The quote tag got ruined in the post, It's fixed now.
was anything I mentioned untrue (I might not have a complete understanding)?
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How much audio power one typically see in CB and Export Radios
- Thread starter Onelasttime
- Start date
was anything I mentioned untrue (I might not have a complete understanding)?
To me direct inject seems like something that is real easy to do but hard to do right, if you're going to bypass all the limiters in the radios mic amps the onus is on you to monitor/limit everything yourself. Not everyone does this but you can't blame that on those that do keep on top of things.
If I was going to get that crazy with the audio I would consider an oscilloscope and a SDR receiver with a panadapter type display requirements for monitoring purposes.
PS: Is that your radio in that clip you posted JoeDirt? if so that is one nice setup you have there.
If I was going to get that crazy with the audio I would consider an oscilloscope and a SDR receiver with a panadapter type display requirements for monitoring purposes.
PS: Is that your radio in that clip you posted JoeDirt? if so that is one nice setup you have there.
SDR receiver is next on my list, i'm going to set it up near the dummy load when I test the hi-fi/direct injected radio again to see how wide it really is with voice / music, I will then get a little idea of how limited the microphone I am using is.
There has got to be a simple software solution that can reveal how "wide" an element In my microphone I have, can anyone offer a suggestion?
There has got to be a simple software solution that can reveal how "wide" an element In my microphone I have, can anyone offer a suggestion?
It is extremely easy. You just crank up mic gain to the point that the ability of the ALC circuit to limit it to a reasonable level is exceeded. You can transmit 30kHz wide on any amateur radio by whacking the mic gain right up, turning the processor on and whacking that up too. You don't even need to crank either of them up to full.
You bleed over the adjacent channels. The limits are defined in Part 95 certification. Who cares? The people who you're bleeding over on the adjacent channels and the FCC. The FCC recommended fining a CBer in New York $22,000 for operating a 150W linear and interfering with other CBers. The base fine for both of those totals $17,000 with an additional $5000 being added because he continued to ignore them.
http://www.arrl.org/news/fcc-ups-the-ante-in-proposing-huge-fine-on-cb-operator
This was following a case where they fined a guy in Florida $14,000 because he refused to allow them to inspect his station after they'd monitored his transmissions.
http://www.arrl.org/news/fcc-proposes-to-fine-cber-14-000-for-not-permitting-station-inspection
Yep, just plug your mic into the input on your computer soundcard, use some software to generate white noise to play into the microphone (plenty of apps for a mobile phone etc) and use some free audio spectrum analyser software to display the output. You'll then get a response curve for your mic up to 44kHz/192kHz or whatever the soundcard is capable of.
However the mic element response width isn't what controls how wide your transmission is. Filtering on the radio and spurious harmonics caused by overdriving the radio is.
That's where the processing comes in to severely limit what gets directly injected into the radio (using software "filters"/e.q. ) on my test setup, later I plan to make a buffer/filter circuit.
What is the problem is the levels that are injected, not the bandwidth. It is the overdriving of the inputs of further stages down the TX chain, not the bandwidth which cause the wide signal to be transmitted. It is in those stages where the spurious signals are generated.
If the audio gear you're using is a line level output this is several magnitudes too high. Line level is typically a volt, volt and a half and you need to be using millivolts.
For testing I have the over-all system volume level set at 20% of max of what the PC soundcard can do, further I then use Dolby Home Theater to set E.Q. and other level adjustments, on a nearby receiving CB I can observe the received signal start to sound overdriven by adjusting levels on the pc up, at one point after lowering settings so much it got clear, and then I lowered drive a little further until the signal was not as strong, I'm fairly certain it's clean (not over-driven as it sounds great on a stock radio), I need a spectrum analyzer to get the full picture though.
I am going to voltage check the output, thank you.
I am going to voltage check the output, thank you.
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I said as long as your not interfering who cares! That was a more aimed to the ham bands. The CBer was obviously interfering. So answer my question even on the CB band how is it that my signal that I recorded is considered interfering or bleeding over?
I think your confusing operators, you have operators that operate their equipment in a negligent fashion causing interference with a really wide transmission, usually thats unintentional because of there ignorance. Usually these operators dont direct inject but if they did their signals going to be wide causing interference regardless because they just dont care.
There are plenty of us who do care about a clean transmission, all I have done is try to help people who really want to learn and achieve this (like myself). I dont think its fair to group all of the CBers in one category. I encourage constructive criticism and try to keep an open mind. You should roll your flex out to 8khz do a recording for us!
This not %100 true with CB. CB radios offer no harmonic filtering like a ham rigs for AM modulation. Regardless if you direct inject or not the radio is still capable of producing the same harmonic interference.
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Some guys are set in their ways and any attempt at better than communications grade audio is evil. Anyone that uses ALC on AM is a dimwit, AMC is a good thing but a different type of circuit. Limiting audio peaks to prevent over modulation is good...anyone that's using external audio gear will eventually find an external audio peak limiter works better than the mod limiter in a CB or ham rig. ALC limits power from an amplifer stage in the radio or in an external amp. A great way to flat top the positive peaks and sound like shit on AM. Works fine for a SSB operator if used conservatively.
Joe dirt is talking about a transmitter capable of passing 30khz of audio bandwidth and a someone that's been licensed since 2009 with a arsenal of plug and play appliances tells him this....
That's about as smart as spinning the vfo with an electric drill while transmitting.
Joe dirt is talking about a transmitter capable of passing 30khz of audio bandwidth and a someone that's been licensed since 2009 with a arsenal of plug and play appliances tells him this....
That's about as smart as spinning the vfo with an electric drill while transmitting.
Someone who did a degree in electronics engineering, has been an electronics engineer since 1986 and who has a wall of first place certificates for CQ-WW, CQ-WPX, IARU HF and ARRL International DX contests. What are your qualifications?
You seem to confuse having a license with having competency whilst discussing technical issues on a forum about an unlicensed service.
Another engineer on the CB forums....
Most engineers that aren't taking out of their their ass wouldn't use DX contests as credentials. I have no electronics credentials to brag about and contesting isn't my thing. How much of your engineering background involved AM radio and how many of your contests have been using AM?5/9 in Texas QRZed