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Davec
Posted on Sunday, October 19, 2003 - 7:48 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

I'm want to buy a base amp for a Galaxy 2547. I've been looking at the KLV400. All the locals are trying to talk me into a Davemade M-80. They all prefer transistors to the KLV tubes. Whats the big deal with tubes? I know they burn out over time and transistors don't? I don't know.
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307
Posted on Sunday, October 19, 2003 - 1:56 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Tubes are much more efficient and produce much less TVI , They are cheaper to fix as well.

307
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Tech671
Posted on Sunday, October 19, 2003 - 6:28 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Make sure using the KLV400 that you adjust radio power so the amplifier's AM carrier is 80-100w. All should be well and the KLV will run more neighbor friendly than the X80.
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Kf4gyp
New member
Username: Kf4gyp

Post Number: 1
Registered: 11-2009
Posted on Sunday, November 29, 2009 - 4:52 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

I am not a big fan of tubes because you need high voltage & low voltage high current supply voltages.Now warm up times on tubes can take longer than just flipping a switch. that is not all if you do not tune it properley into the load you can destroy the tube plates in seconds. this being said along with the filiments generating heat just to sit in stand by mode and do nothing until you ready to pull off of stand by. transister types can be put in service at will do not produce heat when not active and are way more effiecient per watt generated. ooooppppps got a bit winded sorry!

73 Ray
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Tech833
Moderator
Username: Tech833

Post Number: 1793
Registered: 8-2002
Posted on Sunday, November 29, 2009 - 8:37 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

For the record, tube amplifiers are more efficient than transistor types. A typical tube type amplifier runs close to 80% PA efficiency while transistor amps have yet to break the 60% mark.

Tubes are much more forgiving of mismatch and clumsiness. Tubes will withstand overload conditions for a long time before they fail. They will glow red to indicate a problem and give the operator time to notice the problem and take corrective measures. If the tubes do fail, replacement is inexpensive and easy (plug in). Transistors burn up in a fraction of a second in an overload situation, then they're toast. Repairs are very costly, usually more than replacing the entire unit. Replacing transistors requires soldering and some know-how.

True, operating a tube amplifier does require a little more thought process. But most people are smart enough to handle it, no problem. Just tune for minimum plate current and maximum grid current, and away you go. If someone cannot handle that simple task, they have no business running ANY kind of amplifier.

Transistor amps are more convenient when mobile, and are preferred for the no-tune feature. This is why you see so many mobile solid state amplifiers on the market. When on the base station, a tube amplifier is so much more reliable and cost efficient over the long run. Also, tube amplifiers are a lot less prone to causing intermod and spurious type TVI than transistor amps. Not a big consideration when mobile, but a major concern for the base station, particularly those with neighbors.

Admittedly, solid state RF amplifier technology is improving. But, as of this writing, tube amplfiers still have the advantage.

Your radio 'Mythbuster' since 1998
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Bruce
Senior Member
Username: Bruce

Post Number: 5247
Registered: 9-2003
Posted on Monday, November 30, 2009 - 12:17 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

TUBES ?

Under 500 watts Transistors work just fine ....

You don't see trunking system amps using TUBES ...

OVER 500 watts 811's, 572B's are still good choices

My last tube amp was a 4cx250 push-pull amp for 144 mhz that was 40 years ago .....
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Tech833
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Username: Tech833

Post Number: 1794
Registered: 8-2002
Posted on Monday, November 30, 2009 - 10:06 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

You don't see trunking system amps use tubes for many reasons. The most important is that tubes that operate in the UHF and above spectrum are very expensive. Also, linearity is important, and a class A or AB amp is more expensive and less efficient using two expensive UHF tubes than it is to use high frequency silicon devices. I was only referring to class C HF amplifiers.

I never said transistor amps don't work, or work well. I was dispelling the claims made earlier that tube amps are more easily destroyed by poor operating practices and not as efficient as transistor amplifiers. I also gave examples to illustrate my reasons.

Your radio 'Mythbuster' since 1998
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Bruce
Senior Member
Username: Bruce

Post Number: 5248
Registered: 9-2003
Posted on Monday, November 30, 2009 - 11:28 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

IF you take the time to do a good job of building a transistor amp RIGHT ...UNLIKE MFJ did on my 2 meter amp WHICH BURNED UP AT 50% of its output rating with a fan blowing on the heat sink....

I would not even think of tubes under 500 watts.

I ran 829B, 807 and 1625 tubes until the early 70's on 6 meters and 4cx250b's, 829B and 6146 until the mid 70's then went with transistors.

BOTH are durable and unless again a MFJ poor design causes failures BOTH will withstand abuse

YES TUBES will give you some warning like we use to say you know the 829B is running at full output when you see the white grid through the red hot plate .... and in this case a tube will give you a 2nd chance ...... but well thought out transistor amps can too some I have run got VERY hot .....

[Name-calling removed]
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Norm
Junior Member
Username: Norm

Post Number: 32
Registered: 9-2002
Posted on Monday, December 28, 2009 - 12:31 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

I AM WITH TECH 833 THERE IS NUTHING LIKE 2 500Z HERE KETTY KETTY BLACK CAT 2000.
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Kf4gyp
New member
Username: Kf4gyp

Post Number: 4
Registered: 11-2009
Posted on Wednesday, December 30, 2009 - 11:57 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

ok then let us test this theroy. have both transistor and tube type devices sit on stadby mode and power applied ready for service for years on end. come back 15 years later (exagerated for point) and force devices to work at only 10% of rated output no tube filament will last all day every day for 15 years with no breaks. transistors will.my reason for the trasistor is if it is never allowed to exceed the design parimeters it will out last us all. tubes on the other hand wont
and tubes are not cheaper per watt. the device i would like you to study now is a mosfet device arf1500. now this is where efficient operation is going to come from. dont get me wrong tubes do have thier place. (hopefully never) ever there is atomic bomb detonation the only thing in that area that will work is tube type equipment. but under normal situations fet,mosfet & bipolar devices will out last a tube only because of filament life. heck there are still bipolar devices still operating that was made in the late 50's. question is how long does sand,rocks,mountains last? i think they will still be here after the earth has done away with the human race. by the way silicon is sand right? man this fun talking with like minded people. sides look at the time i put this post up.
here is a good link www.triadaudio.net/Triad_Audio/Downloads_files/Tubes_or_Transistors.pdf,

good night73
Ray
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Tech833
Moderator
Username: Tech833

Post Number: 1802
Registered: 8-2002
Posted on Friday, January 01, 2010 - 1:31 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Tube equipment is less expensive per watt when you take the entire unit, including power supply, into consideration.

Leaving tube and transistor amps in standby for years is not a good comparison as nobody would do that. You would use your gear, not just look at it in standby mode for years.

There are no high power solid state SW transmitters in production today because the cost per watt is way too high. There are some mid power (50 KW) transmitters made that are solid state, but they cost nearly twice as much as a tube type. And, when they fail, it sometimes costs 10x as much to repair.

Your radio 'Mythbuster' since 1998
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Norm
Junior Member
Username: Norm

Post Number: 33
Registered: 9-2002
Posted on Friday, January 01, 2010 - 11:15 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

THANK YOU THANK YOU TECK833
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Kf4gyp
New member
Username: Kf4gyp

Post Number: 7
Registered: 11-2009
Posted on Friday, January 29, 2010 - 9:39 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Hi Guys
If that leaving both types of amps switched on for years was not done explain am transmiters on the am broadcast bands they had too as well as fm band. there are both required by the fcc to stay on the air 24/7 for emergency reasons. The cost of operation of a tube is more expensive to keep on the air than tubes. The reacurring cost of tube power consumption heat generation and tube replacement would vs transistors makes the transistor cheaper in the long run to maintain and operate. The thing with transistors is it will operate all day every day so long as the design parameters are not exceeded. I ask you to ask a hi power station (broadcast)transmitter engineer what he replaces the most the tube final pa or the exciter transistors. NOW in favor of the tubes I do like the frequencies they can cover after all radar was based on tubes back in the 1940,s and 50,s heck microwave ovens still use electron tubes to provide radiation to heat our foods at around 2.2-2.5 ghz and last years doing that because they are on and off. Mostly off though!(Grin)

Tech on another note maybe our enjoyable and respectful coraspondane on this subject with one another will be intresting to read to some of the other members on the forum.I belive that is why we as well have our on choices. and i do apperceate all of the opinions you and others have on all subjects of radio! Just saying thank you.

73 Ray/Hawk Eye/KF4GYP
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Tech833
Intermediate Member
Username: Tech833

Post Number: 134
Registered: 12-2001
Posted on Friday, January 29, 2010 - 9:08 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Hi Ray.

It was a little difficult to decipher your post, but I think I see what you are trying to say.

It so happens, that I am a broadcast engineer (Chief Engineer of 12 radio stations right now), half of them are high power. I think I can answer your questions accurately.

First of all, almost all the medium and high power transmitters for FM are still tube type. They are MUCH less expensive to run than solid state. For instance, I have a Harris Z-10 solid state 10 KW transmitter at one site that seems to lose a PA module about twice a year. The pallets to rebuild the modules cost $1200 per module. So, I am spending close to $2400.00 per year JUST on PA modules. That doesn't include other failures. The solid state transmitters have more frequent failures than the tube transmitters.

I have a 10 KW tube transmitter at another site that uses a single PA tube. it costs $980.00 to rebuild that tube. A rebuilt tube lasts almost 2 years. So, I am spending about $490.00 per year for the PA of the tube transmitter. Admittedly, the solid state transmitter has SLIGHTLY higher overall efficiency (power input to RF output) than the tube transmitter, so it takes less power to keep it on the air 24/7. But the power savings does not cover the repair and upkeep costs.

Solid state gear has its place, no denying that! But, don't count tube gear out just yet. it is still the way to go in some applications.

Your radio 'Mythbuster' since 1998
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Ec158
Junior Member
Username: Ec158

Post Number: 10
Registered: 6-2008
Posted on Thursday, March 25, 2010 - 7:21 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Definately TUBES!

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