[TowerTalk] Beverage Layout Problem

[David Gilbert]

Can you come up with a scientific explanation for why lossy coax picks 
up more noise than does a lower loss coax?  I can't.

And if you are able to do that, can you come up with a scientific 
explanation for why less than a db difference in loss would make several 
times that many db difference in the amount of noise it picks up?   I can't.

There's something very fishy here.

Dave   AB7E




On 5/13/2014 9:07 AM, Edward Sawyer wrote:
>   
>
> You're going to have to explain that some more for it to make any sense.
> The total cable loss for 200 feet of RG-213 at 7 MHz is about 1 db.  It
> seems to me that you'd have to have some really horrible impedance
> mismatches for the difference between RG-213 and LDF4 to even be noticeable.
>
>   
>
> The best clue that something is skewed, though, is your comment that the
> noise floor changes a bunch and the signal level not so much. That sounds
> like a termination problem of some sort, or more likely some kind of open
> shield in the RG-213.
>
>   
>
> 73,
>
> Dave   AB7E
>
>   
>
> RESPONSE - That's because its not about loss differences.  Its about the
> lossy coax also picking up sufficient noise to be amplified by a preamp and
> create noise floor.  If you don't believe it. Lay out 200 - 300 ft of RG8x
> or Rg6 on the ground and connect a 20dB preamp to it and see if you hear
> anything with a good receiver - mine's a FT1000MP Mk V (and supposedly that
> isn't even any good - although I never seem to have problems hearing more
> than most other people).  Then do the same thing with LMR600 or LDF4.  All I
> can say is - there's a difference.  And when you then connect a long
> beverage to it, you can hear more than with lossy coax.
>
>   
>
> Possibly if the pre-amp were mounted on the beverage feeds, you wouldn't
> hear as much noise pick up.  But with 5 beverages, that's a lot of preamps
> for me.
>
>   
>
> Ed  N1UR
>
>   
>
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