VK3YE's minimalist 40m DSB : low pass filter

[Steve Smith]

Because of the requirement here in the U.S. for -43 dBc spurious output products, I will be using the W3NQN output filter found, curiously, on the GQRP site:

http://www.gqrp.com/technical2.htm

No increase in parts but I believe it will improve the filtering with no increase, or at least minimal increase in loss.

73.......Steve Smith WB6TNL

[Jason W6IEE]

I want to analyze this a bit more, as I have an underutilized spectrum analyzer. ;)

dBc... decibels relative to the carrier...  Theoretically, if the carrier is surpressed down to nil, it'd be pretty hard to pull that off, right?

Also, does that requirement look at the first harmonic, or what?

This will get interesting!

Thanks,

Jason W6IEE

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[Ian Wilson]

dBc just means relative to the mean transmission power (while you are
actually transmitting something). So if you are radiating 1W nominally
than -43dBc means you should not be radiating more than 50uW of
spurious emissions.

How's the coffee? Raining there?

73, ian

[Jason W6IEE]

"means you should not be radiating more than 50uW"

At 2x the frequency of interest, correct?

Coffee's great, any rain isn't apparent past the window screen. ;) Had bits of rain in Glendora and Pasadena driving home from San Diego county last night. (yeah, i take a convoluted route)

Steve is likely better situated to report on the storm front.

There's an idea for holding down 7200: its the "OMG its raining in SoCal" net!

;)

Thanks,

Jason

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[Ian Wilson]

I would imagine the -43dBc is summed over all emissions. Of course
with a nice tube TX this is probably 90% second harmonic. With solid-state
you could be pumping out UV :)

--ian

[Steve Smith]

[Jason W6IEE]

Thanks!

I'm going to try to build the original filter (assuming the junk box cooperates) and then measure. We'll see if we get a comb generator or not. ;)

-Jason

[Steve Smith]

The Fed's. state, "For transmitters installed after January 1, 2003, the mean power of any spurious emission from a station transmitter or external RF power amplifier transmitting on a frequency below 30 MHz must be at least 43 dB below the mean power of the fundamental emission." To me that translates from Fc to daylight. But whatever. I just try to do my best to comply.

The coffee is good here too. I'm on the 2nd cup.

Not raining at the moment but there's a front coming in from offshore but appears to be breaking up as it moves ENE.

Great day for soldering.

S.S.

[Jason W6IEE]

Ok. I'm going to speculate that the 1st harmonic will be strongest. Will build, then measure!  I have an HP 141T with the RF section plug in that goes to 110 or so Mhz. I have the sweep generator for it as well, but it was obtained in a non-working state, this project might get me to dig into it.  Also have an HP 8924c, more like a VHF/UHF service monitor, but will work as an SA/TG down in HF, with reduced accuracy.

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[Robert Nickels]

On 11/16/2012 11:03 AM, Jason W6IEE wrote:
> We'll see if we get a comb generator or not. ;)
>

My guess is your "other" sideband will get noticed a lot sooner!

73, Bob W9RAN

[Michael Tauson]

From: homebrew-du...@googlegroups.com [mailto:homebrew-du...@googlegroups.com] On Behalf Of Jason W6IEE

There's an idea for holding down 7200: its the "OMG its raining in SoCal" net!

 

The Pineapple Express.  Hawaii’s little gift to the West Coast.  :-)

 

Is there any reason it has to be on 40m?  Could 20 and higher be considered as well?

 

Best regards,

 

Michael, WH7HG, A&P 1803851 Ph: 1-866-733-0218

I live with a maniac at home, my other me.

http://www.nationalmssociety.org/chapters/NTH/index.aspx

http://wh7hg.blogspot.com/

http://kludges-other-blog.blogspot.com

Hiki Nô!