CBS-DT Antennas

[JimHall]

To those of you having a tough time or are unable to pull in CBS DTV signal, try this.

If you have a pre-amp pull it out.  If you have no pre-amp and you are straight off an antenna, try padding down the signal or try an experiment just using an indoor antenna or rabbit ears.

It seems that those of you with really strong signals from TMJ & PBS have a tough time with our signal.  We think, there may be some internal mixing of OTA signals within the tuners causing an overload on our channel assignment.  The correct way to help fix this problem is to use a VHF/UHF combiner backwards and thus separating the VHF from UHF, pad down either the  VHF or UHF side and then re-combining the signal back together and then to the tuner.  But at this time we are not sure which band is causing the problems, we suspect it's the VHF side, however.

I know this may sound strange, but we had a success story with this approach.  

If you are not versed in the combiners, just simply try less signal overall to the tuner as mentioned above; pad down or use a low gain antenna.  I think most of you know that more signal or higher readings on the sets will not result in a better picture once the threshold level for a locked signal with low bit-error rates is achieved.

If any one has success, please let us know.

Thanks
Jim Hall




[This message has been edited by JimHall (edited 03-15-2002).]

[rnelson]

Desperation is sinking in.  There isn't much else that I can grasp onto but acknowledge the fact that the RS Antenna in the roof of my garage just isn't enough to pull me through the reception areas that I would like to get.

I expected to get CBS-DT with no problem.  I wanted ( in the long term ) to try to pick up Chicago.  I used to live in Kenosha and got very used receiving Chicago Channels just as easily as Milwaukee.

Anyway, I spent the last two days assembling a variety of equipment that will put a more conventional antenna on my roof.  I didn't want to do that.  Only because my dad was a Ham Radio Operator (WB9QMX) and his roof looked like a scrap metal junk yard.  For those of you who struggle with your wives over our "Hobby???", my mother struggled with my dad over his Radio (30+ Years).  The old saying goes, "If you can't beat them, join them."  Anyway, my mother studied and took her Ham Test.  She passed and received the call sign KA9AAH.  They both died in July 1984 in a Car accident.  But I'll never forget the junk my dad had on his roof.  Dipole antenna from the roof to a pear tree in the back yard.  2 meter antennas, 6 meter, TV etc.... You never seen so much junk on one roof in your life.

Anyway, I have my nephew coming over today.  I have a 10' tripod with conventional Channel Master equipment.  Total cost is about $400.  Let's hope for the best.

Roy Nelson

[tenth_t2]

Let us know what CM antenna you have, and how it works!

Greg O.

[MesaV]

Stations:          PBS -   CBS -    NBC

Straight thru:      91 -    32 -   N/B
Combiner/Splitter:   91 -     8 -   N/B
VHF Connected Only:   91 -     0 -   N/B
UHF Connected Only:   0 -    10 -   N/B
-6dB VHF side:          85 -     16 -   N/B
-12dB VHF side:         70 -     16 -   N/B
-6dB UHF side:          91 -      0 -   N/B

First off I hope the formatting holds.
NBC was Not Broadcasting during my test.
NBC is always at 100.
My antenna is a CM 4228 in the garage attic.
The 1st test is a straight through signal from the antenna to my Sony SAT-HD100.
The 2nd test is a pair of Radio Shack Combiner/Splitters Part #15-1237.  I split the signal into UHF and VHF, ran coax on each signal to the second Combiner/Splitter.
The 3rd test I disconnected the UHF side, leaving only the VHF side connected.
The 4th test I disconnected the VHF side, leaving only the UHF side connected.
The 5th test both sides are connected but the VHF side is attenuated by 6dB.
The 6th test both sides are connected but the VHF side is attenuated by 12db.
The 7th test both sides are connected but the UHF side is attenuated by 6dB.

Ok Jim??  I'm not a rocket scientist but I play one at home on occasion.  To the untrained eye it appears that I'm getting most of your signal on the VHF side.

Ray

[This message has been edited by MesaV (edited 03-16-2002).]

So much for the formatting!

[This message has been edited by MesaV (edited 03-16-2002).]

[JimHall]

 Ray;

You play a pretty good rock scientist at home.

Looks like you understood exactly what I was discussing.

Since it appears that you are receiving a signal from us, but a low number, I am expecting that you are experiencing a multi-path problem that is causing high bit error rates.

Currently, when I set my simply rabbit ears to receive our station at an 80, I lose TMJ to about 45 and PBS is at 70.  When I set it to get TMJ at 90-92, our station drops to 58-60.

In the old analog days multi-path showed up as ghosting, but know it can wipe a digital signal out completely.

On our analog signal we actually trasmitt a ghost cancelling signal that higher end sets have and cable headends use.  But in the digital era I am not aware that our industry has come up with a bit error rate multipath solution.

I think the next thing to try is moving the antenna.  Antenna is attics are prone to ghosting or multipath.

Let me know what else you try.

Jim Hall CBS-58


[This message has been edited by JimHall (edited 03-16-2002).]

[MesaV]

I didn't want to do it, but the CM4228 is on the roof now. Hello CBS, 84 on your friendly signal meter.
Jim, when you guys do ramp-up to full power the antenna is coming back indoors.

Ray

[Tom Snyder]

I followed your instructions, put my rabbit ears close to parallel to the floor (up about 7 feet from the floor) and turned off the amp, and the signal has been solid ever since.

BTW... it's an RCA DTC-100 STB

[This message has been edited by Tom Snyder (edited 03-16-2002).]

[rnelson]

Ok Guys, Heres the preliminary Results:

Station   Call Letters  Location   Signal Lvl
=============================================
26-1      WKOW-DT       Madison    59
44-1      WSNS-DT       Chicago    40
 2-1      WBBN-DT       Chicago    46
 7-1      WLS-DT        Chicago    32
32-1      WFLD-DT       Chicago    54
 1-1      CBS58HD       Milwaukee  91
 4-1      WTMJ-DT       Milwaukee  94
10-1      WMVS          Milwaukee  88

Not Bad for a start.

Roy

[Joseph S]

My splitter results

No Splitter: NBC:87, CBS:65-71(unstable), PBS:79
VHF(HI): NBC:5, CBS:0, PBS:80
VHF(Lo): NBC:0, CBS:0, PBS:25
UHF: NBC: 88, CBS: 65-70, PBS: 0

So NBC and CBS are for the most part entirely UHF, PBS is entirely VHF with the majority of the signal in the VHF(HI).

The sad thing is even at a signal strength of 25, there is almost no difference between this and the normal 79 PBS strength. CBS's simulcast looks like crap at my end even when hovering at 67-70 signal strength. The HD broadcasts are fine with the exception of the breakups every 5 minutes.

[This message has been edited by Joseph S (edited 03-16-2002).]

[JimHall]

 

Originally posted by MesaV:
I didn't want to do it, but the CM4228 is on the roof now. Hello CBS, 84 on your friendly signal meter.
Jim, when you guys do ramp-up to full power the antenna is coming back indoors.

Ray

Ray,  My guess is that you cleared up the multi-path on our station and the bit-error rate that keep the signal from locking up on the set.  Glad you are able to watch us now.

But even when we ramp up the power, it may or may not solve your problem.  If it is multipath, it will still be there (multipath) and in the same ratio causing the same exact problem.  
Jim Hall


[This message has been edited by JimHall (edited 03-16-2002).]

[MesaV]

For now, I'm going to leave well enough alone.  Thank you for your help Jim.  Okay, now what programming is really in HighDef.

Ray