Post by thread:[EE]: Switching Higher Voltage---->Legal Spark Xmt

> Of course you know that there are people who build and operate SG > transmitters for fun in your country ? A SG transmitter can be made to > meet FCC rules with a lot of filtering, so it can be done. Hmmmm ... *this* I would like to see. Your claim, roughly translated means that you are able, through some miracle of post-spark gap filtering of reducing the bandwidth of said sparkgap emissions to remain within allowable, legal limits for currently legal emissions. That bandwidth being roughly six kiloHertz (although this *might* be legal - you will make no friends on the bands as this is equal to the emissions of a double-sideband AM transmission) *plus* you will need somewhat steep-sided (rectanagular) skirts extending outward from the +-3 kHz points in order to minimize adjacent channel interference (much like assuring that 3rd and 5th order distortion products are down 35 dB or more in a standard transmitter). Loaded Q's in the 600 range can start to get your emissions into the BW required, but, you haven't done anything to work the skirts down yet (I'm assuming here that the spark-output is going to be somewhat broad in it's output BW spectrum). Loaded Q's more like 6000 look to be required once the steeper roll-off in the skirts is looked at. So, it's not really doable. You won't achieve the required passband at any US ham frequency (above 1.8 MHz) without going through those *enormous* efforts that you recognize as being a necessary - a tightening-up of your post-spark bandpass filter and this is without even addressing the filter's capability of achieve any appreciable power level as an output. RF Jim {Original Message removed}

How about a cavity resonator? ----- Original Message ----- From: Jim <spam_OUTjvpollTakeThisOuTDALLAS.NET> To: <.....PICLISTKILLspam@spam@MITVMA.MIT.EDU> Sent: Wednesday, September 11, 2002 8:46 PM Subject: Re: [EE]: Switching Higher Voltage---->Legal Spark Xmtr {Quote hidden}> > Of course you know that there are people who build and operate SG > > transmitters for fun in your country ? A SG transmitter can be made to > > meet FCC rules with a lot of filtering, so it can be done. > > Hmmmm ... *this* I would like to see. > > Your claim, roughly translated means that you are able, through > some miracle of post-spark gap filtering of reducing the bandwidth > of said sparkgap emissions to remain within allowable, legal > limits for currently legal emissions. > > That bandwidth being roughly six kiloHertz (although this *might* be > legal - you will make no friends on the bands as this is equal to > the emissions of a double-sideband AM transmission) *plus* you > will need somewhat steep-sided (rectanagular) skirts extending > outward from the +-3 kHz points in order to minimize adjacent > channel interference (much like assuring that 3rd and 5th > order distortion products are down 35 dB or more in a > standard transmitter). > > Loaded Q's in the 600 range can start to get your emissions into > the BW required, but, you haven't done anything to work the skirts > down yet (I'm assuming here that the spark-output is going to be > somewhat broad in it's output BW spectrum). Loaded Q's more > like 6000 look to be required once the steeper roll-off in > the skirts is looked at. > > So, it's not really doable. You won't achieve the required > passband at any US ham frequency (above 1.8 MHz) without > going through those *enormous* efforts that you recognize > as being a necessary - a tightening-up of your post-spark > bandpass filter and this is without even addressing the > filter's capability of achieve any appreciable power level > as an output. > > > RF Jim > > > > > ----- Original Message ----- > From: "Peter L. Peres" <plpKILLspamACTCOM.CO.IL> > To: <.....PICLISTKILLspam.....MITVMA.MIT.EDU> > Sent: Wednesday, September 11, 2002 2:09 PM > Subject: Re: [EE]: Switching Higher Voltage Sources with Power MOSFETS > > > > On Wed, 11 Sep 2002, Jim wrote: > > > > >Ya know - they used to do it that way - before > > >'spark' was banned! > > > > > >We have some old docs in the FCC collection of historic > > >regulations that address this - and truly, if anything > > >was 'chaotic' it was spark-excited tank (tuned LC) > > >circuits! > > > > > >Now we are coming full-circle, there are propositions > > >for WB (wide-band) RF transmissions for wide-band, > > >real-time 2-way data transfer in the microwave/millimeter > > >wave spectrum. > > > > > >Ever heard the saying: "What comes around - goes around." > > > > > >I used to take contention with that with 'the old guys'. > > >Now I am an 'old guy' and see the wisdom of that ... <BIG GRIN> > > > > Of course you know that there are people who build and operate SG > > transmitters for fun in your country ? A SG transmitter can be made to > > meet FCC rules with a lot of filtering, so it can be done. > > > > Peter > > > > -- > http://www.piclist.com hint: The PICList is archived three different > ways. See http://www.piclist.com/#archives for details. > > -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

On Wed, 11 Sep 2002, Jim wrote: >Your claim, roughly translated means that you are able, through >some miracle of post-spark gap filtering of reducing the bandwidth >of said sparkgap emissions to remain within allowable, legal >limits for currently legal emissions. http://www.qsl.net/g4rfr/marconi.htm 20kHz BW, went on air with special permission, with 15W, on 80m. The circuit speaks volumes. What would a normal transmitter use, three to five stages minimum pi output filter ? Try adding a similar ladder filter (not lowpass) to this transmitter and you'd likely be under 5kHz BW. I did not say it was efficient. He spanned 200 to 400 miles with his 15W. Here is a more detailed article on this: http://www.qsl.net/w9anl/newsltrs/0202/0202.htm If you want it hard enough, and if no basic laws are violated (or if you do not know that those laws exist ... ) then almost anything can be eventually achieved. Peter -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email EraseMElistservspam_OUTTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body

On Wed, 11 Sep 2002, Jim wrote: > > How about a cavity resonator? > >For 160 Meters (1.8 to 2.0 MHz)? > >Sure. Rent a grain silo! > >Now you have to rig up elements to 'excite' or couple >into and out of it (depending on the design)! Er, you know, it's not a grain silo but I heard of cases when small radio stations bougt a segment of disused high voltage line in rural areas and used it as tuned antenna. There were also stations that broadcast directly ON the hv lines (which were in use). I undestand that this was common in Russia (?) a long time ago. Peter -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email @spam@listservKILLspammitvma.mit.edu with SET PICList DIGEST in the body

Excerpts from Peter's previous post follow ">" symbol. > 20kHz BW, went on air with special permission, with 15W, on 80m. Like I said - can't meet even a WI-D-E 6 kHz BW slot the AM'ers occupy. Was that, uh, the uh ... 3dB BW? What did the spectrum look like at +-20 kHz? At +-50 kHz? (See also a previous [OT]: posting where I address this issue about BW regarding spark transmitters and the mechanism that creates such wide BWs.) > 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). RF Jim -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email RemoveMElistservTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body

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 -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

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 removed}