[TowerTalk] R8 vs 6BTV, etc.

[K8RI on Tower Talk]

>>
>> Presumably there are mechanical differences in hardware, etc., but what 
>> I'm
>> really looking for is any noticeable "power sucking loads" that are 
>> inherent
>> in the design (sure, our vertical has a 2:1 SWR bandwidth of 200kHz on 
>> 80..
>> we have a 10 dB pad in the 80m trap!)
>>
>
> There are certainly differences in the way they are fed.  The 6BTV is
> bottom fed with radials, while the R8 has a choke balun and matching
> transformer (see <http://www.iol.ie/~bravo/r7_vertical.htm> for details
> on the similar R7) with counterpoise elements which are much shorter
> than a quarter-wave radial.  The effective length of the R8 is somewhat
> longer than a quarter wave on each band (I'm not sure if it is an
> electrical half-wave, however).
>
> The Hy-Gain AV-640 is similar to the R8, but uses top-loading coils and
> capacity hats for decoupling instead of traps.  Both of these have
> separate vertical elements for the higher-frequency bands.  Neither of
> these is rated for 80 meters.

I have an AV 640 on a brand X Aluminum tower mounted on the West end of my 
shop.
It works very well on 40 and quite good on the rest of the bands except 20. 
The match is good, but it appears to be a good dummy load on 20.  I've never 
taken the time to trouble shoot it to find out the problem.  It has a good 
looking SWR curve that is very close to what the manual predicts, but it 
neither hears, or gets out well on 20.


Roger Halstead (K8RI, EN73 & ARRL Life Member)
N833R, World's Oldest Debonair (S# CD-2)
www.rogerhalstead.com
> The K7LXC/N0AX report on verticals has some interesting comparisons of
> several different models.
>
> 73, Bob N7XY
> _______________________________________________
>
> See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless 
> Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with 
> any questions and ask for Sherman, W2FLA.
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk at contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>