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wmacky1

Receiver Project. Experts needed!

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I'm in the process of assembling a "Super Receiver". I'm recasing one, perhaps even two lawmate receivers into a larger instrument case, and adding a LCD digital frequency controller board. This lcd controller was meant to be used with Comtech receivers, and the intructions state that the receiver's original freq control PIC must be removed or damage may result. The Pic is identified and socketed on the Comtech unit, but the lawmate will be trickier. Thomas has interior pics of the Lawmate Receiver on this page.

http://www.webx.dk/rc/video-wireless/video.htm

I believe the Processor in question is located on a subboard which is on the underside of the lawmate? Is this right?

Does it control more then freq selection on the lawmate?

Should I remove the entire subboard or just cut the connections @ the processor?

What if I were to break the connections between the SDA and SCL pins from the module to the main board? Would that work just as well?

Next issue: Could I run the SDA, and SCL lines from the LCD controller to the proper module pins on TWO different receivers, so that a diveristy system could be implimented?

Thanks!

Edited by wmacky1

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Does it control more then freq selection on the lawmate?

If it is the usual freq synthesizer, the I2C interface will control the freq divisor registers and other things like the charge pump. It also will be able to read the status of the phase lock and other registers.

What if I were to break the connections between the SDA and SCL pins from the module to the main board? Would that work just as well?

That sounds like a low risk method to me.

Could I run the SDA, and SCL lines from the LCD controller to the proper module pins on TWO different receivers, so that a diversity system could be implemented?

It seems to me that in a perfect world, this trick might work. However, if the two modules are not identical and perfectly synchronized, the status bits that are read might not be the same and so they could become corrupted when Or'd together. If the host controller's firmware never cares about the status values, then it just might work. So, success would depend on the host and luck. Personally, I would control them independently unless you have technical info that states otherwise.

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Thanks for those thoughts. Could I also ask what are the exact dimentions of Oracle system board? I have thoughts of intergrating it into my receiver. I'm guessing the prospect of obtaining one of these without the RCA connections pre soldered would be low!

All other comments about this project are very welcome! Don't be shy!

Edited by wmacky1

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what are the exact dimensions of Oracle system board?

The board, less RCA's, is 5.7"D x 3.9"D x 0.7"H. The push switch overhangs the front edge about .2" too.

I'm guessing the prospect of obtaining one of these without the RCA connections pre soldered would be low!

I get 'em with the connectors installed, so everything I have includes the RCA's. But, you could unsolder them (not a horrible task). If you need an Oracle without the plastic case, then PM me to work something out.

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Ok I'm moving ahead. I emailed the vender about connecting 2 receivers to the Lcd Freq controller and this was his response:

"Hi,

I check and you can't connect the simply parallel you need to do some

more work. One receiver should go direct to the SCL and SDA of the tuner

module the second one should go through NON--INVERTING buffers, output

of the buffers go to the second tuners SCL and SDA pins"

Can anyone spell that procedure out for me with appropiate parts? I'm a great assembler, but I have no engineering skills. Do I use some type of chip for that job, and do I need separate buffers for both SCL, SDA lines? I don't know anything about buffering, but I can build it If instructed how.

Edited by wmacky1

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I don't quite understand why you are trying to do what I think you are trying to do. The digital frequency controll boards from Mobicom are designed to be used on their RX boards. The Mobicom rx board already allows tuning of almost any frequency in the band using dip switches. A digital controller board selecting the frequency makes me nervous. If a stray signal or power spike causes the rx to jump frequency, a plane could be lost. Having dip switches seems much safer. I tend to pic a frequency and then leave it alone.

Adapting one of these controllers to the lawmate rx seems like overworking the problem since mobicom and lawmate both use the same comtech cans, at least in 2.4ghz and therefore should have similar sensitivity. The lawmate RX is smaller, but one you add the controller, the size isn't as much of an issue.

As far as mobicom, I have bought from him, and everything showed up in a resonable time.

Best of luck.

Ken

Edited by Lupy

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I already have the controller, and it is a nice looking device!

Why?

I want a diversity receiver that can easily be tuned to any 2.4 transmitter. And Yeah, because it will look nice ;)

I'm going with lawmate as I do need the smaller form factor for my purchased case! I have a RSSI diversity board ready for mounting. I only need to resolve this last issue, and I be golden!

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One receiver should go direct to the SCL and SDA of the tuner

module the second one should go through NON--INVERTING buffers, output

of the buffers go to the second tuners SCL and SDA pins

Here is what they are saying:

Using a 74HC04, connect two of its inverters in series. This will create a non-inverting buffer. Next, connect this buffer *between* the SCL of the "host" A/V Rx module and the SCL input of the slave module. Repeat by adding another non-inverting buffer to the SDA signal on the slave module.

I recommend placing 470 ohms in series with the slave's SDA input so that it is somewhat isolated during the slave's ignored data response bits.

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Thank you!

It's sounds like the chip has several inverters. So I can use four of them doubling up 2 and 2 from a single chip? Now I just need to figure out the pins.......

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Yes, inside the IC there are several inverters. The 74HC04 IC data sheet will get you on your feet.

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