[OZAPRS] Bad signal on 30m

Richter, Mike W Michael.Richter at team.telstra.com
Sun Nov 28 19:36:23 EST 2004

If you use simple R-C filtering (L-C for power lines) then you shouldn't
need to worry about  shielded cables or shielded cases for 100 Watt  SSB
Mobile. I base this suggestion on the circuit for the Codan 9323.
The original TT3 has IC Pins connected directly to external wiring which
means you are connecting long aerials directly to the silicon - if the
voltage on ANY pin goes above +5 or below 0V, then EVERY transistor inside
the IC can start conducting - expect weird behaviour.


From: ozaprs-bounces at marconi.ics.mq.edu.au
[mailto:ozaprs-bounces at marconi.ics.mq.edu.au] On Behalf Of Terry Neumann
Sent: Sunday, 28 November 2004 2:09 PM
To: ozaprs at marconi.ics.mq.edu.au
Subject: Re: [OZAPRS] Bad signal on 30m

Richter, Mike W wrote:

Getting RF Feedback using a TinyTrak should not be a surprise - the

inputs and outputs go direct to the chip without ANY form of filtering -

I suggest putting a 1k resistor in series and a 0.01uF to ground on all

pins that run off the board. 



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G'day Mike and others,

This is good advice.   I went even further as I thought (perhaps in the
wrong direction).   I used minature rf chokes (from Jaycar) on all the
significant in/outputs from the board, and built mine TT3 board  into a
diecast box as well.

This unit has been used in both of our vehicles on 30 metres and on 2
metres and appears to be free of  RF issues - so far. 

It may have been overkill, but I'm a farmer, and agricultural engineering
principles invariably find their way into all situations 8-)

Is there any merit in using rf chokes as opposed to using resistors, or
vice versa??

Terry VK5ATN

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