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Re: Elk Antennas for HTs?

Hello Doug,

>I assume that the reason there are two connectors is because there's
>two antennas, for two bands.  You may be using two radios with it.

Or one radio with two connections.  I've used the Arrow with two radios, 
but the receive radio also desensed.

>Also, I would expect that putting a T connector in there rather than a
>duplexer (for use with a single radio with a single antenna jack)
>might waste some power, as the 2m yagi would be approximately resonant
>at 70cm, but it's director/reflector dimensions would be all wrong
>causing a wierd pattern that's probably not what you want.

Since I was not transmitting on 70cm this wasn't a consideration.  I was 
only receiving on 70cm.

>Of course.  However, I don't see how an Arrow antenna with a duplexer
>(probably built into the handle) is fundamentally any different than
>the Elk antenna without one.
>(Of course, they're different types of antennas, with different
>specifications, but ultimately, both setups provide relatively high
>gains in the 2m and 70cm bands, and both provide one connection for
>your radio.)

OK - you have me scratching my head about this.  I can see two 
possibilities.  The first could be that the 2m side of the duplexer (which 
is a low pass filter) filters out any harmonics above the filter cutoff 
frequency.  But perhaps the high-pass filter on the 70cm side of the 
duplexer also provides isolation by stopping any 2m energy coming back that 
might ultimately produce harmonics.  I suppose it could go either way - I 
think if I have the time I'll tear my duplexer apart and run some tests on it.

>| The original statement was about the IC-W32A which I own (I do not
>| own the other radios you mention) so I can't speak for their built
>| in duplexers.  However I don't believe the FT-530 is full duplex.
>It is.

I wonder if it is a setting - I recall someone using one and when they 
transmitted the receiver muted.

>Since you're transmitting and receiving on the same wire coming out of
>your radio, I'm not really sure how an external duplexer is going to
>prevent this -- if the duplexer inside your radio cannot provide
>adequate isolation, I don't see how an external duplexer can do it.

Can't help you there - all I know is what my experience was when I owned one.

>I wonder if the problem you had with the Elk antenna was a higher SWR
>(higher than with the Arrow antenna) on your transmitting band -- that
>would send more signal back to the radio, which would cause more
>signal to get past the internal duplexer, desensing more ...

One would hope that wasn't the case as it was a brand new antenna - I 
didn't own a VSWR meter at the time, but it worked fine with my base and 
mobile on both bands as long as I wasn't operating full duplex.

>I'm looking to make an antenna for satellite work.  (I could buy one,
>but it seems simple enough to make one.)  I was thinking of the arrow
>(two yagis at 90 degrees) design, but the log periodic used by the Elk
>certainly seems simpler and more portable, and no duplexer needed (for
>my setup) is a nice bonus.  (Yes, I realize that I could use a T
>connector, but I think that will cause problems as I mentioned
>before.)  I'm trying to decide with which way to go (or maybe I should
>just do both :)

Hamantenna in Quebec makes a duplexer kit that is very affordable (I think 
$14US) - that is what I use.

You might also want to take a look at Alex Diaz's Yagi design - more gain 
than the Arrow and looks like it has wider bandwidth (though that probably 
depends on the thickness of the elements you use.)

>It's funny about antennas ... I've found them fascinating, and have
>read just about everything I've found on them, but the more I learn,
>the more I realize I don't know.  This is true about most things, I
>know, but seems much more pronounced with antennas ...

I feel the same way - though in the long run the antenna itself is only a 
matter of understanding Maxwell's Equations.  It's all the other aspects of 
them that is a constant fascination and or burden depending on whether or 
not it achieves the desired results.  It's probably why I only comment on 
antennas I actually own and have tested.



W0EEC - CM87tm
AMSAT Area Coordinator - San Francisco Bay Area
http://www.projectoscar.net    http://www.PlanetEmily.com 

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