Does the RTL SDR also function as an antenna tuner?

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SlowBro
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Joined: Tue Mar 29, 2016 5:17 pm

Does the RTL SDR also function as an antenna tuner?

Post by SlowBro » Tue Mar 29, 2016 5:25 pm

I'm aiming to listen to ham and CB on 12m, 11m, 10m, 6m, and 2m. I'd love to build a tree-hung multiband antenna.

I've been reading about different types of multiband antennas, and most I've seen say an antenna tuner is required for best reception, to change capacitance and impedance. Sometimes it's called a transmatch, matchbox, antenna tuning unit, or an antenna coupler.

Does the RTL-SDR also include this capability in the software or do I need to consider purchasing an external antenna tuner as well?

I would guess the answer is "no it's not included" but wanted to confirm first. (If you asked me last week if the RTL includes a tuner I'd have said yes, thinking frequency tuner, not impedance matching.)

P-40 Warhawk
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Re: Does the RTL SDR also function as an antenna tuner?

Post by P-40 Warhawk » Tue Mar 29, 2016 8:46 pm

Antenna tuners are not needed for receivers , they are used for transmitters .

SlowBro
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Re: Does the RTL SDR also function as an antenna tuner?

Post by SlowBro » Tue Mar 29, 2016 10:55 pm

P-40 Warhawk wrote:Antenna tuners are not needed for receivers , they are used for transmitters .
Wouldn't they make an antenna receive better though, if there's an impedance mismatch? Sorry am new at this.

rtlsdrblog
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Re: Does the RTL SDR also function as an antenna tuner?

Post by rtlsdrblog » Wed Mar 30, 2016 4:08 am

There's no antenna tuner in the RTL-SDR and this type of thing can't be done in software. An antenna tuner will definitely help reception by reducing the SWR, but it is not 100% needed unless you really want the best reception possible. You can find ham band antenna tuners easily, though they can be quite expensive.

P-40 Warhawk
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Re: Does the RTL SDR also function as an antenna tuner?

Post by P-40 Warhawk » Wed Mar 30, 2016 11:57 am

I don't know that their is a antenna tuner that go's higher than 30MHZ , I could be wrong . Most everything the he wants is higher .
Now for everything below 30MHZ a MFJ 1020 works quite well and it's just under a $100.00 , less if used .

SlowBro
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Re: Does the RTL SDR also function as an antenna tuner?

Post by SlowBro » Wed Mar 30, 2016 1:12 pm

rtlsdrblog wrote:There's no antenna tuner in the RTL-SDR and this type of thing can't be done in software.
As expected. I knew the SDR could work miracles but...
rtlsdrblog wrote:An antenna tuner will definitely help reception by reducing the SWR, but it is not 100% needed unless you really want the best reception possible. You can find ham band antenna tuners easily, though they can be quite expensive.
Ok.

Just found that a Windom antenna can work multiple bands without a tuner so will look into that.

SlowBro
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Re: Does the RTL SDR also function as an antenna tuner?

Post by SlowBro » Wed Mar 30, 2016 1:13 pm

P-40 Warhawk wrote:I don't know that their is a antenna tuner that go's higher than 30MHZ , I could be wrong . Most everything the he wants is higher .
Now for everything below 30MHZ a MFJ 1020 works quite well and it's just under a $100.00 , less if used .
Thanks Warhawk!

P-40 Warhawk
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Joined: Thu Jun 26, 2014 11:55 pm

Re: Does the RTL SDR also function as an antenna tuner?

Post by P-40 Warhawk » Wed Mar 30, 2016 2:18 pm

SlowBro Just so you understand I am talking about frequencies that are in the 160 meters 80M 40M 20M 17M and 15M . This is were the MFJ 1020 works with
a direct sampling dongle . The 1020 isn't a antenna tuner , its more a preselector . This is a Quote from a friend by the name of Martin Ehrenfried (The MFJ has a tuned input stage, so it will attenuate all other unwanted out of band signals to a very large extent.

The active antenna is also likely to provide a much lower output level than a full sized antenna, unless it is mounted outside and is well clear of other conductive objects. My active antenna gives about 15 to 20dB lower signal level when it is used inside the house, but your millage may vary depending upon the materials used to construct the building.

These two factors could explain why you need a more gain in the dongle and also why you don't notice any overloading. )

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