The Official AVS Antenna and Related Hardware Topic! - Page 618 - AVS Forum | Home Theater Discussions And Reviews
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post #18511 of 18537 Old 05-21-2020, 05:04 PM
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Quote:
Originally Posted by Calaveras View Post
Okay, taking my cue from what you recently said. Do it the right way, not the easy way.

Two sections of Rohn 25 with an eave bracket will hold your 2" mast nicely. It's also easy to work on. I only use towers these days unless it's a very small antenna.

How far are your transmitter(s)? Do you still need the extreme setup at your new location, or is it more a case of you already had it? It doesn't look like you're facing nearby obstacles other than cactus

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post #18512 of 18537 Old 05-21-2020, 05:56 PM
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Quote:
Originally Posted by lifespeed View Post
How far are your transmitter(s)? Do you still need the extreme setup at your new location, or is it more a case of you already had it? It doesn't look like you're facing nearby obstacles other than cactus

All the important stations are located on Mt. Bigelow which is 77 miles away over a 1 edge path. The edge is 34 miles from here. I do need good antennas. The biggest antennas are on the 20' tower because signals are not as good as they are on my ham radio tower with antennas at 65'. On that tower I'm using my 37 element LPDA on a 9' boom and a homemade 10 element yagi for VHF which is very similar to the 30-2475. I can't ignore VHF because my ABC station is on channel 9.

My Rabbitears report:

https://www.rabbitears.info/searchma...study_id=11616

I can receive all the stations down to K35OU although that one is marginal but what do you expect for station with just 450 watts in my direction at 77 miles?

I've attached a spectrum analyzer trace of the UHF band here. All the Mt. Bigelow stations are labeled in magenta and are in the same direction. This a composite scan. All the stations labeled in yellow are scattered over 6 different directions.

Not much vegetation around here except weeds, grass and mesquite trees topping out at about 15'.

My only reception frustration is KMSB (FOX) on RF 25. It is tied for the strongest signal but it shares the channel with a low power Mexican station just 25 miles south of the border or 30 miles from here. There are 3 stations down there on RF 15, 25 and 34. All are quite strong. My KMSB reception is intermittent as no antenna has enough rejection to completely eliminate the co-channel interference. They could have put it on RF 24 which is open down here. KUVE RF34 suffers the same problem except it's a Spanish station and I don't watch it.

I'm hoping that when ATSC 3.0 gets to Tucson that the station will be on an open channel on Mt. Bigelow.

Chuck
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post #18513 of 18537 Old 05-21-2020, 06:42 PM
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Quote:
Originally Posted by Calaveras View Post
My only reception frustration is KMSB (FOX) on RF 25. It is tied for the strongest signal but it shares the channel with a low power Mexican station just 25 miles south of the border or 30 miles from here. There are 3 stations down there on RF 15, 25 and 34. All are quite strong. My KMSB reception is intermittent as no antenna has enough rejection to completely eliminate the co-channel interference. They could have put it on RF 24 which is open down here. KUVE RF34 suffers the same problem except it's a Spanish station and I don't watch it.

I'm hoping that when ATSC 3.0 gets to Tucson that the station will be on an open channel on Mt. Bigelow.

You've got a Border Blaster!!




Yes, you need to wield the big guns. Mind if I ask the reason for your move from the foothills in CA?

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post #18514 of 18537 Old 05-21-2020, 07:42 PM
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Originally Posted by lifespeed View Post
Mind if I ask the reason for your move from the foothills in CA?

Not appropriate subject matter for this forum. PM me if you really want to know.

Chuck
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post #18515 of 18537 Old 05-22-2020, 08:04 PM
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I'm in WA now and I installed the new CM B71 filter and it helps, but this illustrates how hard it is to filter something so close with consumer grade stuff.

I will be doing more work tomorrow, including putting in the VHF bowtie.
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post #18516 of 18537 Old 05-22-2020, 08:53 PM
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Quote:
Originally Posted by Falcon_77 View Post
I'm in WA now and I installed the new CM B71 filter and it helps, but this illustrates how hard it is to filter something so close with consumer grade stuff.

I will be doing more work tomorrow, including putting in the VHF bowtie.
It looks pretty good, and you can see the front end of your measuring receiver (hobbyist SDR?) overloading and causing spectral regrowth. Probably what is happening in your tuner. But the filter, while not eliminating the signal, does reduce the level somewhat.

So what does your tuner think of the filter? Can you tell if it is less saturated? Despite your protestations, I think the combination of a repack antenna like the XB16A with it's better impedance match to a filter would do even better. Try a 1 or 2 dB pad between the antenna and filter to help prevent unwanted interaction between the reactive source and load, although this may not be necessary with the narrowband antenna.

I don't quite follow why you gave away the "better" XB16A. Because it wasn't enough better? Did you try it in combination with the filter? I guess this is all happening inside your attic with lots of confounding variables, so really pointless to read much into it. To do experiments you need to remove uncontrolled variables.

If you're passing judgement based on attic experiments, don't.

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post #18517 of 18537 Old 05-24-2020, 01:27 PM
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UHF is doing considerably better with the CM 608 MHz filter, but I might throw in some attenuation.

What's been taking most of my time this trip is the Hi-V side. 13 isn't bad, but 11 and especially 9 are really tough.

Here's where I'm at on it. See pic. I've tried the bow-tie and GE inside in the new attic location and outside (side of the house - not the rooftop). Outside the window was a bit worse and it is about 8' lower so it made sense.

I'm going to put the Stellar 30-2475 back online next at the new attic location (now that I have floorboards I installed, where I need them).
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post #18518 of 18537 Old 05-24-2020, 03:17 PM
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Quote:
Originally Posted by Falcon_77 View Post
What's been taking most of my time this trip is the Hi-V side. 13 isn't bad, but 11 and especially 9 are really tough.
https://www.rabbitears.info/searchma...study_id=93095







Looks difficult.
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If you can not measure it, you can not improve it.
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post #18519 of 18537 Old 05-26-2020, 12:13 PM
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Indeed it is for RF 9. I didn't get a chance to set up the Stellar in the new spot. I spent about half the trip laying more floorboards and pulling weeds in the yard (which I didn't even finish). I needed another two days. Hopefully in early July and I might just go straight to the 30-2476 then.
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post #18520 of 18537 Old 05-28-2020, 06:47 PM
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Using an SDR to Help Find the Best Antenna Location for a Problem Channel

Quote:
Originally Posted by Prototype3a View Post
In other news, Ch9 WSWP is still very unpredictable for performance. I haven't really messed with the setup any as I intend to get an RTLSDR and then see what I can learn from that. As such, can multipath be "seen" with an RTLSDR?
https://www.rabbitears.info/searchma...study_id=84216
Quote:
Originally Posted by Prototype3a View Post
To be clear, I can receive WSWP but it seems that the precise positioning of the antenna is critical and so I'm trying to better understand the factors that impact that and if there are modifications to the big antenna that I could make to improve the performance or simply make it more forgiving. One thing I had thought about was to add more or larger reflector rods to help it to reject unwanted signals.
I'm having trouble receiving RF 11 which is ABC. I didn't have any trouble with it in my old room when it was on 13; in my new room there is a tree in the signal path.

Being able to measure signal strength and signal quality are certainly helpful, but being able to see the shape of the transmitted signal with an SDR can be extremely helpful in finding the best location for an antenna.









As a double check, on another day I tried the RTL-SDR dongle:





Although it is encouraging to see a flat channel scan (with sufficient SNR), it shouldn't be interpreted as a guarantee of reliable reception. It is possible to have a flat scan, but the tuner is unable to decode the signal.

In my case, with channel 11, it was a reliable indicator.
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post #18521 of 18537 Old 05-28-2020, 08:19 PM
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Originally Posted by rabbit73 View Post
Being able to measure signal strength and signal quality are certainly helpful, but being able to see the shape of the transmitted signal with an SDR can be extremely helpful in finding the best location for an antenna.
I agree, rabbit, though I need to do more of this in Washington. I'm actually using the same GE (the lower left one) in the attic there right now. It did better than my homebrew VHF-Hi bowtie. It's pretty effective for its size and certainly easier to move around in the attic vs. a big Stellar.

I hope you don't have much Lo-E glass over there. It is widely used in SoCal on any newer installations and isn't kind to OTA and cell reception for that matter. That plus stucco siding.

Speaking of a big Stellar antenna, attached is a pic of my Stellar which I have now mounted on the deck. It seems to be working well, but it's hard to tell yet as I have been getting some powerful tropo out of San Diego lately. Oh no, there's the rotation problem again.

I'm using the CM7777HD on "low-gain" mode after bringing it back down after my WA trip last weekend. It's doing well in this role. I am using a Stellar combiner to feed it.
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post #18522 of 18537 Old 05-28-2020, 08:34 PM
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Also, here's a nifty device that I found on eBay. I'm testing it out, but I think it will be very useful for helping overload problems. It's a RS 15-678 variable attenuator.
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post #18523 of 18537 Old 05-28-2020, 10:05 PM
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Wow! That's an impressive list of stations you're receiving, Falcon! Congratulations!

My complete SF Bay Area DTV Station Lists: http://www.larrykenney.com/sfonair.html
Lots of Broadcasting links and information: http://www.larrykenney.com/broadcast.html
Live reception scans from my HD Home Run receivers: http://www.larrykenney.com/hdhr/
Photos and info on my antennas: http://www.larrykenney.com/tvantennas.html
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post #18524 of 18537 Old 05-29-2020, 09:47 AM
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Thanks, Larry! Well, it's just the tropo, but it does help to have antennas pointing that way.

Ok all, I have two HDHR's set up now, one for LA and the other for SD. How do I figure out which one is being used by the HDHR software program to actually watch them and next I need to figure out how to get them to pass data to the SmartTVs.

Perhaps there's an HDHR thread somewhere on AVS I should hop onto as this is going to be a software issue now vs. hardware.
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post #18525 of 18537 Old 05-29-2020, 06:44 PM
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Quote:
Originally Posted by Falcon_77 View Post
I hope you don't have much Lo-E glass over there. It is widely used in SoCal on any newer installations and isn't kind to OTA and cell reception for that matter. That plus stucco siding.
My first exposure to the Low-E glass problem was in Sept 2008, so I was wondering about it now:
https://www.avsforum.com/forum/25-hd...y-antenna.html



I made some tests with an original CM4221 in the window. The retirement home that I'm in is fairly old, so I doubt that the glass is Low-E. My measurements seem to indicate that, but I wasn't able to confirm it because I couldn't get the window fully open; there is a safety stop that keeps the window from opening any more than 5". I could build a little UHF Yagi and stick it out that opening.

I first compared the GE29884 with the Original CM4221:
Code:

GE29884 vs Original CM4221 at Left Window

RF          GE29884            CM4221
          dBmV   dBm        dBmV    dBm
16       +7.8   -41.0      +10.9   -37.9
33       +4.7   -44.1       +9.4   -39.4
40       -7.5   -56.3       +3.6   -45.2
Next, I wanted to see how much the venetian blind attenuated the signals:

Channel 16, CM4221
Blind down, slats closed: about -10 dBmV
Blind down, slats open: about -10 dBmV
Blind up: about +10 dBmV

So, the venetian blind attenuates the signal about 20 dB.
The window sill is about 9" deep. The space between the glass and the blind is about 7-1/2", which is enough room for a panel antenna.

The glass is double layer with an air space between. There are plastic muntins between the two layers of glass to divide the window into 6 lites. The screen appears to be plastic.

Quote:
Speaking of a big Stellar antenna, attached is a pic of my Stellar which I have now mounted on the deck. It seems to be working well, but it's hard to tell yet as I have been getting some powerful tropo out of San Diego lately. Oh no, there's the rotation problem again.
Nice photo of your antennas on the deck. I edited your photo and told it to behave.

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post #18526 of 18537 Old 05-30-2020, 06:57 AM
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Quote:
Originally Posted by Falcon_77 View Post
Speaking of a big Stellar antenna, attached is a pic of my Stellar which I have now mounted on the deck. It seems to be working well, but it's hard to tell yet as I have been getting some powerful tropo out of San Diego lately.


Your photo is excellent; I know an excellent photo when I see it, because I was a Government photographer for 30 years. While staring at your photo, I noticed something unusual: the 1st Director is between the Reflector and the Driven Element (DE). Usually, the 1st Director would be mounted in front of the DE.



I don't understand why you did that. It might compromise the performance of the antenna; how much, is difficult to say without modeling or range tests. As usual with an off-shore product, the instructions aren't very good.



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post #18527 of 18537 Old 05-30-2020, 09:49 AM
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Quote:
Originally Posted by rabbit73 View Post
While staring at your photo, I noticed something unusual: the 1st Director is between the Reflector and the Driven Element (DE). Usually, the 1st Director would be mounted in front of the DE.
I don't understand why you did that. It might compromise the performance of the antenna; how much, is difficult to say without modeling or range tests.

I saw that too. I'm about 99% sure that is not right. It will have a major impact on performance.
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post #18528 of 18537 Old 05-30-2020, 09:57 AM
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Quote:
Originally Posted by rabbit73 View Post
...I noticed something unusual: the 1st Director is between the Reflector and the Driven Element (DE). Usually, the 1st Director would be mounted in front of the DE.
I noticed that as well, and wondered if it was intentional for some reason, or just a misstep when assembling the antenna? I think the only effect of the misplaced element would be to move the driven element farther from the reflector. That would affect SWR and gain somewhat at the design frequencies, I would think.
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post #18529 of 18537 Old 05-30-2020, 11:51 AM
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It's not right. You need to take the back section off, and swing the back boom the other way with the VHF loop at the very end, then reinstall the reflector section.
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post #18530 of 18537 Old 05-31-2020, 09:53 AM
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Airspy R2 vs SDRplay RSP1A

The SDRplay seems like a nice upgrade over the RTLSDR but is the Airspy R2 worth the extra ~$50 over the RSP1A?
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post #18531 of 18537 Old 05-31-2020, 11:12 AM
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Quote:
Originally Posted by Prototype3a View Post
Airspy R2 vs SDRplay RSP1A

The SDRplay seems like a nice upgrade over the RTLSDR but is the Airspy R2 worth the extra ~$50 over the RSP1A?
The RSP1A has a 10 MHz bandwidth, so you can see a whole channel in real time with the SDRuno software. You only see part of a channel in real time with the RTL-SDR.com dongle and the SDR# software. There is also spectrum analyzer software for the RSP1A. Big advantage for that upgrade.



Video:
https://www.dropbox.com/s/vrc82x4u45...31-20.mp4?dl=0

Going to the Airspy R2 and SDR# software is more expensive. It can also do a whole channel, but I couldn't resist because of the included Spectrum Spy spectrum analyzer software.









Video, no sound:

https://www.dropbox.com/s/gecnrpd46w...17-32.mp4?dl=0

Video, has audio:

https://www.dropbox.com/s/1gkjgk199n...52-12.mp4?dl=0
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post #18532 of 18537 Old 05-31-2020, 09:37 PM
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I didn't realize that the lower half of the spectrum spy display scans....like... well... sonar.
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post #18533 of 18537 Old Yesterday, 04:44 AM
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Quote:
Originally Posted by Prototype3a View Post
I didn't realize that the lower half of the spectrum spy display scans....like... well... sonar.
The lower half is called a "waterfall." The color of a signal is determined by its strength. If the signal is intermittent, it will show a gap. When the gap occurred is marked by a date-time stamp. It's kind of neat, but I'm more interested in the upper half of the display.

If you can not measure it, you can not improve it.
Lord Kelvin, 1883
www.megalithia.com/elect/aerialsite/dttpoorman.html
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post #18534 of 18537 Old Yesterday, 08:51 AM
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While staring at your photo, I noticed something unusual: the 1st Director is between the Reflector and the Driven Element (DE). Usually, the 1st Director would be mounted in front of the DE.

I don't understand why you did that. It might compromise the performance of the antenna; how much, is difficult to say without modeling or range tests. As usual with an off-shore product, the instructions aren't very good.
Well, this helped me wake up on a slow Monday morning. You know how sometimes one doesn't see the obvious when looking right at it? I've re-assembled the 2nd front section and the reflector a number of times and I didn't notice this problem on the main section!

I've been more concerned about the extra spacing on that UHF antenna between the two sections, saying that doesn't look right... I can take a closer pic of that to see what you all think on that.

My best guess is the instructions weren't clear and I must have been thinking the driven should be right next to the mast mount, but as you can see I drilled my own holes further up the boom so it's not next to the mast even now.

Thanks all! This was a mistake in my assembly way back when (2 years ago I got it I think) and I didn't question it. I know better and should have noticed this before. Thanks again for setting me straight and I'm glad I posted the pic.

I will fix it and take another pic. I put the UHF on top in the interim as well, as it's easier to deal with in that position. Also, I put up a much simpler VHF-Hi Yagi (5 elements only) and it is almost as good as my busted build. Well, I will be very curious how much better the Stellar gets when built correctly!

Best,
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post #18535 of 18537 Old Today, 08:00 AM
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I posted this over on the SF thread but it's probably of more interest here.

DIY 14 element high VHF yagi with full data:

https://www.avsforum.com/forum/45-lo...l#post59730934

Teaser image attached.
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post #18536 of 18537 Old Today, 10:38 AM
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I fixed the Stellar and attached is a pic of my current antenna setup towards San Diego. It is difficult to measure with tropo being so unpredictable, but compared to UHF (if even valid in the tropo world) it appears to be a fair amount better than the 5 element I had up temporarily and my prior configuration. I will keep watch on it for a few days.

One thing I will do to make it better is to remove the 6dB attenuator I have on the pre-amp input side to fit the 7777HD pre-amp into the water resistant Stellar combiner case.

Also attached is a closer pic of the UHF antenna showing the extra gap in the middle of directors 9 and 10. Maybe I have the front section backwards? Thoughts? ...I recall that I tried the other way, but the drill holes don't line up. And oh yes, dare I forget that the front most section is in my closet.

Edit: I found the instructions for it, which appear to confirm I have constructed those sections as intended, but is it ideal?

https://manuals.solidsignal.com/HDB91X-MANUAL.PDF
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Last edited by Falcon_77; Today at 11:04 AM.
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post #18537 of 18537 Old Today, 12:38 PM
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Quote:
Originally Posted by Falcon_77 View Post
Also attached is a closer pic of the UHF antenna showing the extra gap in the middle of directors 9 and 10. Maybe I have the front section backwards? Thoughts? ...I recall that I tried the other way, but the drill holes don't line up. And oh yes, dare I forget that the front most section is in my closet.

Edit: I found the instructions for it, which appear to confirm I have constructed those sections as intended, but is it ideal?

Chances are it is correct. Computer optimized and modeled antennas produce spacings and element sizes that do not uniformly taper towards the front as you might expect. The only thing that might not be optimum is that every director is the same size but they probably optimized the design with that limitation built in.

The 14 element high VHF yagi I just built has directors of decreasing size until director 10 which is longer and director 11 which is longer still. Then D12 is a shorter again. Same goes for the spacings. Some of the front spacings are much wider than you'd expect.
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