How does this Bird Co-arse Switch work???

[WBear2GCR]

http://birdtechnologies.thomasnet.com/item/components/selector-switches/74?

What the heck does this mean??

Bird's RF Selector Switches employ a unique, rugged and reliable design which permits positive contact, low insertion VSWR and negligible cross talk between channels. The switching mechanism is 4 1/2" of RG-87/U Teflon cable which is pulled away from the mating Male N connectors and rotated to the desired switch position.

Say what?

What's the internal construction here?
How does it work??

                _-_-bear

[KF1Z]

Instead of just a metal wiper, it uses a cable with button contacts.

[WA1GFZ]

It is a rotary patch panel center pin common and outer connectors positions. You pull then turn to the position you want then push the knob back in to mate the connectors. Very KISS

[WA1GFZ]

not button contacts but the center pin and shield termination that move into the position you want to select.

[K5UJ]

Sounds weird doesn't it.  I never really got it until I bought two off a guy and took them apart.  They disassemble for cleaning real easy.  I'll try to describe it but I don't know how good I'll be at that.

You have a two piece cast shell, one part is a bell shape with a hole in the top for the knob shaft. The bottom is a round plate that bolts to the bell and has six threaded (thread on the outside) cylinders sticking out, all along the edge and one in the center that protrudes a bit farther down.  these make up the outer threads of N jack connectors.   You know how a N male has that inner ring with the center hot pin in the middle, and N females have a center pin that fits over the male pin.  Well the switch knob shaft goes down through the bell and inside, it is attached to an upside down coax U that is soldered to female pins and shields so if you screw on a male N connector to the center and one of the outer threaded cylinders the center pins are there and the shield is threaded on and common to the bottom plate and bell.    You switch coax by grabbing the knob and pulling on it so you pull the U away from the pins and it rotates around and when you are in a position to mate with a feedline you want, you push down on the knob and that pushes the U female pins down on the N males to make contact.   You are basically pulling and pushing a small U shaped coax jumper and rotating it around among the six outer jacks with the center one always being your central line the others are switched to.  It handles more power with isolation, because it is basically a very short, high-watt jumper.  It is also made to be bolted to a front  panel so it can be mounted inside a piece of equipment.  

They are made in different configurations.  There is one where all unused jacks are shorted to ground for example and another version where they are open.   The two I got I paid $75 each for.  they were crudded up on the inside with years of tarnish and dirt but I cleaned them out as best I could with contact cleaners and Q tips and tooth brushes then a friend finished them with an air hose and I regreased them and they're like new now.  Only thing is if you use UHF connectors you have to find some good silver N to UHF adapters.

Rob

[WBear2GCR]

So to simplify, the end that moves to the different positions has a "U" of coax with the end afixed to a rotating mounting surface and having a female "N" connector affixed & soldered. Pull back and the connectors slide apart, rotate, and remate the next N connector?

What is the center? The same deal? What about wear on that center from the rotation, or does that also get pulled out, then rotated? Hmmm, not bad!

What keeps it from being re-inserted inbetween positions? A plate with holes??

What is the diameter of this magic coax they use? different than RG8 size?? IF so how do they get it to rotate?

Oh, and why do they need the coax with the shield also switched? Can't the case make that connection so all that is needed is the center conductor and maybe some insulation??

                    _-_-bear

[WD8BIL]

You're basically rotating a coax jumper from outer shell to outer shell. The center connector is common and breaks connection for rotating when you pull the knob towards ya. I use the 74 all day at work. Built like a tank! As the GFZ said.... KISS!

[K5UJ]

So to simplify, the end that moves to the different positions has a "U" of coax with the end afixed to a rotating mounting surface and having a female "N" connector affixed & soldered. Pull back and the connectors slide apart, rotate, and remate the next N connector?

What is the center? The same deal? What about wear on that center from the rotation, or does that also get pulled out, then rotated? Hmmm, not bad!

What keeps it from being re-inserted inbetween positions? A plate with holes??

What is the diameter of this magic coax they use? different than RG8 size?? IF so how do they get it to rotate?

Oh, and why do they need the coax with the shield also switched? Can't the case make that connection so all that is needed is the center conductor and maybe some insulation??

                    _-_-bear

Both connections pull out.   The rotation axis is on the center connector pin, so the outer end of the U rotates about the axis of the knob shaft.  

I left this part out because the earlier description was already too long but there is a click-stop using ball bearings and grooves in the inside surface of the bell so each coax position clicks into place so you can't accidently get between connectors.   the coax is the size of 213 minus the outer jacket.  It's like tinned 213 minus the jacket except I think it is something else using silver and teflon.  

If the switch only were designed for HF it might work okay without coax and just a wire for the center but it was made to be used up to at least 1 GHz maintaining a 50 ohm Z and also it provides 75 dB isolation between the active and inactive circuits and you would not get that with only the center getting handled with a wire.

[WBear2GCR]

ah kewl!!

Ahzasta getme one!!

         

                   _-_-bear

[WA1GFZ]

I've used these switches at TACAN and IFF RADAR. I would give them the same rating as RG393 with quality N connectors

[KM1H]

Ive used one since the early 60's. They do become intermittent after 30 or so years and a good cleaning makes them as new.

[WA1GFZ]

I've replaced the contacts on one of my switches. All you need is the pin from the right female n connector.

[W9GT]

I have a variation of one of these switches that I believe is called a "transfer switch or bypass switch".  It has four N connectors...can be used as a SPDT type switch using three terms, but actually switches the jumper back and forth between the two sets of connections.  In other words...input R1 switches between output X and A and, at the same time, input R2 switches between output A and X.  It is an interesting switch..not sure what it would have been used for....anyone know?

73,  Jack, W9GT

[WA1GFZ]

I have a couple transfer switches. They work great when you want to run phased antennas. Good for switching delay lines or stubs. Takes a bit of thought and maybe an ohm meter. When you figure it out all you can think is KISS.

[W9GT]

Oh OK...could actually be used to reverse connections on two antennas.  That might be a handy thing for those loops we have been playing with.  Although, I actually prefer Steve's switching arrangement.  By the way, Frank,  I'm in the process of getting ready for a redux of the antennas here...will be putting up a new 20' boom for the loops at about 72'...hopefully, will enjoy an improvement in performance and be able to maintain the proper spacing.

73,  Jack, W9GT

[WA1GFZ]

72 feet is great. Yes Steve's method with the relay is a lot more efficient.
I'm actually using a coax transfer relay on my set up. It hangs between the loops to select short or feed line to reverse the pattern. I'm at around 55 feet.
I put pulley wheels at the ends of the boom so I can service whitout going up the tower. This year I hope to improve RX with a KAZ antenna or phased KAZ loops. I have 2 simulated and now looking at 3 of them. A single KAZ works better than a short beverage. I've been running tests facing WWVH.