The following are UK links.
Tube preamp used to drive a studio condenser style or other microphone: ART Tube Preamp
Cheap and effective boom mount or desk mount condenser mic's : Microphones
Headsets are nice and I actually prefer them over a boom style or desk mic for the simple fact that id doesn't matter where you move or turn your head. The mic is always where it should be and enables true hands free operation when using a foot pedal to key the radio.
Some excellent headsets are from AKG, Audio Technica and Shure.
*Make sure the headset is wired with a "standard" XLR connector to interface with the preamp. (A mini xlr will not work with the preamp nor will a mic wired for wireless transmitters)
(Please take time to look at your transceiver's bandwidth specifications before selecting a mic. Using a mic with a bandwidth much broader than your transmit capability will do nothing to improve your SSB audio)
Bang for the buck, probably the best transceiver on the market for an entry level HF rig. An excellent option for those wanting an extremely high quality 11 meter rig with the option of possibly getting your license in the future. No comparison between a cb/export radio to this rig!
Icom 718 Review
An excellent video about properly setting up your ALC to transmit the clearest audio possible out of your transceiver. Whit is discussed in depth below: Audio Set-Up
Here's a rundown on how to make sure your audio is the best it can be and avoid over modulation.
*This can hurt you're ability to be understood clearly when conditions are poor. Yes, you will be heard but at the expense of clear legible audio.
1. Everything starts with your microphone. It is the very first thing in the signal chain so a decent mic is worth the investment.There are many types of mic's to choose from. Most of them will have differing "gain" characteristics and determining the proper mic gain setting in the radio for that individual mic will go a long way in assuring your audio will be clear and modulated correctly. For example, the stock mic on the Uniden BC980 is ok. But, I wanted more off axis rejection while talking in the car or truck with the windows down. I went to a Ranger SRA198 noise cancelling mic. The gain on that mic is considerably less than the stock mic but sounds much better. The stock mic should be set to "3" in the mic gain on the radio on a scale of 1-4. Setting it to 4 does nothing as it causes the "ALC" to clamp down.The ALC is basically a compressor limiter built into all radios. It is designed to limit a signal that is too hot from the microphone thereby preventing an "over driven condition" in the audio processor of the radio. It shows up as a very flat signal with no swing to the modulation (Swing makes you easier to hear when conditions are poor or qrm is severe). It will also drive the output to a clipping stage and we all know what that sounds like(classic cb audio). Crunchy almost.
2. Understanding of your particular transceivers audio frequency spectrum when considering using an aftermarket high end studio microphone.
Consult your owners manual. It should list your transmit and receive audio spectrum. For example, the AT6666 has a frequency response of right where the human voice is. About 400hz-2500hz. Running a mic with a broader freq' response, lets say 80hz-16000hz,to achieve more bass and high end treble (hifi audio) is useless as the transceiver won't transmit any audio outside of 400-2.5k. The factory supplied mic is very good sounding and gets nice reports while using it. I run an AudioTechnica Pro8HE ($60) headset mic, driven by an ART Tube preamp($40), Yamaha GC2020 compressor limiter and an Alesis MEQ230. The final audio signal is fed into the mic wires in the stock mic with the stock mic element removed. I run 8:1 compression with 4-6db of limiting and a .5 millisecond attack time. The delayed attack time allows the articulation in my voice to come thru unaffected increasing legibility. The limiting is set so that the audio is fully under control "before' it hits the transceiver. Power output is set at "full" on the transceiver always and never moves. I control output power by turning down the output on the comp/limiter. Mic gain is set right on the edge of engaging the alc at full power.
3. How to properly set your mic gain at the edge of the alc kicking in.
a.Make sure all connections are secure and antenna is plugged in. (never key the radio without your antenna jacked in)
b.Set your output power to full. If your transceiver does not have variable power, ignore this step.
c. Set your mic gain to full
d. Set your watt meter to an appropriate scale (ex. if your radio puts out 10 watts, set the meter to a 10-20 watt scale.)
e. While watching your watt meter, key the mic and say "audio" in a long drawn out voice at the loudest level you would talk into the mic while slowly turning down the mic gain. When you notice the output power begin to drop, that is the point where the alc is clamping down. Note the setting and now you have the proper mic gain setting for clear audio for that particular mic.
This information applies to CB/Export rigs only although the principles of setting gain applies to all transceivers. HF(Ham) rigs, like Yaesu,Icom Kenwood style rigs have a broader freq' spectrum and lend themselves well to high end studio gear. However, the improvement in audio will be most apparent to those running "HF" rigs on the receiving end. CB/Export rigs have a much narrower receive as well mimicking their transmit specs.
I have noticed that when tuning an antenna that when the swr's are say, 1.25 or higher that my output power begins to decrease. I also hear a lot of folks say if it's around 1.5 don't worry about it. A friend of mine explained that there is a difference between a true HF rig and a cb/export transceiver. A HF rig can handle higher swr's with little to no loss of power but a cb/export will lose power when the swr's begin to climb.My antennas are tuned flat and yes, they may not be spot on freq' but the transceiver puts out full power always. Just an interesting observation confirmed by trial and error and an expert in radio communications. Please reply with your thoughts and observations. 73, Steve
ReplyDeleteHobie, you obviously know a lot more about mic setup than the average cb guy. Maybe you could do a schematic how you set up your mic with all the equipment. I somewhat understand what your saying but always like pictures lol.
ReplyDeleteOK.I will get to work on that. been thinking about it for a while but I take a lot of things for granted. Gonna require some ripping and tearing to get at the wiring. I need to do some work on the foot pedal I use for keying the radio so that would be a good time to do it. Thanks for the suggestion. Cheers and beers buddy! 73 Steve
ReplyDeletewell just post pics of equipment and a drawing of how it all comes together, don't tear it all apart.
ReplyDeleteHere is how I would setup a radio with a power mic. Start with both the mic and radio mic gain a 9 o'clock. Work with someone that is not just telling you that you sound good to be nice. There is a limit to how much mosr cb or export radios can handle a power mic before the alc is over loaded and thus basically being bypassed per say. I have an icom 746. It has a built in alc meter that gets adjusted according to power output and mic gain. The way my radio works is the lower the power the lower the mic gain to get my alc meter to be in the proper "zone" or sweet spot as to not over load the alc. as I increase power have to adjust mic gain. With full power and my compression turned on my mic gain is set at about the 10 o'clock position. I speak into the mic normally saying audio and adjust mic gain to reach the alc zone limit. The higher I go with my power the higher my mic gain gets set. Also the amount of compression plays into this as well. Fortunatelty I have a monitor feature as well that lets me listen to the tx audio. Not like a cb talkback. I adjust my mic gain as I increase or decrease the power. You don't want too much power from the mic, set it at a low level and then adjust mic gain until the sweet spot is reached. This doesn't tske much but is necessary to get a clean clear signal out. Sure I can crank everything up all the way but at the expense of added heat and possibly sounding bad. It's a fine line that needs to be taken when setting a mic and mic gain. Too much of either (when using a power mic especially will most likely result in sounding like crap. So my suggestion is to turn the mic gain on both the power mic and mic gain on the radio down to at least 1/4 of full. If this is still bad keep adjusting down until the sweet spot is reached. Also turn the rf power all the way up and adjust power output with mic gain. Usually this will be around 1/4 to 1/2 or 9 to 12 o'clock. Doing this will ensure that you don't sound over modulated. Hopefully my rambling makes some sense. It's all about having a clean clear sound, I have noticed that most guys that get their named called often have their stuff setup correctly. But don't run the mic gain and power mic at full bore. It normally makes you sound like crap, causes heat. And lastly stop looking at watt meters and focus more on fhe sound.
ReplyDelete