Mike I'm the fellow that is going to build up a Class C final using a 450TL. I would love to get a copy of that schematic for the 450TH rig in the Editors and Engineers handbook. I have a few of those, but apparently, not that one.
I have a very nice B&W 850A or 852 that I can use in this rig. Either should handle that tube fine, considering I'm not going to run much more than 2500 volts on it anyway. Maybe 3000. I just got the worled biggest honker daddy plate transformer from W5OMR. 8200V center tapped ( 4100 - 0 - 4100 ) at 4.5KVA !!! Yeah suh, takes 3 men and a dolly to move it!! This will be a fun project. 73's & batten down the hatches, here comes Rita.. W5SUM ---------- Original Message ----------- From: "Mike Dorworth,K4XM" <[EMAIL PROTECTED]> To: "Discussion of AM Radio" <amradio@mailman.qth.net> Sent: Wed, 21 Sep 2005 23:10:59 -0400 Subject: Re: [AMRadio] Pi-Net vs Link Couple > The Pi-Net will give a total of 50 db suppresion of harmonics. about > 20 in one spot and 30 in the other. Link couple can pass harmonics > to VHF by capacity coupling, hence the Faraday Shield Links used for > same later on. There is a nice single 450th Pi-Net rig shown in the > Editor and Engineers handbook. Also a couple of single ended ones in > the 1950 ARRL Handbook (for triodes). Some triodes that require > lots and lots or drive can unbalance the grid tank, which is > required for triodes using Pi-Net. Lo capacity tubes like the 450th > is OK. The old timers mostly used tuners (antenna) and open wire > feeders to keep the harmonics down. Hazletine link neutralization > can also be used and no split tanks are needed in or out. Remember > Class C , which is required for Hi level AM, is a extreme distortion > and harmonic generator so that some plan need to be in place to > handle the soup. Also a single band dipole is very frequency > selective and cuts way down on harmonics by itself. Multiband > dipoles, beams and multi dipole on one feeder and traps etc (G5RV) > are an open invitation to spread gook with only link output. Also > the guys that use CB lin years with no half wave filters get away in > mobile service without too many problems due to the narrow > frequency discrimination of mobile antennas. Hope this helps, 73 Mike > > ----- Original Message ----- > From: "Geoff" <[EMAIL PROTECTED]> > To: "Discussion of AM Radio" <amradio@mailman.qth.net> > Sent: Wednesday, September 21, 2005 10:45 PM > Subject: [AMRadio] Pi-Net vs Link Couple > > > SO, here we are, well past 1991 and the 'law' that went into effect > > saying that 1,500w PEP output is the maximum RF Power output that we > > hams can run, regarldless of mode. That doesn't deter the homebrewing > > spirit, but it does suggest that acheiving 1,500w PEP output is much > > easier than producing 1kW DC input to the final. With the mindset of > > still wanting to use the classic high-level plate modulation scheme, > > engineering a rig to use only one tube in the final (a 4-250, 250TH, > > 304TH/TL, 4-400, etc), modulated by a pair seems to make more common > > sense. That, and it's a bit more economic in filament requirements. > > > > I've heard recently that matching the output of the Class C > > pate-modulated final to the antenna is better, and more efficiently > > achieved by link coupling, vs Pi-Net. On the other hand, it's argued > > that Pi-Net coupling produces less RFI than link coupling does. > > > > So, which is better? > > > > Why? > > > > What are the effects of nuetralizing a single tube in a balanced tank > > circuit? If Pi-Net is to be used, does the final tube still need to be > > nuetralized? > > > > I know of a guy who wants to build a rig using a single 450TL in the > > final, modulated by a pair. He wants to pi-net the output, but I've > > heard that's a bad idea. > > > > I want to build a rig using a medium powered tride, perhaps a 250TH, > > modulated by a pair of 811's. Pi-Net, or Link Couple? > > > > I like seeing this kind of technical discussion on the list. I'm > > looking forward to all inputs. > > > > -- > > 73 = Best Regards, > > -Geoff/W5OMR > > > > ______________________________________________________________ > > AMRadio mailing list > > Home: http://mailman.qth.net/mailman/listinfo/amradio > > Help: http://mailman.qth.net/mmfaq.html > > Post: mailto:AMRadio@mailman.qth.net > > AMfone Website: http://www.amfone.net > > AM List Admin: Brian Sherrod/w5ami > > > > ______________________________________________________________ > AMRadio mailing list > Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:AMRadio@mailman.qth.net > AMfone Website: http://www.amfone.net > AM List Admin: Brian Sherrod/w5ami ------- End of Original Message -------
