[Elecraft] [KX3] Re: Strong recommendation: MFJ 18xx-series single-band w...

[Ka9p at aol.com]

HI Barry,
 
I expect your antenna is ok, or at least not mislabeled....
 
I don't have a 20 meter version to measure, but I do have the 17 meter  
version.
 
It works fine on 17 with the KX3 with a drag wire or radial.
 
On an AA30, with no counterpoise, it repeatedly measures resonance sharply  
at about 23.4 mHz.  But that's an all plastic analyzer case.  I've  seen it 
lower on my old MFJ with the metal case, but still not resonant without  
any counterpoise.
 
Based on that I'd guess your 17 meter resonance is a coincidence, and the  
result of measuring it as you did, not a mislabeling issue.
 
I've done a lot of work over the last year with analyzers and  small whips 
since Wayne started looking for the Holy Grail mini-antenna,  and I can 
assure you that if you're looking for reliable low SWR and resonance,  you 
should only do the experiment as you intend to use the antenna.
 
With the KX3 as a handheld this meant holding the radio with mounted  
antenna the way you plan to in the field, with a drag wire or radial of the  
length you plan to use, and over the type of ground you expect, strung out as  
you plan to sit, stand or walk.
 
I ended up going with a single 12 in section of Buddistick mast on a  
bracket, a mini or regular coil, and a standard whip.  This is  surprisingly 
light and breaks down to 12 inches. With the regular coil and  a 13 foot drag 
line I can usually manage to do 10 - 30 meters (sadly  will NOT hit 40) with 
preset taps on the coil, sitting on a bench on  average terrain without 
having to use the tuner.  
 
But change anything and it's up for grabs again, hence having a tappable  
coil in the filed is a blessing.
 
Not so necessary with the KX3 and auto tuner, but with an 817 or  KX3  
without tuner, a must.
 
Have fun.
 
Scott ka9p
 
 
In a message dated 4/3/2016 5:38:09 A.M. Central Daylight Time,  
KX3-noreply at yahoogroups.com writes:



Thanks for all the responses.  Don, your comments are much  appreciated and 
I planned on building a bracket just as you describe and  mounting my 
whip/counterpoise to the top of a trekking pole..  


Again, I'm not asking about antenna performance.  I will add the  
counterpoise in actual operation.  I'm asking if anyone out there who  actually owns 
the MFJ-1820T can please connect it directly to a antenna  analyzer and 
check 20M performance.  Yes, I believe these antennas  actually DO resonate just 
as they are.  I believe mine is 17M  (mislabeled), not 20M, and just 
looking to confirm that.


Thanks & 73,
Barry N1EU

On Sun, Apr 3, 2016 at 9:34 AM, Bruce Nourish <_w0mbt at w0mbt.net_ 
(mailto:w0mbt at w0mbt.net) > wrote:

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.barry at gmail.com_ 
(mailto:n1eu.barry at 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











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 Posted by: Barry N1EU <n1eu.barry at gmail.com>   
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