Phoenix Reception Problems

[clipfert]

Hi,
Here is the report:
http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3df1f0eb18ede651

We purchased the following antenna:
http://www.amazon.com/gp/product/B00MFXNQBU?psc=1&redirect=true&ref_=oh_aui_detailpage_o05_s00

(Note: I just returned the above antenna)

Would like to receive all major network channels.

So, we purchased the amazon 60 mile indoor/outdoor antenna and could get all major network channels except cbs. Directly south of our house we have four very large eucalyptus trees. We first tried placing the antenna in the attic with minimal luck. Next we tried outside in the middle of our yard and could get cbs but that placement won't work, so we placed the antenna on top of our porch, probably at a height of around 20 ft. positioned in between two of the trees and we could get all channels except cbs. My husband even tried holding the antenna on the chimney (receiving no channels from there). So the issue definitely seems to be the trees however we still couldn't get cbs which is a deal breaker because we'll be missing football!! Err.. does anyone have a suggestion for a better reasonably priced antenna? Location? Anything? Please help we've been doing trial and error for 3 weeks and finally gave up on the antenna.

[rabbit73]

Welcome to the forum, clipfert:

The Amazon antenna wasn't the best antenna for you, so it was a good idea to return it.

There are several problems with it. It consists of a small antenna combined with an integrated 15 dB amplifier. The amplifier is supposed to make up for the low gain of the antenna, but that doesn't work because if the signals aren't coming out of the antenna, the amplifier can't create them.

Another problem is that the amplifier can be overloaded by strong signals, so an amplifier should not be used for your location. Your TV signals are not extremely strong, but your FM signals are. Your strongest TV signal KAET has a Noise Margin of 45.2 dB, with a signal power of -45.7 dBm. However, your strongest FM signal KPHF has a signal power of -15.8 dBm, which is about 30 dB stronger. See Attachment No. 2.

http://forum.tvfool.com/attachment.php?attachmentid=1149&stc=1&d=1433343793

Interpreting Noise Margin in the TV Fool Report
http://www.aa6g.org/DTV/Reception/tvfool_nm.html

I suggest that you make some tests with an unamplified antenna with an FM filter inserted in the RG6 coax. The filter can be inside, out of the weather, because you will not be using a preamp. If you were using a preamp, the filter would need to be between the antenna and the input of the preamp.

The antennas to consider are the Winegard HD7694P, RCA ANT751, and Antennas Direct C2V.
http://www.solidsignal.com/pview.asp?p=hd7694p&d=winegard-vhf%2Fuhf-hdtv-antenna-(hd7694p)
http://www.solidsignal.com/pview.asp?p=ant751

Different FM filters have different characteristics. You have strong FM signals near 88 and 108 MHz, so neither the Antennas Direct or the Radio Shack would do, unless you put one of each in series. See Attachment No. 3.

I suggest two FM filters or HLSJs in series. The HLSJ makes a good FM filter because it blocks everything below TV channel 7, including the FM band.

http://www.mcmelectronics.com/product/DISTRIBUTED-BY-MCM-FM-88-/33-341
http://www.solidsignal.com/pview.asp?p=zhlsj

http://www.hollandelectronics.com/catalog/upload_file/Filters-Diplexers.pdf

If you use the HLSJ as an FM filter, connect the coax to the High and Common ports.

The coax shield should be grounded with a grounding block that is connected to the house electrical system ground with 10 gauge copper wire for electrical safety and to reject interference. For further compliance with the electrical code (NEC), the mast should also be grounded in a similar manner to drain any buildup of static charge, but the system will not survive a direct strike.
http://www.solidsignal.com/pview.asp?p=CM3274&d=Channel-Master-CM3274-Ground-Block-(CM3274)&q=ground block

[rickbb]

I don't think it was the trees so much, they do affect reception, but all of your stations are coming from the same location, 188 degrees. And the same distance 17.4 miles.

If you had issues with trees, it should have shown up on more channels than just the CBS station. It's the 4th strongest in your report.

Based on the terrain profile you need to mount your antenna as high as you can get it. The tower is on the left, your house is on the right down behind that mountain in a signal shadow.

https://www.tvfool.com/modeling/tmp/f1f0/eb1/8ede651/PRE-KPHO-DT.png

You also have VHF stations so you will need an antenna that will receive both VHF and UHF.

[clipfert]

Thanks for the reply rabbit but I'm not sure how this translates into the type of antenna to purchase. Any suggestions? What features should I be looking for?

[rabbit73]

see my post #2, I'm still working on it.

It doesn't need to be a large high gain antenna, but it must receive VHF-High (real channels 7-13) and UHF (14-51) signals.

OK?

Please let us know your test results on this same thread.

[ADTech]

I've found that there can be considerable variability between individual filters from the same shipment since they're hand assembled.

I tested a batch of 10 filters back in late 2010 from an incoming shipment that demonstrates the variability. From that batch, one filter only attenuated 108 MHz by 10 dB, another by 35 dB. The majority were between 15 and 22 or so.

http://forum.tvfool.com/attachment.php?attachmentid=1154&stc=1&d=1433353119

Here's a single RS 15-0024 that I tested back in Nov 2013. It's the only one I tested.

http://forum.tvfool.com/attachment.php?attachmentid=1153&stc=1&d=1433352436

[clipfert]

Rabbit, I appreciate all the information. Where did you find info about FM signals? I don't fully understand how they interfere with TV signals.

[rabbit73]

FM signals, which are between TV channel 6 and TV channel 7, can interfere with the reception of TV signals in several ways. They can cause fundamental overload of tuners and preamps in the VHF band, and even in the UHF band if they are strong enough. The second harmonic of an FM signal can interfere with a VHF-High (7-13) TV signal. Very strong FM signals at around 88 MHz can cause adjacent channel interference to TV channel 6.

This is an analysis I did for dbseeker:
thread:
http://forum.tvfool.com/showthread.php?t=14415
my post:
http://forum.tvfool.com/showpost.php?p=51412&postcount=15

THREE TYPES OF OVERLOAD

There are three types of preamp or tuner overload, in order of increasing signal strength:

1. The strong signals almost cause enough intermodulation distortion (IMD) to interfere with the reception of weak desired signals, but the spurious signals are at or below the noise floor. This is the point that holl_ands uses in his preamp charts to obtain max SFDR (Spurious Free Dynamic Range). No damage will happen.

As the strongest signals continue to increase in strength, more of the weaker signals are damaged until you reach:

2. The strong signals cause overload to the preamp or tuner that makes it impossible to receive any signals. No damage will happen. The strongest signals are still there, but they can't be decoded because the IMD products have damaged them so that they contain more errors (high BER....bit error ratio/rate) than can be corrected by the FEC (forward error correction).

3. The signals are so strong that the input transistor is toast. You are not likely to encounter OTA signals that strong, unless you live next door to a high power transmitter and you have your high gain antenna aimed at the transmitter's antenna.

As a general rule, tuners can tolerate stronger signals than preamps before overload. The difference in strength is approx. equal to the preamp gain.

Forum member holl_ands has made a preamp chart that shows the maximum input signal for preamps. Many of the preamps are no longer available, but it gives you the general idea.

http://imageevent.com/holl_ands/files/ota?p=15&n=1&m=-1&c=3&l=0&w=1&s=0&z=4

Intermodulation Distortion

The IMD creates new spurious signals within the preamp itself that can interfere with the reception of your weakest desired signals if the spurious signals are stronger than the noise floor of the weakest desired signals. The spurious signals are caused by the interaction between two or more of your strongest signals.

IMD is not the only distortion that can be created within the preamp; you can also have distortion caused by signals so strong that the top of the strong signals are clipped, which causes compression of the signals. This can be seen if you increase the input to the preamp by, for example, 10 dB and the output increases by less than 10 dB.

Spurious Free Dynamic Range

The Spurious Free Dynamic Range needed is the difference in strength between your strongest signal and your weakest desired signal, using the dBm Pwr scale on your tvfool report. This difference is expressed in terms of dB, not dBm, because the original units are the same. To this you must add 16 dB that is required for the SNR of the weakest desired signal.

Another way to think of it is from the top of the strongest signal down to the bottom (noise floor) of the weakest desired signal. The top of the spurious signals must be at or below the noise floor if they are not to cause interference.

You can also use the NM scale for your calculations, but I prefer to use the Pwr scale because most tuners drop out around -85 dBm.

The second harmonic of an FM signal can interfere with a VHF-High signal if its frequency is 1/2 the frequency of the tV signal:

Testing for DTV Interference
http://www.tvtechnology.com/digital-tv/0148/testing-for-dtv-interference/202503

Strong FM signals at the low end of the FM band (88 MHz) can cause co-channel interference to CH 6 TV signals that are just below 88 MHz.

http://forum.tvfool.com/attachment.php?attachmentid=1171&stc=1&d=1433469297

[mikelessard]

I agree with rabbit except the RCA ANT751 isn't going a have enough umph. The Winegard has twice the gain and isn't that much more. I had an antenna almost exactly like the RCA and I had to upgrade it to one of the last Antennacraft HBU33's when the leaves came out. My whole goal of installing an outdoor antenna is I not into pixels and dropouts and missing football plays. Makes me crabby!