Does anyone know the input impedance of a television tuner module ?

[Externet]

Hello all.
As titled, what is the input impedance ?
Is there any impedance chart/plot of any ATSC modern television tuner antenna input that you may let me know/refer/link to ?
Or any ATSC tuner module schematic diagram, please ?

 

[jiripolivka]

Hello all.
As titled, what is the input impedance ?
Is there any impedance chart/plot of any ATSC modern television tuner antenna input that you may let me know/refer/link to ?
Or any ATSC tuner module schematic diagram, please ?

TV tuners have been always designed to match the input line impedance over the full bandwidth. I have not seen manufacturers' specifications but most VHF, UHF and new "digital" tuners offer low-noise operation over a full bandwidth, even with a long antenna cable is connected. Thus I would say the input impedance match is close to perfect.

If you have a wideband signal generator, you can try to measure input impedance deviation using a variable impedance circuit (tuner).

Tuner schematics may be available by Google as there were many designs of simple spectrum analyzers with tuners as receivers. I used many old tuners for VHF/UHF projects but the new types use LO synthesizers an other features and a diagram is difficult to find.

 

[chuckey]

They try to match them over the whole of their operating band(s) normally 75 ohms.
Frank

 

[Externet]

Thanks.
With my spectrum analyzer I have tracked many peaks and valleys from 26 Ω to 88 Ω along the receiving span, measuring every 10MHz; but larger/lower readings may be hiding in between samples.

Matching 75Ω over the full bandwidth does not make much sense. Impedance is tied to a frequency, or perhaps at several points, but not wideband.

Let me know if you find something. Tuner module data sheets I have seen are inconclusive.

 

[BigBoss]

Thanks.
With my spectrum analyzer I have tracked many peaks and valleys from 26 Ω to 88 Ω along the receiving span, measuring every 10MHz; but larger/lower readings may be hiding in between samples.

Matching 75Ω over the full bandwidth does not make much sense. Impedance is tied to a frequency, or perhaps at several points, but not wideband.

Let me know if you find something. Tuner module data sheets I have seen are inconclusive.

TV Tuner modules have always 75 Ohm input impedance during whole band ( 30MHz-900MHz).I don't know how you have done impedance measurements with a spectrum analyzer but this 75 Ohm impedance ( or -10 to -15dB Retrun Loss ) is compulsory in according to CENELEC and other related standards.