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post #17821 of 17921 Old 08-19-2019, 12:01 PM
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Originally Posted by SFischer1 View Post
The VHF Lo/Hi antenna in the attic is tied up with string and is pointed in the correct direction towards Sutro in San Francisco. The 4-Bay Bowtie UHF antenna on a rotor also was silenced.

My furnace room now has a ceiling so going into the attic would be required, but at 76 I cannot go up into the attic any more. No floor so it was a balancing act with a miss-step punching a hole in the ceiling. My antenna installer I doubt would do any more work for me outside.

SHF
Well, it looks like you are left with trying some easy experiments yourself. If there is no metal in the walls, can you try an indoor folded dipole for CH 5? If the signal is strong, the only problem you might have is from electrical interference noise, which is very high on VHF-Low. The CH 5 signal would have to be at least 15 dB stronger than the noise to be received.


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post #17822 of 17921 Old 08-19-2019, 01:12 PM
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Originally Posted by rabbit73 View Post
Well, it looks like you are left with trying some easy experiments yourself. If there is no metal in the walls, can you try an indoor folded dipole for CH 5? If the signal is strong, the only problem you might have is from electrical interference noise, which is very high on VHF-Low. The CH 5 signal would have to be at least 15 dB stronger than the noise to be received.
...
I just remembered that the impossible RF 2 suddenly appeared on my backup HTPC about a year ago.

I have a non RG-6 cable just lying on the second story floor running to that HTPC from the 8-way distribution amplifier fed by a low noise preamp from my CM4228HD.

A full channel scan shocked me with the RF 2 which I have never seen before. That might be used as a RF 5 antenna next year after the repack.

On my active HTPC RF 2 has never been seen.

So, after phase 9 is complete on May 9, 2020 I may have RF 5.

Should there be any need or desire, it would depend on how the streams on KRCB VC 22 RF 5 and KPJK VC 60 RF 27 are assigned. Should the programming be duplicated ( I consider very likely as RF 5 cannot be received by most viewers) then no problem.

SHF

Note: When it is hot I will not run two HTPCs, my AC cannot keep up with just one running.
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post #17823 of 17921 Old 08-19-2019, 03:54 PM
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Got a stellar labs fringe vhf antenna mounted in my attic. Outside is not an option. I have a rca preamp, but it's a bit underpowered to get vhf for me reliably. Thinking of using a kitztech kt-500. Thoughts? Thanks.

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post #17824 of 17921 Old 08-19-2019, 04:22 PM
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Thanks for the explanation! Seems like you can buy commercial 2x2 bow ties all day long like the DB4 but I have yet to see a commercial x1 vertical array. Why is that? Shipping size constraints? Seems like the 2x2 arrays are a compromised design.
YES, the so-called "2x2" array [aka "Vertically Stacked 2-Bay Bowties"] are a compromised design (just like DB-8e and C4) since they use a 2-Port RF Combiner, which has LOSS on the order of about 0.5 to 1.5+ dB....for example see Loss Measurements towards bottom of my fol. webpage:
https://imageevent.com/holl_ands/files/ota

BTW: A-D DB-4e, Solid Signal HDB-4X and CM-4221HD do NOT use a 2-Port RF Combiner....the box in the middle is a PCB (Printed Circuit Board) Balun.

=============================================
I did a Parametric Investigation to determine the UHF & Hi-VHF Performance of various WIDTH Screen Grid Reflectors, using M4 (9.5x9) as a "typical" 4-Bay Example. The "best" Width was found to be about 32-inches. Much smaller Widths resulted in Hi-VHF Gain reductions, esp. on Lower Channels where the Gain blew out the BACK of the Antenna:
https://imageevent.com/holl_ands/mul...creengridwidth

=============================================
Towards the bottom of the fol. "Loops" Album, you will see several examples where I greatly improved the Hi-VHF SWR by adding "Resonant Loop(s)" to the design:
https://imageevent.com/holl_ands/loops
"Eventually" I'll get around to re-Optimizing these designs for the NEW UHF Band....but since they were Optimized for 698 MHz Max, they're pretty good just as they are....

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post #17825 of 17921 Old 08-19-2019, 05:14 PM
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Originally Posted by EF9500 View Post
Got a stellar labs fringe vhf antenna mounted in my attic. Outside is not an option. I have a rca preamp, but it's a bit underpowered to get vhf for me reliably. Thinking of using a kitztech kt-500. Thoughts? Thanks.

I don't know what you mean by "underpowered" but I assume you mean you don't think it has enough gain. The most important parameter is System Noise Figure, not gain. Your coax run must be pretty short for an attic antenna. You don't need a high gain preamp like the KT-500. It may do more harm than good. A better choice is the KT-200. You can improve the System Noise Figure by a few dB over the RCA preamp. A detailed look at noise and preamps is on my page:

http://www.aa6g.org/DTV/Noise/noise.html
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post #17826 of 17921 Old 08-19-2019, 05:36 PM
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Originally Posted by holl_ands View Post
YES, the so-called "2x2" array [aka "Vertically Stacked 2-Bay Bowties"] are a compromised design (just like DB-8e, C4 and DB4e) since they use a 2-Port RF Combiner, which has LOSS on the order of about 0.5 to 1.5+ dB....for example see Loss Measurements towards bottom of my fol. webpage:
https://imageevent.com/holl_ands/files/ota
What makes you think the DB4e uses a hybrid combiner?

It looks like a harness and a balun as with your HHH. I think the balun is the UP2A; ADTech can confirm that.


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post #17827 of 17921 Old 08-19-2019, 07:43 PM
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Originally Posted by Calaveras View Post
I don't know what you mean by "underpowered" but I assume you mean you don't think it has enough gain. The most important parameter is System Noise Figure, not gain. Your coax run must be pretty short for an attic antenna. You don't need a high gain preamp like the KT-500. It may do more harm than good. A better choice is the KT-200. You can improve the System Noise Figure by a few dB over the RCA preamp. A detailed look at noise and preamps is on my page:

http://www.aa6g.org/DTV/Noise/noise.html
Yes, gain. I just emailed someone at kitz, and they recommended the kt-200 like you did. I ordered it, should have it by Friday. Will update how it works out. Thanks.

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post #17828 of 17921 Old 08-20-2019, 07:44 AM
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Originally Posted by holl_ands View Post
YES, the so-called "2x2" array [aka "Vertically Stacked 2-Bay Bowties"] are a compromised design (just like DB-8e, C4 and DB4e) since they use a 2-Port RF Combiner, which has LOSS on the order of about 0.5 to 1.5+ dB....for example see Loss Measurements towards bottom of my fol. webpage:
https://imageevent.com/holl_ands/files/ota

BTW: Solid Signal HDB-4X and CM-4221HD do NOT use a 2-Port RF Combiner....the box in the middle is a PCB (Printed Circuit Board) Balun.

=============================================
I did a Parametric Investigation to determine the UHF & Hi-VHF Performance of various WIDTH Screen Grid Reflectors, using M4 (9.5x9) as a "typical" 4-Bay Example. The "best" Width was found to be about 32-inches. Much smaller Widths resulted in Hi-VHF Gain reductions, esp. on Lower Channels where the Gain blew out the BACK of the Antenna:
https://imageevent.com/holl_ands/mul...creengridwidth

=============================================
Towards the bottom of the fol. "Loops" Album, you will see several examples where I greatly improved the Hi-VHF SWR by adding "Resonant Loop(s)" to the design:
https://imageevent.com/holl_ands/loops
"Eventually" I'll get around to re-Optimizing these designs for the NEW UHF Band....but since they were Optimized for 698 MHz Max, they're pretty good just as they are....
Excellent information as always.
Yes, a properly designed 4 bay phased array merely needs a 4 to 1 balun in order to use coax so that is the only loss.
Same with the 4228, 8800, and U8000 eight bay phased arrays.
They merely use a single 4 to 1 balun instead of the greater loss of using two baluns, a combiner, and coax jumpers as several others use.
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post #17829 of 17921 Old 08-20-2019, 07:55 AM
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Using a "low noise" preamp on low vhf frequencies has little benefit since the noise floor at those frequencies is so high you won't normally see the advantage a low noise amp offers
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post #17830 of 17921 Old 08-20-2019, 08:00 AM
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Yes, gain. I just emailed someone at kitz, and they recommended the kt-200 like you did. I ordered it, should have it by Friday. Will update how it works out. Thanks.

Don't be disappointed if it doesn't make any difference. As rabbit73 illustrated above, Hi-VHF often has more environmental noise than UHF. A lower noise preamp may not make any improvement. I'm using a KT-200 on Hi-VHF and UHF and saw couple of dB improvement on some very weak stations.
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post #17831 of 17921 Old 08-20-2019, 09:38 AM
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The $300 Blonder Tongue preamps i have used for decades have a 3.5Db noise figure on low VHF which is more than adequate for that band.
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post #17832 of 17921 Old 08-20-2019, 10:40 AM
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Originally Posted by Calaveras View Post
Don't be disappointed if it doesn't make any difference. As rabbit73 illustrated above, Hi-VHF often has more environmental noise than UHF. A lower noise preamp may not make any improvement. I'm using a KT-200 on Hi-VHF and UHF and saw couple of dB improvement on some very weak stations.
Well according to specs, the kt-200 has about 10db more gain. Not looking for a miracle, just enough to make vhf more stable.

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post #17833 of 17921 Old 08-20-2019, 12:12 PM
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Well according to specs, the kt-200 has about 10db more gain. Not looking for a miracle, just enough to make vhf more stable.

True but irrelevant. 17 dB gain on high VHF is probably plenty of gain for your setup. More gain does not equal better reception. Please read the article I linked above that explains this.
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post #17834 of 17921 Old 08-20-2019, 12:21 PM
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Originally Posted by old tv guy View Post
Using a "low noise" preamp on low vhf frequencies has little benefit since the noise floor at those frequencies is so high you won't normally see the advantage a low noise amp offers

At my previous location which was rural and quiet I ran some tests on low VHF and found that the ambient noise was about 10 dB higher than on UHF. A system noise figure of <10 dB made no improvement in the SNR as shown by the receiver. I ended up using no preamp at all with no negative impact.
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post #17835 of 17921 Old 08-20-2019, 12:49 PM
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Well according to specs, the kt-200 has about 10db more gain. Not looking for a miracle, just enough to make vhf more stable.
Huh? According to the specs I looked at, the KT-500 has about 10 dB more gain than the KT-200, but I don't think that extra 10 dB is going to help you.

You haven't even told us your location or shown us your signal report as required in the sticky, making it difficult to give you accurate advice.
https://www.avsforum.com/forum/25-hd...-1st-post.html

The scraps of information that I had to hunt for were Stony Brook, attic antenna, VHF channel problem, LED lamps causing VHF interference; I don't know how accurate those clues are. More antenna gain and more preamp gain will not help you, they will make the signals and the noise interference stronger, resulting in no improvement.
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Yes, gain. I just emailed someone at kitz, and they recommended the kt-200 like you did. I ordered it, should have it by Friday. Will update how it works out. Thanks.
Which one did you order to replace your failed RCA preamps in the attic, the KT-200 standard power or the one for remote coax power? Do you have AC power in the attic?
http://kitztech.com/standard_coax.html

I had two RCA TVPRAMP1R preamps, new and in sealed boxes; they both failed. I'm not impressed with their quality control, and would have paid more for a more reliable preamp.

If you can not measure it, you can not improve it.
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post #17836 of 17921 Old 08-20-2019, 01:02 PM
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"Eventually" I'll get around to re-Optimizing these designs for the NEW UHF Band....but since they were Optimized for 698 MHz Max, they're pretty good just as they are....
This brings up a good question. What will it take to optimize these for after the repack? From my very limited antenna experience I would guess that the bow tie elements would get a bit longer and the spacing between bow ties might change.

So, does anyone know if any of the commercially available bow ties have yet been tweaked for post repack or when/if they might or might not?
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post #17837 of 17921 Old 08-20-2019, 01:10 PM
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Huh? According to the specs I looked at, the KT-500 has about 10 dB more gain than the KT-200, but I don't think that extra 10 dB is going to help you.

Maybe I'm confused but I thought he was comparing the RCA preamp to the KT-200. The KT-200 does have roughly 10 dB more gain than the RCA preamp on Hi-VHF.
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post #17838 of 17921 Old 08-20-2019, 01:22 PM
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Oh, OK. That's possible, 16 vs 26. That might help in the attic.
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post #17839 of 17921 Old 08-20-2019, 02:59 PM
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Huh? According to the specs I looked at, the KT-500 has about 10 dB more gain than the KT-200, but I don't think that extra 10 dB is going to help you.

You haven't even told us your location or shown us your signal report as required in the sticky, making it difficult to give you accurate advice.
https://www.avsforum.com/forum/25-hd...-1st-post.html

The scraps of information that I had to hunt for were Stony Brook, attic antenna, VHF channel problem, LED lamps causing VHF interference; I don't know how accurate those clues are. More antenna gain and more preamp gain will not help you, they will make the signals and the noise interference stronger, resulting in no improvement.

Which one did you order to replace your failed RCA preamps in the attic, the KT-200 standard power or the one for remote coax power? Do you have AC power in the attic?
http://kitztech.com/standard_coax.html

I had two RCA TVPRAMP1R preamps, new and in sealed boxes; they both failed. I'm not impressed with their quality control, and would have paid more for a more reliable preamp.
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Maybe I'm confused but I thought he was comparing the RCA preamp to the KT-200. The KT-200 does have roughly 10 dB more gain than the RCA preamp on Hi-VHF.
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Oh, OK. That's possible, 16 vs 26. That might help in the attic.
Sorry, yes i was comparing to my failed RCA, and yes my vhf antenna is in attic. I am 60 miles from the WTC, and ESB. I did purchase a new RCA from amazon, and probably will return it when I receive my kt-200. I will be combining my vhf and uhf using the Ad combiner, and then amping both with the KT. My Uhf is rock solid, using a cs4 mounted out on the roof. VHF is definitely very strange when it comes to position. I am sure i could eliminate my signal issues by mounting outdoors, but the wife is having no part of the huge stellar labs 30-2476 on the roof. I just spent the last 2 hours in my attic(135 degrees) moving my antenna around. I just gained 10db on my signal just by moving it. Thats where I am at right now.

Edit...ugh. Just like that...vhf is GONE! Just figured out, when my central air is on, I lose signal. Geezer. Are there any sort of smallish vhf antennas I could try on the roof? My wife won't be happy with the stellar labs up there.

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post #17840 of 17921 Old 08-20-2019, 03:41 PM
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What makes you think the DB4e uses a hybrid combiner?

It looks like a harness and a balun as with your HHH. I think the balun is the UP2A; ADTech can confirm that.
I think you are right [although technically it COULD be a PCB Balun....OR a 2-Port Combiner]....I fixed my post.
Note that A-D Technical Data Sheet for DB-4e does NOT say it has a 2-Port Combiner (whereas DB8e TDS does):
https://www.antennasdirect.com/cmss_...s/DB4E-TDS.pdf
https://www.antennasdirect.com/cmss_...s/DB8E-TDS.pdf

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post #17841 of 17921 Old 08-20-2019, 04:04 PM
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Originally Posted by Steve347 View Post
This brings up a good question. What will it take to optimize these for after the repack? From my very limited antenna experience I would guess that the bow tie elements would get a bit longer and the spacing between bow ties might change.

So, does anyone know if any of the commercially available bow ties have yet been tweaked for post repack or when/if they might or might not?
Bowtie Length is significantly longer, as is the Bowtie-to-Bowtie Spacing.

I use Computer Driven OPTIMIZATION software (thanks to nikmil) that randomly picks different values for these and other variables [SIXTEEN Total in FF6 with FLAT Reflector], evaluates each random pick....repeat ad nauseum using nikiml's Genetic Search algorithm...until, many days later, it finds the "best" combination of variables....at which time I find that I need to tweak the original antenna model and do it all over again...which is where I am at in Re-Opt of NEW UHF Band FF6 with FLAT Screen Grid Reflector....

I don't know of any Commercial Bowtie's that have been re-Optimized for 608 MHz Max.
And if any mfr's are working on it, they are very likely to keep their mouth SHUT until they announce it's ready for sale...
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post #17842 of 17921 Old 08-20-2019, 04:20 PM
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Sorry, yes i was comparing to my failed RCA, and yes my vhf antenna is in attic. I am 60 miles from the WTC, and ESB. I did purchase a new RCA from amazon, and probably will return it when I receive my kt-200. I will be combining my vhf and uhf using the Ad combiner, and then amping both with the KT. My Uhf is rock solid, using a cs4 mounted out on the roof. VHF is definitely very strange when it comes to position. I am sure i could eliminate my signal issues by mounting outdoors, but the wife is having no part of the huge stellar labs 30-2476 on the roof. I just spent the last 2 hours in my attic(135 degrees) moving my antenna around. I just gained 10db on my signal just by moving it. Thats where I am at right now.

Edit...ugh. Just like that...vhf is GONE! Just figured out, when my central air is on, I lose signal. Geezer. Are there any sort of smallish vhf antennas I could try on the roof? My wife won't be happy with the stellar labs up there.

You can take the back reflector off the 30-2476 and it works okay. It will have a lower visual profile. Another option is to just have a single reflector tube behind the folded dipole. I've even chopped the first 2 directors off a 30-2476 and it worked good. Maybe post your rabbitears info and you can get more specific advice for particular channel(s) you want. https://www.rabbitears.info/searchmap.php
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..
I don't know of any Commercial Bowtie's that have been re-Optimized for 608 MHz Max.
And if any mfr's are working on it, they are very likely to keep their mouth SHUT until they announce it's ready for sale...
I see some Antenna Direct DB8 at the bargain discount store. Maybe AD reducing warehouse stocks to get ready for the new ones.
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post #17844 of 17921 Old 08-20-2019, 04:29 PM
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Edit...ugh. Just like that...vhf is GONE! Just figured out, when my central air is on, I lose signal. Geezer. Are there any sort of smallish vhf antennas I could try on the roof? My wife won't be happy with the stellar labs up there.
How unfortunate. Would she go for the smaller 30-2475 or the even smaller AD C5? Using just one reflector and removing a few directors from the 2476 or a 2475, as suggested above by johnny antenna, is an interesting idea, they aren't expensive.

Is the central air in front of the antenna, or do you think the central air is creating electrical noise interference like LED lamps can? If you think it is electrical interference, hunt for the source with a portable radio tuned to a clear channel on the AM broadcast band. It's not required by the NEC for an indoor antenna, but sometimes grounding the coax shield with a grounding block connected to the house electrical system ground can help to reject interference.
https://www.fcc.gov/consumers/guides...ephone-signals

Did you get the VHF dipole with your AD CS4 UHF antenna? How does it do?

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Quote:
Originally Posted by johnny antenna View Post
Maybe post your rabbitears info and you can get more specific advice for particular channel(s) you want. https://www.rabbitears.info/searchmap.php
This is a generic report for Stony Brook. A report for your exact location might be different:
https://www.rabbitears.info/searchma...&study_id=5409

extract from report:

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If you can not measure it, you can not improve it.
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www.megalithia.com/elect/aerialsite/dttpoorman.html

Last edited by rabbit73; 08-20-2019 at 05:33 PM.
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post #17846 of 17921 Old 08-20-2019, 05:33 PM
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Quote:
Originally Posted by rabbit73 View Post
This is a generic report for Stony Brook:
https://www.rabbitears.info/searchma...&study_id=5409
...
I think the issues in New York after the repack haven't been completely worked out. Probably better to check the NY thread for people more familiar.
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post #17847 of 17921 Old 08-20-2019, 06:16 PM
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Originally Posted by adream8 View Post
This assessment intuitively strikes me as accurate.

The signals seem a bit weaker overall down lower, though not enough to lose channels. But down lower the reflections may also be reduced, so I get better results overall.

I'm going to play around with the 8-bay down lower first, but then I will probably try a 91 element Yagi.

Would all of these work equally well?

Stellar Labs 30-2370 ($40 shipped)
https://www.newark.com/stellar-labs/...ent/dp/72Y2542

Extreme Signal HDB91X ($55 shipped)
https://www.solidsignal.com/pview.asp?p=hdb91x

Antenna's Direct 91XG ($70 shipped)
https://www.amazon.com/Directional-U.../dp/B000LZ9EXI

The 30-2370 seems a bargain if it works as well as the 91XG.

I also like this Yagi18A imported from GB that is optimized for the repack frequency range:

Yagi 18A ($48 shipped)
https://www.aerialsandtv.com/onlineaerials.html#Yagi18s
I've ordered a Blake DMX16A and JBX21A and a REMO BAS-X11102 MAXI to compare side-by-side with a Stellar Labs 30-2370/HDB91X. I'll be doing A/B testing with SNR meter and spectrum analyzer and writing up a post to share with the peanut gallery. Extra gain could certainly help on some of my fringe jobs.

(Certainly open to suggestion for other high gain yagis available in the US).
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Last edited by mattdp; 08-20-2019 at 06:20 PM.
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post #17848 of 17921 Old 08-20-2019, 06:35 PM
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Originally Posted by mattdp View Post
I've ordered a Blake DMX16A and JBX21A and a REMO BAS-X11102 MAXI to compare side-by-side with a Stellar Labs 30-2370/HDB91X. I'll be doing A/B testing with SNR meter and spectrum analyzer and writing up a post to share with the peanut gallery. Extra gain could certainly help on some of my fringe jobs.

(Certainly open to suggestion for other high gain yagis available in the US).
Fracarro BLU920F is available from Summit.

I have tried to order a Kathrein Olympia 180 corner reflector but it's not stocked in the US despite being in their US distributor catalog. I always thought those Kathrein corner reflectors had a nice aesthetic on the elements.
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post #17849 of 17921 Old 08-20-2019, 07:10 PM
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Sorry guys
http://www.tvfool.com/?option=com_wr...9038e801023797

Trying to get 7, 11, and 13. For some reason 13 wnet is not on that list. Strange
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Last edited by EF9500; 08-20-2019 at 07:34 PM.
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post #17850 of 17921 Old 08-20-2019, 07:18 PM
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Quote:
Originally Posted by rabbit73 View Post
How unfortunate. Would she go for the smaller 30-2475 or the even smaller AD C5? Using just one reflector and removing a few directors from the 2476 or a 2475, as suggested above by johnny antenna, is an interesting idea, they aren't expensive.

Is the central air in front of the antenna, or do you think the central air is creating electrical noise interference like LED lamps can? If you think it is electrical interference, hunt for the source with a portable radio tuned to a clear channel on the AM broadcast band. It's not required by the NEC for an indoor antenna, but sometimes grounding the coax shield with a grounding block connected to the house electrical system ground can help to reject interference.
https://www.fcc.gov/consumers/guides...ephone-signals

Did you get the VHF dipole with your AD CS4 UHF antenna? How does it do?
The vhf dipole didn't do very good. I might try taking the front section off the 2476...basically making it the shorter 2475, then maybe take the back reflector off, and try it on the mast with my cs4. Maybe that will cure all my el noise interference, and give me enough gain. I will also try using a ground block on the coax.

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