Weather Station Hardware > Rainwise Weather Stations
increasing range of 418Mhz Mark III with antenna mods?
DaleReid:
I helped a friend set up a 'spare' Mk III, non-LR station at his place. House has metal siding. The location of the station sensors was in his garden, about 150' away, line of sight, nothing in the way between it and his receiver module which is in a window where the sensor station can be seen.
Most of the time all is well, but occasionally, even with a fully charged nearly new battery, the dreaded dashes of no reception appear.
I know that at higher frequencies yagis can be helpful, and some lines even have these. With this design the antenna seems to be an end fed whip, no coax connection.
Has anyone found a trick to increase gain enough to be worth the trouble for the older Mark IIIs? There is only one receiver and if there was some trick to make the antennas directional it would certainly help.
Thanks for any chatter or comments on helpful tweaks. I mention antenna mods since that seems logical but there might be other things to try (short of a linear amplifier on the sensor suite's output.) And I'm not ruling out trying other tricks for the receiver mod antenna,either. It's just that the location in the garden is about the only one, and now the ground is frozen, along with the spot in his kitchen where he and his wife agreed that the display can go ties my hands a little bit in moving around for a sweet spot.
Dale
dupreezd:
Dale, if the station comes equipped with a helical coil antenna, you might be able to replace it with an external mounted whip antenna such as this which have more gain (typical 2 - 3 dB).
The nice thing about this one is it comes with a piece of co-ax attached.
http://www.glolab.com/antenna/antenna.html
DaleReid:
This one has a long (1/4 wave) antenna hanging down out of the bottom of the weather resistant enclosure. Darn.
WVZR-1:
I could get excited about an antenna improvement myself. I do believe that Richie did have me change mine when we did the install. Mine is a Mark III from maybe '05 that was shelved for many years and I bought NOS in maybe '14 or '15.
miraculon:
With my Davis long-range repeater, I used a mini-circuits LNA. My particular model doesn't cover the 418MHz frequency, but I found a model on eBay that does: Mini-Circuits-ZFL-500HLN
It will give you 19dB of gain.
Also, I was able to extend the range of my garage door opener with a Ham 70cm yagi. The GDO was a bit lower on frequency, but apparently the antenna had enough bandwidth to help.
I modified the PCB where the wire antenna came from to add a SMA female socket. Then I ran a SMA male to a N-connector at the antenna. If you get the amplifier inline, you would need a SMA-SMA jumper cable. The only issue that I see is that the mini-circuits amp draws 110mA. If you could get power to where the Mark III is, this could work. (I feed 15VDC from the garage up the mast to the repeater pre-amp). I also have a 902-928MHz passive filter in line to eliminate some local interference. I don't know if you could find a similar BPF for 418MHz.
Otherwise, maybe a substantial solar/battery rig could run the preamp.
Greg H.
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