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Originally the Fatshark, IRC modules have 6 channels (5740, 5760, 5780, 5800, 5820, 5840, 5860). When we activate the SPI we get 20 or 30 channels on several bands. The fact of having more channels, does this reduce (or otherwise) the bandwidth of each channel?

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The original FatShark (FS) and ImmersionRC (IRC) 5.8GHz modules used vRx modules with the Taiwanese Airwave chip. They were limited to seven channels. Airwave's published video bandwidth was  approximately 5.5MHz. But in practice it was typically less than 5MHz.

All the current FPV 5.8GHz vRx's (including FS and IRC NexWave modules) have the Chinese Richwave chip. It supports a 5725 - 5865 MHz frequency range. Its SPI mode allows controlling the frequency with a couple MHz resolution. So that is why so many operating frequencies are possible.

As far as I know Richwave does not publish a video bandwidth specification. But I think it is safe to assume that the bandwidth remains the same on the various frequencies. The practical video bandwidth will depend on the module's implemented design, component placement (board layout), and build quality. So you will have to measure your module to determine its real video bandwidth. I suspect that most modules offer something between 4 MHz to 5 MHz.

 

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So the new FS or IRC modules are no worse than the first models?
I opened two modules, an IRC and a Fatshark but I did not find the settings knob to adjust the video output level. How do they adjust this value?

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So the new FS or IRC modules are no worse than the first models?

On paper, the specs are similar. But in reality, the newer modules have proven to perform better. Range testing shows RF sensitivity has increased. Also FS/IRC compatibility with other brands has improved because the original Airwave modules used different video de-emphasis. De-emphasis on the NexWave is now similar to the other Chinese brands.

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I opened two modules, an IRC and a Fatshark but I did not find the settings knob to adjust the video output level. How do they adjust this value?

Correcting the video level is the responsibility of the external circuitry. Before 5.8GHz was introduced it was common to find a video level adjustment POT either inside the module or externally on the main PCB.

No, they did not solve the reason for the video level POT. Instead, the designers decided that reducing their manufacturing costs was more important than giving us accurate video levels.

Some FPV users that are suffering bad performance are unaware that their video issues are due to incorrect video amplitude. This problem continues to be ignored and it is difficult for the average FPV consumer to troubleshoot.

 

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I cannot offer any specific advice on changing the video level of the FS or IRC module. I would need the video circuit schematic before offering a solution.

 

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It is surely the kind of thing not found on the Internet, I guess?

I would also like to have the schematic of the FR632 but I did not find ...

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It is surely the kind of thing not found on the Internet, I guess?

They are not open source hobby projects. Instead, they are proprietary designs. So the manufacturer does not publish the schematic.  This is suppose to prevent the competition from cheating by cloning their work, but rarely stops the problem.

A determined person can create the schematic by reverse-engineering the device. It's a lot of work to do that accurately. A lot of cloned products are bad copies.

 

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I would like for pleasure, make myself a 5.8ghz video receiver. In your opinion, should I use the Fatshark / IRC or RX5880 module?

 

 

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The most common choice is to use the Boscam RX5808 module. It is very low cost and widely available. 

There have been reports that the RX5880 has slightly better performance.  However I don't believe that the bare RX5880 module is readily available. If you can't find a supplier then the workaround would be to purchase a FR632 and unsolder the modules in it. Not sure if this is worth the effort, that decision is up to you.

 

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I have a FR632 and a RC832, both use the RX5880 but I am going to modify the RC832. I will include the THS7314 circuit, as you show here:

I would like to use sms components for capacitors and resistor as for the THS7314.

Is it possible? And if yes, what would be the references?

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I would like to use sms components for capacitors and resistor as for the THS7314. Is it possible?

If you look through the HeadPlay HD Goggle Upgrade discussion you will see a photo of a SMT board created by a forum member. Maybe the photo will give you some inspiration.

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