New Modulation Transformer Available for Low Power AM TX

[W2WDX]

I just took delivery of a Modulation Transformer still being made. It seems it would work well for a transmitter with a 30w-40w P-P modulator like a Pair of 6L6's. It is in current production by Sowter in the UK. It is a bit pricey though, especially with US dollar where it is right now.

Impedance 5k to 5k pri/sec, 200ma sec, 1500vp-p voltage on sec

It may be a good candidate as a replacement for mod iron in several of the older boatanchors using a single 6146 or 2e26 like Ranger's, Globe Scout 680, and others. Or you could use it build a modulator for a Heath DX-35, DX-40, Eico 730 or others. Not to mention homebrewing small AM transmitters, like something using a Pair of 6L6 modulating a 6146.

Here's the link:

http://www.sowter.co.uk/acatalog/SOWTER_TRANSFORMERS_SINGLE_ENDED_OUTPUT_17.html#a317

and another with more data:

http://www.sowter.co.uk/single-ended-output-transformers.php

[BrianBurnsSWL]

In a thread from 2008. Stu--AB2EZ-- mentioned AnTek Inc. as a source for a toroidal modulation transformer which he used with good results on his Viking Ranger, followed by a couple more AnTek toroidal transformers that he bought for modulating a high power rig. Search on AnTek, and the thread will come up about third.

I had a look at AnTek's toroidal power transformer line, and they were very robust indeed, and about 15% less expensive than the nearest Hammond equivalent.

Anybody else have any experience with AnTek's products as modulation transformers?

Cheers,

Brian

[W2WDX]

Actually I have. My company has been working on a prototype plate modulated "boatanchor" type transmitter using a DDS VFO (80m-10m) and all tube design. With solid state regulated supplies having separate supplies for Fils, Bias, Mod B+, PA B+, & other low voltages. This is for new manufacture, hopefully to begin production & distribution sometime in early 2013.

We are modulating a 6146 with a PP pair of 6L6's and use an Antek Toroidal for the mod tranny. The same setup can have increased output by adding another 6146, increasing the output of the modulator (which is dialed back right now running lower plate voltage) and changing the mod tranny.

We swept the radio and it has a flat audio response on the output of 60hz-11kHz. We ran the TX on a dummy load on 40m with pink noise input running at 110% modulation for a continuous key down of 26 hours. We noticed no significant problems.

Some of the folks here heard this prototype on the air and can comment if they feel so inclined on how it sounded on the air.

John LeVasseur, W2WDX

[kb3ouk]

How are you connecting the mod transformer? B+ straight through the secondary, modified Heising or parallel-feed?

[N4LTA]

I think there is a lot of promise in using the Hammond 125FSE and GSE single ended transformers for modulation transformers. Both are large heavy iron and are rated for 90 mA and 100 mA DC current.

A 4 or 8 ohm input can be matched for many output impedances and using a modified Heising choke to get rid of the DC bias probably allows them to be rated at 100 watts or so. I plan to test a GFE soon.

Pat
N4LTA

[kb3ouk]

actually, with a single-ended transformer, you might not need the heising choke at all. most of these transformers have a gapped core to handle the unbalanced DC on the primary. feeding one backwards, the primary is hooked inline with the power supply and the RF final. normal mod iron has a gapped core to deal with the unbalanced DC on the secondary. the reason for the heising coke is to keep the DC current, which is what causes core saturation, off of the transformer. this is what is needed when a backwards-connected audio transformer or even a power transformer is used as a modulation transformer.

[N4LTA]

Yes - They are rated for 90 and 100 mA of DC which works well at lower powers but I suspect that their power can be tripled with a choke. They are big hunks of iron for the power rating. Hi pot rating may be their downfall for larger transmitters.

Hammond also make a big moose of a SE transformer rated at 300mA and hi potted to 3500 volts. It weighs 28 pounds and has a 55 H winding but it cost  $325. I suspect that it would work fine at 200-300 watts.

I have seen the Sowter tranformers but they are too hooked up with the audiophoolery crowd to suit me. Way to expensive anyway. At those prices , I am sure Hammond would wind a custom transformer if there was any demand at all. Hoerboer could also do it if there was any demand.

Pat
N4LTA

[WBear2GCR]

Sowter is a very conservative and iirc old English mfr of high quality xfmrs. Excellent performance and specs in general.

They are not "hooked up" with anyone.
Audio hobbyists learned of them from people in England and have sought them out, as have recording studios (when there still were recording studios...). Nothing whatsoever to do with any snake oil or nonsense. FYI and FWIW.

Generally speaking you get what you pay for.

Since we do not usually want or need response out past 20kHz. their value may or may not be there for AM ham users.


                             _-_-bear

[W8VG]

Don't know about use as mod tranny--still have to try that--but Stu's posts served as inspiration and I tried Antek 12 Volt Filament tranny to excite grids of 811A's in PP.  Exciting with one channel of board-kit 15 watt stereo amp with line level audio.  Works great with super response.  Modulating single 813 with Stancor multimatch.
73's Geo 

[w1vtp]

Don't know about use as mod tranny--still have to try that--but Stu's posts served as inspiration and I tried Antek 12 Volt Filament tranny to excite grids of 811A's in PP.  Exciting with one channel of board-kit 15 watt stereo amp with line level audio.  Works great with super response.  Modulating single 813 with Stancor multimatch.
73's Geo 

Very nice!

[W3RSW]

Geo,
I agree, "very nice"' and your rig looks like a Christmas tree, what with the slightly out of focus pilot lights. 

Very nice panel and window layout in particular...  Pix of the amp inside?

[N4LTA]

Anytime someone sell a 30 watt modulation transformer for $300-400 or more delivered -  they are hooked up with some kind of Phoolery. Quality is one thing and maybe they are gold plated - but Sowter's customer base is deep into audiophoolery.

People who pay $300- 700 each for an output transformer meet my definition of audiophoolery - but that's just my opinion.

Pat
STF

[W8VG]

Don't know about use as mod tranny--still have to try that--but Stu's posts served as inspiration and I tried Antek 12 Volt Filament tranny to excite grids of 811A's in PP.  Exciting with one channel of board-kit 15 watt stereo amp with line level audio.  Works great with super response.  Modulating single 813 with Stancor multimatch.
73's Geo 

Very nice!

Geo,
I agree, "very nice"' and your rig looks like a Christmas tree, what with the slightly out of focus pilot lights. 

Very nice panel and window layout in particular...  Pix of the amp inside?

Thanks Guys.  Here are some slightly better pics--you can see the antek tranney better. This started out as a junkbox prototype RF deck--hence all the odd sized DoD surplus chassis and "home depot" stuff. Was experimenting with various biasing arrangements, neutrialization, and rf coils on single 813 deck.....and took off from there.  Went a bit farther than I'd originally intended. Bandswitching and JV2 knobs, paint, cabinet, pilotlights were after-thoughts.  Paint left over from R-390 panel repaint.  Coils are all homemade--based on a 15 year old QST article--highly recommend it.  Can get everything for em at Lowes or Home Depot. Power supply is on plexiglass and oak slat chassis.  Operated it on floor for a longtime--which allowed me to try different things and want to continue with that out here in CA.  Still want to experiment with Antek Mod tranney and modified heising...maybe add preamp, try some neg feedback.  Plenty of room in cab for it.  Note shack doors are closed--so the cat can't come in   

Metal work is all dremel, scroll saw, etc.  Used fly cutter to do two meter holes and then resorted to borrowing a punch.  Too much work!

When company alerted me of impending Calif move, XYL demanded I get it off the basement floor so cabinet was something put together in hurry--inexpensive shelving and flashing/aluminum screen for shielding RF deck.  When I get it out here--is going back on bench or the deck to I can continue to play/add on 

I don't post much but love to read everybody's ideas here--much inspiration derived from em. 


Best 73's Geo

[W2WDX]

Anytime someone sell a 30 watt modulation transformer for $300-400 or more delivered -  they are hooked up with some kind of Phoolery. Quality is one thing and maybe they are gold plated - but Sowter's customer base is deep into audiophoolery.

People who pay $300- 700 each for an output transformer meet my definition of audiophoolery - but that's just my opinion.

Pat
STF

What decade (or century) are you living in I wonder? Let's see ... a 30w mod transformer in 1957 cost about $49 so adjusted for inflation the same transformer today would cost about $400. Seems about right to me.

This thinking is the reason you will never see any new electronics built with any quality ever again. To hit the price points based on 1950's pricing means you MUST build junk to hit the price anticipation of the Ham radio buyers who think everything should cost the same as it did decades ago.

The same transformers sold by other manufacturers to the audiophoolery market sell for thousands of dollars. Sowter is actually selling the type of transformers they build for low prices based on current dollar values.

You are the "phool" if you think you are going to get a new transformer of any real quality for our applications on the cheap, which anything under $300 would be.

The majority of sales for Sowter BTW is to the guitar player market, not the audio fools. And they are cheaper than Hams ("starving musicians") when it comes to buying stuff. Marshall and Vox used to use Sowter to build their transformers, before Korg bought them out and moved manufacturing to China.

So if you want an inexpensive new transformer buy something made in China, otherwise go buy your used junk at a fester.

Sorry ... that thinking just pisses me off.

Geez!

John

[KM1H]

Anytime someone sell a 30 watt modulation transformer for $300-400 or more delivered -  they are hooked up with some kind of Phoolery. Quality is one thing and maybe they are gold plated - but Sowter's customer base is deep into audiophoolery.

People who pay $300- 700 each for an output transformer meet my definition of audiophoolery - but that's just my opinion.

Pat
STF

I totally agree with Pat, the audioholes simply dont care what it costs and I enjoy seeing them get ripped off.

In 1957 you could buy a NIB ART-13, TCS, or similar mod transformer for $5.

What decade (or century) are you living in I wonder? Let's see ... a 30w mod transformer in 1957 cost about $49 so adjusted for inflation the same transformer today would cost about $400. Seems about right to me.

I dont know what orfice you pulled that number out of but in 1957 a generic communications style 30W mod transformer, even multi tap, was under $10. The much praised CVM-1 was a whopping $13.80 and those are list prices.
The DX-100 replacement was $16.95 if I remember.
So using your inflation example a CVM-1 should be around $110 today and put the 300W CVM-4 at around $315 which sounds just about right.

So if you want an inexpensive new transformer buy something made in China, otherwise go buy your used junk at a fester.

Sorry ... that thinking just pisses me off.

Well you better get used to it since anyone who comes here expecting to pimp overpriced audiohole stuff deserves it.

Maybe if you go to the Collins forum you would find a more receptive audience as many of them are big on cash but low on smarts.
Its usually the other way around on here and most elsewhere

Unless American transformer winders get their prices in line with realistic profit margins I would welcome Chinese or any other countries iron if it offered a decent savings.

Carl

[W3RSW]

Curious what P. Dahl would say if he were still around.  There was a great guy making a great product.  Timely and tape wound too. I don't think his margin was excessive.  Of course copper, etc. has sky-rocketed since.

Call up his price list on mod. iron replacements.  Tres interessant for 1990's.

[KM1H]

For 7 years I was selling locally built transformers in direct competition with Dahl. I sold for 30-40% less PLUS cleared a nice profit so dont tell me about Dahls "perceived" margin. While Dahl regularly raised prices claiming copper and steel cost increases my guy had longer time periods and less dollar increases.
Id still be selling them if the company owner had not died suddenly and the place was liquidated.

I also quoted shipping charges up front instead of shipping the most expensive way with shipping COD...one of Dahls known tricks.

Carl

[WBear2GCR]

anyone who can get me hifi output iron equal or better than Sowter quality, at a price that is better, like 25% of Sowter retail, step up. I'd like to buy some. We can both make some money. I am quite serious. I'd even consider Chinese product, if I could figure out how the heck to do business with them.

But if you have product, I'd like to see it.

In fact, I do not think I can wind an output transformer in the 30+ watt class for $100 in raw parts, it would be darn close today... and that is buying in what would be commercially small lots of core, wire and associated parts. (forget about labor, overheads and profit margin)

Step up, I would do it.

I own two Meteor Swiss coil winding machines. C'mawn!

               _-_- bear

[KM1H]

Why not try it and see? Something not fancy and with only a few impedance options. Open frame (if feasible at 30W) with color coded leads, user tapes up or cuts what isnt needed.

KISS

[K5UJ]

anyone who can get me hifi output iron equal or better than Sowter quality, at a price that is better, like 25% of Sowter retail, step up.

Where, in the U.S.?  It won't happen.  Why:  Because of a hidden cost in America that most hams fail to notice--the sky high cost of employee medical plans now.  This is one of the big reasons your RF amp that was $2K 10 years ago is now $4K.  Of course this assumes the manufacturer wants to have decent manufacturing employees who have jobs with benefits like disability insurance (a good idea for people in machine shops).    But since consumers now think everything should cost what cheap crap goes for at Great Wal-Mart of China, they get junk and outfits like Apple have their stuff made where no one has ever heard of medical plans.

[Steve - K4HX]

Where did your computer come from Rob?

Also, much of the so called news about Apple factories was made up.

http://online.wsj.com/article/SB10001424052702304459804577285713362126158.html?mod=ITP_businessandfinance_0

http://www.youtube.com/watch?v=DDWgMXoQnH8&feature=youtu.be

[K5UJ]

Where did your computer come from Rob?

Kindly explain your desire to make this personal.  I use a mac; I did not know where it was made at the time and in 2008 when I bought it I was not concerned with buying American like I am now.  Does any of this change where Apple's products are made?

And, where are they made Steve?  Are they made in the U.S.?

[Steve - K4HX]

You did not know in 2008 that nearly all computers (or at least the component parts) are made off shore? Really?

The sky is blue.
Water is wet.
Apple (and all other computers) are made off shore.

Tell us something we don't already know.

BTW, it's hardly personal. I own five Apple products currently and have been using their stuff since the early 90's. 

[W2WDX]

First let me apologize for the attitude. In my defense it was late, and I just had long argument with a supplier about pricing. So costs of quality products was on my mind and an irritation.

What I will say is I don't know where I got the $49 number, I thought I typed $19 (damn number keypad and chubby fingers.) My $400 number is spot on. If you included the inflation of the dollar, higher relative labor costs in the US, AND factor in the 12x increase on the price of copper since that time.

The audiophools are properly named. They are fools. However that doesn't change the fact that the cost of raw components is now high simply due to real costs. The people who buy the parts, the hi-end audio equipment manufacturers, are the ones who charge the outrageous prices. Simple single ended EL-34 based tubes amps selling for $40,000 is not uncommon. Does it cost half that to build it? Not even close. If it costs $1000 I would be surprised. So don't blame companies like Sowter, they actually are reasonable and inline with real non-audiophoolery costs.

Hammond is a steal BTW. They manage on economies of scale, due to larger production.

BTW, if you want to buy American, for anything, good luck. Our "cheap" American attitudes and need to have everything stay at the same prices over decades have forced this shift in economy.

Just look at MFJ versus any other Ham radio market company with products made here. Well the cheap Asian crap they sell is the number one product. Why? Because Ham's do not want quality or US made products, they want it all "on the cheap". We talk big about "buying US made", but when it comes down to it we Americans can't or won't pay for it. How many Ten-Tec's do you own? MFJ just bought out Palstar. And so it goes ...

Again sorry about the attitude in the earlier post. That was un-called for and I apologize.

John, W2WDX

[Pete, WA2CWA]

MFJ just bought out Palstar. And so it goes ...
John, W2WDX

When did this happen?