audio driver transformer

[The Slab Bacon]

Just how DO you connect coax to a dipole?

With a connector!     Geeeeeeeezzzzzeeeeeeeeee! ! ! ! ! ! !        

[Steve - K4HX]

The forum header.

Technical Forum
 If you have questions, the answers are here!


Nothing about writing a handbook. We have a handbook section for longer articles, theory pieces and links to finished types of data. This forum is interactive - no one-way transmissions.

That said, I do not want to discourage questions here. Just consider consulting your handbook before posting. You'll likely be able to post more focused questions. These usually result in better answers.   

The purpose of this forum isn't to teach those fundamentals.

Says who?

[w1vtp]

Just how DO you connect coax to a dipole?

Use an iron like this. Works good on RG-58     Yeah, I know, the photo's a repeat from another post.  Couldn't pass this up

[W2VW]

Why not jusy buy an antenna?

[KM1H]

Good explainations. Dennis does have a point. All this is covered in the handbooks in the 50's and 60's. If you don't have one, get one (or two). If you have one, read it. These sorts of topics are covered in far more depth than we can here. Who has the time to type pages and pages of text, except for Don.

   

Discouraging comments as found on here is what drives noobies away to the CB pits of Eham and QRZ where they learn to do things that then get them hollered at on the air by the expert snobs on here

What is really lacking on here is for those with time on their hands to add to and clean up the "Technical Info" archives.

Carl

[W8ACR]

OK guys, back on topic

I took a second look at the placard on the transformer, and I read it wrong. I thought it said primary impedance 10000 ohms, secondary 2500 ohms, impedance ratio 4:1.

In reality it says primary impedance 40000 ohms, secondary impedance 2500 ohms, turns ratio P:S=4:1. The math works.

NOW what do you think is the application for this transformer Does anybody think I could use this to drive a pair of class B modulators??

Ron

[W7TFO]

40K primary is very unusual, especially with only 20 Watts throughput.

If it were 200 Watts, I'd say it would be happy with a pair of 100TH or clones.

Got me.

73DG

[The Slab Bacon]

An easy test to find out for sure what the turns ratio is is simple:

Put 120vac (or whatever amount of AC voltage you are comfortable with) on the primary, and measure what you have on the secondary. With a little division this will tell you exactly what the turns ratio is. Simple as that. Also check the taps and windings for symmetry while you are at it, this will give you an idea if you have shorted windings or turns. No special test equipment needed exvept for some clip leads and a multimeter.

[Opcom]

OK guys, back on topic

In reality it says primary impedance 40000 ohms, secondary impedance 2500 ohms, turns ratio P:S=4:1. The math works.

Ron

Use it for whatever tubes will make 20W at that impedance but that means a high voltage/low current tube. What is the voltage rating on it? Is it really a general purpose audio transformer or maybe for some other application?

What happens to the power output when using 40K CT on a pair of 6L6's @360V instead of 5.6K CT? Not the usual 55W, but much less like 7 watts. 

How about a pair of 6CA7's at 800V which normally make 100W into 11K? That kind of plate voltage swing would get closer to 20W. (807's anyone?)

I'm just looking at the tube manuals and calculating the plate to plate RMS voltage, then taking that across the 'new' 40K Ohm load. Granted those tubes would handle way more current than a 40K load could draw. haha maybe 6BQ6's would be more fitting as they would take the high voltage and could supply enough current.

It sure is a puzzling transformer. Why not drag out an audio amp and experiment to see of it will do what you want!

(BTW never pay attention to what I write as I am seldom on the air.)

[W7TFO]

(BTW never pay attention to what I write as I am seldom on the air.)

That makes two of us...

Maybe try a pair of 15E triodes...mega high plate impedance.

73DG

[W8ACR]

Hi Patrick,

The voltage rating is 5KW. This is a really old transformer, my guess would be 1930's or 40's at the latest.

Ron

[Opcom]

Ron,

you could use almost any HV-rated tubes then, and a slightly higher plate voltage would make for an easier match. 20W into 40K Ohm is only 22mA and 895V RMS. With available tubes, the only real challenge is the plate voltage swing. That is why I suggested tubes that could take higher voltages like 800V+

I know I suggested tetrodes or beam tubes, but if using it for as a driver to a class-B stage then it might be a good job for some small high voltage triodes (unless a bunch of feedback is used on the tetrodes to lower the output impedance). The 15E is a beautiful tube (and a heater-hog! ).

How about Eimac 25T's or 35's? 3C24.. any smallish HV tubes. 25's and 35's show up cheap sometimes as few people want to use them.