VHF 150-174MHz
During the summer I work as a lookout for the Forest Service sitting in a tower about 4600ft above sea level. Frequently I work with firefighters either in the air or down in valleys as low as 1200ft that use tactical channels that are line of sight rather than bouncing off the repeaters in the area. With the equipment in the tower I'll often get half of conversations, which is pretty frustrating when trying to keep in the loop.
Currently I'm trying things out with an RTL-SDR v3 kit with the dipole antenna at about 0.44m each end, and attached though an FM (88-108MHz) and an AM (2.6MHz) blocker. Additionally I have it going through an LNA (50MHz-4GHz).
Focusing on receiving, specifically in the range of 151.19 to 173.7625MHz, what are the next steps to improve by gain and range?
I've removed as much potential electrical interference as I can (though there are still telecom towers right next to me), and I'm thinking on putting up a larger omnidirectional antenna and maybe some Ferrite beads for good measure.
Any other suggestions?
Posted Oct 4, 2019, 4:02 AM UTC
For those frequencies you don't need to use the AM filter, that's probably reducing reception as it's being used at out of spec frequencies. And at those frequencies an LNA might not be that useful, and might make things worse, unless you are using a long run of coax cable. Try it with and without the LNA.
My recommendation: Put the antenna up as high as possible with an unobstructed 360 deg view. Have the LNA at the antenna and BCFM filter before the LNA (closer to the antenna), then run some coax to get it to the radio. Or use a USB extension cable and get the dongle by the antenna and don't use the LNA.
If you have telco towers next to you, you might be getting interference from some frequency other than the broadcast band. In that case i'd recommend building yourself a 151.19 to 173.7625 MHz bandpass filter.
Things definitely seem better with the LNA vs without.