Why not change to a 12 V relay in the 30L-1 ???
73 de Osten SM5DQC firstname.lastname@example.org
----- Original Message -----
From: "JOS Earthlink" <email@example.com>
To: "Tom W8JI" <firstname.lastname@example.org>; <email@example.com>
Sent: Saturday, December 09, 2006 4:14 PM
Subject: Re: [Amps] Optoisolator for Keying Collins 30L-1 to Modern Rigs
> Dear Tom,
> Thanks for the clear and detailed answer. I impulsively bought the Ampkeyer
> recently which really is a great value and beautifully constructed. But the
> Ampkeyer manual says not to use the MOSFET circuit for amps like the 30L-1
> as they were not designed to handle the 30L-1 antenna relay voltage/current.
> So I used the Ampkeyer's mechanical relay option and it was at that point I
> realized that I could have put something identical together much more easily
> and cheaper from my junkbox (though the Ampkeyer is pretty inexpensive). I
> guess the bottom line is how well can the finals in my TS-950SD handle the
> transient high SWR's until the 30L-1 relay kicks in - probably not a problem
> in the short-term but the noise you pointed out makes much more sense as an
> issue to avoid.
> The Ampkeyer doesn't show its schematic but the MOSFET is a IRF644B which
> has a rating of 250v and 14a but I guess it cannot handle the negative 170
> voltage of the Collins antenna relay?? Are there any solid state solutions
> that would work with the neg voltage?
> 73 Jerry
> -----Original Message-----
> From: Tom W8JI [mailto:firstname.lastname@example.org]
> Sent: Saturday, December 09, 2006 6:13 AM
> To: JOS Earthlink; email@example.com
> Subject: Re: [Amps] Optoisolator for Keying Collins 30L-1 to Modern Rigs
>> Question is for routine SSB (and some occasional CW) does
>> one really need an
>> optoisolator circuit controlling a relay rather than just
>> a lowvoltage power
>> source plus a well rated (250vdc 2a) low voltage relay?
> The problem with a relay keying another relay is activation
> times are added. Whatever small relay's time you add in, it
> makes an already poor situation worse.
> Say you have 13mS on the large amplifier relay and 5mS on
> the small relay. Pull in would now require 18mS.
> Virtually all rigs actually output RF before the antenna
> relays can transfer in an external PA. This can cause
> amplifier bandswitch or tank component arcing or damage,
> annoying pops or clicks up and down the band, and chopping
> of the first part of transmission at every VOX or key
> closure if you are not using push to talk or manual transmit
> With a solid state buffer circuit you don't add the time of
> another relay.
> It does not take a special expensive circuit to do this or a
> high speed relay. All it takes is one or two transistors, a
> resistor or two, and a diode. You can also use a very fast
> external relay, like a HV reed relay, but you have to watch
> voltage and current transients.
> It might be less time and worry to buy one. Ameritron also
> offers a relay buffer. But they are easy to build.
> 73 Tom
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