rest of Cobra 148F thread

[psycho]

I really would like to know what meter you are checking it on. The 148F is a single final radio and with the limiter clipped and the final volted at the most they'll swing 9-11 watts Bird 43 RMS. The 23 watts peak sounds OK.
SSB average talk maybe 16-20 watts Bird 43 RMS but 28 is impossible.
I have done all the nasty big swing mods to 148s before..... that would sicken all the clean radio lobbyists on this forum but unless a 2nd final or a 2030 was installed, no way.
If an ERF-2030 was installed disregard my post.

 

[nightrider]

the numbers i posted are very possiable, and have been documented on many occasions, my meter is my trusty rat shack, also power supply is set to 14.6 volts but as always it cant be done !!! cant be done !! well single final exports do over 30 peak, why cant a regular 148 ???? these are the numbers i saw take them as they are !!! if you dont beleive them then dont beleive them !!! dont matter anyhow :roll:

 

[psycho]

the numbers i posted are very possiable, and have been documented on many occasions, my meter is my trusty rat shack, also power supply is set to 14.6 volts but as always it cant be done !!! cant be done !! well single final exports do over 30 peak, why cant a regular 148 ???? these are the numbers i saw take them as they are !!! if you dont beleive them then dont beleive them !!! dont matter anyhow :roll:

First of all Moleculo is one of overwhelming majority on this forum that believes that modulating over 100% is a mortal sin. The "numbers" you included translate into modulating so far above 100% that the purists on this forum would go into cardiac arrest.
Exaggerate if you must but the numbers are laughable. I am impressed that moleculo got it up and running but reading his posts to the forum and me it is obvious that he would never set up a radio to overmodulate with the #s you submitted since he is completely against clipping mod limiters.
Most dual final exports will do 30 watts peak so let's leave it at that.
I am just giving you the facts.

 

[psycho]

psycho, the radio modification that he did is one that I perfected years ago. I assure you that the radio does not severely overmodulate. The reason is over your head a bit, but basically the carrier varies in proportion to the modulation.

This does two things. It keeps everything in proportion, and the carrier to peak ratio correct, and also keeps people happy who like the use RMS watt meters to read AM because of their lack of knowledge.

I know you wouldn't know to be concerned about it, but the modification also includes many changes to the audio circuit for a wider frequency response, as well as modification in the transmit mixer, and the bias circuit to keep it from sagging, or going negative on voice peaks, due to the higher output.

If you have a technical comment on this please feel free to respond. I won't bother if your post has the following words:

1: mudduck
2: swing
3: maul
4: SRW's
5: supabowl

You can howl at the moon all you want. If you are in Florida and think one of your copy cat tuneups can outdo one of my 148s on a Bird 43 or 43P I will give you my radio.
You are not the pioneer of CB radio tuneups but if you want to check our radios on a watt meter for "Pinks"....bring it on anytime. 28 watts RMS out of a 2SC1969???????? That's just wonderful. :roll:
Did you and Al Gore invent the internet on a joint venture too? 8)

 

[ken white]

...and also keeps people happy who like the use RMS watt meters to read AM because of their lack of knowledge...

Will you explain this part of your quote?

It is much easier to make a fairly accurate Peak meter, while a true RMS/Average power meter is more difficult to design due to the fast rate of change in energy, but there is only one measure of power and it is the amount of energy transferred/accepted per second, which is RMS/Average.

A Peak meter cannot ever accurately convey the rate of change of energy, but it does give a good indication of modulation which is the only benefit of PEP.

 

[Moleculo]

A couple things:

1. The 28 watts Nightrider is talkign about is accurate, but it's not an Average / RMS reading. It's taken using a Bird 43P.

2. I never said that I thought modulation over 100% was a mortal sin. I've said that most of the cb tunes that are overmodulated sound like crap. Even broadcast AM stations use compression and other techniques to get 100+% modulation.(in the U.S. they're allowed to go to 125% modulation on positive peaks.) The key is balance and how to do it to so as not distort. Distorion and "splatter: are the nasties, IMO

3. RMS vs. Peak measurements...here we go again LOL: Both measurements are important to understand. I'm no broadcast engineer, but my understanding is that the power measurements the FCC requires for broadcast AM all use the "nominal power" method. Nominal power is a function of the instantaneous maximum level of the modulated radio frequency envelope, or "peak" power. In the amateur arena, PEP measurements are required at the transmitter to determine compliance, not average measurments. My way of thinking is that if the FCC is telling us that they want the measurements done using peak methods in both commercial and amateur services, then that's good enough for me....

 

[Moleculo]

If you are in Florida and think one of your copy cat tuneups can outdo one of my 148s on a Bird 43 or 43P I will give you my radio

You really should read more carefully / completely before just starting to hit the "reply" button.

Nightrider never said this was about a keydown contest. I bought the radio from him, tuned it up, made audio changes thanks to some help from Justin, fixed a few things, did a full alignment on the radio (RX alignment was way out of whack when I got it) and used it. When Nightrider wanted to buy it back, I sent it back with the changes and apparently he's happy. Where was the "my tune method is better than yours" message in this?

BTW, the changes that I did aren't 10 minute changes. It takes me about an hour just to do the modifications (I work slow and carefully), not including the alignment. They're not exactly the typcal snip/turn the pot kind of mods. On this one, I left the limiter intact; I know Justin has said that on this radio it's possible to remove it with his modification methods, but it makes me feel warm and fuzzy with it still there

 

[ken white]

...3. RMS vs. Peak measurements...here we go again LOL: Both measurements are important to understand. I'm no broadcast engineer, but my understanding is that the power measurements the FCC requires for broadcast AM all use the "nominal power" method. Nominal power is a function of the instantaneous maximum level of the modulated radio frequency envelope, or "peak" power. In the amateur arena, PEP measurements are required at the transmitter to determine compliance, not average measurments. My way of thinking is that if the FCC is telling us that they want the measurements done using peak methods in both commercial and amateur services, then that's good enough for me....

From: 47CFR73.51;

"Determining operating power.
(a) Except in those circumstances described in paragraph (d) of this section, the operating power shall be determined by the direct method. The direct method consists of either:
(1) using a suitable instrument for determining the antenna's input power directly from the RF voltage, RF current, and phase angle; or"

When calculating power using V x I x Cos (phase angle), which is what (1) is stating, the result will be RMS/Average/True Power which are all the same...

Where did you get your information that nominal means peak?


From 47CFR73.14;

"AM broadcast definitions.
Nominal power. The antenna input power less any power loss through a dissipative network..."

In one of my other posts I have shown that for a single tone, amplitude modulated signal that PEP and RMS are related, but RMS is the value used not PEP.

http://forum.worldwidedx.com/viewtopic.php?t=16238&start=30

When the carrier is modulated by any mixed signals, the envelope is indeterminate and therefore the true power is unknown with PEP measurements. This is why tests are conducted with controlled signals to get controlled results which is what the FCC expects.

 

[psycho]

A couple things:

1. The 28 watts Nightrider is talkign about is accurate, but it's not an Average / RMS reading. It's taken using a Bird 43P.

2. I never said that I thought modulation over 100% was a mortal sin. I've said that most of the cb tunes that are overmodulated sound like crap. Even broadcast AM stations use compression and other techniques to get 100+% modulation.(in the U.S. they're allowed to go to 125% modulation on positive peaks.) The key is balance and how to do it to so as not distort. Distorion and "splatter: are the nasties, IMO

3. RMS vs. Peak measurements...here we go again LOL: Both measurements are important to understand. I'm no broadcast engineer, but my understanding is that the power measurements the FCC requires for broadcast AM all use the "nominal power" method. Nominal power is a function of the instantaneous maximum level of the modulated radio frequency envelope, or "peak" power. In the amateur arena, PEP measurements are required at the transmitter to determine compliance, not average measurments. My way of thinking is that if the FCC is telling us that they want the measurements done using peak methods in both commercial and amateur services, then that's good enough for me....

I have only used 3 types of meters. Bird 43, Bird 43P, and a Comet CMX-1. Those meters read real true RMS but the 43P reading is believeable although I still think that would really stress out a 2SC1969.

 

[Butcher318]

Nightrider, i'm sure the radio sounds great and all the mods are well done and working as they should. Your numbers do seem on the Hi side though, and a Rat Shack meter....come on.

As general occurance people always seem to quote unrealistic wattage numbers from their radio's. I wish people would get real on that stuff.

Justin, about 1 1/2 years ago I was very excited to have a radio tuned by you. It was supposed to be doing 51 peak watts on AM on a Bird 43P. The forum here hyped you up pretty good so my expectations were hi. I got the radio and rushed over to the local techs house to impress him with a 51 watt dual final radio. Bottom line, 38 watts peak into a dummy load and Bird 43P, mic gain cranked, steady 14.5 volts. But to actually talk on the radio and sound good the mic gain had to be backed down. This dropped the peak power to 30-32 watts.

Mole, I'm sure you did a bang up job on the radio, and justin your a sharp guy. I just wish people would make wattage claims that people will actually see.

There, no bashing just discussion so lets not delete this post like so many others. That gets old too.

 

[2M Guy]

Average isn't a very good way to measure SSB.

 

[ken white]

Average isn't a very good way to measure SSB.

With a two tone test signal, the SSB PEP can be directly calculated into an equivalent RMS power.

 

[Happy_Hamer]

Well I think if you want to save money just buy a radio shack watt meter and cut your CB antenna 1 inch at a time until you see the maximum wattage, i think you will be happy.

Results may vary, do at your own risk. I am not a professional

 

[Moleculo]

Where did you get your information that nominal means peak?

I didn't say it meant peak. I said, "Nominal power is a function of the instantaneous maximum level of the modulated radio frequency envelope, or "peak" power." A "function of", not "equal to".

However, I see where I misread and lumped in the formulas for calculating modulation percentage with the text on nominal power. Here the source that messed me up: (Scroll down to the definition of modulation percentage, you'll see where I mistook that for part of the paragraph for Nominal Power)

http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&rgn=div6&view=text&node=47:4.0.1.1.2.1&idno=47

I still wish people would get away from the term "RMS Power", when they really mean "Average Power". RMS is a measurement of voltage, not wattage. I know, the term is meant to say that the RMS method of calculating voltage is used to determine power levels, but it's still confusing to the casual reader.

It seems to me the FCC has been trying to get away from Average power measurements (at least for the Amateur world)? All the Amatuer requirements are stated in terms of PEP now. All my equipment that has built in meters (tuners, amps, etc.) all have active peak reading meters. My Bird has the peak kit...I really only have one meter that doesn't have an active peak reading circuit anymore.

Back on topic, I seem to recall that the Bird 43P readings on my bench at 14 volts were in the neighborhood of 26 watts peak on SSB, so his readings sound similar. I don't really see how that would stress a 1969 final. I've seen a lot more power out of them than that with Cobra 29's.

Next time I get a 148/Grant to mod up, I guess I'll have to take a video clip on the bench with the meter so people will believe it...

 

[Switch Kit]

Perfection tends to ruin this stuff for me at times sorry Nightrider , I kind of got technical with you a while back , I know your just having fun and your pleased. Sometimes I think IM just running out of mental gas with this stuff right when you think you know something somebody else will come around and complacate what I already thought I knew ? I think in the end ,it really shouldn't matter as long as the user is content , with a Dosy/Radio Shack / PDC / Bird or any other meter for that matter. This guy pats that guy on the back and that guy has no pats for the same guy , rms /pep/average this and average that . I hear what your saying Butch , I personal call them "ballpark" numbers , when it starts to sound like rocket science , it has away of draining my brain. I personally can deal with the keeping it simple approach and or if it works, don't fix it ! IM sure every one having anything to do with this thread means well , even Psycho I think most cb radio operators could really care less about what's really going on with the numbers game and are more then comfortable with the "ballpark pep" numbers then anything else. I'd have to say that more users then folks that take the time to truly understand all of this .could really care less about the Einstiens theroies of whats really going on underneath those radio covers, but when you hang around Forums like these , chances are your going to hear it ,one way or the other. That is the nature of the beast.