This is what I have found.
Using surplus vacuum relays from Russia W1W-1.5kw in this test.
Two relays mounted next to each other in an aluminum box. No shielding
between the relays. Both normally open. Connect one terminal from each relay
together and to an SO-239 connector feeding outside the box to a 50 ohm
Connect through another SO-239 an FT-1000mp to a free relay terminal.
Energize this relay to establish a connection to the 50 ohm dummy load.
To the other free terminal on the other relay connect through a SO-239 to a
second FT-1000mp. Leave this relay normal or open.
Feed 100 watts from the FT-1000mp through the closed relay to the dummy
load. Take S-Meter readings from the second FT-1000mp connected to the open
Output frequency 3.5 MHz
Rec readings: 7 MHz S9+10, 14 MHz No Reading only tone, 21 MHz S3, 28 MHz No
Reading only tone
Output Frequency 7 MHz
Rec readings: 14 MHz S9+10, 21 MHz S9+35, 28 MHz S9+20
Output Frequency 14 MHz
Rec readings: 21 MHz No reading only tone, 28 MHz S9+25
Output Frequency 3.5 MHz one bar wattage out 1 1/4 watts ??
Rec Frequency 3.5 MHz S9+60
At no time did any tone or readings appear at any frequency lower then the
----- Original Message -----
From: "Jim Lux" <email@example.com>
To: "Tom Rauch" <firstname.lastname@example.org>; "RCARIELLO" <RCARIELLO@si.rr.com>;
Sent: Wednesday, January 05, 2005 3:14 PM
Subject: Re: [TowerTalk] Help need Vacuum Relay Isolation 1.8 to 30 MHz
> ----- Original Message -----
> From: "Tom Rauch" <email@example.com>
> To: "Jim Lux" <firstname.lastname@example.org>; "RCARIELLO" <RCARIELLO@si.rr.com>;
> "Towertalk" <Towertalk@contesting.com>
> Sent: Tuesday, January 04, 2005 11:02 PM
> Subject: Re: [TowerTalk] Help need Vacuum Relay Isolation 1.8 to 30 MHz
> > > Even though the relay mfr only guarantees 40dB, you have
> > seen 60 dB?
> > Sure. I measure it all the time with accurate instruments.
> Useful to know... Thanks.
> > RatPak, etc.
> > The Rat Pack I measured had -51.7 dB crosstalk on 14 MHz,
> > and -45.3dB on 30 MHz.
> Did you happen to measure the impedance characteristics of the cross talk?
> That is, given that the isolation decreases with increasing frequency, it
> would appear to be primarily capacitive, as opposed to, say, transformer
> style inductive coupling.
> Mostly, I'm just curious, but not curious enough to go out and hook up a
> relay to a network analyzer, especially if someone else has already done
> > > But even with 60dB, you're still putting 0dBm into the
> > second receiver. If
> > > you're expecting same band operation, that's a pretty
> > challenging dynamic
> > > range requirement if you're looking for narrow band
> > signals at -150 dBm
> > > close to the noise floor.
> > I don't understand why anyone would worry about that.
> Here's a scenario..
> If you had several fairly directional antennas, pointed different
> directions, with good isolation (say they were on opposite sides of a
> a situation mentioned on the list recently), and you wanted to hook a
> transceiver to one antenna, and use a receiver to monitor the other at the
> same time, on the same band, and then be able to switch roles quickly.
> (Hey, maybe you're looking for your own signal after going all the way
> around the world?)
> > Not only is that clearly NOT how he intended to use the
> > switch, the path loss between antennas and other things
> > external to the switch would be an even bigger problem.
> I don't recall exactly what the original post was (it's on another
> computer), but wasn't he switching multiple antennas to either of two
> radios? Antenna 1 goes to radio A or B, Antenna 2 goes to Radio A or B,
> etc. Antenna to the moving arm, radio A on one relay contact, radio B on
> the other relay contact.
> And, yes, antenna to antenna isolation would be an additional concern.
> > Typical receivers will easily handle 30dBm without ill
> > effect when you are not duplexing on the same band.
> Here's an interesting question... Does it matter if the interfering signal
> is higher or lower than the desired signal? Lots of radios have a low
> filter (not a bandpass), for harmonic suppression, and don't have any
> else for preselection. A lower frequency signal will blast right on
> I'd find it sort of amazing that the receiver front end can take a watt
> of band without blocking a lower level signal. That would be a pretty
> mixer unless there's some preselection in front of it.
> See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
questions and ask for Sherman, W2FLA.
> TowerTalk mailing list
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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