6146 plate modulator

[KA4RFA]

Does anybody have a circuit to plate modulate a single 6146 using
a readily available low power mod transformer and other associated mod parts?

I don't have the iron to do it right so going to plate modulate the driver stage.

JIM -- KA4RFA

 

[Pete, WA2CWA]

Why don't you screen or cathode modulate the 6146?

[WQ9E]

Jim,

Readily available and mod transformer don't really fit together in the same sentence anymore.  If you are set on a single 6146 or similar keep an eye out for parts rigs to provide the components.  Rangers don't seem to be parted out much but maybe something like a Multi-Elmac AF-67/68 or Harvey Wells TBS-50 (807 final but same basic power) might be easier to find.

Otherwise, since a single 6146 is pretty low power (especially for conditions on 160 and 80), think about going with controlled carrier AM like that used in Drake, smaller Heathkit, and Knightkit transmitters.   The duty cycle of these is very compatible with modern linear amplifiers when you need more signal.

[Steve - WB3HUZ]

Any ARRL Handbook from the 50's and 60's.


Or here

http://www.amwindow.org/tech/htm/rangmod.htm

Or here

http://www.amwindow.org/tech/htm/ranger.htm

[KA2DZT]

Does anybody have a circuit to plate modulate a single 6146 using
a readily available low power mod transformer and other associated mod parts?

I don't have the iron to do it right so going to plate modulate the driver stage.

JIM -- KA4RFA

 

I'm an expert on modulating a single 6146.

Fred

[KA8WTK]

Also, here

http://www.amwindow.org/tech/htm/tvtomod.htm

[The Slab Bacon]

Or take a beefy audio outpoot transformer. (something way bigger than what you think you need) Hook the primary end leads to the plates of a pair of 6L6s (or something similar) Hook the center tap to your B+ supply. Then tie one of the primary end leads to the plate of the 6146 (and the modulator plate as well)
Do not hook anything to the speaker output leads. This is kind of a kluged up autotransformer arrangement, but it can work quite well if you have a good transformer to work with.

                                                     The Slab Bacon

[KE6DF]

Maybe instead of going thru all the work for a single 6146, try a pair of 6146s or a 4D32 or something that approaches 100W out. Probably wouldn't cost that much more to build.

[K5IIA]

not sure exactly what you are looking for audio wise. but you can pickup a single ended hammond audio transformer cheap and modulate it with a small pa amplifier.

[KM1H]

If this is the same question you asked elsewhere that is way too much tube to drive a grid driven 4-400A linear.

[w1vtp]

Maybe instead of going thru all the work for a single 6146, try a pair of 6146s or a 4D32 or something that approaches 100W out. Probably wouldn't cost that much more to build.

I have several single 6146 mod iron Xfmrs I have collected over the years.  That size mod iron is much easier and cheaper to get (especially over eBay) because of the desireability of modulating 2 6146's.  If you have a good ant.. your goal of a single 6146 will work very well.  You should run into a 30-40 watt class mod iron a lot sooner than a 100 watter and cheaper too 'cause most HB'ers want the bigger iron.  I'd just put on a saved search for "modulation transformer" and bid low on 30 - 40 watt mod irons.  Bet you score fairly soon. You need to have a basic collection of Stancor, UTC, Triad, Thordarson, Chicago catalogs so you know when you have a winner.  One of my scores was a rather obscure model that turned out to be a 40 watter.  A quick look in my catalog collection verified what the Xfmr was.

Steve's answer is to the point as far as a schem..

GL, Al VTP

[WU2D]

The old TCS mod iron is a 1:1 6000 Ohm job and it is in that same class.

[w4bfs]

you might take a look at the discussions from a year or two ago about using toroidal lv power transformers hooked up backwards and driven by a solid state audio power amp ... these 25VA units are still available from Epay in the $20 range and sound really good on the air

[N0WEK]

Looking at the original post, Jim isn't trying to do low power AM, he's trying to modulate a driver stage instead of plate modulating the final.

[The Slab Bacon]

Looking at the original post, Jim isn't trying to do low power AM, he's trying to modulate a driver stage instead of plate modulating the final.

It looks like he wants to mod the driver before feeding it into an amplifier (leanyour)
In such case, it would still be the same application as modding a final amplifier, just done on a smaller scale.

Since most leanyours only need around 10-15w of drive for full outpoot, He might me able to scale it down even further and use something like a 2E26 modded by a pair of 6V6s.
Or something similar to make the reduced output needed for the amp. This way he would only need something like a 10-15w mod tranny which should be easy to find and cheap when found.

If he wanted to apply a little shake to the driver stage feeding a modulated class C final
this would be another scenario alltogether.

[KM1H]

Thats what I suggested on another forum; a 6146 was serious overkill. He wants to use a 4-400 linear which only requires 2-4W in a tuned grid drive. Thats in the 5763 class with a couple of loafing 6AQ5's for audio. I also suggested a cathode modulator on the 4-400. However he has been silent for a few days.

A 6N2 T-bolt can be run to full power with 2-3W and a bit more for NCL-2000 with a swamped grid input. Tetrodes have lots of gain.

[N4LTA]

Jim

I 'd use the smaller tube - 2E26 - and modulate it with a Hammond 125ESE which is good for about 80 Ma plate current. It has multiple matching and is a good quality transformer. You probably coul dget by with a 125CSE but the price for the larger one is not that much more.

You can use a small high quality solid state amp to provide the drive - I use the National class D chipamp - LM1875 or the larger one. You can get the board from Chipamp for pretty cheap. I use them to modulate a 6L6 transmitter with a 125ESE  and as my station monitor. They sound great and go up to 60 watts with a higher voltage supply.

Pat
N4LTA

[w1vtp]

Jim

I 'd use the smaller tube - 2E26 - and modulate it with a Hammond 125ESE which is good for about 80 Ma plate current. It has multiple matching and is a good quality transformer. You probably coul dget by with a 125CSE but the price for the larger one is not that much more.

You can use a small high quality solid state amp to provide the drive - I use the National class D chipamp - LM1875 or the larger one. You can get the board from Chipamp for pretty cheap. I use them to modulate a 6L6 transmitter with a 125ESE  and as my station monitor. They sound great and go up to 60 watts with a higher voltage supply.

Pat
N4LTA

I tried this approach and put up a thread on it

http://amfone.net/Amforum/index.php?topic=16771.0

The PDF includes the setup for the AM tests and results including THD test results (good) and freq response (good)

Gl Al