[Amps] SB-220 saga continues

[Joe Subich, W4TV]

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 at contesting.com 
> [mailto:amps-bounces at contesting.com] On Behalf Of Roger (K8RI)
> Sent: Sunday, November 09, 2008 12:34 AM
> To: ke1fo at arrl.net
> Cc: amps at 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 at contesting.com 
> http://lists.contesting.com/mailman/listinfo/amps
> >
> >   
> 
> _______________________________________________
> Amps mailing list
> Amps at contesting.com http://lists.contesting.com/mailman/listinfo/amps