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Should PCM receivers really cost more?

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Old 05-30-2003, 06:36 PM
  #1  
greenboot
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Default Should PCM receivers really cost more?

Judging by the size of the box (like that matters), it seems a PCM receiver shouldn't cost any more to produce than a "standard" FM receiver. Is there any justification for charging twice as much for the PCM boxes? It seems like they would have recouped their development costs by now.

Tom
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Old 05-30-2003, 07:05 PM
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Default Should PCM receivers really cost more?

They will keep recouping it for as long as they can. I am looking for a TCAS for my real plane. It is 2X3X10, cost is over $25,000. There can't be a couple hundred bucks worth of stuff in there. If they dropped it to something like $5000 it would be in every plane in the world and they would make a ton, but they are trying to make as much as they can, as fast as they can. Really dumb. Happens in every aspect of life as well. Do you really think a harley costs $20+ grand to build?
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Old 05-30-2003, 08:07 PM
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Default Should PCM receivers really cost more?

Flyboy,

The cost of the actual hardware is insignificant compared to the engineering/certifcation etc... And the certification level is at least 'B' for a TCAS, which really drives the cost.


Now, I agree with you that the price of PCM could come down some. But as long the coding is proprietery, that is not going to happen soon.

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Old 05-30-2003, 08:07 PM
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Rodney
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Default Should PCM receivers really cost more?

Yes, the added complexity of the decoder circuit warrents the increased price, in fact it is a bargin for what the additional design and circuit components cost. I'm not a fan of PCM but, being an electrical engineer, I do understand the increased costs.
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Old 05-30-2003, 09:34 PM
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Default Should PCM receivers really cost more?

azhar, I agree. They will just keep selling them for as much as they can get for them till it slows down, then drop the price and sell a bunch more (both the PCM and TCAS).

For me, the PCM is easy to justify. There are lots of people who don't feel that way and fly FM. Nothing wrong with that either. Both work well.

Like you said, I don't think you will see a huge drop in price, but they have come down a bit. I can get recievers now for about $50 cheaper than say a year ago.
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Old 05-30-2003, 09:40 PM
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Default Should PCM receivers really cost more?

I haven't seen the circuitry, but PCM is just another integrated chip isn't it?

If it is, then forget about the unit costs, it's only the development costs, the software and tooling costs that are being recovered, and you don't see physical evidence of any of those in the product itself.

After all, the material the chips made of is silicon, and that's available by the ton, free, on any beach!

-David C.
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Old 05-31-2003, 05:46 AM
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Default Should PCM receivers really cost more?

Rodney.. PCM receivers can cost over 150 dollars and all it does is receive and decode a 9600bit/sec RF signal at 72MHz... Now lets compare that to a moment to say a USB wireless card. Which can transmit, recieve, decode, encode, encrypt and route a 11mbit/sec signal at 2GHz which (checking on pricewatch) can go for as little as 33 dollars... Justify the cost of a PCM receiver knowing that... It is all in the development cost. There are more people willing to buy wireless adapters now so companies are willing to spend big bucks developing them, they know they're going to get their money back. Aren't enough RC users to justify the same development costs for a product.
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Old 05-31-2003, 07:09 AM
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Default Should PCM receivers really cost more?

Probably a lot more USB wireless cards sold than PCM receivers already. And when more are sold they will be down to 14.95. That's how it works. Volumes speak volumes about pricing.
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Old 05-31-2003, 09:54 AM
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Default Should PCM receivers really cost more?

I have to agree with Lynx, here. Look at it this way, the difference in price of a PCM radio "package" and an FM package is usually about $30-40. .maybe as high as 60. The difference is probably close to 50% actual part cost increase and 50% additional profit.

Look at a Sony Walkman. . AM, FM, tuneable, Cassette or CD, headphones, less than $60 in some places, and it has a ton more circuitry than our receivers.

They use the same basic casing for most receivers form a manufacturer, unless they change the size. Look at most receivers and they seem to be just a re-labelling of the previous model, with a slight "improvement" in the internal circuitry. PCM has been out for over 10 years now, FM for over 25, and the encryupted 'bits' code-train in PCM is the same, except for polarity, for each manufacturer (It's an FCC rule)

Are we getting "gouged". . . you bet!! Just like 8411 servos going for $115 at most places when you can get the more robust 5945 HiTecs for as little as $75. . . . .someone is making a KILLER profit margin.
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Old 05-31-2003, 01:55 PM
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Default Should PCM receivers really cost more?

At least the prices are starting to come down some. JR has the new 770 for $99 street price. Maybe some of the others will drop in price again too or at least drop the price on new models. It boils down to competition and what the end user is willing to pay.
Ed M.
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Old 05-31-2003, 03:10 PM
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Default Should PCM receivers really cost more?

If the development cost was $10 million and you sold 1 million you'd have to price each at 10 dollars to cover the costs.

If, however, you only sold 100,000 you would have to charge $100 for the same thing.

Since the unit cost is so low, it hardly enters the equation.

How many potential Network Interface Card buyers are there compared with RC radios receiver buyers?

-DC
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Old 05-31-2003, 11:48 PM
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Default Should PCM receivers really cost more?

Since PCM is proprietary by manufacturer, there is no competition to encourage lower prices.
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Old 06-02-2003, 04:53 PM
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Luke 3D
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Default Should PCM receivers really cost more?

All the pro flyers that ive talked to(paul skinner e.t.c) hate PCM- they would rather have FM glitches that they could fight rather than have a completely locked in fail safe plane that they can't do anything about.
Hey well guys, we all know the real definition of PCM.
Its not pulse code modulation, its Probably Costs More!
Now you can get a Multiplex IPD(intelliegent pulse decoder) reciever which is loads better(all the advantages of PCM and FM) for a lot less(FM receiver prices). When these catch on, pcm will probably become extinct(unless they lower their prices by a hell of a lot), so we will no longer have debates about the overpriciness of PCM!
yipee
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Old 06-02-2003, 05:28 PM
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Default Should PCM receivers really cost more?

Originally posted by MPX_4000
Since PCM is proprietary by manufacturer, there is no competition to encourage lower prices.
Not necessarily so, since the mfg is usually pitting their PCM receivers against their PPM receivers. They tout the benefits, but people will only pay so much for them. I got an 8 channel PCM receiver for Futaba for 100 bucks - that's a good deal.
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Old 06-02-2003, 11:19 PM
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Default Should PCM receivers really cost more?

Originally posted by Luke 3D

Now you can get a Multiplex IPD(intelliegent pulse decoder) reciever which is loads better(all the advantages of PCM and FM) for a lot less(FM receiver prices). When these catch on, pcm will probably become extinct(unless they lower their prices by a hell of a lot), so we will no longer have debates about the overpriciness of PCM!
yipee
Luke
No way is IPD better. Check the resolution of the system. If you don't care about performance fine but don't claim it is better. In fact I'd say it has the disadvantages of both.
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Old 06-03-2003, 01:44 AM
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Default IPD Receivers

I have flown FM, Futaba 1024 PCM and Multiplex IPD receivers for many years now and feel no advantage of resolution of one over another, and I fly F3A which requires very precise equipment. I have not encountered any interference at my flying field that I felt, but if there is interference then the IPD receiver does become less precise as shown in the following advertisement, but less precision and some control may possibly be better than failsafe and no control:

"The new IPD process is a MULTIPLEX development which combines the best features of two different systems: the advantages of PPM - speed and compatibility - with the safety of PCM - to detect and suppress interference.
As fast as PPM
Compatible with other PPM transmitters
Detects invalid signals
No servo jitter with transmitter switched off
Servo Hold function
Servo Failsafe function
No servo travel beyond set limit values.

IPD receivers can be operated with all standard FM PPM transmitters on the appropriate frequency. In the event of radio interference, IPD receivers will help you maintain control, and in the event of unrecoverable interference, the receiverís behaviour is similar to that of PCM receivers, with the servos moving to a pre-set failsafe position.

IPD stands for Intelligent Pulse Decoding, and the receiver incorporates a processor which analyzes the incoming signal for validity. Like a PCM system, IPD filters out invalid signals.

The difference between IPD and PCM is that the receiver does not 'switch off' the 'dirty' signal as field strength declines, but instead widens its tolerance. If the signal weakens, the receiver software starts to calculate an average pulse width using the values of subsequent pulses, which are normally slightly different caused by the jitter of the signal. The so called "floating average" suppresses the effect of jitter. As an additional help, the resolution of the signals, sent to the servos, is also reduced. Those two effects result in a slower reaction of the model, which you can take as an warning of interference. This "visible" warning enables you to take action (e.g. change direction of flight, hold the tx up, ...) This means that control becomes less precise as field strength falls away, but remains usable for longer (greater range). The result is that you can infer the approaching limit of range from the modelís behaviour, whereas PCM suddenly robs you of control.

An IPD receiver sees all usual PPM formats as valid, which means that all standard FM PPM transmitters on the same frequency can be used with IPD receivers

IPD is faster than PCM because there are no check cycles.

The user programs the fail-safe positions of all channels into the IPD receiver. The transmitter is used to set all servos to the desired positions.

Practical testing has shown that IPD and PCM produce comparable results when unrecoverable interference occurs. But please donít get complacent: Like PCM, IPD is not an excuse for incompetent RC installation and careless cable deployment, and thorough suppression of electric motors and ignition systems is still essential."
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Old 06-03-2003, 02:45 AM
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Default Re: IPD Receivers

[QUOTE]Originally posted by MPX_4000
[B]I have flown FM, Futaba 1024 PCM and Multiplex IPD receivers for many years now and feel no advantage of resolution of one over another, and I fly F3A which requires very precise equipment. I have not encountered any interference at my flying field that I felt, but if there is interference then the IPD receiver does become less precise as shown in the following advertisement, but less precision and some control may possibly be better than failsafe and no control:

If you get a chance borrow a Hitec servo programmer which will allow you to measure the pulse width of the signal coming out of the receiver. In a good PCM system you will be able to change the pulse width in increments as small as 1.17 microseconds as I recall. I don't remember what I measured on the IPD but I remember I was shocked by the loss of resolution as a result of the signal processing they do. It does get rid of the jitter but at a high cost in terms of resolution. If you are happy with it don't by good servos because it will be a waste.
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Old 06-03-2003, 03:07 AM
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Default Should PCM receivers really cost more?

Originally posted by OhD
No way is IPD better. Check the resolution of the system. If you don't care about performance fine but don't claim it is better. In fact I'd say it has the disadvantages of both.
Is the resolution worse than 512?

I confess my flying accuracy isn't good enough to notice a step of 1/512th of the total movement. Let's see, the elevator only moves about 1/4 inch, so that 1/2048th of an inch per click.

That'll do me!

-David C.
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Old 06-03-2003, 05:20 AM
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Default Should PCM receivers really cost more?

IPD is just a filtered PPM signal, so it's fully analog (no stepping at all)
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Old 06-03-2003, 06:11 AM
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Default Re: Re: IPD Receivers

[QUOTE]Originally posted by OhD
[B]
Originally posted by MPX_4000
IPD but I remember I was shocked by the loss of resolution as a result of the signal processing they do. It does get rid of the jitter but at a high cost in terms of resolution. If you are happy with it don't by good servos because it will be a waste.
That is not true. I use IPD with the JR8411 digital servo and the notion that the IPD receiver gives poor resolution is simply false. If you are getting a normal strength signal the IPD does not do any processing, that only occurs at the extremes of range or otherwise impaired signal where data is poor but not so poor that failsafe needs to kick in.

Harry
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Old 06-03-2003, 08:02 AM
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Default Should PCM receivers really cost more?

Analog PPM is a thing of the past, it started dying when first computer radios came to market.

There is stepping that originates from A/D conversion in the transmitter and there is stepping that comes from timing circuits in IPD receiver MCU. No matter how strong the signal is its resolution can't be better than four times MCU clock pulse period and that is only if MCU has 16 bit timer/PWM circuits. If it has 8 bit timer/PWM circuits then things get worse.


Originally posted by Lynx
IPD is just a filtered PPM signal, so it's fully analog (no stepping at all)
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Old 06-03-2003, 09:16 AM
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Default Should PCM receivers really cost more?

sooooo.. . IPD is nothing more than a normal FM reciever, with some signal reception and amplification circuits thrown in, a PCM-type failsafe function thrown into the mix, and better resolution (within the limitations of the PPM timing window).

So, it can still go into "failsafe" (how do you program that with your standard FM radio?????) which means a lockout, and being FM is more prone to interference than PCM, no matter what kind of fancy receiver doo-dads you come up with to increase sensitivity. It seems that the way that sensitivity is increased, by actually widening the frequency "window" in the RF and IF amplifiers, would make it more prone to interference at the lmiit of sensitivity, which is pretty darned undesirable if the receiver is losing signal due to interference from something on the very edge of the frequency. You are still limited to the "narrow band" for your frequency, for total frequency bandwidth, and being that these "bands" are really bell-curve areas of sensitivity, the outer edges of that "sensitivity range" would actually be outside the desired 10khz (if I recall properly) of maximum frequency deviation allowed by the FCC for transmitters.. . . .

You know. . .U-control and solid steel cables is starting to look more attractive all the time.

There are advantages and disadvantages to every signal and receiver design. The ABC&W from JR is not living up to it's hype, dual conversion still has the upper hand, IPD gives you the worst-case scenarios of "lockout", FM is subject to getting hits from somebody sneezing hard at the other end of the flightline, and AM is a disaster.

Think I'll go over to HAM band so I can transmit 500 watts. . . . . Interfere with THAT!!!!!
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Old 06-03-2003, 09:42 AM
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Default Should PCM receivers really cost more?

PCM better than IPD? errrrmmmmmmm welllll .
IPD is not just an FM reciever.
I can't be bothered to get out the sheet with all the info about them but i can remember some of it.
They are faster than PCM so you get better control- snap rolls can be exited when they exit rather than before- walls are also better with IPD vs. PCM
They filter out any interference(rather than increase sensitvity) up to a certain intolerable level where they go into fail safe. You can tell when its almost going into failsafe or out of range because the controls become more slow and sluggish( the low resolution of the signal filtering that OhD was experiencing), giving you time to turn back towards yourself or raise the transmitter aerial vertical, or turn the plane away from the crowd, or land it really quickly e.t.c .This is something that PCM doesn't do. It filters out a bit and then....... bam into failsafe without any warning.
IPD failsafe programming is very easy. there is a plug in the reciever that you take out, set your controls to the desired positions, and then put the plug back in and the fail safe is memorised by the reciever.
What do you guys think are the best conrol movements for a failsafe? I think that having both ailerons go up about 60 degrees , throttle back and full up 60 degrees elevator would slow down the plane like anything and then have the plane go into a stable elevator.or am i just talking nonsense?
This thread is really interesting, so lets not ruin it by turning this into a pointless argument.
Luke
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Old 06-03-2003, 09:55 AM
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Default Should PCM receivers really cost more?

I found out the HARD way that the "crowd saving" low-throttle snaproll failsafe is NOT the best way to set it up. I lost two planes at Joe Nall this year, because the Transmitter seemed to go intermittent after I removed then replaced the transmitter module.

I'd imagine a minor climbing turn, with about 1/8 throttle, would be the best way to both save the crowd, and possibly save the plane, in the event of failsafe lockout.
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Old 06-03-2003, 10:24 AM
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Default Should PCM receivers really cost more?

The movements i described do not make the plane snap roll.
it makes it go into a parachute.
the thing is though, with an aerobatic model, its not going straight and level . If you program it to do a climbing turn when its doing the inevitable inverted flight, you get a spiral dive- not good.
Aerobatics models are unstable so they won't stay level in a climbing turn- then will come down somewhere rather fast so it could hurt someone badly.Maybe a trainer could be programmed to do a climbing turn but then where does it go? up and up and up so far that youve lost your plane.
I think that the best bet is to make the plane go into a parachute manuver.Even the most unstable 3d planes are stable in a parachute, and come down slowly. Even if the plane is inverted it will still enter a parachute- but the only manuver this won't work is understandably on a low inverted flyby.
I think that the only way you can find out which failsafe setting is the best is to experiment by climbing up high and turning the transmitter off and seeing what it does at various attitudes e.t.c
Luke
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