[Kenwood] Kenwood TS-950s & a L4B

[Paul Kraemer]

#1 You can get a VOX2RCA adapter from Harbach that replaces the obsolete 
Drake connector with RCA jack.  The fact that there is 24vdc present at the 
key jack can be remedied by either an interface device or a soft key in the 
amp
#2 ALL old amps exhibit some delay in keying that only shows up when keying 
with a new solid state rig unless the rig has a time delay in it.  Kenwood 
included this delay in some of their transceivers to allow better interface 
with the TL-922 amp.  Bottom line is it takes time for the antenna relay to 
close.  17ms is best case in the L4B.  It  can be worse because Drake used 
simple  half wave supply for the relay and probably minimal filter capacity. 
If the transceiver is fast there will be rf present before the antenna relay 
in the amp operates.  I use an FT-950 that is particularly bad that way. 
About once a year I have to clean the rf burn off antenna relay in a linear. 
The problem shows as receive drop out.  Some enthusiasts have devised work 
arounds for this---none real easy I know of.
I addressed these issues and others in my ES4L4B soft start / key / bias 
module available from Harbach and Nationwide.  After the installation the 
relay still takes 17ms to operate but at least it is consistent.  The key 
jack voltage will be less than 12vdc, safe for even an Icom.  The resting 
plate current will be reduced a lot saving much power that was otherwise 
wasted in heat.  And there is a soft start.
Paul K0UYA

-----Original Message----- 
From: wg davis
Sent: Monday, September 11, 2017 2:21 PM
To: Kenwood Reflector
Subject: [Kenwood] Kenwood TS-950s & a L4B

    Mrng. Guys,
           My half-Brother has a newer radio and has just put his L4B back
in service
(since he gave my SB-201 back to me).. I was looking online and discovered
that
using the L4B could cause 2 different problems; if U can believe what one
can
read on the Web.. I told Floyd that one side of the Vox Relay connector
has 24 Vdc
or more on it.. He has had this amp over 30 years and had never heard
this, discovered
that is has Vdc after U take it off of Standby.. That is not good, in my
opinion.. The 2nd.
thing is something about there being a delay from when the Transmitter is
keyed to
when the L4B is keyed (my words/ term could be wrong).. Some people are
concerned
about there being a ohms/ impedance mismatch for short period of time..
And some
others are not concerned..
            Do U know where we could get 2 or 3 of the connectors that are
used at the
Vox Relay connector; it is 2 straight pins..


-- 
73,  K4WGD
______________________________________________________________
Kenwood mailing list
Home: http://mailman.qth.net/mailman/listinfo/kenwood
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Kenwood at mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html