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TV Station signal strength

gary350

Well-Known Member
I am trying to learn TV station signal strength from the TVFool.com online chart?

30 years ago I dropped cable TV then built an antenna using Amateur Radio antenna handbook.
Next I bought 2 factory made antennas CM4228 the 8 bay bow tie antenna and Yagi B91X antenna.

I decided CM4228 works best for me because all my stations are between 299 and 329 degrees. Center is 314 degrees. The CM4228 picks up 12 degrees each side of center the B91X only picks up 5 degrees each side of center. I receive all channels by aiming antenna at 314 degrees magnetic using a compass and don't need an antenna rotor.

After reading the Amateur Radio antenna book I learned how to make changes to the CM4228 antenna to get a stronger signal. By adding a 48" x 48" reflector screen the reflector field strength meter shows a much stronger signal. By using reflector screen with smaller holes antenna works better on high frequency. By changing bow tie wires to aluminum sheet metal signal strength meter shows a very large increase. Next I built my own antenna using all the improvements. Next small hook up wire was changed to #12 solid copper. Next I put a balun on left and right have of the antenna then connected the 2 halves together in phase with a T combiner. Field strength meter shows 95% to 100% on all channels. My antenna is over kill to the point no matter how hard it, rains, snows, fog, clouds, hail, wind, forest of trees between the antenna and stations with antenna only 8 ft high signal is never lost any of the 44 channels from 45 miles away in Nashville TN. If I rotate to 329 degrees I can even receive channel 6 from Lebanon TN.

If I rotate the antenna by hand I receive other stations 72 miles away.

I moved to Phoenix AZ for 3 years all the stations are up on south mountain elevation about 3000 feet I could receive all the stations 88 channels 92 miles away from Lake Pleasant AZ.

I mentioned this to the guys on the OTA TV antenna forum they can look at the TVFool chart and know exactly how strong the station signal is but I never did understand how they know that?

They also said, channel 6 is such a low power station we don't see how you can receive it.

How do number on the chart tell how strong the TV station signal is?




118468

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ronsimpson

Well-Known Member
Most Helpful Member
Nice antenna!
Please post the dementions of the bow tie(s).
I need to pick up North and South but not any other direction. So I want a antenna with out a reflector.
 

gary350

Well-Known Member
Nice antenna!
Please post the dementions of the bow tie(s).
I need to pick up North and South but not any other direction. So I want a antenna with out a reflector.
Bow ties are 1" wide on small end, 5" wide on large end, 10" long. I have tried several different lengths it does not seem to make much difference field strength is only slightly different on real channel 5 and real channel 50.
 

Tony Stewart

Well-Known Member
Most Helpful Member
I can pick up about a dozen stations from Buffalo and all the local Toronto Stations using my antenna , but it seems to be losing signals on the edge more often now. TVFool has a reverse radar plot with distance towards the centre showing signal power but also has the tables with dBm and is also color coded grey My furthest signal is 96 miles but tuning to 1 or 2 deg is necessary.1558763020956.png

Gary, WHen I get time, I think I will try your antenna. Any details on the Balun? Although I might tune the wavelength to the lower frequencies I use.



I added LEDstrips to my antenna so we can see it from blocks away at nite
118483118484118485
 
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Nigel Goodwin

Super Moderator
Most Helpful Member
The 'bow tie' (short back fire array) aerials are low gain, wideband, and good for anti-ghosting - so pretty pointless in this age of digital TV (where ghosting isn't an issue) - you're better off with a wideband yagi if you're wanting distant reception, or if it's for a particular staion, then a narrow band yagi is even better (less bandwidth = more gain).

As for signal prediction sites, that's all they are - predictions - x miles away, signal drops y percent per mile, simple maths. In practice they only tend to be correct where you would have no need to check, because it's blindingly obvious. In the situations where an accurate prediction would be useful they are normally worse than useless.

The best UK one is: http://www.wolfbane.net/cgi-bin/tvd.exe? - mostly because it gives you a nice list of possible transmitters.

This is a DX list for the address where I used to work (at a TV Shop), Birchover and Darley Dale are listed but you don't have a prayer of those. Likewise Sutton Coldfield is listed, and we used to have a large double aerial (2x46 element), with multiple amplifiers, just to get BBC2 from there - with a very poor snowy picture, but it allowed us to test colour TV's back before the local relays were built. Everything below that, not a prayer either. Bear in mind the location is the bottom of a valley, Sutton Coldfield only just creeps in because the valley bends that way, so it's less obstructed by hills.

DX.png

On the other hand where I live it lists Emley Moor as requiring a Hi-Gain aerial, yet it's immensely strong, and in the past I used to need an attenuator in the aerial lead to prevent problems - I don't need it now, as the aerial feeds through the cellar via a VERY old coaxial cable, which is faulty and makes a large loss through it. I've never got round to replacing it, as it works perfectly well and saves using an attenuator :D
 

gary350

Well-Known Member
Gary, WHen I get time, I think I will try your antenna. Any details on the Balun? Although I might tune the wavelength to the lower frequencies I use.
I bough 7 Baluns and tested them, 1 did not work at all, 2 had lower signal than the other 4. I kept the best 4 baluns then returned the others to Walmart for a refund. I have been intending on making my own baluns but so far I have not done it. I learned each 4 bay antenna must be connected in phase with each other. I also learned something else unexpected, connect 1 balun to a 4 bay then test it with field strength meter then swap the 2 balun wires I always get a stronger signal with wires connected one way or the other. Leave balun connected with strongest signal. Next connect balun to the other 4 bay and connect both baluns to a T combiner with 18" long coax on each balun. Check signal with field strength at T combiner when swapping wires on the other balun signal get stronger when connected in phase and weaker when connected out of phase. Once both baluns are connected to have the strongest signal that is how I leave it connected. Use 1 continuous coax from T combiner to TV. I also learned from experimenting screen reflector can be adjusted in/out from 5" spacing to 14" spacing between screen reflector to bow ties to tune in different hard to receive frequencies. When screen reflector is closer to bow ties it has stronger signal on high frequency. Smaller holes in screen reflector gives stronger signal on high frequency too. I was having trouble at first getting a good strong signal for real channel 5 and real channel 50 changing to small screen holes pulled in channel 50 and changing the bow ties from wire to solid metal pulled in channel 5 the whole antenna had a much stronger signal. Changing wire bow ties from wire to solid metal made field strength meter so way up from 70 to 98 on field strength meter for the channel I was testing. Field strength meter will test different on each channel so test all channels 1 by 1 and make adjustments for each channel to get what works best for the channels you receive. I hesitate to tell people how well this antenna works most people don't believe it. I have noticed when sun is low on the horizon signal is lower on all channels for about 1 hour in the evening. My yard has hot spots if I move the antenna around different places I can find places where antenna gets a stronger signal. It is not practical to have my antenna is a strange location like center of the garden or middle of the front yard near the street. I can pick up an ok signal from stations 90 miles east of us but some days signal is harder to receive than others. I have no trouble picking up cookville channels 72 miles away but they are exact same programming as Nashville so why bother turning the antenna just to receive the same programs. I have also learned if I aim the antenna in the correct direction using TV fool and a compass then tip antenna up into the sky about 35 degree angle I can sometimes pick up stations 120 miles away. It was a challenge and FUN making the antenna better and better I never have signal fade or flicker it works excellent for me at 45 miles from all the stations I receive. We never watch TV when we go camping but I have taken this antenna camping many times all over the USA just to see how many stations it will receive and it works great in the middle of a forest, beach, desert, mountains, wilderness, long way from the stations it is nice to check weather conditions and storms especially radar reports for tornadoes.

Looking at TVFOOL how can you tell a certain station has a strong long range signal?118504
 
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KeepItSimpleStupid

Well-Known Member
Most Helpful Member
While we have the antenna guru;s here and we're talking about signal strength. If the antenna looks crooked, it was before it was repaired and straightened. There are no good pics of the 8200U online and I don;t have one in the detailed area.

I'm tallking about the largest element and itt's "connections". The "long_element" picture. The original rusted rivet is shown Kapton taed to the boom. The square are would be covered by a plastic cap.

So, the rivet goes through that mess and it;s all rusted.

The "C" shaped channels, basically connect the right and left halfs of the "elements" together. So, the top C channel may be the right side and the lower the left side.

The left and right side eventually connect to a plug in BALUN of some sort.

Since the rusted connections to the boom (rivet pass-thru) were dubius, I removed them. Whne I looked at YAGI construction, this connection did not appear the be there, Anyway, the connection is dubious and I removed it as seen with the heat shrink in both pictures.

The "close-up" pic is just the top and bottom of the long element pic with the heat-shrink clearly showm. One 1/2 element would attach to the upper support and the other 1/2 element would attach to the lower support going in the opposite sirection/


==

The initial install of the antenna fell. The aluminum mast cracked in half (have pics) and the antenna split in half. The antenna was repaired and some of the longer elements were replaced. They were flimsy anyway. I believe the diamer stayed the same. Rivets were replaced with stainless screws for any replaced or loose elements.

I want your opinion before I give Winegard's.

btw: I'm ina UHF/VHF area where physical channels 2, 3, 4, 6 and 12 are VHF.

Thanks,
 

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KeepItSimpleStupid

Well-Known Member
Most Helpful Member
The attached is part of my designed antenna eve mount. Two pieces of Unistrit/Superstrut straddle the top and bottom of the attic vent where EMT tubing provides the major part of the mast. This piece attaches to the horizontal Superstrut to provide the third guy wire support.

Guy "wires" were made from Phillystran, an non-conductive guy wire, Turnbuckles, et, were 316 or 318L stainless steel. A support bearing (NLA) was used as well. they guy wires were attached there. A rotator completes the ensemble. Two guy wires go thru the roof. the one unistrut fitting was like $80.00 USD.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
The initial install of the antenna fell. The aluminum mast cracked in half (have pics) and the antenna split in half. The antenna was repaired and some of the longer elements were replaced. They were flimsy anyway. I believe the diamer stayed the same. Rivets were replaced with stainless screws for any replaced or loose elements.
Back in the days (long ago - 70's) when we used to fit aerials at work there were some massive gales, and as a result we had a huge backlog of aerial jobs - so they asked for volunteers to work Sundays - it paid double time, so I volunteered (although I was an engineer in the workshop, I was also pretty experienced doing aerials, in particular sorting out any 'unusual' problems).

This was in the days prior to any local relays, so aerials tended to be large - and we went to a job at Dimple Farm (not really a farm any more, as even back then it was surrounded by houses), which was a large old farm house with a stone roof - none of your 'namby pamby' tiles or slates, this was inch thick sandstone slabs :D

The aerial was a double JBeam multi-beam (2x46 element UHF - later ones were 48 element) mounted atop a 12 foot pole on the chimney. The pole had snapped just above the top chimney lashing and the aerial had swung forward, perfectly aligned with the aerial heading, and both aerials had punched right through the stone roof :nailbiting:

We simply pulled the aerials out of the roof, straightened the rods with a pair of pliers, and refitted the now shorter pole back in the existing chimney brackets - where it worked fine.

Lesser aerials might have suffered damage, but the JBeam multibeams were exceptionally good aerials, both in performance and in their construction.
 

KeepItSimpleStupid

Well-Known Member
Most Helpful Member
Incidently, mine was chimney mount too. The pic of the sheared mast is attached.

--

The othe rpic is the rendering of what the eve mount was supposed to look like. The TB100 labeled is supposed to be a TB105, now discontinued,
https://www.copperelectronics.com/cart/NTE-TB105-Support-Bearing

I helped do some large dish satelie TV installs.
 

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JimB

Super Moderator
Most Helpful Member
The aerial was a double JBeam multi-beam
Quite coincidentally Jbeam Antennas flashed through my mind* earlier today.
What happened to them? the just seemed to disappear in the early 1980s.
They were THE VHF/UHF antenna manufacturers in the UK.

JimB

* It is amazing the rubbish which runs riot through my mind when I just let it wander.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Quite coincidentally Jbeam Antennas flashed through my mind* earlier today.
What happened to them? the just seemed to disappear in the early 1980s.
They were THE VHF/UHF antenna manufacturers in the UK.
I resume they went bust?, and were taken over by someone else, but I never actually knew.

They were far better than Antiference and others.
 

gary350

Well-Known Member
Lets start over for the 3rd time. This is all the information you get. How can you tell how strong signal is 40 miles away looking at TVFool chart?

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KeepItSimpleStupid

Well-Known Member
Most Helpful Member
I ran one actual number through the calculator here: https://www.rfmentor.com/content/dbm-dbw-dbuv-calculators
Z=75 ohms.

Specs with Antenna gain: https://manuals.solidsignal.com/HD8200U_Specs.pdf

Converted dbm (TVFool) to dbuV (Measured and predicted)
Chan....TVFool(dBm)....Predicted(dBuV).....Measured(dBuV)...........................................Measured+antenna gain
6..............-48.2...................60.55......................59.5........Antenna gain @ 6 = 6 dB.................59.5+6=65.5
32............-64.4...................44.35......................32.3........Antenna gain @ 32 =13.7dB.............32.3+13.7=46

The last column doesn;t make any sense. Measured minus antenna gain should be equal to
predicted, I would think.

Those numbers aren't too bad for agreement. They are at least in the ball park.
The higher the Noise Margin, the better the signal too.

When I checked say, a 10 dB attenuator, the dBuV value was 10 dBuV less.

You need about 80 dBuV for the antenna Input.
 
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JimB

Super Moderator
Most Helpful Member
OK lets try this...

Looking at TVFool for your location, I see this:
TV Fool 1.png
A bit clearer than your offscreen photo.

An interpretation of the numbers can be had by clicking here:
TV Fool 2.png

This will give the following information:
TV Fool 3.png


So, referring to the table of stations, we have a column titled Pwr(dBm) which is the signal power which is predicted to be received by a simple dipole antenna.
We also have NM(dB), which is the predicted noise margin, ie how clean the signal is likely to be.

Looking at the top line of the table for W3FB, we see that the signal strength is -35.8dBm, and the associated noise margin is 55 dB.
This represents a strong signal with very low noise.

If we look further down the table at WKUW, the signal strength is -84.6dBm and the noise margin is 6.2dB. A weak and noisy signal if we try to receive it using a simple dipole.
However, if we use a multi-element yagi with a gain of 20dB, the situation will be much improved.
The signal strength will become -64.6dBm and the noise margin will become 26.2dB, a much better signal with an acceptably now noise.

Does this help?

JimB
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Lets start over for the 3rd time. This is all the information you get. How can you tell how strong signal is 40 miles away looking at TVFool chart?
You can't, it's just a theoretical guess - based on simple mathematics - and has little resemblance to reality.

Even actual measurements are wildly inaccurate - I've seen them done by the BBC for a new transmitter.

First off, they only take measurements at a small number of locations, the rest are extrapolated - but worse, in the example I saw, the engineer raised the aerial on his van, selected BBC1 and rotated the aerial for maximum signal strength, he then selected BBC2 rotated the aerial for maximum strength again (NOT the same direction as before), then selected ITV and did the same rotation. So three maximum signal strengths, with the aerial pointing in three different directions - when I queried this, and asked if people were supposed to have three aerials pointing different directions, he didn't care at all.
 

gary350

Well-Known Member
I was on OTA antenna forum for many years when my computer crashed I lost the link to that forum and have never been able to find it again. When I moved to Phoenix Arizona area 8 yrs ago and told people how well my antenna works in AZ they looked at TVFool and many people said, WOW with signals like that coming from 3000 ft elevation on south mountain you can probably get excellent TV reception 70 miles away with rabbit ears or a piece of wire. I wonder what people are seeing on TVFool that shows a signal that good?
 

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