Garage Door Opener Range.

Well, I sit corrected. Thank you. I'm obviously going mad.

Not necessarily. The authorities will generally shut down the cell network in that area should the possibility of such attack manifest itself.

Perhaps but the reliability of GDOs is pretty bad. If the authorities find it, it's a failed attempt. I certainly wouldn't stand around an IED with a GDO trigger, either.

Disregard total Bollix!...

Err No!,

I'm getting rather forgetful in my olde age!. You were right I've written off several years of TV engineering and Charles Hope can't have been reading this thread else he'd have picked me up on that!>

Some were dipoles but there were slots the "EMISLOT" made by EMI as implied!.

Herewith some pix of same from the Stockland Hill transmitter in deepest Devon taken when the digital switchover was in progress. Oddly enough the engineering notes of the time when they went into service refer to them as panel's which you could call them that, but I don't think anyone did!.!..

Sorry!...

And a close up here at Wenvoe in Wales!..

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

Do you have any source of interference in the garage like flour cent lights or battery charger? I have a cordless phone in the garage. When it is on a charge cycle the opener has a range of 20 feet. Not on a charge cycle about

Hmmm. I'm guessing if you hooked one of these up to your garage door, you'd have no range problems at all.

Not sure about "reliability" - more a case of sensitivity and selectivity which I agree they're pretty hopeless for, certainly the higher the frequency goes. They were probably just the job for performing checks on the BBC's Aspidistra transmitters, though!

Well, in this case, "reliability" includes keeping the door shut until you're not standing next to it.

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.

That was certainly true of previous generations of remote control receivers. I fixed a few of those (mostly by retuning). Most of the few garage door and gate opener repairs I've done have been mechanical, not electronic.

Times have changes. For keyless entry receivers, I'm seeing SAW filters, superhets, one-chip receivers, etc. For example: etc...

Whether Genie uses technology that's become standard for automobile door openers and alarms is unknown. Schematics seem difficult to find. Most of the receiver pictures of the boards I've found are obviously TRF (tuned RF) receivers, which will have the detuning problems you mentioned. The more modern opener that Jim bought seems to have a more sophisticated receiver: The black wire on the left is the antenna. Most of the receiver is covered but I can see the leads of an SOT device nearby and no adjustable coils near the antenna lead. That suggests a more modern design, probably using one of the aforementioned integrated receivers, which will not have antenna detuning issues.

This has my vote; you would want the outside length to be weather protected, like in some of that ugly gray conduit (or just under the eaves, on insulating standoffs). Bend the inside wire to couple with your 'actual' antenna. Don't ground it to the foil insulation, of course (run the conduit through the insulation).

The problem is further reduced. Finally got the programming to take on the HomeLink transmitter in my Q45 (using the programming technique Jeff found)... the range is substantially increased.

So, either batteries in Genie fobs are weak, or transmitter design is weenie. (Q45 is 9 years old... who knows what emasculation has been done to transmitters by the FCC since then.) ...Jim Thompson

That's awesome, but it has absolutely nothing to do with the problem at hand, and that is Jim's SPECIFIC unit. Which is most likely NOT some regenerative design.