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Dave Loudin 21-Sep-2010 8:18 PM

One from another forum
 
This is a challenging problem. The person has an east-facing balcony, so his building will block anything from the west. The locals are the VHFs to the southwest and the two closest UHFs to the northeast. ABC can be found as SD 12.2.

I'd like to recommend the CS5 for his VHFs, but I don't know what its sensitivity is for RF 5. I've told him to try rabbit ears laid flat for VHF paired with a DB-2 via UVSJ to begin with. What do you think?

John Candle 21-Sep-2010 8:56 PM

Tv Reception
 
Is this Condos that the person owns or apts ?

Dave Loudin 22-Sep-2010 1:21 AM

Townhouse.

John Candle 22-Sep-2010 4:30 AM

Tv Reception
 
So most people own town homes. So the antenna can go on the roof. You know about the federal law that states that home owners can install antennas on the roof. And Yes the law covers town homes.

Dave Loudin 22-Sep-2010 4:31 PM

I know that. This is a rental - no roof access. The balcony is the only outside space available.

mtownsend 22-Sep-2010 5:31 PM

I wouldn't expect much on channel 5 from a C5 antenna. I'm guessing that the low-VHF gain is quite low like most other channel 7-13 antennas.



For both low and high VHF coverage, you can use an antenna like the Winegard HD-5030 (large) or Antennacraft CS600 (small).

It's also possible to combine a low-VHF and high-VHF antenna through a HLSJ, and then combine a UHF antenna through a UVSJ. I don't see any particular advantage to having separate hi/lo VHF antennas, but special circumstance might warrant such an approach.

It's always a big gamble trying to pick up channels *through* a building. To get to the channels on the other side of the building, I would strongly urge getting the antenna on the roof or on the other side of the building.

If the user insists on picking up the stations *through* the building, then there's no way of knowing how much signal the building will block/reflect/absorb. They may end up needing a larger, higher gain antenna, or it may end up not working at all. My gut feeling is that rabbit ears probably won't be good enough to pick up channels 10 and 12 reliably through the building unless they happen to get a lucky bounce off a nearby building or their own building is unusually "transparent" at VHF frequencies.

To put a few numbers to these ideas... Rabbit ears in an ideal dipole configuration will get close to 0 dBd gain. In reality, people are more likely to see closer to around -2 dBd gain. The small VHF Yagis will typically see between +2 and +5 dBd gain. The large VHF Yagis may get as much as +5 to +9 dBd gain. The losses caused by the building can be all over the place, but in most cases, it is roughly in the range of about 5 to 30 dB of loss.



I think my initial recommendation would be to get the antenna on the roof or hang two antennas on opposite side of the building. If the user can give each antenna a clear view toward each of the main transmitter clusters, then I would point a CS600 to the south-west, and a DB2 or DB4 (for added gain yet still a wide beam width) aimed north-north-east, half way between channels 51 and 23. Combine the antennas through a UVSJ or a dual-input pre-amp.

ADTech 22-Sep-2010 5:57 PM

Quote:

I'd like to recommend the CS5 for his VHFs, but I don't know what its sensitivity is for RF 5.
I don't know either, so I sent an email to the design engineer to see if he ever modeled it on low-VHF or FM. I'll pass on anything I find out.

FWIW, I use a scrapped C5 loop hanging on the wall of my garage for an FM antenna. It works well enough, but I haven't formally compared it to a reference antenna of known characteristics using test equipment other than my old Pioneer SX-750 that I've had for more than 30 years.

I'm not very optimistic about the prospects of the location in question given the stated constraints.

ADTech 22-Sep-2010 7:39 PM

Got a response back already.

After the standard (and expected) disclaimer of "I didn't design it for low-VHF or FM..", he emailed me polar plots of the simulations he ran on low-VHF.

As expected, it's pretty low: Computed gain ranges from -22 dBi at 54 MHz to -11 dBi at 88 MHz. He did caution that he never actually tested the antenna on this band so he cautioned that actual results are likely a bit different.

All-in-all, it's pretty unlikely that the C5 would be successful for that part of the suggestion.

ADT

Dave Loudin 22-Sep-2010 7:59 PM

ADTech, thanks for checking into that (I was hoping you could!) I'll pass along the recommendations. I directed the person to rabbit-ears knowing all the issues, especially for 10 and 12, because if he couldn't get 5, then bigger VHF antennas would not be worth the cost and time.

The person is in Morgnatown, WV. I used to live there and in several other towns in the Mountain State. This case is pretty typical for many - the rolling hills really break up reception for many. Even when you're near the top of a hill, the shadows of other ridges still frustrate OTA reception. 'Tis no surprise that CATV was born in this area.

John Candle 23-Sep-2010 4:29 PM

Tv Reception
 
The vent pipe mount on the roof


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