OpenGD77 vs MMDVM hat

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KO4BFY
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OpenGD77 vs MMDVM hat

Post by KO4BFY » Sat Feb 08, 2020 9:48 pm

Is the GD77 is a better match with the Pi for a hotspot than a hat? I'm looking to set up a pi-star for my wife's sewing room as soon as she has her ticket (March).

VK3KYY
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Re: OpenGD77 vs MMDVM hat

Post by VK3KYY » Sat Feb 08, 2020 10:14 pm

The MMDVMHS is multi mode, the GD77 is DRM audio only

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kd2lh
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Re: OpenGD77 vs MMDVM hat

Post by kd2lh » Sat Feb 08, 2020 11:28 pm

The GD77 is a DMR radio, and as such only operates over RF using the DMR protocol. That said, it does (in my humble opinion) have better audio and is more tolerant of multiple radios that connect to it with sightly offset frequencies (because the GD77 has AFC).

Understand that the OpenGD77 hotspot mode is still in development, at a level I'd estimate to be toward the end of alpha and close to a beta. It is functionally rich and with the last version is stabilizing. When a GD77 (which can provide higher power - but with care as the duty cycle is high, and the radios may not be rated for that) you can also unplug it and use it as a portable when you need to.

The JumboSpot MMDVM-HS-Hat based hotspots are very compact, self contained, with multiple digital RF modes supported (the software defined radio can alternate between digital modes) and moderate reliability. I have lost the Oled displays on two of mine, having failed in about 9 months of usage - and one of them has started to drift probably due to deterioration of the clock chip.

You can also get duplex JumboSpot MMDVM-Duplex Hat versions that can operate on both time slots simultaneously when they are in DMR mode.

KO4BFY
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Re: OpenGD77 vs MMDVM hat

Post by KO4BFY » Sun Feb 09, 2020 11:36 am

That's made it clearer, thanks and 73s.

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EB3AM
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Re: OpenGD77 vs MMDVM hat

Post by EB3AM » Sun Feb 09, 2020 10:44 pm

Hi, I have a HAT Duplex, and also a GD77. For home I use the Hat, since it offers me both slots. But the GD77 I have it connected to the external antenna, with 4W of power and in VHF it gives me a great coverage, of several km around.
Yesterday, for example, I ran the entire TG91 BM worldwide NET, which lasted a couple of hours. The GD77 supported it without much trouble. The outdoor antenna has no SWR. :roll:
Jordi, EB3AM, Talarn JN02ke, Catalonia.

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kd2lh
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Re: OpenGD77 vs MMDVM hat

Post by kd2lh » Mon Feb 10, 2020 12:12 am

Like all different implementations of technology, the different products will have advantages and disadvantages in different usage contexts.

While the MMDVM HS-Hat based simplex and duplex hotspots make great units for home or within a moving vehicle, the GD-77 provides additional range and a higher power for an antenna connection with a run of coax.

As we the developers pass this stage of work, I expect the GD-77 hotspot implementation will become quite popular, especially considering the portable radio's dual use and the low cost of the Raspberry Pi (a PiZeroW with 8gb memory card and power supply is under $30 in most places).

This is an extraordinary project.

Marc

KO4BFY
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Re: OpenGD77 vs MMDVM hat

Post by KO4BFY » Mon Feb 10, 2020 2:17 am

I'm looking forward to trying hotspot mode out. I'm currently running a Pi/Pi-Star with a single antenna mmdvm hat which talks to an Anytone D878UV. I'm a rank dmr noob, so I don't understand what advantages a dual-antenna setup has to offer. I've ordered an additional Pi 3B for testing with OpenGD77. I have no interest in modes other than dmr. 73s!

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