At W4NJA (3A) for Field Day we use three Dipoles (Cut for the low end of 80 meters) fed with 450 Ohm ladder line into a DXEngineering Balun with less than ten feet of coax into the rig. The feed line is cut at odd multiples and the antennas are spaced in a straight line end to end with separation of course. We can run three stations on the same band but different modes with no interaction. We used to use G5RV's, verticals, beams etc. but have opted for this configuration because it works. No problem with K3's, Omni VII's tuners to tune the bands. I have the actual length's that the three are cut for but they are stored at another location. I actually got the information from DXEngineering somewhere on their web pages.
Ed.. AB4IQ -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Don Wilhelm Sent: Thursday, October 10, 2019 6:44 PM To: Bob McGraw K4TAX <[email protected]>; [email protected] Subject: Re: [Elecraft] Center-fed antennas 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 On 10/10/2019 7:12 PM, Bob McGraw K4TAX wrote: > I thought a Band Pass Filter at each station resolved that issue. > > 73 > > Bob, K4TAX > > On 10/10/2019 5:27 PM, Ken G Kopp wrote: >> Well-said, Don. >> >> 73! >> >> Ken Kopp - K0PP >> >> On Thu, Oct 10, 2019, 16:23 Don Wilhelm <[email protected]> wrote: >> >>> All this talk of multi-band antennas for Field Day ignores the >>> problem of multi-station Field Day operation. >>> There is sufficient pickup of one transmitter's energy on the >>> antenna being used by a receiver on another band. >>> For that reason, my club has banned the use of multiband antennas >>> for Field Day operation. >>> >>> For a single station Field Day operation, the multiband antennas are >>> great. >>> >>> 73, >>> Don W3FPR >>> ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
