"Wilbur Hubbard" wrote in message
anews.com...
"Hanz" wrote in message
...
Can I use the 735 without the antenna tuner to only receive signals (no
transmission)? What happens if I key the mike without the antenna tuner?

Thanx.




The purpose of an antenna tuner is to electronically lengthen or shorten
the physical antenna so as to better match the wavelength of a particular
broadcast frequency. Whole waves, half waves quarter waves are better than
some random wavelength chopping when it comes to propagation and reception
on the other end.

Operating without the tuner will not harm your transmitter. It will only
degrade its transmit efficiency somewhat.

Cross-posted to AFPF in the hopes that one Lloyd Bonafide who is a radio
expert might comment and affirm my thoughts.

Wilbur Hubbard


For maximum power transmitted from the radio the antenna impedance has to be
the complex conjugate of the output impedance of the radio transmitter. So
the antenna and radio must have the same resistive (real) impedance and
their reactive (imaginary) impedances must sum to zero. If the impedances
are not matched, the voltage waves from the transmitter will reflect from
the antenna input and travel back to the transmitter. The could result in
heating of the output amplifier and eventually lead to its destruction. The
antenna length determines its input impedance and radiation pattern. The
tuner, at its simplest, is an electronic network, usually pi configured, and
works to transform the real part of the two impedances to be equal at a
given frequency and the reactive parts to be zero. Multiple pi stages allow
greater tuning ranges.

Bottom line, you can probably get away with short transmissions (like in
aircraft) and intermittently heat up your output stage. If your life depends
on it, get a tuner. You can use an SWR bridge to measure the degree of
mistune:

http://www.packetradio.com/catalog/i...oducts_id=2174

The amateur radio gear will work for marine radio, for $40 it's a handy
thing to have, considering a shop will charge you more for the service.

You can receive without damage with no tuner.
You may damage the radio by transmitting without a tuner.

I just looked up that ICOM-735. It's an amateur radio rig, I thought you
were asking about marine radio. Do you have a license to operate it? If
you did you wouldn't be asking that type of question and you would know how
to get around the heating up the output stage. If you don't have a general
class or better license, don't operate that radio - it's illegal. Keep the
stooges on the internet and off of the airwaves.