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Re: Topband: RG6 recommendations

To: "'Charles Stackhouse'" <cstack14478@yahoo.com>, <topband@contesting.com>
Subject: Re: Topband: RG6 recommendations
From: John Kaufmann via Topband <topband@contesting.com>
Reply-to: john.kaufmann@verizon.net
Date: Sun, 24 Jan 2021 21:07:55 -0500
List-post: <mailto:topband@contesting.com>
Hi Charlie, 

What you see in your TDR sweep of the RG6 is absolutely normal.  I've seen 
exactly the same thing.  The rise in apparent impedance with distance is caused 
by the loss in the cable.  If you had a lower loss cable, the TDR trace would 
be flatter.  As long as you don't seen any significant bumps or dips, your 
cable run is fine.

For use with Beverage antennas, the loss in the RG6 is inconsequential unless 
maybe you have an extremely long run of cable (thousands of feet).   

73, John W1FV

-----Original Message-----
From: Topband [mailto:topband-bounces+john.kaufmann=verizon.net@contesting.com] 
On Behalf Of Charles Stackhouse via Topband
Sent: Sunday, January 24, 2021 8:33 PM
To: topband@contesting.com
Subject: Topband: RG6 recommendations

After a period of inactivity, I set out to get my station going again. The 
Beverages were not working with very low signal levels and I replaced 600 foot 
RG6 feedline from shack to Beverage switch in the woods with new RG6 which 
still had the plastic wrap around the spool.
I was surprised when things were no better. The "new" coax is not right. The 
TDR sweeps show a straight line increase in impedance from 78 ohms to 95 ohms. 
There are no impedance "bumps" seen. The 400 feet left on the spool do the same 
thing as does 800 feet of the same stuff bought at the same time.
This stuff was bought on Ebay and is gel-flooded RG6 labelled "Commscope Inc. 
GA390709 and GA3907022." I bought it in Sept 2014 and it has been stored ever 
since in a dry heated basement.
Using an oscilloscope as a TDR I see that the impedance line is not level as 
with good coax but slopes  upward at an angle.  I also checked by placing a 330 
ohm resistor at the end of the cable and ran an SWR trace from 1-8 MHz with the 
SWR only 2-2.5. 
Why is this cable so lossy? Was it bad to begin with or did it deteriorate in 7 
years?
What recommendations for good RG6 can anyone make. There has been lots of 
critter chewing upon cables in the past so I guess gel-flooded cable would be 
preferable. Should I spend $230 for DXEngineerings good stuff or can I get by 
cheaper? 
p.s. I went out and checked each Beverage at the switchbox today and 4 out of 6 
were great. Only 3" of snow and temp was about 25 deg F. I was able to keep the 
snow and dielectric grease off of my laptop.
73, Charlie W2GN
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