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neil carrick (Unregistered Guest)
Unregistered guest
| | Posted on Saturday, November 20, 2004 - 10:03 am: | 
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Can anyone tell me if adding a sound processor to my radio would be of any benefit. I have a uniden 78.Thanks..Neil |
Tech808
Moderator
Username: Tech808
Post Number: 4123
Registered: 8-2002
| | Posted on Saturday, November 20, 2004 - 10:17 am: |
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neil,
Yes a Speech Processor will HELP any radio you install one in unless it is one of the MAGNUM Radios or others that already have it built in from the factory.
Lon
Tech808
CEF808
N9OSN |
That Elco guy (Unregistered Guest)
Unregistered guest
| | Posted on Saturday, November 20, 2004 - 3:10 pm: |
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Ol 808 is correct...
A speech processor will help your SSB signals ability to be heard in that it will provide a better average signal for SSB transmissions. If you are using AM (amplitude modulation with a carrier) then the preamp mike may help somewhat but if you overdrive the distortion caused by the overdrive will cancel out benefits--in otherwords do not drive more than 90% on the PEAKS of the hightest voice output.
But if you mean a sound processor like a simple audio amp probably not unless you also include with the amp audio filters to filter out unwanted audio frequencies and a knotch filter to filter out splatter and such. Otherwise you will amplify both what you want to hear and the stuff you do not want to hear--net gain zero/just louder garbage.
I hope I did not confuse ya
That Elco Guy
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Racer X (Unregistered Guest)
Unregistered guest
| | Posted on Saturday, November 20, 2004 - 9:38 pm: |
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Are you asking about speech processors, microphone equalizers, or some kind of spound processor that you would use when receiving? I use all of the above and find them beneficial, but less so for AM and more so for SSB. |
neil carrick (Unregistered Guest)
Unregistered guest
| | Posted on Sunday, November 21, 2004 - 7:43 am: |
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I was looking at a few of the processors that would be wired right into the radio..more of a speech processor. I have tried the power mics and didnt really like them.(every one told me they tended to squeal at times) I am told my radio sounds pretty good already,but just wanted to tweek things up some.(Always wanting more..right?)Where I use this every yr, it is pretty much all AM cb's. There are a few 2 meter starting to show,but not enough to rely on them only. Thanks for your comments..Neil |
neil carrick (Unregistered Guest)
Unregistered guest
| | Posted on Sunday, November 21, 2004 - 7:57 am: |
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I should add as well that this is a uniden 78. No side band, if this makes a difference. Thanks again guys |
Racer X (Unregistered Guest)
Unregistered guest
| | Posted on Sunday, November 21, 2004 - 4:30 pm: |
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Speech processors are a great way to increase your average modulation level without causing overmodulation and splatter. They can be used with a radio that has AMC and ALC adjusted to 100% maximum, and the radio will be loud and clean - the way it should be!
There are 4 major types of speech processing:
--Audio compression - This is the kind of processor used in the Magnum radios and in quite a few power microphones - most notably the Turner +3's and SuperSidekick. Audio compression works pretty well, in fact, most CB radios have a bit of compression in their audio stage already. It helps to even out the voice level, but can increase the backround noise when the level is turned up too high. If your radio has built in compression then it's very possible to cause a squeal when you use an amplified microphone and the gain is too high. That's because the compression stage already uses a high level of amplification, and when too much audio is fed into it the transistors are driven into a non-linear stage and oscillation (squeal) happens.
Audio compression is also what the AMC or "limiter" does in an AM radio or AM mode in an AM/SSB radio. Having your AMC adjusted correctly will actually allow you to sound loud and clean while keeping you from overmodulating. In a radio with a good audio stage you can realize a fair amount of compression with just the stock microphone.
--Audio clipping - Lou Franklin makes a speech processor kit that uses audio clipping, and quite a few amateur radios now use split band audio clipping instead of RF clipping. As a result the processing can be used in all modes rather than just SSB. Audio clipping is much more efficient than audio compression and can really increase the average modulation level.
The downside is that clipping at the audio level creates harmonics that fall in the same audio spectrum as your speech and can't be filtered out. The Lou Franklin kit suffers from this problem and when you use too high a level of clipping the speech becomes distorted. However it works well at lower levels and easily beats simple audio compression.
Amateur radio manufacturers use split band audio clipping to get around the harmonics problem. It splits the audio into three or four bands, clips each band independently, filters out all of the harmonics, and then combines them back into the full audio signal. The result is a clean audio signal with much higher average audio level. It works very well.
--RF compression - Most SSB radios use RF compression in the form of an ALC circuit. Adjusting the ALC to allow 100% modulation but no more will allow you to use the ALC as an RF compressor and you can get a bit more average power out of the radio and not cause any splatter. RF compression is about as efficient as audio compression, but doesn't suffer from the problem of high backround noise like audio compression does.
--RF clipping - There are two major kinds of RF clipping. One is done in the RF stage of the radio, and another is done in the audio stage which is usually an outboard unit. When done in the RF stages of the radio the processing is only useable in SSB mode because of how it's done. It works wonderfully and is a very clean way to process the signal. All of the harmonics are filtered and clean audio with a high average level is easily achieved.
Outboard RF speech processors go between the microphone and the radio. The audio output of the microphone modulates an RF SSB signal which is then amplified, clipped, filtered, and finally demodulated back to audio. It works basically the same way RF clipping is done in the RF section of a radio, but because it's done outboard and enters the radio as AF, it can be used in all modes the radio is capable of transmitting.
There were a few companies that produced RF speech processors, but I'm not aware of any currently in production. There are kits available by a german ham, and I believe he also offers completed units for a reasonable price. I understand that many amateur radio magazines had project articles for homebrewing RF clipping speech processors at one time or another.
RF clipping is easily the best method of speech processing and has the best results, although split band audio clipping is not too far away in second place.
When using a speech processor it's important to monitor your signal for distorted audio and excessive backround noise. Most manufacturers recommend using less power output when using high processing levels because it really increases the duty cycle of the transmitter. When used well, speech processing can really increase your average modulation level and make your stock radio sound like you're using more power. Compression can make a couple of dB difference in your signal, but clipping can add 6-9 dB to your signal and make a 12 watt radio with clipping sound like a 100 watt radio without clipping. And for those of you that worry about such things - it's completely legal! |
neil carrick (Unregistered Guest)
Unregistered guest
| | Posted on Monday, November 22, 2004 - 7:46 pm: |
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thanks...can any one recommend a particular speech processor for a radio such as the uniden 78LTW? Thanks again
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Bruce
Senior Member
Username: Bruce
Post Number: 1797
Registered: 9-2003
| | Posted on Monday, November 22, 2004 - 11:17 pm: |
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www.cbcintl.com/kits.htm |
Racer X (Unregistered Guest)
Unregistered guest
| | Posted on Tuesday, November 23, 2004 - 4:58 am: |
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For an AM radio I'd suggest a power microphone with compression just because it's the easiest. The trouble is I don't know of any currently marketed hand microphones that have compression. Some older ones do though. The Turner M+3, K40, and RF Limited's EC+3b. If you can find one of them new or used they would be a good choice.
If you'd rather go with the processor installed in the radio, I'd choose the Lou Franklin speech processor kit. The SP-1a speech processor isn't a bad choice, and the TenTec speech processor kit is a good deal at $14.
All of the speech processors require proper installation while the Lou Franklin and TenTec kits also require assembly.
Make sure you pay attention to the installation options of the Lou Franklin kit which can be customized for each radio. The custom construction instructions were on the last page of the instruction sheet the last time I bought one. That was frustrating because I had already assembled the kit by the time I got to the last page and realized I needed to make changes to the kit I just assembled. |
