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gbowne1 23rd August 2006 01:11 PM

Ampilifier Project
I plan to put this amateur radio linear amplifier into good use in the 6m and 10 m amateur radio bands.

The bands are located at:

6m : 50MHz to 54MHz
10m : 26KHz to 29.7KHz. (Excluding the CB band within 26.965 and 27.405KHz)

Special precautions are going to have to be made so that it won't tune up in that CB band.. because it is illegal to cross-transmit to or from either band.

I plan to use a 19” wide by 12” high rack mount c

hassis.. and cool it with one or two fans sufficient enough to cool this amplifier. It should also not be built in a desktop chassis smaller than 11” wide x 7” high.

The original design was based on these two tubes.

Qty 3 each of 6JE6C (or it's direct substitution 6LQ6)
Qty 1 each of 6JG6A (which has a common substitution of 6KV6)

The output should be no more than 200W PEP due to legal restrictions in the 10m band.

It should contain the latest technology and standard parts. It should also not be capable of producing spurious signals into the CB or 10m amateur radio band, or any such emission over 200w, nor be capable of the same within the 11m Shortwave radio band from 25.6KHz to 26.1KHz.

It may be possible to provide plate, loading and tuning controls and any such controls with the appropriate level meters for each function.. as it also may be possible to provide a LCD display for such information.

I found good information on the two types of tubes used in the original design. People classify them as CB amplifier tubes, and TV Sweep tubes. The design is outdated and I hope to provide the same exact output level as these tubes do, but with different tube(s).

It should be sufficiently grounded, fused with an acceptable glass fuse, and have the power suppy be of sufficient rating that it provides good usage as well as being connected to 110-120v AC power via a disconnect-able computer power supply type AC power cord.

If someone could supply me with the information on a tube or tubes that work at the same output level that these two types produce in this combination, please let me know.

You can contact me though Yahoo! Instant Messanger as gbowne1 or you can email me through my Yahoo! Email account at

Gregory Bowne

DigitalJunkie 23rd August 2006 01:22 PM


10m : 26KHz to 29.7KHz. (Excluding the CB band within 26.965 and 27.405KHz)
I'm sure you mean Mhz,not Khz ;)

Hit up Google,there are *tons* of Amp projects online..

Also lots of projecs on the website.

Lots of tube info at:

And others.

Just be careful of the plate voltage. :att'n:

Tom Bavis 23rd August 2006 02:46 PM

You may wish to use 6GB5 (aka EL500), as there are recent production tubes for reasonable prices. 6JE6/6LQ6 has gotten rather rare and pricey... and can only get worse!

Tubelab_com 23rd August 2006 04:20 PM

When I used to build these things I used a 6146 for the driver and 6LW6's for the finals. The 6146 is a very common tube used in transmitters for a period of 30 years. They are still common and still being made in China.

The 6LW6 is the largest of the octal socket sweep tubes and puts out the most power. They like all sweep tubes are getting expensive, although nowhere as bad as the 6JE6C/6LQ6. The 26 and 36 volt versions are still cheap if you can find them.

There are a couple of sweep tubes still in production in Russia and China, which may be a lower cost alternative.

The sweep tube amplifiers that were common in the 1970's were often illegal CB amplifiers and had lousy performance. They created interference and ate up tubes quite often due to operating them at or above the maximum ratings. There were a few made "for amateur radio use only" that had a band switch (40 through 10 meters) but were capable of CB operation (on 10 meters). Amp Supply Company comes to mind. A lot of sweep tubes may be ineficient on 6 meters since they were designed to operate at 16 KHz.

I would look for copies of the old ARRL radio handbook which had construction projects in them using vacuum tubes. These amplifiers were designed by ham radio operators using tubes that were designed for RF service. The amplifier that you want could be built using a 4CX250B and the tube would last forever at 200W PEP. I don't remember seeing an amplifier that covered 6 and 10 meters, but I haven't looked through my old books in a long time.

gbowne1 23rd August 2006 09:01 PM

My quest is to really just replace the sweep tubes, doing away with them.

The 4CX250B.

I did see a long time ago a King CB amp which was modified by the factory for 6 and 10m. I decided on passing that one up.

I also looked in the book I have, and it lists the 8298, 8298A and the 7212 for substitues for the 6146 and it's variants.

Someone else suggested the 810 series Beam power Pentodes.
The 811A, 572B, 3-500Z, 4-400, 4CX150A, 4CX250B, 4CX800, 3CX1500, 3CX3000, 807

I also need info on the 12A?7 drivers.. (where ? is U, X or T) or using a 6CL6 or 5763 driver. I was concerned about not needing one.. Some sort of Hi-Mu Twin Triode with a 9A socket I would guess.

The 6CL6 is a power Pentode (subst 6677 and 6197) w/9BV base. The 5763 is a Beam power Pentode.

Anyhow thats the research I've done arleady.

gbowne1 26th August 2006 03:33 AM

I just bought a couple 6146's and a 4CX250B for this and future projects along with a surplus rackmount server case that could be used for a transmitter/transciever and amplifier project.


gbowne1 31st August 2006 05:20 AM

Not much done to this project yet. Still waiting on a few items to arrive.


gbowne1 10th October 2007 02:29 AM

Ok.. an update.. Kinda..

I now own a Eimac 8167 (4CX300A) and a RCA 6146 (not the A or B version) YFC.

Any ideas? suggestions?


w5jag 10th October 2007 03:23 AM

Well, before you get on 6 or 10 meters, you need a license.

6JE6C, 6LQ6, 6MJ6 and the like are not the best choice for an RF amplifier. They are fragile, have high inter electrode capacitances, and output will decline as frequency increases. They were once very popular in junky CB amplifiers because they were dirt cheap, but nowadays 6LQ6's will typically run you $25-30, hardly a bargain.

If you really want to use them anyway, it would only take one 6LQ6 to get 150 watts output at HF. I've never seen anyone use one at VHF, even low VHF like six meters. The old sweep tube CB amps that were nominally advertised as covering six meters, really wouldn't with any reasonable degree of efficiency. That was just a scam to sell them to the eleven meter crowd.

There is only 3 dB difference between 200 watts and 100 watts, and a pair of 6146 is rated to 175 MHz, and will do probably 80-90 watts at ten meters and a bit less on 6. There are a lot of other tubes in the 6146 family with different heater voltages, that are basically the same tube. I like the 6293 which is a much more rugged variant.

The 4cx250B was mentioned. A single one of these can do 500 watts PEP input well into VHF, but you will need a special socket, chimney for forced air cooling, and a lot of volts. 6LQ6 will probably need 900 volts, 6146 will take 750 to 900 volts, and tubes like 811A need about 1.8 to 2Kv. My 811A amp runs about 1800 volts unloaded. Even small RF tubes use very high voltages and peak currents relative to most audio amps.

Older ARRL handbooks are a good source of information, as are older copies of the late Bill Orr, W6SAI's, Radio Handbook.



gbowne1 10th October 2007 03:44 AM

I know about the liscencing requirements?

What about the 8167/4CX300A? On MW, 120m or 160m? FM (88-108)

The 6146/ YFC?

What about the sweep tubes on 10, 11m, CB?


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