RadioBanter - View Single Post - jury-rigging radio antenna for HDTV use?

December 26th 03, 05:58 AM

On 25 Dec 2003 19:22:50 -0800, (Jonathan
Epstein) wrote:

Hi Richard,

Thanks for your quick and extremely thorough and friendly response.
As
no doubt you can tell, I know nothing about antennas. Thanks also for
telling me what each antenna does.

In addition to the messages posted here, I also received a couple of
very helpful private emails.

The image of 1950's domestic engineering sounds like fun, but I think
that in this modern era I can make the necessary adjustments while
talking to my wife by cell phone :-)

Yeah, I thought of that too, but it didn't make nearly as amusing an
image.

I left out some detail in my original message, which I'll now attempt
to rectify. The existing antenna is above my living room, and the
associated TVs are on the far side of the house. In addition, I have
a
satellite dish which is pole-mounted in my yard (my neighborhood has a
lot
of mature trees, so there was no way to mount the dish on the roof),
and its junction point-of-entry into the house is directly on the
opposite side of the house, about 50' as a crow flies or 60' using
cables.

A satellite dish and cable have their own issues. It best to keep
these separate.

Portions of my house, especially the family room where the HDTV is
located, are pretty hard to wire internally, so I'd like to use this
existing
satellite dish connection and use combiners and splitters as
necessary.

The dish has its own tuner, so combining would seem unlikely. Also,
the frequency of the dish is considerably higher and more prone to
degradation if you begin combining and splitting along the way.

I think that even if I wind up using the rotatable FM antenna, making
an occasional trip to the living room stereo cabinet to rotate the
antenna is an acceptable level of inconvenience.

Given your TV signals are UHF, the rotating FM antenna is way out of
band. It may still work, but don't count on it. Trying will resolve
this of course.

If necessary I could adopt your suggestion and draw the antenna lines
out of the wall from the exterior. However (in my ignorance) I would
prefer to start fresh and connect "virgin" cables and connectors to
the
antenna, if that's practical.

Practicality is strictly a matter of what you want to do, and how
much. Sure, you can replace the entire run, you just need more of the
same thing. There is no downside to it, except it has you on the roof
more, but you may be there more often than anticipated anyway.

Also, as another poster mentioned, the
HDTV signals are all UHF, and I don't know what (if anything) I need
to
do to provide the appropriately undegraded signal, in a manner which
will 'mix' and 'unmix' well with the dish signal.

Keep things simple, run separate cables.

Hmm... another option: I have to check this out by going back on the
roof, but I suspect that the lower antenna has a cable, but isn't
actually connected to anything, so perhaps I could draw it outside
without
messing up my FM radio reception. In that case it might just be a
matter
of connecting to an RG6 cable. I could be wrong, but I don't think
that
the existing cable attached to the antenna is coax ... perhaps it's
twinlead. But in any case I now have a general sense of what baluns I
might need to buy, and what I need to look for now to interpret the
existing hardware.

Well if it is twin lead, it certainly is a throw-back to the 50's.
You might end up putting the TV antenna on the rotator and retiring
the FM antenna. The TV antenna is already more suitable to UHF.

Another remaining concern is how much power I will lose with a 60'
cable run ... it seems that it will be approx. 4 dB which corresponds
to roughly a 60% loss of power, if my math and understanding are
correct. This doesn't even include the existing cable runs from the
satellite dish junction to the TVs. I don't have a good sense as to
whether this is too much power to give up ... perhaps the use of a
pre-amp is justified. I'm also not sure whether I need to provide
power to the pre-amp, and how I might do that. I guess that I can
install a pre-amp sort of "en route" to the far side of the house, in
a location where electrical power is more readily available. A
battery powered pre-amp is also not out of the question, especially if
I don't need to climb onto the roof to change the batteries.

For receivers (we usually talk about transmitters here), a 4 dB loss
is trivial except in fringe areas. 60% may seem like a lot, but in
the scale of things TV tuners are quite capable with working with very
little signal. Again, simply trying will answer most of this.

Pre-amps that are put on the antenna work best. They can be powered
through the same line that carries the signal so no need for
batteries.

My next step is to visit the roof again in daylight and see what I can
figure out based upon the information that I've received here and in
the private emails. I plan to post back after I've explored this.

Thanks again to you or anyone else for continued advice.

Jonathan

73's
Richard Clark, KB7QHC