Can this be manufactured?

If you are adjusting something then it should, in principle, to build the units without the variations that you are correcting with adjustments. Making it manufacturable may involve learning more about what causes the variations in operation in much more detail.

Then there is a possibility that you can include a microprocessor that makes measurements and records adjustments in digital pots or EEPROM to control other circuits driven by digital to analog converters so that he adjustments are automated, even though it makes the schematic more complicated.

Further, having adjustments is often used in commercial products, just because it's cheaper to have someone adjust a trimmer cap or pot while they are checking it out anyway than to buy unobtainium parts and materials that would "guarantee" the accuracy (and you'd still have to test it to be sure the manufacturing didn't damage a part or you didn't get a bad batch, or they didn't put the thing together wrong, or purchasing didn't buy a bad substitute etc. etc.

Yes, it also provides some protection against copying otherwise unprotectable products. Usually there's some trade-off in using digital adjustments- for example you may sacrifice a bit of the range of an ADC to allow digital calibration and zero adjustment without needing (yuk) digital pots for such DC purposes. In the US, the DMCA may provide extraordinary protection, if you can afford to pursue legal remedies.

Perhaps you could save us from guessing by telling us what you mean by "customized" in your original message.

Best regards, Spehro Pefhany

It isn't impossible. Remember to charge accordingly for the device.

If your customization is a "standard" customization, you could automate the process to some extent. Make as much of the device as standard as possible. Make the customizations as easy to do as possible.

Consider manufacturing 2 models, regular and precision. The latter would be tweaked and expensive, the former would be the same thing (different color, perhaps), but not tweaked, and less expensive.

The parts that must be customized are 4 1N34A Germanium diodes (D1-D4) and 2 resistors (R1 and R2). D1 and D2 must be a matched pair, and D3 and D4 must also be a matched pair. R1 and R2 are the same value, but this optimum value will vary from one unit to another. It could be 1X in Unit A, .6X in Unit B, and 1.5X in unit C.

Selecting parts at random won't cut it. To produce one unit manually, I need to use an oscilloscope and sinusoidal function generator to test things. I set up the sub-circuits that use D1-D4 and R1-R2. It takes trial and error to find matching diodes for D1 and D2 and then more trial and error to find matching diodes for D3 and D4. Once I have these matching diodes in place, it takes trial and error to find the resistance value I need for R1 and R2. I cannot know in advance the proper resistance value, as it could vary by as much as a factor of 2-3.

If D1-D4 are selected at random from a pile of 1N34As, then my product would be just as crude as all the other SWR meters out there. That would kill the main selling point of my version of the SWR meter.

How much more would it cost to manufacture my product WITH the required customization? Most SWR/wattmeter products on the amateur radio market have a price under $100. The amateur radio market is limited in size and is also fairly price sensitive. I don't know much about manufacturing, but I do know that it would take a healthy volume to bring down the per-unit cost, and I'm not sure if the amateur radio market is big enough to support such volume. What volume does it take for manufacturing economies of scale to kick in? 10 units? 100 units? 1000 units? 10,000 units? If it only takes 10 units, then I better drop everything to get in business. If it takes 10,000 units, then my idea is not viable as a business.

Jason Hsu, AG4DG usenet@@@jasonhsu.com

Hmm... I suppose you can't use an integrated Schottky diode array that would already be matched well enough by virtue of them being on the same wafer?

Why can't you use trimpots?

Yes.

Sounds troublesome because it requires care AND significant labor on the part of the person doing the selection. Try to design this bit out if you possibly can. It's okay to have a bit of care required, but try to minimize the minutes or seconds per piece- it may end up being YOU doing it, and that could be limiting.

You have the opportunity learn something with every unit built. Oh, you want a rule of thumb? Double the number of units and the cost goes down 20%. Of course it's wrong, but it's easy to remember. ;-)

You may find you can make 10 units at $500 each and at least break even, but to get the price down to $100 you need to make a few hundred or 1000.

Best regards, Spehro Pefhany

The economies of scale generally refer to the reduction in labor possible because large runs can justify better setups. If you must tune and match diodes in a trial and error method, then you will quickly lose any advantage, unless perhaps you can automate the diode checking, give each diode an exact value, sort by that value, and then pick up the right matched pair.

The level of customization as you present it would preclude large scale production at first. You might be able to have most of the unit made in large scale, then finish and tune each one individually as needed.

Michael

Sounds to me like you need better and more consistent parts, as suggested before, and maybe need to use DSP to process your signal after that stage. Are looking at a signal out of a bridge?

You may have underestimated the size of your potential market. Not only the Hams but also the Professional Radio Engineering market should be considered. What might be expensive "nice to have" in one area is the other's "cheap but good" product. However, if all you are looking at is a superior SWR meter then what is your USP when compared to some products that are already available in the professional range.

You may need to do a bit more market research to evaluate whether or not you have aproduct that is worth developing.

"Jason Hsu" wrote in message news: snipped-for-privacy@posting.google.com...

news:...

Jason,

Sounds like your solution exploits the benefits of a wheatstone bridge. The problem of diode matching in bridge circuits has been around for 50 years. One solution is to use a quad array that specifies each diode be manufactured on a single die. The process control on a single die is orders of magnitude tighter vs. randomly selected single units from different die lots. The inherent matching may be good enough to eliminate the manual tuning step. It will also likely enable a smaller, easier to produce design.

One thing to keep in mind with building the 'better mousetrap' is to do some research on how good are the existing mousetraps. In your case, can you quantify the benefits of your SWR measurement invention vs. the commercial units? Maybe the performance benefit, though measurable, is not commercially useful. Also, take a look inside the commercial units; you will find they are very simple with the minimum component cost. If your solution's parts list costs more, even by 50 cents, it may be unattractive to the industry. I suggest you create a datasheet for your device listing its performance capability. Use a commercial unit's datasheet for comparison to make sure you capture all the pertinent specs. Count the number of parts in your design and list it. List the size of your circuit card and whether it is single sided or 2-sided ( if you need more than 2 layers, then it is probably already too expensive). Finally, note in block diagram form the steps required to manufacture it, including the necessary test equipment, steps that you think can be automated, etc. Focus on how to eliminate any manual tuning steps. Just to give you a reference point, the celluar phone industry produces highly complex radios that require no manual tuning steps at all. All calibration information is stored in the phone's memory and recalled during operation. Forward your product description to the commercial manufacturers and ask them to review whether they might be nterested in your design and further discussion. I would do this before pursuing any further patent activities; if no one is interested with the above description (for any of the reasons listed above), you will have saved much wasted effort.