Re: [AMRadio] Pi-Net vs Link Couple
I wonder though Don, while I've got your .. uhm 'ear' (eyes?) The link could use a little tuning to take a bit more load in the final. I've modified one of my 80m B&W HDVL plug-in coils and removed two turns on each side (4 turns, total), to raise the plate current a bit, because the Q is a bit sharp in that circuit. A breif excursion off-resonance, w/1.5kWDC on the plates, draws around 550mA. At Resonance (with 125mA of grid drive) the thing dips to around 200mA. That said, what value of series capacitance would you suggest/recommend to tune the link? In mine, I use a 4-turn link. On 80m I have about a 1000 pf air variable directly in series with the link, and I think about 300 pf is actually meshed in for resonance. On 160 I use a capacitive voltage divider formed by two fixed micas in series (about .002 each) with the 1000 pf variable bridged across one of them for fine tuning. The load is placed across one of the caps. I can get good coupling that way. When I tried a simple series cap on 160, I could hit resonance, but could only get about 10% coupling. On 40 I use the series cap, but it is almost completely unmeshed to hit resonance. I duplicated the setup for my other homebrew rig, and it works identically. 73, Don
Re: [AMRadio] Pi-Net vs Link Couple
- Original Message - From: "Mike Sawyer" <[EMAIL PROTECTED]> To: "Discussion of AM Radio" Sent: Thursday, September 22, 2005 5:17 PM Subject: Re: [AMRadio] Pi-Net vs Link Couple Doesn't the BC-610 accomplish this with the 250TH? Yes. Or might it be that it is utilizing half the coil. No. Mike(y) W3SLK - Original Message - From: "Brett gazdzinski" <[EMAIL PROTECTED]> To: "'Discussion of AM Radio'" Sent: Thursday, September 22, 2005 8:13 AM Subject: RE: [AMRadio] Pi-Net vs Link Couple I don't think there is any way to run a triode single ended with link coupled output, not in class C. I run a pair of 812A's (or 811A's, or V70D's) push pull link coupled output modulated by a pair of 811A's. It works very well. You can run them up to 2000 volts on the plates, or 1750, 0r 1500. I can get 400 watts carrier out pushing them, 350 watts out has the tubes showing no color. That is very close to the legal limit with plenty of audio. The 812/811 tubes are cheap, work from 1000 to 2000 volts, and don't take up a lot of space. I used small vacuum variable caps for neutralization, kilowatt coils, and a 6000 volt plate tuning cap. I got the small (2 to 30 pf @30,000 volts) neut caps out of old paging transmitters someone gave me, they ran a 4-400 at 3000 volts on 70? MHZ. Brett N2DTS -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Geoff Sent: Wednesday, September 21, 2005 10:46 PM To: Discussion of AM Radio 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 __ 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
Re: [AMRadio] Pi-Net vs Link Couple
Darrell, WA5VGO wrote: Triodes are great for grounded grid, but for class C, why fight neutralization? Use a power grid tube. Sure you need a screen supply, but consider the paybacks. No neutralization; at least on the lower frequencies, and low drive requirements. I realize modulating it is a little trickier, but I've never had the Eimac system of placing a reactor in the screen supply to fail to do the trick. Darrell, WA5VGO that's interesting, Darrell... a reactor in the screen supply. Are you capacitivly coupling it, as well? No, that can't be - the screens need to be DC voltage. However, the choke effectivly kills any stray capacitances... hm Great discussion, so far. Looking forward to more. Hope you guys are hunkered down for the hurricane. Kingwood, TX may be on the west side of the storm, but it's gonna be a big'un. -- 73 = Best Regards, -Geoff/W5OMR
Re: [AMRadio] Re:Balanced Line Antenna Tuner
Don: If you are talking about a "true" balanced antenna tuner, with link coupling and dual-differential output caps, and NO Baluns, you are not likely to achieve 160 through 10. I built a monster true-balanced tuner a few years ago for 160 through 40M. With the components required for the lower bands it will go no higher. You might get 80 through 10M. Tale a look at Cebik's website. He has a great deal of information on balanced antenna tuners. 73, Barrie, W7ALW - Original Message - From: "Donald R. R Moore" <[EMAIL PROTECTED]> To: Sent: Thursday, September 22, 2005 9:18 AM Subject: [AMRadio] Re:Balanced Line Antenna Tuner I want to construct a balanced line antenna tuner to cover 160-10 meters, does any one have any good ideas on one, and where a diagram can be obtained. Thanks, Don W5FFK On Thu, 22 Sep 2005 10:12:24 -0400 (EDT) [EMAIL PROTECTED] writes: Send AMRadio mailing list submissions to amradio@mailman.qth.net To subscribe or unsubscribe via the World Wide Web, visit http://mailman.qth.net/mailman/listinfo/amradio or, via email, send a message with subject or body 'help' to [EMAIL PROTECTED] You can reach the person managing the list at [EMAIL PROTECTED] When replying, please edit your Subject line so it is more specific than "Re: Contents of AMRadio digest..." Today's Topics: 1. Collins filter ([EMAIL PROTECTED]) 2. Re: Pi-Net vs Link Couple ([EMAIL PROTECTED]) 3. Re: Pi-Net vs Link Couple (ronnie.hull) 4. RE: Pi-Net vs Link Couple (Brett gazdzinski) 5. Re: Pi-Net vs Link Couple (Geoff) 6. Re: Pi-Net vs Link Couple ([EMAIL PROTECTED]) 7. Re: Pi-Net vs Link Couple (ronnie.hull) 8. Re: Pi-Net vs Link Couple (ronnie.hull) 9. Re: Pi-Net vs Link Couple (Geoff) 10. Re: Pi-Net vs Link Couple (Geoff) -- Message: 1 Date: Thu, 22 Sep 2005 04:19:26 EDT From: [EMAIL PROTECTED] Subject: [AMRadio] Collins filter To: amradio@mailman.qth.net Message-ID: <[EMAIL PROTECTED]> Content-Type: text/plain; charset="US-ASCII" I am looking for the 6.0khz filter..Pt # F-455-J60.. for the Collins 75A4 Reciever...Tnx Ron W6MAU -- Message: 2 Date: Thu, 22 Sep 2005 07:37:13 -0400 From: [EMAIL PROTECTED] Subject: Re: [AMRadio] Pi-Net vs Link Couple To: Discussion of AM Radio Message-ID: <[EMAIL PROTECTED]> Content-Type: text/plain; charset=US-ASCII On 21 Sep 2005 at 21:45, Geoff wrote: > 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. Where did you hear that? > On the other hand, it's argued > that Pi-Net coupling produces less RFI than link coupling does. > > So, which is better? Pi Network. > Why? I can only tell you from my own experiences, that a) You already answered the foirst part - less harmonics, and B) you get more power out. That is enough to persuade me. I know some folks swear by link coupling. I swear at it! I had an Eldico rig once with an 807 final. I could only get about 15 watts out with the link coupling. I re-confiugred it to be a pi network and immediately had no diifficulty getting about 35 watts out. Now some may argue that the link coupling circuit wasn't made right, wasn't adjust right etc. etc. I don't care about that. I just like pi networks. If it was good enough for Art Collins... -- Message: 3 Date: Thu, 22 Sep 2005 07:53:13 -0400 From: "ronnie.hull" <[EMAIL PROTECTED]> Subject: Re: [AMRadio] Pi-Net vs Link Couple To: "Mike Dorworth, K4XM" <[EMAIL PROTECTED]>,Discussion of AM Radio Message-ID: <[EMAIL PROTECTED]> Content-Type: text/plain; charset=iso-8859-1 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" 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 an
RE: [AMRadio] Pi-Net vs Link Couple
Triodes are great for grounded grid, but for class C, why fight neutralization? Use a power grid tube. Sure you need a screen supply, but consider the paybacks. No neutralization; at least on the lower frequencies, and low drive requirements. I realize modulating it is a little trickier, but I've never had the Eimac system of placing a reactor in the screen supply to fail to do the trick. Darrell, WA5VGO
Re: [AMRadio] Johnson 232-620
Mike: Where would one find the 232-620? 84 microhenry would be great! 73, Barrie, W7ALW - Original Message - From: "Mike Dorworth,K4XM" <[EMAIL PROTECTED]> To: "Discussion of AM Radio" Sent: Wednesday, September 21, 2005 8:48 PM Subject: [AMRadio] Johnson 232-620 Edgewise wound, 1/4" copper strip, cadmium plated, glass bonded mica supporting bars. Widely used commercially. Safely handles more that 1000 watts. 232-622 winding 8 5/16" Long, 4" ID. 84 Microhenry. __ 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
RE: [AMRadio] Pi-Net vs Link Couple - WD5JKO
Hi all, I have a different twist on this wonderful topic. Years ago I was going over the very issue, and I had a Viking I transmitter, and I wanted to run the legal limit of about 375 watts carrier 100% modulated am. So that would be 6 db to go from say 100 watts to 400 watts. I went through a lot of charts, curves, and calculator work, and I worked out a design. Of course I lost my notes, so this description is from memory. What I came up with was a parallel grounded grid linear using low mu 304TL's with a tuned filament choke input, and pi network output. Using grounded grid should reduce, or eliminate the need to neutralize, well at least from 160-40 meters that is. With no neutralizing circuitry, things get a lot simpler. A 3 band pi network on the output is doable, as is resonating the high current filament choke on multiple bands. So I was guessing a little on the gain, but 6 db was the target, and a low mu 304 TL is going to have low gain in G-G mode. Since class B RF linear amplifiers on AM get about 33% efficiency (no modulation), I figured 900 watts DC input would provide 300 watts RF output. A rough guess is the drive would be 100 watts from the Viking I, 25 of which would be lost to drive the 304TL's, and the remaining 75 would feed through to the output (normal characteristic for a G-G amplifier). So the output would be 300 + 75 = 375 watts. So in summary: exciter output 100 w 304TL drive power 25 w final dc input 900 w final amp % eff (un-mod) 33% feed through power from exciter 75 w rf output = (900 * .33) + 75 = 375 watts 304 TL Pd each tube = 300 watts So fellows, here is a big rig running AM legal power with big triodes, pi-net output, NO neutralizing circuit, with NO modulator, band switched, and driven by a Viking I or other 100 watt class AM rig. I never built the beast. Do you folks think this would work? Regards, Jim Candela WD5JKO -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.344 / Virus Database: 267.11.4/109 - Release Date: 9/21/2005
Re: [AMRadio] Pi-Net vs Link Couple
Byron Lichtenwalner wrote: Geoff Don't have the tube characteristics here, but from your description your changing the operating point of the amp by changing L/C ration. Or the "transformer effect" (turns ratio of link to plate coil) gives a better match to the antenna) http://w5omr.shacknet.nu:81/~w5omr/hamstuff/AM-Stuff/XMIT-Tube-Data/250TH.pdf -- 73 = Best Regards, -Geoff/W5OMR
Re: [AMRadio] Pi-Net vs Link Couple
Mike Sawyer wrote: Doesn't the BC-610 accomplish this with the 250TH? Or might it be that it is utilizing half the coil. Mike(y) W3SLK Yeah, it does, Mike. I didn't even think about that, and I recently downloaded a schematic in .gif format of a BC-610 E model. Not the best in the world, however it's like some guys describe their wife... 'better than nothing' ;-) http://w5omr.shacknet.nu:81/~w5omr/hamstuff/AM-Stuff/BC-610/bc610.gif -- 73 = Best Regards, -Geoff/W5OMR
Re: [AMRadio] Pi-Net vs Link Couple
Byron Lichtenwalner wrote: Geoff Don't have the tube characteristics here, but from your description your changing the operating point of the amp by changing L/C ration. Or the "transformer effect" (turns ratio of link to plate coil) gives a better match to the antenna) If you have a 1000 pf that will take the voltage, start there. If you loading to an untuned link, I bet you can load that thing like your using a bucket of bricks. That's the idea, Byron - to use a capacitor in series with the output of the link to the load (antenna). I my case, it's a relativly short run (10 ~ 15' of RG-8) to the input of a Heathkit 2060, which the open wire line output feeds 450 ohm ladder line, that feeds a full-wave delta loop on 75m. With the capacitor in series (someone else suggested an air variable broadcast tuning cap out of an old receiver) I can tune the link to load the final a bit heavier. 1000pF would probably be a good place to start. Thanks! -- 73 = Best Regards, -Geoff/W5OMR
Re: [AMRadio] Pi-Net vs Link Couple
Doesn't the BC-610 accomplish this with the 250TH? Or might it be that it is utilizing half the coil. Mike(y) W3SLK - Original Message - From: "Brett gazdzinski" <[EMAIL PROTECTED]> To: "'Discussion of AM Radio'" Sent: Thursday, September 22, 2005 8:13 AM Subject: RE: [AMRadio] Pi-Net vs Link Couple I don't think there is any way to run a triode single ended with link coupled output, not in class C. I run a pair of 812A's (or 811A's, or V70D's) push pull link coupled output modulated by a pair of 811A's. It works very well. You can run them up to 2000 volts on the plates, or 1750, 0r 1500. I can get 400 watts carrier out pushing them, 350 watts out has the tubes showing no color. That is very close to the legal limit with plenty of audio. The 812/811 tubes are cheap, work from 1000 to 2000 volts, and don't take up a lot of space. I used small vacuum variable caps for neutralization, kilowatt coils, and a 6000 volt plate tuning cap. I got the small (2 to 30 pf @30,000 volts) neut caps out of old paging transmitters someone gave me, they ran a 4-400 at 3000 volts on 70? MHZ. Brett N2DTS -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Geoff Sent: Wednesday, September 21, 2005 10:46 PM To: Discussion of AM Radio 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
Re: [AMRadio] Pi-Net vs Link Couple
Geoff Don't have the tube characteristics here, but from your description your changing the operating point of the amp by changing L/C ration. Or the "transformer effect" (turns ratio of link to plate coil) gives a better match to the antenna) If you have a 1000 pf that will take the voltage, start there. If you loading to an untuned link, I bet you can load that thing like your using a bucket of bricks. Byron, W3WKR - Original Message - From: "W5OMR/Geoff" <[EMAIL PROTECTED]> To: "Discussion of AM Radio" Sent: Thursday, September 22, 2005 5:59 PM Subject: Re: [AMRadio] Pi-Net vs Link Couple Byron Lichtenwalner wrote: Geoff Your last discussion on the L/C ratio of the tank intrigues me. Was the circuit not resonate with the extra (now removed) turns? On the link tuning, what series cap. value are you using? Does it load heavier when at max. cap or minimum? Byron, W3WKR It was resonant, but I wanted to draw a bit more current in the final. Not necessarily at the 4kV of DC that a 250TH can take, (4kV @ 250mA would be quite suffiecient, as long as I had enough drive to compensate for exceeding the plate dissapation by only running 45mA of grid drive per tube - for a pair, I'd need more like 150mA at that kind of current) but what I wanted, was around 1500v @ 350mA. I even started using a 40m coil (since it only had 2 turns less than the modified 80m coil) and added some capacitance from an added split-stator cap to resonate the final on 75m, but I find that the last 100 to 150mA of plate current does not result in an appreciable increase in power output. Yeah, I could get 400mA @ 1500v, but the output was only around 200w. Changing back to the previous coil, I can make around 350w of carrier input, but the plate current is only around 240~250mA. 1500v @ 300mA = 450w DC input and I'd like to keep the current up, while I reduce the voltage. It would also be around 5000 ohms of Z, vs a reduced current at higer voltage (say 1500 @ 100mA) is 15000 ohms. HUGE swing in impedance, which makes for a huge difference in audio. If I could get a starting figure on what size capacitor to use, I'd add one. I'd like to use a variable capacitor, but am unsure of the value range. 400 to 1000pf? Less? More? I'm asking... I don't know. -- 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
Re: [AMRadio] Pi-Net vs Link Couple
Byron Lichtenwalner wrote: Geoff Your last discussion on the L/C ratio of the tank intrigues me. Was the circuit not resonate with the extra (now removed) turns? On the link tuning, what series cap. value are you using? Does it load heavier when at max. cap or minimum? Byron, W3WKR It was resonant, but I wanted to draw a bit more current in the final. Not necessarily at the 4kV of DC that a 250TH can take, (4kV @ 250mA would be quite suffiecient, as long as I had enough drive to compensate for exceeding the plate dissapation by only running 45mA of grid drive per tube - for a pair, I'd need more like 150mA at that kind of current) but what I wanted, was around 1500v @ 350mA. I even started using a 40m coil (since it only had 2 turns less than the modified 80m coil) and added some capacitance from an added split-stator cap to resonate the final on 75m, but I find that the last 100 to 150mA of plate current does not result in an appreciable increase in power output. Yeah, I could get 400mA @ 1500v, but the output was only around 200w. Changing back to the previous coil, I can make around 350w of carrier input, but the plate current is only around 240~250mA. 1500v @ 300mA = 450w DC input and I'd like to keep the current up, while I reduce the voltage. It would also be around 5000 ohms of Z, vs a reduced current at higer voltage (say 1500 @ 100mA) is 15000 ohms. HUGE swing in impedance, which makes for a huge difference in audio. If I could get a starting figure on what size capacitor to use, I'd add one. I'd like to use a variable capacitor, but am unsure of the value range. 400 to 1000pf? Less? More? I'm asking... I don't know. -- 73 = Best Regards, -Geoff/W5OMR
Re: [AMRadio] Pi-Net vs Link Couple
Geoff Your last discussion on the L/C ratio of the tank intrigues me. Was the circuit not resonate with the extra (now removed) turns? On the link tuning, what series cap. value are you using? Does it load heavier when at max. cap or minimum? Byron, W3WKR - Original Message - From: "W5OMR/Geoff" <[EMAIL PROTECTED]> To: "Discussion of AM Radio" Sent: Thursday, September 22, 2005 5:14 PM Subject: Re: [AMRadio] Pi-Net vs Link Couple > I need to better proof-read my posts, before hitting the 'send' button.. > > W5OMR/Geoff wrote: > <>Donald Chester wrote: > > > What does 1500 watt pep have to do with it? > > > > Well... you know. I certainly don't want to Advertise ;-) > > > My Gates BC1-T uses a pair of 833A triodes in parallel, with a > > pi-network followed by a T network and another L netork, to couple the > > final to the antenna. The grid tank uses a tapped coil, with the tap > > grounded to produce the out of phase voltage. Both the adjustment of > > the tap and the neutralising cap will affect neutralisation. > > > > My rig is a pair of 250THs in the final, modulated by a pair. Like what > you prefer, the final has plug-in coils for the grid input tank, as well > as the final output tank. The problem I have with that rig however, is > that there seems to be some interaction between the grid circuit and the > final circuit, even though the plug-in grid coil and link are > 'underneath' the chassis, that the final coil and link sits on top of. > When the rig was built back in the mid 50's, most everything available > was steel, so that's what was used as a chassis. (there, that makes > more sense ;-)) > > A suggestion of physically raising the final coil further up to get out > of the field of the grid tank could be realized, if i wanted to give up > the front-panel control of the Faraday [-shielding-] sheilded link. As > a result, neutralization is as close as possible/ > > > The problem with grid neutralisation, sometimes called Rice > > neutralisation, is that it doesn't hold very well over a wide > > frequency range, especially if you attempt to switch over several > > amateur bands. My Gates stays neutralised over the 160m band from 1.8 > > to 2.0, but I never have tried to use it on any other band. > > > I've got plug-in coils for that rig, from 80m thru 10m, but I'm more > than a little leary of running a pair of 250TH's in Class C on 10m ;-) > > I wonder though Don, while I've got your .. uhm 'ear' (eyes?) The link > could use a little tuning to take a bit more heavier load in the final. > I've modified one of my 80m B&W HDVL plug-in coils and removed two > turns on each side (4 turns, total), to raise the plate current a bit, > because the Q is a bit sharp in that circuit. A breif excursion > off-resonance, w/1.5kWDC on the plates, draws around 550mA. At > Resonance (with 125mA of grid drive) the thing dips to around 200mA. > That said, what value of series capacitance would you suggest/recommend > to tune the link? > > > Plate neutralisation, using the same kind of tank circuit as a > > pushpull final, and single ended grid tank, works better over a wider > > freq range, because the plate-to-ground capacitance is usually much > > less than the grid-to-ground capacitance, and capacitance across one > > side of the tank circuit upsets the balance of the circuit. Also, > > grid loading effects cause some additional unbalance, even if the > > capacitance is perfectly balanced out with additional fixed > > capacitors. The pushpull circuit works best of all, since it is > > inherently a balanced bridge circuit, and theoretically works equally > > well over an extremely wide frequency range. Limitations lie in the > > precision of the balance of the split stator tank capacitors from > > minimum to maximum capacitance. > > > In my rig, the neutralizing caps come from the crossed grid-input lines, > and big silver disks mounted on screws on the back end of the B&W > bread-slicer butterfly tuning capacitor are what nulls out the > differences in capacitances in the two tubes. However, I know it is > possible to use a single tube in the final, like K5SWK's single 833, > modulated by a pair. I -think- Otis is using a big capacitor in place > of the 2nd tube and he's able to maintain a balanced tank circuit. I > had him on the phone earlier, but we didn't talk about rigs. > Looking forward to your reply and info. > > That should read better. > > -Geoff > > __ > 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
Re: [AMRadio] Pi-Net vs Link Couple
I need to better proof-read my posts, before hitting the 'send' button.. W5OMR/Geoff wrote: <>Donald Chester wrote: What does 1500 watt pep have to do with it? Well... you know. I certainly don't want to Advertise ;-) My Gates BC1-T uses a pair of 833A triodes in parallel, with a pi-network followed by a T network and another L netork, to couple the final to the antenna. The grid tank uses a tapped coil, with the tap grounded to produce the out of phase voltage. Both the adjustment of the tap and the neutralising cap will affect neutralisation. My rig is a pair of 250THs in the final, modulated by a pair. Like what you prefer, the final has plug-in coils for the grid input tank, as well as the final output tank. The problem I have with that rig however, is that there seems to be some interaction between the grid circuit and the final circuit, even though the plug-in grid coil and link are 'underneath' the chassis, that the final coil and link sits on top of. When the rig was built back in the mid 50's, most everything available was steel, so that's what was used as a chassis. (there, that makes more sense ;-)) A suggestion of physically raising the final coil further up to get out of the field of the grid tank could be realized, if i wanted to give up the front-panel control of the Faraday [-shielding-] sheilded link. As a result, neutralization is as close as possible/ The problem with grid neutralisation, sometimes called Rice neutralisation, is that it doesn't hold very well over a wide frequency range, especially if you attempt to switch over several amateur bands. My Gates stays neutralised over the 160m band from 1.8 to 2.0, but I never have tried to use it on any other band. I've got plug-in coils for that rig, from 80m thru 10m, but I'm more than a little leary of running a pair of 250TH's in Class C on 10m ;-) I wonder though Don, while I've got your .. uhm 'ear' (eyes?) The link could use a little tuning to take a bit more heavier load in the final. I've modified one of my 80m B&W HDVL plug-in coils and removed two turns on each side (4 turns, total), to raise the plate current a bit, because the Q is a bit sharp in that circuit. A breif excursion off-resonance, w/1.5kWDC on the plates, draws around 550mA. At Resonance (with 125mA of grid drive) the thing dips to around 200mA. That said, what value of series capacitance would you suggest/recommend to tune the link? Plate neutralisation, using the same kind of tank circuit as a pushpull final, and single ended grid tank, works better over a wider freq range, because the plate-to-ground capacitance is usually much less than the grid-to-ground capacitance, and capacitance across one side of the tank circuit upsets the balance of the circuit. Also, grid loading effects cause some additional unbalance, even if the capacitance is perfectly balanced out with additional fixed capacitors. The pushpull circuit works best of all, since it is inherently a balanced bridge circuit, and theoretically works equally well over an extremely wide frequency range. Limitations lie in the precision of the balance of the split stator tank capacitors from minimum to maximum capacitance. In my rig, the neutralizing caps come from the crossed grid-input lines, and big silver disks mounted on screws on the back end of the B&W bread-slicer butterfly tuning capacitor are what nulls out the differences in capacitances in the two tubes. However, I know it is possible to use a single tube in the final, like K5SWK's single 833, modulated by a pair. I -think- Otis is using a big capacitor in place of the 2nd tube and he's able to maintain a balanced tank circuit. I had him on the phone earlier, but we didn't talk about rigs. Looking forward to your reply and info. That should read better. -Geoff
Re: [AMRadio] Pi-Net vs Link Couple
Donald Chester wrote: What does 1500 watt pep have to do with it? Well... you know. I certainly don't want to Advertise ;-) My Gates BC1-T uses a pair of 833A triodes in parallel, with a pi-network followed by a T network and another L netork, to couple the final to the antenna. The grid tank uses a tapped coil, with the tap grounded to produce the out of phase voltage. Both the adjustment of the tap and the neutralising cap will affect neutralisation. My rig is a pair of 250THs in the final, modulated by a pair in the modulator. Like what you prefer, the final has plug-in coils for the grid input tank, as well as the final tank. The problem I have with that rig however, is that there seems to be some interaction between the grid circuit and the final circuit, even though the plug-in coil and link are 'underneath' the chassis, that the final coil sits on top of. When the rig was built back in the mid 50's, most everything available was steel. A suggestion of raising the final coil further up to get out of the field of the grid tank could be realized, if i wanted to give up the front-panel control of the Faraday shielding link. As a result, it's as close as possible, but probably not close enough. The problem with grid neutralisation, sometimes called Rice neutralisation, is that it doesn't hold very well over a wide frequency range, especially if you attempt to switch over several amateur bands. My Gates stays neutralised over the 160m band from 1.8 to 2.0, but I never have tried to use it on any other band. I've got plug-in coils for that rig, from 80m thru 10m, but I'm more than a little leary of running a pair of 250TH's in Class C on 10m ;-) I wonder though Don, while I've got your .. uhm 'ear' (eyes?) The link could use a little tuning to take a bit more load in the final. I've modified one of my 80m B&W HDVL plug-in coils and removed two turns on each side (4 turns, total), to raise the plate current a bit, because the Q is a bit sharp in that circuit. A breif excursion off-resonance, w/1.5kWDC on the plates, draws around 550mA. At Resonance (with 125mA of grid drive) the thing dips to around 200mA. That said, what value of series capacitance would you suggest/recommend to tune the link? Plate neutralisation, using the same kind of tank circuit as a pushpull final, and single ended grid tank, works better over a wider freq range, because the plate-to-ground capacitance is usually much less than the grid-to-ground capacitance, and capacitance across one side of the tank circuit upsets the balance of the circuit. Also, grid loading effects cause some additional unbalance, even if the capacitance is perfectly balanced out with additional fixed capacitors. The pushpull circuit works best of all, since it is inherently a balanced bridge circuit, and theoretically works equally well over an extremely wide frequency range. Limitations lie in the precision of the balance of the split stator tank capacitors from minimum to maximum capacitance. In my rig, the neutralizing caps come from the crossed grid-input lines, and big silver disks mounted on screws on the back end of the B&W bread-slicer butterfly tuning capacitor. Looking forward to your reply and info. -- 73 = Best Regards, -Geoff/W5OMR
RE: [AMRadio] Collins filter
I am looking for the 6.0khz filter..Pt # F-455-J60.. for the Collins 75A4 Reciever...Tnx Ron W6MAU Lots of luck. The trophy collectors have driven the price beyond what one used to pay for an entire 75A4. You can buy a reproduction filter, built around a modern Rockwell mechanical filter, with identical or better characteristics than the original one, for about $200. See the ad in Electric Radio. I bought one of those, and have an original 75A4 AM filter in my other receiver. To test them out I put both filters in the same receiver, and couldn't tell any difference whatever when I switched between them. Don k4kyv
RE: [AMRadio] Pi-Net vs Link Couple
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? What does 1500 watt pep have to do with it? If he wants to use pi network, he will have to use a balanced grid tank to produce the out-of-phase rf voltage necessary for neutralisation. A tube with as much grid-plate capacitance as the 450TL or 250TH must be neutralised for proper operation, unless it is grounded grid. Grounded grid is not recommended for plate modulated finals. My Gates BC1-T uses a pair of 833A triodes in parallel, with a pi-network followed by a T network and another L netork, to couple the final to the antenna. The grid tank uses a tapped coil, with the tap grounded to produce the out of phase voltage. Both the adjustment of the tap and the neutralising cap will affect neutralisation. The problem with grid neutralisation, sometimes called Rice neutralisation, is that it doesn't hold very well over a wide frequency range, especially if you attempt to switch over several amateur bands. My Gates stays neutralised over the 160m band from 1.8 to 2.0, but I never have tried to use it on any other band. Plate neutralisation, using the same kind of tank circuit as a pushpull final, and single ended grid tank, works better over a wider freq range, because the plate-to-ground capacitance is usually much less than the grid-to-ground capacitance, and capacitance across one side of the tank circuit upsets the balance of the circuit. Also, grid loading effects cause some additional unbalance, even if the capacitance is perfectly balanced out with additional fixed capacitors. The pushpull circuit works best of all, since it is inherently a balanced bridge circuit, and theoretically works equally well over an extremely wide frequency range. Limitations lie in the precision of the balance of the split stator tank capacitors from minimum to maximum capacitance. I have alway preferred the pushpull circuit with plug in coils and link coupling. It is more foolproof and works better. If everything is working properly, there should be negligible difference in the output power with either circuit. I have always used a link-coupled tuner into open line wire with mine, and have never received any harmonic complaints on any band. The biggest inconvenience is the necessity of changing coils to go from band to band. In any practical setup there are tradeoffs subject to the preferences of the operator. Don k4kyv
Re: [AMRadio] Re:Balanced Line Antenna Tuner
In a message dated 9/22/05 9:19:29 AM, [EMAIL PROTECTED] writes: > I want to construct a balanced line antenna tuner to cover 160-10 meters, > does any one have any good ideas on one, and where a diagram can be > obtained. > > A multitude of circuits and thousands of pages of description, theory and discussion can be found in the various published handbooks and antenna manuals (ARRL, Editors and Engineers, etc.) from the 1930s up to the present time. Dennis D. W7QHO Glendale, CA
Re: [AMRadio] Johnson 226-1
Johnson 226-3 Inductance 13.5 microHenry, 19.5 turns. Heavy duty rotary inductor for amateur and commercial use. Handle over a KW of modulated RF energy to 30 mHz. Winding 1/4" x 1/8" edgewise copper. Spring loaded beryllium copper contact. Variable pitch winding- wide frequency coverage. Height 6 1/2", width 4". Guaranteed to contain NO PCB's. Is it Y2K compliant? Don K4KYV
Re: [AMRadio] Pi-Net vs Link Couple
Hey Ronnie, YOU got the Boa Constrictor, OM! Why would you need it? Oh I get it - you want it for the DRIVER STAGE! He he he he he! On 22 Sep 2005 at 11:16, ronnie.hull wrote: > he don't need it Bry, let me have it LOL > > > > -- Original Message --- > From: Geoff <[EMAIL PROTECTED]> > To: Discussion of AM Radio > Sent: Thu, 22 Sep 2005 09:03:49 -0500 > Subject: Re: [AMRadio] Pi-Net vs Link Couple > > > ronnie.hull wrote: > > > > > <>well Bry, you gotta unnerstand, I'm next door to Texas, that makes me a > > > cousin.. and you know how they are in texas.. everything is bigger!!! > > > > > > R > > > > Bry, just on the Off-chance that I might make it to Florida, what > > are you asking for that 2500v @ 1amp xfmr? > > > > -- > > 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 > --- End of Original Message --- > > __ > 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 >
Re: [AMRadio] Pi-Net vs Link Couple
On 22 Sep 2005 at 9:03, Geoff wrote: > Bry, just on the Off-chance that I might make it to Florida, what are > you asking for that 2500v @ 1amp xfmr? > -Geoff/W5OMR Hi Geoff - I would let it go real reasonable - like $26.00 It's an older style upright transformer with a ceramic top. Kind of cool looking.
[AMRadio] Re:Balanced Line Antenna Tuner
I want to construct a balanced line antenna tuner to cover 160-10 meters, does any one have any good ideas on one, and where a diagram can be obtained. Thanks, Don W5FFK On Thu, 22 Sep 2005 10:12:24 -0400 (EDT) [EMAIL PROTECTED] writes: > Send AMRadio mailing list submissions to > amradio@mailman.qth.net > > To subscribe or unsubscribe via the World Wide Web, visit > http://mailman.qth.net/mailman/listinfo/amradio > or, via email, send a message with subject or body 'help' to > [EMAIL PROTECTED] > > You can reach the person managing the list at > [EMAIL PROTECTED] > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of AMRadio digest..." > > > Today's Topics: > >1. Collins filter ([EMAIL PROTECTED]) >2. Re: Pi-Net vs Link Couple ([EMAIL PROTECTED]) >3. Re: Pi-Net vs Link Couple (ronnie.hull) >4. RE: Pi-Net vs Link Couple (Brett gazdzinski) >5. Re: Pi-Net vs Link Couple (Geoff) >6. Re: Pi-Net vs Link Couple ([EMAIL PROTECTED]) >7. Re: Pi-Net vs Link Couple (ronnie.hull) >8. Re: Pi-Net vs Link Couple (ronnie.hull) >9. Re: Pi-Net vs Link Couple (Geoff) > 10. Re: Pi-Net vs Link Couple (Geoff) > > > -- > > Message: 1 > Date: Thu, 22 Sep 2005 04:19:26 EDT > From: [EMAIL PROTECTED] > Subject: [AMRadio] Collins filter > To: amradio@mailman.qth.net > Message-ID: <[EMAIL PROTECTED]> > Content-Type: text/plain; charset="US-ASCII" > > I am looking for the 6.0khz filter..Pt # F-455-J60.. for the > Collins 75A4 > Reciever...Tnx Ron W6MAU > > > -- > > Message: 2 > Date: Thu, 22 Sep 2005 07:37:13 -0400 > From: [EMAIL PROTECTED] > Subject: Re: [AMRadio] Pi-Net vs Link Couple > To: Discussion of AM Radio > Message-ID: <[EMAIL PROTECTED]> > Content-Type: text/plain; charset=US-ASCII > > On 21 Sep 2005 at 21:45, Geoff wrote: > > > 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. > > Where did you hear that? > > > On the other hand, it's argued > > that Pi-Net coupling produces less RFI than link coupling does. > > > > So, which is better? > > Pi Network. > > > Why? > > I can only tell you from my own experiences, that a) You already > answered the foirst part - less harmonics, and > B) you get more power out. > > That is enough to persuade me. > > I know some folks swear by link coupling. > I swear at it! > > I had an Eldico rig once with an 807 final. > I could only get about 15 watts out with the link coupling. > I re-confiugred it to be a pi network and immediately had > no diifficulty getting about 35 watts out. > > Now some may argue that the link coupling circuit wasn't > made right, wasn't adjust right etc. etc. I don't care about > that. I just like pi networks. If it was good enough for > Art Collins... > > > > > -- > > Message: 3 > Date: Thu, 22 Sep 2005 07:53:13 -0400 > From: "ronnie.hull" <[EMAIL PROTECTED]> > Subject: Re: [AMRadio] Pi-Net vs Link Couple > To: "Mike Dorworth, K4XM" <[EMAIL PROTECTED]>,Discussion of AM > Radio > > Message-ID: <[EMAIL PROTECTED]> > Content-Type: text/plain; charset=iso-8859-1 > > > 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" > 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)
Re: [AMRadio] Pi-Net vs Link Couple
he don't need it Bry, let me have it LOL -- Original Message --- From: Geoff <[EMAIL PROTECTED]> To: Discussion of AM Radio Sent: Thu, 22 Sep 2005 09:03:49 -0500 Subject: Re: [AMRadio] Pi-Net vs Link Couple > ronnie.hull wrote: > > > <>well Bry, you gotta unnerstand, I'm next door to Texas, that makes me a > > cousin.. and you know how they are in texas.. everything is bigger!!! > > > > R > > Bry, just on the Off-chance that I might make it to Florida, what > are you asking for that 2500v @ 1amp xfmr? > > -- > 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 --- End of Original Message ---
Re: [AMRadio] Pi-Net vs Link Couple
Ronnie, Hello! The 1 kilowatt Triode Pi-Network Amplifier using the 450TH is in the Editors and Engineers Handbook 14th Edition. The first of the handbooks edited by Bill Orr W6SAI. It has the RED cover. It starts on Page 585 in chapter 26-12 and ends on page 589. My scanner got knocked off the table by the dog and is broken. Been looking for replacement at CHEAP price. Perhaps some of the other fellows have this handy, if not, in a coupla weeks I should be able to get you a copy. 73, Mike - Original Message - From: "ronnie.hull" <[EMAIL PROTECTED]> To: "Mike Dorworth, K4XM" <[EMAIL PROTECTED]>; "Discussion of AM Radio" Sent: Thursday, September 22, 2005 7:53 AM Subject: Re: [AMRadio] Pi-Net vs Link Couple > > 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" > 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" > > 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 > > > > > > _
Re: [AMRadio] Pi-Net vs Link Couple
ronnie.hull wrote: <>well Bry, you gotta unnerstand, I'm next door to Texas, that makes me a cousin.. and you know how they are in texas.. everything is bigger!!! R Bry, just on the Off-chance that I might make it to Florida, what are you asking for that 2500v @ 1amp xfmr? -- 73 = Best Regards, -Geoff/W5OMR
Re: [AMRadio] Pi-Net vs Link Couple
ronnie.hull wrote: <>well it clearley shows on the top of the tranny 4100 - 0 - 4100.. I'll test it out this weekend and we'll know then. did you ever even put power to this transformer? R Yes, I did. Did it at John/WA5BXO's place.
Re: [AMRadio] Pi-Net vs Link Couple
well Bry, you gotta unnerstand, I'm next door to Texas, that makes me a cousin.. and you know how they are in texas.. everything is bigger!!! R -- Original Message --- From: [EMAIL PROTECTED] To: Discussion of AM Radio Sent: Thu, 22 Sep 2005 08:41:26 -0400 Subject: Re: [AMRadio] Pi-Net vs Link Couple > On 22 Sep 2005 at 7:22, Geoff wrote: > > > > I just got the worled biggest honker daddy plate transformer from W5OMR. > > > 8200V center tapped ( 4100 - 0 - 4100 ) at 4.5KVA !! > > > I think you're going to find, and we talked about this, that the > > transformer is 4100v across the entire secondary (@4.74kVA) > > Yeah but 8200 volts sounds so... electrifying! > > If anyone needs a smaller tranny, I have one that will do 2500 volts > at about 1 amp. > > Brian, AF4K > > __ > 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 ---
Re: [AMRadio] Pi-Net vs Link Couple
well it clearley shows on the top of the tranny 4100 - 0 - 4100.. I'll test it out this weekend and we'll know then. did you ever even put power to this transformer? R -- Original Message --- From: Geoff <[EMAIL PROTECTED]> To: Discussion of AM Radio Sent: Thu, 22 Sep 2005 07:22:16 -0500 Subject: Re: [AMRadio] Pi-Net vs Link Couple > ronnie.hull wrote: > > > <>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!! > > I think you're going to find, and we talked about this, that the > transformer is 4100v across the entire secondary (@4.74kVA) > > __ > 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 ---
Re: [AMRadio] Pi-Net vs Link Couple
On 22 Sep 2005 at 7:22, Geoff wrote: > > I just got the worled biggest honker daddy plate transformer from W5OMR. > > 8200V center tapped ( 4100 - 0 - 4100 ) at 4.5KVA !! > I think you're going to find, and we talked about this, that the > transformer is 4100v across the entire secondary (@4.74kVA) Yeah but 8200 volts sounds so... electrifying! If anyone needs a smaller tranny, I have one that will do 2500 volts at about 1 amp. Brian, AF4K
Re: [AMRadio] Pi-Net vs Link Couple
ronnie.hull wrote: <>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!! I think you're going to find, and we talked about this, that the transformer is 4100v across the entire secondary (@4.74kVA)
RE: [AMRadio] Pi-Net vs Link Couple
I don't think there is any way to run a triode single ended with link coupled output, not in class C. I run a pair of 812A's (or 811A's, or V70D's) push pull link coupled output modulated by a pair of 811A's. It works very well. You can run them up to 2000 volts on the plates, or 1750, 0r 1500. I can get 400 watts carrier out pushing them, 350 watts out has the tubes showing no color. That is very close to the legal limit with plenty of audio. The 812/811 tubes are cheap, work from 1000 to 2000 volts, and don't take up a lot of space. I used small vacuum variable caps for neutralization, kilowatt coils, and a 6000 volt plate tuning cap. I got the small (2 to 30 pf @30,000 volts) neut caps out of old paging transmitters someone gave me, they ran a 4-400 at 3000 volts on 70? MHZ. Brett N2DTS -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Geoff Sent: Wednesday, September 21, 2005 10:46 PM To: Discussion of AM Radio 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
Re: [AMRadio] Pi-Net vs Link Couple
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" 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" > 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 ---
Re: [AMRadio] Pi-Net vs Link Couple
On 21 Sep 2005 at 21:45, Geoff wrote: > 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. Where did you hear that? > On the other hand, it's argued > that Pi-Net coupling produces less RFI than link coupling does. > > So, which is better? Pi Network. > Why? I can only tell you from my own experiences, that a) You already answered the foirst part - less harmonics, and B) you get more power out. That is enough to persuade me. I know some folks swear by link coupling. I swear at it! I had an Eldico rig once with an 807 final. I could only get about 15 watts out with the link coupling. I re-confiugred it to be a pi network and immediately had no diifficulty getting about 35 watts out. Now some may argue that the link coupling circuit wasn't made right, wasn't adjust right etc. etc. I don't care about that. I just like pi networks. If it was good enough for Art Collins...
[AMRadio] Collins filter
I am looking for the 6.0khz filter..Pt # F-455-J60.. for the Collins 75A4 Reciever...Tnx Ron W6MAU
