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Old 06-08-2013, 10:27 AM   #15  
Pete Higgins
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Join Date: Aug 2012
Location: California, 58 miles @112 degrees from Mt. Wilson
Posts: 242
Default HDB8X multi-directional?

A compelling advertised feature of the HDB8X is its ability to align the 4-Bay panels to receive broadcasts originating from different directions. Since I predominately watch UHF stations coming from San Diego @ ~169 deg. (True) and Los Angeles @~292 deg. (292 – 169 = 123 deg.) I thought I would see how well it performed when configured with the panels orientated at a 123 deg. angle.

Similar to what I did yesterday, using the rotor, I “bump” aligned the CM-4228 for maximum SNR on San Diego channel 30 (15.1 KPBS) and then, by eyeball, “fix” aligned the non-movable HDB8X panel to match. I then “bump” aligned the CM-4228 for maximum SNR on LA channel 36 (4.1 KNBC) and then, by eyeball, “fix” aligned the movable HDB8X panel to match.
FYI, I had to tighten the wing nuts on the mast clamps until they were vertical to align the movable panel. To go more than ~130 deg. you’ll probably have to shorten the mast clamp bolts on the moveable panel side.
While I got my normal 3 San Diego UHF stations, I thought I had a bad panel pointing towards LA. Other than my local channel 26 (24.1 PBS TVFool @ -15.6) I couldn’t receive any LA stations. After several trips to the roof to check connections & alignment I decided to disconnect the LA panel from the combiner and use it like a standalone 4-Bay. I connected the combiner end of the HDB8X harness through an F-81 F-F barrel to the black coax used for testing yesterday. Configured standalone, I got channel 38 (30.1 ION) with an SNR in the 15.x range. Usually anything below 16.x isn’t watchable for very long. Clearly to be useable I was going to have to add an amplifier.

I connected the combiner end of the HDB8X harness through an F-81 F-F barrel to a 15’ section of RG-6 coax. I connected this new length of coax through a Channel Plus NF-471 55dB channel 24-29 notch filter to my Winegard AP-2870 amplifier’s UHF input. Configured this way I got 13 of the 19 channels I had yesterday. As expected, I lost the San Diego channels and all but one (PBS) of those in the NF-471 notch.

Pleased with the amplified single panel results, I reconnected the HDB8X harness to its combiner input and connected the 15’ section of RG-6 coax to the combiner output.

Combining the two antennas resulted in the total loss of 9 LA stations and dramatically reduced the others. Based on today’s testing results, for my location, the HDB8X is a competitive 8-Bay Bow Tie when used in its “flat panel” configuration but is nearly useless for leveraging its advertised multi-direction feature.

I suppose one advantage it still has over a conventional 8-Bay like my CM-4228 would be the ability to use it as 2 separate 4-Bays and run separate cables to a coaxial switch?

I also ran a series of tests substituting a PCT MA2-M +15 dB cable drop amp for the Winegard AP-2870. The Channel Plus NF-471 notch filter was not used with the MA2-M.
Attached Images
File Type: jpg HDB8X Test 7 June 2013.jpg (120.9 KB, 32 views)

Last edited by Pete Higgins; 06-08-2013 at 11:03 AM.. Reason: Add attachment
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