It also slows down the closure speed considerably. Back when I was using
that combo I settled on 100 Ohms as a reasonable compromise.
A diode across the amp relay is always a good idea no matter how it is
being controlled.
Carl
KM1H
----- Original Message -----
From: "Pete Smith" <n4zr@contesting.com>
To: <amps@contesting.com>
Sent: Sunday, November 09, 2008 11:06 AM
Subject: Re: [Amps] SB-220 saga continues
>A very simple fix, which worked for years with my SB-220 and TS-930, is
>to
> insert a 220-ohm resistor in series with the kPTT lead. Does nothing
> for
> the voltage rating of the transceiver switching circuit, but it does
> limit
> the current surges that weld relay contacts together.
>
> 73, Pete N4ZR
>
> At 10:20 AM 11/9/2008, W4TV wrote:
>
>>The keying line (PTT relay) in the SB-220 is +120 V DC. The contacts
>>of the "Linear" or "Send" relays in most transceivers can not handle
>>the voltage and current "spike" generated by the high voltage PTT
>>circuits in the older amplifiers (SB-200, SB-220, L4, L7, TL-922,
>>etc.).
>>You will probably need to replace the "Linear" or "Send" relay in your
>>transceiver (if you are lucky, that will be all).
>>
>>I suggest adding a keying buffer (e.g. Ameritron ARB-704), modifying
>>the SB-200 with the internal Harbach Electronics soft key circuit
>>(www.harbachelectronics.com/main/page_products_sb220__sb221.html),
>>or converting the SB-200 to faster, low voltage relays and electronic
>>bias switching.
>>
>>73,
>>
>> ... Joe, W4TV
>>
>>
>>
>> > -----Original Message-----
>> > From: amps-bounces@contesting.com
>> > [mailto:amps-bounces@contesting.com] On Behalf Of Roger (K8RI)
>> > Sent: Sunday, November 09, 2008 12:34 AM
>> > To: ke1fo@arrl.net
>> > Cc: amps@contesting.com
>> > Subject: Re: [Amps] SB-220 saga continues
>> >
>> >
>> > Please do not cross post between reflectors.
>> >
>> > Roger (K8RI)
>> >
>> > Alfred Frugoli wrote:
>> > > Hello everyone,
>> > >
>> > > So it seems I've got a problem with my SB-220.
>> > >
>> > > When the amp is off, but connected in the RF path,
>> > everything is fine.
>> > >
>> > > When I switch the amp on I've suddenly got lots of attenuation
>> > > happening on the receive path. Transmit seems fine - amp tunes
>> > > OK
>> > > etc.
>> > >
>> > > My first suspicion was that there were dirty relay contacts on
>> > > the
>> > > receive side. Cleaned the contacts with no success. Then
>> > I realized
>> > > that the problem only occurs when the amp is on. So a trip to
>> > > the
>> > > schematic tells me I don't understand. In the RX mode the RF
>> > > path
>> > > through the amplifier should be the same as when the power
>> > is on. So
>> > > I'm not sure where my attenuation is coming from.
>> > >
>> > > Just testing it a few minutes ago I can make an S5-7 station
>> > > almost
>> > > completely disappear by turning on the amp, so I've got
>> > somewhere in
>> > > the area of 20db of attenuation happening!
>> > >
>> > > Thoughts?
>> > >
>> > > Thanks.
>> > >
>> > > 73 de Al, KE1FO
>> > >
>> > > -----
>> > > Visit my amateur radio contesting blog at ke1fo.wordpress.com.
>> > > _______________________________________________
>> > > Amps mailing list
>> > > Amps@contesting.com
>> > http://lists.contesting.com/mailman/listinfo/amps
>> > >
>> > >
>> >
>> > _______________________________________________
>> > Amps mailing list
>> > Amps@contesting.com
>> > http://lists.contesting.com/mailman/listinfo/amps
>>
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