Preamp + adjacent antenna
 

Hi,

I have a scanner (or whatever else I plug in to the coax at the time)
fed by a discone that's about 8 feet from my 2m/440 large vertical
antenna. I run at most 50W into the vertical, usually just 5W, and
have yet to run into any major overload problems into the scanner. At
most, it just stops recieving but I haven't blown anything yet,
probably because it's a 120ft RG-8 run. lossy :) Anyway I'd like to
put a pre-amp at the antenna on the recieve only feed and am worried
that I could overload the pre-amp while transmitting on the other
antenna. What to do here? Relocating it further away would be a last
resort. Shutting the recieve side off during TX is fine. Is there
some remote rf sensing auto coax disconnect device out there?

73
J

Joey,

You will have to feed power to the preamp anyhow. So turn it off when the
transmitter is on. You should be able to arrange it so that the preamp power
goes off automatically when the transmitter is on. For good measure, you
could put a relay at the preamp input to disconnect the antenna input when
there is no power to the preamp.

Tam/WB2TT
"Joey" wrote in message
...
Hi,

I have a scanner (or whatever else I plug in to the coax at the time)
fed by a discone that's about 8 feet from my 2m/440 large vertical
antenna. I run at most 50W into the vertical, usually just 5W, and
have yet to run into any major overload problems into the scanner. At
most, it just stops recieving but I haven't blown anything yet,
probably because it's a 120ft RG-8 run. lossy :) Anyway I'd like to
put a pre-amp at the antenna on the recieve only feed and am worried
that I could overload the pre-amp while transmitting on the other
antenna. What to do here? Relocating it further away would be a last
resort. Shutting the recieve side off during TX is fine. Is there
some remote rf sensing auto coax disconnect device out there?

73
J

And short it to ground.
k
9
d
c
i

"Tarmo Tammaru" wrote in message
...
Joey,

You will have to feed power to the preamp anyhow. So turn it off when the
transmitter is on. You should be able to arrange it so that the preamp
power
goes off automatically when the transmitter is on. For good measure, you
could put a relay at the preamp input to disconnect the antenna input when
there is no power to the preamp.

Tam/WB2TT
"Joey" wrote in message
...
Hi,

I have a scanner (or whatever else I plug in to the coax at the time)
fed by a discone that's about 8 feet from my 2m/440 large vertical
antenna. I run at most 50W into the vertical, usually just 5W, and
have yet to run into any major overload problems into the scanner. At
most, it just stops recieving but I haven't blown anything yet,
probably because it's a 120ft RG-8 run. lossy :) Anyway I'd like to
put a pre-amp at the antenna on the recieve only feed and am worried
that I could overload the pre-amp while transmitting on the other
antenna. What to do here? Relocating it further away would be a last
resort. Shutting the recieve side off during TX is fine. Is there
some remote rf sensing auto coax disconnect device out there?

73
J

"Steve Nosko" wrote in message
...
And short it to ground.
k
9
d
c
i
He means short the preamp input, not the antenna.

Tam/WB2TT

You could also put the relay on the transmit antenna and short it to
ground during transmit, that would keep the preamp happy.





He he he.

Tarmo Tammaru wrote:
"Steve Nosko" wrote in message
...

And short it to ground.
k
9
d
c
i

He means short the preamp input, not the antenna.

Tam/WB2TT

Thanks for the tips all!

On Thu, 20 Nov 2003 23:10:26 GMT, Mike wrote:

You could also put the relay on the transmit antenna and short it to
ground during transmit, that would keep the preamp happy.





He he he.

Tarmo Tammaru wrote:
"Steve Nosko" wrote in message
...

And short it to ground.
k
9
d
c
i

He means short the preamp input, not the antenna.

Tam/WB2TT