[BC] Re: Commercial Station Feeding A Translator

[Al Wolfe]

    The purpose of my post was to point out an adantage of the echelon 
receiving antenna method providing an additional degree of rejection of 
unwanted signals.  I also contend that it provides a degree of gain and 
space diversity just by having more aluminum in the air in a different 
space.

    It the station you wish to receive circularly polarised? Then a circular 
receiving antenna system might help. Of course reflected signals could be 
out of phase and be distructive. Perhaps a vertically polarised yagi with 
its own receiver added to the mix is in order.

    If this is really important and you have the budget for it then 
additional receiving sites at different heights on your tower could be used, 
with each feeding a seperate receiver and some sort of S/N selector, or 
voter, picking the best signal.

    90 miles and 99.99 % reliability is still going to be tough to do in any 
case.

Al Wolfe, retired, mostly


> From: RichardBJohnson at comcast.net
> Subject: Re: [BC] Re: Commercial Station Feeding A Commercial
> Translator
>
>
>> radiation/reception pattern with a specific center of radiation.  One
>> element (antenna) cannot augment another unless they feed separate
>> receivers and a circuit decides which one is providing the best signal
>> at the moment.
>
> Sure they can and antenna manufacturers even make precut stacking
> harnesses for such use. A signal that arrives in phase from one
> antenna combines with another similar signal, resulting in twice the
> signal voltage. Noise, however, combines as sqrt(2) = 1.4, so every
> pair of similar antennas that form an array not only increases the signal,
> but also (potentially) improves S/N.
>
> However in the subject case, at 90 miles, the signal would have to go
> through the earth and even if the TX/RX antennas were high enough
> there might be Fresnel zone problems causing instability.
>
> --
> Cheers,
> Richard B. Johnson
> Read about my book
> http://www.LymanSchool.org
>
>
> -------------- Original message ----------------------
> From: RADIO DOCTOR <lylehenry at fastmail.fm>
>> On Wed, 17 Oct 2007, Al Wolfe wrote:
>>
>> >   They called this the "echelon" antenna configuration. Besides the
>> > almost three db gain over one antenna, you supposedly get about twenty
>> > db additional rejection from the rear. Also gain some space diversity.
>>
>> Taking issue with the space diversity part.  Antenna elements that are
>> combined to a single receiver become an array which has a
>> radiation/reception pattern with a specific center of radiation.  One
>> element (antenna) cannot augment another unless they feed separate
>> receivers and a circuit decides which one is providing the best signal
>> at the moment.  That's the principle of diversity reception, though I'm
>> sure it can be stated much better.
>>
>>