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Wolverine
| | Posted on Wednesday, February 19, 2003 - 10:00 am: | 
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What is the difference between a sweep tube and a transmitting tube for Ac base or mobile amps? I do remember that sweep tubes were for tv sets, like the 6lf6 tubes. Also, what are the new designations for the tubes used in Ac sky competition shootouts. Thanks in advance. |
bruce
| | Posted on Wednesday, February 19, 2003 - 11:35 am: |
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NONE the sweeptube may not be as linear but they work almost the same. Many very old tubes are just as good now as then many old timers on 6 and 2 meters remember the 1625/807 or the 829B still a good tube for a 100 watt amp. Some new ceramic tubes produce very high power for the size but the design for most goes back 30 years or more... 4x150 50 years! In short their is a wide selection myself i have a amp with 3 811's but dont use it i picked it because that tube goes back 60 years and is STILL made! |
Wolverine
| | Posted on Thursday, February 20, 2003 - 3:29 am: |
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Thanks Bruce, I have 8 years of catching up to do,
and I'm trying to re-learn all I can as fast as I can. I'm surprised that in amp shoot-outs at various CB breaks, such as th Ac sky class (Sky is the limit for tube watts generated), that most people aren't afraid of the high-voltages involved. What ever tube designations that are being used, they all must be experts, and not neo-phytes. |
2600
| | Posted on Friday, February 21, 2003 - 12:21 am: |
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A "sweep" tube is a RECEIVING tube. The power that it can handle is limited by how hot it can get without damage. When the TV factories were gobbling millions of sweep tubes to build televisions, they were cheap, like anything else that gets made by the million. A 30-Watt sweep tube in 1975 cost around $6.00. That's twenty cents a watt. That 30-Watt rating is for near-continuous duty inside the family television. RF amplifiers routinely pump twice the rated power to a 'sweep' tube. So long as the key-down time is short enough, and the standby time is long enough, it doesn't get hot enough to be damaged. Figured this way, it's more like 10 cents a watt. In 1975, a 4CX250 transmitting tube cost around $150 each. That's more like 60 cents a watt. Sixty cents or ten cents? It's easy to see why 'sweep' tubes got used to build price-sensitive toys like RF amplifiers.
Fast-Forward to the year 2003. The same 30 (60?) Watt sweep tube now costs, maybe, $60.00. A dollar a watt. The same 250-Watt transmitting tube is now around $150.00. Sixty cents a watt sounded high in 1975. Now it sounds cheap. What had been the expensive option back then is the cheaper one now.
73 |
bruce
| | Posted on Friday, February 21, 2003 - 8:41 am: |
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Even though the " sweeptube " was not developed for transmitting service it is not a true reciving tube its a power tube. The 6JB6 was widely used i used many of them in my drake line the tube is a pentode power tube ment as a driver for the flyback in a tv set but EXCEPT for lower temperure will preform just fine as a mid power transmitting tube and at that time FAR cheaper. I ran 3 4cx250b in parral for my 1000 watt 6 meter deck and 2 in push pull for 2 meter moonbounce this is not the same type of tube the external anode tube were air cooled and set up to run at high temp far higher than any TV set would ever run at. For the average joe radio user either will work just fine although i discurage using tubes in amps below 200 watts since transistors are just as good and now just as cheep or cheeper. Even the old standards are fast going away ..... 807's 1625's 6146's and the vhf work horse 829b are almost never seen today no reason to use them when a pill the size of a poptop will put out more and do it at 12 volts! |
CM 3885
| | Posted on Saturday, February 22, 2003 - 3:24 pm: |
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Transistor amps are "dirtier" than tubes. and besides tubes talk better than transistors! The best tube amps to run are the ones that use the ceramic tubes. |
Wolverine
| | Posted on Sunday, February 23, 2003 - 8:44 pm: |
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Well, if sweep tubes are recieving, what do they call The tubes used in AC sky shoot-outs, or keydowns now?? Xmit, or Directing? I prefer Transistor amps any day dirty or not. Their safer used in mobile applications, and I don't have to re-tune them when I change the freqency. Now, if I had a "Base" set-up, ignore all of my previous comments . |
bruce
| | Posted on Sunday, February 23, 2003 - 9:37 pm: |
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Transistor amps are NOT dirty if they were you could not make them for comercal use. Now the limit seems to be about 500 watts where tubes pull away as far as proformance but in most 100-200 watt radios tubes have no real advangage. I dont use tubes anymore except for one amp. All my HF/VHF/UHF radios are solid state. I grew up on tubes went to rech school in the 60's and used them till the late 90's but today except for old times sake not for me! |
Txdx
| | Posted on Monday, February 24, 2003 - 5:40 am: |
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Transistor amps are NOT dirty when built correctly.Sorry Bruce a lot of the transistor amps out there are very dirty.BIASING are the lack of biasing I should say.There is a big difference in clean output between an AB biased amp and a C.
SPURIOUS EMISSIONS
Comp amps and clipped radios are the usual culprets for bleeding 10 channels across 2000 miles.Just my 2 cents.73s everyone. |
2600
| | Posted on Monday, February 24, 2003 - 11:26 am: |
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Hmmm, he did say "AC Sky". At around 100 Watts PEP per 'sweep' tube, it would take scores of them to compete with that crowd. There are technical barriers to wiring more than 6 or 8 of those together at once.
It's a flat-out arms race with those guys. A few years ago, one or two 3CX3000 tubes made you a big dog in that division. Lately, the 5000-Watt and 10,000-Watt size tubes are what the rumors describe among the top dogs in "AC Sky" competition. Funny, the ones who keep winning are the most shy about showing just what is 'under the hood', so rumors abound, and facts are scarce. www.bigradios.com had the most up-to-date pictures and shootout results a year or so ago. Haven't checked them for a while now.
73 |
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