FM Antenna Question

Factual Questions
1

Hi!

I have one of them newfangled HD radio receivers and I just put a (small) hole through my wall so I can feed a dipole antenna through from the outside. There’s no way I could put an antenna on the roof.

My reception is OK, but I would love to get more of the digital channels (the regular radio stations where I live are so-so, but there’s some great stuff on the second and third channel).

Here’s my question: would it help if I used some 200 ohm twin-lead to move the dipole antenna further up on my outside wall? Or, would there be impedance issues or something like that? Any other suggestions for improving reception?

Here’s my setup: dipole antenna attached to an outside wall (with a neighbor’s house maybe 15 or 20 feet away), fed through a hole in the wall to one of those old Radio Shack FM amplifiers (mostly used for converting the 200-ohm signal to a 75-ohm coax cable), then coax to the receiver (Yamaha receiver).

Thanks for your help!

2

Fist of all, it’s 300Ω.
Secondly, yes, the higher you can put the dipole, the better reception you will get.
You might also want to try an amplified antenna which is specifically designed for DTV.

3

Right! 300 ohms. Sorry, I must have destroyed that particular neuron over the weekend.

Is DTV in the same frequency range as HD radio? I know (or I think I know) that FM radio is between channels 4 and 5 on your television dial, but I don’t know whether DTV is in the same range as analog TV.

I tried one of those TERK antennas once (indoor, FM radio-type) – it was awful, much worse than a dipole.

OK, I’ll try moving it up. Thanks for your help.

4

The idea is to get your antenna up as high as possible and in the clear. Do NOT use a DTV antenna. Most of those signals now or shortly will reside in the UHF band. The HD radio signal “rides along” with the analog in the 88-108 mhz band. The other thing to keep in mind is that the digital radio signal is something like 10% strength of the analog carrier, so it will be more fragile. Good luck

5

OK, thanks for the advice, especially on skipping the DTV antenna. I’ll move the dipole up this weekend.

6

Actually, in the US and Canada the FM band is between TV channels 6 and 7, which is why you can pick up the sound for analog TV 6 just below the FM band.

7

Interesting. Then, I don’t understand how they could have channel 4 and 5 in NY, while every other channel is separated (2, 4, 5, 7, 9, 11, 13 are the broadcast channels here) – I knew that FM was in there someplace, and I just figured that it must be between 4 and 5 to provide the separation.

8

The tv spectrum is not continuous. In other words, TV channel 4 ends at 72mhz, and TV channel 5 starts at 76mhz, so they are not adjacent, therefore, they can exist in the same geographical area. We have 4 & 5 here in Central NC as well.

9

Interesting. I still don’t get why you never see both channel 6 and 7 or 2 and 3 in a broadcast area (or, at least, I haven’t seen it). Anyway, this is getting pretty far afield from my original question, so if I can’t track down the facts about that, I’ll come back and open another thread.

If you have any further advice about outdoor antennas and HD radio, I’d love to hear it.

Thanks, everyone, for your help!

10

Channels 2 and 3 are adjacent, as are 6 and 7. It’s just 4 and 5 that have about 2/3rds of a channel separating them. There are larger gaps between 7 and 8, and between 13 and 14. Cable TV shoves additional channels into those gaps.

ETA: to go back on-topic, you could also try rotating your dipole so see if that helps. A dipole won’t receive well along the line parallel to it (left or right in the crappy picture below).



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11

Hey, I think that’s a beautiful picture.

It will be against my outside wall, so I don’t think I can really rotate it. However, it should be roughly facing NYC, which is where most of they stations I want to get come from, so I should be OK.

12

Again, the gap is between channels 6 and 7, not 7 and 8. To recap, for the over-the-air channels, there is a 4 megahertz gap between channels 4 and 5, an 86 megahertz gap between channels 6 and 7 (leaving room for the FM band from 88 to 108 megahertz, and an 254 megahertz gap between channels 13 and 14. The rest of the channels are continuous.



BAND    CH #   FREQUENCY       BAND     CH #    FREQUENCY
VHF LOW  02    54-60 Mhz       VHF HIGH  07     174-180 Mhz
VHF LOW  03    60-66 Mhz       VHF HIGH  08     180-186 Mhz
VHF LOW  04    66-72 Mhz       VHF HIGH  09     186-192 Mhz
VHF LOW  05    76-82 Mhz       VHF HIGH  10     192-198 Mhz
VHF LOW  06    82-88 Mhz       VHF HIGH  11     198-204 Mhz
                               VHF HIGH  12     204-210 Mhz
                               VHF HIGH  13     210-216 Mhz