Low voltage RF operated switch

Thread Starter

shezza

Joined Mar 19, 2014
66
So there are thousands upon thousands of these around, most of them are quite low range, regardless of their claims. Basically, Dad's garage door isn't easy to find remotes for, so the easy solution is to connect a RF low voltage switch across the wall switch wiring. I bought him one a while back, but the range was dismal. I was wondering what the trick is to finding a long-range one, without just looking for one that costs triple figures? Is it more in the transmitter than the receiver? Or it really quite equal?
 

AlbertHall

Joined Jun 4, 2014
11,506
Positioning of the aerials is very important.
If the door is metal, the receiver will likely work better if the aerial is outside the door.
 

Thread Starter

shezza

Joined Mar 19, 2014
66
Thanks and toda Yaakov!
I only need 100m range. Though 50 obstructed or thereabouts.

So it is in an open-air position. All the cheaper receivers have tiny coiled-up wire. Is getting a real antenna and attaching it of great use?
 

Yaakov

Joined Jan 27, 2019
3,523
Thanks and toda Yaakov!
I only need 100m range. Though 50 obstructed or thereabouts.

So it is in an open-air position. All the cheaper receivers have tiny coiled-up wire. Is getting a real antenna and attaching it of great use?
A good antenna can make a very great difference. This one looks good, and has an SMA connector with a small antenna on it. If it wasn't enough you could replace it with something better, like this.
 

Janis59

Joined Aug 21, 2017
1,350
My few cents are probably for direction contrary problem.

Always have be wondering WHY the prost DC relay costs 1 Eur but relay qualified to switch the antenna sometimes to transmitter, sometimes to receiver - costs 2000-3000 Eur. If find one cheaper, whistle please to me, while I am using to switch on boat by means of screwing down the PL259 plug and changing to other and then back, forth and back, forth and back until loss of conscious.

Antenna to 25W VHF radio; Antenna to 2W AIS service; Antenna to anti-thunder grounding. Once even tried what will happen about if use ordinary tumbler instead of inquisition with plugs. Loss factor was 100% detrimental, of course. What I would like, it is under 100 bucks beer cup sized hook on the box with three 50 Ohm terminals in one side and one in another side.
 

andrewmm

Joined Feb 25, 2011
1,757
RF relays are expensive compared to DC/AC ones because
a) there are many less made, so little scale
b) they need to carry RF , with matched impedance, which is not easy
c) RF jumps gaps, you want isolation between the points of many dB's, a AC relay only needs about 50 dB at 50 Hz.

If you want to play, they dont have to be thousands of dollars,

https://uk.rs-online.com/web/p/high-frequency-rf-relays/0351459/

https://uk.rs-online.com/web/p/high-frequency-rf-relays/8154962/

depends just what you want
 

Janis59

Joined Aug 21, 2017
1,350
RE: Andrewmm
Thanks for the links but not seems they be able to stand for 175 MHz 25W what ultimatively demands a coaxial input/output otherhow full blow-back. I have seen much of technics marked as "very high frequency" and when search deeper it was meant the 400 Hz. For such frequency the relays shown in pictures are better as best, for sure, maybe even kHz scale.

For clarity: 25W 50 Ohm means 35 V and 0.7 A of pure 170 MHz
 
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