[mythtv-users] No reception or EIT for Channel 5 in Essex [OT]

Allen Edwards allen.p.edwards at gmail.com
Thu Sep 18 17:40:20 UTC 2008


On Thu, Sep 18, 2008 at 9:38 AM, peter nikolic
<p.nikolic1 at btinternet.com> wrote:
> On Tuesday 16 September 2008, Allen Edwards wrote:
>> > I think you need to back to collage   a little .
>> >
>> > I did state UK and COAX i care not for the US system of 300 Ohm ribon
>>
>> Free space is 377 ohms so they build antennas at 300 ohms to match
>> into free space.  Then they use a 4:1 transformer (a balum) to match
>> to the 75 ohm coax.  I see from looking at amazon.co.uk that all your
>> antennas have balums built in for some reason.  Sorry, I did not
>> realize that.
>>
>> I also didn't realize that hybrid combiners like these:
>> https://www.tselectronic.com/chanplus/2532_34.html
>> had not made it over there yet.  You really should get some so you
>> don't have to mismatch the coax the way you explained in your writeup.
>>  Too bad you use such junk over there when these combiners are so
>> inexpensive.
>>
>> By the way, I have a Masters in EE from Stanford, an Extra Class Ham
>> license, and 30 years experience in RF.  That is enough education for
>> now.
>>
>> Allen
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>
> Obviously not quite enough in thius instance   next time engadge brain before
> mouth we are a 75 ohm coax system here in the UK we do NOT use 300 ohm ribbon
>
> EOS
>
>
Brain firmly engaged.  Like I said before, I was trying to clarify
your obvious misstatement that the splitter presented a 37.5 ohm load
to the cable.  This is not true.

On the other hand, I said that the antenna was 300 ohms, which it is.
It is the output of the balun on your antennas that is 75 ohms, not
the antenna.  So, technically, you misspoke there although that is a
nit and I would not call you wrong for saying it that way.  I also
said people used 300 ohm twin lead in the past but generally not now.
Are saying that never in the history of the UK did people use twin
lead?  Perhaps, but my statement would still be true because people
did used to use twin lead in other countries.  My comments were not
country specific.

My suggestion is that you two not be so rude to someone trying to
clarify a misstatement and bring a little knowledge to this forum.
Fine to clarify that your antennas have built in baluns, but not to
make personal attacks.

Allen


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