[NLRS] [BC'ers] Fwd: Re: Anybody have experience withmulti-band feeds?

[Donn]

Hi David.

Either dish would work.  The DirecTV is in "wide" use around here for 10GHz,
although with 10GHz only feeds.  When viewed along bore-site its an 18" diameter
dish... the "extra" couple of inches disappear when tilted foreward.  The feed
arm of the dish will be about 15° below level when the beam is on the horizon.
If you don't have the feed arm, the plane of the front edge of the dish should
be about 67° from vertical.

A really good reference is W1GHZ's "Online Antenna Handbook," Chp 5.  You can
find it at http://www.w1ghz.org/antbook/contents.htm.

Its really worth having a copy handy, and reading the whole thing when you've
got free time.

As for making it multiband:  all multiband antennas are a compromise.  It'll
work best, of course, at 10GHz, and with a 10GHz only feed.  Since 10GHz is the
highest frequency of interest, the trick will be to place the phase center of
the Vivaldi for 10GHz at the focal point of the dish.  Yes, the other
frequencies will NOT be optimized, but....

A rough estimate of the gains for an 18" dish:
10GHz       28-29dBi
5.7GHz      24-25
3.4GHz      20-21
2.3GHz      14-15

The "larger" Channel Master dish actually only an 18" dish:  the extra width is
to allow multiple feeds to look at multiple satellites.  Again, when looked at
along its bore-site, its and 18" dish.

Looking forward to seeing you at Aurora and measuring the dish on the range.
It'll be interesting !

73 Donn
WA2VOI/0





----- Original Message ----- 
From: "David Palm" <thepalmhq at gmail.com>
To: <nlrs at mailman.qth.net>; <badgercontesters at mailman.qth.net>
Sent: Tuesday, March 15, 2011 1:44 AM
Subject: Re: [NLRS] [BC'ers] Fwd: Re: Anybody have experience withmulti-band
feeds?


>
>
> I have Aurora 2011 marked out on my calendar and am going to do my best to
> be there with KC9JTL and KF9OP.
>
> Now, I want to get this dish with a multi-band feed ready to try on the
> range.  I will probably have a dedicated dish for 10 GHz (I'll probably be
> asking more about modifying a dish for that later.)  This would be for
> 3456/5760 and, possibly but it seems a stretch, 2304.  I need some advice.
>
> I have the PCB Vivaldi antenna from Kent Britain for the multi-band feed.  I
> currently have two dishes.  Both are offset feed.  One is a normal DirecTV,
> 18" wide and about 20" tall.  The other is a Channel Master, 24" wide and
> 18" tall.
>
> Which, if either of these, would be better and why?  The CM obviously has a
> little more surface area.  If neither of these would be a good match, what
> would you recommend and where would I get it?  And any good ideas on
> mounting the PCB Vivaldi, so that it can be focused for optimum
> illumination?
>
> Thanks and 73,
>
> David  W9HQ
>
>
> On Sat, Feb 5, 2011 at 3:02 PM, Dr. Gerald N. Johnson
> <geraldj at weather.net>wrote:
>
>> Aurora May 14, White Bear Lake MN, if the portable signal sources work,
>> 144 to 10 GHz at least. In the morning providing it doesn't snow.
>>
>> 73, Jerry, K0CQ
>>
>> On 2/5/2011 2:21 PM, David Palm wrote:
>> >
>> >
>> > Thank you all for your very interesting replies.  It seems that if I'm
>> going
>> > to give this a try with a WA5VJB Vivaldi as a multi-band feed, I should
>> > strive to get it someplace where its performance can actually be
>> measured.
>> > So that leads me to the next question.  Are you guys going to have a
>> > get-together with an antenna range this spring, as I think has happened
>> some
>> > years in the past?  If so, I really want to get that on the calendar and
>> try
>> > to drive up for that.
>> >
>> > Thanks again and 73,
>> >
>> > David  W9HQ
>> > ______________________________________________________________
>> >
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