[amsat-bb] Re: 75 ohm CATV Cable on 70 cm
Alvaro de Leon Romo
xe2at at hotmail.com
Tue May 22 08:24:28 PDT 2007
I read about it and I have dude what kind of 75 ohms cable are you using ...
In 70 cm I am using CATV hard line 1/2 inches for about 50 feets and in the
rotor section I am using RG6, when AO40 was ON I can run 100w and no problem
about the RG6 cable :-)
In other way I am using same cables for EME in 144 MhZ and I run 400w with
any problem that you are describing, I know that CATV hard line may be is
not a problem but RG6 have no problem also, here SWR both instalations are
I recomend 100 % both cables
>From: SV1BSX <sv1bsx at yahoo.gr>
>To: amsat-bb at amsat.org
>Subject: [amsat-bb] Re: 75 ohm CATV Cable on 70 cm
>Date: Tue, 22 May 2007 02:19:41 -0700 (PDT)
>...yes, I tryed that on my 2nd QTH because my
>experience with 100ft of RG213 was very bad on UHF.
>It was Sunday - no chance to buy something better..
>so I decided to replace the RG213 with 75 Ohm TV
> Well, the receiving-difference it was spectacular!
>With 75Ohm cable it was possible to hear Loud & clear
>the FO-29 downlink, with RG-213 not good enough!
> The same I noticed with other Satellites and weak
>signal ground stations.
> Later, after few weeks I replaced the 75 Ohm cable
>with AirCom+. Nothing changed between 75 Ohm TV and
>AirCom+ in the receiving! Absolutely equal receiving
>between the two cables, even if the AirCom+ was "10
>times" much more expensive cable!
> But in transmittion, it's obvious that the 75 Ohm
>cable has problem. It is not the mismatch (SWR 1.5)
>but this cable probably can not drive output Power
>bigger than 5-10 Watts. I confirmed that with 2-3 RIGs
>and several type of antennas. If you have output Power
>bigger than 10 Watts, is possible the RIG to
>decrease the Power output (ALC action? protection? I
>don't know!)a few seconds after PTT's press. (I'm
>talking always for UHF band).
> So, from my experience I believe that the 75 Ohm is
>excellent in case you need a separate cable from
>UHF-LNA output upto the Shack.
>I noticed that the Loss for 100ft at 450 MHz is about
>2-2.5 dB, very Low-value for a cheap cable.
> For transmittion is a cheap choice, if you have up to
>5-10 Watts maximum Power on UHF.
> Hope that helps
>73, Mak SV1BSX
>--- Mike Miller <mmiller at nctc.com> wrote:
> > Anyone have any experience using 75 ohm CATV cable
> > on 70 cm?
> > Mike KA5SMA
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