[TowerTalk] Laws of Physics Repealed!

[Roger (K8RI) on TT]

 From my experience with the AV640, I am impressed with it on 40 meters 
(Its lowest band) mounted at 25 and 32 feet with it matching the center 
fed,sloping half wave on average for DX.  Due to its sensitivity to 
nearby objects I wouldn't recommend it as a limited space antenna. OTOH 
if that's the only space available, I'd use one.  Get it as high as 
possible, or convenient.   Tripod roof top mount, short pole or tower.

I do have one caveat for both antennas.  There are a lot of mechanical 
connections for jumpers, coils, traps and stubs subject to corrosion. 
I'm not down wind from any nearby industry, but I still get a lot of 
degradation of solder and Al to Al connections.  The solder turns grey 
and just crumbles away. Al to Al held by screws often gets a buildup 
between the Al pieces.  I have needed to redo a number of the coil and 
jumper connections on the AV640.  I've had good luck with liquid 
Electrical tape. Around here the clear Krylon doesn't last long.  YMMV

As a comparison, All of my C3i antennas (one 7L 6-meter, two 12L 147, 
and two 11L 440s) have had all solder joints for the matching networks 
fail. What solder was left would crumble to powder when rubbed between 
my thumb and fore finger.  Those all had several coats of clear Krylon.  
They are getting liquid electrical tape.

73

Roger (K8RI)


On 10/24/2015 6:48 PM, Jim Brown wrote:
> On Sat,10/24/2015 6:49 AM, Daniel Danny Horvat wrote:
>> There is no R6 antenna, there is a R-6000 antenna which I designed for
>> Cushcraft followed by R8 antenna which was covered in K7LXC & N0AX 
>> report
>> with high score.
>
> Congrats on your work, Danny.  It's not easy getting good performance 
> with small size!
>
>> I was against implementing a 80m on R8 vertical back then (1998) due low
>> efficiency and narrow bandwidth. MFJ has no problem to claim anything 
>> just
>> to sell.
>
> N0AX acknowledged this in his write-up of their tests. Only a fool 
> would expect otherwise. :) His advice for all of these antennas as a 
> class was to buy one rated for at least one band lower than you intend 
> to operate with it.  That is, if you want to work 40, buy one that 
> will work 80, and don't expect good performance on 80M from a 30 ft 
> vertical.
>
>> Verticals,  R5/R7 R6000 R8 and also clones AV620, AV640 are IMO better
>
> My friend K9OR, a very good op on a very small lot in Evanston (near 
> Chicago), has done very well with an AV640 on the roof of his small 
> ranch-style home.
>
>> than 43 foot verticals or even worse CHA250 and clone verticals.
>
> I suggest that anyone considering an HF vertical or other antennas for 
> limited space take a look at these pieces on my website.
>
> http://k9yc.com/VerticalHeight.pdf
>
> http://k9yc.com/43FtVertical.pdf
>
> http://k9yc.com/VertOrHorizontal-Slides.pdf
>
> 73, Jim K9YC
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>
>
>
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-- 

73

Roger (K8RI)


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