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[2E0ILY]

I am at the stage with my Henry 2000D 27MHz RF generator to single band linear amp conversion where I need to address relays and relay control for antenna switching. Has anyone any good links to home brewing this side of things with currently and readily available bits please? I will initially try driving it with a Kenwood TS-590 transceiver into a single band dipole used for both RX and TX. 10 meter band initially, to keep things simple. Thanks.

[WB2WIK]

Many ways to do this, but I usually just use a double pole coaxial relay, using one side of it on the input and the other side on the output, as an electrical "bypass" switch.

Relays like this are readily available and not expensive and handle a lot of power at 28 MHz:

http://www.rfparts.com/coaxial/cx800m.html

I use them all over the place, although most of mine are older "Dow Key" units (American made, and very expensive today), but same idea.

[2E0ILY]

Thanks Steve, will have to try and find a UK source, I asked for a shipping quote from RF Parts on two pairs of Millen HV connectors and ten feet of HV insulated cable and they cited $93 to me here in the UK, which kind of told me they didn't want the order, not that it would put much turkey on the table at Christmas.... Shame, as they have lots of "nice stuff".

So I don't need to be looking at vacuum relays then? I was worrying about adequate switching speeds and stuff as well. Cheers.

[WB2WIK]

No need for vacuum relays unless you want the amp to run QSK on CW.

Otherwise, you should never be switching relays at the same time as RF, and most transceivers won't do that -- they apply the "amp switching signal" before the RF output, and then reverse that when going back to receive.

As such, almost any kind of relay works but the coaxial relays can handle serious RF power and even maintain pretty constant impedance (50 Ohm) as well.

The relays I referenced aren't American-made, they're made in Japan and surely available in Europe.

[2E0ILY]

OK, got it. I will have a search around the web for suppliers in Europe or ideally the UK, many thanks for bearing with me. In fact I have a pal ringing me tonight who has a lot of surplus RF stuff, I might ask him what he has stashed away.

[G3RZP]

Mostly, you can get away pretty well with a normal open frame realy at HF. I like to use a 3 pole relay, with two of the changeover pairs for the antenna/amplifier in/out switching and the third pole for the amplifier control - that minimises the hot switching chances. But doesn't work for QSK.

DON'T use the Millen HV connectors. They are very poor by today's standards - W8JI cites instances of people being electrocuted touching them.  They are said to be hygroscopic as well. Lash out on some proper high voltage PET connectors from RS or Farnell.

[2E0ILY]

Funny you should say that. I posted somewhere about how the wire is retained in the Millens, either on this forum, or another. I had only seen photos of them and the male connector seemed very short with little outer cable outer insulation "within" the connector. Now they have physically arrived I see they rely solely on a soldered connection to the conductor holding about an eighth of an inch of double sheathed outer insulation within the body of the plug. Now, it doesn't take much to pull a cable so the outer moves an eighth of an inch relative to the inner, exposing the conductor, does it? Nor to break the inner conductor and have the then unrestrained HV cable flailing about. Not what I fancy with 5kV at near two Amps flowing ..... I have got some proper HV connectors and sockets on order. They say one learns, or should learn, from ones mistakes. i don't fancy a 5kV mistake, I;'ll put the price down to experience. thanks for the info on the relays, and the heads up on the Millens!