The guys opening up TX typically open up RX at the same time, read those mods Robb posted again. With some processing on TX and a good external speaker on RX there is audio being produced and received on CB that is full bodied, articulate and easy to listen to.
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TX audio mods
- Thread starter Crasher
- Start date
The guys opening up TX typically open up RX at the same time, read those mods Robb posted again. With some processing on TX and a good external speaker on RX there is audio being produced and received on CB that is full bodied, articulate and easy to listen to.
This is the reason I mention the D-104 mod because it can be difficult to get a good balance in tone once the mods are done. People will often set the EQ to over emphasize bass because they are not happy with the bandwidth they are hearing and want more. You can't force bass through the audio chain like this. If you're needing extreme boost in the low end on an EQ, you probably don't have the needed bandwidth in the first place. That tends to create noticeable distortion and a muddy sound in the low end.
To add insult to injury they will remove just about all mid range to make pulling the speech out of that mud even more difficult. I'm finding very good results can be obtained modifying the D-104 and using it on rigs that have had the bandwidth increased. That's because the element is tailored for clean speech and most suitable for AM. Important frequency ranges that make understanding what's being said through noise have been slightly emphasized.
The only notably lacking area is in the bass response as compared to most mics that would be considered Hi-Fi. Changing the first stage of the preamp to an FET with a gate resistor at least 4.7 meg does the trick real good. Your results will vary depending on the condition of your specific element. Unfortunately about 50% of the D-104 crystal elements cannot provide the original frequency response and gain as they did new.
Many assume the crystal itself has gone bad but humidity and temperature changes have really destroyed the mechanical bond between the crystal, aluminum diaphragm and the housing the crystal is mounted to. The aluminum diaphragm on the front is only bonded to the metal pin of the crystal by a drop of black wax. Expansion and contraction often breaks that bond. One drop of wax can fix this problem.
The other problems are more severe and less likely to be able to fix without further damage because you have to remove the diaphragm before you can access the other two bonding points to the crystal. They are the two corners of the crystal where the metal pin forms the arch over the crystal on both sides and the two rubber shock pads on the back side, mounting it to the plastic case.
To add insult to injury they will remove just about all mid range to make pulling the speech out of that mud even more difficult. I'm finding very good results can be obtained modifying the D-104 and using it on rigs that have had the bandwidth increased. That's because the element is tailored for clean speech and most suitable for AM. Important frequency ranges that make understanding what's being said through noise have been slightly emphasized.
The only notably lacking area is in the bass response as compared to most mics that would be considered Hi-Fi. Changing the first stage of the preamp to an FET with a gate resistor at least 4.7 meg does the trick real good. Your results will vary depending on the condition of your specific element. Unfortunately about 50% of the D-104 crystal elements cannot provide the original frequency response and gain as they did new.
Many assume the crystal itself has gone bad but humidity and temperature changes have really destroyed the mechanical bond between the crystal, aluminum diaphragm and the housing the crystal is mounted to. The aluminum diaphragm on the front is only bonded to the metal pin of the crystal by a drop of black wax. Expansion and contraction often breaks that bond. One drop of wax can fix this problem.
The other problems are more severe and less likely to be able to fix without further damage because you have to remove the diaphragm before you can access the other two bonding points to the crystal. They are the two corners of the crystal where the metal pin forms the arch over the crystal on both sides and the two rubber shock pads on the back side, mounting it to the plastic case.
Not too hard to hear the difference even when a radio's receive is narrow, I can tell the difference every time when someone has modded their TX even on a stocker radio. Mechanical filters aren't perfect, there is a slope/cutoff point that can still hear some when the bass has been extended and same for the highs before it positively rolls it off. DSP is another thing altogether. When using the FlexRadio SDR-1000, I see the audio curves from Ham stations and see that the filters do not shut off as described. Same is true for CBers as well.
What the mods do is extend the bass range - which was beforehand cut out altogether - and a modest extension of the range to 4khz which helps out articulation considerably. It really isn't real 'hifi' in the same sense that the word is otherwise used, but a modest change change that makes a perceivable difference.
Yes, Bob Heil DOES do it. In fact, without his choice of mics it would be otherwise impossible to achieve these results in Ham radio. He has also made a tidy sum in doing this too. He is no fool, and ran ahead of other before they realized where it was going. The PR-40 is a favorite choice amongst those who play there. However it is not the best in its field of competitors; the EV RE20 and 27 and the Shure SM-7B still edge him out by a tad.
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No doubt the SM-58 is going to sound better in the long run. I use one on my Kenwood but it also has to pass through a good deal of rack equipment to pass my inspection. If I ever tried to dump the Shure directly into the radio, it would sound muddy and need lots of gain reduction around 250 cycles before it would clean up.
The beauty of the D-104 hi impedance mod is that the crystal can now reach 30 cycles before hitting the 3db down point. You don't need any other equipment if the radio has good bandwidth. Not studio grade Hi-Fi but the best sound I've heard with just a mic and radio. There is actually a good deal of info online about this type of mod and the results with the D-104.
The beauty of the D-104 hi impedance mod is that the crystal can now reach 30 cycles before hitting the 3db down point. You don't need any other equipment if the radio has good bandwidth. Not studio grade Hi-Fi but the best sound I've heard with just a mic and radio. There is actually a good deal of info online about this type of mod and the results with the D-104.
I'll agree that the Astatic is a classic and that it does have a decent bass response. I prefer a mic with an otherwise smoother response. Crystal mics tend to have some peaks along its response curve that takes out a natural sound - IMO.
The Shure SM-58 is also a standard in the industry and I have used many of them in the past for live sound and even some applications in studio recording work (works great on snare drums and tom-toms). Vocalists in a live performance prefer it nearly every time. Still a great yet inexpensive choice for radio.
But for a real ruler-flat, uncolored response that is easy to EQ to ones own personal tastes, I prefer a hot tube plate sound condenser mic. Just 'too cool for school'; sounds brilliant and exceedingly natural. Tends to be a bit too sensitive - though. A little pricey, but about the same cost as Heil's PR-40 . . .
The Shure SM-58 is also a standard in the industry and I have used many of them in the past for live sound and even some applications in studio recording work (works great on snare drums and tom-toms). Vocalists in a live performance prefer it nearly every time. Still a great yet inexpensive choice for radio.
But for a real ruler-flat, uncolored response that is easy to EQ to ones own personal tastes, I prefer a hot tube plate sound condenser mic. Just 'too cool for school'; sounds brilliant and exceedingly natural. Tends to be a bit too sensitive - though. A little pricey, but about the same cost as Heil's PR-40 . . .
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Yes I know they do. However 99.9999999999999% of the people that hear them haven't so there's no benefit.
If you want broadcast audio why not just use AM?
Then there's the biggest elephant in the room. Narrow band modes get you further per watt than wider modes. So by using ESSB that only a fraction of a percent of CB/amateurs can actually receive fully, you're reducing the range that you can reach with the power you have.
Since we are talking about frequency response to 4 KHz and a bandwidth of 8 KHz I think it's safe to assume we are not talking about ESSB and we are indeed talking about Hi-Fi AM. The idea that a stock receiver can't hear anything outside of 300 to 3000 cycles is not accurate. That's just where the 3 db down points typically are. Most will easily respond to increases in bass almost twice as low and up to 4 KHz with no mods although it will be a few more db down.
Why do what 99.9% of operators are doing when I can do what .1% of them are doing? And in actuality, there are quite a few really nice sounding stations throughout the 40 CB channels.
That's the goal, and it beats over modulated echo boards all to hell.
ESSB? I've tried SSB a few times and it's not my cup of tea. I felt like a sailor in the bowels of a ship wearing headphones working that QRP, so I certainly have no interest in ESSB. But all the way from 23cm to 160m there ought to be something for everyone!
Yeah, I'm not sure where this got side tracked.
Exactly, most people look at filters and bandwidth like a brick wall when in reality they all have a shape.
You said to change out R-176(270K) for a 470K resistor for more gain especially when you want to run a noise cancelling mic. I want to run my Ranger SRA-198 exclusively on my 959. My first thought was to turn up VR16. What's the difference?
I have a Top Gun CP-1. The Top Gun CP-1 instructions say to remove R-176&R-186 before soldering in their CP-1.
Just wondering what to do here.
Bonus vid: http://youtu.be/eHnHncbUDoA
D-104 mod:
http://youtu.be/aLbB4XUS0lM
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No; I didn't say that. These are not my mods, they are info given on the 'net by the tech that goes by the name of 'Goldfinger'. I don't recommend doing that - either.
Changing the gain in any stage of the radio means that it will affect the modulation % output. I would be really careful of doing that, since more than 100% is never a thing that is desirable since it will cause the radio to have spurious emissions. Unless the NPC/RC mod is done with only a modest boost to the positive peaks first; but that is getting way ahead of ourselves as far as wider audio bandwidth is concerned.
It seems that AMers are always looking for ways to get the gain up past 100%. But 100% modulation is still "hitting the wall"; the point where any gain is lost as distortion and spurious emissions. Most if not all radios can be adjusted to get 100% modulation without having to hack their radios anyway. Better to make the most of the available bandwidth that the mod otherwise makes, which is getting ~40hz to 4khz audio bandwidth on both TX and RX.
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As far as the instructions for your CP-1 goes, I would follow the instructions to the letter. In addition, the SP1A is also a compressor. So you will have to choose between the CP-1 and the SP1A, as you don't want to use two compressors at the same time; bad juju. Neither one add to the bandwidth of your audio signal, they just compress the audio peaks so they do not exceed 100% modulation. Once again, comparing apples to oranges when talking about audio bandwidth and audio peaks.
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I just want to match my radio to the SRA-198 I have. I continuously moniter my modulation levels and make sure they don't go over 100%. I like to have my SRA-198 on my 959 peak at 100%,it's just that I have to eat the mic to get the modulation level that I desire.
By the way,it's a DTB tuned radio.
How are you monitoring modulation? Why not switch to the SRA158, it's a great hand mic.
My 959 is DTB tuned. That means that it's modulation meter is accurate plus I have a stand alone modulation meter to check against it. I already have a SRA-198 so I'm going to use it.
Also,I have but not installed are CP-1,a RF Limited TRBX2,a speech processor board and plans from CBCINTL,and a Art Tube 2 MP tube preamp. All of these aren't installed in anything yet.
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