Topband: "Is your feedline also an antenna?"

[MW Comercial]

> The most common problems I see with signal ingress is poor
> connections on shields where connectors are installed. With
> equipment it is poor connector layout or grounding on a
> chassis or wiring inside.

I will check this, it can be fixed easily if sth is wrong.

> > Honestly, I don't know if it's constructed well enough,
> but I hope so. Any
> > way, there are 3 relays switching between beverage's and
> K9AY. I switch the
> > coax center and shield of all cables / antennas.
>
> As a general rule that is a problem. I would never switch
> the shields in my station. It is begging for problems! The
> shields should be solidly grounded to a common groundplane.
> Only the centers switched.

Here we have a problem. After reading this comment, I said to myself: "OK, I
give up". The first switchbox I've built few weeks ago was very simple and
switching only the centers. All cables were sharing common ground. Than,
I've learnt from ON4UN book: "make sure you always switch both the inner
conductor and the shields (...)" This was confirmed by other HAM's. So I've
spent 2 more days rebuilding my switcher. Seems that now I will have to do
it again.. But before I'll do that , I will run a simple test, connecting
just one cable / one antenna directly and will see if there is any
difference when the switcher is out of the system. Will let you know about
the result.

>
> Relays always have some coupling between the coil windings
> and the armature. The armature is near the signal leads.
> Many relays actually have the steel pole piece inside the
> coil actually connected to the armature, they might have
> 20pF capacitance directly from the common contact to the
> coil. Other relays have long leads that pass the coil.

OK, now I see, thank's for the explanation. I will try to measure if there
is any capacitance there, in the relays I use.

> Unless you know the relay has very low RF coupling from
> contacts to the coil, you should have a low impedance bypass
> capacitor from the coil to ground and a very short ground
> lead on the grounded coil terminal.
> Otherwise you can have relay to relay crosstalk and relay to
> control cable signal coupling.

If there is a relay to relay crosstalk, there should be a difference while
listening on one of the antennas, and connecting / disconnecting the other
antena from switcher, right?

> 73 Tom
73 Mac