Garage Door Opener Range.

That's a lot of speculation and maybes. How about he look at what he has and goes from there. I'll bet it is one of the single chip code hopping solutions from any one of a bunch of manufacturers and I doubt that it will be a super- regen anything. And, he didn't say that he cared if the FCC might not like the mod.

Where?

I'm curious how you calculate these values?

Does that leave two wires a crook could short to open the door? Important not to forget the "other" reason for a door opener...

Many thanks for the info.

Sorry. Here's the missing link:

The VSWR and Efficiencies are show in the "Main" page. More on radiation and power efficiency:

Depending of your size constraints, even -10 dB or -20 dB antennas might be acceptable.

Of course, no such constraints should exist for a fixed, big (garage door) antenna.

I got one for my dad's gate, his Door remote was branded Dominator, so, probably uses a different code sequence to Genie. I can't spot the receiver modiule on-line (I got mine over the counter from the Dominator agent).

OTOH you could just get a 433MHz receiver module and a transmitter replace the transmitter antenna with something worse than what it comes with abd wire them together far enough apart that the receiver can't see the transmitter,

that confirms it's a "antenna in a metal box" problem

I'm thinking that be the eqivalent of about a 4" window in your door.

It'd work better if the indoor antenna was closer to the receiver. I'd be considering putting the indoor antenna in the near field of the receiver antenna. (but only after rejecting a direct connection to the receiver circuit)

You've got inverse square law losses between you and the outdoor antenna and again between the indooor antenna and the receiver.

Moving the indoor end of your passive repeater to where it does most good has got to be good for a 30db reduction in loss.

I like that one (for no obvious reason because there are no specs).

Is the metal part of the garage door insulated from the metal support frame? Usually, that requires rubber or plastic wheels in the door track. If so, you might be able to simply connect the antenna connection to the overhead track arm, which is connected to the door. The idea is to turn the metal door into an antenna. It won't be efficient, matched, kosher, elegant, or otherwise according to the textbook, but it will put the RF on the outside of the garage, which methinks is the basic problem. Try it with a clip lead and hope that the receiver tuning is sufficiently isolated from the antenna to not become detuned (or oscillatory). My only worry is that if someone dumps a static discharge into the door, it might blow up the receiver front end.

Oh-oh. Kinda looks like BFT no longer sells a BFT-1. Nothing on their web pile: No manuals or any reference to a BFT-1 on their site.

Interesting thought. A schematic of the controller board would be most helpful. ...Jim Thompson

How many have you worked on?

You might find a schematic on the FCC database. Some items include one in the OEM's filing.

If you looked at the PDF I posted, it shows how to remove the controller/transmitter pcb. Take it out and see how complex it is. You know how to draw schematic, I can't read them, but you know how :-) Mikek Mikek

Heh heh heh.

Thanks. I'll have to get a version that works for me (on Mac).

I was curious that the VSWR seems to go roughly as the inverse third power of length, which made it seem like a simple formula could approximate it.

Clifford Heath.

First of all, you need to kill the reactive impedance, for a short antenna with a suitable inductance.

Secondly, you need to match the antenna impedance (in a small antenna usually a few ohms) with the receiver/transmitter 50 ohms resistive impedance.

A pi (series L with C to ground) or a T (series C and L to ground) will do the trick for a narrow band application.

One more than you have.

If that were true, you would know how sensitive the front end is to detuning. The additional capacitance of coax would take it out of band without reducing the inductance in the tuned circuit. BTW, I repaired hundreds of the damned things for a garage door company that was owned by a friend. I repaired stuff from early tube designs, up to rolling code. From single function, to specials models that controlled eight doors for firehouses.