Low VHF antenna designs
Greetings everyone.
Since it is near impossible to purchase a low VHF band specific antenna, It would be nice to have the information to build one. Personally, I'd prefer a Low Band VHF antenna that covers Rf 2-6. Currently, I've been using FM antennas to receive Rf 6 with fairly good results. I'm finding FM antennas harder and harder to find for purchase. Please include specific spacing, reflector, director measurements. Appreciate your help!! |
You're right Joe... Finding any commercially made L-VHF antennas has become nigh-on-impossible. I've just finished installing 4NEC2 antenna modeling software on my new computer so as I get back up to speed with it expect me to offer a few contributions to this thread. In the meantime, there are a few calculators available online.
Examples; https://www.changpuak.ch/electronics...enna_DL6WU.php https://www.changpuak.ch/electronics/Dipole_folded.php https://www.changpuak.ch/electronics...da_antenna.php http://www.vk5dj.com/yagi.html https://www.qsl.net/4nec2/ |
Really appreciate your information. I cannot help but
wonder if a low band VHF antenna, that covers Rf 2-6, would differ from the channel specific designs you provided???? |
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If you need even more bandwidth, the next step up would be a Log-Yagi which has log periodic active elements combined with parasitic elements. An example would be the VHF-High section of an RCA ANT751. https://i.imgur.com/0HMm9FY.jpg And finally, for the greatest bandwidth you would need a Log Periodic antenna design. Examples would be the VHF-High section of the Winegard HD7698P and the VHF-High/VHF-Low section of the Winegard HD-8200U. https://forum.tvfool.com/attachment....3&d=1565736363 https://forum.tvfool.com/attachment....2&d=1565726635 The small extensions that you see on some of the 8200 VHF elements allow those elements to function on 2-6 AND 7-13. |
Here is a file from holl_ands for a channel 3 to 5 Log-Yagi that has two active elements and a parasitic reflector and directors. Note that the gain curve is fairly flat across the design bandwidth, as opposed to a Yagi that has a gain curve that rises from the low end to the high end.
http://imageevent.com/holl_ands/logy...0elch35logyagi This is the Antennacraft Y-10-2-6 Log-Yagi. The design is deficient for channel 2. http://imageevent.com/holl_ands/logyagi/y1026 |
I really appreciate all your suggestions and information.
Toying with the idea of producing antennas currently either hard or impossible to find new. There are several places in Phoenix that could make the components and a place here in Prescott that could assemble the components on the cheap. I just don't know if I want to undertake such an ambitious project at this time in my life..... |
Just the design and testing phase would be time consuming.
After you get all that nailed the rest is just building and shipping. Except for the after the sale customer service call headaches of course. lol |
Here is another online calculator, for designing a Log-Periodic-Dipole-Array.
https://hamwaves.com/lpda/en/index.html |
As always, there is good information here. Recently, a station that used to broadcast on RF 46 switched to RF 6 and now I find myself trying to figure out what to do. I've built probably close to a dozen or so UHF antennas, from M4's to a DBGH (currently on the house), but I've yet to try and tackle a L-VHF. Mainly because there has never been a need until now. I knew the station was going to make the switch, but I didn't care when it was only a religious station. But about a month before they switched, they added ION and Bounce to their line up and now I want to get it back. Has anyone as of yet tackled one of these monsters? If so, how did it work out for you?
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I have two commercially produced moderate to compact size antennas with L-VHF extensions here in SOCAL LA/OC. The RCA ANT3037XR (actually built by Winegard for RCA) and the Winegard HD7000R, one each for my two Samsungs, 2013 40" and 2017 32". There are several low powered stations on Mt. Wilson above LA, broadcasting on the L-VHF frequency right now and one full powered station, KWHY 22 (display, physical 4) at 35kW power (yes, that's right!) which carries Retro TV on KBEH 63-3. Since part of my TV viewing includes Retro programming, that was why I put up those antennas. Plus, there might be possibilities of other stations moving to L-VHF in the future or increasing their signal. Nothing firm at the moment, just chatter from the NET. I'm in a strong to moderate signal area, 35 miles south of Mt. Wilson, so I get excellent (100%) reception from KBEH which transmits off the KWHY 22 tower. So, yeah it's worked out well for me. I hope this helps answer your query. I know you mentioned you build your own TV antennas, so I can't really help you with that issue if that's what you were looking for. Anyway, all the best..... |
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Or if you need more gain, try a 3 element Yagi antenna. I expect you would get about 6 dB gain out of a 3 element Yagi as compared to a dipole. You can use this calculator for the measurements (note: measurements in meters) https://www.rfwireless-world.com/cal...alculator.html Or this one has measurements in feet and inches plus measurements for additional director elements if needed: http://www.wc7i.com/yagi_calculator.htm |
Thank you for the information guys. I do want to try and build one to see if I can pull it off. But my plans may be on hold until the spring. I am roughly 30 miles from the towers of the Altoona antenna farm in PA, but due to the mountains, all my signals are 2 edge. I'll give it a shot as soon as I can. Thank you again.
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Hi eggman.
What material would you like to use to build your channel 6 yagi? I did a design that uses 3/4” hardline from a CATV scrap pile for the elements. I’ll send you the dimensions if you have access to that material. I have also built a bidirectional V beam from simple wire. A full rhombic is another option. In hilly areas such as yours the location of the antenna makes a significant difference. I have seen antennas in the side yard on a 10’ pole work better than the roof. Goo goo gachoo. |
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https://www.rabbitears.info/repackch...=&lss=&status= https://www.rabbitears.info/market.p...=13929#station The strength of the WKBS signal at your location will determine what type of Channel 6 antenna you will need. On the plus side, VHF signals can make it over rough terrain better than UHF signals. On the minus side, the noise level from electrical interference is high on VHF-Low, requiring a stronger signal with sufficient SNR above the noise. Tower Guy is correct; try different locations for your DIY CH 6 antenna. I made some measurements of electrical noise on all three TV bands; it was highest on VHF-Low: https://i.imgur.com/aAU1EBY.png This is what the noise looks like on VHF-Low at my location. The signal had to be at least -8 dBmV (-57 dBm), which is a fairly strong OTA signal equivalent to 34 dB NM on a TVFool report, for reliable reception: https://i.imgur.com/DwQNtji.jpg Signal diagnostics: https://i.imgur.com/eiRXzRu.jpg Channel 3 folded dipole antenna: https://i.imgur.com/6qYVZsO.jpg |
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cambria county on AVS extended the rear elements on his RCA ANT751 to be able to receive WQED from Pittsburgh. It moved from 13 to 4.
https://www.avsforum.com/forum/45-lo...l#post58584134 Quote:
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Those elements are a little too long for channel 6; should be more like 33 or 34 inches on each side. This is what the Winegard HD7000R looks like with the VHF-Low extensions added: https://forum.tvfool.com/attachment....5&d=1572964727 https://forum.tvfool.com/attachment....6&d=1572966677 |
Another option would be to use an FM antenna, especially for
Rf 6. You cannot beat the price..... and it works very well for a 500 watt, Rf 6, translator at 20 miles away. https://www.newark.com/stellar-labs/...ING-Electrical |
That's a good idea.
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http://www.tvfool.com/?option=com_wr...90386ebd6201d7
My TVFool report. It's not very accurate as these are the old listings and the channel I'm trying to get isn't even on there BEFORE the switch. Actually, my NBC station used to come in on RF 34 which isn't on the report either. They switched to RF 35 around the same time and signal now cuts in and out. Maybe an LTE filter is needed? I don't know. I haven't had a chance to try anything yet. Hopefully over the weekend. I apologize as I just now have only had a chance to check the thread and am getting ready to run out the door to work. I'll look over everything everyone has posted ASAP. Thank you all. |
Also, yes, it's WKBS.
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https://forum.tvfool.com/attachment....7&d=1573067494 This is a report from rabbitears.info which should have a more accurate list of channels: https://www.rabbitears.info/searchma...study_id=25786 You can do your own report here; I used coordinates for the one I did: https://www.rabbitears.info/searchmap.php This is an extract from your rabbitears.info report: https://forum.tvfool.com/attachment....8&d=1573068929 I guess I don't need to tell you that your location is not idea for OTA reception. Quote:
https://www.rabbitears.info/tvq.php?...ms&facid=73120 The strongest one listed on your report is on channel 22, but it is only running 7.5 kW ERP. WJAC on RF35 is further down on the list and over 50 miles away. It is running 1000 kW. Both signals are blocked by terrain. Click on the transmitter distance in the report for each channel to see the terrain profile. https://forum.tvfool.com/attachment....9&d=1573076090 https://forum.tvfool.com/attachment....0&d=1573076116 A lot of hills in the signal path that block the direct signal. |
I had wondered about an FM antenna. Which sucks, because I gave one away about a year and a half ago. And I really like the idea of using the extensions on a smaller antenna, but, most likely I'm going to try the dipole outside over the weekend first. I have a pair of rabbit ears that I measured out to 2.75 feet on each side and took it to the attic late last night. When I scanned channels 2-13, it stops for about 20 seconds about halfway through. So, I'm guessing it's trying to lock onto something but there just isn't quite enough there. I know, it's in the attic. There is a spot outside on my property that I used to be able to get it before but it's at ground level. Also, I remembered I had collected and kept some elements off of an old full range antenna someone was throwing out so I will probably try and build a yagi (my first one) using those. Also, all the pics REALLY help! Thank you again.
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https://www.rabbitears.info/searchmap.php |
I did this 4 element design for channel 6 using EZ-NEC:
3/8" diameter elements. Reflector length 71.6" Driven length 72.4" Director #1 61.2" Director #2 57" spacing Ref-Driven 22.8" Driven-D1 3.1" D1-D2 20.1" The feed is direct using 75 ohm coax; no balun. If you want to play download this: https://www.eznec.com/demoinfo.htm |
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Thank you for the link. I didn't know he had a demo. |
My RabbitFool report, err, Rabbitears report:
https://www.rabbitears.info/searchma...study_id=26219 |
Thank you Tower Guy for the dimensions on the Yagi. One question on it is though, what is the spacing on the feedpoint for the driven element? Though I've tried to teach myself how to use them in the past, I've never been good with NEC programs and rely heavily on people posting dimensions (or pictures with dimensions).
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The driven element is fed in the center.
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https://www.rabbitears.info/searchma...study_id=25786 |
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You may use any reasonable gap that is convenient.
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Well, I tried a pair of rabbit ears measured out for RF 6 with no luck. The small TV I carried up onto my shed roof again tries to lock on to something, but can't quite get it. Without the rabbit ears, my channel scan zooms right through with no stalls. For kicks I hooked up one of those RCA preamps just to try it and still nothing. I wimped out and ordered a FM yagi because it will get here before I get a chance to build anything. My wife is gonna kill me when she finds I bought yet another antenna as I ran into what I thought was a sweet deal at Ollie's (good stuff cheap!) on some Antennas Direct DB8 antennas for 50$ a piece. So I bought 3 of them to play with and use for future installs. Guess I should get used to sleeping on the couch.
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"A wife should let her husband have his hobbies so that he doesn't notice she is running his life." |
Success! Well, sort of. My FM antenna was delivered today so even though it was pretty cold here, I had to go out and play with it. Something is up with my rooftop antenna setup, so I installed a temporary setup behind my shed where I can just snag my local stations around the neighbor's house. It's not ideal, but it'll get me through the winter. I had to get it up about 15' to 20' up, but the FM antenna will lock onto RF 6, though HEAVILY pixelated and pretty much unwatchable. BUT it's a step forward. I ran it through the RCA PRAMP1R on the VHF input. I want to try just using a straight cord to the TV in the next couple of days and see how that works. Would've done it today, but I lost daylight too quickly. I should also mention that this is being sent to 4 different TV's. Anyways, I bought this antenna:
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1 |
I don't know of any Low-VHF only antennas, although I understand that the larger ones (usually made by Channel Master, R.C.A., and Winegard) have long dipoles near their ends that are designed to receive low-VHF channels. Rabbit ears still seem to be readily available, although I assume indoor reception would be a problem regarding the effects of impulse noise on the low-VHF signals since they would already be weakened by the exterior walls.
I'm also not sure if there are any ways to improve gain. I don't imagine that the corner reflectors seen on U.H.F. antennas would be practical as they would be rather large and cumbersome, so I would assume the only way to improve gain for the low-VHF channels would be to add more parasitic elements/directors. I hope this helps. |
So, I've decided to start gathering materials needed for a 5 element Yagi found on the Yagi calculator page that GroundUrMast posted earlier. I decided to go with the folded dipole calculator as well. All to the tune of 86 MHz. Now this causes me to ask a question or two. The main question is, how important is it that I stick to the rod diameter for the folded dipole? It's calling for a diameter just a hair under 1/2" and I was wondering if 3/8 would work just as well? I ask because benders can get a little pricey. Also, I've seen folded dipoles now with both a curve on the end and squared ends. So my next question is, could I just keep the same distances (with the exception of the curves) and simply use 90 degree elbows and square it off? Or, in my ignorance, am I missing something here? Thank you in advance for any wisdom you all can bestow upon me.
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As far as the folded dipole driven element, from a practical perspective I suspect that either curved ends or squared ends will work fine as long as you keep the relative dimensions the same. Another thought to keep in mind is that an antenna is usually more broad banded when it is constructed of larger diameter elements. There are many, many variables in yagi antenna design. Someone with antenna modeling software could probably give you some more specific answers than my general ramblings and observations. |
I agree with Tim on the general answers and that precise answers would require antenna modeling.
Channel 6 is 82 to 88 MHz, so center freq would be 85 MHz. |
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