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New Kid On The Block
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Registered: 11-2016
Posts: 2
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Low Pass Filter - a must?


Hi all,

Ham Operators use always a Low Pass Filter after an amplifier or the most amplifier have a LP
Filter already build in.
When I watch some CB Activities with a Amplifier (RM Italy) they don't use a LP Filter.
The RM Italy KL-203 Amplifier have not a build in LP Filter. It seems nobody takes care
about the harmonics (Ok, analog TV is mostly dead, so nobody gets disturbed).
Do you use a Lowpass Filter after an Amplifier (Max. 100W Out)?

Many thanks for your opinions!

Ben
 
4/Dec/2016, 4:49 pm Link to this post Send Email to 15FB572   Send PM to 15FB572 Blog
 
Spac3Monk3y Profile
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Freebander
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Registered: 06-2014
Location: No Place Like 127.0.0.1
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Re: Low Pass Filter - a must?


No because i have no use for a amp... emoticon

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31/Dec/2016, 2:35 pm Link to this post Send PM to Spac3Monk3y
 
Hot Fusion Profile
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Management
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Registered: 03-2008
Location: South West England
Posts: 1372
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Re: Low Pass Filter - a must?


I suppose the sensible answer would be to say yes, use a low pass filter.

Amps come in 2 basically different types - tuned output, or wideband.

The wideband CB types, for cheapness, tend not to have any filtering and so it is possible for them to radiate significant harmonics.

The tuned output types include all valve amps, and some solid state amps. A little solid state Zetagi b150 I have here has a tuned output stage, so this would tend to reduce harmonics.

One way to tell is to open the case and look for open-wound wire coils - this would probably mean a tuned output. The presence of rings of dark material (ferrite) with wire coils passing through would suggest a wideband output stage, with no filtering.

Hopefully that hasn't confused anyone, but grab a decent Kenwood LF30A low pass filter and all will be OK with the world. emoticon

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Andy - FB107
1/Jan/2017, 7:46 pm Link to this post Send Email to Hot Fusion   Send PM to Hot Fusion
 


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