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Author Topic: How To Improve Your Radio's Audio Capabilities?  (Read 632 times)
KC8VWM
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Posts: 3124




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« on: November 20, 2003, 02:06:35 PM »

Is it possible to connect a cheap $10 computer microphone to the computer, and then run a patch cord from your PC soundcard to your radio mic input to achieve superior quality audio on your radio?

Advantage?

You can use the computer to process & equalize your audio before it even reaches the radio. Secondly, you will be able to use your computer like an electronic scope to "see" and monitor your audio ensuring you don't get into "bandwidth" issues while using SSB for example.

I know that MFJ sells a piece of hardware that connects between your mic and your radio for this purpose, but I was wondering if you could just use your PC instead?

With this type of computer audio processing using your PC in combination with your radio, I cannot see any reason why a cheap $10.00 computer mic can't sound as good, or mabey even better than a $200 microphone.

Has anyone tried this? Do broadcast stations use a similar "software" enviroment to achieve these results?

Is there a good place to look for software for soundcards to achieve this result?

Inquiring minds want to know...

Thanks,

Charles KC8VWM

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K0BG
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« Reply #1 on: November 20, 2003, 03:20:17 PM »

I think you're trying to mix the wrong audio if you'll excuse the pun.

Using a computer with any mic, cheap or otherwise, tayloring the response, and feeding the audio to you rig is asking for trouble. The band width of SSB is not made to be HiFi although there are a few pundits out there who would argue. Fact is, using more power or band width is both bad sportsmanship and technically against the rules.

Want better audio? Use wide band FM on the properly allocated frequencies for such operation.

Alan, KØBG
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K5DVW
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« Reply #2 on: November 20, 2003, 03:36:48 PM »

Oh, I wouldnt call it bad operating practice to shape the audio to flatten out or emphasize a microphone response... infact my ICOM 756PII has graphic equalization adjustments to do just that.  

Using a computer for equalization seems like a good idea to me if all you're wanting to do is mess with your audio within the permitted spectrum. Since a lot of folks rigs are already hooked to the soundcard for SSTV and PSK, it would make sense to add computer controlled audio shaping. At least that's what I understand you're trying to do.

However, you could still end up over driving the rig if you're not careful, and splattering all over the place even if you had a brick wall 2.5Khz SSB software filter. So it's no guarantee just to shape the audio externally.
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RobertKoernerExAE7G
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« Reply #3 on: November 20, 2003, 04:19:56 PM »

A good way to check out your theory is to ask anyone who has the superior audio you want to emulate how they did it.

see if you can find a web site for w8fam or k8fam. He owns broadcast stations and uses processing equipment from his stations in his ham radio set up.  Or, at least he did a few years ago.  But this equpiment is in the 10s of thousands of dollars.  It isn't software for a PC using a sound card.

And, he is on HF.

73
Bob
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KD7EVS
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« Reply #4 on: November 20, 2003, 05:19:07 PM »

well, there is a DSP program on linux that's pretty sweet. haven't played with it for a while but as with most open source software it's probably gotten better.

If I were going to do it, I'd do it both ways. I'd spend more than 10 bucks for the mic but not a ton. also I'd feed the output out of the radio through the PC.  this way you can apply all the DSP you want on both outgoing and incomming audio.  I know several stations that use software DSP to pick up weaker signals.

one note.  make sure to use an isolation circut on both the feed to and from the radio to keep PC generated noise off of both.

there is alot of information about DSP software and needed isolation circuts online. do a bit of googling.

Seven Three
ZEB
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K6AER
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« Reply #5 on: November 20, 2003, 05:37:28 PM »

You can shape your audio using the audio card in your computer very well. That said, I would still use the best microphone you can afford and at least use a microphone designed for wide band audio response. Many of these microphones are available from Radio Shack for 35-60 dollar range and will have audio quality approaching a $130 Heil unit. Remember audio that starts distorted at the microphone will contain harmonic distortion that can be filtered to a point but will have in-band harmonics that will still make the reproduced sound brassy and harsh.

I’ve meet a lot of audiophiles and their greatest aid in good broadcast audio is they have trained their voice for a pleasant broadcast sound. Ware headphones when modulating the mic. to hear what you sound like. This will help you keep your audio level constant. A great many microphone audios are set too high and have a lot of back ground noise. Unless your are in a sound proof room, learn to modulate the microphone no more than three inches from the microphone. That way you won’t hear micro echoes from the walls. Buy a foam microphone cover to minimize breathing and air noise. Close the door to the ham shack so your QSO doesn’t have to pick your voice from a back ground of screaming kids, dogs barking and don’t forget the linear cooling fan.  In short, present the best quality audio from your mouth to the microphone with a minimum of back ground noise. After you have started with a good presentation of speech you can tailor slight response adjustments for the transmitter.

Most radio and TV types got their jobs for their voices. They worked to develop a great communication voice. This is a much cheaper road to good audio presentation than electronic processing.
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WB2WIK
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« Reply #6 on: November 20, 2003, 06:03:45 PM »

Also, remember such a system is not pure GIGO (garbage in, garbage out).  

What you "see" on your monitor, which is a spectral display of your modulation before it ever reaches your transmitter, has absolutely no bearing at all on how your transmitter will sound.  And, using a similar display connected to your receiver and running "spectrum analyzer" type software to judge received signals is similarly inconsequential: You're not analyzing the other station's modulation, you're analyzing the whole system from his microphone to your computer, and everything in between -- most of which has nothing to do with the other station's modulation.

As such, the best suggestion is to listen to yourself with headphones as you operate, using the MONITOR function of your transceiver (if it has one), or otherwise a second receiver, and make adjustments until you sound the best to yourself.

WB2WIK/6
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W8MW
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« Reply #7 on: November 20, 2003, 07:02:45 PM »

>process & equalize your audio before it even reaches the radio.

Plenty of ops interested in better transmit audio are using outboard processing techniques to tweak the audio before it reaches the radio.  The W2IHY 8 band equalizer is a product made specifically for amateur radio transmitters and I am very pleased with mine.  Some ops are using audio processors intended for professional audio and broadcast applications.  I haven't heard anyone using a PC to achieve real-time DSP for SSB transmit audio, other than the computer based rigs like Pegasus, but that doesn't mean it's not out there.    

>you will be able to use your computer like an electronic scope to "see" and monitor your audio ensuring you don't get into "bandwidth" issues while using SSB for example.

There are numerous audio spectrum analyzer applications available for the PC and it is fascinating to view a spectral display of the digitized audio. Hamalyzer is an inexpensive application. These displays can be helpful but they do not provide RF information. To monitor bandwidth of your actual transmitted signal, you'll need an RF Spectrum Analyzer.  They're expensive. I like the Tektronix Model 494A/P Spectrum Analyzer. $25,000.00 new. (Wish I could afford one).

>reason why a cheap $10.00 computer mic can't sound as good, or mabey even better than a $200 microphone.

What you're saying is possible, but for the most part I have come to believe there is no free lunch. An inferior microphone may generate horrendous amounts of internal distortion, might have terribly indadequate frequency response, might be overly prone to plosives (breath blasts), might go nuts in an RF environment, etc. Having said that, a crappy sounding microphone is an excellent candidate for use with an equalizer because it's possible to achieve a dramatic improvement in perceived audio quality.  I recorded an example of this phenomenon. Check it out on the W2IHY web site www.w2ihy.com

>Do broadcast stations use a similar "software" enviroment to achieve these results?

Yes and no.  In their recording studios most broadcast stations use digital recorders with all sorts of softward based processing options. Recorded material such as commercials, station promos and pre-recorded programs are usually enhanced with software DSP.  But the audio chain from the control room to the transmitter typically includes dedicated rack mounted hardware, most of which uses digital processing of a
propriatary design.

Hope some of this was helpful.
73, Mike W8MW
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W8JI
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« Reply #8 on: November 20, 2003, 08:32:00 PM »

Be careful using any equalization or processing, especially routing to other equipment not designed to interface.

"Brick-wall" shaping is largely a mythical dream by proponents of hi-fi audio who somehow think the stages past the modulator are perfect and IM free, and that the increased intensity of the extra unneeded lows and highs somehow doesn't add additional IM products up and down the band.

If you look at QST reviews you'll see some of the best radios for "brickwall" filtering have the poorest transmitter IM testing performance. The more "stuff" put in to mix, the more "stuff" that comes out even if levels are not too high. Extra lows and highs are especially problematic because lows tax power and bias supplies, and combine with accented highs to create stronger mixing products outside the normal passband in transmitter driver and power amplifier stages.

So don't get too carried away trying to sound like a BC station on a crowded band!!! No matter how sharp the passband cutoff is, accented highs and lows will always increase the average power in your IM products over that produced by the minimum response necessary for good communications audio.    

You also have to watch levels and watch ground loops. Audio isolation transformers will almost certainly be necessary, and you have to watch so the audio transformers don't induce hum from magnetic fields from closeby power transformers.

It certainly is possible to have good audio with a cheap mic and processing through a soundcard system (or some other device), but it might not be easy or cheap compared to just buying a good microphone, plussing it in, and being done with it.

I've been 100% successful just with capacitors and resistors to tailor response, and once in a while adding a FET, to make cheap microphones work with any rig I've had and sound good.

But radio is about experimenting and learning so give it a try. Just be mindful of pitfalls.

73 Tom
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W4CNG
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Posts: 177




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« Reply #9 on: November 20, 2003, 10:12:36 PM »

The best single piece of Audio Equipment on the Ham market today is the W2IHY EQ.  It will take most cheap to expensive mic's and taylor (EQ) them to great sounding audio on a properly set-up HF Radio.  Yes you can spend $$$ for more stuff, but unless you have a way to Monitor your audio inside of your HF Radio (read that Monitor capability which most do not have), you will be guessing at what is going on.  There are additional programs out there for analyzing audio (Spectrum Analysis programs, ie. SpectraPlus) that will give you a good representation of what is going on after the "Effects/EQ".  There are even more devices that can enhance and improve audio before entering the HF Rig (compressors, expanders, gates, aural exciters), but this gets into more $$$.  There are several folks out on HF that can give you very good advice, measure what you sound like, and have web sites dedicated to "Enhanced Audio".  None of them are using a PC sound card EQ to do the magic with.  You want "Professional Sounding Audio", get a microphone with a flat response from 100-4000hz.  Get a HF Radio with a flat response TX-Audio-Filter path that is flat from 100-3000hz. and get a way to listen to the output of what goes on the air.  You can re-shape your voice to sound like anything you want (Audio Equalizer), but natural is best.  You just have to make sure that the path and settings are flat and Natural.  There are a few of us that know audio and professional sound equipment, how to set it up for Ham Radio, and we are always ready to help others that want to step up to something better than Donald Duck SSB.  I grew up in Broadcast Radio and Televison and have had the good luck to have worked with lots of Audio Equipment, both before and how in my Ham Shack.
Good Luck
Steve W4CNG
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AA4PB
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« Reply #10 on: November 21, 2003, 12:17:41 AM »

I submit that the typical $15 computer sound card is not exactly a good clean audio device. They tend to have a good deal of low level digital noise on the output. In the audio industry the current move appears to be to sound cards that are connected to the computer via the USB in order to keep it physically removed from the noise in the computer.

In regard to a sound card being able to turn a $10 mike into a $200 mike, I doubt that you will have a lot of luck. Again, professional audio people start with the best mike they can afford even though they have plenty of EQ and digital processing available.
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WA9SVD
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« Reply #11 on: November 21, 2003, 12:38:04 AM »

While what you propose is certainly possible, what doesn't seem to have mentioned is the problem of level matching.  The microphone input of your transceiver is looking for a low-level microphone signal, whereas the sound card output is considerably higher than that level, so you need to make an adjustment.  The "volume controls" in the computer software may not allow proper or sufficient adjustment, (and many have poor control and/or poor quality at low levels)  so you may have to include a resistive attenuator in the signal path between the computer's  sound card output and the transceiver's MIC input.
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VE3TMT
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« Reply #12 on: November 21, 2003, 08:40:25 AM »

I wouldn't even trust my SoundBlaster Live 5.1 card to equal the sound I can get from my Samson and Behringer setup. Computers generate too much noise, and some of that noise will show up on your audio.  Depends on how "clean" you want to go I guess.  I am in favour of all external components between the mic and radio.
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HAMDUDE
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« Reply #13 on: November 28, 2003, 11:36:40 AM »

Put a good quality mike on the rig, make sure its gain is set properly so as not to exceed the alc and talk on it, forget all the toys and junk. Just listen to the wide, splattering muffled up raunchy audio of the so called audio boys on 14.178 and youll know how too much garbage inline with the rig sounds. Besides, hooking your computer up to the rig for audio is also inviting rfi so why create an unnecessasy hassle for yourself?
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