[TowerTalk] Serious RF Problem

[VR2BrettGraham]

K9YC continued:

> >Good point - though for all the radios to have a pin 1 problem is a
> >little odd (though if it is another device that's locking up, maybe it
> >has a pin 1 problem itself).
>
>Sadly, it is not odd -- the ham radio community, and the engineers who
>design for it, are mostly unaware of it. When Neil Muncy (ex-W3WJE)
>taught us about it in 1994, virtually ALL pro audio equipment was built
>with pin 1 problems, even the most expensive broadcast equipment and mix
>consoles. Today it's more like 50%.
>
>Today, virtually all computer audio gear has pin 1 problems at its
>inputs and outputs. AND so do the serial ports!  I am convinced that pin
>1 problems are the root cause of the vast majority of "RF in the shack"
>problems.

<snip>

Luckily, I'm still using the same serial card from way back that
seems to be okay.  Computer sound is certain to be a problem &
so far so good, I've been okay as-is for just recording the receivers'
audio.  Hooking the computer to the mic is an almost certain pin 1
problem, that's for sure!

When adding bypass caps, I have seen some instances where
grounding for cabinet, connector case (if any) & cable shield/return
lead needed improving, but for the most part, the typical spiquet
on a box in the shack is okay if it's got some protection from
incoming RF on it.

The mic input on the OMNI 6 so far has been the only thing where
I have had to get carried away (isolation transformer).  As I work
mostly CW, I have to admit that this might also have had some
bearing on my experience.  ;^)

Otherwise, decent cable (shielded twisted pair is great stuff) &
mystery torroids from parts shops (I buy a handful of whatever
shows up) tend to do the trick.  After I started feeding the roof
tower as a vertical, I found that the decoupling required for that
made a big improvement inside & doing something about the
source of the problem probably helps get me below some
threshold for other nasties to rear their ugly heads.

Hopefully our experiences will be helpful for K9OM & anyone
else with similar situation/problem.

Oh, almost forgot - have also found proper feeding of antennas
helps - choking feeders at the feedpoint (tribander & HF2V
about 10m from shack on fourth floor under a tin roof).  Even a
little sniffer with a light bulb, continuing with GM3SEK's
suggestion, might suggest that coiling the feeder to an
otherwise properly fed antenna might substantially help things.

73, VR2BrettGraham