Notices

antenna coupler

Old 04-20-2007, 04:04 PM
  #1  
Senior MemberCaptains Club Member
Thread Starter
 
Join Date: Jan 2007
Location: Tampa Florida
Posts: 4,633
Default antenna coupler

what does the antenna coupler actually do other than provide a connection between coax and antenna? does it contain filters or boosters, pre-amps?
Rolandt03 is offline  
Old 04-20-2007, 04:42 PM
  #2  
Senior Member
 
Join Date: Jan 2007
Location: Whacksonville, Fl
Posts: 724
Default Re: antenna coupler

Yes- filters and preamps.
prodigalson is offline  
Old 04-20-2007, 05:10 PM
  #3  
Senior Member
 
Join Date: Aug 2006
Location:
Posts: 219
Default Re: antenna coupler

(Marine Auto Tuners)

Actually they do not contain preamps. They contain inductors and capacitors and relays as well as a microprocessor that contains the math to switch the inductors and capacitors in or out of the circuit. The inductors and capacitors are switched in with the relays and are what is used to match the lenght of the antenna wire to the sampled transmitted frequency.

Preamps are contained in the radio equipment.
Radio University is offline  
Old 04-20-2007, 05:42 PM
  #4  
Senior Member
 
Join Date: Jan 2007
Location: Whacksonville, Fl
Posts: 724
Default Re: antenna coupler

I stand corrected.
prodigalson is offline  
Old 04-21-2007, 01:05 PM
  #5  
Senior Member
 
Join Date: Aug 2006
Location:
Posts: 219
Default Re: antenna coupler

prodigalson,

Actually you are correct if he was referring to a Loran antenna coupler. I was assuming he was talking about a marine SSB auto tuner (also know as coupler)...
Radio University is offline  
Old 04-21-2007, 07:33 PM
  #6  
Senior Member
 
Join Date: Jan 2007
Location: Whacksonville, Fl
Posts: 724
Default Re: antenna coupler

I was thinking of Loran, myself.

I coulda sworn that they had amps inside (though it's been years since I did anything with one besides throw it away).

Thanks!
prodigalson is offline  
Old 04-25-2007, 12:48 AM
  #7  
Senior Member
 
Join Date: Dec 2002
Location: Southeast Michigan
Posts: 2,571
Default RE: antenna coupler

Rolandt03 - 4/20/2007 4:04 PM

what does the antenna coupler actually do other than provide a connection between coax and antenna? does it contain filters or boosters, pre-amps?
An antenna coupler is also called an antenna tuning unit. An antenna tuning unit (ATU) typically contains capacitive or inductive reactances arranged in such a way as to transform the antenna feed point impedance to match the characteristic impedance of the transmission line feeding the antenna. This allows for maximum transfer of energy from the feed line to the antenna. The components in the ATU should be as lossless as possible so that they do not dissipate any of the energy in the ATU itself. When a conjugate match has been obtained between the antenna and the transmission line, it works in both directions, that is, on transmit the transmitter's energy is effectively coupled to the antenna, and on receive the energy picked up by the antenna is effectively coupled into the receiver.

Modern ATU's have the ability to self-adjust, that is to automatically adjust their settings to produce the best possible transfer of energy between the transmission line and antenna. This type of Automatic-ATU is useful when a non-resonant antenna is used over a wide range of frequencies or bands.

It is extremely common that the arrangement of reactive elements in an ATU will produce a filtering effect, although this is a secondary result; the primary concern is to match impedances. In more sophisticated antenna systems the filter effect must be considered as it can cause problems with variations in a modulated signal.

In the case of LORAN antennas used for receive-only, it is common for a pre-amplifier to be built into the antenna coupler. The frequency of all LORAN-C transmissions is 0.1-MHz and all practical receive antennas are extremely short (in terms of their electrical length). This causes them to be quiet inefficient and to produce poor signal strength. A pre-amplifier in the antenna base itself is often utilized to boast the received signals to a higher level. Some LORAN antennas are not really classical vertical monopole antennas but rather are voltage probe antennas which require very high gain amplifiers to produce useable signals.

So, yes, there is a lot more going on inside an ATU than just a box to house the connectors for the antenna and the transmission line and to connect them together.
jhebert is offline  

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are Off


Thread Tools
Search this Thread