[opendtv] Re: Build a 3 bay Rhombic Antenna with 20 dB of gain!
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Sun, 12 Oct 2008 20:18:22 -0400
Cliff Benham posted:
> From TV Technology, Jan, 2008
>
http://www.tvtechnology.com/article/11412
But rhombics are huge, comparatively.
The takeaway for me is that your best performance-to-size ratio goes to
the vertical dipole stacks with reflector, either one or two stacks,
side by side. They are quite good for high VHF through UHF, and they are
not nearly as directional as yagis. Similar gain to yagis, but much less
directional. Sounds like a good deal for most markets in the US (and
Italy).
In UHF, you get 13.7 dB of gain with a single stack of 4 bowties, and
15.8 dB with two of these side by side. It seems to me that the two
stacks side by side should be somewhat more directional in the
horizontal plane than the single stack. Would be interesting to try a
dual stack, with the two angled instead of mounted together as one flat
panel.
The article by Doug Lung says about the dual stacks of 4 bowties, with
reflector:
"FCC DTV planning factors are based on antenna gains of 4 dB, 6 dB and
10 dB for low-VHF (Channels 2-6), high-VHF (7-13) and UHF (14-69)
respectively. Kerry Cozad of Dielectric measured the Channel Master
Model 4228 eight-bay bowtie-with-screen UHF antenna and measured gains
of approximately 3 dB, 9 dB and 15 dB for low-VHF, high-VHF and UHF.
This UHF-only antenna exceeds the planning factor gain at both high-VHF
and UHF!"
I believe that Channel Master antenna is discontinued, but don't
despair. There is an exact equivalent available from Antennas Direct:
http://www.solidsignal.com/prod_display.asp?PROD=AD-DB8
And they also sell half of that, a single stack, called the DB4.
http://www.solidsignal.com/prod_display.asp?PROD=AD-DB4
Bert
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