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Dc vs AC

This section is about Keydown Competition rigs or high performance competition base setups. If you have questions or information on how to maximize a competition setup, this is the place !

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bayou1
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Dc vs AC

Post by bayou1 » Sunday, 11 January 2015, 21:22 PM

Scenario = 2 comp trucks setup to do 5k output. Both using bounce back equally tuned. 1 is a AC truck and the other is DC truck. Who has the advantage? And why do you expect your choice to win?
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Re: Dc vs AC

Post by 543FtWorth » Monday, 12 January 2015, 6:00 AM

If both are producing a clean 5k they are equal. The output circuit in a tube amp makes it cleaner by nature.

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Re: Dc vs AC

Post by MDYoungblood » Monday, 12 January 2015, 6:31 AM

If they are equal than that is the answer, irregularities would be the only thing to make a difference.

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Re: Dc vs AC

Post by jessejamesdallas » Monday, 12 January 2015, 8:06 AM

Person with the better antenna set up will win... (antenna spacing, coax, jumper lengths)
And who can hold the volts the longest!
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Re: Dc vs AC

Post by TheCBDoctor » Monday, 12 January 2015, 9:59 AM

jessejamesdallas wrote:Person with the better antenna set up will win... (antenna spacing, coax, jumper lengths)
And who can hold the volts the longest!
543FtWorth and jessejamesdallas has it right. 5K is 5K no matter if you are using AC or DC. DC may be cleaner if you get any noise on AC since the source voltage on AC may produce a 60 hertz hum. You do not need as many batteries when using AC (Advantage considering the cost of a deep cycle battery). The alternator on AC will cost more than the one needed for DC. Also on DC your voltage may drop after a long key-down; this reduces your output.

The antenna system is what makes the difference on any radio system if all things are equal (5K is 5K).

Just my humble 2 cents,

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Re: Dc vs AC

Post by bayou1 » Wednesday, 14 January 2015, 7:25 AM

Tks for the input. I have heard some say dc had a advantage and others say Ac. A watt is a watt to me.
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Re: Dc vs AC

Post by yota167 » Thursday, 15 January 2015, 11:37 AM

Cool post. Is that 60hrtz the hum I hear in the background that sounds like a fan running in the background when a big tube base keys? I've not listened to the lower tones as I don't use them to tune radios...
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Re: Dc vs AC

Post by TheCBDoctor » Thursday, 15 January 2015, 12:17 PM

bayou1 wrote:Tks for the input. I have heard some say dc had a advantage and others say Ac. A watt is a watt to me.
Good afternoon bayou1,

On AM the efficiency is only 25%, so a watt is really 1/4 of a watt. Those that run DC say DC has the advantage, while those that use AC say AC has an advantage. It is really 6 of one and a half dozen of the other. I am not into "Key-Downs" They really don't prove what radio is better. If I can speak into a Mic and the other station can hear me the first time, then my radio and antenna system is working.

Power is measured in dbm. That means you must double your output in watts to give another station 1 "S" unit. The truth is no one can tell the difference between an "S" unit of 6 and an "S" unit of 7. Commercial radios do not have a receive meter for a reason. They are useless. Only CBers rely on the receive meter, and that is because it is just another gadget to look at. I can adjust the receive meter to read whatever I wish. So what makes them so practical? It helps the novice see that there is a receive signal. It doesn't mean what you are seeing is what you are getting.

When I need to see if a radio is receiving and at what sensitivity, I use my test equipment.

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Re: Dc vs AC

Post by ogdoa » Thursday, 15 January 2015, 13:42 PM

Hate to disagree but the meters on the front of radios do have a few other purposes then just being a gadget. I remember playing fox hunt when I was younger. It will also help when dialing things in. If you have a friend that you normally hit with a 6 and you make some improvements then you hit him with a 7...you know they worked. A lot of the meters and test equipment is about as accurate as the meter in a radio. Dosy watt meters come to mind. It is all relative. I use my radio swr meter and my external meters to tell me if something is going wrong. I know they are not accurate but if they move....I know something is wrong and I can fix it before something gets damaged. With commercial equipment, they have to run it until something breaks unless they have a tech checking it every day.
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Re: Dc vs AC

Post by barney33 » Sunday, 19 March 2017, 9:00 AM

An AC amp can electrocute someone who is not careful while a DC amp can't.

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Re: Dc vs AC

Post by 443 Arizona » Monday, 20 March 2017, 9:56 AM

as for the original question, DC is the answer.
and as applied to the "scenario", the truck becomes a better DC ground which increases field strength.
also,my reasoning is that AC is always trying to be DC , :cyclopsani:
i might be a bit biased(pun :lol: )

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Re: Dc vs AC

Post by 543FtWorth » Monday, 20 March 2017, 10:21 AM

Tubes and transistors both require a dc power supply.

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Re: Dc vs AC

Post by MDYoungblood » Thursday, 23 March 2017, 6:54 AM

AC or DC,, both can be a shocking experience,
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Re: Dc vs AC

Post by Crusher » Sunday, 26 March 2017, 6:30 AM

Antennas first along with proper coax. Transistor mobile. If you are relying on batteries to hold system. You will start to drop off at end. Tube box, may take a few seconds to build up DC if the engine ain't full bore at beginning of key. Also I think it's closer to 300-400hz for 3ph alternator. Have to spend a bit more on proper regulator for AC mobile. If you don't know what you are doing, you can die quickly. Also if your not tech savvy when it comes to tube box. If something blows, you are at mercy of someone that is to repair your stuff. Meaning possible added cost down road. On transistor stuff make sure you have like 50% more alternator than you need. Remember as they heat up, current drops. Good alternators should have some kind of temp chart showing differences. If your gonna do it. Do it right first time. Don't try to save a buck. You will end up spending twice as much in end. I know. Lol.

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Re: Dc vs AC

Post by nk14zp » Sunday, 26 March 2017, 15:17 PM

543FtWorth wrote:
Monday, 20 March 2017, 10:21 AM
Tubes and transistors both require a dc power supply.
Yep in the end they all run of dc and your alt produces ac.

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Re: Dc vs AC

Post by Crusher » Thursday, 13 April 2017, 17:48 PM

Yup, but if you don't know what your doing. Better stick with transistors. Low voltage. The tube stuff depending how you regulate voltage could have 5000v or even 7000v or more. No room for mistakes

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