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Old 14-Dec-2016, 7:50 PM   #1
lifespeed
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antenna and low noise amp recommend for San Jose

Time to de-lurk and install some antenna hardware, here is my TVfool report. I would like to do without a rotor, and start with a single antenna pointed at Mt. Sutro and San Bruno in San Francisco at 314 degrees, although I am also hoping to get the 357 degree stations in Fremont if possible. I am not interested in the stations to the south. I'll be doing TV over ethernet using a Silicondust HDHR connect tuner(s).

I've been trying to decide between the DB8e and CM-4228HD antenna (don't need VHF, KGO 7 is repeated on UHF 48), as well as figure out if I would benefit from a LNA. I'm not entirely sure what's inside the HDHR tuner, but it may have a power splitter before any amplification, in which case an amp may be justified based on that alone. But like I said, I don't know much about the RF design of this tuner.

The antenna will be chimney-mounted on a 10' mast, which will put it 2 - 3 feet above the peak of a single story roof. Because of the networked tuner location in the attic, the run of RG6 will be less than 20'. I don't have trees nearby at 314 or 357 degrees.

In a nutshell, DB8e vs CM-4228HD antenna, and can I use a 18 dB gain pre-amp like the AD Juice without compressing and distorting the signal. Local tribal knowledge says the pre-amp is iffy.

Thanks in advance,

Lifespeed

Edit: Here is a teardown of the HDHR3 tuner. It looks like there is a pre-amp before the split to the dual tuner chips. With a short run of RG6 there may be little reason to use a pre-amp. Too bad they don't make that tuner in an outdoor enclosure version with Power Over Ethernet, could mount it on the mast and run ethernet up the pole.

Last edited by lifespeed; 14-Dec-2016 at 8:03 PM.
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Old 14-Dec-2016, 8:58 PM   #2
ADTech
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DB4e would be a better, more appropriate, and less expensive choice.

Now that both KNTV's flagship NBC programming is on KSTS and KGO has their UHF 35 translator, it's no longer necessary for folks in San Jose and points southwards down the valley to fight the VHF battle.

You probably don't need a preamp, but, if you do, the Juice will not overload internally. It might cause overload in your tuner, but IT won't overload.
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Old 14-Dec-2016, 9:41 PM   #3
lifespeed
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Quote:
Originally Posted by ADTech View Post
DB4e would be a better, more appropriate, and less expensive choice.

Now that both KNTV's flagship NBC programming is on KSTS and KGO has their UHF 35 translator, it's no longer necessary for folks in San Jose and points southwards down the valley to fight the VHF battle.

You probably don't need a preamp, but, if you do, the Juice will not overload internally. It might cause overload in your tuner, but IT won't overload.
Do you think the dB4E is enough for RF channels 42 (356 deg) and 45 (315 deg) at -80 dBm with the antenna pointed at 335 degrees? I guess the 60 degree beam angle of the less-directional dB4e might actually be better as you say.

The benefit, if any, of the pre-amp may depend on the noise figure of the Juice compared to the NF of the HDHR3 low noise amp plus 20' of RG6. The tuner overload can be avoided with an attenuator at it's input, presuming the noise margin of the signals is significantly improved with a pre-amp.

Thanks,

Lifespeed

Edit: I guess if there was an indication I needed a pre-amp, or wasn't able to get all the signals, the correct thing to do is a higher gain antenna before adding a pre-amp. But then directivity of the higher gain and my 40 degree separation between antenna farms comes into play. Try it and see . . .

Or I could get a dB8e, aim the panels separately, and cable the individual panels (two dB4e?) to separate tuners so as to avoid phasing interference issues from combining the RF. A moderately more expensive solution, but at $90/tuner not entirely unreasonable.

Last edited by lifespeed; 14-Dec-2016 at 9:48 PM.
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Old 14-Dec-2016, 10:21 PM   #4
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Hmm... Glad you raised questions.

Looking closer at the map, it appears you're in a very unique position behind the only hill in south San Jose. Your signal analysis indicates that you have LOS to both Mt San Bruno and Mt Allison in Fremont but your signal path to Mt Sutro, only 4 to the east of San Bruno, shows a very impaired signal path. Moving your marker only a few blocks to the west makes everything on your TVFool plot go "green".

Now, the first thing I'd suggest is to double check your location on the interactive map and verify if it's correct or not. I have so many errors using Google's Maps that I've simply adopted the policy of ALWAYS verifying locations with the map and NEVER accepting Google's geocoding. That has kept me out of trouble with faulty location lookups since I made that decision a while back.
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Last edited by ADTech; 14-Dec-2016 at 10:26 PM.
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Old 14-Dec-2016, 10:28 PM   #5
WIRELESS ENGINEER
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I like the DB4e because you need a wide pattern for max channel count In that direction

With nearly 60 degree beamwidth, its a set it and forget it antenna

The channel master and db8 would be too narrow and you don't look like you need the extra gain

Last edited by WIRELESS ENGINEER; 14-Dec-2016 at 10:34 PM.
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Old 14-Dec-2016, 10:41 PM   #6
lifespeed
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Quote:
Originally Posted by ADTech View Post
Hmm... Glad you raised questions.

Looking closer at the map, it appears you're in a very unique position behind the only hill in south San Jose. Your signal analysis indicates that you have LOS to both Mt San Bruno and Mt Allison in Fremont but your signal path to Mt Sutro, only 4 to the east of San Bruno, shows a very impaired signal path. Moving your marker only a few blocks to the west makes everything on your TVFool plot go "green".
I am a half mile south of Communications Hill, a few blocks west would do exactly as you described.
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Old 15-Dec-2016, 6:50 AM   #7
lifespeed
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Thought about this some more and did the noise margin calculations for the worst-case 10dB stations. A big assumption in these calculations is 7dB noise figure for the Silicondust HDHR3 tuner, I can't find any specs for it.

Using a dB4e without pre-amp and 20' of RG6 I'll get maybe a 1-2 dB improvement over the in-air noise margin. I've got 12 Mt. Sutro stations between 10 and 16 dB noise margin. A pre-amp will improve this by 5dB, a dB8e antenna will improve it by 6dB (with the potential cost of degrading the Fremont stations due to narrow beam).

I think the logical progression to try is:

1) dB4e aimed at 316 degrees, no pre-amp. Not much noise margin on paper, but it is simple and may work. Check and make sure I can get KGO-TV 35 at 357 degrees, one of the weakest Fremont stations at 22dB NM.

2) dB4e aimed at 316 degrees, 3dB noise figure Juice pre-amp (may need an attenuator at the tuner input). Should get me another 5 dB noise margin and allow me to rotate from 316 degrees nearer to 357 degrees Fremont if necessary.

3) dB8e, experiments with side-lobe pickup at 357 degrees, or dual antennas with separate tuners (relatively practical with $90 network attached tuners, no RF combining).
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Old 15-Dec-2016, 10:09 PM   #8
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Seems like a plausible plan. Please let us know how it turns out.
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Old 1-Jan-2017, 3:33 AM   #9
lifespeed
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Looks like the DB4E was the way to go

I mounted the DB4E antenna to the chimney today on a 10' mast, 15' of high quality RG6, no preamp, Silicondust HDHR4 network tuner. It is a couple feet above the peak of the roof, about 24' above ground level. According to the TVfool report, the three stations I'll have the most difficulty pulling in are:

Station: direction/location/strength/SNR/symbol quality/distance
KBCW 45 (44.1) 316 deg Mt. Sutro 95/85/100/47 miles
KFTL-CD 28 (28.1) 312 deg Mt. San Bruno 72/64/100/16 miles
KAXT-CD 42 (1.1) 356 deg Mt. Allison 98/90/100/43 miles

I aimed the antenna trying to split the difference using channels 45 and 42, probably should re-aim a few degrees to the west using 28 and 42 to see if I can't improve 28.

Thanks for the advice. I'm glad I got the smaller, broader-beam antenna.

Edit: added some installation photos, click to zoom. Notice the 10G solid ground to a copper rod in the dirt off camera. The green stranded 12G goes from the ground spike to a coax ground block before entering the attic to tie into the ground bus back to the electrical panel ground. There are only 6' of RG6 from the attic entry point under the eaves, the HDHR4-US network tuner sends the streams over the network to a media server PC that DVRs and transcodes to mobile and other clients anywhere on the internet.






Last edited by lifespeed; 21-Jan-2017 at 11:54 PM. Reason: add photos
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Old 21-Jan-2017, 11:34 PM   #10
lifespeed
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bump for added photos

See install above, @GroundUrMast would be satisfied.
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Old 22-Jan-2017, 4:35 AM   #11
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If you"re happy, I'm happy.

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If the well is dry and you don't see rain on the horizon, you'll need to dig the hole deeper. (If the antenna can't get the job done, an amp won't fix it.)

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Old 22-Jan-2017, 11:53 AM   #12
ADTech
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Please install the zip ties that were included with your DB4e as shown in the directions. I had them added to the bill of materials (and the instructions) for a very good reason (to prevent damage).

Glad it's working!
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