Presumed FM interference
 

http://www.tvfool.com/?option=com_wr...5b9480256c9f67
Great forum!! Thanks to all that offer their expertise.
Current setup is a Winegard 7084p rooftop with 10' pole with 25 foot of RG6 into attic to a AP 8275 with FM trap on, done about 8 years ago. I have always had trouble with real channel 7 pixelating presumably from a strong FM station about a half mile away. Two years ago, I placed Radio Shack FM trap in line prior to preamp and the channel is watchable with minor pixilation. However, WEHT pixelates mildly since then presumably from the extra NM introduced by the FM trap. Surprisingly, channels 15 and 20 are rock solid but no channel 47. There is only 25 more feet of coax to one TV from the preamp. I have not tried adjusting the variable trap. I have tried the RCA preamp and a Kitz tech amp with no change in results. I have at my disposal a CM 4221HD and an HBU33.
Questions: Can I trim the VHF elements on the 7084 to the length of the VHF elements as on the HBU 33 and effectively make a 7698 out of it and reduce some of the FM interference that way? If so, what is the best way to trim an element?
Should I try either or both of the other two antennas with the Winegard or RCA preamp with FM traps and hopefully eliminate the Radio Shack component? Would I likely lose channels 15 and 20?
Appreciate all your input! Thanks!!

Sorry about a mistake. It should have read WFIE channel 45 pixilates mildly since adding the Radio Shack trap.

Post an FM Fool report. It may not be FM interference as you assume.

Re-run your TV Fool report at 30, 40 and 50 ft to see how far up you have to go to get RCH7 and RCH46 (your weakest stations) as a 1Edge or even LOS. I think a slightly taller mast will make a huge difference in your location.

Just completed install of CM 4221HD with Antennacraft Y10713 at 40 foot height using RCA pre-amp, fm trap on, separate input selected and 4 foot distance from each antenna. Was able to eliminate radioshack fm trap and real channel 7 now rock solid. Channels 15, 20, 47 all rock solid with substantially lesser noise margin than WFIE that still pixilates mildly but watchable and solid after dark. Will assume mulitipath? Adjustments to aiming could hurt the lesser NM channels. Would appreciate any suggestions!!!

+=>

In place of the CM4221HD install a CM4228HD.

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Can Call the WFIE Tv Station with a Telephone and Have a Voice Conversation With the Engineering Department About the Transmission and Reception Situations of WFIE and Your Reception Situation.

http://en.wikipedia.org/wiki/WFIE.

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A question.

Is , W06BD , Analog channel 6 being received??

http://en.wikipedia.org/wiki/W06BD.


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As always , for Reception of Tv Stations , trees and tree leaves , plants and plant leaves , have a Negative Effect on Broadcast Tv Reception and so do buildings and and other obstructions including you own building.

Some and not all Negative Effects are.

Absorbing and Blocking Reception.

Multi-Path Reflecting Tv Signals Bouncing All Around.

The Best Practice for Reliable Reception is to Install the Antenna/s at a Location that has the Least Amount to No Amount of Obstructions of Any Type or Kind in Directions of Reception Including Your Own Building.

I agree that your problem is likely to be FM interference. Unfortunately, the frequency of the strongest station is 89.1 MHz, and almost all FM traps pass 89.1 with little attenuation. This is because channel 6 is on 82-88 MHz, the trap should not interfere with channel 6 reception, and the trap can't be designed with rejection that close.

A better solution for you is to install a HLSJ between your antenna and the preamp, and put a 75 ohm termination on the L port of the splitter/joiner.

An HLSJ is an excellent suggestion.

The FM Filter we carry is a "full-band" filter and doesn't compromise FM suppression to save channel 6 (which it will also attenuate) so it can't be used in areas like Philly or Albany (Sorry, Fred!).

I have seen FM interference severe enough that two traps in series were needed to suppress really strong FM.

I have seen tests that show that the AD FM filter takes out only some channel 6, so it might still work in a strong channel 6 environment. I doubt that the FM attenuation of the AD filter would be sufficient in this case.

That is based on an FM fool look-up using the 4 digit latitude and longitude data in the TV fool report. It shows that 89.1 is .7 miles away and +4 dbm signal level.

Yep, that's a hot signal, alright.

I tested the Pico and Holland HLSJ devices a couple of years ago. The Holland attenuated 90 MHz by about 25 dB, the Pico was around 31-33 on a curve. Some of our FM filters tested close to 40 dB, but there was a variance all the way down to only 20 dB on some units.

I've got one of the current Radio Shack FM filters at the shop. I'll put it on our new office play toy (Agilent FieldFox N9923A) tomorrow and see what it looks like.

Thanks to all who have replied and shared their knowledge base. T he fm interference on real channel 7 was eliminated with the Y10713 and the RCA preamp fm trap. Channel 6 was never received on the Winegard 7084p and is a high school channel of no significance. Channel 46 has remained a pixilation problem and as Teleview suggests, I have an email into the engineer for possible troubleshooting. The Winegard advertises a gain of 12 to 14 db on channel 46 so upgrading to a Channelmaster 4228 would be a gamble.
If anyone has ideas for eliminating the channel 46 problem, I am all ears.
Many thanks!!

Try raising or lowering the antenna 6-12 inches. It may be sitting in a weak spot for WFIE & just needs a slight vertical tweak to see a more consistent signal.

About one year later, I have been struggling with real channel 7 (ABC channel 25 Virtual).
Signal strength is good on a new LG 24 inch with signal strength meter only. Channel strength drops to nothing for hours and then returns to good and watchable at random with no correlation on time or electrical intereference or fm intereference. All fm traps (most recent a Winegard FT 3000) have been tried and in multiple series with no effect.. NO amp is used and cable run at 50 feet.
Poor connections come to mind, however all coax replaced within one year with RG6 and best fittings. RF 9 always solid and not intermittent.
As an experiment today, mounted an RCA ant751 about 8 foot below the antennacraft Y10713 to a separate tv tuner and picture watchable with mild pixilation on rf 7 with no reception on the Antennacraft. Again rf 9 receivable on both antennas.
I realize that signal layering issues occur, but for an antenna that has a 9.4 db gain to go from good strength to absolutely nothing strength seemingly at will and maintain channel 9 reception without issue would not suggest a connection issue.
Please comment and offer your expertise. This gremlin is on my last nerve!!

Did you ever try raising or lowering the Y10-7-13. It may be sitting in a bad spot for RF 7.

How is signal strength on RF7 when it is good, compared to RF9. Is one more stable than the other at these times?

Do you happen to have one of the anaolog to digital converters leftover from the transition?

Your gremlin is FM second harmonic interference that harms 7 more than 9.
http://www.tvtechnology.com/digital-...ference/202503

CH 7, 174-180 MHz, 1/2 = 87-90, WVJC 89.1 +4.2 dBm
CH 9, 186-192 MHz, 1/2 = 93-96, WYNG 94.9 -9.2 dBm, 13.4 dB less

see Attachment

Possible solution: two HLSJ in series between antenna and preamp

Ant > HLSJ > HLSJ > AD Juice Preamp > coax down > Power Injector > TV
http://www.hollandelectronics.com/ca...-Diplexers.pdf

The Juice preamp doesn't have an FM filter, but it is highly resistant to overload.

Is it safe for me to assume that your coax shield is grounded with a grounding block to help reject interference?

It is also possible that the noise level on VHF from electrical interference is high at your location. I have a VHF-High channel that would seem to be strong enough, but the noise level is so high the SNR for that channel barely makes it to 15 dB as shown on the Diagnostics Screen of my Sony TV. Sometimes I can receive that channel, sometimes not according to how high the noise level is at that time. I have been able to measure the strength of that signal and the noise level of the vacant adjacent channel with my old Sadelco 719E signal level meter (SLM) to confirm that. I have also used my Sadelco DisplayMax 800 SLM to make similar measurements of SNR.

OTA signals are constantly changing in strength, especially for 1Edge and 2Edge signals that are less stable than LOS signals. This is why you need to have a fade margin of at least 10 dB for your NM after adding antenna and preamp gains.

Thanks, I was assuming the OP was still using the Radio Shack FM trap, but looks like he has removed it after re-reading the thread. He absolutely needs to have one. I would re-insert the RS trap & try that before ordering anything. It might be enough.

The RS trap probably has insufficient attenuation at 90 MHz to be effective in this situation.

Maybe / maybe not. I have successfully used one with a +8.3 db FM station .25 miles away (90.9) I would certainly try it first.

All FM filters are not equal.

http://forum.tvfool.com/attachment.p...1&d=1433181349


FM Filter
http://www.avsforum.com/forum/25-hdt...fm-filter.html

I know that, but the OP already has the RS unit. Why not try it first??????? Is this an informercial?

An infomercial, no. It's a setting of expectations when a given tool that is at hand is known to not be the best suited for the job.

If the OP wishes to give it a try, then he should do so since all he's spending is time and effort. It's his choice to see if it will help or not but, if it doesn't, there is no definite conclusion about it one way or the other.

He already tried it. Weren't you paying attention?

And if he tried it again, and it didn't work again, what would you suggest that he do next?
It couldn't possibly be an infomercial, because I said use a HLSJ instead of the AD or RS filter.

I have selected the best tools for the job without consideration of brand, which is what engineers do and marketing guys don't. I selected the Juice preamp, not because it is made by AD but has excellent proven resistance to overload from strong signals. Do you know of a better one?

No, just saying I have used a RS trap where all the charts & graphs indicated it likely wouldn't offer enough attenuation, but it worked like a charm. Sometimes things work in the real world that don't on paper.

Just like I have a 2005 Corolla that the EPA rates at 27 city/35 highway. I never have see a tank below 40 MPG, even regularly commuting in ugly DC traffic. Currently averaging about 45-46 MPG in the warmer weather.

Like everything else, YMMV.

Oops, I didn't see where he tried it again. My apologies:)

No problem. I have been known to miss a post and have been called down.

At least you are trying to help.

Sometimes a good idea comes from an unexpected direction, so I try not to reject it right away.

Great discussion.
To quote Bones on Star Trek, "For Godsakes Jim, I'm only a doctor not an engineer!!"
I have at my disposal a Winegard FT 3000 and a Radio Shack fm trap
that I have tried separately but not in tandem with no effect but a reduction in all channel signal strength.. I also have a winegard 8275 with trap and the RCA preamp with trap. Also have a AD CPA 19 and various and sundry Terk and RCA inline amps with no traps.
All amps produced worse signal strengths on all channels and with 50 feet of coax to the tv, so I just eliminated them.
Tried using the analog to digital convertors at both locations and still no signal on the Y10713 but signal on the RCA 751 so tuner sensitivity not the issue.
Will get a couple of HLSJ and give them a shot.
The question comes to mind if it is a second harmonic on RF7, why is the bigger antenna affected and not both? I believe these radio stations operate 24/7 and since I see no pattern to the reception issue, the changing of transmitting KW( if that is the case) seems to have no effect on the reception pattern. I am remiss in not having a grounded system. This setup is at my 87 y.o. Mother's house and while OTA has become a novice hobby of mine(obsession?), I will correct that also.
As always, the level of expertise found here is extraordinary and I can't praise everyone enough.

Thank you for the background information and the kind words.

Please let us know the results on this same thread.

That is done for AM transmitters in the broadcast band, because the signals go farther at night.

Are any of the boxes Zeniths?

Could be FM, or just the difference in where the antennas are mounted. Once you try the HLSJ(s) we will know better as they will eliminate any FM concerns.

I'd check the balun next.

The FM interference was stronger from the Y10713 because it has more VHF gain than the 751.

Update--installed 2 hlsj's in series and low and behold signal strength returned to normal range on the LG but no picture. With tweaking of the aim of the Y7 10 13 and a presumed signal quality improvement, picture returned with rare pixilation from mild wind and trees. Was able to reconnect the RCA preamp with increase in all channel signal strength.
While all posts celebrate the RCA preamps resistance to overload, I believe this fm signal hit its Achilles heel.
Now as editorial comment, for the extra $1.98 that an hlsj costs, why not incorporate them in manufacturers harness / balun/ connectors that a hi VHF antenna is shipped or manufactured with to increase customer satisfaction and success rate.
If we didn't follow this type of philosophy in medicine, the cemeteries would be much larger.
Again, greatly appreciate everyone's expertise.

Thanks for the update with the good news. It's good to hear when we get a tough one right.

Tweaking aim while monitoring signal quality (SNR and errors) is the best way to do it. The technique works best and is most sensitive when the signal is weak and close to the "Digital Cliff."

http://forum.tvfool.com/attachment.p...1&d=1433989061

Aiming an Antenna for Best Signal Quality
http://forum.tvfool.com/showpost.php...19&postcount=7