[NLRS] Old 2M antenna Question

[Dr. Gerald N. Johnson]

Point it skyward to get most of the RF away from reflectors. Often what 
leaks out the back is small enough to minimize the effects of ground 
behind the beam.

For some KLM antennas M2 offers support yet since at least one of the 
proprietors of KLM is now with M2. But their web site shows links for 
KLM manuals but the links don't work. E-mail them I guess.

I hope you are feeding it with the coaxial sleeve balun and that the 
wires are soldered well at the balun and connected to soldered crimp 
lugs at the antenna end. I had a KLM with a 4 element feeder and those 
connections gave problems out in the weather. I don't think I ever 
checked the SWR though, just got times where it didn't hear well. Water 
got in a crimp lug and froze loosening the connection. In the time your 
antenna has been in the box corrosion could have done the same. The wire 
length and spacing may also be critical.

I had a M2 5WL up for 2m for quite a while. It had comparable gain to 
the 20-LBX but was way too directive. 15 degrees at the 3 dB points is 
narrower than the brake notches on my rotor so it was hard to peak on 
signals. I concluded that a pair of 9 element taken from K1FO designs 
stacked 10 or 12 feet vertically will give nearly the same gain, but 
have twice the azimuth beamwidth for easier aiming. K1FO said the 
antennas shorter than 12 elements were not optimized but I like the 
patterns when modeled and while the G/T could be improved for 
terrestrial work hearing signals 25 or 30 dB down off the sides and back 
is better than not hearing them when they are 40 or 50 dB down off the 
side and back. So far the 432 version I built has tested with greater 
gain on the CSVHF antenna range than the somputer model. I mentioned 
that in my paper on "how Close can they be stacked" a few years ago. 
www.geraldj.networkiowa.com/papers/CSVHF2011/HowCloseB.pdf
I plan to use 3 on 432 in between the two 2m.

Many years ago, probably summer of 1967, I modified a W1HDQ yagi and a 
crumcarft 11 element 432 yagi with gamma matches on each. I tuned them 
up in an ISU lab (the old machinery lab) with signal generator and 
return loss bridge. I could detect another grad student at a distance of 
at least 40 feet when he moved through the main lobe.

73, Jerry, KCQ

On 4/19/2015 7:22 PM, Mike King - KM0T wrote:
>
>
> Hi all,
>
>
>
> I resurrected an old KLM 2M-20LBX.  I got it about 5 years ago from some
> deal I was swinging and it was brand new in the box, never opened until this
> weekend.  The instruction manual says 1990!
>
>
>
> Anyway, its 38.5' long and it looks awesome put together.  It was a really
> nice kit and went together very well.
>
>
>
> So, the question I have for some of you that were around and on the air back
> when that was a popular antenna.  I can only get it to about 12' for
> testing, and I get a 1.7 SWR.  I'm assuming it's an issue with being too
> close to ground to get an accurate reading.
>
>
>
> When I get it on the tower, it will be hard to get at again.  However, it
> does not appear that there is any way to adjust the antenna for SWR.
>
>
>
> So I was wondering if any of you recall what kind of SWRs you were seeing
> when you got this beast up in the air?
>
>
>
> Incidentally, it's a dual driven element system with crossed phase bars, so
> the bandwidth is wide.  Not that I need that, cause I'm never going to use
> it above 145 Mhz.
>
>
>
> Any other anecdotal info appreciated..i.e. was it a good antenna or not?  Or
> did I just spend the weekend practicing putting antennas together and move
> on to a newer unit?
>
>
>
> 73 and Thanks,
>
>
>
> Mike - KM0T
>
> EN13VB.
>
>
>
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