[mythtv-users] Antenna attenuator question

backuppc at sundquist.imapmail.org backuppc at sundquist.imapmail.org
Mon Jul 14 22:06:19 UTC 2008


On Tue, 01 Jul 2008 17:42:53 -0400, backuppc at sundquist.imapmail.org
said:

> On Tue, 01 Jul 2008 8:27 AM, "Alen Edwards"
> <allen.edwards at oldpaloalto.com> said:
> 
> > Radio Shack sells them 5 for $1. They have 330 ohms. You can take a 
> > 330 ohm and a 3300 ohm and put them in parallel and get 300 ohms. But 
> > the 330 may be just what you need. You may also try using a paper clip 
> > into the 75 ohm center pin and squeeze it with your fingers also 
> > touching the case. The tighter you squeeze, the more loss you will 
> > introduce. 
> 
> Oh, OK, just a regular resistor.  I was thinking something built to
> screw onto the F-connector.
> 
> I'm an engineer, but of the chemical variety.  I remember taking the GRE
> exam and just skipped every EE question on the test and finished right
> on time. I knew that stuff would come back to haunt me sometime  ;-) 
> I'll see if I can try this hack out, though.
> 
> It might be a couple of days, though.  My Mythbox is plugged into the
> biggest screen in the house and the family wants to watch the Olympic
> swim trials, which are only available via streaming web, and only on
> windows, Arrgh!  So they booted the mythbox into windows for the whole
> week.  But the trials are back on broadcast this weekend; NBC of course,
> my problem channel.

All:

Just wanted to get back to all who helped with what I did.  I had to
wait until the above mentioned trials were over, and then got busy on
other stuff.

I never did get a resistor to check, because first I tried this:  The
4221 has a dead node at about 19 degrees off the direct back of the
antenna (http://www.hdtvprimer.com/ANTENNAS/cm4221.html).  The antenna
was previously pointing directly back at the problem NBC tower.  It was
happenstance that the NBC tower was directly in back, I was aiming at
the more distant towers 180 degrees in the opposite direction than NBC.

But because the front reception is not too narrow, I just rotated the
antenna about 19 degrees (hard to be too accurate), aiming the dead node
at NBC.  So far, this seems to work.  I get good NBC reception (tower
less than 5 miles away), with the amplifier on.  Still get good
reception from the Grand Island towers, 35 miles away, even though I'm
not pointed right at them.  I've been running this for several days now,
and my good luck doesn't seem to be just fleeting.

I suppose I should start a separate thread, but now my remaining
reception problem is the PBS tower where I get a strong signal strength,
but can't get a lock.

Last winter, when I was using an antenna in the attic (with marginal
results -
http://www.gossamer-threads.com/lists/mythtv/users/318560#318560 ), and
got PBS then.  Since that antenna was still mounted up in the attic, I
just plugged that into my capture card rather than my
roof-mounted/amplified 4221 and checked again.  Unlike last winter, when
I got these results (from above thread):

SCANNING: 647000000 (us-bcast:43) 
LOCK: 8vsb (ss=44 snq=43 seq=100) 
PROGRAM: 2: 43.1 WNED-HD 

Now it got no lock.  So I get no lock with either antenna.  So perhaps
WNED changed something?  But the signal strength is quite strong with my
roof-mount.  Would it help to rescan the channels?  Is there some
parameter other than the frequency that scanning picks up?  I don't
think so but the only dumb question is the one that isn't asked.

Thanks.

J.S.


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