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Discussion Starter · #1 ·
Hi Ya'll,

Been working on a problem and would like some input.

Currently I have a CM3018 (VHF/UHF/FM) mast mounted with a CM3041DSB Pre-Amp with rotor. There's this one station that I'm having difficulty locking in on being broadcast on frequency 59, whose tentative channel designation after the shutdown is 36. My tuner picks it up but only shows, at best, one bar and often the signal breaks up (pixalation, freezing, sound loss, etc) or completely drops out.

I'm thinking on getting a CM4228 and a CM7777, mount the 4228 either above or below the 3018 and hook the 3018 up on the vhf input on the 7777 and the 4228 on the uhf input.

Will it work?

My reasoning is this; the 3018 would supply me both the low and high band vhf and the 4228 the uhf which in turn should help me to bring in the troublesome station. And when analog shuts down I should be able to eliminate the 3018 and rely upon the 4228 to get me 13.


I'm not sure how to copy and paste the AntennaWeb results all neat and tidy but if you put down 28791-1610 in the zip code and 300' for the height the results will show the offending station; wyff-dt in the purple range.


Thanks.
 

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Discussion Starter · #3 ·
Or should I maybe consider doing away with the 3018 and get a 'bigger' antenna such as the Winegard HD7082P?

What about the Pre-Amp?


In researching this stuff it gets kind of confusing!
 

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disagree on the antenna choices.


Prefer the antennas direct 91xg for that application since it has great response on the upper uhf channels, is very light, very directional, tames multipath, and stacks nicely.


with the 91xg, there is a 2-4 improvement in dbd gain across the uhf spectrum over the cm3018. the cm3018 has a range in the 7-10 ballpark versus 9-14 for the 91 xg.


at ch 60 for example, the difference is about 4 dbd between the cm3018 and 91xg. with the cm4228 a little over 2.5 dbd. the 91xg will give you over 1.5 dbd improvement in gain.


The cm 4228 also performs nicely. The largest most important factor at your site would be multipath handling properties where the 91xg has the edge over the cm4228. In this case, the positive gain differences of the cm4228 over the 91xg would have the back seat.


use the cm3018 for vhf/fm and the 91 xg for uhf. I would avoid the cm4228 if there is a hint of multpath (pixelation, up and down signal, dropouts, etc,) as in your case.


if you also want to use the cm3018 for fm, you would not want to amplify the vhf off the cm3018.


you would use separate coax for each antenna and only amplify the 91xg (uhf) with the cm7777. inside you would filter the fm off the tv signal with a winegard ca-8800 tv/fm splitter (only .4 db insertion loss), and combine the unamplified vhf and amplified uhf with a cm0549 vhf/uhf combiner, and then output the combined signal to your distribution system and splitters .


Separate antennas would offer you the best of both worlds and more flexibility.
 

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91XG would probably be easier than the 4228 since you already have the rotor.


But I'm wondering why the trouble with a full power channel 59 @ 16 miles? Must be obstruction or multipath, could even be overload.


But the 91XG should help with that... perhaps try it first without preamp if the run isn't overly long.
 

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I just noticed you are in the mountains and WYFF-DT may be only 392 kW ERP (on 59) which might explain it.


I'd say since you already have the Sammy DTB-H260F tuner, the best thing to try next would still be the 91XG. Perhaps try without preamp (to rule out some oddball overload/interference) if that still doesn't do it then try with the (better shielded) CM 7777. May even want to leave VHF out of the picture until you solve WYFF.
 

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Discussion Starter · #7 ·
See what I mean by confusing!?!?

KenL

When you say WYFF-DT may only be 392 kW ERP are you saying that the signal isn't being broadcast at full power; supposedly 1000 kW? I believe their analog signal is at full power but I could be wrong. So it may be safe to assume that at some point they will eventually broadcast their digital signal at full power?

That said, I may not need to try to wrestle the signal out of the air, just wait for it.

Although, the little bits and pieces of the signal I do get is kinda tainting and there's something in me that wants to take up the challenge.


I hope to streamline my antenna situation once analog drops but if my research is on target, WLOS-DT (broadcasting on 56) will get reassigned to 13 (DTV Tentative Channel Designation) which means I would still need an antenna that can pick up VHF-Hi, hince, the 4228.


With stacking, what kind of spacing should I look for. Should they both be pointed in the same direction or is a 90 degree differential better?
 

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Quote:
Originally Posted by mblrds /forum/post/0

KenL

When you say WYFF-DT may only be 392 kW ERP are you saying that the signal isn't being broadcast at full power; supposedly 1000 kW...

I can't tell for sure from here. It's hard to imagine why you wouldn't be getting it even with a small bowtie @ 16 miles, if it really was 1000kW ERP digital, ordinarily. I have a solid lock on a 50 kW ERP @ 75 miles. Granted it's lower UHF and my terrain isn't as brutal. But others are apparently receiving WYFF-DT (presently) @ 60 miles or more away. STA 392 kW ERP sure isn't peanut power by any means.


So what to do? Well waiting it out will work because channel 36 should prove easier than 59, whatever the final power. But I don't see any downside to a 91XG in the short or longer term, so go for it if you are inclined. It will outperform the 4228 in some aspects, especially channel 59. Possibly even on your eventual upper VHF. It's more directional but you have a rotor. You can see above how easy it is to stack. Either one of those (91XG or 4228) will do better than the CM3018 on UHF.
 

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Discussion Starter · #10 ·
After looking around online I'm just about sold on the 91XG. However the CM7777 is currently out of stock regardless of where you go, until mid Febuary, at least.

Would of liked to order both items at the same time from the same place, minimize shipping cost and all that. Some sites do reccommend a suitable alternative but I don't know if I want to do that.

What to do?
 

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alternatives to the cm7777


cm7778 equivalent to your cm3041dsb

cm7775 uhf only. does not pass vhf

ap8700

ap4700 amplifies uhf passes vhf

ap4800 ditto as above with more gain

ap8275 gain is rather high and risky with short runs. intended for the boonies


Preamp specs.


Channel Master

CM3041DSB UHF/VHF UHF: 23db gain, 2.2 db noise; VHF 16 db gain, 3.0 db noise

CM7775 UHF: 26db gain, 2 db noise

CM7777 UHF/VHF UHF: 26db gain, 2.0 db noise; VHF 23 db gain, 2.8 db noise

CM7778 UHF/VHF UHF: 23db gain, 2.2 db noise; VHF 16 db gain, 3.0 db noise

CM3039 UHF/VHF 13db gain , 3.5 db noise


Winegard

AP4700 UHF: 19db gain, 2.9 db noise

AP4800 UHF: 28db gain, 2.7 db noise

AP8275 UHF/VHF UHF: 28db gain, 2.8 db noise; VHF 29 db gain, 2.9 db noise

AP8700 UHF/VHF UHF: 19db gain, 2.8 db noise; VHF 17 db gain, 2.8 db noise

HDP-269 UHF/VHF 12db gain (high input), 3.0 db noise


My choices would be

AP8700

AP4700

AP4800


The cm7778 is close to your current amp. the cm 7775 will not pass vhf and not a good choice for you. The ap8275 would be ok but the gain is rather high and risky on overload. If you decide on a single input amp you can combine the 2 antennas with a cm0549 vhf/uhf combiner.


february is not too far off. use your current amp for the short term. The 91xg is $20 cheaper at solid signal.
 

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Discussion Starter · #12 ·
I may forego the Pre-Amp and continue to use my current amp.

Thinking I may go ahead and get the 91XG and route it to feed my Sammy h260f and let my current setup feed the cheapo DVD/VCR, which both, in turn, feeds the tv at different inputs.

Depending upon how things go I may not need a Pre-Amp at this time and iffen I do, we'll fine-tune the selection. All this talk about overloading with too much gain and what-not is confusing still!
 

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Quote:
Originally Posted by mblrds /forum/post/0


I may forego the Pre-Amp and continue to use my current amp...

You won't want to use the 3041DSB with the 91 XG. To do so you'd need to bypass the matched PCB balun, which I wouldn't do except to use a 1/2 lambda coax balun, which hopefully isn't necessary here.


Perhaps leave the spartan on the 3018 for analog. As for the Titans, I actually like the 7778 better than the 7777. Same specs as 3041DSB but separate 75 ohm ins and of course shielded like a tank. Can use it as either quasi 7775 or 7776, in "separate" mode with the unused input terminated, which is what I do. Then if in the future you want to try for upper VHF on the 91 XG, you can switch the Titan back to "combined" mode.


I do think it's a good idea to try it first with no pre-amp (most contiguous shot possible of decent quad shield to the DTB-H260F) provided the run is not much more than perhaps 50 feet.

Quote:
Originally Posted by mblrds /forum/post/0


All this talk about overloading with too much gain and what-not is confusing still!

Tell me about it. I have no less than 7 preamps, but the only ones really in use now are the Titans. Those with challenging signal issues end up trying just about *everything* to find what works best in a particular situation. No single solution for everyone. But of course it's worth it in the end to be able to sit down (today) and watch any channel you want, any time you want.
 

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it is unfortunate that the 3041DSB has 300 ohm inputs.


I always felt/thought that the cm 7778 offered Spartan 3 specifications (as the 3041DSB series of amps) in the Titan housing as the cm7777.


that is why I suggested these.

AP8700

AP4700

AP4800


1/2 lambda coax balun...
.
 

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Discussion Starter · #15 ·

Quote:
Originally Posted by KenL /forum/post/0


Perhaps leave the spartan on the 3018 for analog.

What I was thinking. Sorry if my post wasn't clear.

With my current setup I don't believe my Sammy h260f picked up any broadcast in the VHF range. That's why I'm thinking on hooking the 91XG directly to the h260f. I'll have to check again to make sure.
 
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