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Search: Posts Made By: rabbit73
Forum: Antennas 30-Jun-2017, 6:31 PM
Replies: 22
Views: 45,949
Posted By rabbit73
http://forum.tvfool.com/attachment.php?attachmenti...

http://forum.tvfool.com/attachment.php?attachmentid=2775&stc=1&d=1498846547

GroundUrMast had to select a frequency to model the antenna; he picked 584 MHz in the middle of the UHF band. Each...
Forum: Antennas 26-Mar-2017, 8:18 PM
Replies: 22
Views: 45,949
Posted By rabbit73
The formula that I use as a first approximation...

The formula that I use as a first approximation for a half wavelength for VHF and UHF is 5540/Freq in MHz with the answer in inches.
...
Forum: Antennas 26-Mar-2017, 7:15 PM
Replies: 22
Views: 45,949
Posted By rabbit73
http://forum.tvfool.com/attachment.php?attachmenti...

http://forum.tvfool.com/attachment.php?attachmentid=2598&stc=1&d=1490555553

I was concerned about a similar problem with a 4-bay UHF bowtie antenna. As the wavefront reaches the antenna, current...
Forum: Antennas 26-Mar-2017, 2:52 AM
Replies: 22
Views: 45,949
Posted By rabbit73
I assume you mean distance between the reflector...

I assume you mean distance between the reflector and bowtie elements. The distance is a function of frequency. The original Channel Master 4221 had the reflector 4.25 inches behind the elements. For...
Forum: Antennas 24-Sep-2015, 11:22 PM
Replies: 22
Views: 45,949
Posted By rabbit73
Thanks for the correction, the photo of your...

Thanks for the correction, the photo of your creation, and the tvfool report.
That scale is a lot better than nothing, and good enough to make comparisons.

Oh, OK, I get it; the 44 dB comes from...
Forum: Antennas 24-Sep-2015, 2:17 PM
Replies: 22
Views: 45,949
Posted By rabbit73
I put labels on your diagram; please check my...

I put labels on your diagram; please check my work.

http://forum.tvfool.com/attachment.php?attachmentid=1633&d=1443136347
Forum: Antennas 24-Sep-2015, 11:43 AM
Replies: 22
Views: 45,949
Posted By rabbit73
Thanks for the sketch. It gives me a good idea of...

Thanks for the sketch. It gives me a good idea of what you are doing.

I've never seen anything like that before, but understand why you call it multi-folded dipole. Glad to hear you are getting...
Forum: Antennas 23-Sep-2015, 5:18 PM
Replies: 22
Views: 45,949
Posted By rabbit73
The yagi antenna has a bandwidth that is much...

The yagi antenna has a bandwidth that is much less than a bowtie antenna, because the yagi is a high "Q" antenna as compared to the bowtie antenna which has a low "Q," as defined by the max allowable...
Forum: Antennas 22-Sep-2015, 1:44 AM
Replies: 22
Views: 45,949
Posted By rabbit73
It is possible to build a 4-bay bowtie antenna...

It is possible to build a 4-bay bowtie antenna for VHF-High, but it would be three times as large as the UHF version. Antenna designs can be scaled to other frequencies. The size is an inverse of...
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