Hi Andy and Genossen LFers!
The hi-voltage relays problem will be solved by serially
connected not so hi-voltage relays!
This way was used at the time when radio was young.
The schematic diagramm of Khodynka's spark-gap TX at 1914 in
Moscow.
That method was used 9H1ZA in Malta for 160m's vertical also.
Vlad remember me that simple method at first time.
73!
Roman
Hi Andy
Surely the voltage will not
appear across the contacts, though I agree contacts to
activating coil might be a problem.
Yes reeds area problem because
I think of the reed material. I only used them (from Coto)
at low levels on ATE. I did have some rated in the kV range
but not taking much current.
Alan
G3NYK
----- Original Message -----
Sent: Thursday, November
19, 2015 12:44 PM
Subject: Re: LF: Re:
Antenna relays
Alan -
You're forgetting the loading coil has to be switched
out when using the loop at HF, so the relay has to
withstand the full RF voltage when using it as a vertical
at LF/MF.
So you'll need a vacuum relay with a contacts rated at
something like 10kV. The current will only be an amp or
so. I tried this once using FR / Crydom reed relays that
were certainly rated at that sort of voltage. Trouble was
that rating was DC. At 137kHz it died with a flash from
inside and melted contacts as soon as a decent amount of
RF was applied.
A knife switch on a ceramic former would probably work,
otherwise find someone working for
NatGrid and try to get a 33 or 132kV contactor :-)
Andy G4JNT
On 19 November 2015 at 12:24, Alan Melia
<[email protected]>
wrote:
Hi Chris I dont think
the relay type is too significant at these
frequencies. The important thing is its contacts
should be able to carry the current. It is at a low
impedance point so the voltages should not be
excessive. Even an open frame style intended for
switching 20 to 30A of 230v would be worth trying (I
am sure you have a bin-full or two of those lying
around :-)) ).......the old-timers used knife
switches at these frequencies :-))
Alan
G3NYK
----- Original Message ----- From: "Chris Wilson" <[email protected]>
To: <[email protected]>
Sent: Thursday, November 19, 2015 12:00 PM
Subject: LF: Antenna relays
19
November 2015
I am currently running a bottom strapped windowed
ladder line feeder to
my horizontal quad loop as the vertical for
LF, the loop as the
capacitive top hat. It means I am unable to use it
for HF though. I am
wondering if I might add a remote switched relay at
the bottom of the
ladder line, so it has two states. One connects my
co ax feeder to the
ladder line with the bottom strapped together.
the other opens the
strap and connects the 2 legs to a balun and then my
co as feed line.
Given the voltages involved at LF, what sort of
relay would I need to
be looking at? Thanks.
--
Best regards,
Chris 2E0ILY mailto:[email protected]
--
73!
Roman, RW3ADB
