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10db 50 OHM Attenuator For FM Transmitter!?!


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Quick question guys, I want to order a 10db 50 ohm attenuator to make sure I get just enough signal for my display, and so I don't get in trouble with the guys in the black van...

I have a 500mW Transmitter and want to bring the power down to 100mW, according to someone, saying somewhere 100mW is legal.. not sure how true that is...

​Anyways for me 500mW is too powerful? Where can I get an Attenuator for the right price to do the job for me?

Edited by Arteom
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I have used the ones on this page for the past few years...

http://www.mpja.com/Scope-Probes--Test-Leads/products/57/

Quick question guys, I want to order a 10db 50 ohm attenuator to make sure I get just enough signal for my display, and so I don't get in trouble with the guys in the black van...

I have a 500mW Transmitter and want to bring the power down to 100mW, according to someone, saying somewhere 100mW is legal.. not sure how true that is...

​Anyways for me 500mW is too powerful? Where can I get an Attenuator for the right price to do the job for me?

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I have used the ones on this page for the past few years...

http://www.mpja.com/...ds/products/57/

Me too. No issues at all with it. Direct link to the one I use: http://www.mpja.com/10db-Feed-Through-Attennuator-Terminator/productinfo/16547+TE/

@ Arteom: I believe that 1 watt is it's maximum power rating, not what it outputs, if it was doing that I think by now I'd have already had a little visit with the guys in black suits, dark glasses and black vans.

It cut my MBB Eclipe 4000 power output down from transmitting 2-5 miles to around 500' or a bit over, yes still a bit over the 200' limit.

Been using this particular unit for 3 years now, works for my needs and thus far no FCC visitations.

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I Want to cut my range to 200'... i'm good, the current chinese unit transits around 500' now anyways, and its a 500mW ;)

I'm just scared of this whole FCC thing... Why risk it!?!

Are you sure the direct link is to the one that will work for me to cut the power DOWN?

Did anyone try to call that company to see if they can get cheaper shipping? I mean $10 for that little thing is ridiculous! Flate rate shipping is $5

Edited by Arteom
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The 10bd says it's power is 1W if thats output power thats more than needed, it should be .1W or 1/10 of a watt?

It's an attenuator...

http://en.wikipedia....r_(electronics)

And here's how attenuation works in regards to power output...

http://sss-mag.com/db.html

Edited by Jeffrey
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The 10bd says it's power is 1W if thats output power thats more than needed, it should be .1W or 1/10 of a watt?

That is its maximum input power rating. Its a passive device, does not generate power.

A 10 dB attenuator on a 500 mW output will give you 50 mW output (10 log of the power ratio).

As has been discussed here ad nauseum, part 15 does not dictate a power output limitation, but a field strength limit. While you can estimate and say "x mw will keep me within limits", it is truly an estimate.

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Wow, thanks guys... those links helped me out a-lot Jeffrey, I'll go ahead and see if I can get cheaper shipping on the 10 DB model..

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I recently contacted an eBayer...

The attenuation will be relative to the input. For instance, 3 db is commonly referred to as "half-power". 3 db cuts any input in half. 6 db will reduce the input to 1/4 of its original power (3 cuts it in half, then 3 cuts that half in half, leaving a quarter of the original).

In your case, 6 db will bring you to 125mW. Is that close enough?

10 db attenuates by a power of 10. So 50W would be attentuated to 5W. 500mW would be attenuated to 50mW.

Attenuation is basically "negative gain". This calculator will provide good numbers expressed as "negative gain", i.e. -10db of gain. This is actually attentuation.

http://www.rf-amplifiers.com/index.php?topic=gain

Enter your starting power as the input power (500mW) and your desired power as the output power (100mW) and the calculation will be -7db. You can play around to find acceptable power levels.

I have one 6db attenuator left, which will bring your output power down to approximately 125mW.

http://www.ebay.com/itm/130766270081?ssPageName=STRK:MESELX:IT&_trksid=p3984.m1555.l2649

Thanks and I hope that I have been of some help.

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Guest Don Gillespie

I recently contacted an eBayer...

The attenuation will be relative to the input. For instance, 3 db is commonly referred to as "half-power". 3 db cuts any input in half. 6 db will reduce the input to 1/4 of its original power (3 cuts it in half, then 3 cuts that half in half, leaving a quarter of the original).

In your case, 6 db will bring you to 125mW. Is that close enough?

10 db attenuates by a power of 10. So 50W would be attentuated to 5W. 500mW would be attenuated to 50mW.

Attenuation is basically "negative gain". This calculator will provide good numbers expressed as "negative gain", i.e. -10db of gain. This is actually attentuation.

http://www.rf-amplif....php?topic=gain

Enter your starting power as the input power (500mW) and your desired power as the output power (100mW) and the calculation will be -7db. You can play around to find acceptable power levels.

I have one 6db attenuator left, which will bring your output power down to approximately 125mW.

http://www.ebay.com/...984.m1555.l2649

Thanks and I hope that I have been of some help.

didn't Gary just mention this a few posts up??

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didn't Gary just mention this a few posts up??

Yes, I just decided to share it ;)

I have a quick question though, will the 10db unit bee too much of a power decrease? Thats only 50mW when currently my radio only travels around 500'?

What's the return policy like on MPJA? Has anyone dealt with that before?

Edited by Arteom
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I will put it simple if at 500mw you only got 500 ft the crickets are all anyone will here during your display unless standing beside the house because 50mw is not even going to transmit out of the house.

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Will you get the bloody 6db attenuator and be done with it. This will lower your power to 125mW at the antenna. I cant see you having any problems, unless you put some dang dipole on it. And put it 50' above your roof. Them little antennas that come with the transmitter do a wonderful job for our purpose.

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