[Elecraft] Strong recommendation: MFJ 18xx-series single-band whips for KX3, etc.

[Walter Underwood]

I got the whip for 17m. I figure there is not much difference between a coil at the base of the whip and a coil inside the ATU. Neither one will radiate. So get a whip for the highest band you want to use and let the ATU provide loading for lower bands.

wunder
K6WRU
Walter Underwood
CM87wj
http://observer.wunderwood.org/ (my blog)

> On Mar 23, 2016, at 8:44 PM, Tom Crayner <tcrayner at gmail.com> wrote:
> 
> Wayne,
> 
> Funny you should bring this up, I just received an MFJ-1899T today. Slapped
> a counterpoise on it and at 6 watts running JT9 (in New Jersey) was able to
> be heard (watching PSK Reporter) all the way in CA and Alberta.  Just
> worked a station in MN.
> 
> I'm not even giving the whip a fair chance... I'm sitting in a basement
> with it cranked up to the floor joist over my head, nestled between 4 foot
> fluorescent tubes and metal duct work. It tuned 1.2:1... counterpoise is
> connected to ground thumb screw next to antenna jack.
> 
> I did groove a small piece of 2x4 for the right angle BNC connector to be
> cradled on so all that weight of the telescopic whip doesn't damage the
> jack...
> 
> Can't wait to take this down to the shore in a few weeks and see what it
> can really do without all the disadvantages I've placed on it tonight....
> :-)
> 
> Tom, W2YF
> 
> 
> On Wed, Mar 23, 2016 at 10:12 PM, Wayne Burdick <n6kr at 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 at 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 tcrayner at gmail.com
>> 
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at 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 wunder at wunderwood.org