[Boatanchors] Antenna Relays & T-R Switches

[Peter Markavage]

Many of the boatanchor receivers used a link coupled coil to the antenna
terminals  on the antenna coil. On several of them that I've had back
then, and throughout the years, I've added a small lamp in series with
the antenna connection to the receiver. The cold resistance of the lamp
was small enough not to degrade the performance of the receiver. If by
chance, RF got on the lead to the receiver, the lamp would light (since
the cold side of the link on the antenna coil was generally tied to
ground)  and the lamp resistance would go up in the receiver input line.
If enough RF got on the lead, the lamp would just burn out and open the
connection. Never lost an antenna coil in the process. If you go back to
some of the early ARRL Hints and Kinks, this process was documented a
number of times. I also used this process as simple form of T-R switch on
a low power 2E26 homebrew 6 meter transmitter and using an Ameco CN-50 6
meter converter. Added a phono jack to the back of the homebrew
transmitter for converter input connection, one side of the lamp (I
remember using a small Xmas tree type lamp) connected to the center pin
of the phono jack and the other side of the lamp connected to the
pi-network of the transmitter output. When transmitting, the light would
glow, causing the resistance of the line to the receiver to increase.
Never lost the antenna coil, nor the front-end nuvistor, to RF burn-up
with this setup and I used it for several years. That rig is still around
here somewhere.

Pete, wa2cwa

On Wed, 5 Nov 2008 18:21:45 -0500 "Mark K3MSB" <mark.k3msb at gmail.com>
writes:
> On Wed, Nov 5, 2008 at 5:49 PM, Peter Markavage <manualman at juno.com> 
> wrote:
> > "am I pumping some or all of my RF back into my receiver".
> 
> Which brings to mind a question I've wondered about..... why did 
> the
> rx manufacturers of old never put a small fuse in the rx right 
> after
> the input jack, just in case?   I've considered doing that on my BA
> rx's as I restore them.
> 
> Several years ago when I was working on my 5100B I had a pre-senior
> moment and used the TS-830S as a dummy load.....
> 
> 73 Mark K3MSB
> _______________________________________________
> 
>