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Old Mar 31, 2004, 11:26 AM
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DIY FM narrow band receivers

I have been investigating narrow band FM receivers for micro flight applications.

The design and construction looks relatively easy. The hard part is getting parts in small quantities. There are 3 parts. The narrow band fm chip; the ceramic 455KHz filter; the ceramic discriminator for the particular chip.

In my case I believe the following parts would make a nice receiver:
Toshiba: TA31136FN FM-IF chip
Murata: CFUCG455HX-TC Ceramic Filter 455kHz 6kHz bw
Murata: CDBCB455KCAY24-R0 Ceramic Discriminator

To extend the design to a double conversion receiver I would also require a smd crystal at 10.245 MHz

If anyone has solved this problem with this combination or another combination I would be very interested.
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Old Apr 01, 2004, 01:11 AM
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This was the subject of a thread in another forum

http://www.rcgroups.com/forums/showt...hreadid=197283

Any help?
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Old Apr 01, 2004, 01:24 AM
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Also this started off about PICs but had some rx info

http://www.rcgroups.com/forums/showt...hreadid=195327

I think you need a critical mass of interested parties, then you can make the bulk order JMP refers to in the first thread.

I think that the 'inventors' of the small business microreceivers are not keen to see their DIY production flourish, probably because they equate it to a lost sale?

It would be really good if we could get an electronics/model shop to stock the individual components specific to this area.
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Old Apr 01, 2004, 02:49 AM
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http://www.micronradiocontrol.fsnet.co.uk/
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Old Apr 01, 2004, 04:09 AM
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Micron radio

Vintage 1,

They would be ideal, but unfortunately they do not seem to be interested in doing SMD or extending their product lines. I did ask, but hey if they have quite a few enquiries, then they might service the demand.

Any other alternatives?
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Old Apr 01, 2004, 06:58 AM
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DIY Micro Rx

Ok if anybody is serious about making RX22, let us discuss...

the main chip MC3362DW I have...about a dozen...coils no problem...will happy to exchange...with filters and also how to make the PCB cheap...may be iron on method etc etc

Regards
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Old Apr 01, 2004, 07:00 AM
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Okay, okay, I can't stand the pressure any longer.

Re your remarks, fear of losing potential customers isn't really the factor.
I my case (one-man company, doing design, development, production monitoring, post production adjustment, quality control, packing, billing, etc..., and hopefully some flying, not withstanding the family life, all after my normal day job) it is taking care of multiple orders which is the problem.
On the other hand, I remember pestering a Motorola salesman back in the 60's until he gave me his sample of a then new type unijunction transistor (still remember the type : 2N2646), for an own-design transmitter encoder. I also remember that it had to be DIY, and that buying a commercial unit was out of the question - where would the fun have been? -
I am ready to supply a limited quantity of the TK83361M Toko receiver chip and of the matching C49 Murata discriminator (say 10 or 20) to someone who would first have centralised the orders of interested DIY parties. IF filters are not available, being bought in the correct quantity for planned production.
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Old Apr 01, 2004, 07:58 AM
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JMP-blackfoot

If you could over buy the ceramic filter on your next order to make up a matched set of receiver chip/filter/discriminator, I would commit to buying 20 sets. I only want 5 sets for my own experiments and would offer the other 15 sets at cost to other DIYer's. Hopefully this offer will get other folks interested.

Brian
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Old Apr 01, 2004, 08:16 AM
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I'm also interested in trying to have a go

Depends on the cost, but I could imagine trying to build between 3-5 units including disasters.

Johnny,

(AH Intermediate Filters not if filters)

ps I really hopes this comes to fruition

Thanks JMP!!!!!!!!!!!
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Old Apr 01, 2004, 09:25 AM
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These are the parts that I believe are the correct set. Does this sound correct?

TK83361M Toko receiver chip
CDA455C49 Toko ceramic discriminator 455kHz
ELFC455G Toko ceramic ladder filter 455kHz 4.5kHz bw at 6db
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Old Apr 01, 2004, 09:44 AM
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Quote:
Originally posted by vaughan@world.s
These are the parts that I believe are the correct set. Does this sound correct?
TK83361M Toko receiver chip
I found this chip to be much more consistent and easy to use than MC3361. The datasheet gives very good application information.
Quote:
CDA455C49 Toko ceramic discriminator 455kHz
Or the Murata equivalent : CDBCB455KCAY49
Quote:
ELFC455G Toko ceramic ladder filter 455kHz 4.5kHz bw at 6db
Filter or combination of filters of your choice. The ELFC455G looks okay on paper.
In fact, you could even make a simpler and lighter receiver by replacing the IF (Intermediate Frequency) filter with a 0.1 F capacitor, but your selectivity would be poor. I haven't tried it yet, but it has been done before.
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Old Apr 01, 2004, 10:11 AM
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I have been experimenting with super regen Albin designs and with the TDA7021T active filter if design. They suffer from being broad band. This is fine when I am flying alone in the front yard. It is a little anti social in a flying group. This is the reason for my interest in narrow band fm.

I agree with you that the ladder filter adds weight. However it is the key to the narrow band performance. Having never seen a ceramic filter in the flesh, do you know their weight? Does shaving the plastic shell hold any weight savings? Twenty years ago I worked in a small shop where we made hybrid circuits and we had a ball bonder to tie leads to bare chips. Have you heard of Toko or Murata providing the raw unbonded ceramic filters/discriminators?

I don't want to get silly here. I only ask because you might have already discussed this with Toko/Murata or other smaller vendors.

My objective remains: to build a real receiver by modest means.

Brian
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Old Apr 01, 2004, 12:16 PM
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My cross for the recommended Toko CDA455C49 is the Murata CDBCB455KCAY21 with an audio output of 55+-20 mV rather than the CDBCB455KCAY49 with an audio output of 45+-10 mV.

Is the difference a matter of technical choice or a matter of close enough?
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Old Apr 01, 2004, 12:20 PM
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I am up to have a crack at this. 35Mhz for me of course.

I'd probably want to extend it to put a LIPO style BEC and LVC and ESC on it but that comes later..

What I want is as follows

- decent pair of front end filters before the mixer - so little coils it is and a discrete FET RF amplifier feeding a discrete FET mixer. That tales care of nasty intermodulation and most of teh need for DC operation - at 35Mhz anyway. at 72 is a bit different.

I am a bit worried about a single ceramic IF filter - even a good one - as the skirt response always gives a false pair of peaks a few khz out of band. Better sets use another one with a different skirt response to give an overall better result.

Ceramic discriminator is good tho.

I would then think in terms of a PIC to do all the decoding, and drive servo outputs, and some MOSFETS for the actual motor.

If it was a tad heavy, at least getting the ESC on board would help.

In terms of PCB production its not that hard. You can buy resist coated board, inkjet or laser print masks onto film, expose in sunlight and etch with feerric chloride.

I spent about ten years doing PCB design as part of my job as electronics designer, includng RF PCB, and I am pretty good at it, tho I never did SMT before.

Anyway, its not hugely expemnsive tpo get 20-50 boards made up.

The big issues as far as i am concerned are coming up with a stable design, testing it, and sourcing the bits.

Funding such and getting PCB's made is no big deal.

Finding a spectrum analyser and sweep generator is a real issue.
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Old Apr 01, 2004, 12:51 PM
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Quote:
Originally posted by vaughan@world.s
My cross for the recommended Toko CDA455C49 is the Murata CDBCB455KCAY21 with an audio output of 55+-20 mV rather than the CDBCB455KCAY49 with an audio output of 45+-10 mV.

Is the difference a matter of technical choice or a matter of close enough?
The CDBCB455KCAY49 type is recommended for MC3361. The TK83361 is specified as a drop-in replacement for the MC3361 (Not quite true, the demodulated signal is much larger with the Toko part), so I deduced that the CDBCB455KCAY49 is suitable for TK83361. Having tested, built and sold several hundred receivers, I am fairly assured that the combination works quite well. The CDBCB455KCAY21 is recommended by Murata for the Toshiba TA31132 IC, so I do not know how it would actually work with the Toko chip.
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