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Designing custom antenna for my very specific local needs?

2868 Views 23 Replies 9 Participants Last post by  jflarin
This is a question to all the OTA gurus on this forum.

I would like to design custom antenna for my location,
based on the numbers given by tvfool.

The weakest channel I'd like to get is 23 (ION) and for this I'd probably need a preamp.

By looking at the tvfool chart I've come up with a list of frequencies, azimuths and target gains.

My question are:

Are the target gains enough (with /without preamp)?
Are some if target gains to much if I am to use a preamp?
Could I go with less gain on any channel?

Chan	Network	Dist	Path	NM 	azim     target gain
	        (mi)            (dB)	(deg)    (dbi)
20	CBC	19.8	LOS	49.6	50	    0
18	Ind	26.2	LOS	46.7	-50	    0
40		19.8	LOS	44.4	50	    0
44	OMN	20.2	LOS	43.1	50	    0
64	OMN	20.2	LOS	41.6	50	    0
35	Ind	26.2	LOS	38.6	-50	    0
24	SRC	19.8	LOS	37.4	50	    0
32	CW	57.6	LOS	37.2	0	    0
65	GTN	19.8	LOS	34.9	50	    0
66	Sun	19.8	LOS	34.8	50	    0
53	Ind	19.8	LOS	33.5	50	    0
43	PBS	57.6	LOS	29.5	0	    1
14	Fox	57.5	LOS	24.2	0	    1
39	CBS	86.2	LOS	21.7	-5	    1
33	NBC	85.4	1Edge	17.5    0	    5
38	ABC	87.5	1Edge	12.9	-5	    8
26	Ind	87.1	1Edge	11.5	-30	    9
49	MyN	86.3	1Edge	7.7	0	    10
7	Ind	88.0	2Edge	-7.2	-10	    8
23	ION	100.2	2Edge	-13.5	10	    16
Thanks in advance,

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1 - 4 of 24 Posts
The preamp will take of the losses after the antenna terminals (and help with weak TV tuner gain). For one thats about the best against overloading, get the Winegard HDP-269. Its also one of the lowest priced ones too.
And what would be the gain needed for channel 23 (NM -14db)?
If you had clear LOS to it, and -14 NM was just a matter of distance, roughly about 24dbi antenna gain for consistant viewing, as far as Ive gathered. Holl_ands would give you a better estimate.
Resultant signal output power from antenna: -90dBm + 14dB = -76dBm
Assuming there aren't significant losses in your system, then this should fall within the sensitivity range of your ATSC tuner (-83dBm).
So for his channel 23, that would mean an antenna with 21.7 + dbi.
How tipical is the sensitivity you mentioned (-83dBm)?
Will preamp help here or a preamp will also have similar sensitivity?
Well, if your tuners internal amp is poor, the preamp gain will help boost it. If your tuners gain is already great, the AGC circuit is going to limit additional gain benefits. (I havent seen an AGC adjustment control on a TV in a very long time. It used to be common.)
what do you make out of the explanation in the tvfool signal analysis faq, just below the table:
Big difference between being able to detect a station versus getting a consistant strong lock on it. Thats why I added 10 to the figure (instead of 0).

So basically from what I understand :

If you take the initial NM value for a given channel, add your antenna gain, subtract all the other system losses, and still end up with a value above 10, then you should be able to lock onto that channel.
1 - 4 of 24 Posts
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