Probably a dumb question, but any suggestions on how to connect counterpoise wires using the MFJ-1820T? The loaded whip terminates in a male BNC, which I assume is intended to connect directly to the KX3 antenna jack. It's not obvious to me how to add counterpoise wires???
Thanks & 73, Barry N1EU On Wed, Mar 23, 2016 at 10:12 PM, Wayne Burdick <n...@elecraft.com> wrote: > Hi all, > > I've been using an MFJ-1820T telescoping 20-meter whip for a few months. > Considering its length (48"), results have been excellent. I typically use > it with the KX3 on a picnic table at 15 W (with an external battery), or > hand-held at 3 to 5 W (internal battery). > > During the ARRL DX contest I worked many countries in CW and RTTY modes, > and have also had a number of longer QSOs on 20-meter SSB. Of course at > these power levels, with an electrically short whip, good band conditions > can't hurt. > > I prefer a 25' or so wire-in-a-tree antenna when there's time. But when I > need a quick deployment antenna that weighs very little, I pull out the > 1820T. Note that you *must* use at least one counterpose wire. More than > one helps, but all of the QSOs I described were made with a single 13'-long > wire laid out on the ground. With no ground wire, you'll be down some 15 to > 20 dB in transmit mode. > > Since the 20-meter results were so good, I also bought the whips for 40, > 17, 15, and 10 meters. 40 meters is a rough ride at 48", but I was still > able to check into daytime SSB nets all over the west coast running 10 W. > On the higher bands, results improve as you go higher in frequency. I > worked a few JAs on 15 meter SSB running just 1 watt. > > A traditional problem with such antennas is that the the SWR can sometimes > be unexpectedly high, requiring that you micro-adjust the telescoping > length and/or adjust the length of the counterpoise wire. This is > completely unnecessary if you have an auto-tuner available. In particular, > the KX3's ATU can quickly match any of these whips over their full target > band. In a pinch the ATU can also match a given whip on adjacent bands. In > the DX contest mentioned I tuned up the 20-meter whip on 17 and 15 meters > as well, and made a few Q's there, despite the losses due to off-resonance > operation. > > These whips can handle a surprising amount of power. They're rated to 25 > W, but I ran 50 W through the 20-meter version for several minutes without > damaging it. Some other compact whips I've tried overheated quickly even at > 10 W, including some of the Maldol models. When this happens, the SWR goes > up and stays up until the coil cools down. > > Caveat: Always use a full-size antenna when possible. But if you've just > crested a new hill and only have a couple of minutes to see if the RF > really is greener on the other side, this is an excellent choice. > > 73, > Wayne > N6KR > > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to n1eu.ba...@gmail.com > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
