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4 posts • Page 1 of 1
I live in zip 20832. I'm no more than 20 miles from my primary stations that run from channel 7-50. I'm looking for a low profile antenna for outside or an attic install.
I will be feeding a dual tuner HD Homerun so I will need to use one two way splitter with a main cable run of 25-40 feet either way.
I was thinking of either a 7694P in the attic or a GS2200 outside. I assume I would also need a preamp at least for the 7649P.
Your recommendations would be appreciated.
Also I would really be interested if someone could provide a signal math example. Something like:
Expected incoming signal strength / 50% for attic + antenna gain + pre-amp gain - cable loss - splitter loss = signal at input.
Since your TV stations are less than 20 miles from you I would suggest the HD7694P antenna in the attic. The GS-2200 antenna could give you too much signal since it has a built in amplifier gain of +18dB which multiples the incoming signal by 8 times. This could actually give you too much signal for the TV tuners to handle. Also the GS-2200 antenna is bi directional on the VHF band (channels2-13) so depending on the buildings, trees, etc around you we could get signal bouncing the back of the antenna and confuse the digital tuner with multiple signal.
Example of system losses would be as follows but we have to make some assumptions on signal levels.
Starting with a signal level of 18dBmV or 8000 microvolts (-30.0dBm) of actual signal outside you loose 50% (-6.0dB) so now your starting signal in the attic is 12dBmV or 4000 microvolts to start with. If the antenna gain is 10dB (3X) we now have 22dBmV or 12,000 microvolts at the antenna. Now we have to figure our losses. Cable loss is figured at an average of 6.0dB of loss per 100 feet for UHF. Splitter loss is figured at an average loss of -4.0dB.
+22dBmV at the antenna
-cable loss from the antenna to the splitter (unknown for this example)
-4.0dB loss of the splitter
-2.4dB cable loss for 40’ of cable at 6.0dB per 100’ for the longest leg off the 2 way splitter going to a TV set
+15.6dBmV is our signal at the TV set
With the +15.6dBmV (approximately 6000 microvolts) you will not need an amplifier in this example. I suggest that you try your system without an amplifier. If you should require a amplifier then use the HDA-100 ahead of your 2 way splitter.
One more clarification.
I will be splitting the signal after the 40' run. After the splitter are two ~3' cables feeding the two inputs on a HD Homerun box. So if I understand.
18dBmV assumed outside signal strength
- 6 dBmV for attic loss = 12 dBmV at antenna
+ 10 bB (x3) antenna gain = 22 dBmV
- 2.4 dBmV cable loss (40 ft.) = 19.6 dBmV to splitter
- 4 dBmV splitter loss = 15.6 dBmV signal to tuners
So the end result is the same.
I have two remaining questions. What is the difference between a pre-amp and a distribution-amp in Winegard parlance? When I think of a distribution amp, I usually think multiple outputs (Broadcast TV Background). It also seems as though the pre-amps are capable of being mounted to the mast outdoors while the distribution amps are meant for indoors and can be mounted either near the antenna or near the receiver and have the ability to be powered directly without an injector.
Is the HDA-200 a reasonable choice? I like the option of the adjustable gain but I am slightly confused by the trap, negative gain and some of the other specs.
You are correct about where the amps are meant to be mounted. Yes, both the HDA-100 and HDA-200 may be powered with the supplied power inserter if a power source is not near where the amp will be located or they can be directly powered. Although amplification is probably not necessary in this application, both the HDA-100 and HDA-200 would be a reasonable choice if signal amplification is needed. The HDA-200 offer more flexibility with the gain control. It also features an FM trap to filter out unwanted FM signals. FM signals reside right between low band VHF TV signals and High band VHF TV signals. If there is a very powerful FM station in the area, sometimes it can disrupt the digital tuner and must be “trapped” out to avoid this. In this case though, the HD7694P antenna automatically rejects the unwanted FM. The return path specs are for cable TV systems.
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