Site Radio Advice

[IRW]

Hi folks,

We've got Motorola DP1400's as our site radios (running in p2p mode- no repeater), and there is one particular area in the building where reception is rather poor, so I was wondering if anyone might have any suggestion as to ways to improve this, preferably one that doesn't involve a repeater for X many thousand pounds...?

Range itself is not an issue, as I can go out of the building and a good couple of hundred meters away, but the room in question is particularly buried in a corner of the building (effectively basement area of a new build section of the building, breeze block walls, corrugated metal ceiling with concrete on the floor above, etc etc...)

Thanks,

Ian

[Robin D]

A simple answer is to leave the radio outside the bunker next to an old microphone, amp and cheapie speaker inside. You hear the call but have to go out to answer. Years ago had to do this for a cue in a show to throw in some confetti from a metal gantry that was a first class Faraday cage. 

[Paul TC]

Google the term "passive repeater".   

Simply an antenna in coverage connected to an antenna in the area where coverage is required by low loss coaxial cable.  

However, where the source radio is not a base station may be difficult to get it to work reliably.  

[cedd]

A vehicle set mounted in the room and powered from a 12v mains adapter, with the coax running out to a fixed aerial would work. Just switch it on when you're in there. However there are legalities to consider. I believe Ofcom class a set that is mounted in some way to be a fixed base, which isn't permitted. You'd need to read up on it. 

Is it that you get nothing at all, or that the squelch is too high in its' usual setting? If the signal you're after is there but buried in the noise then you may be able to programme a button on your radios up to switch the squelch level. 

I think you're probably going to struggle to do anything from an RF point of view without some sort of base station or repeater. 

[IRW]

6 hours ago, cedd said:

A vehicle set mounted in the room and powered from a 12v mains adapter, with the coax running out to a fixed aerial would work. Just switch it on when you're in there. However there are legalities to consider. I believe Ofcom class a set that is mounted in some way to be a fixed base, which isn't permitted. You'd need to read up on it. 

Is it that you get nothing at all, or that the squelch is too high in its' usual setting? If the signal you're after is there but buried in the noise then you may be able to programme a button on your radios up to switch the squelch level. 

I think you're probably going to struggle to do anything from an RF point of view without some sort of base station or repeater. 

We do get something in there, but there's enough drop out to make calls unintelligible

[sunray]

7 hours ago, Paul TC said:

Google the term "passive repeater".   

Simply an antenna in coverage connected to an antenna in the area where coverage is required by low loss coaxial cable.  

However, where the source radio is not a base station may be difficult to get it to work reliably.  

Passive repeater is a known thing and can work well as long as it's correctly set-up, the aerials have to be fairly and closely tuned to the frequency in question. Just using a 420-470MHz device is simply not good enough.

 

7 hours ago, cedd said:

A vehicle set mounted in the room and powered from a 12v mains adapter, with the coax running out to a fixed aerial would work. Just switch it on when you're in there. However there are legalities to consider. I believe Ofcom class a set that is mounted in some way to be a fixed base, which isn't permitted. You'd need to read up on it. 

Is it that you get nothing at all, or that the squelch is too high in its' usual setting? If the signal you're after is there but buried in the noise then you may be able to programme a button on your radios up to switch the squelch level. 

I think you're probably going to struggle to do anything from an RF point of view without some sort of base station or repeater. 

My suggestion too. This could be done with a portable radio with external aerial and ofcom would struggle to call it a base station, I suspect Ofcom would not be concerned if you use a mobile set as Cedd suggests if the power and aerial type/performance is similar to that of the portables. I might even suggest a phonecall to them may bring a positive response, I've not found them to be the ogre that many assume.

Edited October 27, 2022 by sunray

[paulears]

The success of connecting 2 antennas together is only ever successful when the field strength in one location is very strong, allowing a feed through to a dead spot - as in a room with rebar in the walls. The success is usually totally reliant on signal strength - so if you have a base station antenna, with moderate output, you can point a distant yagi, with gain at it, then feed that to an omni antenna in the shielded space. If the idea is to 'collect' the RF from low power handhelds at a distance, you cannot use a directional antenna and will totally lose the gain they provide, which is critical. An omni in the 'good' space will capture tiny amounts of RF - passive systems are very lossy and inefficient.I suspect the measly few Watts of RF from handhelds all over the place will just not be enough to make the system work. For what it is worth, a decent second hand repeater need not cost thousands for an analogue system. Budget wise - maybe £700 for a rack mount repeater, a cheap cavity filter and antenna and some cable? maybe a couple of hundred quid. Put the antenna up high and check there is a path to the current dodgy area and everyone gets decent radio anywhere within range of the high up antenna. A licence will cost you £75. Without spending some money, the system will just be unreliable. You'd need reprogramming costs of course.

 

Of course a simple test would prove it - you haven't said if it's UHF or VHF - but two dipoles and a bit of cable will prove very quickly if it works, or sadly, doesn't. The antennas just need to have your frequency centre of their band where they are the most efficient.