50 watt mod? Gimmie the straight scoop...

[cbshack]

cb radios

Justin you are correct on several fronts. My only real complaint is the adjacent channel rejection suffered a bit after the receive mods. It is more sensitive and quiet.

I thought John Fatori is the owner of MJ Products. His name shows up on some of the shipping labels.

I was recently told by Northstar (from this forum) and JR from Ramko that a gentleman named Mark is the owner of General, some Superstar radios (121 for example), and Connex. He doesn't like to be known I am told.

I must have misunderstood what you stated about certain importers/manufactures not really knowing much about cb and 10 meter radios.

Do you think that Mr. Peng is getting out of the business with all the money he has made? Maybe he is looking for a change. What do you think will happen to Ranger?

I guess without all these radios out there to repair, modify, and sell you and I would be making a living another way.

I am good and will not bother you. I just wish I would have been contacted before some of the work was done to my radio?

Did John Fatori retire? I remember him telling me something to that effect. He is a tough old dog!

Have a good one, Ben in Florida

 

[C2]

Ok cool, I hope you guys work out your personal business and the rest of us can get back to the discussion.

What happened, I thought you wanted to "talk?"

Just never mind, I've seen enough.

 

[King Mudduck]

Some of these posts really flip me out.Time and time agian i hear and see people crying about poor work done by a lot of those so called cb techs,then when you find a tech like Justin you do all you can to tear him down!His mods work plain and simple.Having owned a few cobras and one 48T that he did for me i have always gotten outstanding reports from others.So if you guys cant accept that or the fact that there are a few(very few) techs out there who may know more then that good ole boy cb shop down the street then i guess that just to bad for you!

 

[NorthStar]

I believe this topic could go on and on. Always someone's opininion will differ from the next guys. I hope we can get back to the topic.

 

[Switch Kit]

Once again your prop's are noted . but who is downing the dude in the first place ?(and if they were ? that's just another part of the business.you can please some of the people some of the time but you just can't please all of the people all of the time) I will say this much ...this is just another person who works on radios to me , just like all the other hundreds of them through out the country ....and each one of those hundreds have some kind of happy customers ...IM not going to bow here . But as I said ,the prop's are noted. I have nothing to be impressed about nor do I want to be. I kind of think we are way past the subject here Northstar , but that's par for the course and here I sit still feeding on it. (bad me) Let it be noted by many others ,Justin is the king guru of radio modifacation and repairs , there's no body else but him here on the WWRF ....so everytime you have the chance ,jam it down somebody else's throat ,it will help him put gas in his car.....this is all good .....but questions get asked and never answered ? ....it just turns into a damned ad campain ....IM personally not out to pay for anybodies services ....just trying to help or be helped here.

 

[cbshack]

50 watt mods

Not all mods work for everyone. We offer a super tune for example for the Cobra 29 and Uniden 78. This is just one way to do it. We change out the final, put in a swing kit, detach one leg of the limiter if the customer asks us to, sell them a rk-56, and add talkback if they want. On our Coaxial Dynamics meter which is similar to a bird we see 40-60 watts on AM peak with an ahhhh. Some customers want the limiter left so we do that also. Usually get the 35-45 watt range then.There are other ways to achieve this. Ours is one way that works for us and our customers. Hope this helps.

 

[Switch Kit]

Your honest CB-shack , it works for you and your customers and that's all that really matters , if just about everything that is done to these radios in one way or the other is illegal ...just tends to make me wonder how truly bad some mods are to others ? .....I can hear it now ...ours are just cleaner then there's are !! there just hacks !! .....Black List were made by the same people that were on somebody else's. My guess is this CB-Shack ...if you had done a number of radios for a handful of WWRF members and they were more content then not ...you might be getting some props along the way as well...at the same time that doesn't make your work the best it can get according to others points of view and leave it to "them" to find it nessasary to point that out to you when ever they find the chance....From what I have read .....nobody prop's this dude up better then himself ......these guys who get there radios done for the most part do not understand the differents.....the only thing they truly care about is that it works and works well or what those birds and dosy swing .....99.9% of the time it is about the mighty green backs.....not nessasarally the answer to anybodies questions around here ....Why ? that could well be the differents between money in there pockets and it going else where .it can be a rock and a hard place at times .....you get a radio done and you get it back and your not happy ....you try and work with the folks that did it for you and then you begin to feel jerked around ....now your beginning to get a little more pissed off when your not getting any results ....whats a guy to do there after ? Get on the radio or Internet Forums and vent your feelings ? and then get blamed for bad mouthing somebody who could have more then likely deserved it anyways ? ....that's what I meant between a rock and a hard place ....damned if you do and your damned if you don't ....and when it comes to these Froums ..I certainly don't make whats fair ....I just have to abid by the rules and regs the best I can ...and even then ....there really are no garentees . Mans got to do what mans got to do. Weather or not questions or answered or not ? ....Sometimes it just amounts to ones attitude there after. Reminds of the time when I baught a top of the line PC ...within a few months of buying it ,I started to get upgrades for it as they came along , I would ask the tech a few questions and he really didn't feel the need to answer them for me , but yet he would take 40 dollars to plug something in and download the drivers for me because I couldn't figure them out for myself ....one other time he nicely told me that why should he tell me anything because he went to school to learn his trade and had paid 40 grand to do so......to each his own I suppose.

 

[King Mudduck]

And i know your right!

 

[cbshack]

50 watt mods

Switchkit you make several good points. I really enjoy this forum. Most of the time you get honest answers. Sometimes you don't. I don't claim to know everything but I believe I can make most cbs sound and receive well. I have modified ham radios in the past. Not everything works for everyone but hopefully we can get some good opinions as to what works on some vehicles and what radios are being made well. I would be more than happy to help whomever I can. Just PM me and I will try to respond. Peace to all, Ben in Titusville, Florida.

I use a Cobra 29 and a Uniden 78 at my store. I use a Kenwood 450 at my house and I do use the Grant LT that Justin, Frank, and their morning tech upgraded for me in my truck. I hope that this Stryker radio that Justin helped with is the best 10 meter our there. I really don't like most of these radios. They are just too noisy for my tastes. And yes, I do sell them because that is what the my customers want.

Don't forget the importance of a good antenna and coax.

I just started doing this full time August 1st.

I'm back quiet!

 

[C2]

Really it doesn't matter any which way, the second harmonic is down by -32db or better, with the trap tuned properly. The fact of the matter is... I don't have time to play online games, it's really not worth it.

Given your 50 watt output, that puts your second harmonic at a 32 mW level. That is close to a 50 mW ERP that some cheap FRS radio's put out.

Standard CB radios are specified with harmonics below -55 dBc. That is just about as low as 0.01 mW. So your 2nd harmonic increases by nearly three thousand percent (3000%).

Lets see, 16W to 50W output is a 5dB gain, but the 2nd harmoic goes from 0.01mW to 32mW, a 34 dB gain.

Well, that is the nature of the beast. But that is also for sure a TVI monger.

 

[Moleculo]

but the 2nd harmoic goes from 0.01mW to 32mW, a 34 dB gain.

Well, that is the nature of the beast. But that is also for sure a TVI monger.

If your TV exhibits signs of RFI from 32mW of RF, then you need to take it back under warranty. I don't know about where you live, but around there, there's a lot more RF traffic on 27mhz's 2nd harmonic (54 mhz) than 32mW from a CB. 6 meters traffic comes to mind pretty quick. Oh yeah, all of the California Highway patrol runs around 42mhz AM, and CalTrans is around 47mhz AM. I think my neighbors baby monitor puts out a couple milliwatts on 49mhz. Funny, I'm pretty sure that the CalTrans station that is about 1 mile down the street puts out more than 32mW of power. I must have a really good TV because I don't hear them.

All sarcasm aside, TV's and other consumer electronics are supposed to filter out and shield themselves from some RFI. 32mW is well within tolerable specs of what a TV should be able to handle. Now, if you turn that 32mW into a much higher level of power by amplifying it, that's a different problem. And another thing....most people use Low Pass Filters on their station anyway. If they don't, they should, which would make it a moot issue anyway.

Oh yeah, and most FRS radios are 500mW, not 50mW.

 

[C2]

FRS is allowed 500 mW maximum. Most with the little stub antenna put out significantly less. I have looked at many of the independant lab test results submitted to the FCC for certification. A $10 pair that I have are 50 mW ERP.

Many receivers of the ham orientation will show an S9 signal with 74 dBm input. That is less than 1 nanoWatt or is 45 microVolt. CBs are sensitive to much less than 1 microVolt, but typically show S9 at 100 microVolt.

The bottom edge of the over-the-air TV channel 2 is 54 MHz and the upper edge is 60 MHz. Add in some of the IMD products likely present in the 50W mod and put them at the lower edge of the TV spectrum, and you get TVI, no matter what shielding the TV has. BTW, filtering and shielding are NOT designed to filter and shield the fundamental that the TV should be receiving in the first place. A TV cannot filter out the second harmonic of a 27+ MHz signal.

6 meters upper edge is 54 MHz. There is no "traffic" of the sort in the TV channel's bandwidth. Not from 47 MHz or any other service.

I am talking about a 54+ MHz harmonic that falls right in the TV channel bandwidth being supplied to your antenna at a 32mW level. That causes TVI and is not the fault of poor filtering or shielding on a TV set. Not matter what you do. Granted, most run an amplifier, which makes the situation much, much worse. And to think a cheep drake LPF is going to solve your problem, think again. How much do you think that drake will suppress that harmonic? At best 72 dB. How much did your amplifier bring it up? It is not going to be enough to get it below the sensitivity of the TV receiver.

Number one complaint about pumped up CBs is TVI. Justin should add more filtering when he does this type of mod.

 

[Moleculo]

OK, we need to be a little careful here interchanging terms like ERP, dB, and dBm. Not that it was used anywhere incorrectly, but many won't follow it. Originally you said FRS radios put out 50mW. Then you changed it to 50mW ERP. I fully believe the ERP statement given the lousy antenna and half charged batteries, but that's not what was originally said.

Many receivers of the ham orientation will show an S9 signal with 74 dBm input. That is less than 1 nanoWatt or is 45 microVolt.

How is the signal fed...directly to the input or is the signal just being broadcast right next to the receiver? Certainly if the generated signal is right on the same frequency as the receiver, I would expect it to show high S unit on the receiver at close distance. If the generated signal is more than 10khz or so away from the receiver's setting, I would expect the signal to fall outside the receiver's passband (we're talking about AM/FM, not SSB, right?)

Now I fully realize that an TV probably doesn't have such a sensitive or sophisticated receiver as a decent ham rig with selectable filters, adjustable passband tuning, and the like. Perhaps a TV doesn't have as sharp of a passband cutoff as a ham rig? But it still has to be able to discriminate between signals that are on it's fundamental frequencies and those that are adjacent.

For channel 2 in the U.S., the video is at 55.25 MHz, the color carrier is at 58.83 MHz, and the audio carrier is at 59.75 MHz. That means to get CB 2nd harmonic RFI on the fundamental video carrier frequency on a TV, you would have to be transmitting on 27.625 MHz. Now, I realize that the video frequency is modulated from the carrier of 55.25 MHz minus 1.25 MHz to plus 4.75 MHz. However, the video in the carrier minus 1.25 MHz range is rolled off to give us only dark gray to light gray transitions.

Are you telling me that a TV's receiver is so lousy that it will pick up a 32mW signal on 54.37 MHz (CB channel 19, second harmonic) which is almost 1 MHz away from the lowest carrier frequency needed for channel 2? Even if the CB is really trashy and taking out a few CB channels on either side, it still isn't close to any of the fundamental carrier frequencies needed for channel 2, and it is only in a small portion of the video frequency range needed for grey color transitions.

Again I'll go back to filtering. Both the color and audio frequencies for channel 2 are not very adjacent to the 2nd harmonic from a CB signal. I would be surprised if 32mW gave any RFI on those frequencies. If it is, simple low pass filtering will solve it. Is it possible that 32mW might give us some RFI on the black & white portion of the signal? I suppose. Is it likely? I doubt it. Maybe I'll go home and put a TV right next to my radio and see for myself.

 

[Moleculo]

Since I actually have a modified 50 watt Justin tuned Cobra 29, I think I'm qualified to report test results of the 2nd harmonic's affect on TV broacast channel 2.

I took my handheld RCA, piece of junk color TV with a 22" antenna and ran some tests. If there's ever a little TV with no shielding or filtering, this is it.

1st test: CB run into dry dummy load with TV sitting next to dummy load: very, very minor waviness on TV with CB on channel 40. With CB on channel 5, nothing. TV placed 10 feet away from dry dummy load: channel 40 has barely a quiver, channel 5 nothing. TV placed two rooms away (about 30') nothing on either channel.

2nd test: CB run into I-10K antenna on roof, 32' to feedpoint, test only performed on channel 40: TV right next to CB: very minor waviness on TV. TV placed in center of house, directly under antenna feedpoint: even less, very subtle waviness on TV.

3rd test: CB run into Bencher Low Pass 1.5KW filter into I-10K: TV placed 10' from radio: very, very subtle waviness hardly perceptible yet there. TV placed directly under antenna in center of house: even less waviness, barely enough to mention.

Asking neighbors next door if they noticed any interference: They report nothing.

So is it possible? Looks like it. Is it likely? I think the answer is, "it depends", and probably more doubtful than anything else. It's certainly easy enough to filter out a small amount of RFI like I reported using several basic techniques. Is it a "TVI monger" ?? Hardly. IMO, all that really matters is whether or not your wife or neighbors complain. And don't forget: all this really only matters if you're pulling in broadcast TV. If you're using cable or satellite, it's pretty much a moot issue.

 

[C2]

That is interesting.

Shielding is there to keep unwanted RF from getting in the circuit through other means than the antenna input port.

Filtering is there to prevent unwanted frequencies that are outside the passband (the channel you are trying to receive) from getting in the circuit from the antenna port.

Neither the shielding or the filtering of the TV will do anything to keep out the 54 MHz harmonic because that is in the passband (channel bandwidth) of what you are trying to receive. Both of these, however, will do their part to keep out the 27 MHz (and 42, 47, et al other MHz) fundamental.

I would hardly expect any TVI to be observed while running a dummy load. Dummy loads are designed to not radiate.

Directly under your I10K is not really the best place to conduct your test. The neighbors arial, however, would be good. Assuming they have one and were even watching channel 2.

I agree that Cable or Satellite helps imensly, as well as does any digital mode. Soon enough, OTA will all be digital anyway.

So it might be a moot point, but TVI remains one of the biggest complaints against CBs and one of the hardest problems for CBers to solve. Much of the problem is as Justin points out, but that is really no argument in favor of allowing very high levels of harmonics and IMD.

Most of the CB amps can run quite cleanly, if the radio is properly set up and the amplifier is not over driven. The only place where class C really belongs is for FM or CW, not AM or SSB.