Station Setup

Technically, the biggest problem I see is that it is 50 usec pre-emphasis.  The audio on standard FM radios in the USA is 75 usec. The difference results in muddy sounding audio.

so I would eventually need a Low Bypass Filter to level it out? I swear that I ordered the one recommend by this site.

A difference of about 1 kHz breakover comparring 50 and 75 us preemphasis response.

The transmitter preemphasis would start boosting audio frequencies above 3180 Hz at 6 db/octave but the US receivers would start attenuating frequencies above 2122 Hz at the same rate.

I'm sure trying to compensate at the transmitter is more complicated than simply EQ'ing the audio but it should brighten the audio.  

I wouldn't throw out the transmitter just yet.  Here's a little primer on Pre/De emphasis:

Info Here

also with that supplied antenna 10-20mW (i'm assuming it's the adjustable version in 10mW steps) TPO should get you about 200-250ft to a crappy radio which should be close to part 15 spec's. i have the 1 watt version of this transmitter.

I'm unhappy about the 50uS pre-emphasis, which is not the U.S. standard as mentioned already.

After carefully reading the link I cannot find any mention of what the pre-emphasis is for this unit, but other commenters seem convinced that it's 50uS, so I will go with them.

It is likely the pre-emphasis is set by only two parts in the circuit... a capacitor and resistor. But it would take a skilled radio engineer to calculate and install the right values.

I recommend talking with the seller and if they can't solve the pre-emphasis problem, get a refund.

Most would recommend a Decade FM transmitter.

Better yet, get AM transmitter from SStran.com for better coverage.

I would've gone with an AM transmitter had I found a go one for cheap. As for as right value, yes I would need a radio engineer. As far as putting it in, no. I am a skilled repairman with an evialent to Assoicates in Electrical Engineering. I can read a blueprint or schematic and I've built circuit boards for scratch. I must admit I don't have a firm grasp on the 50 vs 75 uS pre-emphasis, but I do understand the Hertz reference. And until I hook it up and play with, I wouldn't exactly know.

oh and Carl I understand what your getting at but if I can't find information on something I don't go with what the crowd say. That's as bad as guessing or assuming, and we all know what that can lead to.

I have the same transmitter, dressed in black though, and it's older. I've seen a lot of people with that model so it must be popular. I also noticed the preemphasis issue, it sounded good at first, then I noticed it seemed dull on better speakers and headphones, not bad but not like other stations.

I read that it's set at 50 microseconds since this transmitter is made for the world market, and outside of America 50 is used, it's a compromise, if it was 75 that would be too much treble for 50 areas. I tried an onscreen EQ in my player to jack the highs up, and it sounded better, but some songs with lots of highs would clip and distort.

I tried other things, and wanted a limiter to stop the overloads, it's something people say you really need with this transmitter, it doesn't have one built in like more pro transmitters. I tried some and wasn't too happy with them, because they weren't made for broadcasting.

Later I found a program called Sonos Limit on Vwestlife's Youtube. It's free, and I use it with Vwestlife's RADIO.FMT format file. It's real radio processing, and it has preemphasis and deemphasis settings.

The coolest thing is that you can select 50 or 75 EQ in and out. I set the Pre to 75, and the De-emphasis under Output to 50. What that does is add a perfect 25 microsecond boost to the transmitter, giving back your highs, plus it's processing on the full 75, so you won't get overloads.

I set it with the loudest track in my playlist, with the input meter peaking to -7, alc sitting at -13 or so with the volume on the transmitter to where it was a little less loud than a commercial station. I've never heard distortion again, unless the song was distorted itself!

This is my own invention, I've never read of anyone else doing this to correct transmitters for the US!

If anyone needs Sonos Limit from the video and can't find it, I'll put it on a download site for ya.

This Chinese transmitter, just so you know, at powers of 100mW and 500mW puts out way over the legal limit even with the stock rubber duck antenna.

As for the pre-emphisis, if you don't like the way it sounds you can always boost the treble at source a bit.

Not easy to change on circuit board of this one.....all micro surface mounts, and the main transmitter chip is under another board enclosed in a metal casing and to get to it means breaking it for sure.

 Also the one kc8gpd has is a 990 mW one (familiar with this) but power can be adjusted continuosly from 0-990 mW and is a different brand then the CZH 05B you have.

Mark

thanks Mark 

mat least that was easier to understand for a novice to radio but my only question just from that answer is you stated that at 100mW & 500mW is way over the legal limit but you mentioned that someone else had a variable transmitter that goes from 0-990 mW. I understand its variable and can be adjusted but then what is the limit?

The answer to the question I ask still hasn't been addressed rigt. You guys are giving good answers but it would be like me handing someone an adjustable fuse and say here, plugged it in. Don't worry about the voltages it variable. You can adjust it after we power it up.

According to the knowledgeble people here on the forum legal signal strength in the USA is 200 to 300 ft max with a hand held portable radio depending on how good the radio is. With a car radio it may be 2 to 3 times that. If you can still get your station over half a mile away in the car you know you are over the legal signal strength.

Mark

seeing how I can't get a straight answer at all, I'm calling it. How hard is to tell new people, hi welcome this is the equipment you need to start off with. When my transmitter finally gets here, I am just returning it  and giving up on Part 15 all together. Thanks for ruining it for me and to the admin, you might as well delete me because after I post this I am logging out and never logging back in.

There is no power limit it's the field strength that matters. 100mW and 500mW will put out to much field strength but I told you in the last post how to know if you have too much.

You were also asking about the pre-emphisis?

Don't quit part 15....no one ment to offend you, just answering what we thought you were asking.

Mark

The FCC rule for the FM band is based on field strength.  We can't tell you what the power limit is because that is not how the FCC regulates it.  

As stated in previous posts, measured field strength is the rule and the equipment to measure it is beyond the scope of the casual user.

You can use any power level you desire as long as the measured field strength is within limits.  Since you can't measure it, the rule of thumb is a range of about 200 feet as stated in the previous posts.  More power requires less system efficiency to keep the field strength within limits.

Yes, it's frustrating.  Be happy-don't worry...

i never asked about pre-emphasis, because I have no idea what the hell that is. I asked if what I had bought and I what I had, what else I would need.

you guys went on a tangent about pre-emphasis and other stuff that only experienced in radio would. I am a Novice which means I have never done this before. Saying its legal, a mixer board maybe a good idea and it will only broadcast 200' would have been easy to do but people are too busy about trying to make someone feel stupid.

people wonder why nobody wants to try anything new? It because of experiences like this. The transmitter is already on its way back and I have reacclamated the space for something else.