Modified Heising Chokes Question

[W2WDX]

Hi All,

So here's the question: Does anybody know of a transformer manufacturer who makes an off the shelf choke that is 20H 200ma working voltage of at least 800v. I know this is uncommon these days. I am surprised actually since the scuttlebutt within the DIY audiophoolery circles is about trying to find larger chokes in this size class. Unfortunately audiophools do seem to drive the market for transformers these days. I do know I can get custom made chokes, but would prefer an off-the-shelf solution since this would most likely reduce cost. And no ... no vintage or used stuff. This is not for a one-off project.

The situation is a single 6146 (and/or two) being modulated by a pair of P-P EL-34's (AB1) running an Antek toroid as a modulation transformer. I am currently using two Hammond 10H chokes in series, but I want to reduce the size and weight and eliminate one transformer from the chassis design. 20H seems to be sufficient with the ~2uf series blocking cap and a load resistor paralleled on the mod iron output (not paralleled with the blocking cap as some have suggested.) I am also using about 4.5dB of feedback off the mod output going back into the modulator driver, so bear that in mind.

We may end up with a solid state modulator since this would also reduce the parts count but would force a  change in the Antek mod iron we are using. However this shouldn't affect the Heising choke choice, I assume.

The current design works very well, without any high frequency roll-off, oscillations, heating or other problems. Audio frequency response is better than we expected (usable 60Hz-7kHz), with marginal phase problems at these high and low working limits (surprisingly.) So I want to keep the design but reduce the component count & weight if I can.

I don't want to give out too many details since this is for a commercial design we hope to manufacture.

I also wonder if there is such a thing as a toroidal choke. Can't seem to find anything.

Thanks,

John, W2WDX

[WD5JKO]

  John,

  I did the Modified Heising once with three 8-10 Henry chokes in series, and the cases insulated from ground. The series choke idea eases the winding capacity issue that will shunt the higher frequencies. This is OK when the choke is used in a power supply, but in audio reactor mode we have a problem. So using several chokes in series helps; the resultant winding capacity is divided by the number of chokes in series. The winding resistance and inductance are additive.

  Another alternative is the single ended tube HI-FI audio transformers. Here the windings have low capacity, the core is gapped for DC current, the primary inductance is high (but not always specified), and these are readily available.

  I am linking one example from Edcor:
http://www.edcorusa.com/p/795/cxse25-8-10k

  The Edcor might work for a low power rig, and might need the case to be lifted from the chassis.

Jim
WD5JKO

[KE6DF]

Another option might be to design a modulation transformer -- and then use another one of the same modulation transformers with the windings in series as the Heising choke.

Of course, you need a mod trans that can handle DC for that to make sense.

But it uses a single part number for two purposes -- which is always nice when you are manufacturing something.

[W8VG]

John (WDX):  I've toyed with that idea on my HB rig but haven't tried anything.  Glad it at least works for ya. 

The chokes are always what seems to be limiting factor but a couple 6146's  should be less problem than my single 813.  Here's to your success!

On chokes, have seen some guitar replacements that go up into 40H at AES but are limited to 100-150ma. 

A few years back sent email to John at Antek and asked if he was interested in making chokes (he'd recently introduced line of audio output tranny's) but his answer was no...probably too much trouble for that type of technology and manufacture.  Suspect it could be done--putting a gap in a torroid core. 

Good luck!

Best 73's
Geo W8VG/6

[N4LTA]

John,

Hammond make a 30H 100 Ma choke  - I am using two in parallel as modified Heising chokes. It is the 194E and my gut is that they are good for 800 volts but they don't say so. They sell for about $43 each - If you want try them let me know - I can probably save you some money.

The Hammond 193J is 10H at 200 Ma at 800 volts but they are $48 or so each. There is not a easy cheap way to get a modulation reactor.

Hammond would probably make a good modulation choke if we could convince them they would sell .


Pat
N4LTA

[k4kyv]

I helped John, WA5BXO build a homebrew 30H 600 MA reactor back when I was living in Houston.  We found a couple of identical 10H 600 MA filter chokes that came out of an old CH 11 TV transmitter.  Took them apart and removed the I  laminations, and butted together the remaining E laminations with the coils left intact. Clamped them down with angle iron stock and nuts & bolts. Left a gap between the two cores, using the same composition material that was used to form the gap in one of the filter chokes.  Then wired the coils in series with the proper polarity, so that the inductances of the  coils were additive, not subtractive.

Theoretically, the  resultant inductance should have been 40 Hy, since the number of turns in the coil was effectively doubled, but we threw out some iron (the I laminations), so that might have been the reason we measured only approximately 30 Hy. We might have been able to attain more inductance by playing around with the gap  spacing, but John was satisfied with 30 H and didn't want to bother with disassembling and re-assembling the core multiple times. He used that reactor for many years.  It even survived a Houston flood and being submerged under water for several weeks.  He used it with a pair of 304TLs modulated by a quad of triode-connected 813s.  The high frequency response seemed to be quite good.

Combining two chokes in this manner results in one reactor that is smaller and  lighter in weight than the two unmodified chokes in series, and you  get substantially more inductance.  If the internal capacitance and/or core material of power supply chokes used as mod reactors results in high frequency loss, find a small choke, about a Henry or so, rated for the full current of the main choke, and wire it in series with the big one.  The small choke will provide adequate reactance for the higher frequencies and chances are without the high frequency loss of the big one, while the larger choke will provide the needed reactance for the lower audio frequencies where its loss is minimal.

To figure out how much total inductance is needed for the reactor, calculate about 8 Hy for every 1000 ohms of modulating impedance.  For example, you  run 2000V @ 500 MA to the final; the modulation transformer sees a 4000-ohm load, or 4 X 1000 ohms. So the inductance of the reactor should be at least 4 X 8 Henries, or 32 Henries.  A 30H reactor would work just fine.

[W2WDX]

Hi again,

Thank you for the suggestions. The issue here is not in the design of the Hesing reactor and modulation scheme, but the physical aspects of having so many transformers.

I should be more clear on the application maybe. This is for a commercially built product we are planning on offering to the amateur community within a year. It is a newly manufactured "boatanchor". The idea is that there is a real interest in a turn key new transmitter in our community.

Many Hams have been buying up older transmitters, and have been paying top dollar for many transmitters that either do not work or are fifty-plus years old. The restoration of these transmitters may also be beyond the ability of many Hams from either a lack of technical expertise or simply time available. Our feeling is many Hams would like to own transmitters of this type, but do not want to nor can they work on the radio. This is an untapped market IMO. I think there would be many more AM operators if something new and turn-key was available to them.

These reason should not disallow a Ham from using one these types of transmitters though. So we thought there would be market for a new transmitter using a hybrid approach. A new transmitter with new, modern parts & components. It will use a tube output, high-level modulation, digital frequency synthesis w/ memory. Also due to the changes FCC regulations, limiting the audio bandwidth is not necessary anymore like it was back in the day. This allows higher fidelity audio to be utilized. We also have incorporated more modern thinking in the handling of audio in this transmitter. Such as line inputs, tone controls, adjustable high and low pass filtering with sharp roll-off, and other features.

We can also design & test in such a way to fine tune the transmitter to achieve this high quality audio, but not produce the splatter (harmonics) that caused the original outdated rules to be so strict, but still present an issue of good operating practice.

The problem I am having is the complexity of the chassis, weight and cost of the transmitter. I want to reduce one choke. Like I said I am using two Hammond chokes right now in the design. It does work very well, however I want to eliminate one choke.

The transmitter is already large by modern standards. It is about the size & weight of a Hallicrafters HT-37. It uses point to point wiring in much of the circuitry, except for the modern components like the DDS VFO synthesizer. We are also planning the option of using three types of modulation schemes, one is an internal tube based modulator (P-P AB1), two would be an internal solid state modulator, and three is no modulator with an input for an external audio power amplifier of the operators choice. These variants would fall in at different price points and give people options.

I guess we will have to go to one of the manufacturers and have them build a custom choke for this transmitter. I didn't want to go that route since I wanted to have parts in this radio that people could acquire on their own in a pinch. Plus going this route probably will not reduce the cost.

So this is why I am hoping someone knows some obscure manufacturer that may have chokes of these values as stock items, but I'm guessing my research is already correct. It may not exist.

J

[IN3IEX]

Hi,   sorry for not completely understanding your approach. A single regular modulation transformer is smaller, and less expensive than the Heising "combination".
If you want to include something that can make the difference, why not include an ALC - AGC that really works for plate modulated AM transmitters?
http://amfone.net/Amforum/index.php?topic=30073.0
Use an integrated modulator with KT88s. I like tubes and I don't want any solid state in my TX (and my Audio Hi-Fi). If I want solid state I switch to classE classD DSP DDS combination... no tube at all... and real 2012 technology.  
Giorgio


BTW, making modulation transformer is easy....for instance  http://www.813am.qsl.br/artigos/tx/Brucutu.pdf has some instructions in the text.
I think that C laminated cores are best for making gapped transformers. Just put .5 mm insulating gap while assembling the thing.

[W2WDX]

I ended up with a modified Heising configuration because of the fact good mod iron is hard to find new. I would prefer a single mod iron solution ... but alas. The problem lies in the saturation that occurs from unbalanced DC on modern audio transformers; they just can't deal with it at the voltage and current levels we need them.

Honestly, if we could build transformers on a production scale we would. Not only to build our own products but to sell to the Ham community. But the knowledge to build transformers of this type is beyond our scope as a company, the cost would be high due to limited production (putting us outside the price point most Ham's would be willing to pay) and we would probably have to reinvent the wheel to do it properly.

Preferences of modulator types (i.e. SS, tube, external) is a personal thing which is why the design will be available with options in this respect.

John

[W7TFO]

Try my friend Jack Elliano, W6TNR.

He is in Las Vegas @ www.electra-print.com

He has the ability to wind just about anything you may need in production quantities.

73DG

[Pete, WA2CWA]

I should be more clear on the application maybe. This is for a commercially built product we are planning on offering to the amateur community within a year. It is a newly manufactured "boatanchor". The idea is that there is a real interest in a turn key new transmitter in our community.

Many Hams have been buying up older transmitters, and have been paying top dollar for many transmitters that either do not work or are fifty-plus years old. The restoration of these transmitters may also be beyond the ability of many Hams from either a lack of technical expertise or simply time available. Our feeling is many Hams would like to own transmitters of this type, but do not want to nor can they work on the radio. This is an untapped market IMO. I think there would be many more AM operators if something new and turn-key was available to them.

J

This was tried several years ago with the WRL knock-off "500D" transmitter and it was a failure. It's hard to believe there would be any substantial demand for an AM only transmitter in today's amateur radio community.

[k4kyv]

For the best quality, a modulation transformer/reactor combination is highly preferable to a single transformer carrying the DC to the final.  To even approach the same performance, the modulation transformer probably needs to be close to the same total size as a transformer designed to be used with a reactor, plus the reactor.

I have a  couple of mod transformers removed from 250-watt RCA broadcast transmitters.  One, designed for the reactor, is much smaller.  The one designed to carry the DC is the same size as the mod transformer they use in the kilowatt RCA transmitter (with a reactor). A huge amount of iron is needed to allow the transformer to perform without effects of saturation when it carries the unbalanced DC.

I should be more clear on the application maybe. This is for a commercially built product we are planning on offering to the amateur community within a year. It is a newly manufactured "boatanchor". The idea is that there is a real interest in a turn key new transmitter in our community.

Many Hams have been buying up older transmitters, and have been paying top dollar for many transmitters that either do not work or are fifty-plus years old. The restoration of these transmitters may also be beyond the ability of many Hams from either a lack of technical expertise or simply time available. Our feeling is many Hams would like to own transmitters of this type, but do not want to nor can they work on the radio. This is an untapped market IMO. I think there would be many more AM operators if something new and turn-key was available to them.

J

This was tried several years ago with the WRL knock-off "500D" transmitter and it was a failure. It's hard to believe there would be any substantial demand for an AM only transmitter in today's amateur radio community.

The problem was that transmitter was an over-priced, poorly designed piece of junk, and the integrity of the manufacturer was questionable. But hams tend to be cheap, so anything of good quality that merely broke even to manufacture and market would likely not sell.  Even the plastic radio retailers hardly make anything off the sale of a ricebox. For an AM transmitter, something along the lines of Class E would probably be a better bet.

[W2WDX]

Don I certainly agree with you on both points.

The WRL knock off was a complete failure not because the market isn't there, but because the transmitter was supposed to be a clone and was built badly to the extreme. It also was too big for the market both in price and size. Somebody who wants that power class will build it. However people pay $400 everyday for Ranger's that are not even in good working order. The market for smaller radios is there, it's just untapped. A BRAND NEW AM transmitter, of the same type, may be just what is needed.

I saw one these "Globe King" Clones. The transformers had detached from the chassis in shipping. Bits of the torn off chassis still attached to the mounts & screws. The thin aluminum chassis was so substandard it completely twisted around and was cracked in several places. The "manufacturer" refused to ship the radio with the larger transformers separated. The radio did not even work once it was put back together. It needed substantial circuit modification to get it to work and it performed marginally at best once this was done. The guy was trying to "cash in" and not really build something of any value at any price.

The market is there, but it's a small niche market. But things are different now with having global reach via the web. I have ten probably sold right now, if I could get it to market, without even trying. The issue for us is quality and performance, both of which are the top priority for me in releasing this product. If I cannot make this thing worthwhile in those aspects we will not produce it.

So far, the production prototype has exceeded my performance expectations. Now the time has to be put in to test the long term reliability. As we speak this prototype has been sitting on a bench running at 90% modulation with pink noise into a dummy load. It has been running that way continuously for nearly 2 months now. It has been heard on the air by many of the "big-gun" Northeast guys on 80m and the signal quality reports have been very positive. (I wish somebody had recorded it ... Oh well.)

Don, I knew the Heising arrangement was going to be the right way to go in terms of performance and weight. I just wish I could get this choke situation right, at least in terms of the component count. Otherwise, the two chokes in series arrangement does work well.

The problem with marketing a Class E is it will always be cheaper to build, it's easy to build and there apparently are patent issues, big patent issues it turns out. We began talking to Amateur industry people about a Class E transmitter for the Amateur market three years ago Out of the blue we got a letter from a lawyer from one of the big broadcast manufacturers. I can't even say who and what the details were without creating liability for us. To say the least we dropped the concept right there.

I will contact Jack, W6TNR and see what he can offer us. Thanks for the tip, TFO. That's what I am looking for. Any more?

John, W2WDX

[k4kyv]

We began talking to Amateur industry people about a Class E transmitter for the Amateur market three years ago Out of the blue we got a letter from a lawyer from one of the big broadcast manufacturers. I can't even say who and what the details were without creating liability for us.

How can revealing the details of a patent cause liability for anyone?  If it's legitimate, the full details including the identity of the patent holder as well as circuit descriptions are on public record via the patent office, and can be viewed on line if you know the patent number.

I haven't heard of anyone being hassled for freely exchanging class E circuits and how-to-build-it information, or for using class E transmitters over the air (although regardless, I think it's none of their business and beyond  their jurisdiction what a ham homebrews up and puts on the air for his own personal use, patents notwithstanding).  Look at Steve's web site. Not only detailed information, I believe he has, or had at one time, parts and circuit boards available to facilitate building one's own.

[W2WDX]

Don,

The difference isn't in the exchange of knowledge, it's in the potential of using specific knowledge for economic gain that another party feels they have a claim of ownership. When this company contacted me they wouldn't even discuss the specifics of their claim until I signed a non-disclosure statement. Since I was looking to produce something for the market, and seriously wanted to use this technology I had no choice but to open a dialog.

Signing the agreement was the only way that would happen. I can't discuss what was talked about, why it was talked about, or even if any offer was made. Even disclosing the details of even why I had to sign the agreement are limited to saying simply I had to. We decided not to pursue this matter after this dialog occurred.

Selling parts for homebrewing a specific technology is not the same as commercially manufacturing a complete product using the same technology. Steve has never sold a complete transmitter, manufactured as a production run, and I do not think he wants to. Probably for the same reasons I'm not.  

Its kinda like the Soybean situation here in the US with Monsanto & Round-Up.

I can't say anything more other than: Viking Vintage has no plans nor do we ever intend to market, build or construct any commercial products using the aforementioned technologies or derivatives thereof.

Silly right?

[k4kyv]

When this company contacted me they wouldn't even discuss the specifics of their claim until I signed a non-disclosure statement. Since I was looking to produce something for the market, and seriously wanted to use this technology I had no choice but to open a dialog. Signing the agreement was the only way that would happen.

So I take it after you signed the agreement, they informed you that they wouldn't allow anyone to commercially exploit the technology for the amateur market without their approval, but were not interesting in licensing to a third party nor marketing it themselves for the amateur market?

This sounds a lot like RCA's early monopoly on vacuum tube technology. 

I recall reading that someone once held a patent on crystal oscillator circuits, and that a transmitter manufacturer circumvented the patent by producing a crystal controlled transmitter that used a mechanical buzzer to physically vibrate the crystal, and that excitation generated enough carrier signal to drive a pre-amplifier and subsequent stages.

One of the the mid 1930s Frank C Jones Radio Handbooks carries an ad from Heinz-Kaufmann for "gridless" transmitting tubes, which used deflection plates somewhat like those in a CRT to control the electron flow to the plate, instead of a grid, to circumvent RCA's monopoly.

[Ed/KB1HYS]

How can a class of amplification be 'patented'  If I wrote a patent on a Class C radio amplifier, wouldn't that just be for the particular circuit? The mode of operation is dictated by physics, it would seem to be like patenting the ability to drive a car forwards and not some unit 'bit' that allows one to do that.   

Just odd thoughts.

For the rest, I think it would be viable to have a 'vintage' type rig available for new purchase, and Kudo's to anyone with the gumption to give it a go.

[W1VD]

Might try contacting Toroid Corp. of Maryland ... if you haven't already.

http://www.toroid.com/custom_transformers/dc_filter_chokes.htm

They have experience building toroid dc chokes and tube amplifier transformers ... as well as toroidal items for a large number of applications. I'm sure what you're looking for would be custom job but development costs may be reasonable ... how hard can it be to turn a toroid winding machine loose on an appropriate core.

[W2WDX]

I have one more related question that has made wonder for some time. Maybe some of you know the practical answer, I know the math.

I know that two inductors in series have some mutual coupling depending on the proximity and orientation. The common wisdom is to orient the inductors 90 degrees in relation to each other. Now the question is the formulas I have seen never take into account the orientation so how do you calculate your total inductance (including mutual inductance) for the different orientations? Or is it necessary? I am sure the coupling is different depending on orientation, but the formula doesn't specify. Or have I just missed it?

John

[k4kyv]

It would be about impossible to say.  Too many variables.  The shape of the magnetic field surrounding the chokes, the distance apart, the number of turns on each choke, etc.  It's something that would have to be measured.

Regarding mutual coupling, that's  the idea of removing the I  laminations and butting together the E laminations with the  coils on them.  This achieves maximum possible mutual coupling, so they could be considered one  choke.  With two chokes wired in series as a modulation reactor, the more mutual coupling, the better, since that would increase the total inductance available.  So, there would be no  reason  to orient them to keep coupling to a minimum.  Just be sure the coils are additive instead of subtracting from one another.  But unless they were modified as described above, I doubt you could get enough mutual coupling between separate chokes to make a measurable difference.

[W2WDX]

Thanks Don ... that explains alot. I did try them both ways and noticed no significant change in performance in our prototype. Maybe I'll keep them inline like I already have them. It looks nicer! 

John

[W7TFO]

This comment is relative only so far as what to expect in terms of size/weight for a modulation reactor as to copper & iron outlay.

I have a specimen rated at 60hY @ 750mA, is over 100 lbs and roughly is 15" H X 10" W X 12" deep, open frame EI type with 4 separate plies.

Buggar me, it's too heavy to lift just now....

73DG

[k4kyv]

Sounds a lot like the original one Gates used in the BC1-F.

[W7TFO]

Is from a late 60's ITA 1kW AM BC rig, using 4-400' X 4-400's.

73DG

[W2WDX]

  So do you think I can maintain a CCS rating on that if I get someone to duplicate it. Ya know,  with a single 6146 driven by a 30 watt modulator? I wonder if I can squeeze it onto the chassis somehow? I guess I couldn't ship my radios via standard UPS ground. 

Hmmm ...