Re: [AMRadio] AM Linear Operation
Mike, I have two Ameritron AL-1200's and one AL-1500. I like the AL-1200's better as they provide a good match for the 22-25 watt level driver. With 22 watts of carrier, the AL-1200 will put out 375 watts of carrier with 1500 watts PEP with a real nice scope pattern. The Al-1500 needs only about 10 watts of carrier to do the same job, but if during the course of a long transmission, should you overmodulate on some rare voice peak, the 1500 will kick off its overload circuit. Some may say this is a good thing. Since my amps are in the garage attached to the shack, I don't find it convienent to run out and reset the beast. The DX-60 will have too much drive for these amplifiers. I remember putting a dummy load on a T connector with one of my driver transmitters, but I don't remember how much lower the power was with this setup. Hope to hear you on AM in the future Mike. 73, Ken W2DTC Because I enjoy operating, and would like to do so with enough signal to be heard reasonably well on 80 and 40 meters, I too have been considering which linear to run on AM.
[AMRadio] AM Linear Operation
I've been reading this AM linear thread with great interest. I currently run a TS570 which gives me no more than 25 watts of carrier, plus a bit more on modulation peaks. I have an unmodified DX60 that I intend to put back in service later this summer after a shack painting project is finished. (No need to move it twice!) Because I enjoy operating, and would like to do so with enough signal to be heard reasonably well on 80 and 40 meters, I too have been considering which linear to run on AM. This discussion of linears on AM has caused me to reason that there is no exact magic combination of carrier drive level and audio level which is guaranteed to produce a cleanly amplified AM signal. For me, at least, this apparent fact is most unfortunate indeed. My signature will give you a hint of the usefulness of a scope in my shack. So, do I sit on my hands and wait for better propogation on the higher bands, or do I continue serving as the pin-drop test for all those restored 75A4's, HQ170's etc? Mike Duke, K5XU American Council of Blind Radio Amateurs
Re: [AMRadio] Amplifier to use with my DX-60
Don K4KYV said: "I hear a lot of guys on the air with AM linears, and most of the time they claim to be running way too much carrier for the tubes they are using. I often hear stuff like 200 watts out with a pair of 811A's or 250 watts out with a pair of 813's in g-g. If so, they are cooking the tubes, or else the efficiency is running too high, and they are flat-topping all over the place." I agree with your comments and yes, there is no doubt that those rigs are flat-topping. I've been running linear amps on AM for years and I find that the cleanest, best sounding signal comes from a linear with LOTS OF PLATE DISSIPATION and HEADROOM. In addition, an audio signal generator and an oscilloscope are mandatory to get clean results. Not everyone has this equipment and it is a hobby after all so folks do the best they can. As a rule of thumb I consider the plate dissipation divided by 3 to be a general yardstick for AM linears, some tubes giving a little more and some a little less. In the case of a pair of 3-500Z's I rate them in the 333-350 watt carrier class. So while a pair of 813's can be a wonderful plate modulated rig, as an AM linear they are not worth all the trouble of building them. It seems to me to be a waste of time to build an AM linear with much less than 1000 watts of plate dissipation. Of course if you have a low power rice box and already own some kind of linear, well go ahead, but if one is building an AM linear, more dissipation is better. 73, Ken W2DTC
RE: [AMRadio] Amplifier to use with my DX-60
I agree with that, it seems to me, lately, MANY people on the air are generating a lot of splatter. Often, the received signal looks ok (sometimes not), the audio sounds very good, but tune off frequency and they are generating artifacts way out. I see other people overmodulating, others with under 50% mod, people 2 kc off frequency, etc. On 40 meters, we often ran 5 Kc spacing, groups on 7295, 7290, 7285, and I did not hear the other guys with a 5.5Kc filter. Now, I often hear the people on 7285 on 7295. A lot of the people have been around a long time, so I am not sure what is up, extreme hifi not doing well through the transmitter? I myself cant even think about operating without the mod monitor and pep reading watt meter, its like driving at night without headlights! Brett N2DTS > Unfortunately, very few hams use scopes as modulation > monitors anymore. > They have become so unpopular that the major transceiver > manufacturers no > longer include monitor scopes in their equipment line, and > haven't done so > for years. I suppose the new breed of ham finds oscilloscope > patterns too > complicated to understand. No wonder there are so many > trashy signals on > the air. > > Don K4KYV > >
Re: [AMRadio] Modulator feedback
Jim, you have a dandy idea there. The plate supply for the drivers is kind of weird. When I was going through the transmitter I replaced most of the components in the modulator section as most were out of tolerance. Maybe I made a mistake, I'll sure check. Thankfully, the modulator deck can be accessed (by standing on your head!) without breaking down the entire transmitter. If that bias is off it could sure cause some strange happenings. Thanks a million, I'll follow your advise. Rick/K5IZ James M. Walker wrote: I'll bet you a nickel the bias supply has a problem, the plate supply for the 2A3s is not normal the plate supply is achieved by putting a negative voltage on the 2A3s cathode to raise hte plate to 360 volts. Sounds like the bias supply voltage is off. Check the manual and then the components that provide voltage to the 2A3s Jim WB2FCN YMMV
Re: [AMRadio] Modulator feedback
I'll bet you a nickel the bias supply has a problem, the plate supply for the 2A3s is not normal the plate supply is achieved by putting a negative voltage on the 2A3s cathode to raise hte plate to 360 volts. Sounds like the bias supply voltage is off. Check the manual and then the components that provide voltage to the 2A3s Jim WB2FCN YMMV - Original Message - From: "Rick Brashear" <[EMAIL PROTECTED]> To: "Discussion of AM Radio" Sent: Friday, March 17, 2006 6:10 PM Subject: Re: [AMRadio] Modulator feedback Thanks Mike. I just made a discovery about the 2A3 A-F drivers. I had a set of matched NOS RCA tubes in there. The feedback seemed to be coming from the area of those tubes more so than anywhere else. So, I exchanged them for another pair I have and it seemed to help quiet the feedback. Obviously, microphonics in the 2A3's is a factor. Next I looked for shields for the tubes, but have none, so I used a "poor man's shield", a couple of pieces of aluminum foil. It helped considerably! As a matter of fact, I could then advance the audio of the speech amp enough to achieve good modulation. So, I am now on a quest to find some way of shielding the 2A3's. I'm afraid my temporary foil shields would cause the tubes to over heat, plus it's not the best way of doing it. Have you had any experience with this? I wonder if the 100th's are also part of the problem. I really think the "talk back" is coming from the modulation transformer, which I can live with. I just have to get the feedback out of it. Thanks for your assistance and advice, Rick/K5IZ Mike Sawyer wrote: Rick, The UTC may work so don't discount it. Those I and H model transformers were only about half the size as the D and E models. I can't think of the company that made them but they were substantially different then the earlier models. As always, your mileage may vary. Mod-U-Lator, Mike(y) W3SLK __ 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, Paul Courson/wa3vjb
Re: [AMRadio] Amplifier to use with my DX-60
My main concern Don is that giving out a calculated carrier level for a set of tubes to a guy who does not have a scope and audio generator is not going to give the amateur band another clean signal. As I mentioned in a previous email, I have been unable to obtain the efficiencies you mention and would like to hear from someone who can measure everything with test equipment and tell me about it. I have never worked much with AM linears or low level modulation in my own station, but I have helped others set up their amplifiers. I do recall getting a SB-220 working with a FT-301, running a KW DC input and about 350 watts carrier out, with good modulation on the scope and little downward carrier shift in modulation. I also recall a Continental Electronics 250 watt broadcast transmitter used as a stand-by at a station where I once worked, which used a pair of 4-250's in the final, running a combination of screen and control grid modulation. It ran 250 watts output, with full 100% modulation, and the DC input was exactly 750 watts input. I recall back in the 60's, Walt WB4AOE running a pair of 833A's in class B linear service and getting 350 watts carrier output, until he acquired a modulation transformer to run plate modulation with another pair. I hear a lot of guys on the air with AM linears, and most of the time they claim to be running way too much carrier for the tubes they are using. I often hear stuff like 200 watts out with a pair of 811A's or 250 watts out with a pair of 813's in g-g. If so, they are cooking the tubes, or else the efficiency is running too high, and they are flat-topping all over the place. To me, that's the disadvantage of low level AM. You have to fiddle with it and get everything just exactly right: not too much grid drive, make sure you have heavy enough antenna loading, and keep the audio level at the right place. With plate modulation, the antenna loading and rf drive are not critical. Just tune everything to resonance, and make sure you are not overmodulating (and that the modulator is putting out clean audio), and as long as the tube is running reasonably close to recommended parameters, everything will be ok. Unfortunately, very few hams use scopes as modulation monitors anymore. They have become so unpopular that the major transceiver manufacturers no longer include monitor scopes in their equipment line, and haven't done so for years. I suppose the new breed of ham finds oscilloscope patterns too complicated to understand. No wonder there are so many trashy signals on the air. Don K4KYV ___ This message was typed using the DVORAK keyboard layout. Try it - you'll like it. http://www.mwbrooks.com/dvorak/ http://gigliwood.com/abcd/
Re: [AMRadio] Modulator feedback
Thanks Don. I used a 100 uf capacitor at 160 vdc, so it should be sufficient. I hooked it up exactly as you stated, positive to ground and the negative lead toward the center tap of the HV transformer. I wish I could say it stopped it, but I still have problems. It did stop a lot of the talk back, but the feed back is still there albeit not nearly as prevalent since I switched the 2A3 driver tubes. I made a couple of modifications to the dynamic microphone input to better accommodate the non amplified D-104, but I can't see how that would have anything to do with it. I can move the mic several feet away (it has a long cord - possibly too long) and turn the audio up enough to get 100% modulation on the scope. The 614 has a pretty high output and it takes little to overdrive the modulator. Rick/K5IZ Donald Chester wrote: How much capacitance did you use? It should be at least 20 mfd. A cheap electrolytic should do ok, since there is only a few volts across it. Put it between the midtap of the plate transformer and ground. The positive side should go to ground, and the negative side to the transformer. In all the BC-610E's I have ever seen, that capacitor eliminates 95% of the chatter. Don k4kyv ___ This message was typed using the DVORAK keyboard layout. Try it - you'll like it. http://www.mwbrooks.com/dvorak/ http://gigliwood.com/abcd/ __ 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, Paul Courson/wa3vjb
RE: [AMRadio] Modulator feedback
How much capacitance did you use? It should be at least 20 mfd. A cheap electrolytic should do ok, since there is only a few volts across it. Put it between the midtap of the plate transformer and ground. The positive side should go to ground, and the negative side to the transformer. In all the BC-610E's I have ever seen, that capacitor eliminates 95% of the chatter. Don k4kyv ___ This message was typed using the DVORAK keyboard layout. Try it - you'll like it. http://www.mwbrooks.com/dvorak/ http://gigliwood.com/abcd/
Re: [AMRadio] Modulator for DX60 available
John, I'll venture a bet that it was the versatile modulator that was in QST or the handbook from the fifties. That was a pretty common circuit and a JN could go ahead and buy a CW rig and just build the modulator to attach to it. I have one that Eric, WB4VVI (SK) built and gave me. I'm going to use it for either a modulator, or driver for a pair of 810's. Mod-U-Lator, Mike(y) W3SLK - Original Message - From: "John Lyles" <[EMAIL PROTECTED]> To: Sent: Friday, March 17, 2006 7:09 PM Subject: [AMRadio] Modulator for DX60 available I have a self contained, commercial looking modulator chassis that would work well with a DX60 sized rig. It uses a pair of 807s and has the input and output iron and driver tubes. It came from a SK's pile this summer. If there is interest, I would part with it to help out a DX60 conversion to high level plate modulation. Its a small thang. Technical details available upon request. 73 John K5PRO __ 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, Paul Courson/wa3vjb
RE: [AMRadio] AM transmitter coming available
WOW http://www.nrcdxas.org/articles/bta5t/ > Original Message > Subject: [AMRadio] AM transmitter coming available > From: "Robert A. Poff" <[EMAIL PROTECTED]> > Date: Fri, March 17, 2006 9:16 am > To: "AM Radio List Server" > > I'm in the process of getting approval to dispose of our good old RCA BTA-5T > transmitter. > Sad duty, since it's the rig I grew up listening toand I don't have the > room to take it.. > > This is a 5 KW/1KW AM transmitter in operating condition, currently on 910 > KC. > > Three phase power. > This one has been modified with ceramic tubes in the modulator (3CX3000's if > I remember correctly). > Essentially a drop-in change. > > The company would like to get $500 for the rig. > There is still a small chance they may want to part it out throughout the > company. > > But if they decide to dispose of it, you pick up in York, PA. > > Anyone interested? > > Robert A. Poff / WB3AWJ > Chief Engineer > WSBA / WARM-FM/ WSOX > Susquehanna Radio Corp. > > > __ > 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, Paul Courson/wa3vjb
RE: [AMRadio] AM transmitter coming available
Anything on the West Coast folks?! > Original Message > > I'm in the process of getting approval to dispose of our good old RCA BTA-5T > transmitter. > > But if they decide to dispose of it, you pick up in York, PA.
[AMRadio] Modulator for DX60 available
I have a self contained, commercial looking modulator chassis that would work well with a DX60 sized rig. It uses a pair of 807s and has the input and output iron and driver tubes. It came from a SK's pile this summer. If there is interest, I would part with it to help out a DX60 conversion to high level plate modulation. Its a small thang. Technical details available upon request. 73 John K5PRO
Re: [AMRadio] Modulator feedback
Thanks Mike. I just made a discovery about the 2A3 A-F drivers. I had a set of matched NOS RCA tubes in there. The feedback seemed to be coming from the area of those tubes more so than anywhere else. So, I exchanged them for another pair I have and it seemed to help quiet the feedback. Obviously, microphonics in the 2A3's is a factor. Next I looked for shields for the tubes, but have none, so I used a "poor man's shield", a couple of pieces of aluminum foil. It helped considerably! As a matter of fact, I could then advance the audio of the speech amp enough to achieve good modulation. So, I am now on a quest to find some way of shielding the 2A3's. I'm afraid my temporary foil shields would cause the tubes to over heat, plus it's not the best way of doing it. Have you had any experience with this? I wonder if the 100th's are also part of the problem. I really think the "talk back" is coming from the modulation transformer, which I can live with. I just have to get the feedback out of it. Thanks for your assistance and advice, Rick/K5IZ Mike Sawyer wrote: Rick, The UTC may work so don't discount it. Those I and H model transformers were only about half the size as the D and E models. I can't think of the company that made them but they were substantially different then the earlier models. As always, your mileage may vary. Mod-U-Lator, Mike(y) W3SLK
Re: [AMRadio] Modulator feedback
Thanks John, that's a good idea. Rick John E. Coleman (ARS WA5BXO) wrote: Get a high inductance choke (modulation reactor) to shunt the DC out of the secondary of the modulation XFMR. It will kill about 75 % of the talk back. What's left is all second harmonic talk back and it won't feed back. Did you ever use an old speaker that required DC to get the magnetism (no permanent magnet)? Not much sound comes out until the DC goes in to make the magnetism for the voice coil to work against. John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Rick Brashear Sent: Thursday, March 16, 2006 9:43 PM To: Discussion of AM Radio Subject: [AMRadio] Modulator feedback I've posed a couple of questions on some other lists and received some good advice, but I am still in need of more. My BC-610-E has a bad feedback or "talk back" problem. I've placed a capacitor across the overload relay (RY-5) and that did eliminate a little of the talk back. However, with much audio gain at all, not nearly enough to attain 100% modulation, I get feedback. Not just talk back, but feedback. I have to assume it's coming from the modulation transformer. The modulator bias is set for 40 ma as specifications state. The bolts on the modulation transformer are all tight. What am I over looking here? I'm using a BC-614-E speech amplifier with a D-104 non amplified mic. I did a few modifications to the dynamic input circuitry of the BC-614 to better match the D-104, but that is the only modification in either the speech amp or the BC-610-E. Rick/K5IZ __ 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, Paul Courson/wa3vjb __ 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, Paul Courson/wa3vjb
RE: [AMRadio] Modulator feedback
Get a high inductance choke (modulation reactor) to shunt the DC out of the secondary of the modulation XFMR. It will kill about 75 % of the talk back. What's left is all second harmonic talk back and it won't feed back. Did you ever use an old speaker that required DC to get the magnetism (no permanent magnet)? Not much sound comes out until the DC goes in to make the magnetism for the voice coil to work against. John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Rick Brashear Sent: Thursday, March 16, 2006 9:43 PM To: Discussion of AM Radio Subject: [AMRadio] Modulator feedback I've posed a couple of questions on some other lists and received some good advice, but I am still in need of more. My BC-610-E has a bad feedback or "talk back" problem. I've placed a capacitor across the overload relay (RY-5) and that did eliminate a little of the talk back. However, with much audio gain at all, not nearly enough to attain 100% modulation, I get feedback. Not just talk back, but feedback. I have to assume it's coming from the modulation transformer. The modulator bias is set for 40 ma as specifications state. The bolts on the modulation transformer are all tight. What am I over looking here? I'm using a BC-614-E speech amplifier with a D-104 non amplified mic. I did a few modifications to the dynamic input circuitry of the BC-614 to better match the D-104, but that is the only modification in either the speech amp or the BC-610-E. Rick/K5IZ __ 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, Paul Courson/wa3vjb
Re: [AMRadio] Modulator feedback
Rick, The UTC may work so don't discount it. Those I and H model transformers were only about half the size as the D and E models. I can't think of the company that made them but they were substantially different then the earlier models. As always, your mileage may vary. Mod-U-Lator, Mike(y) W3SLK - Original Message - From: "Rick Brashear" <[EMAIL PROTECTED]> To: "Discussion of AM Radio" Sent: Friday, March 17, 2006 4:25 PM Subject: Re: [AMRadio] Modulator feedback Wow! Not exactly the news I wanted, Mike, but thanks for the honesty. It looks like I may have to move the speech amp and mic considerably further away from the "E" model. I have an "H" and "I" model, but they are still in the refurb process. Potted modulation transformers or any modulation transformer for the 610 series is scarce. I have a UTC that will work, but it's not potted and I have an oil filled military transformer that would work if I had room on the chassis. I wonder what the guys in the SCR-399 did to contend with this issue since they were in such close quarters? Anyway, back to the drawing board and thanks again for the info. 73, Rick/K5IZ Mike Sawyer wrote: >Rick, >Unfortunately, you are plagued with the same problem dozens of -610 >owners have. The only way to resolve it is to get an I or H model >modulation >transformer. They are potted and hermetically sealed and don't talk back >near as much. Other than that you are SOL. >Mod-U-Lator, >Mike(y) >W3SLK >- Original Message - >From: "Rick Brashear" <[EMAIL PROTECTED]> >To: "Discussion of AM Radio" >Sent: Thursday, March 16, 2006 10:42 PM >Subject: [AMRadio] Modulator feedback > > >I've posed a couple of questions on some other lists and received some >good advice, but I am still in need of more. My BC-610-E has a bad >feedback or "talk back" problem. I've placed a capacitor across the >overload relay (RY-5) and that did eliminate a little of the talk back. >However, with much audio gain at all, not nearly enough to attain 100% >modulation, I get feedback. Not just talk back, but feedback. I have >to assume it's coming from the modulation transformer. The modulator >bias is set for 40 ma as specifications state. The bolts on the >modulation transformer are all tight. What am I over looking here? I'm >using a BC-614-E speech amplifier with a D-104 non amplified mic. I did >a few modifications to the dynamic input circuitry of the BC-614 to >better match the D-104, but that is the only modification in either the >speech amp or the BC-610-E. > >Rick/K5IZ > > >__ >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, Paul Courson/wa3vjb > >__ >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, Paul Courson/wa3vjb > > > __ 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, Paul Courson/wa3vjb
Re: [AMRadio] Amplifier to use with my DX-60
If I use a modulator to do plate modulation with the DX-60 what considerations are there regarding connection the plate circuit in respects to RF shielding, etc from the modulator circuit? Tom K3TVC - Original Message - From: "Harry Vaught" <[EMAIL PROTECTED]> Cc: "'Discussion of AM Radio'" Sent: Friday, March 17, 2006 2:56 PM Subject: Re: [AMRadio] Amplifier to use with my DX-60 > Thanks to those who replied to my question about plate modulating my > DX-60. Amazingly, the conversions sound practical. > > I was expecting posts which started, "First, obtain some unobtainium...". > > Thanks, guys. > > Harry, KT4AE > Maryville, Tennessee > __ > 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, Paul Courson/wa3vjb >
Re: [AMRadio] Valiant modulation eedback
Thanks John. I hadn't thought of isolating the xfmr from the chassis. I do that with near fields in the studio all the time to get a flatter response. You may be on to something big here, thanks! Regards, Rick/K5IZ John Lawson wrote: Re: the discussion of acoustic/mechanical modulator feedback - my Valiant 'talks' - and loudly - when I'm hitting it good. I have a broadcast mike, preamp, EQ and compressor in my audio chain - all fed into the (as yet unmodified) Valiant input. (BTW, my buddy's Johnson 500 'talks' loud enough to heard in the next room - he also has to watch his mike placement.) Of course, when On The Air - the Valiant rings and howls - I have to move the mike, change the locations of various things - and quite likely put the Valiant on an acoustic absorbing pad of some kind. Lead-filled 1/2" neoprene comes to mind - I've used that building theatres and recording studios - it's amazing what it sucks up. Another thought re: 'potted' vs. 'open frame' Mod Iron occurs to me (still with acoustic-designer hat on)... isolating the offending transformer from the chassis might mitigate some of these feedback effects - maybe as easy as removing the mounting bolts and resting the device on hi-temp dense foam or even thick felt padding - something to break the close mechanical coupling between the transformer core and the chassis of tghe rig. Maybe easier than re-doing the modulator, or even exiling tghe poor thing... I've done exactly this with building distro transformers of up to 100KVA - and in fact there are several commercially-available solutions for just this kind of thing... hit the Big Breaker and half that end of the building goes hu... ;} Cheers John KB6SCO __ 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, Paul Courson/wa3vjb
[AMRadio] Valiant modulation eedback
Re: the discussion of acoustic/mechanical modulator feedback - my Valiant 'talks' - and loudly - when I'm hitting it good. I have a broadcast mike, preamp, EQ and compressor in my audio chain - all fed into the (as yet unmodified) Valiant input. (BTW, my buddy's Johnson 500 'talks' loud enough to heard in the next room - he also has to watch his mike placement.) Of course, when On The Air - the Valiant rings and howls - I have to move the mike, change the locations of various things - and quite likely put the Valiant on an acoustic absorbing pad of some kind. Lead-filled 1/2" neoprene comes to mind - I've used that building theatres and recording studios - it's amazing what it sucks up. Another thought re: 'potted' vs. 'open frame' Mod Iron occurs to me (still with acoustic-designer hat on)... isolating the offending transformer from the chassis might mitigate some of these feedback effects - maybe as easy as removing the mounting bolts and resting the device on hi-temp dense foam or even thick felt padding - something to break the close mechanical coupling between the transformer core and the chassis of tghe rig. Maybe easier than re-doing the modulator, or even exiling tghe poor thing... I've done exactly this with building distro transformers of up to 100KVA - and in fact there are several commercially-available solutions for just this kind of thing... hit the Big Breaker and half that end of the building goes hu... ;} Cheers John KB6SCO
Re: [AMRadio] Modulator feedback
Wow! Not exactly the news I wanted, Mike, but thanks for the honesty. It looks like I may have to move the speech amp and mic considerably further away from the "E" model. I have an "H" and "I" model, but they are still in the refurb process. Potted modulation transformers or any modulation transformer for the 610 series is scarce. I have a UTC that will work, but it's not potted and I have an oil filled military transformer that would work if I had room on the chassis. I wonder what the guys in the SCR-399 did to contend with this issue since they were in such close quarters? Anyway, back to the drawing board and thanks again for the info. 73, Rick/K5IZ Mike Sawyer wrote: Rick, Unfortunately, you are plagued with the same problem dozens of -610 owners have. The only way to resolve it is to get an I or H model modulation transformer. They are potted and hermetically sealed and don't talk back near as much. Other than that you are SOL. Mod-U-Lator, Mike(y) W3SLK - Original Message - From: "Rick Brashear" <[EMAIL PROTECTED]> To: "Discussion of AM Radio" Sent: Thursday, March 16, 2006 10:42 PM Subject: [AMRadio] Modulator feedback I've posed a couple of questions on some other lists and received some good advice, but I am still in need of more. My BC-610-E has a bad feedback or "talk back" problem. I've placed a capacitor across the overload relay (RY-5) and that did eliminate a little of the talk back. However, with much audio gain at all, not nearly enough to attain 100% modulation, I get feedback. Not just talk back, but feedback. I have to assume it's coming from the modulation transformer. The modulator bias is set for 40 ma as specifications state. The bolts on the modulation transformer are all tight. What am I over looking here? I'm using a BC-614-E speech amplifier with a D-104 non amplified mic. I did a few modifications to the dynamic input circuitry of the BC-614 to better match the D-104, but that is the only modification in either the speech amp or the BC-610-E. Rick/K5IZ __ 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, Paul Courson/wa3vjb __ 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, Paul Courson/wa3vjb
Re: [AMRadio] Modulator feedback
Rick, Unfortunately, you are plagued with the same problem dozens of -610 owners have. The only way to resolve it is to get an I or H model modulation transformer. They are potted and hermetically sealed and don't talk back near as much. Other than that you are SOL. Mod-U-Lator, Mike(y) W3SLK - Original Message - From: "Rick Brashear" <[EMAIL PROTECTED]> To: "Discussion of AM Radio" Sent: Thursday, March 16, 2006 10:42 PM Subject: [AMRadio] Modulator feedback I've posed a couple of questions on some other lists and received some good advice, but I am still in need of more. My BC-610-E has a bad feedback or "talk back" problem. I've placed a capacitor across the overload relay (RY-5) and that did eliminate a little of the talk back. However, with much audio gain at all, not nearly enough to attain 100% modulation, I get feedback. Not just talk back, but feedback. I have to assume it's coming from the modulation transformer. The modulator bias is set for 40 ma as specifications state. The bolts on the modulation transformer are all tight. What am I over looking here? I'm using a BC-614-E speech amplifier with a D-104 non amplified mic. I did a few modifications to the dynamic input circuitry of the BC-614 to better match the D-104, but that is the only modification in either the speech amp or the BC-610-E. Rick/K5IZ __ 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, Paul Courson/wa3vjb
Re: [AMRadio] Amplifier to use with my DX-60
About $100 each new I believe My Centurion has 2 of them and they have lasted over 5 years now. 375 watts of carrier is easy on them. - Original Message - From: "John E. Coleman (ARS WA5BXO)" <[EMAIL PROTECTED]> To: "'Discussion of AM Radio'" Sent: Friday, March 17, 2006 10:28 AM Subject: RE: [AMRadio] Amplifier to use with my DX-60 Yep, there is no doubt that the pair of 3-500Zs and getting rid of the control carrier on the DX60 would be better but a lot more expense I think. Aren't 3-500Zs pretty expensive? John -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Jim candela Sent: Friday, March 17, 2006 10:00 AM To: Discussion of AM Radio Subject: RE: [AMRadio] Amplifier to use with my DX-60 John, Your approach as always is a good one, and can be made to work out quite well. This extra box will allow about a 6DB increase in power from what a screen modulated 6146 can do. The DX-60 with carrier control can arguably better match up to a linear amplifier, but must of us would agree that carrier control as done on this rig is too much, and annoying to those copying a weak signal that goes into and out of the noise with modulation peaks. Now consider these options: 1.) Modify the DX-60 for non carrier control screen modulation. That should provide about 20 watts carrier with room for + 100% modulation. 2.) Modify the DX-60 for plate modulation. This might require a 6146 bias change for proper class C plate modulation bias. You will also have to deal with modulating the screen grid. The plate tuning capacitor might flash over, and other components may need to be beefed up to handle the higher peak power. Once done, you will have a fine 45-50 watt AM rig that you could be proud of. 3.) Combine option 1 with this: Mate up the modified DX-60 to a linear with 1000 watts of dissipation available (like two 3-500Z's). Now you can easily run 250 watts AM or more (maybe 375) of quality AM. 4.) Use the DX-60 as is (stock), or with an amplifier as you wish. The choice is yours, Jim WD5JKO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of John E. Coleman (ARS WA5BXO) Sent: Thursday, March 16, 2006 9:10 PM To: 'Discussion of AM Radio' Subject: RE: [AMRadio] Amplifier to use with my DX-60 I still say, forget the linear, and use less money to build a plate modulator for the DX60. It will work better, sound better, cost less, and heat the shack up less. As I recall the DX 60 has a 6146 in the final for class C CW and puts out about 40-50 watts of carrier if it were plate modulated it would do at least 200 watts PEP and sound great. There is a number of different ways to do the modulator. A lot of guys just find and old PA and a transformer to match to the final. Some build the modulator output stages only, input XFMR tubes and modulation XFMR. Then they drive it with a small microphone amp. That's more stuff to set around on the desk but it works. There are a lot of self contained 25 and 50 watt modulator circuits around and probably a lot of complete one piece store bought modulators as well. As I recall, EICO had a pretty nice one that was to go with the EICO model 720 but it was used on many different rigs as well as being used as a driver for big modulators. A buddy of mine had an ECIO 720 and built a nice home brewed modulator for it using 1625s in AB1. It sounded real good. I built one similar to it with less power output for my Knight Kit T60. The T60 had the same control carrier AM that the DX60 does. What a difference it made when it was plate modulated. Very little modification is necessary in the DX60 to accommodate the external modulator. John, WA5BXO __ 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, Paul Courson/wa3vjb -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.1.385 / Virus Database: 268.2.4/283 - Release Date: 3/16/2006 -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.1.385 / Virus Database: 268.2.4/283 - Release Date: 3/16/2006 __ 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, Paul Courson/wa3vjb __ 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, Paul Courson/wa3vjb
RE: [AMRadio] Amplifier to use with my DX-60
Jim, I suppose it is also preference. BJ and I modified the Kenwood TS820 to full double sideband and it runs about 10-20 watts carrier output in that mode we drive and SB200 modified with a switch to kick in extra bias when we use in on AM. It puts out about 75-80 watts carrier with good modulation characteristics. So the combo is equivalent to a DX100 with maybe better audio. John -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Jim candela Sent: Friday, March 17, 2006 1:48 PM To: Discussion of AM Radio Subject: RE: [AMRadio] Amplifier to use with my DX-60 John, Yep 3-500z's are expensive. That said, I've seen "working" Heath SB-220's for sale around $300.00. Also many of us in this group already have a nice linear already as part of their SSB station. If it is already there, use it on AM! Cheers, Jim
Re: [AMRadio] Amplifier to use with my DX-60
On Fri, 17 Mar 2006, Harry Vaught wrote: I was expecting posts which started, "First, obtain some unobtainium...". Then of course it would have been "Oh - that's on eBay right now, Item Number XX. RARE L@@K VINTAGE UNOBTANIUM Never Opened - With Hard-to-Find Original Label" Cheers John KB6SCO
Re: [AMRadio] Amplifier to use with my DX-60
Thanks to those who replied to my question about plate modulating my DX-60. Amazingly, the conversions sound practical. I was expecting posts which started, "First, obtain some unobtainium...". Thanks, guys. Harry, KT4AE Maryville, Tennessee
RE: [AMRadio] Amplifier to use with my DX-60
John, Yep 3-500z's are expensive. That said, I've seen "working" Heath SB-220's for sale around $300.00. Also many of us in this group already have a nice linear already as part of their SSB station. If it is already there, use it on AM! Cheers, Jim -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of John E. Coleman (ARS WA5BXO) Sent: Friday, March 17, 2006 10:29 AM To: 'Discussion of AM Radio' Subject: RE: [AMRadio] Amplifier to use with my DX-60 Yep, there is no doubt that the pair of 3-500Zs and getting rid of the control carrier on the DX60 would be better but a lot more expense I think. Aren't 3-500Zs pretty expensive? John -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Jim candela Sent: Friday, March 17, 2006 10:00 AM To: Discussion of AM Radio Subject: RE: [AMRadio] Amplifier to use with my DX-60 John, Your approach as always is a good one, and can be made to work out quite well. This extra box will allow about a 6DB increase in power from what a screen modulated 6146 can do. The DX-60 with carrier control can arguably better match up to a linear amplifier, but must of us would agree that carrier control as done on this rig is too much, and annoying to those copying a weak signal that goes into and out of the noise with modulation peaks. Now consider these options: 1.) Modify the DX-60 for non carrier control screen modulation. That should provide about 20 watts carrier with room for + 100% modulation. 2.) Modify the DX-60 for plate modulation. This might require a 6146 bias change for proper class C plate modulation bias. You will also have to deal with modulating the screen grid. The plate tuning capacitor might flash over, and other components may need to be beefed up to handle the higher peak power. Once done, you will have a fine 45-50 watt AM rig that you could be proud of. 3.) Combine option 1 with this: Mate up the modified DX-60 to a linear with 1000 watts of dissipation available (like two 3-500Z's). Now you can easily run 250 watts AM or more (maybe 375) of quality AM. 4.) Use the DX-60 as is (stock), or with an amplifier as you wish. The choice is yours, Jim WD5JKO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of John E. Coleman (ARS WA5BXO) Sent: Thursday, March 16, 2006 9:10 PM To: 'Discussion of AM Radio' Subject: RE: [AMRadio] Amplifier to use with my DX-60 I still say, forget the linear, and use less money to build a plate modulator for the DX60. It will work better, sound better, cost less, and heat the shack up less. As I recall the DX 60 has a 6146 in the final for class C CW and puts out about 40-50 watts of carrier if it were plate modulated it would do at least 200 watts PEP and sound great. There is a number of different ways to do the modulator. A lot of guys just find and old PA and a transformer to match to the final. Some build the modulator output stages only, input XFMR tubes and modulation XFMR. Then they drive it with a small microphone amp. That's more stuff to set around on the desk but it works. There are a lot of self contained 25 and 50 watt modulator circuits around and probably a lot of complete one piece store bought modulators as well. As I recall, EICO had a pretty nice one that was to go with the EICO model 720 but it was used on many different rigs as well as being used as a driver for big modulators. A buddy of mine had an ECIO 720 and built a nice home brewed modulator for it using 1625s in AB1. It sounded real good. I built one similar to it with less power output for my Knight Kit T60. The T60 had the same control carrier AM that the DX60 does. What a difference it made when it was plate modulated. Very little modification is necessary in the DX60 to accommodate the external modulator. John, WA5BXO __ 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, Paul Courson/wa3vjb -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.1.385 / Virus Database: 268.2.4/283 - Release Date: 3/16/2006 -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.1.385 / Virus Database: 268.2.4/283 - Release Date: 3/16/2006 __ 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, Paul Courson/wa3vjb __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: ma
RE: [AMRadio] Amplifier to use with my DX-60
Ken, The answer to your question is YES, But. The but comes from the fact that linear amplifiers need to be monitored with a scope looking for proper linearity, more so than plate modulation. I use the trapezoid pattern, and I always tune for max as you describe, and then when cutting back the drive to about 25%, I modulate while looking at the trapezoid. Almost always I have to adjust the linear loading control for a linear ramp as I approach 100% modulation. So with a linear you need the scope, and trapezoid pattern selection to get things correct, and then set the audio level. With plate modulation you only set the audio level. So what percentage of this group uses a scope on AM? So what percentage of the scope users utilize the Trapezoid pattern? Remember for the Trapezoid you use scope in X:Y mode where the audio at scope suitable level (about 10 volts peak) goes into the horizontal channel, and the RF into the vertical channel. Regards, Jim I have been called a square before, but never a trapezoid! -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of kenw2dtc Sent: Thursday, March 16, 2006 7:25 PM To: Discussion of AM Radio Subject: Re: [AMRadio] Amplifier to use with my DX-60 Jim, I guess my question is really: Can anyone actually demonstrate a real AM linear that can output 500 watts carrier and show 2000 watts PEP into a dummy load with a nice looking audio sine wave on the scope, from the RF pickup, while running 1500 watts DC input ? If so, please send me an email at [EMAIL PROTECTED] The reason I ask is: A. None of my amps has ever been that good and B. Unfortunately, a number of people running AM linears do not have scopes and if you tell them that a pair of whatever tubes can achieve a certain carrier power, they will put the carrier to that level via dipping and peaking the pi-net until their wattmeter reaches the specified power and talk. In my experience, by the time you heavily load the output to achieve the perfect audio sine wave, your tuning controls are quite different than what is was when you peaked everything and the efficiency is no longer as good as what the calculations show. On top of that most male voices have peaks that should have an additional de-rating of output power. So when someone asks about what kind of carrier power a certain pair of tubes can put out in AM linear service, I really like to give a conservative number, not the math numbers. 73, Ken W2DTC __ Ken Barber Middletown, NJ Radio Website: http://w2dtc.com Family Photos: http://kenw2dtc.home.comcast.net __ - Original Message - From: "Jim candela" <[EMAIL PROTECTED]> To: "Discussion of AM Radio" Sent: Thursday, March 16, 2006 7:22 PM Subject: RE: [AMRadio] Amplifier to use with my DX-60 > > Don, > > You said: "So you could run maximum 1500 watts DC input to those tubes, > with 500 watts > carrier output, and 1000 watts dissipated by the tubes". > > Reply from Jim WD5JKO: > > What is stated above is correct if the tubes can dissipate 1000 watts of > heat (like two 3-500Z's flat out blushing), and the drive is adjusted to > about 1/4th that for maximum PEP output. In this case the efficiency is > assummed to be about 33%, so 1500 X .333 = 500 watts. The efficiency may > vary some, and is usually lower then that, so the 33% assumption is only a > first guess. It could be 25%, and that really upsets the situation making > the linear more of a heater, and less of a transmitter. > > One good thing about the 1500 watt PEP output power rule we all complain > about is that efficiency doesn't matter as much now. You can legally run a > 15 KW PEP input amplifier with 10% efficiency to provide 1500 watts PEP > output. It wouldn't make a lot of sense, or be practical, but it's now > legal. Back in the 1000 watts DC input days things were a lot different, > and > the SB-220's input would likely exceed 1000 watts DC before the AM carrier > got to 375 like we often do today with these amps. The point here is that > for low efficiency linears, or grid modulated amplifiers, we can > sometimes > run more power today on AM then before the rules changed from 1000 watts > DC > input to 1500 watts PEP output. Of course this isn't the case with plate > modulation where an output PEP at or maybe more than 3KW PEP WAS possible, > and completely legal. > > Regards, > Jim > WD5JKO > > > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Behalf Of kenw2dtc > Sent: Thursday, March 16, 2006 4:21 PM > To: Discussion of AM Radio > Subject: Re: [AMRadio] Amplifier to use with my DX-60 > > > Don says: > > "So you could run maximum 1500 watts DC input to those tubes, with 500 > watts > carrier output, and 1000 watts dissipated by the tubes" > > ***I need a little help with the math here Don. You are suggesting > that > with a class B linear in AM mode, one can
RE: [AMRadio] Amplifier to use with my DX-60
Well first of all Harry I am not familiar with the Webster Electric PA amp but 25 watts output is a little on the light side but is usable if you don't load the DX60 to more than 40-50 watts plate input power. You could probably use a 25 watt audio output XFMR rated of single ended use, so it would handle the DC from the final. I have used a 200 watt power XFMR from old television sets as a modulation XFMR. Use the HV Secondary as the final side (experiment as to whether using all of the secondary or one half) and input from the PA (16 ohm to 12V) or (500 ohm to 110V). Experimentation might be necessary. Basically, if the 6146 rig is 500V and 100ma it would require 25 watts at 353 V RMS (0.707 X 500) to modulate it. Find the transformation windings that give you the closest match to get this voltage output. Your 25 watt amp is capable of putting out 20 volts RMS into 16 ohms or about 14 volts into 8 ohms or 112 volts for 500 ohm line. If you had more audio power available then your options would be more. If the power XFMR is about 360 volts either side of CT then use CT to one one side (half of the secondary) for the plate circuit and input 500 ohms to the 115 Volt AC of the primary. You will use the DX 60 in the CW mode and connect the HV secondary of the outboard matching XFMR so that the B+ for the final and the screen resistor connection point are together and their current has to pass thru the XFMR to work. Check with other diagrams of 6146 plate modulated rigs in the older handbooks and you will get the idea. Good Luck John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Harry Vaught Sent: Friday, March 17, 2006 7:13 AM To: Discussion of AM Radio Subject: Re: [AMRadio] Amplifier to use with my DX-60 Ok, tell me this: I have a DX-60A and a 25 watt P-P 6L6 Webster Electric PA amp with a large selection of output impedances. What would I have to do to plate modulate my DX-60? There are obviously greatly varying levels of knowledge out there, and mine is probably below median. Harry, KT4AE Maryville, Tennessee __ 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, Paul Courson/wa3vjb
Re: [AMRadio] Amplifier to use with my DX-60
Get a large old TV power transformer. Use the high voltage to feed the 6146 and the 115 volt winding or filament windings to match to the amplifier output. You can use a 4500 ohm resistor of 20 watts across the highvoltage winding and look at it with a scope. Select the winding on the TV xfmr and the amp output tap that gives the best waveform with a 2 tone or 1000kc signal thru the amp. Other wise find an old tube amp with 30 watts or better output and remove the output transformer. Hook it reversed from the amp output to the 6146. I've used both systems will good results. Healthfully yours, DON W4BWS - Original Message - From: "Harry Vaught" <[EMAIL PROTECTED]> To: "Discussion of AM Radio" Sent: Friday, March 17, 2006 7:13 AM Subject: Re: [AMRadio] Amplifier to use with my DX-60 > Ok, tell me this: > > I have a DX-60A and a 25 watt P-P 6L6 Webster Electric PA amp with a > large selection of output impedances. What would I have to do to plate > modulate my DX-60? > > There are obviously greatly varying levels of knowledge out there, and > mine is probably below median. > > Harry, KT4AE > Maryville, Tennessee > __ > 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, Paul Courson/wa3vjb >
[AMRadio] AM transmitter coming available
I'm in the process of getting approval to dispose of our good old RCA BTA-5T transmitter. Sad duty, since it's the rig I grew up listening toand I don't have the room to take it.. This is a 5 KW/1KW AM transmitter in operating condition, currently on 910 KC. Three phase power. This one has been modified with ceramic tubes in the modulator (3CX3000's if I remember correctly). Essentially a drop-in change. The company would like to get $500 for the rig. There is still a small chance they may want to part it out throughout the company. But if they decide to dispose of it, you pick up in York, PA. Anyone interested? Robert A. Poff / WB3AWJ Chief Engineer WSBA / WARM-FM/ WSOX Susquehanna Radio Corp.
RE: [AMRadio] Amplifier to use with my DX-60
Yep, there is no doubt that the pair of 3-500Zs and getting rid of the control carrier on the DX60 would be better but a lot more expense I think. Aren't 3-500Zs pretty expensive? John -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Jim candela Sent: Friday, March 17, 2006 10:00 AM To: Discussion of AM Radio Subject: RE: [AMRadio] Amplifier to use with my DX-60 John, Your approach as always is a good one, and can be made to work out quite well. This extra box will allow about a 6DB increase in power from what a screen modulated 6146 can do. The DX-60 with carrier control can arguably better match up to a linear amplifier, but must of us would agree that carrier control as done on this rig is too much, and annoying to those copying a weak signal that goes into and out of the noise with modulation peaks. Now consider these options: 1.) Modify the DX-60 for non carrier control screen modulation. That should provide about 20 watts carrier with room for + 100% modulation. 2.) Modify the DX-60 for plate modulation. This might require a 6146 bias change for proper class C plate modulation bias. You will also have to deal with modulating the screen grid. The plate tuning capacitor might flash over, and other components may need to be beefed up to handle the higher peak power. Once done, you will have a fine 45-50 watt AM rig that you could be proud of. 3.) Combine option 1 with this: Mate up the modified DX-60 to a linear with 1000 watts of dissipation available (like two 3-500Z's). Now you can easily run 250 watts AM or more (maybe 375) of quality AM. 4.) Use the DX-60 as is (stock), or with an amplifier as you wish. The choice is yours, Jim WD5JKO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of John E. Coleman (ARS WA5BXO) Sent: Thursday, March 16, 2006 9:10 PM To: 'Discussion of AM Radio' Subject: RE: [AMRadio] Amplifier to use with my DX-60 I still say, forget the linear, and use less money to build a plate modulator for the DX60. It will work better, sound better, cost less, and heat the shack up less. As I recall the DX 60 has a 6146 in the final for class C CW and puts out about 40-50 watts of carrier if it were plate modulated it would do at least 200 watts PEP and sound great. There is a number of different ways to do the modulator. A lot of guys just find and old PA and a transformer to match to the final. Some build the modulator output stages only, input XFMR tubes and modulation XFMR. Then they drive it with a small microphone amp. That's more stuff to set around on the desk but it works. There are a lot of self contained 25 and 50 watt modulator circuits around and probably a lot of complete one piece store bought modulators as well. As I recall, EICO had a pretty nice one that was to go with the EICO model 720 but it was used on many different rigs as well as being used as a driver for big modulators. A buddy of mine had an ECIO 720 and built a nice home brewed modulator for it using 1625s in AB1. It sounded real good. I built one similar to it with less power output for my Knight Kit T60. The T60 had the same control carrier AM that the DX60 does. What a difference it made when it was plate modulated. Very little modification is necessary in the DX60 to accommodate the external modulator. John, WA5BXO __ 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, Paul Courson/wa3vjb -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.1.385 / Virus Database: 268.2.4/283 - Release Date: 3/16/2006 -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.1.385 / Virus Database: 268.2.4/283 - Release Date: 3/16/2006 __ 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, Paul Courson/wa3vjb
RE: [AMRadio] Amplifier to use with my DX-60
John, Your approach as always is a good one, and can be made to work out quite well. This extra box will allow about a 6DB increase in power from what a screen modulated 6146 can do. The DX-60 with carrier control can arguably better match up to a linear amplifier, but must of us would agree that carrier control as done on this rig is too much, and annoying to those copying a weak signal that goes into and out of the noise with modulation peaks. Now consider these options: 1.) Modify the DX-60 for non carrier control screen modulation. That should provide about 20 watts carrier with room for + 100% modulation. 2.) Modify the DX-60 for plate modulation. This might require a 6146 bias change for proper class C plate modulation bias. You will also have to deal with modulating the screen grid. The plate tuning capacitor might flash over, and other components may need to be beefed up to handle the higher peak power. Once done, you will have a fine 45-50 watt AM rig that you could be proud of. 3.) Combine option 1 with this: Mate up the modified DX-60 to a linear with 1000 watts of dissipation available (like two 3-500Z's). Now you can easily run 250 watts AM or more (maybe 375) of quality AM. 4.) Use the DX-60 as is (stock), or with an amplifier as you wish. The choice is yours, Jim WD5JKO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of John E. Coleman (ARS WA5BXO) Sent: Thursday, March 16, 2006 9:10 PM To: 'Discussion of AM Radio' Subject: RE: [AMRadio] Amplifier to use with my DX-60 I still say, forget the linear, and use less money to build a plate modulator for the DX60. It will work better, sound better, cost less, and heat the shack up less. As I recall the DX 60 has a 6146 in the final for class C CW and puts out about 40-50 watts of carrier if it were plate modulated it would do at least 200 watts PEP and sound great. There is a number of different ways to do the modulator. A lot of guys just find and old PA and a transformer to match to the final. Some build the modulator output stages only, input XFMR tubes and modulation XFMR. Then they drive it with a small microphone amp. That's more stuff to set around on the desk but it works. There are a lot of self contained 25 and 50 watt modulator circuits around and probably a lot of complete one piece store bought modulators as well. As I recall, EICO had a pretty nice one that was to go with the EICO model 720 but it was used on many different rigs as well as being used as a driver for big modulators. A buddy of mine had an ECIO 720 and built a nice home brewed modulator for it using 1625s in AB1. It sounded real good. I built one similar to it with less power output for my Knight Kit T60. The T60 had the same control carrier AM that the DX60 does. What a difference it made when it was plate modulated. Very little modification is necessary in the DX60 to accommodate the external modulator. John, WA5BXO __ 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, Paul Courson/wa3vjb -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.1.385 / Virus Database: 268.2.4/283 - Release Date: 3/16/2006 -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.1.385 / Virus Database: 268.2.4/283 - Release Date: 3/16/2006
Re: [AMRadio] Amplifier to use with my DX-60
You have an interesting point here John. I don't know if I have access to enough "STUFF" to do a job like that, I am fairly isolated here on PEI. It is almost better to find a Johnson Transmitter or something. I AM going to try a 160 meter end fed Zepp to get some height and gain off my antenna. Cheers, Alan John E. Coleman (ARS WA5BXO) wrote: I still say, forget the linear, and use less money to build a plate modulator for the DX60. It will work better, sound better, cost less, and heat the shack up less. As I recall the DX 60 has a 6146 in the final for class C CW and puts out about 40-50 watts of carrier if it were plate modulated it would do at least 200 watts PEP and sound great. There is a number of different ways to do the modulator. A lot of guys just find and old PA and a transformer to match to the final. Some build the modulator output stages only, input XFMR tubes and modulation XFMR. Then they drive it with a small microphone amp. That's more stuff to set around on the desk but it works. There are a lot of self contained 25 and 50 watt modulator circuits around and probably a lot of complete one piece store bought modulators as well. As I recall, EICO had a pretty nice one that was to go with the EICO model 720 but it was used on many different rigs as well as being used as a driver for big modulators. A buddy of mine had an ECIO 720 and built a nice home brewed modulator for it using 1625s in AB1. It sounded real good. I built one similar to it with less power output for my Knight Kit T60. The T60 had the same control carrier AM that the DX60 does. What a difference it made when it was plate modulated. Very little modification is necessary in the DX60 to accommodate the external modulator. John, WA5BXO __ 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, Paul Courson/wa3vjb
Re: [AMRadio] Amplifier to use with my DX-60
Thank you Tom. ;-) I love been a thread seed. You guys have all been great in helping me decide which linear to seek out in the Heathkit cheapo line. so, is the 220/230 the best choice to get the job done. I think from what I am seeing here that the 200 just would not cut it. 73, Alan [EMAIL PROTECTED] wrote: If I understand these responses this all boils down to answer Alan's original question and that is that a SB-200 would be ok with the DX-60 at the DX-60's max output . Correct? Tom K3TVC - Original Message - From: "Mike Dorworth, K4XM" <[EMAIL PROTECTED]> To: "Discussion of AM Radio" Sent: Thursday, March 16, 2006 5:45 PM Subject: Re: [AMRadio] Amplifier to use with my DX-60 YUP. The two things are the tubes and the power supply.. One half dissipation is MAX.. you are using 800 watt tubes so 400Watt carrier is max. The Thunderbolt has a real power supply, so, sure 300 watts is fine.Since SSB is 25 to 30 percent average of peaks the manufactures can squeeze in small supplies for voice or CW service. Ever make you wonder that they might allow 2500 watts input SSB but only 400 for RTTY. AM and RTTY separates the Men from the boys.. Mike - Original Message - From: "Dale Smith" <[EMAIL PROTECTED]> To: "Mike Dorworth, K4XM" <[EMAIL PROTECTED]>; "Discussion of AM Radio" Sent: Thursday, March 16, 2006 5:43 PM Subject: Re: [AMRadio] Amplifier to use with my DX-60 How about a Johnson thunder bolt is 300 watt carrier ok ? I hope so cause that is what I have been doing The transformer in there is twice as big as my swan mark 1. thanks ..de/dale/ka5who __ 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, Paul Courson/wa3vjb __ 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, Paul Courson/wa3vjb
Re: [AMRadio] Amplifier to use with my DX-60
Ok, tell me this: I have a DX-60A and a 25 watt P-P 6L6 Webster Electric PA amp with a large selection of output impedances. What would I have to do to plate modulate my DX-60? There are obviously greatly varying levels of knowledge out there, and mine is probably below median. Harry, KT4AE Maryville, Tennessee
Re: [AMRadio] Amplifier to use with my DX-60
My main concern Don is that giving out a calculated carrier level for a set of tubes to a guy who does not have a scope and audio generator is not going to give the amateur band another clean signal. As I mentioned in a previous email, I have been unable to obtain the efficiencies you mention and would like to hear from someone who can measure everything with test equipment and tell me about it. Thanks, Ken W2DTC From: "kenw2dtc" <[EMAIL PROTECTED]> Don says: "So you could run maximum 1500 watts DC input to those tubes, with 500 watts carrier output, and 1000 watts dissipated by the tubes" ***I need a little help with the math here Don. You are suggesting that with a class B linear in AM mode, one can get 2000 watts PEP with 1500 watts input ? Assuming 100% positive peak modulation, yes. ___ This message was typed using the DVORAK keyboard layout. Try it - you'll like it. http://www.mwbrooks.com/dvorak/ http://gigliwood.com/abcd/ __ 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, Paul Courson/wa3vjb
