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View Full Version : Feedback on TX RX wireless modules for RS-232



sachin_surendran
11-30-2008, 07:52 PM
I happen to buy this set of TX RX modules from :

http://APLUSindia.net

And I am seeing dismal (very very bad )results with this Modules

The modules I bought are

1. SM-FRX-01-FSK

2. SM-FTX-01-FSK

I brought a TX- RX pair.
It barely works at 300 Baud, out of every 100 bytes I sent, i get to
receive about 1-5 bytes.

I have made the antenna for 433MHz and cut the wire right size for it to work as a quarter wave antenna. Inspite of all these, even if I get the
TX RX antennas as close an a 1cm, still the performance sees no improvement.

Seems I lost my 500 bucks I put into these.
I thought of spreading the word so that others are cautious before they
go for a buy.

Sachin

a7400
12-01-2008, 09:51 AM
hey sachin

theres a work around to this... Never keep your line idle, keep sending a dummy character for keeping the line synchronized

eg: dummy character = 'X'

Data stream = XXXXXXXXXXXXXOWRXXXXXXXXX

and at receiver end only read the values excluding the dummy character.

I have achieved a speed of around 1200bps with ASK modules like these...but not the FSK ones. mebbe worth a try[/b]

sachin_surendran
12-01-2008, 10:15 AM
I am giving that approach a shot,
I will post the results here after im done.

Thanks
Sachin

sachin_surendran
12-02-2008, 10:48 AM
I tried the approach of sending data continuously,

Result: Not a significant improvement

Then I tried sending data in Manchester format

01 for 0
10 for 1

That was showing an improvement, but was none the less
unreliable.

Conclusion: If I send patterns like 0x55 and 0xAA , which has alternating bits, The Success in Receiving the pattern is 80%+ .

But for all the other data it is very susceptible to errors. The overall performance being bad.

My Feedback on the Module: I would give a POOR verdict to the FSK module. After the results of all the above experiments.

Thanks for your inputs a7400.

Sachin

a7400
12-02-2008, 12:00 PM
option 2.

Add a start frame haveing data 0x55 and then ur actual data... u can discard the start frame at the receiver end.

a7400
12-02-2008, 12:01 PM
the only thing thts good about these modules is the cost..
These are also very susceptible to noise due to mobile phone signal ... all in all not a gr8 package