Did you have a counterpoise when you swept the antenna? If not, you're only looking at half your antenna, especially as the RigExpert is almost all plastic.
On Sun, Apr 3, 2016, 01:15 Barry N1EU <n1eu.ba...@gmail.com> wrote: > If anyone else out there has an MFJ-1820T and also an antenna analyzer, I > wonder if you could please do me a favor. Please just connect the whip > directly to the analyzer and tell me what the SWR looks like across the 20M > and the 17M bands. > > I swept my MFJ-1820T with my Rig Expert AA-30 and my MFJ-1820T is resonant > on 17M, not 20M. I'm wondering if I have a mislabeled MFJ-1817T. > > Thanks & 73, > Barry N1EU > > On Thu, Mar 24, 2016 at 2:12 AM, 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 w0...@w0mbt.net > ______________________________________________________________ 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
