RXOffset on a JumboSpot/ChinaSpot

MMDVM_HS Hat hardware
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Re: RXOffset on a JumboSpot/ChinaSpot

Post by KE7FNS » Sat Jul 27, 2019 1:51 am

KN6CXC wrote:
Fri Jul 26, 2019 1:29 am
Any suggestions on the RXOffset?
Use pistar-mmdvmcal and figure out the correct setting. There isn't one magic number across the board, every radio and every MMDVM are off by some amount.
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Re: RXOffset on a JumboSpot/ChinaSpot

Post by KE0FHS » Sat Jul 27, 2019 12:32 pm

FYI, Daniel, K9NPX, has a good article on using MMDVMCAL to get more exact RXOffset (and TXOffset) settings for a DMR radio:
http://www.k9npx.com/2019/02/hotspot-of ... n.html?m=1
73, Toshen, KE0FHS
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Re: RXOffset on a JumboSpot/ChinaSpot

Post by kd2lh » Fri Aug 30, 2019 9:34 pm

Be picky about the vendor you're acquiring a Chinese made JumboSpot MMDVM HS Hat from (either simplex or duplex versions).

Be sure that they are using a quality, and preferably US made reference oscillator chip. These tend to be more temperature stable. Look for boards that properly manufactured to comply with the opensource standard board.

Use a consistent packaging, preferably something metal that can passively dissipate heat. I have the tiny Raspberry Pi Zero-W board running both simplex and duplex style MMDVM HS Hat boards in compact metal cases.

I have several of these running, and they all have slightly different MMDVMCAL tested offset frequencies.

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