Are all CB Amps built the same?

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Are all CB Amps built the same?

Postby Phoenix » 11 Jan 2017, 08:42

Grey area for me but im interested to know, given all the bad press CB Amplifiers get with regard to clean output.I know most CB equipment is built to a price.But is the such a thing as a quality AMP for the CB spectrum and in your opinion what makes for good clean,efficient device.Brand names welcome. :clap:
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Re: Are all CB Amps built the same?

Postby Otter » 11 Jan 2017, 09:24

I know it's not answering your question, but I've had two Moonraker L100s and they have an input SWR of over 3. RM amplifiers seem to have a proper match.
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Re: Are all CB Amps built the same?

Postby kilimax » 11 Jan 2017, 10:17

Phoenix wrote:Grey area for me but im interested to know, given all the bad press CB Amplifiers get with regard to clean output.I know most CB equipment is built to a price.But is the such a thing as a quality AMP for the CB spectrum and in your opinion what makes for good clean,efficient device.Brand names welcome. :clap:


The main points I see with the vast majority of these "budget" amplifiers is input power, claimed output and filtering.

Most of these amps will fail if you overdrive them so you need to ensure you are staying well within the input limits.
The second point is that these amps have either no filtering or very poor filtering so for base station use, I would recommend a good quality low pass filter. Stay within the input power and your amp will stay realatively linear. Overdrive and the outputs will pop.

Finally,if you haven't already figured it out is ignore the claimed output power. It's highly exaggerated!
I would go for a bigger amp than you need, reduce the input power and feed that to a low pass filter.

The RM series of amps are ok so long as you observe the above.
What sort of power output are you looking at and is it for base station or mobile use?
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Re: Are all CB Amps built the same?

Postby Phoenix » 11 Jan 2017, 11:41

Thanks so far was maybe looking for homebase use i do have a few 30amp power supplies. Are there any amps that are filtered within the CB Band? I take your points on keeping the input low to reduce overdriving the device and not killing the output transistors.
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Re: Are all CB Amps built the same?

Postby kilimax » 11 Jan 2017, 11:57

The more expensive RM amplifiers designed for the HF spectrum do have proper filtering for each band so in that sense, they have filtering that covers 11m.
30A psu will do nicely.

A separate low pass filter will be just fine albeit that means another bit of kit in the setup but well worth it.
I use a Kenwood LF30 which works very well.
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Re: Are all CB Amps built the same?

Postby Buick Mackane » 11 Jan 2017, 12:17

Iv'e always wondered the same, Christ zetagi can't even screw the S0-239 Sockets on straight, Mind you they are cheap - ish. Quality gear = Quality prices
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Re: Are all CB Amps built the same?

Postby kilimax » 11 Jan 2017, 15:25

PLL02A wrote:Iv'e always wondered the same, Christ zetagi can't even screw the S0-239 Sockets on straight, Mind you they are cheap - ish. Quality gear = Quality prices


Some of the tests done on these cheap amps show some really concerning 2nd & 3rd order harmonics. In some cases, almost as strong as the carrier frequency itself, especially when overdriven. :thumbdown:

Regardless, I'd always want to have some filtering in place on the output and keep the drive level as low as possible.
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Re: Are all CB Amps built the same?

Postby Buick Mackane » 11 Jan 2017, 15:32

kilimax wrote:
PLL02A wrote:Iv'e always wondered the same, Christ zetagi can't even screw the S0-239 Sockets on straight, Mind you they are cheap - ish. Quality gear = Quality prices


Some of the tests done on these cheap amps show some really concerning 2nd & 3rd order harmonics. In some cases, almost as strong as the carrier frequency itself, especially when overdriven. :thumbdown:

Regardless, I'd always want to have some filtering in place on the output and keep the drive level as low as possible.



Yeah. Thats the reason a lot of these cheap amps give a high SWR reading, Out of band frequencies reaching the aerial. You look at the prices of small amateur band amps, They're usually considerably more than equivalent CB Band amps. Zetagi etc, Its an auld saying but its true,. ya get what ya pay for..I'm not a fan of zetagi at all, Christ did you see the state of the aerial switch box sickboy posted a while ago ? :shock: Utter sh1te,
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Re: Are all CB Amps built the same?

Postby kilimax » 11 Jan 2017, 15:43

PLL02A wrote:I'm not a fan of zetagi at all, Christ did you see the state of the aerial switch box sickboy posted a while ago ? :shock: Utter sh1te,


Lol, your right there mate. A bag full of extremely stinky testicles!

To be avoided at all costs!
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Re: Are all CB Amps built the same?

Postby Phoenix » 11 Jan 2017, 16:50

That would explain why 3 locals all using RM KL400's could be heard on 28.300 with an S8 signal ...These were talking on CH19 UK FM so the second harmonic was nearly as strong on the 10m Amateur Band...wonder were the third was ? :oops: Ermmm a bit more research required.
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Re: Are all CB Amps built the same?

Postby Buick Mackane » 11 Jan 2017, 17:29

The 2nd harmonic of 19 UK is 55.562khz, Unless i'm missing something here. Thats the reason the original ham bands are harmonically related 160m 80m 40m 20m etc, because back in the days when hams used to home brew gear if they got the filtering wrong they'd be transmitting on the related ham bands rather than commercial broadcast bands
Last edited by Buick Mackane on 11 Jan 2017, 17:35, edited 1 time in total.
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Re: Are all CB Amps built the same?

Postby kilimax » 11 Jan 2017, 17:34

Phoenix wrote:That would explain why 3 locals all using RM KL400's could be heard on 28.300 with an S8 signal ...These were talking on CH19 UK FM so the second harmonic was nearly as strong on the 10m Amateur Band...wonder were the third was ? :oops: Ermmm a bit more research required.


Yip! Remember too that any misaligned transmitter that isn't as clean as it ought to be because someone has tuned it for "maximum readings on an oscilloscope" (I love that one) will only get worse once a dirty amp is smoking full pelt!

Choose wisely.....
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Re: Are all CB Amps built the same?

Postby Buick Mackane » 11 Jan 2017, 17:39

kilimax wrote:
Phoenix wrote:That would explain why 3 locals all using RM KL400's could be heard on 28.300 with an S8 signal ...These were talking on CH19 UK FM so the second harmonic was nearly as strong on the 10m Amateur Band...wonder were the third was ? :oops: Ermmm a bit more research required.


Yip! Remember too that any misaligned transmitter that isn't as clean as it ought to be because someone has tuned it for "maximum readings on an oscilloscope" (I love that one) will only get worse once a dirty amp is smoking full pelt!

Choose wisely.....



More like a stethoscope :lolno:
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Re: Are all CB Amps built the same?

Postby kilimax » 11 Jan 2017, 17:41

PLL02A wrote:The 2nd harmonic of 19 UK is 55.562khz, Unless i'm missing something here. Thats the reason the original ham bands are harmonically related 160m 80m 40m 20m etc, because back in the days when hams used to home brew gear if they got the filtering wrong they'd be transmitting on the related ham bands rather than commercial broadcast bands


It's 55.5625Mhz. 2nd harmonic is 2f where f is the fundamental.

At 28.300, this is likely to be some sprog from the TX or possibly intermod/mixing products in the receiver. Won't be the actual 2nd harmonic.
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Re: Are all CB Amps built the same?

Postby kilimax » 11 Jan 2017, 17:44

Best & cleanest way if possible would be to get your gain from your antenna system. That way, you benefit on both tx & rx but sometimes, we do need a bit of assistance!
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