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post #61 of 153 Old 10-03-2012, 10:32 AM
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There's an insertion loss of the bandpass filter that might be dropping your signal strength below an acceptable level. It varies from one unit to another. It has been a long time since I seriously experimented with UHF jointennas on a bench, but I think the insertion loss of the bandpass path commonly varied from about 2 to 5 dB.

The other thing is, the band reject filters aren't very narrow, and the channel 23 band reject circuit could attenuate channel 20 on the thru path, and the channel 20 filter's reject circuit could reject the channel 23 on its thru path, so it is important to couple the weaker, problematic signal last in a string of jointennas. You might also benefit from lightly amplifying the channel 23 lead by 10 to 12 dB before inserting it into a filter, but whether you can get away with doing that will depend on the relative strength of the other signals coming off that line. If you only have a 15 to 20dB amplifier available, you can use it to preamplify the channel 23 line, but if you do, you might need to "double up" your two channel 23 Jointennas, using the first one on the preamplifier output just as a bandpass filter and using the second one for coupling.

Do you have a TV fool plot we can look at?
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post #62 of 153 Old 10-07-2012, 08:49 AM
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AntAltMike

Thanks again for taking an interest in my problem. I will try to address the issues you raised in your last post. I do have a TVFool plot for my location but I do not know how to send it to you. I can tell you the results. Most of the stations I watch are located to the east which I receive by diffraction due to a ridge between me and the transmitters. Two of these are VHF stations which I receive on an upper band VHF antenna. The signals from the UHF antenna and the VHF antenna are combined through a CM-7777 amplifier. However, I also have two UHF stations located to the north which I receive by line of sight. One of these, channel 20, is so strong that I can receive it on my UHF antenna pointed east. The other, channel 23, is strong but needs an antenna pointed north.

In my last test of the channel 23 jointenna I used an antenna pointed north connected to the CM-7777 amplifier. The channel 20 jointenna was not connected. I tuned my TV to channel 23 and had a good signal. I then inserted the channel 23 jointenna right at the TV set, and got no signal. Does this information give you any ideas as to why it doesn't work?
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post #63 of 153 Old 10-07-2012, 12:17 PM
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Quote:
Originally Posted by rptr View Post

I do have a TVFool plot for my location but I do not know how to send it to you.

I think this site requires that you have made five posts before it will let you post the hyperlink to your TV fool plot, but your next post will be your fifth.
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post #64 of 153 Old 10-07-2012, 12:21 PM
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You might try using one channel 23 Jointenna as just a bandpass filter, between the antenna and the preamplifier input, and then, if that preamp output is tunable by your TV, then couple the preamp output into your other antenna line using your other channel 23 jointenna.

What is the published gain of your CM7777? It has been mentioned here that newer Channelmaster preamps have different electronics and different gain figures than do earlier units bearing the same model or part numbers.
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post #65 of 153 Old 10-16-2012, 08:17 AM
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AntAltMike

I have the old model of the CM-7777 which has separate inputs for VHF and UHF. It has a gain of 26dB on UHF. I did not understand why you are suggesting to use both channel 23 jointennas. Neither one will pass the channel 23 signal on the channel 23 input. Can you explain why that is happening? Thanks again for for your interest and suggestions.
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post #66 of 153 Old 10-16-2012, 11:16 AM
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Actually, both of them "pass" the channel 23 signal if they did so when Channel Master tested them and if no one has subsequently attempted to retune them.

It is possible for a TV to work when connected to a signal that has passed through a working filter when insertion loss drops that signal below the minimal level needed by the tuner, or when preamplification has degraded it. It is actually easier to deal with the problem of an anemic digital signal because, since preamplifiers all have lower noise figures than do digital TV tuners, a weakened digital signal can be "rescued by "post preamplification" after it comes out of a bandpass filter.

Since you have the two filters and a preamp on hand, you need to just try this and see how it does. If it doesn't work, then the next step would be to try pre and post amplification combinations using a lower gain amplifier.

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post #67 of 153 Old 11-08-2012, 05:46 PM
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Good news. I solved my channel 23 Jointenna problem by buying an Antenna Signal Injector from Tin Lee. It does the same job as the Jointenna. I just connected it to the antennas and it worked. I can now get all the channels from the two antennas.


AntAltMike

Thanks for your interest and all your advice.
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post #68 of 153 Old 11-09-2012, 09:05 AM
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rptr,

If you're interested, I can check out the ch23 Jointenna to see what was wrong with it. Sorry, missed your previous posts or I'd have offered to check it sooner. Shoot me aPM if you're interested.

BTW, how much did the TinLee injector cost? Just curious since we often run into oddball channel locations when talking to customers.

Cheers!

Tech support for Antennas Direct
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post #69 of 153 Old 04-15-2015, 09:26 AM
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Are there any opinions as to whether Jointennas should be used before or after signal amplifiers? I have always used them after amplification.


In my particular case I would like to wire a single secondary antenna through a preamp, then power inserter, then a splitter and into two single channel inlet ports on two separate Jointennas (in parallel), then have the primary antenna (also post preamp, post power inserter) come through the common ports of both Jointennas (in series).


If I recall correctly jointennas are power passive.
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post #70 of 153 Old 04-15-2015, 09:30 AM
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Quote:
Originally Posted by ADTech View Post
rptr,

If you're interested, I can check out the ch23 Jointenna to see what was wrong with it. Sorry, missed your previous posts or I'd have offered to check it sooner. Shoot me aPM if you're interested.

BTW, how much did the TinLee injector cost? Just curious since we often run into oddball channel locations when talking to customers.

Cheers!
I was quoted $100USD for a 1 channel and $120USD for a 2 channel. Doesn't include shipping. I was debating picking 1 or 2 up next time I was up in Toronto to save shipping....
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post #71 of 153 Old 04-15-2015, 10:38 AM
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Originally Posted by bigdaveyl View Post
I was quoted $100USD for a 1 channel and $120USD for a 2 channel. Doesn't include shipping. I was debating picking 1 or 2 up next time I was up in Toronto to save shipping....
You'd better call ahead and prepay, because I doubt they have all models in stock.
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post #72 of 153 Old 04-15-2015, 10:44 AM
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Originally Posted by AntAltMike View Post
You'd better call ahead and prepay, because I doubt they have all models in stock.

I don't think they have anything in stock. AFAIK they custom build everything.
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post #73 of 153 Old 04-15-2015, 10:51 AM
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Quote:
Originally Posted by OTAzak View Post
Are there any opinions as to whether Jointennas should be used before or after signal amplifiers? I have always used them after amplification.


In my particular case I would like to wire a single secondary antenna through a preamp, then power inserter, then a splitter and into two single channel inlet ports on two separate Jointennas (in parallel), then have the primary antenna (also post preamp, post power inserter) come through the common ports of both Jointennas (in series).


If I recall correctly jointennas are power passive.

If you order from Tinlee I think you can get DC pass wherever you want. Inexpensive splitters that pass DC on one port are available.

The preamp should be first if at all possible because anything between the antenna and the preamp adds loss, which either lowers the effective antenna gain or increases the system noise figure, depending on how you view it.

I think the use of two antenna joiners as you described above is shown in my diagram below. This will work. Otherwise you can put one power inserter just before the TV and you'll need DC pass on the proper device ports.
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post #74 of 153 Old 04-15-2015, 10:53 AM
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Originally Posted by Calaveras View Post
I don't think they have anything in stock. AFAIK they custom build everything.
This is true, I believe. They could custom build any 1 or 2 channel inserter. That would make sense because they say no returns/exchanges unless unit is defective.
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post #75 of 153 Old 04-15-2015, 12:35 PM
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Quote:
In my particular case I would like to wire a single secondary antenna through a preamp, then power inserter, then a splitter and into two single channel inlet ports on two separate Jointennas (in parallel), then have the primary antenna (also post preamp, post power inserter) come through the common ports of both Jointennas (in series).
Why? What is the advantage of using two jointennas to insert the signal from the second antenna twice?

If you can not measure it, you can not improve it.
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post #76 of 153 Old 04-15-2015, 01:34 PM
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Quote:
Originally Posted by rabbit73 View Post
Why? What is the advantage of using two jointennas to insert the signal from the second antenna twice?

Sorry this wasn't clear, they would be inserting two different UHF channels, about 12 channels apart (and roughly 30 deg. angle separation). Figured a splitter is cheaper and easier than setting up a third antenna.
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post #77 of 153 Old 04-15-2015, 04:59 PM
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Oh, OK. That might work using a splitter in reverse as a combiner.
Google search for join tenna schematic:

https://www.google.com/search?q=join+tenna+schematic&biw=1093&bih=420&tbm =isch&tbo=u&source=univ&sa=X&ei=S-ouVfjwFfiUsQSj6ICoBQ&ved=0CDEQsAQ

What channels are you talking about? Is this pretty close to your tvfool report?
http://www.tvfool.com/?option=com_wr...f1f0147309a88d

This is the way Channel Master does it:



http://www.warrenelectronics.com/Antennas/Jointennas.htm

And this is another way, using a splitter in reverse as a combiner:



http://webpages.charter.net/themanny/ota.htm

Quote:
If I recall correctly jointennas are power passive.
Maybe one way, but not the other:

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post #78 of 153 Old 04-16-2015, 06:44 AM
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Rabbit, thanks for your reply. I have seen the basic diagrams on the Warren Electronics site but had not seen the second schematic (although they never show where a signal amplifier could or should be introduced - if an amplifier overcomes the ~ 12.5 bandstop then I suspect there could be issues).


In my case I want to receive RC 22 and RC 34 from the north, and have an RC 22 jointenna and a second UHF jointenna that I hope to retune to 34. Most of my stations are southerly as the TV report indicates. If this is not feasible the loss of RC 34 isn't very significant. I had hoped to get these off the (primary) antenna backside but have been unsuccessful so far just via aiming of the main antenna.


Thus my question above - split a single antenna input through two jointennas using a splitter. I had not thought about using a combiner on the bandstop side.

Last edited by OTAzak; 04-16-2015 at 06:49 AM.
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post #79 of 153 Old 04-16-2015, 09:29 AM
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Quote:
Originally Posted by OTAzak View Post
Are there any opinions as to whether Jointennas should be used before or after signal amplifiers? I have always used them after amplification....
If I recall correctly jointennas are power passive.
Quote:
Originally Posted by rabbit73 View Post
Maybe one way, but not the other:

I just popped the cases open on an 0579 channel 9 VHF Jointenna and an 0585-1 UHF Jointenna pre-tuned to channel 28.

That schematic above is for a VHF Jointenna, which does not pass power through its single antenna port. The UHF 0585-X Jointennas DO pass power to all ports. I just measured zero resistance from TV Set to All Channels, and 0.5 ohms from TV Set to Single Channel. I am not able to estimate their current carrying capability of the Single Channel circuit, as those current bypass inductors are wound with awfully tiny wire, but they surely can carry whatever amount of current a single preamplifier draws. FWIW, the TV to All Channels path can carry enough current to light a Christmas tree,

In fact, the drawing is either a Low Band Jointenna or a very old one. The channel 9 High Band Jointenna I am looking at right now was likely made in this century, and it has tiny trimmer inductors in series with each of the shunt capacitors. I have not yet experimented with them to see what their tuning range and effects is.

About a decade ago, I opened and examined some low band Jointennas whose packages I had to wipe the dust off to read, and they did not have similar, trimmer inductors. I have no way of knowing whether those trimmers are a modern addition or an inherent design difference between the low band and high band units.

The two big inductors on the VHF Jointennas are wound around the same threaded non inductive core, meaning they function as an air core transformer. Curiously, that core is threaded and slotted and can be turned, but turning it accomplishes nothing electrically, so it was probably used just because it was a readily available item that neatly supports those heavy gauge four turn coils.

On the UHF Jointenna, the similarly circuited inductor coils that also interact to function as a transformer are free standing and appear to have been hand optimized by poking at them. There are also multiturn inductor screw slugs that move the pass band and reject notch through the entire designated ranges of channels 14-30 (0585-1), 31-49 (0585-2), and presumably 50-69 (0585-3), but I don't have an 0585-3 available to test. FWIW, when I adjust those inductor slugs to change the UHF Jointennas from one channel to another, I see no effect of a metal, inductive screwdriver of their performance. Similarly, I could tune the slugs on the old, Tru-Spec BPFs with an ordinary, 1/8" magnetic screwdriver as well.

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post #80 of 153 Old 04-16-2015, 01:58 PM
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OK, I think I got it. Chuck's diagram is correct, if you can keep the power inserters in the places indicated. If you want a power inserter after the second jointenna and just before the TV instead, then it must be able to provide enough current for both preamps, and the jointennas and splitter must be able to pass the current.


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post #81 of 153 Old 04-16-2015, 03:50 PM
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Quote:
Originally Posted by OTAzak View Post
In my case I want to receive RC 22 and RC 34 from the north, and have an RC 22 jointenna and a second UHF jointenna that I hope to retune to 34. Most of my stations are southerly as the TV report indicates. If this is not feasible the loss of RC 34 isn't very significant. I had hoped to get these off the (primary) antenna backside but have been unsuccessful so far just via aiming of the main antenna.
This is your tvfool report for your estimated location

You never did post your tvfool report AFAIK, so I hope my estimate of your location is close enough.

I think you can make it work, but I see a few potential problems ahead. I understand your desire to amplify the signals before the jointennas to compensate for their insertion loss. But, since your signals from the north and from the southwest are already very strong, there is a good chance that the preamps will be overloaded which will create spurious signals in the preamp from IMD that will wipe out your weakest desired signals.

There a few ways you can deal with that problem. You can try just the CH 22 jointenna first without any preamps, you can select a preamp that can tolerate very strong signals, or you can insert an attenuator between the antenna and the preamp input for a compromise between those two extremes that will provide just enough amplification without creating enough overload to damage your weakest desired signal. I favor the first choice as a test.

CH 22 is going to be a lot easier than CH 34, in spite of the fact that CH 22 is 26.5 dB weaker than WSFB on CH 33.

CH 34, WTXX-LP digital virtual 34.1 has co-channel interference (if tvfool is correct) from WTXX analog that is 7.3 dB weaker, co-channel interference from WESA analog that is 15.1 dB weaker, adjacent channel interference from WFSB on CH 33 that is 37.7 dB stronger, and adjacent channel interference from WVIT on CH 35 that is 27.1 dB stronger.

If you can not measure it, you can not improve it.
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post #82 of 153 Old 09-19-2015, 12:58 PM
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Coming back to this subject after a long absence -- is anybody making new Join-Tenna equivalents? (I have a multi-antenna setup that works great, thanks to a Channel 49 Join-Tenna; now trying to help a friend, and hoping my Join-Tenna holds up.)
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post #83 of 153 Old 09-19-2015, 01:10 PM
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Originally Posted by wildwillie6 View Post
Coming back to this subject after a long absence -- is anybody making new Join-Tenna equivalents? (I have a multi-antenna setup that works great, thanks to a Channel 49 Join-Tenna; now trying to help a friend, and hoping my Join-Tenna holds up.)
Tin-Lee in Canada makes a superior device to the Join-tenna called an "AC7". I got a quote from them a week ago, and it's $170.00 U.S. http://www.tinlee.com/MATV_headend.p...IGNALINJECTORS

I don't think I want to spend that sort of money for one channel, no matter how badly I want it. That's about twice what it's worth.

Note: that's the price quote to ME, one for you might be a bit cheaper, or may be more expensive. They do not have fixed prices, and must quote everything you might want to buy from them individually, as it's all customized to order.

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post #84 of 153 Old 09-19-2015, 02:54 PM
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I got a quote from them a week ago, and it's $170.00 U.S. http://www.tinlee.com/MATV_headend.p...IGNALINJECTORS
I see -- priced more for headend operators than home hobbyists.

The other solution for my friend is a DVR with two antenna inputs, but I guess they're rare (rare like a unicorn).
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post #85 of 153 Old 09-19-2015, 03:24 PM
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I see -- priced more for headend operators than home hobbyists.

The other solution for my friend is a DVR with two antenna inputs, but I guess they're rare (rare like a unicorn).
Well, there is also pulling another full coax line up to the antennas, and using an "A-B switch" type device to switch between separate antennas. Not very useful for DVR's, but it could be done. SOME people can even get away with using a 2-way splitter backwards, but that has less of a chance to work out successfully for most of us, due to various OTA voodoo reception stuff.
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post #86 of 153 Old 10-01-2015, 10:52 PM
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I discovered a UHF Jointenna device on Ebay, which is manufactured in Slovakia for their DVB-T system. However, it really only cares about the particular frequencies it's tuned for, as it's a bandpass/bandstop combiner. We just give them that info, and they set it. Their tv system is UHF only, so I'm unsure if they can provide VHF versions (I didn't ask this as I don't need a VHF one at this time). I've been in contact with the seller, and he said we can order one of these and provide a note before paying with this info:

Quote:
Standard US 75 ohm F connectors
Input 1 (DC PASS or not?) U.S. Ch 14...51 (470...698MHz for UHF) (Note: this range is equal to their systems channel 21 through 49)
Input 2 (DC PASS or not?) U.S. Ch (lower edge freq.)...(upper edge freq.) for instance: CH 46 (662...668MHz) This is for the antenna pointed at the single channel you want that doesn't come in on the other antenna
NOTE: DC PASS is needed, IF you intend on powering a preamp between the antenna and this combiner. Could be useful if these channels are very weak.

U.S. UHF channel frequency listing:

https://en.wikipedia.org/wiki/North_...ncies#UHF_band

INPUT 1 = The 'all-channel' antenna minus the channel on input 2
INPUT 2 = The 'single channel' antenna minus all the other channels on input 1
OUTPUT = combined input 1 and input 2 to tv set.

$19.90 US which includes shipping!

http://www.ebay.com/itm/121758149132...%3AMEBIDX%3AIT

Home URL: http://www.antenne-komponenty.eu/eng...zlucovace.html



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post #87 of 153 Old 10-02-2015, 01:15 AM
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There used to be a cheap 4-input, user tunable filter bearing the label Tru-Spec, models MX-4V and MX-4U that could be had for under $30, but it didn't have any band-stopping in it. I bought a lot of about 30 of them on eBay a decade ago for a song, but you'll never find them in quantity any more. They stopped making it in the early 1990s. I still have a few but I'm not willing to sell them.

(Edited by AntAltMike to remove spam image that had been substituted for linked image)

The manufacturer of the antenne-komponenty product is hardly making any money on them, so I would advise making your first purchase order for one tuned in European frequencies. I doubt that they will be narrowing the passband width for you even if they agree to "center" the pass and reject bands to North American channel frequencies.

Here is what they are used to using for a channel plan:

CH# Vis carrier Aural carrier
21 471.25 477.75
22 479.25 485.75
23 487.25 493.75
24 495.25 501.75
25 503.25 509.75
26 511.25 517.75
27 519.25 525.75
28 527.25 533.75
29 535.25 541.75
30 543.25 549.75
31 551.25 557.75
32 559.25 565.75
33 567.25 573.75
34 575.25 581.75
35 583.25 589.75
36 591.25 597.75
37 599.25 605.75
38 607.25 613.75
39 615.25 621.75
40 623.25 629.75
41 631.25 637.75
42 639.25 645.75
43 647.25 653.75
44 655.25 661.75
45 663.25 669.75
46 671.25 677.75
47 679.25 685.75
48 687.25 693.75
49 695.25 701.75

They are passing 3MHz above and below those limits, so they can be matched up with any UHF, FCC broadcast channels. Your biggest problem may be with the bandstop section degrading a desired alternate channel. That potential problem can be mitigated by selecting the European channel to the side "away" from the alternate desired channel.
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post #88 of 153 Old 10-02-2015, 05:10 AM
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This new find might be exactly what I need. I'm trying to combine two separate antennas to get different markets. Here is a chart I made with the two markets color codes. Yellow = Antenna 1 Blue = Antenna 2. The blue channels are all non-negotiable. I realize I might have to sacrifice WYFF to make this work.

Would this new device Primestar31 found work for me, or would I be better off paying the Canadian company to build something custom?

How should I ask them to configure it? The above US vs European debate makes sense, but is confusing to me. Looking for expert guidance!
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post #89 of 153 Old 10-02-2015, 06:35 AM
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Quote:
How should I ask them to configure it? The above US vs European debate makes sense, but is confusing to me. Looking for expert guidance!
What does your linked tvfool report look like? We need to see the azimuth which your image doesn't give. It has to do with beamwidth.

The adjustable panel 8-bays aren't any better than combining from two different directions than two 4-bays. Sometimes it works, sometimes not. According to ADTech, who works for Antennas Direct and was in on the design and testing of the DB8E, it works best when the two directions are at right angles, 90 deg apart.

If you can not measure it, you can not improve it.
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post #90 of 153 Old 10-02-2015, 09:00 AM
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Originally Posted by rabbit73 View Post
What does your linked tvfool report look like? We need to see the azimuth which your image doesn't give. It has to do with beamwidth.

The adjustable panel 8-bays aren't any better than combining from two different directions than two 4-bays. Sometimes it works, sometimes not. According to ADTech, who works for Antennas Direct and was in on the design and testing of the DB8E, it works best when the two directions are at right angles, 90 deg apart.
Here is my TVFool.

I've basically abandoned the DB8E idea and am looking at just using two regular antennas. Most likely another 8-bay like the one I have (see my other thread). My plan is to point one at 83 degrees to pick up the Blue Stations (Antenna #1 ). Antenna #2 would point towards 283 degrees (WHNS) which would put it near the two weakest stations I'm trying to pick up on the other side.

Ideally I'd like to use one of the devices Primestar31 found to cut down on the interference between the two, but I realize that will mean sacrificing WYFF most likely.

Right now with one antenna pointed at 83 I pick up all of the Blue channels, and traces of the Yellow ones coming off the back side.
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