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DIY antenna designs for attic?

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km1125
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Joined: Thu Mar 14, 2019 3:09 pm

Re: DIY antenna designs for attic?

Post by km1125 » Tue Apr 21, 2020 3:51 pm

So I whipped up another folded dipole centered on Ch 12 to use for the Toledo stations but it is nowhere near as good in performance as the larger antenna for the Detroit VHF stations. I could not pick up anything with it on Saturday and got some marginal signal on Sunday.

I used the "signal strength" function on the TV to try and tune a reflector (just a section of copper pipe) behind the dipole and found about 20" spacing to be the best, but it wasn't much of an improvement. There was some directionality to it but I couldn't measure it because as soon as I moved the dipole I lost all the signal. I ran out of time before I could rig up a preamp to see if that would help



CK-722
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Re: DIY antenna designs for attic?

Post by CK-722 » Tue Apr 21, 2020 5:11 pm

I just called Winegard. The person who answered said there were no new products being developed at this time for the repacked channels 14-36 and for Low VHF at least as an after thought.

Apparenowntly we're on our own.


Is THAT where they got the idea for the 486-SX?

Same (x, y, z), different (t)

Your bullet missed my trial balloon.

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k8jd
Posts: 358
Joined: Fri Jun 28, 2013 3:35 pm
Location: Commerce, MI

Re: DIY antenna designs for attic?

Post by k8jd » Wed Apr 22, 2020 3:59 pm

A folded dipole shold work fine for local signals .
I wish I could survey your attic to see if there is HVAC gear, electrical wiring or metal roofing above or around the antenna site. That antenna is no match for multi element Yagis or LPDA ;systems , but they have to be aimed right at the transmitting antenna towers.



km1125
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Re: DIY antenna designs for attic?

Post by km1125 » Wed Apr 22, 2020 5:34 pm

Nothing really in the attics except for a couple power lines up to the lights. No metal roofing, although there's probably some aluminum drip edge at the bottom row of shingles and then there's the normal aluminum gutters.

Right now in the garage attic I have an old simple set of rabbit ears from a tv, extended horizontally as far as they would go (probably 4' or so) and that's what's picking up 11 and 13 in Toledo. That's what I'm trying to replace with the new folded dipole that I built cut to Ch 12. It currently is in the 2nd floor about the same vertical height as the garage attic antenna but eventually I'll add another 8' of height when I move it to the house attic. Just have it in the 2nd floor so I can see the TV when I'm testing stuff (like a director or reflector for it)



km1125
Posts: 1463
Joined: Thu Mar 14, 2019 3:09 pm

Re: DIY antenna designs for attic?

Post by km1125 » Thu Apr 23, 2020 9:21 am

CK-722 wrote:
Fri Apr 17, 2020 11:57 am
If you have an FM BC receiver with a fairly detailed signal meter in terms of LEDs, or digital like the Tecsuns, you could experiment with an FM dipole and reflector.
....
Silly me!! After reading that suggestion again I was thinking of different things I could use, and realized I have an old "Visual Field Strength Meter (Texscan VSM-1) sitting in the basement. I fired it up the other day and it still works! It's got to be at least 40 years old. The battery is no longer good (no surprise there) but I do have the battery charger/eliminator and it works good on that. It only goes up to 350 MHz, so it's useless on any of the UHF stuff, but for VHF it is good to go. Probably still reasonably accurate in an actual measurement for a CW or FM broadcast signal, but I can see the 8VSB signals on it too, just not measure them with any accuracy.

Just playing with it yesterday I connected it to my shorter folded dipole and can see a very strong signal on RF 7, weaker RF 3
, really weak RF 9 and just barely discernible RF 11 and RF 13, when swinging it around to the various stations. I'm going to do some comparisons with readings on it relative to the signal readings on the TV so I can determine how much of a reading on the meter is required to get a decent signal on the TV.

Thanks for the suggestion! It got me thinking!

If you're curious... here's a VSM-1A (that was good up to 450MHz):
https://www.youtube.com/watch?v=j1dYq_JyNvw



k8jd
Posts: 358
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Location: Commerce, MI

Re: DIY antenna designs for attic?

Post by k8jd » Thu Apr 23, 2020 1:08 pm

[quote
....
[/quote]

Silly me!! After reading that suggestion again I was thinking of different things I could use, and realized I have an old "Visual Field Strength Meter (Texscan VSM-1) sitting in the basement. I fired it up the other day and it still works! It's got to be at least 40 years old. The battery is no longer good (no surprise there) but I do have the battery charger/eliminator and it works good on that. It only goes up to 350 MHz,

If you're curious... here's a VSM-1A (that was good up to 450MHz):
https://www.youtube.com/watch?v=j1dYq_JyNvw
[/quote]
that piece of gear isusually called a :"Spectrum analyzer". Looks like a 4 figure priced toy ! We used those in the two way business, makes inter mod issues on sites easy to find ! .Our service monitors, sometimes had the Spectrum analyzer function on them.I could plug a 2 ft whip in , set the scan for 88-108 MHz and see all the FMBC stations within 40-50 miles on display!



k8jd
Posts: 358
Joined: Fri Jun 28, 2013 3:35 pm
Location: Commerce, MI

Re: DIY antenna designs for attic?

Post by k8jd » Thu Apr 23, 2020 1:11 pm

Sometimes a good clear attic is a place to set up antennas where there is some HOA restriction of any outdoor antennas.
I have contacted other radio Amaterus all over the country who are using vaious attic antenna systems. Coast to coast !



km1125
Posts: 1463
Joined: Thu Mar 14, 2019 3:09 pm

Re: DIY antenna designs for attic?

Post by km1125 » Thu Apr 23, 2020 1:24 pm

k8jd wrote:
Thu Apr 23, 2020 1:08 pm
that piece of gear isusually called a :"Spectrum analyzer". Looks like a 4 figure priced toy ! We used those in the two way business, makes inter mod issues on sites easy to find ! .Our service monitors, sometimes had the Spectrum analyzer function on them.I could plug a 2 ft whip in , set the scan for 88-108 MHz and see all the FMBC stations within 40-50 miles on display!
I think they would have been crucified back in the day if they called it a spectrum analyzer. It had no where near the capabilities or accuracy of an HP 8558 or Tek 7L12, but it was smaller, portable, and substantially cheaper.

Other than some markers, there is not much of a horizontal calibration on the unit, nor much for filtering or resolution bandwidth adjustments. You pretty much just get a display of carrier amplitudes. Was great for checking or setting the relative amplitude of the aural carrier to the video carrier on NTSC channels, especially when you had 30 or 40 packed on the screen. You could easily see one that was 'out of whack', which seemed to happen frequently on those old modulators.



CK-722
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Re: DIY antenna designs for attic?

Post by CK-722 » Thu Apr 23, 2020 10:40 pm

I wonder what audiophile uses.

Analog TV was it's own field strength meter. How else would you set your rotator for best reception? That's what I used to find the optimum spacing for a UHF Bowtie and Oven Rack for getting WEYI 25 analog 55 miles away across bad terrain. I also looked in the ARRL Publication "FM and Repeaters" that I bought at Shand's, where I got the idea to use an oven rack.


Is THAT where they got the idea for the 486-SX?

Same (x, y, z), different (t)

Your bullet missed my trial balloon.

RTN Price. Not guaranteed. As of 12:30, 157.71 Down 0.22.

Artificial Intelligence is a Child that needs a Parent to guide it through.

CK-722
Posts: 1284
Joined: Sun Dec 16, 2018 3:53 pm

Re: DIY antenna designs for attic?

Post by CK-722 » Fri Apr 24, 2020 2:52 am

I've been looking over some information on that Texscan Jerrold.

I see claims that it covers 4-450 to 4-1000 MHz. Perhaps different models, later covering the really high Cable Channels/OTA Channels.

So I guess it's not much help with AM BC.

You just don't know what shape of unit you're going to get buying one from eBay.

http://theoldcatvequipmentmuseum.org/180/187/index.html

From what I've heard, in the early days all the output channels were supposed to be equal, which also ensured that an OTA antenna would get a stronger signal than the cable on stronger signals. The output wasn't dramatically higher than a Grade B High VHF OTA signal. The fairly low but equal signals helped avoid adjacent channel interference and intermodulation. But the big selling point to cable operators was that if you put a splitter on it, it wouldn't have good results. This was before preamps and distribution amplifiers were commonly used in households.


Is THAT where they got the idea for the 486-SX?

Same (x, y, z), different (t)

Your bullet missed my trial balloon.

RTN Price. Not guaranteed. As of 12:30, 157.71 Down 0.22.

Artificial Intelligence is a Child that needs a Parent to guide it through.

km1125
Posts: 1463
Joined: Thu Mar 14, 2019 3:09 pm

Re: DIY antenna designs for attic?

Post by km1125 » Fri Apr 24, 2020 1:38 pm

CK-722 wrote:
Fri Apr 24, 2020 2:52 am
I see claims that it covers 4-450 to 4-1000 MHz. Perhaps different models, later covering the really high Cable Channels/OTA Channels.
Yes, the various models improved the bandwidth and features. The model I have is the older one, the VSM-1, which only covers up to 350MHz. The 1A went up to 450MHz and the later ones went up to 1000MHz. I did use a VSM-5 for a while and it is a very nice unit which includes some resolution filters and demods. That one you could legitimately call a low-end spectrum analyzer. Wish I had one of those. I also have an
CK-722 wrote:
Fri Apr 24, 2020 2:52 am
From what I've heard, in the early days all the output channels were supposed to be equal, which also ensured that an OTA antenna would get a stronger signal than the cable on stronger signals. The output wasn't dramatically higher than a Grade B High VHF OTA signal. The fairly low but equal signals helped avoid adjacent channel interference and intermodulation. But the big selling point to cable operators was that if you put a splitter on it, it wouldn't have good results. This was before preamps and distribution amplifiers were commonly used in households.
The channels definitely had to be run at nearly identical levels, otherwise the higher carriers would drive the distribution amps crazy with distortions, and the lower channels would suffer poor SNR as the baseline noise grew in the cascade of distribution amps.

In early systems they were really only designed for one TV per household, but by the late 70's/early 80's that had been modified to generally feed 4 TV sets as long as the house wasn't set too far away from the road where the distribution line was located. Anyone with an external antenna could have generally picked up the most local channels with a stronger signal and better SNR, but might also have to deal with a rotator. Cable eliminated those necessities and also brought more distant signals in.



km1125
Posts: 1463
Joined: Thu Mar 14, 2019 3:09 pm

Re: DIY antenna designs for attic?

Post by km1125 » Tue Nov 17, 2020 8:01 pm

Well I finally circled back to working on these antennas.

I played with the folded dipole I built and was testing it against a standard dipole and with and without a reflector element.

I setup another antenna a ways away and pumped in a really weak CW carrier on Ch 12. I compared my folded dipole to a manufactured dipole that was adjusted to 1/2 WL for Ch 12. I measured maybe a dB or two improvement, so I was comfortable I was in the ballpark. I then added a reflector element to my folded dipole. I tried a couple different things I had... one was just a length of angled aluminum and I also tried a section of ROMEX. I ended up using a section of 1/4" copper tubing (just something I had lying around). All three were similar in performance.

I compared signals again with the dipole and could see about a 3-4 dB improvement. I then rotated the folded dipole to see what kind of directionality I was getting. I lose about 12 dB when going off 45 degrees to either side and have about 6dB when looking at front-to-back. I'm now using this antenna to pick up WTOL and WTVG and it seems to be pretty good. I diplex it in with a UHF antenna and go through an amp to distribute to the house TVs. Once at the TV, I have about 15-20 dB of headroom before it starts breaking up.

I still have it in the garage attic. Eventually I'll move it up to the house attic which will add another 8' of AGL.

Here's a pic while I was testing:
Image



k8jd
Posts: 358
Joined: Fri Jun 28, 2013 3:35 pm
Location: Commerce, MI

Re: DIY antenna designs for attic?

Post by k8jd » Thu Nov 19, 2020 3:39 pm

FUN Project
I found a simple design page feturing UHF antennas, one is the single bow tie, This has a wider bandwidth than a folded dipole and may be easier to make.
I did not make notes of the freq range , but I am sure it will cover the UHF TV channels.
It's 16 1/2 inches end to end and the elements are flat triangles, far ends are 5 1/2 inches wide tapering to a point joined in center with coax connection there. I suggest a 4:1 balun to use less lossy 300 Ohm twin lead.
Simple to fabricate, half hour project if you have some small sheet metal pieces, or even aluminum foil and a plywood sheet to use as a mount .
Good if you are in the primary service area.



k8jd
Posts: 358
Joined: Fri Jun 28, 2013 3:35 pm
Location: Commerce, MI

Re: DIY antenna designs for attic?

Post by k8jd » Thu Nov 19, 2020 3:47 pm

CK-722 wrote:
Fri Apr 24, 2020 2:52 am
I've been looking over some information on that Texscan Jerrold.

I see claims that it covers 4-450 to 4-1000 MHz. Perhaps different models, later covering the really high Cable Channels/OTA Channels.

So I guess it's not much help with AM BC.

A halfwave dipole for 1000 kHz is 468 ft long.
A Quarterwve long end fed wire would be 238 ft long, but for a modern receiver , that's overkill :D :D



km1125
Posts: 1463
Joined: Thu Mar 14, 2019 3:09 pm

Re: DIY antenna designs for attic?

Post by km1125 » Tue Nov 24, 2020 2:18 pm

I finally got all the antennas moved up to the house attic. I have a VHF folded dipole (centered on RF12) pointed south diplexed in with a UHF pointed south, a VHF folded dipole (centered on RF3) pointed east diplexed in with a UHF pointed east and another UHF pointed west. All three antenna groups are then coupled together and fed into an amp before the downlead to the basement, where there's another amp prior to the splitter and distribution to the rest of the house.

While looking at signals I realized I was hammering the second amp, so I now have a 10dB attenuator on the input of that amp. That really cleaned up the noise floor as there was a lot of distortion there. Ideally, I'd like to replace the one amp in the attic with three preamps for each antenna group before they get mixed together, but I haven't found an inexpensive 10-12dB preamp yet for that application.

Here are some analyzer shots of all the signals I'm picking up. Seems like I'm getting something on RF8, but none of the sets detect that. Also, as noted in another thread, I am getting RF23 which should get me either WNWO or WUDT but neither come in, as I suspect there is substantial cochannel blocked them both.
VHF Group:
Image

UHF goup:
Image



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