[CQ-Contest] lock-outs

[k8cc]

At 10:21 AM 11/6/00 -0500, Rick Dougherty wrote:
>Hello all...our small multi-multi has finally decided amongst the ops that
>we need to have a second station on the bands in order to be more
>competitive...wonder if Tim K3LR, Frank W3LPL ,and Matt KC1XX would be
>willing to share their lockout methods with the contesting community...in
>that matter anyone else who may have a working design...it might save us
>some development time not having to re-invent the wheel

Rick,

I've been fortunate to have operated at W3LPL, but was waiting to see if 
Frank was going to answer before commenting.  I've been (although never 
operated) to K3LR and seen his setup.  We also do interlocked stations at 
K8CC, so here's my input.

One major difference between K3LR and W3LPL is that Tim has physically 
separate stations; that is, the run and mult stations each have their own 
radio/amp and separate antennas.  Frank has two transceivers going into a 
single amp connect to that band's set of antennas.  With interlocks on the 
transmit control (i.e., PTT) the two systems are functionally equivalent 
with regards to allowing "only one transmitted signal at a time".

However, the two systems improve significantly different requirements to 
implement.  K3LR's method is simplest with regards to the interlock 
circuitry, but the run and mult antennas on any band must have sufficient 
separation to prevent in-band RF-induced damage to the receivers - bandpass 
filters won't help this.  However, one advantage of this system is that it 
allows each receiver to (attempt to) hear while the other radio is 
transmitting.

The W3LPL system feeds the transmitter output(s) through a relay which 
decides which radio actually goes to the final amplifier and out the 
antenna on transmit.  Other relays allow both receivers to listen as long 
as neither radio is transmitting.  Since no receiver is connected to an 
antenna when either radio is transmitting, there is no danger of in-band 
RF-induced damage.  At the same time, you can't hear anything when the 
"other" station is transmitting.

I would think that with your current setup (bands intermixed on your three 
towers), a variation of the W3LPL setup might be the only way to go to 
prevent in-band RF-induced damage.  You will need some sort of PTT 
interlock, which also drives the "which rig transmits" RF relay which 
routes the transceiver output(s) to the amp.  You also need to come up with 
a way to allow both receivers to "hear" when neither transmitter is off 
line.  At K8CC, we've found this to be not too difficult with certain ICOM 
radios like IC-781s and IC-765s thanks to access to the receive path via 
rear panel jacks.  With FT-1000Ds, and many other radios which have only 
aux antenna inputs on the back, an old-fashioned "T/R relay" is needed on 
the amp input.  The transmit side of this relay goes to the "which rig 
transmits" relay while the receive side goes to the transceivers' aux 
antenna inputs.

Hopefully this will get you started.

73,


Dave/K8CC


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