Yes, impratical. I simply wanted to clearly draw the
distinction between the function of the "pi output
filter" and the function of the "IF filter".

The Pi output filters limit harmonic content, the IF
filters "protect" or reject  adjacent channels/frequencies
(depending on whether xmit or receive mode is 'in play'
at the moment). Even on the HF bands some higher-frequency
voice content is effectively filtered by the "SSB filter"
and kept from appearing on the adjacent channels (thereby
reducing transmit splatter).

Just because if is called a "SSB filter" do not be
confused, it is an "IF (Intermediate Frequency) filter"
and usable on both CW or SSB (or capable of cleaning-up
and reducing the BW of a heteodybable 'spark' signal).
For AM is may not allow the carrier to pass and therefore
not allow "envelope detection" to work to demodulate the
AM signal in lieu of the normal action of the SSB 'product
detector'.

I apologize to the list beforehand for any who take
exception to this continued discusssion. I expect this
should be my last response on this topic with esteemed
list participant Peter.

RF Jim


----- Original Message -----
From: "Peter L. Peres" <plp@ACTCOM.CO.IL>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Friday, September 13, 2002 2:17 AM
Subject: Re: [EE]: Switching Higher Voltage---->Legal Spark Xmtr


> On Thu, 12 Sep 2002, Jim wrote:
>
> >> What would a normal transmitter use, three to five
> >> stages minimum pi output filter ?
> >
> >These "three to five pi output filters" (the key, operative word here
> >is "output") remove *harmonics* (integral multiples of the signal)
> >and do not influence in-band, channnel-to-channel (adfjacent channel)
> >performance.
> >
> >THAT'S what duty of the sharp SSB filter (on a normal, pre-DSP radio).
> >(That SSB filter is used in both xmit AND receive modes BTW).
>
> We are talking CW only here. I did not suggest voice transmissions on a SG
>  tx. You are right, the phase noise of a spark gap generator is terrible.
> OTOH a real enthusiast could fill a room with 9-12 LC tank circuits built
> on aircoils put in empty steel filing cabinets and homemade oil or
> polyethylene capacitors and go on air legally with CW on a spark gap I
> think. The point is, that it is possible to achieve, although not
> economical and probably of interest only to dedicated amateurs.
>
> Peter

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