New Modulation Transformer Available for Low Power AM TX

[KM1H]

After disasters with a Paragon and Orion I bought new Id never own a Ten Tec product again.

I get enough of their amps in here for service to know they are inferior to even Ameritron in most areas.

Copper and steel costs are a crock, they are far less in China and elsewhere that has the natural resources and/or processing ability. We are paying for over the top union wages, EPA, OHSHA, and envirowhacko lawsuits plus out of sight energy costs.

A modulation transformer can be built in a basement with a trained housewife getting part time wages. Im sure there are many areas with assemblers who used to work for small transformer companies. There are other ways to keep the cost low.

Carl

[W2WDX]

You're not serious Carl, are you? Is he joking with me; pulling my leg?

A housewife in basement part time? That's a joke right?

First off, I own a company. I have to pay at least minimum wages, pay for disability insurances, pay my share of FICA, get all the information Homeland Security requires now for hiring, and all the other things that go along with ownership and employees.

Hiring a slave lady to work down in my basement would not a good business plan make. How long would that last? Maybe I could hire some illegal aliens and chain them to the winding machines. Or maybe I could get child labor in India to make them work for me. Ooo ... I could get a bullwhip!!! Yeah !!! {CRACK} Work you dogs!!!  

Just so you could have your dream of a cheap modulation transformer. You are joking right?

Carl I can't take you seriously if you are gonna say things like that. And the price of copper IN THE USA is the highest it has ever been in history. Period. Take at look at this chart that goes back only to 1986. The price has risen 8 times over that period alone. 2009 was a good year though to buy.

http://en.wikipedia.org/wiki/File:Copper_Price_History_USD.png

And I looked up the price of copper for Feb 1959 as being at .24k in USD per metric ton (adjusted from US ton). More than a quarter of the price of 1986. Those are real numbers.

And BTW copper prices are paid globally and the markets do not differ that much from each other. So the idea that China pays that much less for it, or it costs more to buy here is ludicrous. It costs more to produce it here making the margin lower for the producers, the sell price is the same set by the exchanges. (An oversimplification maybe but close enough to reality.)

Don't just take a stance to be right. Please.

Anywho, the Sowter seems like FB. Considering nobody makes anything like it anyway. Seems to be well made, like Bear said. I wired it into a Ranger I have here and it works well. I have to sweep it to see what it really does though. Maybe it's something to consider for a future venture.

John

[W7TFO]

A good transformer is NOT an easy item to fabricate.  Steel, copper, punching presses, winders, all of it comes at a price and not something you can do on a bench by hand without some sort of support:  E&I stuff, forms, whatever.  The less of those things you have, the less professional the item is.

And a design.  That damn design.  You can cite impedance ratios all you want, but as Heinlein said, "The map is not the territory".

So-so ones abound, just look & listen to some in critical auditons.

It goes back to the guy getting $100 for slapping a TV set and having it work just fine...$1 for hitting it, $99 for knowing where & how...

A good, well designed and produced transformer is worth every penny.

73DG

[W2WDX]

Yup ... this is I meant by reinventing the wheel. Carl, you seem to have some intrinsic knowledge. Wanna come work in my basement? I have cookies!!!

[KM1H]

I wasnt commenting to you, its Bear that has the winder and all he needs to do is start a basement shop building small transformer runs. Others have done that and thrived if they are smart.

[WBear2GCR]

Yeah I do have the winders. Two. But when you look at the prices of the raw materials, the cores, the copper, the insulation, the screws, nuts, washers, insulators, paint, various goo compounds, tape, heatshrink, end bells, etc, then add in the labor costs, the taxes, the overheads it starts to look like a job that doesn't pay well until you get past a fairly high number of units sold! Then you go back around with the gov't carp that you have to deal with - even a 1099 to a legit subcontractor can be a nightmare. And TRY to find anyone who doesn't think that they should get $20/hr to "sweep ur floor". Find me someone PLEASE!!! Heck I'd pay someone to just clean the benches and restock parts!! Try to find that "part time person". Please.

I do know someone whose biz it is to wind custom audio things. He supports himself in his one man shop pretty well now. I think it took him over a decade to get to the point where he is on cruise control for that.

It just isn't an easy road to hoe, and unless you get the recipe right by accident, or "borrow it" or come with info from working for someone else first (there's another problem with hiring someone who is motivated and into the biz, vs. a "housewife" or other undocumented "worker") then ur going to spend a fair amount of time getting things right both from the mechanical construction part and the actual performance end.

Seems to me with the cost of copper now, ur going to blow through hundreds of dollars worth of wire before you make ur first *audio* transformer that is worth a darn. Power is probably going to be easier to get right.

Anyone who would like to run my winders, gimme a shout!

                          _-_-bear

[KM1H]

Well, that rewinder in ME takes old iron apart and even counts turns.

Id start with something small and cheap that is known good and start reverse engineering.
Nobody said it wont take time or be a labor of love at least in the beginning. Put on your work dress and apron and play housewife...its called R&D

Even do some rewinding for others to get a feel for the various designs.

I wish I had grabbed some of the gear when NH Transformer was liquidated when the owner died. He had a nice 4-5 person business doing mostly small runs and prototypes that the Magcaps, Merrimac Magnetics, and others didnt want to bother with.

[N4LTA]

Didn't mean to cause such a stir.

What decade did I come from?

 - The 50s when a TV cost 5 % of the annual income and today a 30" HDTV cost 1/2 weeks pay.


Souther ? A good quality British company  - typically British  - non inovative and only still in business because Audio Phools pay the inflated cost to make something that is out of date and non competitive with todays technology.

Hammond ( I know Hammond well and they are probably 85-90% as good as Souther and cost 1/3 the price Hammond is a transformer and sheet metal company - not a tube phoolery company - they make lots of good stuff and still sell the classic stuff more or less for nostalgia) I doubt that 2% of their business is tube iron.

The Hammond stuff does very well on the test bench but performs poorly in the Audiophool market because it doesn't cost enough.

And gee - Hammonds has very conservatively rated real copper wire and real silicone steel windings


Only problem that I have with an amplifier built with Hammond parts is that it has poor frequency response compared to a modern MOSFET amp that cost half as much - it sounds tubey - it sounds just like the Souter transformer amp - it has a colored frequency response exactly like the Marnatz and Mac amps of the late 50s and 60s that only the Doctors could afford.

If Hammond and Hoerborer can make a 50 watt output transformer that gets 50-18,000 Hz for $95  - I ain't paying $700 for one to get  5%  more frequecy response - especially when I can pay half the price for a MOSFET amp that I can use as a linear for the new Ham band.

But then - That's just me - Thats what decade that I am from - I have been Phooled more than once and built a whole lot of audio amps -  I like the tube sound but I hate the PHOOLERY and PHOOLERY  is rampant (in more than tube audio)

Pat
N4LTA

[KB2WIG]

" The Hammond stuff does very well on the test bench but performs poorly in the Audiophool market because it doesn't cost enough. "


Well, marketing would help......   Grab one of yer units, get some expensive, high quality paint and paint the  'bells' to a mirror finish. A bit o spagetti fer the leads and triple the price. And get someone who can write a gud review. Making up a few new words would be oh tay.  Look to see if there's a old term that doesn't get used and apply it to the Premium line.


klc

[KM1H]

Chrome plate the bells and jack the price $1000+

[KB2WIG]

'  Chrome plate the bells '

Doesn't chrome cause Cancer !!!???


The powder coat, ferrite laden (which keeps the flux inside, thereby improving the texture), envyronmentally $afe,  ~green~, socially conscious is much better than the deadley chrome (which makes the sound waves reflect off of the inside, which makes them beyonc around).

klc

[W3RSW]

As any good businessman can tell you, especially a proprietress of a one woman show, you only want your help to be so bright ...  Any more and the "valued employee" will simply learn all from you and start their own business.

Not counting all the regulatory hurdles, the greatest challenge in small business is walking the fine line between keeping employees good enough to be competent while keeping the poorer ones from tipping the till.    This ranges from outright cash register theft to highly maskable embezzlement.

[N4LTA]

Hammond already makes a modulation transformer of sorts



Rated at a very conservative 25 watts and 100 mA and weighs 6 pounds. Rated at 100hZ to 15kHz and will match 4 - 8 - 16 ohms from a solid state audio amp to 2500 -10,000 ohms.

If there was enough interest, Hammmond would probably put a tube push pull winding in place of the low impedance winding.


Sells for about $85 and it has all that expensive copper and steel that Souter gets $600 for


It really is a quality piece of iron. I will use one to modulate my 40 watt transmitter.

Pat
N4LTA

[W3RSW]

...as have generations to 'modulate' their 811's grids from a transistor PA or HI FI amplifier. 

[WD5JKO]

Here is the Edcor 25W single ended tube audio output transformer. This one is unusual in that it has a 600 ohm winding, and a teritiary tap for the screen grid.

http://www.edcorusa.com/p/475/cxse25-600-5k

So picture the Edcor in a Heising modulation scheme with the 600 ohm winding left unconnected. With the usual class A modulator, modulation is limited to about 80%, but a nice clean 80%. The transformer can take 200ma and not saturate at audio frequencies as low as 20HZ. So picture a B+ of 500V with a RF tube (6146) running 50 w DC input, or 100 ma plate current. Then for modulators use two EL-34's in parallel class A at 50 ma each. The total current will be 200 ma, RF input 50W, output about 35W carrier.

Now take that 600 ohm winding and phased properly, put it in series with the modulated B+. With a turns ratio of 2.9:1 the modulation capability will jump from around 80% to over 120%.

If it gets a little close to saturating, then just lessen the bass response to around 100 hz.

So here is another off the shelf modulation transformer for $83.50.  


Edit: The concept above of a single ended class A modulator runs 50W DC input, and with 50% efficiency puts out 25W to 100% modulate the 6146 which is also running 50W DC input. The modulator runs the tubes at maximum plate dissipation, and might not be capable of providing the peak modulation required to achieve 120% on peaks.

To overcome this limitation we could run the modulator class A2 with a cathode follower drive. This boosts the peak power ability of class A, and increases efficiency. Distortion can remain low so long as the audio drive is low impedance. Go a step further and use a sliding modulator bias (like the Brooks circuit). The following link analyzes the Brooks circuit, and then the author designs a sliding bias circuit for a single ended class A audio amplifier, called "Turbo SE". This could back off the modulator DC input from 50 watts to maybe 35 watts, yet with the sliding bias achieve over 40 watts audio. The circuit as at the end of the following link:

http://www.tubecad.com/2007/12/blog0128.htm


Jim
WD5JKO

[kb3ouk]

hmm, if you sat that hammond transformer up on some insulators, you might be able to pass a higher voltage through it, and for intermittent use, might handle twice their rated power. they have another single ended transformer that is rated at 75 watts. one could build a high power direct coupled solid state amp and feed it into the low impedence side of the transformer then hook the high impedence side to the RF final.

[W1VD]

In the old days (70's), Hammond would custom wind transformers for small quantity orders ... or make 'specials' available to hams when referenced in magazine or Handbook construction articles. Admittedly, that was when Fred Hammond VE3HC was running the show and you could call and talk with him directly. Not sure what their current stance is on small quantity production runs but it may be worth asking ... especially if it is generally a viable product to add to their line. Might help to mention the VE3HC museum http://www.hammondmuseumofradio.org during the call with it's early broadcasting, AM heritage, etc. An e mail to the museum curator may get a good contact name within the company rather than a 'standard' sales person. Hammond has experience in 'high' voltage ... I have a couple custom wound plate transformers 3500 V @ 2 amps ... big, heavy and quite 'stiff' under load. Ratings appear to be quite conservative.

   

[WD5JKO]

In the old days (70's), Hammond would custom wind transformers for small quantity orders ... or make 'specials' available to hams when referenced in magazine or Handbook construction articles.

Today Edcor provides this service, "EDCOR charges a $40.00 design and setup fee for quantities less than 10 pieces. We have a large database of designs going back over 30 years and if we already have the transformer on file then the design and setup fee is waived."

http://www.edcorusa.com/c/10/custom

As I've already posted here (post 39 this thread), they have some off the shelf stuff that might work out well if we design around one of their single ended tube offerings.

For sure Hammond makes good stuff but they are not the only choice out there.

Jim
WD5JKO

[N4LTA]

Hammond is still a good company but they charge quite a bit for custom work - They won't do it for $40 but they have generated  some goog stuff for Hams and radio enthusiasts. They have introduced an output transformer for the Collins military radios and some nice interstage transformers.

If there is enough interest for a general purpose modulation transformer 50-75 watts or whatever - let me know and I'll see what they will do.

Pat
N4LTA

[W2WDX]

You know what, I come from the "audiophoolery" market, having worked for Cary, Levinson & others over the years. The nosense in that industry drove me out of it. So I agree most people who buy this stuff prebuilt are nutz paying the prices they pay.

That being said, two transformer dominate the area of DIY tube amplifier parts suppliers. In Europe, it's seems Lundahl is the preference. In the US, Hammond dominates the field. Yes ... Hammond. The reason they can supply transformers cheaply is in economies of scale. The bulk of its business is in large industrial transformers and sheet metal work, not just little transformers for audio. So they have lower cost of manufacturing.

Now what we are talking about is a transformer designed specifically as a mod transformer, with a primary for P-P higher impedance plate connection and the proper lamination types. The Hammond you refer to will work well, IF it's connected to solid state audio amplifier. However for a standard type modulator in the classic scheme it's a no go.

Now to put down Sowter, because they are "british" and to say that the British are not innovative is a demonstration of a lack of understanding of the history of transformer design (and electronics in general). G.A.V. Sowter was a pioneer in transformer and magnetics starting in the 1920's and published many papers on the subject from the 1930's through the 1990's. His work on moving coil technologies, magnetic properties of soft metals, work on various nickel-iron alloys, Mumetal use, and applications of high-permeability magnetic alloys are considered benchmarks for transformer design. His call sign is G20S and designed numerous modulation transformers over the years. Good ones!

Sowter is a bit more expensive for two primary reasons. The cost of manufacturing in Britain is even higher than it is here, and two the difference between the Euro and the US dollar.

And as far as keeping employees out of learning everything and starting there own business? Make them sign an agreement stating they cannot do that! It's perfectly legal and enforceable, and it works most times. I can't build and sell tube audio amplifiers of certain types for another 6 years, because of working for one manufacturer I previously designed for.

However, we are talking about finding real NEW mod transformers, and not using trannys' designed for other applications and changing or limiting our designs to suit that. Like being limited to solid state modulators, not being able to connect to the plates of a tube audio amplifier output without jumping through hoops.

$700 for a prototype mod tranny sounds like they don't want to do it at all. Hey ... don't get me wrong, I love Hammond.

J

[WD5JKO]

Today Edcor provides this service, "EDCOR charges a $40.00 design and setup fee for quantities less than 10 pieces. We have a large database of designs going back over 30 years and if we already have the transformer on file then the design and setup fee is waived."
http://www.edcorusa.com/c/10/custom

  Loyalty to Hammond can get expensive.....

Has anyone talked to these folks about a push pull modulation transformer? The single ended Edcor I brought up earlier in this thread can handle 200ma whereas the Hammond only 100ma into the primary.

Jim
WD5JKO

[KM1H]

Denny found his dream niche when he started Cary.