RCA ANT751 How is it on VHF?

Mark P

DTVUSA Rookie
#1
I have a single VHF station 22 miles away from my house LOS. Was thinking about RCA ANT751 after seeing it on recommended on avs for uhf/vhf antenna. It's pretty small. Is it mandatory to use with a preamp if the antenna is only going to be 20' away from my TV?
 

EscapeVelocity

Moderator, , Webmaster of EV's Antenna Blog
#2
The numbers Ive seen from a NEC model is 7.5 dbd on Channel 7, slightly higher through the middle of VHF Hi and a dropoff on channel 12 and 13. However this dropoff is suspect, as the Winegard 10 element VHF Hi antenna also displayed this, and its great on 12 and 13.

So, the short answer is 7 to 9 dbd gain (over a reference dipole) on VHF High (Channel 7 to 9).

Ch 14 4dbd
Ch 30 5dbd
Ch 50 6dbd

or there abouts...

The UHF specs are from the front end of a Winegard 7000R. You can see that even it with the longer elements for VHF Low is only getting just above reference dipole gain. The 7000R is worth consideration if you need VHF Low as well and are within 25 miles of the towers. Its well built as well. My guess is that Winegard makes the RCA ANT751 too, which is also well built.

On VHF Low (Ch. 2-6), with the RCA ANT751, I would expect negative gain compared to reference dipole cut to channel....40" length telescoping Rabbit Ears will be better.
 
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Don_M

DTVUSA Member
#3
Hi, Mark, and welcome to the forums here! If you plan to place the ANT751 outside at least several feet off the ground (higher being better) and point it directly at that station 22 miles away, it should be enough antenna to capture a full-power VHF signal on one TV 20 feet away without an amplifier. It should also do a reasonable job capturing UHF digital signals under similar circumstances.

An indoor installation is dicier if signal-blocking building materials (brick, stucco, aluminum siding, or foil-lined insulation or vapor barrier) stand in the way. That antenna should perform OK if the framing and siding are wood and/or the roof has asphalt shingles over a wooden deck and rafters.
 

Piggie

Super Moderator
#6
The numbers Ive seen from a NEC model is 7.5 dbd on Channel 7, slightly higher through the middle of VHF Hi and a dropoff on channel 12 and 13. However this dropoff is suspect, as the Winegard 10 element VHF Hi antenna also displayed this, and its great on 12 and 13.
I own two of those 10 element Winegards stacked 40 inches over each other. Winegard suggested 42 inches for channel 11. My calculations said 40 inches for the center of the band or channel 10 . I don't think 2 inches makes that much difference on VHF. 10 inches does. I experimented at 60 poor no better than one antenna, 50 no more gain but less drop outs, the at 40 inches I saw the gain pop alive.

I use my on channels 7,9,10, 13 and I don't think I agree with Ken's modeling that they don't have gain on Channel 13, it's one of my best channels. Though they pick up a 18 KW stations at 61 miles that is 2 edge from a 300 meter tower. Well unless there is tropo or impluse.
 

EscapeVelocity

Moderator, , Webmaster of EV's Antenna Blog
#7
So, the short answer is 7 to 9 dbd gain (over a reference dipole) on VHF High (Channel 7 to 9). -- EV
That should read...

So, the short answer is 7 to 9 dbd gain (over a reference dipole) on VHF High (Channel 7 to 13)
 

Piggie

Super Moderator
#8
That should read...

So, the short answer is 7 to 9 dbd gain (over a reference dipole) on VHF High (Channel 7 to 13)
I missed that reading too fast.

Actually that seems too high of gain for that antenna from my "instinct" of seeing antennas for seems like forever at this point

If NEC software must have limitations. But don't get me wrong, not bad mouthing NEC software nor the RCA ANT751 both are good products in their niche. (I know almost nothing about the NEC software except the results of this antenna and the YA-1713).

Remember in the Lava thread, Boom Length is king. The RCA ANT751 is 35.16 and the boom to mast is ubolt is about 2 inches. So probably at best the boom length is 33 inches. Or shorter if you don't count the UHF section.

I can't see getting that much gain out of 0.55 wavelength boom (based on the middle of the band (195 MHz).

The Y5-7-13 has a boom length of 0.99 wavelengths and the YA-6713 has 0.85 wavelengths. Both have fairly well documented gain in the 7 dbd range.

I would lean toward the RCA ANT751 having closer to 3 to 5 dbd on high band.

Still for someone in a little too weak for indoor and needs VHF also, in suburban level signal ranges it is a niche filling antenna. If one doesn't need end mounting the same gain should be achieved at half the price with a Winegard HD7000R
 
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EscapeVelocity

Moderator, , Webmaster of EV's Antenna Blog
#9
Makes sense.


Just playing Devil's Advocate, Winegard is claiming 5db on the 7000R, and the RCA ANT751 ditches the VHF Low elements and focuses on VHF High with a log-yagi design and 2 directors....which would back up claims that the RCA ANT751 is getting at least more then the 7000R. If we accept that Winegards posted figures are accurate, then the RCA has 6db or better gain on VHF High....but even their's dips at channel 13.

Interesting discussion.
 
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Piggie

Super Moderator
#11
Makes sense.


Just playing Devil's Advocate, Winegard is claiming 5db on the 7000R, and the RCA ANT751 ditches the VHF Low elements and focuses on VHF High with a log-yagi design and 2 directors....which would back up claims that the RCA ANT751 is getting at least more then the 7000R. If we accept that Winegards posted figures are accurate, then the RCA has 6db or better gain on VHF High....but even their's dips at channel 13.

Interesting discussion.
I love Devil's Advocate discussion as makes the brain work, broadens horizons, etc. I also love when things are challenged by valid antenna facts. I know you are much more into "gizmo" antenna than I, but you know a lot of antenna theory and make talking about them fun. What bugs me is when all I am quoted is look at my picture and I live x miles away, which means nothing except it works for them.

Well both the 751 and the 7000 have the same boom, so that is equal. And yes the 751 has an additional high band director element. But some say cramming in a director on an already crowded boom is diminishing return and might even hurt the gain but help some on beam width.

I expanded the PDF on the 7000R and it appears all elements that look high band (2 directors and a reflector) are passive. On VHF it appears the longer low band looking elements are driven. They may be playing off a third harmonic or just like the old 4228 resonated on VHF because the screen did and it was passive. Coupling into a driven element can be odd and not apparent.

So going on that, the 7000R might have more than 3 elements on high band with parts of the longer two adding up to be close to the equivalent of another element for high band.

I can't get away from the fact the YA-6713 is 50 inches long. It is fairly simple to analyze as it has 3 directors and a reflector passive. Then 2 driven elements that on any the ends of the band only one works and toward the middle both work. It has about 7 db gain, that matches all my history of building and playing this wide spaced yagis on 2 meters and commercial linking.

Devils advocate the other way, I still say the 751 only has about 5 db of gain, maybe a little more but just adding a director to the same boom as a 700R won't give 2 more db, and probably .5 at best.

Which would I bet works better on high band? RCA ANT751 would get my money. But can you tell it inside on the CECB? Or more so I would say you would need a good test range to see the clear winner on paper, though we both know the 751 should win.
 

EscapeVelocity

Moderator, , Webmaster of EV's Antenna Blog
#13
If you look at the RCA ANT751 you will see that the 2 (slightly different width) VHF High elements on the top of the boom are fed in a log-yagi configuration.

That is 2, not only driven elements but interconnected in a log periodic formulation which also increases gain.

From what I can tell ofthe Winegard 7000R, it has at least one driven element the 100" wingspan on the back, and perhaps the second longest element in front of it on the top of the boom as well.

I have the RCA ANT751 right here with me.

Back elements are 34" total and 16" each plus gap.
Next forward driven log yagi element is 29" total and 14" each side plus gap.

The directors in front of that on the bottom of the boom are...

26" (rear) adn 25" (front) and are not electrically seperated from the boom.


Everything from the 2 directors behind the UHF folded dipole forward looks the same on these antennas.
 

EscapeVelocity

Moderator, , Webmaster of EV's Antenna Blog
#14
I love Devil's Advocate discussion as makes the brain work, broadens horizons, etc. I also love when things are challenged by valid antenna facts. I know you are much more into "gizmo" antenna than I, but you know a lot of antenna theory and make talking about them fun. What bugs me is when all I am quoted is look at my picture and I live x miles away, which means nothing except it works for them.
Yeah!

I couldnt get anything but sneers out of knowledgable people over at the AVSforum about the Chinese Rotor antennas. The conventional wisdom crowd doesnt really like the indoor antenna, the non traditional antenna or even the more traditional antenna designs that are smaller, for that matter.

I even had to work on you to give me some feedback in the Chinese antanna thread. :)
 

Piggie

Super Moderator
#15
Yeah!

I couldnt get anything but sneers out of knowledgable people over at the AVSforum about the Chinese Rotor antennas. The conventional wisdom crowd doesnt really like the indoor antenna, the non traditional antenna or even the more traditional antenna designs that are smaller, for that matter.

I even had to work on you to give me some feedback in the Chinese antanna thread. :)
I admit I am a old school, wants a much aluminum in the sky kinda guy!

You did have to work on me to give more than a ho hum on Chinese things.

But you challenged me at my core understanding of antennas. How could I ignore that!

I know years ago when I found AVS, I read and reread your indoor review many times and learned a lot.

It's a real pleasure we have captured your interest on this forum and have you as an active member!
 

EscapeVelocity

Moderator, , Webmaster of EV's Antenna Blog
#16
Well, I readily acknowledge there are far more knowledgable people than me when it comes to antenna theory and design, and I like learning from them (and I mean lots-ham radio folks especially).

I bow to your superior antenna knowledge.

That being said, I have much more hands on experience with indoor tv antennas than just about anybody around.
 

Piggie

Super Moderator
#17
Well, I readily acknowledge there are far more knowledgable people than me when it comes to antenna theory and design, and I like learning from them (and I mean lots-ham radio folks especially).

I bow to your superior antenna knowledge.

That being said, I have much more hands on experience with indoor tv antennas than just about anybody around.
Funny how we all know lots of people smarter than us. I read the stuff in UHF antenna thread and admire the knowledge and keep learning. Of all the hard core antenna types I rate myself in the B+ category with a lot of people above me on the ladder.

I could not sit down and design a TV antenna, but I can guess really close what someone else was doing when they built it. I have all my life in many jobs been in some no man's land between being a technician and engineer.

So save your bows to those smarter than me whose material I have read all my life and learned.

The older ham radio folks. I am finding fewer and fewer people in that hobby that lead the edge any more. Actually for quite some time. I haven't been on the air since the very early 90's. As myself and other's tried to get ham radio into the digital world back then, we hit brick walls of older timers wanting to do the old way only. I see from reading my current QSTs little has changed. A lot of the death sentence for hams to go any farther in digital also was loosing 220 to 222 MHz. We had proposals to run very wide stuff in there to get speeds up. We already had enough bandwidth there for 9600 baud and had started building it out when we lost the bottom of that band. We had plans to apply for STAs to use wider signals to at least get up to 28kbaud similar to a telephone modem. We needed that band because no one used it, and we could run wide signals there. Plus there were few people into the high speed stuff so we needed something that had 100 mile range to move data even if only at night. We had plans for using microwaves for much much faster data as it caught on and it was possible to take many more shorter hops between people's houses, etc.

It all died. Digital is still used mainly for DX spotting and passing Health and Welfare traffic, and it's state of the art is stuck circa 1990.

The new thing is memorize the test, go buy a Japanese radio and antenna and call that seat of the pants.

I have seriously though of putting back up only dipole and simple wire antennas and polishing my CW back to a decent speed. Many of the experimenters now "hide" down in the CW parts of the band.

Another place that actually seems more interesting to me is there are also experimenters in the VHF and UHF band running not FM, handhelds or repeaters and phone patches, but Single Side Band and CW running antennas very similar to they type we discuss here. I did it in the past and keep swearing I should buy another 2 meter SSB rig to get started again. It's pretty amazing how far you can talk on 10 to 25 watts PEP with a long boom yagi on 144 MHz just 20 ft up. Here is FL nightly distance is 100 miles plus. 144MHz is wild as even E-skip gets up that high one or twice a year if you are lucky enough to be on the band. I have worked people out 900 miles on 146 MHz, so I know it's possible. Oh the people that play with satellites tend to be a unique crowd as well, and I tried it but it wasn't my style.

====

Now that said!! Yes, everywhere I have looked on the net, EV is the man with the most experience on indoor antlers! You are also the man to take on the new Chinese beams, because I really think they are the new indoor antennas that may very well even solve some of the "I live in an apartment and can't get no VHF blues" crowd. Seriously....
 

EscapeVelocity

Moderator, , Webmaster of EV's Antenna Blog
#18
I mostly followed along with you there......Im applying for my ham license, and have memorized the test and will soon be getting a Japanese rig.

LOL!

I only have a RS DX-390 (or something) SW radio now.


Yes, everywhere I have looked on the net, EV is the man
It just goes to show you think small and specialize in areas no one give a fig about! You too can be a guru.
 

Piggie

Super Moderator
#19
I mostly followed along with you there......Im applying for my ham license, and have memorized the test and will soon be getting a Japanese rig.

LOL!

I only have a RS DX-390 (or something) SW radio now.




It just goes to show you think small and specialize in areas no one give a fig about! You too can be a guru.
I know it's more expensive but consider SSB on VHF instead of FM, at least from the house. FM is fun driving to work or around town and can actually come in handy if you have a problem (cell phones not withstanding).

But I really think anyone that like TV antennas and propagation would clone right into being a VHF/UHF SSB nut. You might even get interested in CW as it can give you 200 mile range on a 2 wavelength yagi and 10 watts RMS. Remember the IF's are very narrow even on SSB at 2.1 KHz so say 25 watts PEP travels a long way. 100 watt amps are not that expensive either if you want to push it out there farther when the band isn't open.

But I forgot where you live and might not have the nightly band opening we have in Florida.
 

jimw

DTVUSA Rookie
#20
I tested the ant751 in south Florida(read waaaay flat). I am 47 miles north of 2 hi vhf stations on adjacent channels, 12 and 13. They both are the same distance and 182 degrees from me. The station on 13 for whatever reason has always been the most difficult to recieve. I get them both great using the ant751 sitting on the top of a plastic topped 6 ft stepladder. Got a solid signal for several hours over 2 days. With that setup, I get all the networks, etc. 23 channels. Using rabbitears with a uhf loop, I got 20 channels outside using the ladder, etc. The 2 hi vhf signals were missing using rabbitears.
 
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