Last year we had some roof work done and I told the guys to take down the large TV antenna that hadn't been connected in years and was unsightly.  I hacked off and saved the UHF section from it in case I ever wanted to use it for OTA digital reception.  It's a couple of feet long, a sort of traditional "Yagi" style flat section with about a dozen short aluminum rods, and two reflectors at rear with similar configuration that fold out at an angle above and below the main mounting body, kind of like the first image below.

Well, the time to give this salvaged rig a try has come, as the stormy weather is making reception with bow tie/rabbit ears annoying.  Now that I've examined the section I saved, I see no way that the two wingnut terminals where leads would be connected would in turn provide a connection to the remaining elements.  The rods that connected these wingnut terminals to various parts of the entire array had to be cut as part of the salvage process, and with the VHF section gone, there don't appear to be any points left to connect them to.  I can't see how the connection point as it stands now would employ any elements other than the two short aluminum tubes extending from either side of its plastic block.

Is there any way to rectify this?  I've checked on line and have seen some examples of building an indoor UHF antenna out of 8 V-shaped coat hanger sections (see image below), which is nothing like what I'm dealing with, but the one feature they do have is a pair of connecting rods that crisscross, each of which shares a fastener with 4 the V-shaped components.  From what I've read, this configuration is important, so I'm wondering how I'd apply that to what I'm working with. 

Or should I just forget about it and buy something?

Thanks Paulo,

I guess the "active elements" of my antenna went to the scrap heap.  I might be able to recreate one "half-wave dipole" pair at the rear of the section I have left. 

All this time I thought the short "director" elements at the front end were for UHF, so that's why I saved that portion.  Now I'm understanding that it's the wide-span dipoles that pull in the signals, whether VHF or UHF.  

Since digital signals in my area are far more easily received than analog used to be, adding that one pair might be enough to improve reception over what I'm getting with the small indoor bow tie I'm currently using.  It's worth a try.

Eric, thanks for the suggestion but I'm looking for something much smaller.  As stated above, the indoor bow tie is pulling in nearly every station available (the majority of transmitters are 45 miles away or less), but sometimes weather conditions cause pixelation, momentary loss of sound, or loss of signal altogether.  All I need is a boost in reception that will eliminate these problems.

Phil, I'll try to get a picture posted here tomorrow.

I've hatched a dipole plan that might improve things.  Tomorrow may be a good day to try it, since it's supposed to be cloudy with possible showers, which presents perfect conditions to see if it will work.  If not, then I may make myself one of those coat hanger rigs.

Here's what I'm working with.  The center section (the directors, I presume) looks to be slightly under 3' long. 

The connecting block for the dipole is just inside the V-shaped reflector(s).  From tip to tip it measures just under 12".   Wing nuts are on the bottom.   I had to JB Weld it because it had broken in half when the whole rig was tossed off the roof and onto the driveway.  I don't know what the other orange piece with U-shaped rod was for.   It's riveted so wasn't intended for any connective purpose.  I removed the cut rods from the connector block since they no longer served a purpose.  Most assuredly, they connected to a section of the longer elements behind what remains.  I feel as though that missing connection to the rear section is what's diminishing this remnant's ability to pull in signals.

Thanks for the excellent explanations on what I'm dealing with.  If I'm understanding things correctly, just that little dipole is pulling in the signal and the rest of the assembly is only there to help zero in on it.  That's kind of amazing.

I gave the antenna a trial run, and reception was excellent on what had been weak and problematic channels, but the NBC affiliate rendered a "no signal" display.  I tried aiming the antenna about 30 degrees in either direction from what I know was best when this rig was intact.  Still "no signal."  This is a deal-breaker, since I'd rather get NBC than more Asian language dramas and game shows.

I never would have believed that a little bow tie could pull signals indoors better than a rooftop unit.

Phil, I may take a shot at one of those 4-bay antennas.  That may be all I need.

Phil, I've been wondering about whether the NBC channel could be VHF.  In the analog days it was channel 11 but these days I don't know what it really is.  It has always been an issue to receive 11's signal because the transmitter was south of town instead of north like all the other local stations.  When it became the NBC affiliate, in order to serve the entire greater Bay Area, they moved their transmitter and changed media markets from Monterey to San Francisco, but they didn't move to where the bulk of local stations transmit from.  Still, it's in the general area and shouldn't require a different aim than for the other channels.  I'm pretty sure their tower is on the same hill as channel 2, which comes through fine most of the time.

Do you think I could use some 12 gauge romex wire for the 4-bay antenna?   I've also contemplated harvesting dipoles from a set of rabbit ears and attaching them to the hairpin block by drilling holes for a couple of screws, and then connecting the rabbit ear dipole to the UHF dipole with some wire.  I know spacing is key, so am not sure if fastening the rabbit ear dipole on the hairpin block would be the proper placement.

Last night, with mostly cloudy skies, I tweaked the bow tie arrangement I have the TV hooked up to, and all stations I care about came through.  It's unsightly, but I might not be able to do much better.  See attached picture, and yes, looping the twin lead around that one side of the bow tie makes a huge difference.  The TV is a 19" Magnavox with built-in DVD and VHS players.  It still delivers a sharp, crisp picture with perfect color.

Thanks Phil.  I did learn that KNTV uses a VHF frequency.   I think my rabbit ear dipole plan is worth a try. 

Also, back when KNTV first began broadcasting in the '50s, because their transmitter was in the opposite direction from where area antennas were aimed, they distributed free small rooftop dipoles that could be spliced into the existing antenna system and aimed toward their transmitter.  I still have one, so the other option is to hook it onto the UHF antenna's terminals with some twin lead.   That would eliminate the need to create a fastening system for the rabbit ear dipoles.

I'll post a picture of the antenna tomorrow for your review.

Here's the KNTV antenna.  If it helps with reception on that station, it will once again serve its original purpose some 60 years after it was issued.  Due to one terminal screw having snapped off many years ago, the connection block can't be used as a splitter anymore, but the pair of terminals marked "SET" is all I need. 

It's bordering on a Rube Goldberg solution, but if it works, that's all I care about.  I'll test today and report back with results.

First I tried using just the KNTV antenna.  Not all stations could be received, so I hooked up the UHF antenna as well.  Now I receive every station without interference except KGO 7, which is still VHF.  No matter how I aim the KNTV portion of this arrangement, there's an occasional blip in sound or momentary pixelation on KGO.  Considering the fact that it's clear and sunny today, I expect issues with KGO on rainy or otherwise overcast days, which include summer when fog can often shroud the transmitter tower in SF where most stations' signals originate, even though it's sunny in the rest of the greater Bay Area.

Over all, it's an improvement over the set-top antenna.  KGO 7 doesn't come in that much better, but other stations that would invariably have issues are now steady. 

I don't know if constructing my own 4-bay antenna would improve things any further.  Besides, right now I have the KNTV antenna aimed slightly differently from the UHF, and this wouldn't be possible with the 4-bay arrangement.

I'm not making any of this permanent until I've tested reception under various weather conditions.   The ability to remove the unsightly set-top rigging would be a plus if all goes well.

Thanks Phil -- your information above reveals that I have the KNTV antenna aimed backwards.  I'll turn it around and see what happens.  Just for the record, KGO has been on for the past three hours and there hasn't been a single issue.  I would think that turning the KNTV antenna around could only improve on the progress I've made.

I'll look into making a folded dipole for the UHF remnant.  I'm not sure where I'd find aluminum tubing, or whether using a tube bender would work to "fold" one.

I turned the KNTV antenna around so everything is now properly aimed.  I'm receiving all available channels with absolutely ZERO interference!   It seems odd not to be dealing with hiccups and temporary loss of sound.  

A scan performed by the digital tuner box picked up one additional channel that broadcasts on VHF from about 20 miles south of here, so am assuming the VHF antenna gets credit for that one.  It offers nine appearances, each of which are religious in nature, so I manually deleted all of them.  This is why my excursions to Reno are few and far between.

The real test comes this weekend when some rain is expected.  I don't think I can do any better with what I have, so if the rain and/or related cloud deck cause trouble, that will suggest the need to upgrade.

Rich, I checked around on line for a list of OTA channels to see if I was pulling in everything within reason, and found the rundown in the link provided.   It appears north bay channels primarily offer duplicate programming of what's provided on stations in closer proximity that I can easily receive.

The only station I'd like to receive but has its transmitter to the south of here is KSBW 8 out of Salinas/Monterey.  They cover the Santa Cruz weather forecast in more detail than SF Bay Area stations do, and have a no-nonsense/no hype meteorologist who is also a licensed pilot and puts a practical spin on things.

Phil, I think your post directly above explains why KGO has been more problematic than other stations. 

Today we have some high clouds in advance of a weak weather system due in here tomorrow, and KGO is displaying slight, infrequent choppiness, mainly momentary loss of sound.  It's not horrible, but per the link I posted further up, KGO broadcasts on low band VHF from the tower in SF, and on UHF from a transmitter closer to me, but the nearby tower is NE of here instead of NW, which is the direction I have the UHF antenna aimed.

Apparently KGO's VHF signal is too weak from the SF location so I think what I'm getting is coming from the nearby UHF tower.   I've aimed the VHF antenna to the NE, but realize it's not designed to receive UHF, and am not seeing much improvement.  I think KGO will remain an issue except in fair weather, at least until I make a decision on upgrading.  Maybe I need to revisit the rabbit ear dipole addition on the UHF antenna's hairpin block, or just upgrade to a modern rig that will receive both VHF and UHF.

The reason I think I'm receiving the KGO signal over UHF is because when I ran a new channel scan on the converter box, I ended up with duplicates of channel 2, which has a similar arrangement over separate transmitters in the same locations as KGO, but channel 2 broadcasts over UHF from both.   So far, appearances of channel 2 from both towers are coming across fine. 

It seems strange when a little college station like KCSM/60 with presumably weaker signal can be received more reliably than a network affiliate like KGO/7, even though they're both broadcasting from the same tower.  I've decided I can't improve reception on KGO with my current system, but it's not bad enough to make me go out and buy a new antenna.  We'll see what happens when SF's summer fog season kicks in.

Also, I just heard that negotiations are in progress to sell KCSM, so we can say goodbye to the only PBS alternative to the bloated KQED empire in this market.  Prepare for foreign language, shopping, infomercial or religious broadcasts on channel 60 down the road.

Eddie, thanks for confirming that KGO has always been quirky.  I sort of recall it being ghosty in the olden days when other network affiliates were fine, even though most were broadcasting from the same general area before Sutro tower went up.  The other station that tended to come through less than perfectly was KTVU channel 2.  I remember on our 1951 Capehart, 2 was always a bit snowy.  It improved when we got our '62 Airline, but with rabbit ears on other sets, 2 was more compromised, and 7 (KGO) always needed adjustments.

I read many, many years ago that the reason so many ABC stations are found on channel 7 is because there was a rumor or concern in the early days of TV (cold war era?) that the FCC or whatever agency might claim the use of the lower VHF frequencies for government use, so by snapping up all of the channel 7 frequencies, ABC would essentially be the first viewable channel on the dial.  In the days before remote control, that was a strategic position.   I don't know if there's any truth to this legend, since ABC was late to the TV party behind NBC and CBS anyway.   In the end, ABC landed downstream from NBC and CBS, which in major markets can usually be found somewhere in the range of channels 2 through 5. 

Rich, it gets worse re: Channel 60.  In that same story I mentioned above, it was reported that the jazz station KCSM (91.1 FM or 60.3 on TV) has cut staff and live programming and is now running some shows prerecorded out of Chicago.  A source at KCSM didn't exactly confirm or deny rumors that the radio station is up for sale (presumably ours is a hot market for radio and there's no shortage of potential buyers), so we might be saying goodbye to jazz in the Bay Area for good this time, as there probably isn't anyone willing to step in like KCSM did to fill the void left when KJAZ was sold quite a few years ago.