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Antennas and Coax Forum Discussion on the development and implementation of antennas for radio monitoring activities.

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Old 07-01-2007, 07:13 PM
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Default Ant - folded dipole for 460 mhz?

I salvaged this antenna from the top of a building that we bought:

http://picasaweb.google.com/kickingtrbo/Antenna <-- photo

From what I read, this is a folded dipole array. The elements are 11 inches long x 2 inches across.

I am guessing that this was used for the 450 or 460 mhz business band - likely a repeater.

Is it possible to re-tune for use on the 70cm ham band?

Would it make a good antenna for monitoring UHF with a scanner?

I found a similar antenna here, 8.5 dB gain, $980.00: http://tinyurl.com/3bny9r


Thanks.
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Old 07-01-2007, 07:33 PM
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Retuning for 70cm would mean making the elements longer, essentially rebuilding the antenna with new elements and reusing as much of the hardware as possible.

As a scanner antenna, it has real possibilities for the UHF business band.

Quote:
Originally Posted by kkn50
I salvaged this antenna from the top of a building that we bought:

http://picasaweb.google.com/kickingtrbo/Antenna <-- photo

From what I read, this is a folded dipole array. The elements are 11 inches long x 2 inches across.

I am guessing that this was used for the 450 or 460 mhz business band - likely a repeater.

Is it possible to re-tune for use on the 70cm ham band?

Would it make a good antenna for monitoring UHF with a scanner?

I found a similar antenna here, 8.5 dB gain, $980.00: http://tinyurl.com/3bny9r


Thanks.
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Old 07-01-2007, 07:35 PM
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Quote:
Originally Posted by Don_Burke
Retuning for 70cm would mean making the elements longer, essentially rebuilding the antenna with new elements and reusing as much of the hardware as possible.

As a scanner antenna, it has real possibilities for the UHF business band.
That's what I was afraid of. It will have to be a scanner antenna.

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Old 07-01-2007, 08:20 PM
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That is made by DB Products. I have several here. You should see a model number like DB-404B. If the last digit is a "B", then it will TX from 440-470 no problems. If it is an "A", then it will do 406-420. The ones I have are the "A" model. The best I can get out of them is 430~ish. ham is out on the "A" models, but they still receice like a dream on UHF - doesn't matter what the frequency is.
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Old 07-01-2007, 08:22 PM
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If you're looking to get rid of it, give me a shout. I have LOTS of stuff to trade.
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Old 07-01-2007, 08:30 PM
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I also have a DB-404 and had a few DB-408s in the 450-470 range and they work great down to 440MHz. The elements are very broad band but if you get too much out of band they will take on some down tilt or possibly up tilt due to the phasing harness being too long or short. If you order a new DB-404 with down tilt for high mountain top use the harness will be a different length and the VSWR spec will be a little worse.
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Old 07-01-2007, 08:41 PM
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If you're just going to use it for monitoring purposes, I'll trade you a model "A" for your model "B". It'll still work like a champ. I just need a TX antenna for my repeater.
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Old 07-01-2007, 09:15 PM
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The label is very worn. Can not read the name but can read "Model TDE7260A", "Transmit 450-470"
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Old 07-01-2007, 09:16 PM
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Quote:
Originally Posted by kkn50
The label is very worn. Can not read the name but can read "Model TDE7260A", "Transmit 450-470"
Making it a Motorola: http://www.ameradio.com/product/701/description.html
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Old 07-01-2007, 09:29 PM
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Yep, but I bet the farm that DB Products made it and let Motorola label it. That is identical to the DB404s I have here.
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Old 07-01-2007, 09:45 PM
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Quote:
Originally Posted by kkn50
I salvaged this antenna from the top of a building that we bought:

Is it possible to re-tune for use on the 70cm ham band?

Would it make a good antenna for monitoring UHF with a scanner?

Thanks.
Like someone already set, see what the match is in the middle of the transmit portion of 440. It's liable to match just fine. I have used an antenna (fiberglass 3 dB Maxrad) labeled for 450-460, down on the ham band with good VSWR.
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