Re: [AMRadio] T3 Mod iron specs - Audio limitations, harmonics, etc.
On Thu, Feb 21, 2008 at 1:47 AM, Ed Sieb [EMAIL PROTECTED] wrote: With the stock iron, there was a noticeable improvement in the low end response. Further improvement can only be obtained by installing a different modulation transformer. Yep, not unlike the Valiant and a few others. They can be made to sound 'better', but only to the limit of the iron. My big xmtr was instead limited mainly by couple caps, resistors, and so on. Done about halfway through the production run to limit response and increase punch through the noise. Simple changes back to something close to earlier values improved audio considerably, without dirtying up the signal. An OT once told me with respect to audio that anytime you add 'more' stages, processing, etc, you also introduce more distortion. And somewhere along the way I picked up the term 'outboard distortion' to describe outboard processing. There are more than a few folks with artificially-enhanced voice characteristics (added bass comes to mind) resulting in audio that pops up and down the band 10+ kc/s either side. Not sure it it's a result of where they added it inline or more a product of bad set up. It would make sense that if you don't address shortcomings in the rig like components or iron, and then run through them to some degree, you'd be asking for trouble. There are also some stations out there with custom audio that sound fabulous, and have clean signals despite being a bit wide in the eyes of some. So it can obviously be done right. No doubt has a lot to do with what you're trying to push the outboard audio through. The old saying 'you can't polish a turd' comes to mind... ~ Todd, KA1KAQ __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
[AMRadio] Re: T3 Mod Iron Specs
Anyone know the approximate designed frequency range for a T-368 modulation transformer? Brian / wa5am The frequency range of the standard T-368 mod-transformer is 300 - 3500 CPS. The mod iron is rated for 250 watts MAX., with a peak working voltage of 5000, and max altitude operating range of 10,000 ft. Maximum rated carrier power out of a standard T-368 400 Watts AM voice, and AM FSK, and 450 watts CW/FSK. NOTE: that is two different ratings for FSK mode. Jim WB2FCN We all know that a modified T-368 can do much better than that. It is not unusual for a transformer to vastly exceed the nominal frequency response given in the specs. 300-3500~ is the minimum guaranteed response, +/- a given number of dB's. If the actual transformer exceeds that, it still meets those contracted specs. I once used an audio driver tranformer, made by Chicago Transformer Co, with those same exact specs stamped on the case, but the thing was actually flat from well below 100 Hz to beyond 7 or 8 kHz. So unless you plan to run communications grade audio, those specs are meaningless, except for giving you an idea of how poor the response might be. In many cases, I suspect the communications-grade transformer comes from the same stock as similar transfromers rated for broadcast or other higher audio quality applications, and the company simply stamped the minimum ratings spelt out in the contract, instead of going to the expense and trouble of modifying an existing design to degrade its frequency response down to communications grade, unless the customer specifically demanded it. After all, what would be objectionable about shipping out a lower cost product whose quality is actually superior to what was called for? To determine the real response, you need to test the transformer with a signal generator. Load the secondary with the specified resistive load. Put maybe half the specified primary impedance in series with the primary, and connect to the generator. Sweep the frequency response using a scope or good audio level meter. Many VOM's have a calibrated dB scale. You will need a generator capable of delivering enough voltage to get a good reading on the scope or meter. You may be surprised how good the response on that transformer is. IIRC, the BC-610 audio is specified at 100-5000~, and I suspect that transformer will turn out at least as good. Let's say your transmitter is limited for 200 to 3000 cycles in the audio section, either by coupling caps, cathode bypass, cathode resistors, plate loading, and any transformers... what is the result of using an external EQ and audio chain that pumps audio from the mic that is beyond either end of the audio range the transmitter is allowed by design to pass? I think this is a common mistake that a lot of us make that can cause some serious harmonics and other artifacts. According to the engineering data included in one of my UTC catalogues, they recommend that the flat frequency response of an audio transformer should extend one octave above and one octave below the intended frequency response expected from the amplifier, to assure that the audio waveform coming out of the transformer is close to identical to what is fed into the transformer. Low frequency phase shift may alter the assymetry of the voice waveform, and, with a pushpull amplifier, high frequency phase shift may result in objectionable distortion caused by one side of the pushpull circuit not being exactly 180 degrees out of phase with the other. You can test the phase shift response of a balanced transformer with an oscilloscope. Feed audio into the transformer with a wide-range audio signal generator. On each balanced primary or secondary winding, connect the ground side of the scope to the midtap of the transformer winding, and connect one end of the winding to the horizontal input to the scope, and the other end to the vertical input. Adjust both horizontal and vertical gain for equal deflection on the scope tube. If there is no phase shift, you should see a straight diagonal line. If there is phase shift, the diagonal line will expand into an elongated oval shape. In the worst case, with 90 degrees of phase shift, the pattern will become a perfect circle. If it is a pushpull grids to pushpull plates transformer, run the test with both windings, by reversing primary and secordary and re-running the test. If there is a balanced 500/600 ohm output with a midtap, run the test with that winding as well. While you may not even use the midtap, the test will nevertheless give you an idea of the phase linearity of the transformer. Throughout the useful frequency range of the transformer, you should see the straight diagonal. At either end of the response, it will begin to fatten out into an oval. If there is any nonlinearity, which may occur at the extreme ends of the response curve, the diagonal line may show curvature
[AMRadio] Knob
I have a knob that appears to be from a NC 173 or 183, I am not sure which. The color is the light gray and the skirt is the same as my other National products. The skirt is marked 5-0-5 over 180 degrees. This is typical of a CWO or phasing knob. I don't have a receiver of this color, so the knob is excess to me. Does anyone NEED it? Not does anyone collect them, but do you need it for your receiver that you use? Please contact me at [EMAIL PROTECTED] direct, not on the list please. Jim/W5JO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
Re: [AMRadio] T3 Mod iron specs - Audio limitations, harmonics, etc.
I think, if the other stages pass wide range audio, you can boost the fidelity some with EQ, but I would not push it to hard. In most cases, you dont really need to, you just need to correct for a crappy microphone and your voice. I think we have all heard people who sounded great running stock rigs like the 32V3 and a decent mic. I dont remember who it was, but I do remember someone just like that, stock 32V3 and a Sure 55s or something like that. I dount think he would have sounded better on a broadcast rig. But the mod iron can alter your voice, some need less bass, other people sound better with some boost. I used to run a CVM5 mod trans, and when I got the RCA transformers, sold the cvm5 because it sounded so poor compaired to the RCA. I think the trick of running everything gently helps, gentle EQ, gentle compression, gentle modulator output, gentle final power percentage, gentle modulation percentage. Its best it build big and run it easy, with as much audio power output avalable as rf power input. Brett N2DTS - Original Message - From: A.R.S. - WA5AM [EMAIL PROTECTED] To: Discussion of AM Radio in the Amateur Service amradio@mailman.qth.net Sent: Wednesday, February 20, 2008 6:02 PM Subject: [AMRadio] T3 Mod iron specs - Audio limitations, harmonics, etc. Anyone know the approximate designed frequency range for a T-368 modulation transformer? Also, if there is a website out there somewhere that has stock audio specs on the popular commercial and military transmitters, I would be interested in seeing it. I think I know the answer to this, however I know there are a lot of you out there that have a lot more knowledge than I do on the specifics... Let's say your transmitter is limited for 200 to 3000 cycles in the audio section, either by coupling caps, cathode bypass, cathode resistors, plate loading, and any transformers... what is the result of using an external EQ and audio chain that pumps audio from the mic that is beyond either end of the audio range the transmitter is allowed by design to pass? I think this is a common mistake that a lot of us make that can cause some serious harmonics and other artifacts. I'd like to see a discussion on this if any of you experts would care to chime in ;) 73 Brian / wa5am -- Money is only temporary, radios are forever - Jim Little aka the old dawg/K5BAI __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
[AMRadio] AMfone
Is it just my connection or is Amfone running very slow to others tonight? Rick/K5IAR __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
Re: [AMRadio] AMfone
Rick: Is it just my connection or is Amfone running very slow to others tonight? Your message dated 8:26 PM got here at 8:31. - Jim WB6BLD __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
Re: [AMRadio] AMfone
Site is down Rick . I ahve been trying to connect to the provider. Update to follow Rick wrote: Is it just my connection or is Amfone running very slow to others tonight? Rick/K5IAR __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] AMfone
Thanks Gary. Sorry you're having all the problems. Rick Site is down Rick . I ahve been trying to connect to the provider. Update to follow __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
Re: [AMRadio] AMfone
Yes it is. I can't even connect up to it. Ellen - AF9J - Original Message - From: Rick [EMAIL PROTECTED] To: 'Discussion of AM Radio in the Amateur Service' amradio@mailman.qth.net Sent: Thursday, February 21, 2008 7:26 PM Subject: [AMRadio] AMfone Is it just my connection or is Amfone running very slow to others tonight? Rick/K5IAR __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
Re: [AMRadio] AMfone
Darn! I was going to write some hot stuff about ARRL and IARU. Pete, wa2cwa On Thu, 21 Feb 2008 20:33:27 -0500 W2INR [EMAIL PROTECTED] writes: Site is down Rick . I ahve been trying to connect to the provider. Update to follow Rick wrote: Is it just my connection or is Amfone running very slow to others tonight? Rick/K5IAR __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
Re: [AMRadio] AMfone
Post it here Pete. Jim/W5JO Make sure you include the AM connection. Darn! I was going to write some hot stuff about ARRL and IARU. Pete, wa2cwa __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
Re: [AMRadio] Hot Stuff
Hello Pete, You mean about those secret papers from the Dallas County district attorney's safe that was opened Monday? :) 73, Bruce WA8TNC == Peter Markavage wrote: Darn! I was going to write some hot stuff about ARRL and IARU. Pete, wa2cwa __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
[AMRadio] 70 ft tower Plus antennas FREE
From Craigslist http://nh.craigslist.org/zip/581988244.html Located Hudson NH. **Ideas to please picky eaters. Watch video on AOL Living. (http://living.aol.com/video/how-to-please-your-picky-eater/rachel-campos-duffy/ 2050827?NCID=aolcmp0030002598) __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
Re: [AMRadio] Hot Stuff
You're one up on me Bruce; safe was opened Monday in the AM. And AMfone is back. Pete, wa2cwa On Thu, 21 Feb 2008 21:34:27 -0500 BSugarberg [EMAIL PROTECTED] writes: Hello Pete, You mean about those secret papers from the Dallas County district attorney's safe that was opened Monday? :) 73, Bruce WA8TNC == Peter Markavage wrote: Darn! I was going to write some hot stuff about ARRL and IARU. Pete, wa2cwa __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
