Type of Switch?

[ms660]

Anyone know why each coil section has to be shorted out?

Lawrence.

[ChristianFletcher]

Originally Posted by pwdrive

An old type barrel switch is within the realms of DIY:

http://www.americanradiohistory.com/...ical%20hole%22

Brass grub screws could be used for the turret contacts, they can be linked to give progressive shorting of the ATU coil.

Lawrence.

Dont think it would look much like that if I built it

[ChristianFletcher]

Lawrence.

I remember reading somewhere that its advantageous to always short out unused section of the ATU coil. I think this is because if left un-shorted high voltages can be induced in them from adjacent windings and could damage the switches.

Regards chris

[Andrew B]

PW, it helps prevent unwanted interactions/resonances in the unused part of the coil. StationX, admitted, some of the wafers do not need to short out as they select other components in the conventional manner, usually by adding more capacitance. Those sections are easy to produce. .

I have stripped a couple of wafers down while awaiting the arrival of a length of 3/32" copper tube with which to make the rivets/eyelets, which when fitted will be soldered as well (belt and braces).

It appears the Yaesu tuner uses SRBP as the wafer material and as (at the moment) I only have SRBP wafers, I'll give it a try as I don't intend to pump a kilowatt up the antenna (yet!!)

I still can't get over the attitude of the company who made the original switches, in my experience, no-one ever won an argument with a potential customer.!!

I like all of the replies coming in and I hope to meet you all on the airwaves shortly.

73's
Andrew

[Skywave]

Exactly, Graham, re: your post #20.

I did an analysis of the function of that switch with the required corrections made to the original drawing. I was able to reduce it to the following diagram, as below. It assumes a 12-way rotary switch is required. As is often the case - but not always - a complicated-looking switch can sometimes be reduced to something simpler. The reduction process is similar to that for simplifying a combinational logic diagram.

Al.

[Skywave]

Originally Posted by Andrew B

It appears the Yaesu tuner uses SRBP as the wafer material and as (at the moment) I only have SRBP wafers, I'll give it a try as I don't intend to pump a kilowatt up the antenna (yet!!)

Ah! So this is a Yaesu product then: that explains quite a lot! If this switch is designed to handle substantial R.F. energy, SRPB is the last material I would use. Ceramic (or possibly PTFE) would be a wiser choice.

Al.

[Andrew B]

Hi Al.

Thats the reason I am hunting for a ceramic switch, I don't intend to reproduce Yaesu's flaws. The other options are either the roller coaster, the crocodile clip or the sliding tube. (I just thought of a sliding tube mechanism ©)

I do have a pair of 813's squirreled away, as well as a couple of microwave transformers AND some RR03-1250's, of course I will need to pass my "full" exam before I use them.

[bikerhifinut]

Until I saw you were using it for a transmitter I wondered if relay switching would work? standard C/O relayand when its off it shorts the unused section to earth? Are there relays that will handle large amounts of RF energy? I can imagine some of the more delicate stuff might be prone to chattering when you push the transmit button/key?

[Andrew B]

Hi there bikehifinut.

There are plenty of relays that will handle RF, trouble is that every set of contacts and the leads to/from the coil to the contacts adds more inductance.

I do see the point though, a bank of 6 40 amp auto type relays arranged to be switched out of circuit would work, just use 12v on an el cheapo rotary switch to power the relays OUT of circuit, the default NC contacts grounding down a section of coil. a set of 6 spst cheapo switches instead of the rotary, in fact i could use a diode between each switch as an "interlock.

envelope and pencil MK1 coming in to play.................