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Reducing output signal   Message List  
Reply | Forward Message #5579 of 6095 |
Re: [LPFM] Re:Reducing output signal

Hey Johnno,
 
Studying your figures, it seems that RG58A has a loss of 13mW per metre? So would I be right in saying to get a 1 watt TX down to approx. 300mW or less I would need around 60 metres of RG58A?
 
Cheers, Mike
 
 
On 15/02/2008 12:01:31 a.m., Johnno (valentine@...) wrote:
> Hello Grant,
>
> Will be a little loss in TX power... now to get my calculator out :)))
>
> If your TX is out putting 500mw @ 88.4 MHZ, SWR of 1:1 at 7 meters of
> coax
> will be
>
> RG58 = Output 409 mw
> RG58A = Output 401 mw
> RG58C = Output 384 mw
> RG213 = Output 450 mw
>
> If you have already increased TX to 1 watt for the 87.5 - 88.4 as RSM is
> talking about then the following applies..
>
> RG58 = Output 818 mw
> RG58A = Output 803 mw
> RG58C = Output 768 mw
> RG213 = Output 901 mw
>
> I hope that helps...
>
> Johnno
>
> ----- Original Message -----
> From: "88.4 FM The Cheese" <studio@... [link:
> mailto:studio@...]>
> To: <LPFM_Radio@... [link: mailto:LPFM_Radio@yahoogroups.
> com.au]>
> Sent: Thursday, February 14, 2008 10:46 PM
> Subject: [LPFM] Re:Reducing output signal
>
> > This is of interest to me, as I need to move my transmitter for a few
> > weeks while decorating the studio.
> > I have a 7 metre coax extension lead. Will this cause much loss to my
> > transmitter power?
> >
> > Cheers,
> > Grant
> >
> >
> >


Thu Feb 14, 2008 5:56 pm

valdusradio
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Message #5579 of 6095 |
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Heya guys, Anybody got any bright ideas on how to reduce the signal coming out of the back of the transmitter? We have a one watt transmitter but wish to...
Michael Rowse
valdusradio
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Feb 13, 2008
5:33 pm

Probably the cheapest/way to reduce power is to add attentuation to the aerial lead. Add length to the cable... not sure of exact figures but adding 10 metres...
Geoff Barkman
Mad_Milkie
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Feb 13, 2008
8:13 pm

Geoff's right. The easiest way to reduce power is to use more coax. The data is in the back of the Dick Smith catalog. If I remember correctly the spec for...
John Peterson
johnfp3
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Feb 13, 2008
8:40 pm

Speaking of 2.4GHz spectrum. I just hooked up some 600mW Wi-Fi PCI cards to have a look at the 2.4GHz spectrum in Invercargill. The amount of wireless LANs is...
Gavin Stephens
kiwi_rock_24
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Feb 14, 2008
12:05 am

This is of interest to me, as I need to move my transmitter for a few weeks while decorating the studio. I have a 7 metre coax extension lead. Will this cause...
88.4 FM The Cheese
grantthoms
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Feb 14, 2008
9:46 am

Hello Grant, Will be a little loss in TX power... now to get my calculator out :))) If your TX is out putting 500mw @ 88.4 MHZ, SWR of 1:1 at 7 meters of coax ...
Johnno
j_larsen2006
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Feb 14, 2008
11:01 am

That's great Johnno.. Thanks for the info :) Cheers, Grant ... of coax...
grantthoms
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Feb 15, 2008
9:22 am

Hey Johnno, Studying your figures, it seems that RG58A has a loss of 13mW per metre? So would I be right in saying to get a 1 watt TX down to approx. 300mW or...
Michael Rowse
valdusradio
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Feb 14, 2008
5:57 pm

The figures are based on the Freq Range, SWR ratio (ie: 1:1) and the cable that is being used... If we use 88.4 mhz, 1 Watt, SWR 1:1 and using RG58A = 39...
Johnno
j_larsen2006
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Feb 14, 2008
7:34 pm

I've been watching all the suggestions for reducing power and that is a simple and practical way of dealing with it. However if you have the schematic diagram...
averagesteward
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Feb 14, 2008
7:40 pm

Unfortunately it's not as simple as working it out to a mW per meter. That's why things are done in dB. For example, driving a coax cable with a known loss of...
Gavin Stephens
kiwi_rock_24
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Feb 15, 2008
1:13 am

You can make yourself a simple T attenuator with a loss of about 5.2dB Close to that value will suffice as its not exactly critical. Build it in a tin box with...
Keith
wantok.geo
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Feb 15, 2008
1:25 am

By the way, it's 500mW eirp, output from the antenna... Cheers Dean Groove 107.7FM PO Box 10 989 Wellington Ph 381 4766 (381GROOVE) Fax 381 4755 Mob 021-457...
Groove 107.7FM
groove_crew
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Feb 15, 2008
6:34 am

Thanks for those, Gavin. D. ... From: Gavin Stephens To: LPFM_Radio@... Sent: Friday, February 15, 2008 3:10 PM Subject: Re: [LPFM] Re:Reducing...
Groove 107.7FM
groove_crew
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Feb 15, 2008
6:57 am

That coax cable one is handy but I've just finally noticed the power budget one isn't right. It asks for dBm on a lot of things and provides answers in dB when...
Gavin Stephens
kiwi_rock_24
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Feb 15, 2008
11:42 am

... Reduce the drive to the final output - usually by reducing the voltage supplied to it. The final will last longer and run cooler....
wireless.radio
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Feb 16, 2008
6:43 am

Hey guys, I just realised that I never actually thanked everyone for their ideas on reducing the signal output. Shame on me. So....thanks everyone! We have...
Michael Rowse
valdusradio
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Mar 1, 2008
9:51 pm

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