CB shop black list.

Lol..Every time i hear that whistle i think of a youtube vid of a ####tiel that whistles it all day..

 

I guess I’m confused here and what you are saying. Do you mean that his two attenuators, one for the oscope, and one for the spectrum analyzer is causing the harmonics?

 

The harmonics are produced by the radio. The amplifier is doing it's job by making them larger. He blames the amplifier for producing them.

 

Well, I think he’s right. When he bypassed the amp, the radio looked clean to me. When he changed the radios power level from low to high, the signal still looked clean. The harmonics didn’t appear until he turned on the amp. There’s other videos on the net that show how amps that aren’t correctly adjusted, can distort the wave form which causes the harmonics. But I’m not an amp guru, so this is just speculation on my part.

 

Look closely at the bottom line and tell me how clean it looks. You can clearly see the Spurs that are the source of the problem. In the video he even admits he sees some harmonics coming from the radio but he says that they are very low and he thinks they don't matter. The amplifier is simply doing what it was supposed to do and that's amplify what's put into it. A stock unmodified radio would look much better than this. Amps are no joke and I don't recommend them for anyone unless they have complete confidence in the signal purity of the transmitter. Most of these radios have mismatched final transistors which creates IMD and that would be Amplified going through an amplifier. You can't just tune that stuff out by turning screws. Replacing the factory finals with a beta-matched set is a critical first step to cleaning up the output of the radio.

 

Okay, I first watched this video on my phone. I watched it again on my laptop, and you are right, he did admit there were some small spurs in the noise floor of the radio, and it was obvious on the bigger screen. I guess since Mike is a break/fix by the book type of tech, he recommends a LPF to his customer from Canada, since that would be the cheapest way to fix the problem, rather than rebuilding the TX section of the radio? He talks like this is a common problem with these cheaper amps, and I wouldn't be surprised if that is a correct statement. Anyway, good catch Rabbi.

 

So would an expensive amp ignore the radio's spurs?

 

Nope. Not unless the amp filters the input from the radio, or a filter was used before the amp. I have a radio that sounds and works great that has spurs almost invisible, and I would never connect that thing to an amp.
( until it gets rebuilt with a beta-matched set of Palomar ERF2030+ and the spurs are gone)
Those spurs would be much larger on Mark's bench, and Mike wouldn't be able to see the spurs on my first AT-6666.

 

FINE TUNE CB SHOP. HARDRIVE 163 NM Got a radio from this guy, brand new 2970n4. Didn't work right. Receive was messed up and couldn't hear really well. Radio put out about 300 watts pep with the (4) 2970s. (I know we don't talk on PeP, just facts) Radio checks were not all thumbs up either. Some said I was too quiet, others said my audio started loud then dropped off ### I modulated. Messed around with the radio for about an hour before noticing how hot it was, and how crappy the recieve was coming in. Sent it back to him, and he told me I was talking on FM, and smoked the pills.) Having a 2995dx already, I know how to operate in AM mode and every feature on the radio...even if i were in FM, why would a radio have FM mode and blow itself up? A month went by and he sent it back with argument over user error in the hour I had it. Called me up after he saw it was delivered and asked me how I like it. Told him its the exact same, and everyone in my local area was telling me how sorry they were for me. Spent over $800 with him, and I told him I was unhappy, and maybe something he is overlooking. I was answered with a moody Hardrive, who argued more and more, then hung up on me, and I've never heard from him again. Never cussed at him, never was disrespectful, just told him the facts. That's all I have to say, he still hasn't made it right, and I won't be using him again. As for the radio, I sold it on ebay for a huge discount, letting the customer know what was wrong with it. Thanks for reading, Josh Toomey 440 southern-cal, waving around Joshua Tree

 

You forgot to mention you shorted out the coax on the Jerry rigged power supply.
Details like that are very helpful in determining the cause of the problem.
Failure to follow instructions always ends up with bad results. The symptoms you described indicate you were attempting to transmit in FM mode and when you shipped the radio back to mark you left it in FM mode.
It might have been prudent to switch it back to am mode before shipping it back to mark in order to make yourself look more knowledgeable in regards to the operation of the radio.
Honesty and integrity go a long way towards gaining our respect. Withholding certain crucial details is kinda dishonest to say the least. As soon as Mark finds the pictures of your jerry-rigged power supply with the arcing and sparking that was going on I can share them in case you deleted your copies of those pictures.