Redesigned DB-2 & DB-4 for UHF & VHF-HI - Page 3 - Canadian TV, Computing and Home Theatre Forums

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post #31 of 36 (permalink) Old 2010-10-24, 11:24 AM
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Stacking vertically will compress the beamwidth in the elevation plane while leaving the horizontal beamwidth relatively unchanged.

Stacking horizontally will have the opposite effect.
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post #32 of 36 (permalink) Old 2010-10-24, 08:27 PM
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It's great that this antenna is being made specifically for the spectrum 7-51 with the best gains from 14-51. I can't wait to see the tests when these bad boys come out, I think the best way is to get a very high gain VHF antenna and combine it with this new antenna to get the best over all signal for my area. This is something to look forward too.
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post #33 of 36 (permalink) Old 2010-10-24, 11:24 PM
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Yep I'm wanting to replace my antenna, when I get a new HD set, so I may consider this one if it turns out to be good. Looks like all our channels except maybe one will be UHF anyway, can't wait for the results to come out.
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post #34 of 36 (permalink) Old 2010-10-25, 11:13 AM
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No more info on when they'll be available I guess?
My best guess is production will commence sometime between Thanksgiving and Valentines Day. The engineer is still finalizing the DB4 phasing lines, then the plastics engineer needs to design the molds for the plastic pieces, the molds have to be built, the plastic pieces have to be produced, then the antenna assembly can be done. It's a long tail that wags the dog on a new product!

Give Mini-Circuits a call re Surface Mount Device (SMD) Balun Transformers, but it looks
like the loss at 700 MHz might be closer to 1.5+ dB:
PS: 200:50-ohm is IDENTICAL to 300:75-ohm transformer.....both are 4:1 impedance RATIO....
We have already investigated this idea and rejected it. While the impedance transformation ratio is correct, we don't know know what kind of mismatch losses would be incurred using a device specified by the manufacturer for different impedances than our design intention. It would probably work okay for some of our antennas at certain frequencies, but our engineer indicated he wasn't interested in the 50:200 baluns. He's the one with all the degrees and design experience, so I'll defer to his judgment.

Anaren Microwave claimed a loss of under 1.0 dB up thru 700 MHz, although the loss at the
lowest frequencies appears to be a bit higher....BUT, since external noise usually predominates
at the lower freqs (vice thermal noise), a bit more loss at low freqs can be readily tolerated:
I didn't see the above item listed on their give them a call:
I called them last winter. Vaporware. Product was never produced. I have found an interesting candidate from Murata (DXP18BN7514T) that we may look into.

It's great that this antenna is being made specifically for the spectrum 7-51 with the best gains from 14-51.
See post #15, please. I haven't seen any simulation data on high-VHF yet, so I'm suggesting that UHF performance be the subject of conversation. Please also remember that our ClearStream UHF antennas were specifically designed for 14-51 and have been on the market for two years. So far, they're the only commercially available antennas designed for the new UHF band.

As far as other new stuff that's already in stock, we already have a cute little variable line amp available along with our new coaxial 5-in-1 tool (perfect for the homeowner or the weekend warrior). This week, we should be adding a 15' telescoping mount to the website ...but I digress from the subject of this thread.

Regards to all!

Last edited by ADTech; 2010-10-25 at 02:15 PM.
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post #35 of 36 (permalink) Old 2010-10-26, 03:34 PM
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Location: San Diego, CA
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When considering using a component outside it's "spec region", a quick TEST is indicated....
Perhaps you can get the manufacturer to do the test....and if not, request a sample to test
and talk to them about adding a suitable test to a production run....

This happens much more frequently than one would expect.....and of course, the more units
you threaten to buy, the more they might be interested in helping make a sale.....
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post #36 of 36 (permalink) Old 2010-10-28, 01:47 AM
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Location: Mississauga
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I wonder if this antenna will have a better edge over the CM4221HD and also the Beam Width. How long will it take until we find out the true specs. They claim a gain of 15 db . something which seems incredible but I wont buy it until the good antenna experts here can vouch for it.
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