The Official AVS Antenna and Related Hardware Topic! - Page 597 - AVS Forum | Home Theater Discussions And Reviews
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post #17881 of 17920 Old 09-03-2019, 05:56 AM
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Originally Posted by adream8 View Post
.....

Anyone ever experience something like this on the CM-4228HD?

Any ideas on what might be going on here?
May be because of the style of harness the 4228hd has. The weakness of the 8-bay antennas is the feed lines/printed circuit board balun. If you were really wanting to tinker you could replace the harness with 2 traditional baluns and a reversed splitter. There are other harness mods too if you want to go way down the rabbit hole.
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post #17882 of 17920 Old 09-03-2019, 09:18 AM
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Originally Posted by johnny antenna View Post
May be because of the style of harness the 4228hd has. The weakness of the 8-bay antennas is the feed lines/printed circuit board balun. If you were really wanting to tinker you could replace the harness with 2 traditional baluns and a reversed splitter. There are other harness mods too if you want to go way down the rabbit hole.
Thanks. Yeah, I read about that, if you're referring to this:

http://www.hdtvprimer.com/ANTENNAS/TemporaryPage.html

But according to that data the sub-par harness seems to cause a drop off of about 1-1.5 dBi at around RF 23. I'm not sure why it would have any negative affect on performance at RF 13. The graph seems to indicate that it wouldn't.
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post #17883 of 17920 Old 09-03-2019, 09:41 AM
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Originally Posted by adream8 View Post
Quote:
Originally Posted by johnny antenna View Post
May be because of the style of harness the 4228hd has. The weakness of the 8-bay antennas is the feed lines/printed circuit board balun. If you were really wanting to tinker you could replace the harness with 2 traditional baluns and a reversed splitter. There are other harness mods too if you want to go way down the rabbit hole.[IMG class=inlineimg]/forum/images/smilies/biggrin.gif[/IMG]
Thanks. Yeah, I read about that, if you're referring to this:

http://www.hdtvprimer.com/ANTENNAS/TemporaryPage.html

But according to that data the sub-par harness seems to cause a drop off of about 1-1.5 dBi at around RF 23. I'm not sure why it would have any negative affect on performance at RF 13. The graph seems to indicate that it wouldn't.
Other than the harness, if the signal isn't equal across the bays that can cause poor reception too.
I'm not a fan of the 8 bay antennas, overly complicated in my opinion for the little gain over a 4 bay when you account for the loss in the harness.
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post #17884 of 17920 Old 09-03-2019, 10:04 AM
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Originally Posted by johnny antenna View Post
Other than the harness, if the signal isn't equal across the bays that can cause poor reception too.
I'm not a fan of the 8 bay antennas, overly complicated in my opinion for the little gain over a 4 bay when you account for the loss in the harness.
Hmm.. that's interesting. I've read that too. Maybe I should try a 4 bay.

The 8 bay does seem to be pulling most of my marginal channels better. I now have to wonder if a 4 bay might do as well.
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post #17885 of 17920 Old 09-03-2019, 12:05 PM
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Long time lurker, first time poster. I figured someone may benefit from my years of playing around with preamps in a fringe area. Below are some findings that are not anywhere near technical like the great posters on the forum (thanks Adtech). My setup:

- Cabin in the Northwoods of Wisconsin in a valley surrounded by tall evergreen trees
- WINEGARD HD-8800 UHF High-Gain 8-Bay mounted on roof of cabin (about 25' from ground)
- Samsung OLED TV using the internal signal meter screen showing SNR and number of signal bars (1-10)
- 3 different towers. 2 channels are low power translators (7.1, 34.1), 1 channel is higher power, non-translator (12.1). One of the low power translators though is fairly close to the cabin but not line of site (7.1)
- My Rabbitear Info is attached (I could not post the web link)

I had been using the Winegard AP-8275 for 7+ years with only the occasional drop out when it rained on the far low power translator tower (34.1). The last few months though it has been getting worse. Attached are my findings trying each of the following amps: Winegard AP-8275, Juice, RCA TVPRAMP1R, and the CM-7777HD using both the low and high settings. Juice seems to be my winner. Although the CM-7777HD on high setting is a bit better on my problem channel for SNR, I am worried about its enclosure for the elements outdoors. Support via email from Antennas Direct with my questions was great too. See my testing results from the Samsung TV signal meter screen.
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post #17886 of 17920 Old 09-03-2019, 12:35 PM
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Originally Posted by slthomas0 View Post
...Attached are my findings trying each of the following amps: Winegard AP-8275, Juice, RCA TVPRAMP1R, and the CM-7777HD using both the low and high settings. Juice seems to be my winner. Although the CM-7777HD on high setting is a bit better on my problem channel for SNR, I am worried about its enclosure for the elements outdoors. Support via email from Antennas Direct with my questions was great too. See my testing results from the Samsung TV signal meter screen.
What were your numbers with no pre-amp?
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post #17887 of 17920 Old 09-03-2019, 12:39 PM
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What were your numbers with no pre-amp?
I should have added I have about 60' of RG6 cable. I can't get any signal on channels 12.1 and 34.1 so i didn't even bother going up and down the ladder to swap the preamps and into the crawl space for swapping out the injectors to test without since I only could get 1 channel without a preamp.
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post #17888 of 17920 Old 09-03-2019, 02:19 PM
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Originally Posted by slthomas0 View Post
I figured someone may benefit from my years of playing around with preamps in a fringe area. Below are some findings that are not anywhere near technical like the great posters on the forum (thanks Adtech).

My takeaway is that your setup doesn't require a preamp with more than 20 dB gain as would be expected with only 60' of RG-6 coax. The two lowest gain preamps are essentially identical. Higher gain resulted in no improvement.

Did you measure the gain/NF or are these the manufacturer's specs? I measured an AP-8275 and the gain was more like 36 dB as opposed to what Winegard claimed. That's way too much gain except in a few special situations.
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post #17889 of 17920 Old 09-03-2019, 02:28 PM
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Originally Posted by Calaveras View Post
My takeaway is that your setup doesn't require a preamp with more than 20 dB gain as would be expected with only 60' of RG-6 coax. The two lowest gain preamps are essentially identical. Higher gain resulted in no improvement.

Did you measure the gain/NF or are these the manufacturer's specs? I measured an AP-8275 and the gain was more like 36 dB as opposed to what Winegard claimed. That's way too much gain except in a few special situations.
Thanks for the input - that is from the manufacturer on the noise and gain (or at least what I could find). I should have added I have 60' of RG6 and a 2-way splitter. Big miss on my part of the post.

Eight years ago when I first put up the antenna, I could only get 1 channel without a preamp so I added the Winegard. Since the Winegard appears to be going out, I played around with the preamps I listed in the screenshot this past weekend. It might be worth going up there once again and trying without a preamp to see if I can get that 1 weaker channel (34.1). Appreciate the input.
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post #17890 of 17920 Old 09-03-2019, 05:50 PM
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Originally Posted by adream8 View Post
Hmm.. that's interesting. I've read that too. Maybe I should try a 4 bay.

The 8 bay does seem to be pulling most of my marginal channels better. I now have to wonder if a 4 bay might do as well.
Thing is, a 4-bay wouldn't have much VHF reception at all. It doesn't have the wide reflector the 8-bay has.

You could still use it for UHF and the RCA for VHF, if the RCA gets all your VHF channels as well as it does with channel 13
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post #17891 of 17920 Old 09-10-2019, 01:40 PM
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SWR, return loss measurement utility for TV antennas?

I recently added a vector network analyzer (VNA) to my set of tools. Excellent tool for characterizing antennas used for amateur radio transmission...but I am wondering if there is any utility for TV antenna measurements, specifically...do measurements like SWR, impedance, return loss etc have any utility in comparing different TV antennas? I can definitely see some utility in measuring the line loss for different coax cables, when ends are placed across the two ports (S12).
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post #17892 of 17920 Old 09-10-2019, 02:50 PM
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Congratulations on your new VNA!

Because of the antenna reciprocity theorem, your VNA should be just as useful for receiving antennas as it is for transmitting antennas. As a matter of fact, antenna modeling programs treat the antenna as if it were for transmitting.

The most useful parameters would probably be impedance and SWR as proof of performance that comes after modeling.

In this presentation, by Dr. John Ross who invented the tapered loop for Antennas Direct, you will see several prototype antennas ready for measurement:

http://www.johnross.com/SBE_2008.pdf

his website:
http://www.johnross.com/

his equipment:
http://www.johnross.com/laboratory.html

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 #17893 of 17920 Old 09-10-2019, 02:53 PM
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Originally Posted by tustinfarm View Post
I recently added a vector network analyzer (VNA) to my set of tools. Excellent tool for characterizing antennas used for amateur radio transmission...but I am wondering if there is any utility for TV antenna measurements, specifically...do measurements like SWR, impedance, return loss etc have any utility in comparing different TV antennas? I can definitely see some utility in measuring the line loss for different coax cables, when ends are placed across the two ports (S12).
SWR, impedance and Return Loss are related and essentially the same thing. If two antennas claimed the same gain but one has a high SWR and the other a low SWR then the latter would have a higher real gain. Here's a calculator where you can calculate mismatch loss:

https://www.microwaves101.com/calcul...swr-calculator

Other than that I think the answer is "no." You can't measure gain or F/B Ratio easily.
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post #17894 of 17920 Old 09-10-2019, 03:22 PM
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Originally Posted by Calaveras View Post
SWR, impedance and Return Loss are related and essentially the same thing. If two antennas claimed the same gain but one has a high SWR and the other a low SWR then the latter would have a higher real gain. Here's a calculator where you can calculate mismatch loss:

https://www.microwaves101.com/calcul...swr-calculator

Other than that I think the answer is "no." You can't measure gain or F/B Ratio easily.
Thanks Calaveras and rabbit73 for the useful information...so it sounds like the SWR might have some limited value in comparing antennas, but won't tell the gain or F/B...just relative information if antennas are purported to have the same gain. And I suppose for an individual antenna the SWR plot might give a rough sense of where it would work best, i.e. hi-VHF, UHF etc.

All that said, I am having a TON of fun with the VNA, checking some FM traps I had laying around, and will be great for checking the LTE filter I have too.
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post #17895 of 17920 Old 09-10-2019, 05:30 PM
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First 4 Analyses of CM4228HD (As Shipped, with PCB Balun), with HHH [Holl_ands Horizontal Harness], with misc to improve Hi-VHF SWR, and with RCM (separate Baluns/Combiner):
https://imageevent.com/holl_ands/multibay

Most important is to use a Commercial Cylindrical Balun [which passes Ch2-69+] instead of Modern PCB Balun [which only passes UHF with low loss]...

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post #17896 of 17920 Old 09-18-2019, 07:41 PM
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Under ideal conditions, say you have one of those big old out door antennas like our grandparents had, and it was 30ft off the ground, what would be the maximum distance a tower could reach it with no obstructions? Talking about a full power main station like a CBS from a big city.
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post #17897 of 17920 Old 09-19-2019, 04:59 AM
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Quote:
Originally Posted by Matthew Hawkins View Post
Under ideal conditions, say you have one of those big old out door antennas like our grandparents had, and it was 30ft off the ground, what would be the maximum distance a tower could reach it with no obstructions? Talking about a full power main station like a CBS from a big city.
Probably a couple of hundred miles...you did say *ideal* conditions. I'm thinking of tropospheric propagation. Don't depend on it, though. Rare. Usually that infrequent type of propagation is more like 100 miles.

From what I understand the theoretical(?) distance is 70 miles due to the curvature of the earth (line of sight).

Lots of unknows... Age of coax cable? Length of coax cable? Preamp? Number of splitters involved? Last time antenna connections were checked for oxidation/corrosion? Is the desired station transmitting on a UHF or VHF frequency (most of the big old antennas like our grandparents used were VHF antennas). And then you get into the real technical stuff that is beyond me.

Realistically, I'd be happy with 50 miles as long as no nearby trees or buildings were between me and the transmitter. Also, look at a topo map to be sure there are no hills or mountains that could be putting you in the shadow of the signal, in other words blocking your line of sight between your antenna and the transmitter. I've got one station that is a hair over 50 miles from me that I have given up on due to a hill about halfway between me and that transmitter (20-25 miles distant). My antenna setup is far from optimal...actually it is really close to the ground. But, I can receive a mid-UHF station with my Antennas Direct DB8e consistently with it at about 40 miles. At 30' I figure it would perform much better.

But, again, I think the theoretical distance is 70 miles...or less.

I'm sure some of the antenna experts will give you some good information here, they're very knowledgeable.

Best wishes. It sounds like you've got a project!

Ed
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post #17898 of 17920 Old 09-19-2019, 07:44 AM
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Quote:
Originally Posted by Matthew Hawkins View Post
Under ideal conditions, say you have one of those big old out door antennas like our grandparents had, and it was 30ft off the ground, what would be the maximum distance a tower could reach it with no obstructions? Talking about a full power main station like a CBS from a big city.
If you mean "What is the line-of-sight distance between the transmitter and the receive antennas?" then use this:

http://www.ringbell.co.uk/info/hdist.htm

Add the distance for the transmitter antenna and receive antenna. For a 2000' high transmitter and a 30' high receive antenna the distance is roughly 60 miles.
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post #17899 of 17920 Old 09-19-2019, 10:23 AM
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I'm looking at two YAGI antennas and wondered if there is technically any benefit in one vs the other?

Mediasonic HOMEWORX HDTV Outdoor Antenna - 80 Miles Range Support UHF / VHF (HW-27UV)
RCA ANT751E
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post #17900 of 17920 Old 09-19-2019, 03:20 PM
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I'm looking at two YAGI antennas and wondered if there is technically any benefit in one vs the other?

Mediasonic HOMEWORX HDTV Outdoor Antenna - 80 Miles Range Support UHF / VHF (HW-27UV)
RCA ANT751E
You should get better VHF-Hi performance with the RCA ANT-751E. UHF performance will probably be about the same.
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post #17901 of 17920 Old 09-19-2019, 08:11 PM
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Quote:
Originally Posted by Matthew Hawkins View Post
Under ideal conditions, say you have one of those big old out door antennas like our grandparents had, and it was 30ft off the ground, what would be the maximum distance a tower could reach it with no obstructions? Talking about a full power main station like a CBS from a big city.
I guess you could call this ideal.Actually once in a lifetime. From a couple weeks ago.Brighton,ON using a CM4228 UHF.Bude,MS 1122 miles.


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post #17902 of 17920 Old 09-20-2019, 04:02 AM
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Originally Posted by Calaveras View Post
If you mean "What is the line-of-sight distance between the transmitter and the receive antennas?" then use this:

http://www.ringbell.co.uk/info/hdist.htm

Add the distance for the transmitter antenna and receive antenna. For a 2000' high transmitter and a 30' high receive antenna the distance is roughly 60 miles.
One thing this shows is that (IN THEORY!) the antenna height doesn't matter very much at all, such as in my case for Chicago stations 58 miles across Lake Michigan from my southwest Michigan house. Because the broadcast antennas are so high, having your receiving antenna high is almost exclusively needed to avoid local obstructions, not to improve the theoretical line of sight (avoiding curvature of earth problems) to the transmitter.

Getting that antenna higher is needed for most of us only to avoid local obstructions and nothing else. The transmitting antenna is high enough (usually) to avoid curvature of earth line of sight issues.

Put another way, if I lived on the shores of Lake Michigan with no local obstructions, I should be able to have my antenna close to ground level and it should make little difference compared to 30 feet up on my roof for reception of Chicago stations across the lake 58 miles away.
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post #17903 of 17920 Old 09-25-2019, 10:39 AM
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Probably a couple of hundred miles...you did say *ideal* conditions. I'm thinking of tropospheric propagation. Don't depend on it, though. Rare. Usually that infrequent type of propagation is more like 100 miles.

From what I understand the theoretical(?) distance is 70 miles due to the curvature of the earth (line of sight).

Lots of unknows... Age of coax cable? Length of coax cable? Preamp? Number of splitters involved? Last time antenna connections were checked for oxidation/corrosion? Is the desired station transmitting on a UHF or VHF frequency (most of the big old antennas like our grandparents used were VHF antennas). And then you get into the real technical stuff that is beyond me.

Realistically, I'd be happy with 50 miles as long as no nearby trees or buildings were between me and the transmitter. Also, look at a topo map to be sure there are no hills or mountains that could be putting you in the shadow of the signal, in other words blocking your line of sight between your antenna and the transmitter. I've got one station that is a hair over 50 miles from me that I have given up on due to a hill about halfway between me and that transmitter (20-25 miles distant). My antenna setup is far from optimal...actually it is really close to the ground. But, I can receive a mid-UHF station with my Antennas Direct DB8e consistently with it at about 40 miles. At 30' I figure it would perform much better.

But, again, I think the theoretical distance is 70 miles...or less.

I'm sure some of the antenna experts will give you some good information here, they're very knowledgeable.

Best wishes. It sounds like you've got a project!

Ed

The Coax is brand new RG6, new balun, just put in this past Sunday. No amps of any kind, no splitters, The channel I want is UHF.


Speaking of ideal conditions, the other day I was able to get a channel from Wilmington, that's over 300 miles. It was crystal clear for about 10 minutes, then nothing.
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post #17904 of 17920 Old 09-25-2019, 11:33 AM
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Matthew, the best consistent distance with everything set up the best it can be and having the best weather conditions would be probably 50-60 miles. There's just so far that a dependable signal can reach. How far are your desired transmitters from you.

The 300 mile reception is what is known as "tropo", "tropospheric propagation", "tropospheric ducting"... Google it.

You can even go to this site and see predictions for long range reception... http://www.dxinfocentre.com/tropo.html

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post #17905 of 17920 Old 09-25-2019, 12:34 PM
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Quote:
Originally Posted by Matthew Hawkins View Post
The Coax is brand new RG6, new balun, just put in this past Sunday. No amps of any kind, no splitters, The channel I want is UHF.

Speaking of ideal conditions, the other day I was able to get a channel from Wilmington, that's over 300 miles. It was crystal clear for about 10 minutes, then nothing.

Post a link to your Rabbitears report and maybe we can help you.

https://www.rabbitears.info/searchmap.php
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post #17906 of 17920 Old 09-25-2019, 07:16 PM
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Originally Posted by Matthew Hawkins View Post
The Coax is brand new RG6, new balun, just put in this past Sunday. No amps of any kind, no splitters, The channel I want is UHF.


Speaking of ideal conditions, the other day I was able to get a channel from Wilmington, that's over 300 miles. It was crystal clear for about 10 minutes, then nothing.
What UHF channel are you trying to receive? With a proper antenna and amplifier, you may be able to receive Charlotte, Greenville-Spartanburg, and Columbia markets if you are in York County, SC.
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post #17907 of 17920 Old 10-10-2019, 02:00 PM
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Originally Posted by MAX HD View Post
Quote:


Originally posted by Ken H
99.44% of the time, the following apply:


- Bigger is better


- Higher is better


- Outside is better


- Directional is better






Ken,you are sooooo right.Thanks for heading up this thread.I'll start it out with one of the best setups for UHF reception...and I've tried 'em all


Lots of pics and nice links for valuable info.

http://community-2.webtv.net/GregBar...rrentUHFTower/

This advice makes me happy as i just purchased the 100 mile range outdoor antenna from channel master and i have a 20' tall mast outside! Cutting the cord!
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post #17908 of 17920 Old 10-10-2019, 02:06 PM
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Quote:
Originally Posted by MAX HD View Post
Quote:


Originally posted by Ken H
99.44% of the time, the following apply:


- Bigger is better


- Higher is better


- Outside is better


- Directional is better






Ken,you are sooooo right.Thanks for heading up this thread.I'll start it out with one of the best setups for UHF reception...and I've tried 'em all


Lots of pics and nice links for valuable info.

http://community-2.webtv.net/GregBar...rrentUHFTower/

This advice makes me happy as i just purchased the 100 mile range outdoor antenna from channel master and i have a 20' tall mast outside! Cutting the cord!

I live in BFE and can get 4 channels with a cheap i door antenna. Regardless what the realistic range on receiving a tea smission is i wanted the biggest
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post #17909 of 17920 Old 10-17-2019, 08:17 PM
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Hi,

I want to modify my Antennas Direct DB2e to get CBS Chicago which is VHF 12 that will look like the attached.

I know I have to cut the Aluminum wire rod to length, hammer the end flat then drill a hole to mount it.

How long should each of the rods be and what diameter?

If the frequency is 207MHz, I'm guessing the length s/b 28.5" on each side.

Like to get as exact as possible.

Is this close or ?

Thanks!
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post #17910 of 17920 Old 10-18-2019, 12:25 PM
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Quote:
Originally Posted by ncsercs View Post
Hi,

I want to modify my Antennas Direct DB2e to get CBS Chicago which is VHF 12 that will look like the attached.

I know I have to cut the Aluminum wire rod to length, hammer the end flat then drill a hole to mount it.

How long should each of the rods be and what diameter?

If the frequency is 207MHz, I'm guessing the length s/b 28.5" on each side.

Like to get as exact as possible.

Is this close or ?

Thanks!
I wonder how you came to the conclusion that the length should be 28.5 in on each side?

It looks to me like the VHF element is just a simple dipole. If that is the case you could calculate the length using the dipole antenna calculator at: https://www.translatorscafe.com/unit...ipole-antenna/

It will give you the total length of the dipole element as well as the length of each leg. It also takes into account the diameter of the rod or tubing you are using.

For example, using a 1/4" diameter element, the overall length would be 2.29 ft (27.48 in) and each individual leg would be 1.15 ft (13.8 in) for a frequency of 207 MHz.

Of course I may be completely wrong so let's see if others weigh in on the matter.
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