Easiest way to achieve hi fi?

[sixstrings]

Hi


Have you seen the direct inject vs. motor mouth maul modulator? Sorry I dont have the link but if you search "direct inject vs. motor mouth maul modulator" it's the video that has an oscillscope on the search results. Im not into his kind of audio type but even the mmm @ 150% has crispy edges in my headphones and at 200 the sound is quite fatiguing and being in a band for the last 20 years I can take distortion . It seems like alot of money for barley more audio.

Does anyone have an oscillicope trapaziod pattern of the mmm audio? On youtube I can only find oscope waves I heard that using an oscope watching a wave go by is accurate but hard to see cuz it goes so quick but the trapazoid wave is much more clear to see if the cb was linnear.

Peace...

 

[StrangeBrew]

....
Also I'd expect adjacent channels to be heard in the RX if I used an 8 Khz Murata but nothing in my experience can verify this, it's all conjecture on my part.
....

First the disclaimer. I don't have any real experience with hi-fi CB myself, what I have been doing is a lot of research for a possible future project. So I'm mostly just looking for some feedback to see if my own thinking is on the right track, nothing I write here should be taken as advice.

To the best of my knowledge with 10khz channel spacing you have 5khz of audio bandwidth, you have your center frequency with 5khz above and below for each sidebands audio. If you go beyond 5khz your upper sideband will encroach on the next higher frequencies lower sideband and your lower sideband will be in the next lower frequencies upper sideband.

So in theory if a filter doesn't let anything outside its rated frequency range pass a filter that says 10khz on the box would give exactly 5khz for each sideband and you would be good, the problem is filters don't seem to be very precise in where the frequency cuts off. You need to take into account how things roll off at the edges of the filters range and everything becomes much more of a judgement call.

I'm currently of the opinion that using a higher quality filter with a tighter roll off at the edges would allow using a wider spec filter with less bleed over problems, this should keep the total bandwidth of what it lets in reasonable while making the response across that bandwidth a little flatter. But I am open to reconsider this opinion if/when more info comes in.

The problem is there doesn't seem to be one complete resource for info on this stuff, you have to try to piece it together from multiple sources.


Added on edit: The filter bandwidth ratings I'm referring to above would be total bandwidth, I have noticed that in some cases a +/- figure is given instead.

 

[Captain Kilowatt]

Strangebrew, you are 100% correct on what you stated above. Many filters can have the same bandwidth but perform differently. Most are speced at -6dB point in their frequency response but how steep they roll-off after that is important. Another important figure is the attenuation at the -60dB point which shows how tight that freq roll off is. Some filters quote -50 or -55 dB instead. The sides of the filter response are called the skirts, just like a lady's skirt and you can see why from the shape of it. You want steep skirts which means a fast and deep roll off beyond the bandpass edges.

 

[543_Dallas]

543 Dallas Thank you for the idea of the sdr play and relay that's really neat, I will jot that down in the sketch book.

About the ceramic filter:
I have seen a guy swap the filter in a to-be-hifi modded export on youtube but I forget what he mentioned was used.
6 kilohertz wide would be nice, here is one I found on ebay 8 Khz Murata!
http://www.ebay.com/itm/MURATA-CFM4...455K-IF-FOR-HI-FI-SHORTWAVE-ETC-/222252515336

$40 is more than I have in the rig, but you got to pay to play!!
Thank You

Exit13 I think you are 100% correct about the a.m. only radios, the 25/29 have double conversion and outperform my 142 GTL (SSB & single conversion as you know) on RX.
-Leap

I wouldn't spend that kind of money on a filter for a CB. The end result is not worth it. The ones I use are $5 from mouser. I'll have to get back with you on the part number.

Correct me if I'm wrong but on an AM radio a 6khz filter would give 3khz of audio and the 8khz filter would give 4khz audio bandwidth, so based on that I would think that an 8 would be the way to go.

A 6k is 6 up and 6 down. An 8k filter would be great for a transmitter but too wide for an RX filter on 11 meters IMO. 6 is what I use. The sdr receivers are nice because you can listen with a wide filter and narrow it with a click of the mouse if you start to get bleed over from adjacent channels.

Hi


Have you seen the direct inject vs. motor mouth maul modulator? Sorry I dont have the link but if you search "direct inject vs. motor mouth maul modulator" it's the video that has an oscillscope on the search results. Im not into his kind of audio type but even the mmm @ 150% has crispy edges in my headphones and at 200 the sound is quite fatiguing and being in a band for the last 20 years I can take distortion . It seems like alot of money for barley more audio.

Does anyone have an oscillicope trapaziod pattern of the mmm audio? On youtube I can only find oscope waves I heard that using an oscope watching a wave go by is accurate but hard to see cuz it goes so quick but the trapazoid wave is much more clear to see if the cb was linnear.

Peace...

What are your headphones plugged into? A receiver with a diode detector or a simple demodulator circuit will start to distort more and more with higher positive peaks.

The trapezoid test doesn't apply here because we're not using a linear amplifier. It is a comparison of amplifier input to amplifier output.

High level modulation is used with the MMM board and the direct injection deal. Audio is mixed with the carrier at the finals. Basically modern plate modulation.

 

[Bearcat]

Hi


Have you seen the direct inject vs. motor mouth maul modulator? Sorry I dont have the link but if you search "direct inject vs. motor mouth maul modulator" it's the video that has an oscillscope on the search results. Im not into his kind of audio type but even the mmm @ 150% has crispy edges in my headphones and at 200 the sound is quite fatiguing and being in a band for the last 20 years I can take distortion . It seems like alot of money for barley more audio.

Does anyone have an oscillicope trapaziod pattern of the mmm audio? On youtube I can only find oscope waves I heard that using an oscope watching a wave go by is accurate but hard to see cuz it goes so quick but the trapazoid wave is much more clear to see if the cb was linnear.

Peace...

I don't care for mmm sound or board..dude has muddy sounding audio and some people like that low below sound..if I'm going to use a board it's probably going to be asymod

 

[sixstrings]

Yes, I agree about the muddy audio he sounds kinda on the poor side. Shocking to me was how close the direct inject sounds only tonally compaired to mmm.
Also the video poster says something like Im using and 8k filter. From reading the forum posts isn't that only 4khz of audio? If thats correct and please correct if Im wrong that is no where near hifi and if I when I listen to the audio I don't hear very many higher tones so I think that gives his audio the appearance of being muddy but I dont have a spectrum analyzer in my head - well I almost do.

My headphones are plugged into the headphone jack on my studio monitors and the audio source is youtube. The speakers and amp are of good quality. So I'm listening to the video posters audio he has an SDR receiver and says he is not using the agc.

Please correct me again if Im wrong but does the trapiziod pattern not work with direct inject or the MMM becuase they are not linear (thanks for the spelling I should have paid more attention in spelling class) or does it show non-linearity of some type.



Wow, this is such a great web site as a radio newbie I have enjoyed hours of reading the many informative posts.


Peace....

 

[LeapFrog]

Shocking to me was how close the direct inject sounds only tonally compaired to mmm.
Also the video poster says something like Im using and 8k filter. From reading the forum posts isn't that only 4khz of audio? If thats correct and please correct if Im wrong that is no where near hifi and if I when I listen to the audio I don't hear very many higher tones so I think that gives his audio the appearance of being muddy but I dont have a spectrum analyzer in my head - well I almost do.

I agree but only up to 150% modulation, they sound close!

I think this is the video? At 200% modulation (i.m.o.) the direct inject audio sounds too distorted compared to the MMM board at 200%.

 

[543_Dallas]

I don't care for mmm sound or board..dude has muddy sounding audio and some people like that low below sound..if I'm going to use a board it's probably going to be asymod

The asymod and mmm boards do the same thing. How you sound is determined by how you run your equalizer and how much or little processing you use. The MMM board doesn't make you sound like him. Some of his customers use similar processing trying to sound like him.

Yes, I agree about the muddy audio he sounds kinda on the poor side. Shocking to me was how close the direct inject sounds only tonally compaired to mmm.
Also the video poster says something like Im using and 8k filter. From reading the forum posts isn't that only 4khz of audio? If thats correct and please correct if Im wrong that is no where near hifi and if I when I listen to the audio I don't hear very many higher tones so I think that gives his audio the appearance of being muddy but I dont have a spectrum analyzer in my head - well I almost do.

My headphones are plugged into the headphone jack on my studio monitors and the audio source is youtube. The speakers and amp are of good quality. So I'm listening to the video posters audio he has an SDR receiver and says he is not using the agc.

Please correct me again if Im wrong but does the trapiziod pattern not work with direct inject or the MMM becuase they are not linear (thanks for the spelling I should have paid more attention in spelling class) or does it show non-linearity of some type.



Wow, this is such a great web site as a radio newbie I have enjoyed hours of reading the many informative posts.


Peace....

Since you are modulating the finals in the radio there is no input and output of an amplifier to compare. If it were a low level modulated rig or if you wanted to see how linear your amplifier is use the trapezoid test.

The board gives you an edge over piping the audio into the the am regulator of the 148 (direct inject). I was able to get around 110% positive peaks that way. EQ settings are important. The wrong bass makes mud. Low end bass will help keep the carrier from pinching if done right. You can see a waveform within a waveform on the scope. If you ever see it it will make better sense.

I've also had some luck using the 3 diode ultra modulation (one to google) trick on solid state rigs. You can't get carried away or the waveform looks like poo but just a touch of keep alive voltage helps.

 

[sixstrings]

I see said the blind man as he pulled up a chair and sat on the floor. So the trapezoid pattern is not usable on AM only side band got it.

If I got this thread correctly then the mmm only give a slight advantage over D.I.? The cost difference is like 10000x more? The mmm is not a linear board? The mmm can goto high % of modulation but that is not suitable for a diode detector?

I have a nice cap - audio grade tantalum do you think it would be worth it to try the DI. I have a older style virgin 148 and a small foot warmer.

So much to learn. Thanks for all your help.

Peace

 

[LeapFrog]

The only information I have found on the "3 diode ultra modulation" are in reference to tube rigs, an old PDF scanned from an ARRL page circa 1956 (here), I figure the idea can be applied to modern solid state rigs, I just have to decipher how!

 

[543_Dallas]

So the trapezoid pattern is not usable on AM only side band got it.

It's not an am or ssb thing. It is a test to show if an amplifier is linear.

If I got this thread correctly then the mmm only give a slight advantage over D.I.? The cost difference is like 10000x more? The mmm is not a linear board? The mmm can goto high % of modulation but that is not suitable for a diode detector?

I have a nice cap - audio grade tantalum do you think it would be worth it to try the DI. I have a older style virgin 148 and a small foot warmer.

So much to learn. Thanks for all your help.

Peace

The mmm board is not an amplifier. It is a modulator/carrier control circuit. How much of an advantage it is over di depends on your skills and knowledge. The MMM board makes things easier for the operator. For CB work keep it under 150% and it will be fine...some CBers call small amplifiers modulators. That is a golden screwdriver term and not really a modulator. I just wanted to make sure that wasn't where the confusion came from.

I use a home brew copy of the board but did the DI thing for years. The board seems to have better freq response. I was skeptical about it at first but someone was kind enough to build and give me the board. I think they are worth the 100 to 200 bucks they cost. Now that they are single voltage it's even easier.

Something to keep mind about Joe Dirt's video is that he's been doing this for a while. He spent a lot of time with the DI method before the MMM board. A rookie would not have had the DI radio sounding that good to begin with.

If you DI the 148 shoot for 90-100% modulation. It is very easy to cause distortion. It will sound muddy and muffled when you push the modulation too hard. The first thing a lot of guys will do is start adjusting the eq because they think they have too much bass. The learning curve can be steep.

Then you have to deal with everyone telling you to turn up your mic gain because your audio is low. A good peak limiter and proper compression help with this. I could keep going but this is why there isn't always a simple answer for the issues you will run into with this stuff. Lots of trial and error.

The only information I have found on the "3 diode ultra modulation" are in reference to tube rigs, an old PDF scanned from an ARRL page circa 1956 (here), I figure the idea can be applied to modern solid state rigs, I just have to decipher how!

That's it. Look at D8 in a cobra 29. That's the first diode so you'll only need 2 more. Now take that 3 diode contraption and put it in series with tp7 and tp8 on a cobra 148 chassis...
I think it's tp7 and 8. They are the the wires for measuring final and driver bias. Don't get crazy with it or you'll still end up with squared off negative peaks.

 

[sixstrings]

Cool, thanks for the clarification. Makes much more sense now.

My appologies for asking so many questions but I do have one more about a post here on the forum about a conversion to low-level am on a cobra 2000 witch I understand is basically the same radio..worth investigating or no?

Ill shut and read more now...


Peace to all

 

[Sonar]

Like on video gates you hear 131 mustang and bass master? Or Stacy Adams? That's the sound I like? Can u even run power with this stuff?

HiFi on AM is a misleading acronym. True HiFi is normally associated with FM, but If you wanna sound like 131 Mustang get yourself one of those Dave Made transmitters he's operating. I'm not familiar with the setup of the DM transmitter but short of a good mic you're probably gonna be good to go. You could get yourself a nice valiant for between $400 and $800. Actually any later 1950's AM transmitter will have you sounding exceptional on AM. Essb is a different monster and much easier to get any of the big three company transceivers sounding excellent. After purchase Kenwood ect ect buy yourself a W2HIY 8 band eq, eq+ or both and with a little listening and reports you'll be in business. There's other ways of doing it but like many said it's a learning curve, and IMO a mess of wires, lots of money not well spent only to realize HiFi AM is actually widebanding on AM. I've come to enjoy and appreciate my slightly modded sonar fs 2340 (bypassed audio clipper board) driving a phantom (11/2 watts dk 18 pep) and demco modulator. That's just me of course and everybody has to meet their own expectations and dreams of what they want their stations to sound like. Good luck. Ps Whatever you wind up doing please don't hang out on channel 28 (AM) and take song requests (no name's mentioned). 73

 

[Captain Kilowatt]

The trapezoid test doesn't apply here because we're not using a linear amplifier. It is a comparison of amplifier input to amplifier output.

[QUOTE="543_Dallas, post: 564156, member: 21044"
Since you are modulating the finals in the radio there is no input and output of an amplifier to compare. If it were a low level modulated rig or if you wanted to see how linear your amplifier is use the trapezoid test.[/QUOTE]

Not necessarily. While a trapezoidal test does show linearity it is also useful for measuring the modulation of an RF envelope.

http://www.radiomagonline.com/misc/0082/measuring-modulation/26624

https://www.google.ca/url?sa=t&rct=...2C9XIodEw&sig2=uSbNprSFnliy7YTcEqSfxA&cad=rja

 

[Bearcat]

HiFi on AM is a misleading acronym. True HiFi is normally associated with FM, but If you wanna sound like 131 Mustang get yourself one of those Dave Made transmitters he's operating. I'm not familiar with the setup of the DM transmitter but short of a good mic you're probably gonna be good to go. You could get yourself a nice valiant for between $400 and $800. Actually any later 1950's AM transmitter will have you sounding exceptional on AM. Essb is a different monster and much easier to get any of the big three company transceivers sounding excellent. After purchase Kenwood ect ect buy yourself a W2HIY 8 band eq, eq+ or both and with a little listening and reports you'll be in business. There's other ways of doing it but like many said it's a learning curve, and IMO a mess of wires, lots of money not well spent only to realize HiFi AM is actually widebanding on AM. Good luck. Ps Whatever you wind up doing please don't hang out on channel 28 (AM) and take song requests (no name's mentioned).

Oh good god...I'm not a disc jockey....lmao...they don't make Dave made transmiters anymore do they? And the w2hiy is hardly worth that kind of money..maybe at the end of the day a Turner +3 is the way to go with a touch of echo on a connex board ...I just want to get away from the pinched tinny sound ....why talk on a trashy sounding radio..don't we strive to sound good over the air?? Good points sonar...if I could get a valiant I would.