5 replies to this topic

[jdm66]

Hello

I opened my RX Lawmate 2.4 ghz and here is a picture of the filter.

The reference is F 480-1.

I can not find the data sheet for this component

Is it necessary to change from that of DPCAV, D480A ?.

thank you for your technical support

jdm66

Attached Thumbnails

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Edited by jdm66, 21 December 2011 - 01:55 PM.

[Mr.RC-Cam]

The reference is F480-1. I can not find the data sheet for this component

http://www.actcrystals.com/_files/franchise/Advanced_Crystal_Technology/datasheets/ACTF480-1%20480_0,TO-39-2.pdf

[JetPilot]

I was hoping to see the answer to this question... Will the D480A SAW filter increaese performance in this receiver. I looked at the Data sheets, and the origional SAW filter shows a 21 DB insertion loss, while the D480A is around 19.5 dB. Is this worth doing ?

Mike

[Mr.RC-Cam]

Will the D480A SAW filter increaese performance in this receiver.

In this example the original SAW filter's bandwidth (~18MHz) is about the same as the popular ECS-D480 upgrade filter. So upgrading it is not expected to earn any extra points.

FWIW, the SAW upgrade will generally help a 900MHz -1.3GHz Rx since most have a 27MHz wide SAW filter (which is wider than we need for FPV video). But a typical 2.4GHz A/V Rx would rarely have a wide bandwidth filter in it. That is because the 2.4GHz designs were not used in satellite TV applications like the 900MHz - 1.3GHz Rx modules were designed for. But regardless, an inspection of the original SAW filter's part number is the place to begin.

I looked at the Data sheets, and the origional SAW filter shows a 21 DB insertion loss, while the D480A is around 19.5 dB. Is this worth doing ?

The insertion loss spec is not a huge concern in our application. The SAW filter upgrade trick involves reducing the RF bandwidth.

[megabyte]

I've heard that the video link needs ~14MHz of bandwidth, yet Wikipedia says the PAL and NTSC signals only use roughly 4 to 5MHz of bandwidth, and that's for 625 lines. I'm wondering if 18MHz is overkill? Maybe we could get by with less bandwidth for our 520 line FPV cameras?

Hypothetically, a 15MHz or even 8MHz SAW, it might make a replacement mod worthwhile IF we had a quiet flying site, and the signal was usable. Before I waste my time chasing down unobtanium parts, can you suggest what the outcome might be if we did use a SAW filter that was too narrow? Could we get better range at the expense of video quality, or am I over simplifying things?

[Mr.RC-Cam]

I've heard that the video link needs ~14MHz

On the 900Mhz-1.3GHz systems the audio sub-carrier is 5.5MHz from Fc, so minimum required A/V bandwidth is ~11MHz; A 12MHz filter would be nice.

Could we get better range at the expense of video quality, or am I over simplifying things?

That is certainly an option. As long as you maintain sufficient RF bandwidth you will not seriously harm the video quality. Budget 1MHz BW for every 85 lines of required visual resolution.

BTW, I will be testing a narrow bandwidth (~8MHz) SAW filter later this month.