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Televes Hi-VHF Yagi

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jimh
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Televes Hi-VHF Yagi

Post by jimh » Tue Jun 06, 2023 3:03 pm

In April 2023 I bought a Televes seven-element Hi-VHF Yagi from SOLID SIGNAL in Novi, Michigan, placing a telephone order and then driving over to their headquarters to pick-up the antenna in person about 90-minutes later. (Due to road construction, it is almost impossible to drive directly to their location from my location, and I encountered about five road detours in the route getting there.)

The purpose of buying the Televes Hi-VHF Yagi was to improve reception of CBET-09 from Windsor, Ontario at my location. The antenna that was in use (a short log-periodic array or LPA) was not delivering reliable reception as the air temperature warmed and foliage came onto the trees at my location. The start of coverage on CBC of the Stanley Cup Playoffs necessitated getting a better signal for the next two months.

Here are some observations about the antenna.

TELEVES Hi-VHF Antenna, Model 106501

DESCRIPTION
The antenna is nicely packaged in a long cardboard box. There are no large and ugly staples in the box. It opens without any problem and without having to cut away anything.

The mechanical design is excellent. All elements are held in contact with the 20mm aluminum square tube boom with cast white-metal clamps that have a threaded boss that receives a 10mm hex-head machine screw through-bolted through a pre-drilled hole in the boom that determines all element locations along the boom. The clamps have a recess cut out that matches the boom width, and this positions each element perfectly orthogonal to the boom. All the parasitic elements are connected at their centers to the boom by this clamp. The clamps tends to fatten the element at the boom center area.

The 20mm square boom assembles from two pieces using a plastic joining plug. One side of the plug is press fit into one of the boom sections. A 10-mm hex head screw and a nut with cast-in lock washer joins the other boom piece to the plastic plug with a snug fit. Because of the plastic plug, there is NO ELECTRICAL conductivity between the two boom sections. This seems odd to me. I contacted Televes at their USA operation to inquire about the split-boom conductivity. They assured me it was part of the intended design.

The longer section of the two-piece boom contains the reflector, the driven element, the very close-spaced first director, and the wider spaced second director, making a four-element antenna.

The shorter boom section contains the third, fourth, and fifth directors, but they have no DC continuity to the other boom and its elements. This section adds three more elements to the other half.

The durability of this antenna should be extremely good. It should withstand wind and weather for decades—perhaps outliving television broadcasting itself.

ELEMENT DETAILS
The diameter of all elements is 8mm round aluminum tube. The element tubing at the outer ends is nicely machined to a rounded termination so there are no sharp machined edges. The boom ends are filled with plastic press-in plugs.

The reflector length is 35-1/5-inches.

The driven element is a folded dipole with a spacing of just under 2.5-inches on center to the elements and a length of 28-3/8-inches.

There is no electrical DC continuity between the driven element and the boom.

The director elements taper as follow (in inches)
1. 23-5/8
2. 23-1/4
3. 22-7/8
4. 22-3/8
5. 21-5/8

The element spacing is non-uniform and varies slightly, but the first director is very close spaced compared to the reflector and the remaining directors. The close spaced first director seems to be common in TV antenna designs. I suspect it affects the input impedance of the antenna more than anything else. Clearly this is not a cook-book design where directors are equal length and element spacing is constant.

The overall length of the boom is about 55.5-inches or 4-feet 7.5-inches.

ASSEMBLY
The assembly was not difficult, but you MUST have a 10-mm wrench or socket driver. A wrench is not provided in the package.

The driven element is pre-assembled to a plastic fitting that contains the balun (enclosed in a metal sealed tub) and the antenna's feed point F-connector. This assembly must be carefully positioned onto the boom to properly locate it. Be sure to carefully observe the photographs and drawings in the instructions for location. The molded yellow plastic housing is designed to snap-fit onto the boom and can be quite stiff to pry apart for fitting onto the boom before it snaps into place. I think it could be broken if not handled carefully. There are two holes in the boom associated with the driven element. One hole is for the retaining bolt and the other is for a locating pin molded onto the plastic snap-on channel.

BOOM TO MAST MOUNT
The antenna is designed to be mounted to a mast with non-symmetrical alignment. The Boom-to-Mast clamp is intended to be located between the reflector and the driven element. The Boon-to-Mast steel hardware is very strong, considering the overall light weight of the antenna. In my installation the mast is non-conductive and is oriented horizontally, in the same plane as the elements. This is a result of the unusual indoor installation.

PERFORMANCE
Before changing to the new antenna, I tuned to CBET-9 and observed the relative signal indicator (RSI) and the SNR indicator. This was done about 3 p.m. so I would not expect any sudden change in temperature to occur. The little Log-Periodic Array (LPA) antenna was RSI=41 and SNR=16.

I took down the LPA and put the Televes in its place. This took a while as I had to fiddle with the mounting to get the boom to be more balanced. My mast is a horizontal arm and I didn't want too much twisting force on it from the antenna. By the time I returned to the TV set to see the diagnostic readings, perhaps 45 minutes had passed. I cannot easily A/B test them as they have to be mounted in the same position--no room for two antennas at once.

My initial readings of RSI and SNR were just about identical--which was a disappointment. I was expecting the Televes to have much more gain at CH-9 than the LPA which covers a wider frequency range, up to 1000-MHz and only has perhaps three elements in the HI-VHF range. I guess that the LPA must have about 5 dBi gain, maybe 6 dBi. The Televes advertises 9.5 dBi gain.

After watching several hours of CBET-9, I did observe one improvement. With the LPA the picture would badly deteriorate anytime the SNR was below 16, and at SNR 15 it would have significant defects. The audio would be almost totally gone.

With the Televes at SNR 15 the picture is almost rock solid, and the audio is almost perfect, I am speculating that perhaps the Televes has a sharper pattern and ignores more multipath signals, so the errors are fewer even at 15 dB. At 16 dB SNR the Televes is perfect picture and audio.

Next I watched four hours of hockey broadcast. I only noticed a few low signal artifacts, and they only lasted perhaps ten to 15 seconds. This makes me think those low signal artifacts were perhaps caused by aircraft or some other temporary interference. Previously with the LPA, when the picture started to break up it would continue that trend downward and not recover for maybe an hour or more, indicative of some slow propagation fade and return. (Re aircraft, we are overflow here by planes approaching DTW for runways 21 and 22 for landing, or if the wind shifts, by planes climbing out from take off on runways 03 and 04.)

Also, I experimented with putting a notch-filter for CH-07 in the feed. I was thinking that perhaps with the Televes there would be a lot of gain at CH-07. The antenna is not aimed right at WJBK ("TV2" but transmitting on RF-07), but it is aimed in that same quadrant. I thought perhaps there was so much RF-07 going into the TV receiver that it was messing with RF-09, probably many tens of decibels weaker. But I did not see a significant change in RSI or SNR with the insertion of the RF-07 notch filter.

I also took out my LTE filter in an attempt to get better signal from CBET-09. This seemed to help the RSI a tiny bit, but not the SNR.

NEXT STEP
I moved the boom-to-mast mount to the position Televes intended for it. After this change and on this particular day of testing, CBET-09 was producing a SNR of 18 dB, a value never seen with the LPA antenna. Perhaps the mounting bracket placement is more critical that one might think.

I realize my testing was not strictly scientific, but I think moving the boom-to-mast mount to the intended location (between the folded dipole and the long reflector element) may have improved the antenna gain or pattern. The mount is a rather large chunk of metal and may have an influence on the antenna response. In my initial position for the boom mount it was between the first director and second director. The first director is very close-spaced to the folded dipole driven element, so having a big piece of metal there may have thrown off some of the gain or pattern intended.

At this point I was very satisfied with reception of CBET-09 with the Televes Hi-VHF Yagi. I recorded many broadcasts of the hockey games for later viewing, and there were almost zero picture or audio glitches in any of the recordings.

TEMPERATURE RISING
By late May and early June, the air temperature had risen to be almost 90-degrees on some days. The warm air seems to affect reception of CBET-09, and the relative signal strength (RSI) indicator was trending downward, from the usual 42 to perhaps 38. The SNR on CBET-09 was down as low as 14 to 15 dB, resulting in picture and sound that were no longer completely free of glitches over a several hour broadcast.

I decided to experiment in improving the SNR by elimination of any locally generated interference.

RECEIVING ENVIRONMENT
The antenna is mounted indoors near the ceiling of a second storey room at my home, and looks out a large window on a direct line to CBET. The path should be line-of-sight with regard to terrain, but there are many tall buildings in downtown Detroit that are not far from the path line.

In the same room are two personal computers, two HDMI monitors, a WiFi base station, a large flat scanner, and a wired Ethernet hub with five connected devices. The main computer is usually always powered on, but it enters "sleep" mode after a few minutes of inactivity. I had already observed that with the main computer (Mac Mini) running and NOT in sleep mode there was significant interference occurring, but on some further investigation, I discovered that the actual main source of interference was the HP computer monitor display; the computer itself was not particularly causing interference. Further experimentation found that shutting off the WiFi hub and the Ethernet hub--basically shutting off everything at the computer desk--yielded another significant gain in reception; typically the SNR would improve another 2 dB with everything shut off.

SUMMARY
With reduction of local interference, I continue to be able to get excellent reception of CBET-09 even with the hot summer weather and trees in full foliage with the Televes Hi-VHF antenna. I am still able to get signals of 18-dB SNR, and glitch-free reception down to 15-dB (indicated) SNR. The antenna's $60 cost was well worth the investment. Usually by this time of the year, there would be no trace of CBET-09 on my television receiver.

Although the Televes Hi-VHF yagi is intended for use on 174 to 230-Mhz, it also works well for receiving the local UHF signals from the Detroit market stations in the 500 to 600 Mhz range. The relationship of the two bands is about three-to-one. Antennas designed for a particular frequency often exhibit some resonance on their third harmonic.

ABOUT TELEVES
In March and April 2023 I was in Spain for over three weeks. Spanish people appear to have much greater interest in receiving their television signals by over the air, and I saw literally hundreds and hundreds of home or apartment buildings with television antennas on the roof, far more than you would see in the metro Detroit area. There appears to be a big market for television antennas in Spain, which probably accounts for Televes being in the antenna manufacturing business there for over 70 years.
Last edited by jimh on Fri Nov 10, 2023 8:35 pm, edited 3 times in total.



Round Six
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Re: Televes Hi-VHF Yagi

Post by Round Six » Wed Jun 07, 2023 11:55 am

jimh:
Do you own the home you live in?


Women spend more time wondering what men are thinking about than men spend actually thinking.

jimh
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Re: Televes Hi-VHF Yagi

Post by jimh » Wed Jun 07, 2023 5:39 pm

Round Six wrote:
Wed Jun 07, 2023 11:55 am
Do you own the home you live in?
I own the home, but it is in a condominium association.



Round Six
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Re: Televes Hi-VHF Yagi

Post by Round Six » Wed Jun 07, 2023 6:24 pm

jimh wrote:
Wed Jun 07, 2023 5:39 pm
I own the home, but it is in a condominium association.
Okay. Explains what I was wondering.
Thanks.


Women spend more time wondering what men are thinking about than men spend actually thinking.

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Ben Zonia
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Re: Televes Hi-VHF Yagi

Post by Ben Zonia » Wed Jun 07, 2023 9:28 pm

Does anyone have an actual pattern for the antenna? Yagis like this usually have less gain and worse front to back ratio than the Winegard 7698.

As you get further West and North into the high land ski areas in Oakland County above 1000 feet, I suspect that late Night will bring in a lot of Tropospheric interference from WWTV 9, which is also on Physical Channel 9. It always did in the analog days. And WWTV 9 is substantially higher ERP, 45 kW, with a CP for 51.8 kW, than most VHF High stations. CBET 9 is not intended to serve the US, though it was fully spaced to WWTV 9 under analog rules, though with a higher HAAT than CBET 9.

I suspect that this entry link is not corrected for peak vs. average, as Canadian stations use average, though 26 kW is the peak ERP, so you many need to adjust the ERP accordingly in different directions.

https://www.fccdata.org/?lang=en&cantv=CBET-DT


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jimh
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Re: Televes Hi-VHF Yagi

Post by jimh » Fri Jun 09, 2023 9:56 am

Televes publishes the antenna horizontal and vertical directional pattern, and specifies a F/B ratio of greater than 20 dB.

Cf.: https://www.televes.com/us/g-008-high-vhf-antenna.html

I discard the proposed notion that the cause of interference to reception of CBET-09 at my location is from WWTV-9 in Cadillac, Michigan, and the Televes antenna pattern is insufficient to reject the signal arriving off the back of the antenna.

My location is not in northern Oakland county. My location is not at a ground elevation of 1,000 feet or higher. I am in Bingham Farms, and not on a hilltop.

Reception of CBET-09 tends to always improve at night due to decrease in air temperature.



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Ben Zonia
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Re: Televes Hi-VHF Yagi

Post by Ben Zonia » Fri Jun 09, 2023 1:21 pm

I just found the additional specifications page, and I would like to post, but I can't get the address to post actual relevant images.

First of all the maximum gain is around 9.5 dBi, which is 7.35 dBd, and this is at around 230 MHz, outside the US Channel 7-13 range, 174-216 MHz. That range is mainly in the 7.5 dBi, 5.35 dBd, range. It might work well on the 1.25 Meter Amateur Radio Band, if you could match it to 50 ohms to minimize VSWR.

I don't doubt that this is a much better choice than most people are using for VHF-High OTA reception though. Can you get WTOL 11 and WTVG 13 well on it from your receiving location?


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Ben Zonia
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Re: Televes Hi-VHF Yagi

Post by Ben Zonia » Fri Jun 09, 2023 6:22 pm

This antenna is actually designed for Channels 5-12 in Spain. Which explains why the highest gain is at around 230 MHz. Here are the Channels 5-12 in Spain. Not saying it's not a decent antenna, but not really designed for our Channels 7-13, and could be redesigned better for the US and Canada. But you would have to ADD length to the elements, not snip elements to shorten them, like people used to snip Channel 6 Yagis for FM, like they did in my High School Electronics Class in the 1960s for the Heathkit FM Tuner a previous class had built.

WXYZ-FM changed to WRIF in that period, and the more album oriented elements of the Electronics Class always had it on to listen to Arthur P play the latest from "Mr. Hendrix".

5 175.25 177.5 180.75
6 182.25 184.5 187.75
7 189.25 191.5 194.75
8 196.25 198.5 201.75
9 203.25 205.5 208.75
10 210.25 212.5 215.75
11 217.25 219.5 222.75
12 224.25 226.5 229.75


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jimh
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Re: Televes Hi-VHF Yagi

Post by jimh » Sat Jun 10, 2023 8:48 am

When a Televes antenna made in Spain is used in the United States to receive a signal from Canada, the antenna does not behave any differently than it would in Spain to receive a signal from a Spain.

CBET-09 transmits on 186 to 192-MHz, which is in the designed frequency range of the Televes Hi-VHF yagi.

All Yagi antennas tend to exhibit a rise in gain with rise in frequency.

As I very clearly described in my initial post, the Televes Hi-VHF yagi is an extremely well made antenna, is readily available, and is of reasonable size and cost. It has significantly improved reception of CBET-09 at my location. I don’t see much not to like.



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Re: Televes Hi-VHF Yagi

Post by jimh » Sat Jun 10, 2023 9:04 am

Regarding a comparison being made of the Televes Hi-VHF yagi to a VHF/UHF very large Winegard 7698 antenna: the claimed improvement in front-to-back ratio is not supported by anything other than apparent anecdotal comment. I am not inclined to accept such claims unless some controlled comparison test data is provided. Televes gives a specification for F/B ratio and a pattern plot. Where are those data for the 7698 Weingard antenna?

Further, using a highly directive yagi to receive UHF signals in my location is not likely to be productive because the azimuth heading to the stations of interest are not well aligned in a single direction. Long yagi antennas usually have rather narrow main lobes with very deep nulls alongside them.



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Re: Televes Hi-VHF Yagi

Post by MWmetalhead » Sat Jun 10, 2023 9:09 am

My location is not in northern Oakland county. My location is not at a ground elevation of 1,000 feet or higher. I am in Bingham Farms, and not on a hilltop.
You're pretty close to me location wise, and I can concur reception of channel 9 is difficult here.

CBET broadcasts a directional signal pattern. There is a null in the direction of Pontiac. Maybe 6 kW to 7 kW ERP radiates in the direction of Bingham Farms. CBET's transmitting antenna sits about 370 meters above sea level whereas WJBK's (as a point of comparison) is 520 meters above sea level.

When one takes all of the above factors into account, plus the fact the downriver steel mills, refinery, Southfield's high rises and other forms of urban development stand in the way between the CBET TX site and Bingham Farms (the Southfield high rises also could lead to multi-path issues perhaps), it's no surprise that reception of CBET in Jim's neck of the woods is very challenging.

The fact a fairly small outdoor antenna, after some effort with positioning, is able to pick up CBET decently is a pretty good feat.



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Ben Zonia
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Re: Televes Hi-VHF Yagi

Post by Ben Zonia » Sat Jun 10, 2023 10:41 am

I never said the antenna wasn't DECENT compared to what most people have. But the data are misleading. The 230 MHz region, where the highest gain for the antenna is reached, around 9.5 dBi (7.35 dBd), is used in Spain, but not the US. We only use up to 216 MHz in the US and Canada. The channel 9 region shows about 7.6 dBi, which is only 5.45 dBd. Also, I'd like to see the F/B and Front To Largest Side ratios as a function of frequency, especially on channels 7-13.

I have sent the information on the Televes antenna to a man who has analyzed many TV and FM antennas using a method similar to "Method of Moments", analyzing each segment of each element and the dimensions and spacings of the elements. I hope he responds. He analyzed the Denny's Antenna Service FM 2500HD, which was promoted here and on many message boards as an FM antenna. He found it lacking in many ways, not the least of which is that it is not really an FM antenna, but a VHF-High TV antenna. The Televes needs to be redesigned for the US and Canada, and reoptimized for 174-216 MHz. That would give better gain and directivity on Channel 9. As I said, you couldn't easily add length to each element to optimize it. The man has also designed a "Home Depot" construction materials, home brew optimized antenna for 174-216 MHz.

At one location, I have an attic mounted 7 Element Archer/Antennacraft V-110 Log Periodic VHF antenna, at a somewhat further distance than yours. Not only does it provide reliable service every time I pass CBET 9-1 surfing channels, but it now also provides reliable service on WHNE-LD Channel 3, which has many subchannels. They should bring that design back.

https://worldradiohistory.com/hd2/IDX-C ... e-0103.pdf

It seems like the stations have problems though with the digital TV transmitters, and are often not at full power, and of course all the repacking problems, and off air or reduced power periods as a result.

For this link, to obtain the correct ERP for CBET 9, double the ERP shown in each direction. The shallow null roughly toward Pontiac would thus be 8.4 kW ERP.

https://www.fccdata.org/?lang=en&cantv=CBET-DT


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Re: Televes Hi-VHF Yagi

Post by Ben Zonia » Sat Jun 10, 2023 11:37 am

As you requested, the Winegard HD7698 Technical Data.

https://www.solidsignal.com/Manuals/HD7698_Specs.pdf

Note that the gain on Channel 9 is 12.6 dBd, which is 14.75 dBi, which is 14.75-7.6=7.15 dB greater than the Televes, which is more than twice the signal strength. Yes, it's large and more expensive, but I think you would notice the difference.


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Re: Televes Hi-VHF Yagi

Post by MWmetalhead » Sat Jun 10, 2023 12:26 pm

The model of the Televes antenna in question would certainly be a poor choice for those desirous of VHF low reception over a significant distance.

They do have other models that might work decently for that, though.



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Re: Televes Hi-VHF Yagi

Post by jimh » Sat Jun 10, 2023 12:53 pm

Comparing an antenna that costs $60 and can be easily used indoors—which is where I need to use the antenna—to an antenna that costs $240 and is essentially impossible to use indoors or even in an attic is not a particularly apt comparison.

I am certain that an array of the four compact Televes yagis would be far superior to that old-school Wineguard antenna in gain and pattern on RF-09 reception. A four-square yagi would have a very large aperture. But it would not fit in my second storey indoor setting.

No accurate modeling of the Televes Hi-VHF yagi can occur without knowing the element spacing dimensions, which are not given in their literature or in my remarks. So the outcome of such a project is hardly going to be credible.
Last edited by jimh on Sat Jun 10, 2023 1:03 pm, edited 2 times in total.



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