Which VHF-Hi ONLY antenna or other solution?

[balm]

i repositioned the #13 yagi, to put it further out in front of the tower, im receiving #13 now about 80% of the time , but with frequent drop-outs (with no amplifier - kitztech is repairing it)

ive tried the join-tenna for #13, and one for #8, in neither case did they help, it did not seem to reduce the strength on #8, so ive given up on the join-tennas

now i have to decide if i should try the expensive Tin-Lee filter, to reduce #8, and UHF

the Zinwell ZAT-720 converter improved reception greatly on all channels, more stable (locks on 3% - 30% on the quality meter)


however all my 2nd edge channels are subject to interference when the lake is busy with motor boats, i havent found a way to lessen this yet...

[resago]

you could try moving your antenna to the other side of the tower, perhaps on an eight foot pole, centered through the tower. You may have the 13 ant. in a dead spot. With me, 3 feet made a huge difference in getting my trouble ch13 to come in.

[balm]

before deciding on a $200 Tin-Lee filter, im not sure if i also need to block #23, #38,

as im not sure if the strong UHFs are interfering with the weaker UHFs and the weak#13 VHF


is there a way to know for sure if say #38 is interfering, or overloading the TV tuner (the bandpass filter is very expensif)


tvfool: http://www.tvfool.com/?option=com_wr...9e7445a6fd57f8

[ScaryBob]

I doubt that 38 is causing any interference or overloading. Channel 8 is a more likely suspect since it can create intermodulation harmonics across the UHF band. I have a similar situation here with channel 10.

[majortom]

is there a way to know for sure if say #38 is interfering, or overloading the TV tuner (the bandpass filter is very expensif)

I would have to agree with Scary. One quick test ya might try is:
1.) take note of existing ch 13 quality. However ya can measure it, PC card, TV Tuner's indication, so on.
2.) add a fixed amount of attenuation in line at the tuner. Attenuator, another 2 way, 4 way splitter, whatever.
3.) If there is absolutely no difference in the quality with the added attenuation, you can say the signal was already degraded before it hits the tuner and ur not overloading there.

U could then try a similar test up top, but place the attenuation at the input of the preamp (unless ur not using one).
Again, if there's no difference in Quality with the extra attenuation ya might conclude the signal already degraded before it hits ur preamp.

[balm]

thanks

ive done this using a/b test, without amplifier, and didnt notice any change, other than i tend to completely lose #13 with 6db attenuator

previously with amplification, and a variable attenuator, it helped #13

[majortom]

If u completely lose it with an extra 6dB Attenuator, then I think it's safe to say ya just don't have quite enough signal strength and your limited by the noise floor. A good thing, should be easier to come up with a little extra signal with better antenna placement, a better antenna, or both...

[balm]

yes, i might add another 2 elements, i receive #13 now most of the time, but it still comes and goes at any given moment, with huge instantaneous swings on the signal quality meter making viewing a very frustrating experience

can wing from 0 to 30% quality (back & forth) in a matter of seconds


i might just dig into my "patience", and wait to see what happens after co-channels drop in power (after August 31)

[majortom]

hmm, sudden swings, if they're real brief might be some nearby electrical noise?
Are you in an a new or old neighborhood, urban, suburban or rural?
Do u see like a tearing line thru the picture?

[balm]

its old cottage country, on a point, on the river bank, all cottages/homes are within 60 ft of one another, private road runs up the point, fair amount of daytime boating activity, nighttime reception improves dramatically,

on digital i dont see much other than pixel blocking, sometimes in a mostly horizontal pattern

on some analogs, we have vertical scrolling, with some regular, repeating popping noise

i tried a Home Depot power noise filter with 45 db EMI reduction on 100 khz, but nothing improved

all cottage was rewired last year with grounding

[ScaryBob]

Sudden wide swings can also be caused by aircraft. The effect will be a repeated swing that varies in speed, depending on aircraft location. A single sharp dropout is more likely to be noise from something like a motor switching off. Ignition noise from small motors could also be an issue. Not much can be done about those except get lots more antenna height. If extra height cause problems due to overloading, a filter would be the best bet.

[balm]

across the river we have a regional airport, about 3 miles away, but i never really see any aiplanes low ovehead, also its in the opposite direction

[balm]

im redesigning my channel 13 DIY yagi,

this time i would like to use 1" square aluminum tubing spine, and put 1" diameter schedule40 pvc as stand-off supports to hold the elements. I would screw the supports onto the top of the square tubing, then the elements would be screed on top of the supports

im not sure if i need to use a boom correction factor on the elements to account for the metal spine, even though the elements will be insulated from it,
and if i dont, how much am i compromising performance?

obviously im constructing like this for speed


thanks

[ScaryBob]

The airplane "flutter" effect is usually caused by large commercial aircraft at a fairly high altitude. Think of it as a fast moving tropo reflection that goes in and out of phase. I suspect that lower flying smaller aircraft would also have an effect but they would need to be made of metal. A low flying aircraft that crosses the signal path could cause a very brief, rapid signal fluctuation.

[holl_ands]

Originally Posted by balm

its old cottage country, on a point, on the river bank, all cottages/homes are within 60 ft of one another, private road runs up the point, fair amount of daytime boating activity, nighttime reception improves dramatically,

on digital i dont see much other than pixel blocking, sometimes in a mostly horizontal pattern

on some analogs, we have vertical scrolling, with some regular, repeating popping noise

i tried a Home Depot power noise filter with 45 db EMI reduction on 100 khz, but nothing improved

all cottage was rewired last year with grounding

Two-stroke engines (e.g. boats, motorcycles, old lawn mowers) use magneto ignition systems,
which are notorious generators of Impulse Noise: [Raise an EMI "fence" to protect your antenna?]
http://www.newscientist.com/blog/las.../on-blink.html
http://www.docstoc.com/docs/24267475...e-MZ202-engine

Not much you can do about it unless you can encourage them to change over to 4-strokes,
which are more likely to be using an EMI suppressing (e.g. transistor) ignition systems:
http://www.marineenginedigest.com/sp...sus4stroke.htm
http://marine.honda.com/Products/modeldetail/BF2

Some lakes outlaw conventional 2-stroke engines due to their high pollution:
http://www.trpa.org/default.aspx?tabid=349

Note that Lake Tahoe does allow direct fuel injected 2-stroke engines.
However, Evinrude E-TEC Engines still use a magneto....there are reports re EMI on 27 MHz:
http://www.marineenginedigest.com/pr...nrude/etec.htm

And in smog-plagued Southern California, 2-stroke lawnmowers are also banned....

There is a fairly new (2010) SAE J551-1 Standard re Electromagnetic Compatibility
levels allowed in vehicles, boats (up to 15-meters) and machines:
http://standards.sae.org/j551/1_201006/
The SAE J551 predecessor is dated 2000.
There is also an IEC CISPR-25 Standard, dated 2008.
Unfortunately, they cost more than a few bucks to order a copy....no thanks....

IEC CISPR-12 Standard is an older predecessor, original 2001, last updated 2007:
http://www.emclabinfo.com/precomplia...Bed5.0%7Db.pdf
Figure on pg17 depicts the allowable radiation levels, measured at 10-meter distance:
34 dB(uV/m) for 30-75 MHz (Lo-VHF TV Band)
45 dB(uV/m) for 400-1000 MHz (UHF TV Band)
Linear scale in-between (Hi-VHF TV Band)

These limits are intended to protect Radio equipment ON THE BOAT and are very good.
FCC OET-69 presumes DTV needs 28 dB(uV/m) for Lo-VHF and 36 dB(uV/m) for Hi-VHF.
[A ten-fold increase in distance to 100-meters results in a 20 dB reduction in Field Strength.]

So TV reception on a nearby shore should NOT be affected by boats meeting this Standard.
So, over time, the situation SHOULD improve as the older boats retire.....or sink....

BTW: In Taiwan several years ago, one particular brand of Arc Welder was found
to be generating an extremely high level of radio interference. The manufacturer
was forced to not only recall, but also beat a path to the door of non-responders
in order to install a mod kit....on thousands and thousands of offending units.

I can see it now....the EMI Police (e.g. FCC) gets aggressive in finding, fining and
shutting down Man-Made Radio Noise sources.....