[NLRS] 70-cm Antenna Dilemma

[Donn Baker]

Hi Carl,
Need to ask some questions.
Other than changing the antenna, what ELSE was changed ?  Was it the same
feedline ?  Same jumpers in the shack ?  Same radio or transverter ?  Same
preamp ?  Where is the preamp located ?  How good are you measurements
(i.e., 20 dB above the noise) ?  How do you KNOW that you're down 40 to 50
dB ?  Who/what says ?

I ask all this stuff 'cause it seems strange that if the antenna were "bad"
(which is certainly possible), NOTHING CHANGED when you put up a different
antenna.  (I doubt BOTH are bad.)  

On the other hand, its also possible that something other than the
antenna(s) could be at fault... cable run, cable in the shack, bad
connector(s), bad receiver, blown pre-amp, etc.  Obviously, these would
need to be common with both antennas, so I had to ask.

Do you hear other stations ?  How well ?  Could the problem be at the OTHER
end of your 50 mile path (that is; your OK, but the other station is bad) ?

Where/how did you measure the SWR ?  AT the antenna(s), or at the end of
the feed line in the shack ?

73 Donn
WA2VOI/0



At 07:03 6/7/06 -0500, Carl Estey wrote:
>
>
>In the Spring of 2005 I obtained a used 16-element 432-Mhz yagii of un-known
>design.  When I got it up on a 40’ tower and fed it with 65’ of LMR-400 I
>found performance over a 50-mile path very poor.  Last week I put up a 48’
>piece of Andrew 7/8” Heliax and a 15’ LMR-400 Ultraflex jumper at the
>antenna the best I can do on a fifty mile path with 100-watts at both ends
>is 20-24 db above the noise – somewhere there is a loss of 40-50 db!!
>Physical exam of the antenna shows nothing wrong, which makes me think the
>balun is the problem – and it is a ½ diameter six-inch long tube that is
>sealed (soldered) on the end with the female N-connector.  One the opposite
>end of the balun from the N-connector are flat zig-zagged metal straps that
>go to several of the elements.  Does anyone recognize the design of this
>16-element antenna and have any specs on it?
>