Yes, those are "enclosed" open frame relays. The SB-220 relay is excellent
and very reliable considering how many still see daily use after 30-40
Ive never got close to that with a vacuum relay.
----- Original Message -----
From: "Steve Flood" <firstname.lastname@example.org>
Sent: Saturday, March 29, 2008 2:31 PM
Subject: Re: [Amps] open frame relay rating
> Thanks Carl and others for the replies. I don't plan to use this amp
> 20m actually. One of my relays is very similar to the SB-220 relay - and
> thinking I'd use the same setup with a third pole for the bias circuit.
> BUT, I surely do not want to lose any significant signal in RX mode.
> Are the "general pupose" relays considered "open-frame" - I am referring
> those where you can see the working parts through a clear plastic shell.
> They are used in my Amertiron remote coax switch and Ameritron rates those
> at 4kw HF.
>> Many amps used open frame relays with 10-13A contacts and they worked
>> at 1500W. The one issue with them is high VSWR in the thru position on
>> which can fold back the power in a SS rig. The cure is simple, add a
>> capacitor from the thru loop to ground to tune out the Xl.
>> You can use an adjustable mica trimmer and leave it or measure the value
>> and replace with a 1KV disc ceramic or 500V mica. Typical values are
>> pf. Any one will handle 100W with ease.
>>>I have several open-frame relays. If I use one for the T/R relay, what
>>>should the contact rating be for a 1500w amp? Is it as simple as 1500w
>>>50 ohms = SQRT of 30A or 5.5 Amps?
>>> Steve, KK7UV
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