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462 mhz passive repeaters

merkury187

New Member
Hello, we are using DEWALT DXFRS800 2 way radios which seem to operate on 462 mhz according to the manual https://images.homedepot-static.com/catalog/pdfImages/db/db055560-d26f-433a-bfaa-9222cfd756f8.pdf

We have 2 warehouse buildings which are adjacent to each other with about 2 semi truck+trailer distance apart however they are both made of metal and have lots of warehouse racking so the signal is just barely making it between buildings and sometimes we have to go near a window or go outside to understand what the other person is saying.

Is there a passive repeater set that we could purchase for both buildings that would improve the signal?
 
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unclejed613

Well-Known Member
Most Helpful Member
get two dipoles cut for 462Mhz,(or even better UHF TV 4-bay "bowtie" antennas) mount each on inside a building, and run a good grade of 50 ohm coax cable (one of the following types will be best for lowest loss... RG9/U, RG34 , RG119 , RG120, RG213/U, RG214/U) between the antennas. when you mount the antennas mount them with the elements vertical instead of horizontal.
 

nsaspook

Well-Known Member
Most Helpful Member
75 ohm?
 

vu2nan

New Member
Two external 3-element Yagi beams, facing one another, each coupled with low loss coaxial cable to an indoor inverted ¼ λ ground plane antenna , may help improve the connectivity.

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RadioRon

Well-Known Member
Some educated guess numbers with yagis as shown above:
transmit power, portable
33​
dBm
portable antenna gain, average
-5​
dB
path loss to in-building rx antenna
-80​
dB
gain of in-building rx antenna
0​
dBi
coax loss to roof yagi
-3​
dB
gain of roof yagi
8​
dBi
path loss to other yagi (#2) (50 m)
-60​
dB
gain of yagi #2
8​
dBi
coax loss
-3​
dB
in building antenna gain
0​
dBi
path loss in-building
-80​
dB
receive power
-182​
dBm

You need at least -110 dBm to function, so we need to find about 72 dB more gain. Not sure how to do that. Could start by replacing the two yagis with a single run of low loss coax cable connecting the two in-building antennas. This gets the path loss down to -136 dBm. In this case, it might work when the portables are close to the in-building fixed antennas.
 

vu2nan

New Member
Hi RadioRon,

That's a real eyeopener and I do need to tone down the optimism in my post!

Many thanks.

Nandu.
 

RadioRon

Well-Known Member
Passive repeaters are usually not very efficient, and the idea of cascading two of these will not work. However, if they can stand to run some low loss coax (like LMR400) from one building to the other, and if the buildings are single story, and if they can hang the repeater antennas off the ceiling somewhat central in the building then it might work. My estimate of 80 dB of path loss inside the building may be pessimistic if these are wide open warehouse type structures.

But before doing all that, I'm a bit surprised that two watt transmitters can't get enough signal into the other building that is only a few hundred feet away, but then again, I cannot see all the metal that is in the way. They should check that the portable transceivers are all working at their maximum power?
 

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