[Elecraft] Center-fed antennas

[Joe Subich, W4TV]

The one "multiband" antenna one can use in a multi-transmitter
configuration is the flat-top with open wire feeders and a
*Link coupled* tuner.  The link coupled tuner is a bandpass filter
that significantly reduces harmonic/broadband noise just like the
"Q" of a single band antenna.

73,

    ... Joe, W4TV


On 2019-10-10 7:44 PM, Don Wilhelm wrote:
> Bob,
> 
> Bandpass filters at each station will help a lot, but they do not have 
> infinite out of band rejection.
> There is still a huge benefit with single band antennas.  My club uses 
> both.
> 
> Last Field Day (3F operation) one station got on the air with a 
> multiband vertical, and all other operators jumped on that operator to 
> shut him down quickly!  The multi-band antenna radiated harmonics of the 
> radio.  Even though the transmitter met the -43 dB harmonic required by 
> the FCC, the proximity of the multiband antenna to other antennas caused 
> problems (that station was not using a bandpass filter).
> 
> So for Field Day multi-station operation, single band antennas, bandpass 
> filters and transmitters with low phase noise are important.  We were 
> not able to orient the antennas end to end due to space considerations 
> at the EOC site, so we had to compromise on that, which makes the other 
> factors very important.
> 
> I need to point out that as an experiment, a 2nd station used an antenna 
> on 20 meters separated from the main 20 meters, and we were able to 
> operate one on CW (K3) at the same time as the other station (Icom) used 
> digital and SSB modes.  We had some mutual interference, but it was 
> minimal.  The K3 did not interfere much with the Icom due to the K3's 
> low phase noise, but the Icom did raise the background noise level on 
> the K3.
> 
> 73,
> Don W3FPR
>