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M6HSB
Wed 18th Jun 2014, 17:24
Hi guys

Got a bit of a project in mind to give me an excuse to go out and buy an arduino kit as its a toss up between this and the pi I think this will fit me better.

What I would like to know is what options there are for VHF transmitter boards. I don't need too much output but more than a few mw would be nice I have seen one that will put out 300mw but would like to get into full watt figures if I can and will be used purely to TX data

Anyone out there know of anything that could fit the bill

Paul

5B4AJB
Wed 18th Jun 2014, 21:46
Can't you just add a linear amplifier? I'd put a bandpass filter between the two as well...

M6HSB
Fri 20th Jun 2014, 17:15
Thats an idea but end game is to have it all self contained in a portable box able to just plug in 12v option for ext GPS and VHF and leave it there doing its thing. But will look into options for an amp as max output needs to be under 10w

Ideally id like to be able to keep it as neat and small form factor as possible.

Thanks for the ideas thought

5B4AJB
Fri 20th Jun 2014, 18:01
A linear is a pretty straightforward (http://www.m0ukd.com/2N6084_144MHz_Power_Amplifier/) device.

I have an old Motorola single channel handheld, recrystalled for 70cm packet, in a box with a small linear built inside.

There is room for batteries, but I never fitted them...

M6HSB
Fri 20th Jun 2014, 20:22
cheers ill take a look

Sparks1973
Wed 10th Jul 2019, 15:27
My son lives 500 miles away from me and being prepper. the thought of him in a rid down situation just kills me. I would like to set up a lora message system and voice over ham to be able to communicate with him and others. how many meters wave length with what sort of linear amplifier and antenna should I look at that is both compact compadable with a Shield?

brandon lind
Mon 15th Jul 2019, 14:01
Even using lora, you are not getting 500 miles out of a 10w VHF transmitter reliably. For VHF to work that far (without legal limit power and a prohibitively expensive antenna array and feed line) you would need to have an extensive knowledge of RF propagation and a keen eye on the weather. It is an absolute mystery to me why preppers (im one too) always jump straight to VHF for their communication needs when HF is super reliable for DX work... Actually prepping for a communications blackout will require far more than an arduino and a few youtube videos, no offense intended.

Heck, even CB is more reliable for 500 miles than what you wish to do. Get an HF radio/license and study radio wave propagation. Each band is specific in how it refracts or absorbs in the various layers of the ionoshpere (for HF) or atmosphere (for VHF and up), which is why the military use radios that periodically probe the ionoshpere back and forth and automatically set to the best frequency for a given scenario. At 500 miles, scrap the whole VHF idea.