On Dec 31, 7:21*am, BDK wrote:
In article 43a532e0-63d5-4ae1-b27a-72085c8bbbf8
@t1g2000pra.googlegroups.com, says...
On Dec 30, 9:37*pm, D Peter Maus wrote:
Brian wrote:
I finally got a house out in the woods on five acres and I'm going to set up
a couple of pretty long wires and my Wellbrook ALA-1530. I've pretty much
decided on RG-6 for a couple of 150 ft. runs because the stuff's dirt cheap
and I can pick it up at the local Home Depot. Is the impedance mismatch here
going to be negligible, or should I just bite the bullet and go with RG-8 or
a similar 50 ohm coax?
-Brian
- *Alone, your receiver won't care. I doubt that the Wellbrook would,
- either.
-
- * *As a complex, however, you're going to have not one mismatch, but
- two. One at the output of the Wellbrook loop, and one at the input
of
- the antenna interface. This may result in standing waves on the
- transmission line which, in turn may result in irregularities in
- performance.
-
- * *With a reasonably well designed receiver, you'll likely not
notice
- any losses in practical listening. And unless you are working at the
- very limits of performance on signals very far down in the noise and
- doing A/B tests of one coax over another, you'll not detect the
- performance irregularities.
-
DPM,
Then it becomes a Practical Implementation and CBA type Problem.
CBA = Cost Benefit Analysis
http://en.wikipedia.org/wiki/Cost-benefit_analysis
http://en.wikipedia.org/wiki/Implementation
Cost of RG58/RG8 Coax Cable -versus- Cost of RG6 Quad-Shield
Coax Cable with a 75-to-50 Ohm Matching Transformer at each
end.
Starting with the Concept of a 9:1 Matching Transformer for General
Broad-Band Shortwave Radio (High Frequency 3~30 MHz) Use and
Application with 30 Turns (9-Side) and 10 Turns (1-Side) and the Same
Ferrite Core Material :
We now need a Matching Transformer to take the Antenna and Radios
SO-239 Jack/Plugs {BNC Connector Optional} -to- the 75 Ohm Coax
Cable with an F-Connector {BNC Connector Optional} .
The 50 Ohm 10 Turns (1-Side) should be understood.
Getting to the 75 Ohm (X-Side) should be simple Math :
75 / 50 = 1.5
Square Root of 1.5 = 1.225
Therefore the 75 Ohm (X-Side) would have 12 Turns.
A 75 Ohm to 50 Ohm [1.5:1] Matching Transformer would have
12 Turns (1.5-Side) and 10 Turns (1-Side) and the Same Ferrite
Core Material -as- 9:1 Matching Transformer for General Broad
Band Shortwave Radio (High Frequency 3~30 MHz) Use and
Application.
Anyone Else Have Any Ideas : On a Building Your Own {DIY}
a 75 Ohm to 50 Ohm [1.5:1] Matching Transformer ?
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
- - - - - - -
The Next Question Becomes : At What Cost ?
* Are the 75 Ohm to 50 Ohm [1.5:1] Matching Transformers
commercial available ? - a Ready Made Item ? Price ?
* Are the 75 Ohm to 50 Ohm [1.5:1] Matching Transformers a
Low Cost "Built-it-Yourself" Item ? - DIY Price ?
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
- - - - - - -
DPM - I go back to your first statement : "Alone, your receiver
won't care. I doubt that the Wellbrook would, either."
- - IMHO - For the vast majority of Shortwave Radio Listeners (SWLs)
- - Practical Implementation Says : Just Do It ! - Use the RG6 Coax
- - Cable -and- enjoy listening to your radios - iane ~ RHF
- - *.
- Why bother with all that? I've used RG6 coax for decades without
- any issues. A 1.5 to 1 SWR is nothing to worry about at all.
-
- This is just being anal.
-
- BDK
-
BDK - That I Am, and . . . Retentive Too ! ~ RHF
http://en.wikipedia.org/wiki/Anal_retentive
-butt- Then Again I Did Also Write :
IMHO - For the vast majority of Shortwave Radio Listeners (SWLs)
Practical Implementation Says : Just Do It ! - Use the RG6 Coax
Cable -and- enjoy listening to your radios - iane ~ RHF