen:
CQ WPX SSB 2023.jpg
CQ WPX SSB 2023.jpg (187.4 KiB) Viewed 3629 times
J.J. KF4VE
Ohwenzelph
 

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Re: Mic eq device?

Post by Ohwenzelph »

Attempt at http://www.w1aex.com/mic/mic.html mod. Basically high pass to reduce lower frequency audio coming from the mic. I hope I understand the circuit and board correctly.
Trace cut between C17 &C18:
AA4CDB4D-A94E-40EB-8A31-0128E2207031.jpeg
AA4CDB4D-A94E-40EB-8A31-0128E2207031.jpeg (102.7 KiB) Viewed 3585 times
Re connected with 4.7k ohm resistor:
FEE0BAAF-4C20-4F8A-ABB9-46D82D2757E7.jpeg
FEE0BAAF-4C20-4F8A-ABB9-46D82D2757E7.jpeg (116.99 KiB) Viewed 3585 times
Parallel 0.047uF cap added:
2086F74F-5BC2-4775-BBC7-DB8371AF06A6.jpeg
2086F74F-5BC2-4775-BBC7-DB8371AF06A6.jpeg (130.3 KiB) Viewed 3585 times
Will it make a difference? If I figure that out I’ll let you all know! 73 Jerry aa1of
gatorjj
 

Posts: 50
Joined: 11 Oct 2022, 00:06

Re: Mic eq device?

Post by gatorjj »

Jerry please let us know how that works out!

J.J. KF4VE
Ohwenzelph
 

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Re: Mic eq device?

Post by Ohwenzelph »

Was worried there might not be enough audio left. Put up an antenna, cloud warmer height, 40m, listened to an in state websdr. Initial impression, sounds ok. Tried 3 elements: CMEJ-0627-42-P (this should be very close to the stock mic), Com Mic JLI-52B, and AOM-5024L-HD-R which did sound the loudest. I don’t have a comparison with and without the mod, just a first impression but it did not wipe out the audio and for now I am leaving it in.
Update
With a bit worse propagation couldn’t hear my self at all with the stock mic( but could with the AOM-5024L-HD-R, so that extra gain may be necessary after all. Maybe. With the mod my wife says the internal mic (a CMEJ-0627-42-P) sounds the best. I shorted past the mod
IMG_0636.jpeg
IMG_0636.jpeg (21 KiB) Viewed 3428 times
and then I thought the Com Mic JLI-52B sounded the best and the AOM-5024L-HD-R was NOT good, made noise when not talking and distorted and when I removed the short again I decided i was still not happy with the AOM-5024L-HD-R. But unfortunately I didn’t have my wife listen when the mod was disabled.
So, clear as mud! What I got so far…
Got tired of ‘I can barely hear you’ so tried another configuration, 0.047 uf from C18 to C17 with no parallel resistor but with a 6.8k from C18 to ground. No results to report yet.
IMG-0639.jpeg
IMG-0639.jpeg (215.62 KiB) Viewed 3392 times
gatorjj
 

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Joined: 11 Oct 2022, 00:06

Re: Mic eq device?

Post by gatorjj »

Thought I would update this thread for posterity. I played around with a number of different filter settings and finally settled on this design below. The combined low pass and high pass should yield a peak around 3100 Hz. While that looks out of range, it seemed to work best with what the (tr)usdx bandwidth is. I don't have the means to measure it but I noticed playing with WSJT-X a dramatic dropoff above about 2 KHz. So I just "played it by ear" so to speak to get some more articulation. This EQ'ing drops the signal quite a bit, which is why there's a 2-stage amp after it to bring it back up.
final schematic.jpg
final schematic.jpg (26.95 KiB) Viewed 2570 times
I also learned how to turn the schematic into a PCB, and designed a little 3D printed "backpack" for the (tr)usdx along with the power connectors and a volume control for external speaker (which works great with digital as well to control the volume into the soundcard).
IMG_20230512_205720405.jpg
IMG_20230512_205720405.jpg (209.1 KiB) Viewed 2570 times
Here's what it sounds like on the other end, at TX drive set at 5 (Courtesy of the Friday Night QRP net on YouTube). It's a bit "Apollo 11" sounding, but it helps to get through quite well at all the power the (tr)usdx can muster. I haven't had to repeat myself in months :lol:
https://www.dropbox.com/s/fm5klk1jzv9bg ... 3.mp3?dl=0

Hopefully this helps somebody down the road, I have learned a lot from the experience! :mrgreen:

J.J. KF4VE
Ohwenzelph
 

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Re: Mic eq device?

Post by Ohwenzelph »

Circuitry confuses the heck out of me. I wish I knew how to apply lt spice.
Anyhow, looks like you changed R1 from 150 to 330 ohms, which should move the low pass cut off from 10,610 hz down to 4,823 hz. That would be the -3db point so the (human ear) noticeable cutoff would be even lower in frequency. Which seems consistent with your observations. Don’t know how it interacts with everything around it in your circuit and in the truSDX circuitry.
And looks like R5 went from 3.3 kohm to 220 ohm, which ought to move the hi pass cutoff from 482 hz up to 7,234 hz ?
But, nothing succeeds like success and your audio sounds perfect to me, like it’s just exactly what we need. Really good.
gatorjj
 

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Joined: 11 Oct 2022, 00:06

Re: Mic eq device?

Post by gatorjj »

Your filter calculations line up with what I saw, and initially made no sense to me. But when I drew both filter plots over each other, the intersection peaked somewhere around 3100 Hz, though down a fair amount of dB (can't remember exactly how much). That seems to be the case indeed, and all these calculations actually work! :lol:

In practical terms I think it's just putting more of the power out into frequencies where intelligibility happens when combined with the (tr)usdx response. That frequency peak may seem a little high to do that, and maybe a bit lower (or higher?) could yield better results but I'm satisfied with it and I've taken it as far as I plan to. Maybe someone will get the bug and work out something better, but for me it's time to get back to operating! Ironically, I prefer CW :mrgreen:

J.J. KF4VE
VE3RRD
 

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Re: Mic eq device?

Post by VE3RRD »

Did you have a .png version of your final schematic? The .jpg version is kind of blurry and difficult to read values when I enlarge it. AL - VE3RRD
Ohwenzelph
 

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Re: Mic eq device?

Post by Ohwenzelph »

The one from March 19th is clear and essentially identical except R1 is 330 and R5 is 220 on the newer one.
gatorjj
 

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Re: Mic eq device?

Post by gatorjj »

Sorry 'bout that, I didn't look at it close enough. Hopefully this is clearer.
Screen Shot 2023-05-12 at 8.56.38 PM.png
Screen Shot 2023-05-12 at 8.56.38 PM.png (56.95 KiB) Viewed 2319 times
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