You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.
The Feb 2025 Radioddity Giveaway Results are In! Click Here to see who won!

Reply to thread

Message

The distortion introduced by the NPC circuit will be MUCH less than from baselining the audio.

Another issue is this: If you DO manage to drop the carrier to insane levels, the RECEIVING detector is 9 out of 10 times a simple diode.... And THEY can't handle the distortion created when going much over about 150 percent positive mod.... Hence the FCC mandated 125 percent MAX on broadcash equip... During the "loudness wars" of the broadcash days, it was common to run 200+++ percent positive modulation, and they'd use a circuit similiar to the one I posted to limit baselining the audio.

The way the 29 (and most other transformer modulated / plate modulated ) / 25 / 21 / etc hit 75 watts PEP is this: The transformer in them is connected as an AUTOTRANSFORMER... The MODULATED voltage is MUCH more than 13.8 volts! 13 volts is actually the CARRIER voltage... They need to impress ANOTHER 13 volts on TOP of it to get 100 percent modulation... Which will quadruple the output, giving the textbook 4 to 1 carrier to PEP level we look for. It is possible (if I remember correctly, it's been about 6 to 10 years since I tried doing one, and EVERY chassis was INDIVIDUALLY tuned on the output pi network to hit > 45 watts!!!!) to get near 40 - 50 volts PEAK on the output of the transformer.

A LOT of the AVG increase is due to the non-baselining. If you limit the negative excursions of the negative peaks so that they NEVER cause a FLATLINE in the modulated RF envelope, you cause a LARGE increase in output power on an AVG reading meter... And you will also notice a lot of increase in range, all other things being equal... Although our ear responds to peak power, the AVG power is what actually gets the signal through.... Just like in cars, it's 'torque under the curve' that actually gets the job done, not just a 1000 horsepower engine... One that produces torque from 1800 rpm to 6000 at 800 peak horsepower will EAT a 1000 horsepower engine that ONLY produces torque in a couple thousand RPM powerband. If you can increase the AVERAGE power output of your radio (which is ALL NPC does), you've won half the battle..... LIMITING the negative peaks and ensuring you have asymetrical mod (which you'd need a good avg meter or scope to see) so your positive peaks are GREATER than your negative is also beneficial, as it increases the PEAK power on the modulator.

--Toll_Free

<blockquote data-quote="Toll_Free" data-source="post: 253333" data-attributes="member: 1736">The distortion introduced by the NPC circuit will be MUCH less than from baselining the audio.Another issue is this:&nbsp; If you DO manage to drop the carrier to insane levels, the RECEIVING detector is 9 out of 10 times a simple diode....&nbsp; And THEY can&#039;t handle the distortion created when going much over about 150 percent positive mod....&nbsp; Hence the FCC mandated 125 percent MAX on broadcash equip...&nbsp; During the &quot;loudness wars&quot; of the broadcash days, it was common to run 200+++ percent positive modulation, and they&#039;d use a circuit similiar to the one I posted to limit baselining the audio.The way the 29 (and most other transformer modulated / plate modulated ) / 25 / 21 / etc hit 75 watts PEP is this:&nbsp; The transformer in them is connected as an AUTOTRANSFORMER...&nbsp; The MODULATED voltage is MUCH more than 13.8 volts!&nbsp; 13 volts is actually the CARRIER voltage...&nbsp; They need to impress ANOTHER 13 volts on TOP of it to get 100 percent modulation...&nbsp; Which will quadruple the output, giving the textbook 4 to 1 carrier to PEP level we look for.&nbsp; It is possible (if I remember correctly, it&#039;s been about 6 to 10 years since I tried doing one, and EVERY chassis was INDIVIDUALLY tuned on the output pi network to hit &gt; 45 watts!!!!) to get near 40 - 50 volts PEAK on the output of the transformer.A LOT of the AVG increase is due to the non-baselining.&nbsp; If you limit the negative excursions of the negative peaks so that they NEVER cause a FLATLINE in the modulated RF envelope, you cause a LARGE increase in output power on an AVG reading meter...&nbsp; And you will also notice a lot of increase in range, all other things being equal...&nbsp; Although our ear responds to peak power, the AVG power is what actually gets the signal through....&nbsp; Just like in cars, it&#039;s &#039;torque under the curve&#039; that actually gets the job done, not just a 1000 horsepower engine...&nbsp; One that produces torque from 1800 rpm to 6000 at 800 peak horsepower will EAT a 1000 horsepower engine that ONLY produces torque in a couple thousand RPM powerband.&nbsp; If you can increase the AVERAGE power output of your radio (which is ALL NPC does), you&#039;ve won half the battle.....&nbsp; LIMITING the negative peaks and ensuring you have asymetrical mod (which you&#039;d need a good avg meter or scope to see) so your positive peaks are GREATER than your negative is also beneficial, as it increases the PEAK power on the modulator.--Toll_Free</blockquote>

[QUOTE="Toll_Free, post: 253333, member: 1736"] The distortion introduced by the NPC circuit will be MUCH less than from baselining the audio. Another issue is this: If you DO manage to drop the carrier to insane levels, the RECEIVING detector is 9 out of 10 times a simple diode.... And THEY can't handle the distortion created when going much over about 150 percent positive mod.... Hence the FCC mandated 125 percent MAX on broadcash equip... During the "loudness wars" of the broadcash days, it was common to run 200+++ percent positive modulation, and they'd use a circuit similiar to the one I posted to limit baselining the audio. The way the 29 (and most other transformer modulated / plate modulated ) / 25 / 21 / etc hit 75 watts PEP is this: The transformer in them is connected as an AUTOTRANSFORMER... The MODULATED voltage is MUCH more than 13.8 volts! 13 volts is actually the CARRIER voltage... They need to impress ANOTHER 13 volts on TOP of it to get 100 percent modulation... Which will quadruple the output, giving the textbook 4 to 1 carrier to PEP level we look for. It is possible (if I remember correctly, it's been about 6 to 10 years since I tried doing one, and EVERY chassis was INDIVIDUALLY tuned on the output pi network to hit > 45 watts!!!!) to get near 40 - 50 volts PEAK on the output of the transformer. A LOT of the AVG increase is due to the non-baselining. If you limit the negative excursions of the negative peaks so that they NEVER cause a FLATLINE in the modulated RF envelope, you cause a LARGE increase in output power on an AVG reading meter... And you will also notice a lot of increase in range, all other things being equal... Although our ear responds to peak power, the AVG power is what actually gets the signal through.... Just like in cars, it's 'torque under the curve' that actually gets the job done, not just a 1000 horsepower engine... One that produces torque from 1800 rpm to 6000 at 800 peak horsepower will EAT a 1000 horsepower engine that ONLY produces torque in a couple thousand RPM powerband. If you can increase the AVERAGE power output of your radio (which is ALL NPC does), you've won half the battle..... LIMITING the negative peaks and ensuring you have asymetrical mod (which you'd need a good avg meter or scope to see) so your positive peaks are GREATER than your negative is also beneficial, as it increases the PEAK power on the modulator. --Toll_Free [/QUOTE]

Top Bottom