[1000mp] PTT with outboard filters

[Mark Shaum]

Tom,

I hope you didn't hook the SB-220 and external DSP in parallel,
grounding through TX GND?  Unless you have modified your amp, the 120
volts DC the SB-220 presents on its relay jack to pull to ground might
be a tad too high for the outboard filters to deal with on their T/R
line.  If the TX GND will key the filter bypasses ok without the SB-220
in the circuit, you are probably ok.  Any of the "soft key" transistor
circuits can be added to the line between the SB-220 and Yaesu to
isolate the switching from the high voltage relay coil.  I'm also
presuming the PTT line on the filters is a "ground during transmit" type
of input and doesn't need a pullup resistor or such.

Mark K9TR

----- Original Message -----
From: "Thomas Beltran" <tbeltran at earthlink.net>
To: <1000mp at mailman.qth.net>
Sent: Thursday, September 02, 2004 11:04 AM
Subject: [1000mp] PTT with outboard filters



I use either a Timewave 599zx, or an NIR-12 outboard filter with my Mark
V.  On CW, both filters have a feature, where a PTT line can be hooked
up, turning off the filter, so that one can hear the unfiltered
sidetone.  I also use an SB-220.  I thought the proper way to get the
PTT switching on the outboard filters, was to use the TX GND plug, which
I also use for my SB-220.  This doesn't seem to work.  Is anyone else
using a similar filter?  If so, how does one obtain the PTT switching?
Tom W6EIJ