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300w amp (up to 20w input)

 
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300w amp (up to 20w input)
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daniel
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Post 300w amp (up to 20w input) Reply with quote
what is the possibility of building on of these amplifiers with out any measuring equipment?
http://www.polyfet.com/tbplt3.htm
i am also assuming that none of these 300 watt fm amps would be ready to use without filtering?
thanks for any replies
Wed Dec 18, 2002 5:34 am
pcs
Site master
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Joined: 18 Jan 2002
Posts: 3063
Location: Radio Land

Post You're right Reply with quote
I would advice using spectral analyzer, although I am sure that
many have guilt it without one. Its more/less a no tune design
so I guess you could build one without it. But filter is definitely
necessary.

_________________
Best regards,
Marko - PCS Electronics
--------------------------------------------------------
Turn your PC into a FM radio station!
http://www.pcs-electronics.com
fax +386 4 2316 128
Wed Dec 18, 2002 11:22 am View user's profile Send private message Visit poster's website
Daniel
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Post Thank you Reply with quote
Thank you for your opinion, Marko, I know you are very knowledgable in this field. I will try and get ahold of a spectral analyser to test my amp.
If you are interested, I found a few good schemas, some even with pics of analysis. I could post some links.
Regards,
Daniel
Tue Dec 24, 2002 12:23 am
pcs
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Joined: 18 Jan 2002
Posts: 3063
Location: Radio Land

Post Sure, go ahead! Reply with quote
Yes, Daniel, a link would be welcomed by everyone, I'm sure!

_________________
Best regards,
Marko - PCS Electronics
--------------------------------------------------------
Turn your PC into a FM radio station!
http://www.pcs-electronics.com
fax +386 4 2316 128
Tue Dec 24, 2002 12:26 am View user's profile Send private message Visit poster's website
Daniel
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Post Links for FM xmitter amps and misc Reply with quote
Hi, first I'd like to apologize for my erratic online presence ^^ sorry all. If you are waiting for the links, here they are! Enjoy.

-amps-
http://members.tripod.com/~AMN92/index_main.htm
http://www.polyfet.com/tbplt3.htm
http://www.realfm.nl/eindtrappen.html (more than amps here)
http://home.wanadoo.nl/jplatenk/htm/Schemas.htm (phantomfm.org)
http://www.freeradio.org/tech/tech.html

-misc-
http://irational.org/sic/radio/
http://www.qsl.net/n9zia/wireless/appendixF.html
http://www.radio-locator.com/cgi-bin/nation
http://www.trsweather.com/top100/tools/tools.html
http://stereo-fm.net
Sat Dec 28, 2002 7:29 pm
Daniel
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Post phantomfm.org schemas Reply with quote
I quote this from my email, in regards to the 350 watt amp posted on the phantomfm.org site. (direct link http://home.wanadoo.nl/jplatenk/schemas/BLF278/BLF278_new.zip)

"Drive power has to be about 4 Watt.
Yes! only 4W is enough to make 350W of output.
The design is very clean and has an good filter at the output line.
Bias voltage has to be about 1,4 Vdc at the gate of the FET (both gates)."

So... if you have a PCI max with a 5W booster or one of the Max Pro's, you are ready for this 350W amp ^_^ if you can handle that much.

I have one question regarding this quote: you see I was told there is already a filter on this schema, does that mean I don't need an external one? Is it possible to tell be the schema how good the filter is? I wouldn't know because I'm not a professional electronic. Perhaps you could help Marko? I trust the word of the man, but I want a second opinion because as I said, I don't have easy access to test equipment.
Sat Dec 28, 2002 7:42 pm
StormiNorm
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Post BLF278 Reply with quote
From all appearances it has a filter on board...That still does not guarantee that your trnsmission will be harmonic free..Conducted Harmonic radiation and proper power supply filtering and dypass/Decoupleing is an area that should not be overlooked either...Remember it is when one has verified that all other potential sources of "induced' or passed along intermod products are reduced to the absolute minimum..it then and only then that one can expect the final LPF to do an effective job of filtering whatever possible harmonics is generated in the BLF278 Finalstage.

The fact that this particular circuit is what i refer to as a Broadbanded design with input tuning gain compensation etc.etc...one other reason to ensure that whatever signal is being amplified is relatively 'clean' harmonic content wise..because those harmonics will be equally amplified as well and may appear at the output of the BLF278 and the filter may not neccessarily reduce all the potential Low Frequency oscillations to the -60dBC Level.

And also the choice of Antenna is equally as important as well...The final stage consisting of the Coax feed and the Antenna of choice forms a tuned cct..and there are some cases whereby the choice of antenna and the level of attention paid to the tuning of the Antenna is equally as important...One might just have an Antenna resonateing at a frequency that is maybe a harmonic of lets say a frequency not properly attenuated by the filter.

Also one needs to consider the fact that as a single stage RF amp..then chances are no other type of filtering might be needed...But what happens when one decides to combine two modules with on board individual filtering???..What rules apply here needs to be considered as well..You all think about that aspect as well.

Respects...StormiNorm
Fri Feb 21, 2003 4:19 pm
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