Timeline for Broadband antenna for SDR radio
Current License: CC BY-SA 3.0
10 events
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| Aug 10, 2017 at 20:32 | comment | added | SDsolar | I get your point, @Kevin. I did get a bit long-winded responding to the previous comments. None of it was responsive to the OP question, so would have been better off written in chat. | |
| Aug 10, 2017 at 14:51 | comment | added | Kevin Reid AG6YO♦ | @SDsolar Please don't write answers in comments. If it deserves three comments' worth of text, it deserves to be a post of its own — you could even post the question quoting Luca. | |
| Aug 10, 2017 at 9:50 | comment | added | SDsolar | @Luca, that is a very good question. And yes, lots of people like to build their own tuners. My little one has a much narrower range than the Dentron Super Tuner I let go years ago. Wikipedia has a fairly decent article on antenna tuners. Many difference in designs. Here is a link to the article, pointing to the losses section and the next paragraph that talks about where they can be located in the antenna system. You might find it interesting to skim the whole article and see if it answers your question: en.wikipedia.org/wiki/Antenna_tuner#Loss_in_Antenna_tuners | |
| Aug 10, 2017 at 9:42 | comment | added | SDsolar | One thing people do with mobile antennas is to use a 9-foot CB whip with a large loading coil at the bottom to provide inductance that can bring it to near resonance. However, coils don't radiate the same so you lose a lot of signal strength. If you took that same design upside down (the coil on top) you are more likely to make it work better. AM broadcast antennas have the same problem. They rarely resonant (as in, I have never seen one that didn't require a matching network). And the network is right next to the transmitter, soaking up power that never gets put out to the listeners. | |
| Aug 10, 2017 at 9:38 | comment | added | SDsolar | "antenna matching" is really just reactance cancellation. Radios want an antenna that presents as a purely resistive load because the capacitance and inductance are balanced out. That's good for the transceiver yet may not be best for capturing signals. The ideal antenna, however, is truly resonant on the frequency of interest, But often "good enough" is good enough. Tuners are great for utilizing a 75-meter phone antenna on the 80-meter CW band, no doubt. It gets a little dicier when trying to use a 40-meter antenna on the 15-meter band. | |
| Jul 27, 2017 at 17:30 | history | edited | Kevin Reid AG6YO♦ | CC BY-SA 3.0 |
added 38 characters in body
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| Jul 27, 2017 at 10:10 | comment | added | Luca | Are the antenna tuners essentially different tank circuits that you can choose from depending on the band you need? I have two old air variable capacitors laying around, making coils for LW will get extremely frustrating but would be doable. How does the antenna matching work? | |
| Jul 27, 2017 at 0:58 | comment | added | Phil Frost - W8II | "suppression increases with turns squared" this is only true until the arrangement's self-resonant frequency moves below the target suppression frequency. | |
| Jul 26, 2017 at 23:18 | comment | added | SDsolar | Ditto. I have a little MFJ-971 and you can always find some combination of settings that will help. Even if all you do at first is tune it for loudest "noise" | |
| Jul 26, 2017 at 17:15 | history | answered | Kevin Reid AG6YO♦ | CC BY-SA 3.0 |