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

Tue Mar 29 11:34:54 EDT 2016

How about putting a grounding lug on the chassis BNC?

http://www.amphenolrf.com/031-10152-rfx.html <http://www.amphenolrf.com/031-10152-rfx.html>

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

> On Mar 29, 2016, at 8:28 AM, Bruce Nourish <w0mbt at w0mbt.net> wrote:
> 
> I'm always terrified of losing the thumbscrew in the grass. I wish MFJ made
> these with a built-in right angle and a binding post, or even just a bolt
> and a wing nut, at the base.
> 
> On Tue, Mar 29, 2016 at 8:21 AM Wayne Burdick <n6kr at elecraft.com> wrote:
> 
>> Use one of the KX3's thumbscrews. We relieved the paint on the chassis at
>> these points so you can use them for counterpoise wires or ground.
>> 
>> Wayne
>> N6KR
>> 
>> 
>> On Mar 29, 2016, at 5:14 AM, "Barry N1EU n1eu.barry at gmail.com [KX3]" <
>> KX3-noreply at yahoogroups.com> wrote:
>> 
>>> 
>>> 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 <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
>>> 
>>> 
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