Sometimes I have a good enough signal to a repeater that I can key in,
but not enough to have anything other than a carrier signal get
through. Now, if I'm trying to get attention on a repeater on, say,
the 2 meter band, how do I know whether I'm full quieting and there is
just no one listening at the moment or I'm having problems getting
through? A friend suggested having a scanner handy with earphones to
listen to myself on the output freq. I tried that and it didn't seem
to work at all.

I'm using a Kenwood TH-F6 to transmit on 2 meters and I have an Icom
R3 tuned to the output of the repeater I am keying up. I don't have
any problems getting into the repeater and everyone seems to hear me
just fine. The only thing is, I can't hear myself through the Icom
when I transmit on the Kenwood. The Icom is functioning otherwise.
It picks up the output of the repeater without issue unless I am
transmitting through it with my TH-F6. For a moment I thought that my
hearing was to blame, so I dug out an old analog oscilloscope that I
had bought at a MIT flea market years ago for about $75. I visually
watched the audio output of the Icom with the scope. When other
operators were transmitting through the repeater I could see their
voices dance on the blue-green glowing screen of the scope, but when I
transmitted all I saw was a flat-line.

Why is my scanner deaf when I'm transmitting with a separate rig?
Could this have anything to do with near-field emissions? I'm
transmitting with 5 watts of power using a 7.5dB gain omni-directional
antenna. My scanner is always within 10 feet of the antenna.

Repeater output freq: 147.000 MHz
Offset: -600KHz

BTW, I've talked with another ham that has experienced the same thing,
so at least I know I'm not going nuts just yet.

KC2MAC

Front end overload.

It's like trying to see a candle next to a spotlight shining in your face.

Radioman wrote in message ...
Front end overload.

It's like trying to see a candle next to a spotlight shining in your face.

Even though they are different freqs? I'm transmitting on 146.400,
but listening on 147.00 (-600k offset). Is there anything I could do
to treat the symptom aside from keeping the antennas of the two units
far apart from each other? I wish I had a spectrum analyzer. I'd
love to see definitively what is happening to the spectrum when I
transmit. Maybe there is a way I can turn my old oscilloscope into a
spectrum analyzer. hmmmmmmm...

KC2MAC

On 2 Dec 2003 09:32:01 -0800, (KC2MAC) wrote:

Radioman wrote in message ...
Front end overload.

It's like trying to see a candle next to a spotlight shining in your face.

Even though they are different freqs? I'm transmitting on 146.400,
but listening on 147.00 (-600k offset).

You may think it's a lot, but 600 kHz to an FM radio can be quite
close.

Is there anything I could do to treat the symptom aside from keeping
the antennas of the two units far apart from each other?

See my other response regarding antenna polarization and duplexers.
You could actually build a simple notch filter out of a piece of coax
and a T fitting. It's not going to be very deep, and it will be wider
(in terms of bandwidth) than a duplexer, but every dB helps in this
case.

I wish I had a spectrum analyzer. I'd love to see definitively what is
happening to the spectrum when I transmit.

Look at any transmitter product review in QST, especially HF gear.
Basically what you will see is a very high spike at the transmit
frequency, with progressively diminishing sidebands for several
hundred Hz either side of the carrier frequency. There will also be
some highly attenuated spikes at periodic intervals above and below
the carrier frequency.

Maybe there is a way I can turn my old oscilloscope into a spectrum
analyzer. hmmmmmmm...

Probably not.

LRod

Master Woodbutcher and seasoned termite

Shamelessly whoring my website since 1999

http://www.woodbutcher.net

Hey - Merry x-mass Rod...

from the cold in Naperville....
Wes

"LRod" wrote in message
...
On 2 Dec 2003 09:32:01 -0800, (KC2MAC) wrote:

Radioman wrote in message
...
Front end overload.

It's like trying to see a candle next to a spotlight shining in your
face.

Even though they are different freqs? I'm transmitting on 146.400,
but listening on 147.00 (-600k offset).

You may think it's a lot, but 600 kHz to an FM radio can be quite
close.

Is there anything I could do to treat the symptom aside from keeping
the antennas of the two units far apart from each other?

See my other response regarding antenna polarization and duplexers.
You could actually build a simple notch filter out of a piece of coax
and a T fitting. It's not going to be very deep, and it will be wider
(in terms of bandwidth) than a duplexer, but every dB helps in this
case.

I wish I had a spectrum analyzer. I'd love to see definitively what is
happening to the spectrum when I transmit.

Look at any transmitter product review in QST, especially HF gear.
Basically what you will see is a very high spike at the transmit
frequency, with progressively diminishing sidebands for several
hundred Hz either side of the carrier frequency. There will also be
some highly attenuated spikes at periodic intervals above and below
the carrier frequency.

Maybe there is a way I can turn my old oscilloscope into a spectrum
analyzer. hmmmmmmm...

Probably not.

LRod

Master Woodbutcher and seasoned termite

Shamelessly whoring my website since 1999

http://www.woodbutcher.net

On Thu, 25 Dec 2003 16:50:59 GMT, "TheTenor"
wrote:

Hey - Merry x-mass Rod...

from the cold in Naperville....
Wes

Holy ****, aren't I safe anywhere?

How're things?

LRod

Master Woodbutcher and seasoned termite

Shamelessly whoring my website since 1999

http://www.woodbutcher.net

On 1 Dec 2003 21:13:04 -0800, (KC2MAC) wrote:


Why is my scanner deaf when I'm transmitting with a separate rig?
Could this have anything to do with near-field emissions? I'm
transmitting with 5 watts of power using a 7.5dB gain omni-directional
antenna. My scanner is always within 10 feet of the antenna.

Yes, the technical, two way trade term for it is desense. One of the
big efforts needed in building a repeater is to isolate the always-on
receiver from the always-on-when-someone's-talking transmitter. They
do that by use of a duplexer and/or antenna separation and
polarization.

Your receiver may not be up to the job, but in any event, its antenna
needs to be as far away from your transmitter antenna as possible. If
the repeater signal is strong enough at your location, you might also
try horizontal polarization for the scanner antenna. That can get you
up to 20 dB isolation from the transmitter antenna, but will cost you
that same 20 dB in strength of the repeater signal.

LRod

Master Woodbutcher and seasoned termite

Shamelessly whoring my website since 1999

http://www.woodbutcher.net