Re: [HDTV-in-SFbay] Antenna Choice and Location for Mid Peninsula
- I am in Palo Alto and offer some observations. I have an 8' piece of
rigid conduit mounted on a router that is not used other than as a
mount. A chimney mount would be much more secure. It has been there
for over 20 years with 4 antennas on it. Two are very large VHF/UHF
antennas, one is a UHF and one a omni FM.
The UHF antenna is pointed south east but I don't use it as 9.2 is a
re-broadcast of the only station I want over there.
The second VHF/UHF antenna is left over from when channel 12 was in
San Jose. I don't use that either.
While I have a rotor, I don't use it either. It is a pain. Think of
channel surfing with a rotor. Get a second antenna. A rotor is good
for ham radio when you might want to transmit in any random direction.
In your case, you just want two fixed locations so get two antennas.
Trees matter so avoid them if you can. They matter more in the rain.
If you have to look through a tree, it should still work.
If you have trouble, get a preamp.
On Sun, Nov 23, 2008 at 5:26 PM, baumgrenze <baumgrenze@...> wrote:
> I'm the new kid on the block. Here are my current questions.
> I am in Palo Alto. A search on www.batchgeocode.com puts me at
> Latitude: 37.442104 / Longitude: -122.129052.
> I am currently reworking my antenna system for OTA reception on a Sony
> Model #: KDL-32XBR6.
> The current state of affairs is as follows.
> I removed the VHF antenna from the top of my 1.25" x 9.5' tubular
> mast. I moved my Archer Model U-75R directional UHF antenna, purchased
> in 1989, to the top of the mast. I attached a 300 ohm to 75 ohm balun
> and 50' of RG6U cable and connected it to the TV and ran the setup.
> The mast is currently leaning against a ladder, guyed to 4 points with
> parachute cord. The antenna is roughly pointed at Mt. Sutro. The
> reception on KQED 9.1 is great. I should be so lucky once I have set
> and guyed the mast properly. I recognize that to pull in signals from
> Mission Peak and Mt. Hamilton I must reorient this antenna towards the
> transmitter towers.
> I am considering replacing the U-75R with a Terrestrial DB-4
> non-directional antenna. Can I expect to receive good signals from
> broadcast antennae that are 114.5° (Mission Peak) and 151.26° (Mt.
> Hamilton) relative to a line-of-sight bearing on Mt. Sutro? Do I need
> to worry about signals being reflected from the local mountain ranges?
> Do I need to worry about Palo Alto's many trees? I have some very tall
> ones near my house.
> In my rework, I removed about 6' of 1.5" tubular mast from between the
> swivel base mount and a 1960's rotor. I discovered that it came with
> only 8 ball bearings running in an upper race and another 8 in a lower
> race. Needless to say, the aluminum bearing race is severely by years
> of wind rocking of the antenna system. I think I could get it to run
> again, but it hardly seems worth the effort.
> The mast still carries a large FM antenna, too. It is ~148" long and
> ~138" wide on its rear-most, longest element. I would like to get this
> a bit more than 6' from my flat Eichler roof for safety reasons. I can
> see two possible solutions:
> 1) Purchase 6' of schedule 40 or heavier galvanized iron pipe threaded
> on one end. Install a pipe flange on the upper end and use this as a
> lower extension, running guy wires from holes drilled in the flange.
> The mounting end would be in a Universal Swivel Base Mount (9013)
> mounted on a 4" x 7.5" x 0.25" thick steel plate lag screwed to the
> fascia board of the upper roof. This should give me room to put my FM
> antenna at 4' below even a DB-4 mounted on the top of the mast. It
> would allow a slip fit of 18" between the pipe and the tubular mast.
> If the pipe does not fit the swivel base, I could bore hole through it
> an appropriate distance from the bottom to fit the swivel bolt.
> 2) To keep both antennae lower, I could purchase a chimney mount kit
> and mount an 8' long mast on it. The chimney in question extends up
> ~4.5' above the lower roof (~18" lower,) so roughly half of the mast
> would be between the upper and lower mounting brackets. Wouldn't this
> make for a pretty secure mount without guy wires? I would use this to
> mount the FM antenna. Should I be concerned that the forward-most
> element of the FM antenna would be ~18" from the mast carrying the UHF
> antenna? It would be `behind' the UHF with respect to Mt. Sutro, off
> to the side with respect to Mission Peak, and in front with respect to
> Mt. Hamilton. Would this make a difference?
> 3) The entire tar-and-gravel roof has urethane foam sheet insulation
> with an aluminum foil facing. Is this significant?
The broadcast antennas are physically vertical looking but they transmit in the horizontal plane. All television stations are licensed to operate at their power in the horizontal plane if there is a vertical element that doesn’t count in operational power. KNTV will replace the old top mount ch-11 antenna with a new ch-12 top mount antenna sometime in 2009 I believe (we will then have a main and standby antenna capable of 100% power operation) and when completed we will have the ability to have a 100% power in the vertical plane as well as the horizontal plane. It is planned to operate that way as there are many indoor antenna users in the bay area (especially in SF) and to this point no one builds a good indoor VHF antenna. By the way we currently operate at 25% vertical.
From: HDTV-in-SFbay@yahoogroups.com [mailto: HDTV-in-SFbay@yahoogroups.com ] On Behalf Of Frank Nemec W6NJR
Sent: Friday, December 12, 2008 8:34 AM
Subject: [HDTV-in-SFbay] Re: Sugnal Report
The screen is indeed aluminum. The product catalog says so, and nearly
all residential TV antennas use aluminum elements for high conductivity
and low cost and weight. But they're not so good for strength, so I
would always lose about 3 long elements per season to the wind.
Sometimes they anodize the aluminum, I think mainly because the gold
finish looked better and sold better.
The new model, the 4228HD, has close-spaced horizontal elements running
the full width of the antenna. That makes it an almost perfect
reflector for the horizontally- polarized component of the signal, nearly
as good as a solid aluminum panel would be. The horizontal gap is
mostly just a slightly wider gap than all the others. The 'driven'
elements (the ones connected to the feedline) are also most sensitive to
the horizontally- polarized component of the signal. That's why the
horizontal gap wouldn't make much difference.
That led me to wonder. Since all the TV antennas on Sutro are vertical,
why don't we install these antennas vertically? I suspect the reason is
that the vertical stacking makes the sensitivity pattern flat, like a
horizontal pancake. You sacrifice the polarization match because for an
antenna pointed north, extra sensitivity to the northeast and northwest
is more useful than sensitivity toward the dirt and toward the north star.
PS: Sorry for the confusion I caused regarding Nick Sayer's antenna
setup. I was reading the compass bearing from him to the various
stations, but I was mistakenly reading that from the distance column
instead of the heading column.