Antenna spacing between HF and 912 mhz

[AJAT]

I have a tower with a 3 beam yagi about 35 feet in the air on 20 and 10 meters, 100 watt max. I want to add a LoRa 915 MHz antenna for a Meshtastic network on the tower. How far below the HF antenna would you all recommend I mount it? I am afraid I might over power the Meshtastic board and fry it.

 

[mmckenna]

Hopefully the 900MHz radio should have some sort of filtering on it to reduce out of band signals. HF is far enough away that it should be fine.

Not sure how much spacing you need, but since the 900MHz is vertically polarized and the HF beam is horizontally polarized, you have some additional attenuation there. I'd try a couple of feet and see how it works.

 

[merlin]

I had a 440 Yagi about 4 foot below an HF horizontal longwire feed point. As much as 250 watt HF and 100 watt UHF, neither had any effect on the other.
I don't know about the front end protection on the Meshtastic board, but a low pass filter in the HF line and 900 MHz pass filter for the
Meshtastic, mayby little or no desensing between the two.

 

[AJAT]

Thanks for the replies. I will put it up a few feet below and see what happens. Worst case it fries the board and I am out $23.00 or to be an Optimist. I learn something new for $23.00.