🚀 go-pugleaf

In article <C1HAr2.L7G@hpchase.rose.hp.com>, jahr@hprnd.rose.hp.com (Steve Jahr) writes:
> Chris Kaiser (kaiser@elec.canterbury.ac.nz) wrote:
> 
> Well...... this sounds good on paper.  The problem is that the inside
> of a Tx is a very hostile environment for electronic thing-ies.  Seems
> that there is a great deal of EM garbage/noise being generated from
> that long metal thing sticking out (:
> 
> Seriously, I tried a little op-amp adder for a dual rate circuit once
> and it didn't work anything like I expected.  As I recall it worked on
> the voltmeter *until* I reconnected the RF module and then it went nuts.
> Seems that the op-amp tried to follow the RF signal noise as well as
> the control pot signal.  Nothing that I tried would clean up the signal
> enough (filter capacitors and RF chokes).
> 
> Perhaps if you use a *really* slow op-amp though...

Hmmm. I did say that I hadn't got around to actually trying it...
One could take the brut force approach and stick the circuit inside
a fully enclosed metal box with shielded connecting wires. Otherwise
a bit (lot?) of knowledge and experimentation with noise reduction
techniques would be required. Considering the amount of electronic
thing-ies inside a modern radio it must be possible to suppress the
RF, but probably not easy.... :-(
A PCB (not veroboard) with ground plane would probably be essential.

Chris Kaiser

Postgrad, Elec. Eng. Dept.
University of Canterbury
Christchurch, NEW ZEALAND