[NLRS] Thoughts on VHF-UHF beacon hardware.

[Doug Reed]

I've been debating with myself what might be the cheapest way to get a
VHF-UHF beacon on the air without having to dedicate an expensive SSB
rig to the task and without buying crystals. I keep coming back to
using modes like CW or PI4/JT65/WSPR that work with a Class C RF
amplifier, then use an old FM mobile as the TX and power amp. You can
use crystal control, but crystals are getting difficult and expensive
to buy. But it is fairly easy to do if the beacon controller also
provides the frequency control and stability. The HansSummer.com
Ultimate 3S controller can handle all of that, especially with the
optional OCXO SI5351A oscillator and using GPS for frequency control
and timing.

I've been a bit more worried about how to do propagation RX monitoring
from the same site, if I wanted to.... The FM receiver is useless for
that, but with the SI5351A oscillator acting as a LO for the receiver
front-end and mixer, I could feed the IF out to a "cheap" HF receiver
such as a SoftRock, Minima, Pixie, or even a CB SSB radio. Anything
that receives CW or SSB would work to feed audio to the sound card RX
software for decoding. Another option would be to just use the FM
receiver front-end as a filter with a RTL-SDR dongle as the
receiver....

If anyone wants to try this or other direct keying mods to build a
beacon site, VHF and UHF crystal-controlled mobiles are available
pretty much for the hauling. Nobody wants to buy crystals. 6M is a
little harder to find because you have to be sure you get a "high
split" radio.... In fact the problem may turn out to be that many or
most of these mobiles are 110W radios and they seem like a bit of
overkill for a beacon....

One thing to remember, the FM mobiles were designed for intermittent
duty, around 20% TX. Unless you reduce power, add fans and heat
sinking, or built an intermittent TX beacon, you will have problems
with overheating the TX. OTOH, I have successfully modified a 110W GE
mobile to run FM repeater continuous duty with just extra heat
sinking. I then added fans to be 100% certain and it ran for about 15
years before being replaced with newer equipment.

73, Doug Reed, N0NAS.