From: w...@w8ji.com
The worse case SWR of a 50 ohm system with 75 ohm cable isn't 1.5:1 when
normalized to 50 ohms. It is 2.25:1. 1.5*1.5 = 2.25
A 50 ohm load with 1/4 wave of 75 ohm is 112.5 ohms, and that is 2.25:1.
This is why the cable needs to be 1/2 wave long, so impedance is back
I think you're being overly picky. The 75-ohm cable would be at worst a 1.5:1
mismatch. Probably a fraction of a dB loss at most, particularly with foam type
hard line. If you have a source of good, low-loss 75-ohm coax that will safely
handle the power you intend to run, and which will hold up
On 6/13/2014 12:17 PM, Donald Chester wrote:
I think you're being overly picky. The 75-ohm cable would be at worst a 1.5:1
mismatch. Probably a fraction of a dB loss at most, particularly with foam type
hard line. If you have a source of good, low-loss 75-ohm coax that will safely
handle the
-
From: Donald Chester k4...@hotmail.com
To: topband@contesting.com
Sent: Fri, 13 Jun 2014 19:17:59 - (UTC)
Subject: Re: Topband: 50 ohm direct burial coax cable
I think you're being overly picky. The 75-ohm cable would be at worst a 1.5:1
mismatch. Probably a fraction of a dB loss at most
)
Subject: Re: Topband: 50 ohm direct burial coax cable
You can easily make the 75 ohm coax essentially invisible in a monoband
application by using some RG-11 to extend the total length of the 75
ohm feedline to any multiple of 1/2 wavelength.
73
Frank
W3LPL
- Original Message -
From
N2MS
- Original Message -
From: Donald Chester k4...@hotmail.com
To: topband@contesting.com
Sent: Fri, 13 Jun 2014 19:17:59 - (UTC)
Subject: Re: Topband: 50 ohm direct burial coax cable
I think you're being overly picky. The 75-ohm cable would be at worst a
1.5:1 mismatch. Probably
, June 13, 2014 4:01 PM
Subject: Re: Topband: 50 ohm direct burial coax cable
You can easily make the 75 ohm coax essentially invisible in a monoband
application by using some RG-11 to extend the total length of the 75
ohm feedline to any multiple of 1/2 wavelength.
73
Frank
W3LPL
- Original
: Fri, 13 Jun 2014 20:36:49 - (UTC)
Subject: Re: Topband: 50 ohm direct burial coax cable
Ive been using that CATV RG-11 since the late 70's as jumpers to the
hardline from wire antennas, in the house, and as phasing lines for 160 and
80M verticals. Never a hint of heat at 1200W but someone
This does however, slightly narrow the bandwidth of the antenna if the coax
loss is small because as you move away from the perfect 1/2 wave point the
coax will start to show SWR. For monobanders this usually isn't a problem,
but it may be for some tribanders.
This will also work on all the
You bring up some good points. I got a couple of hundred feet of Flooded
Commscope 75 ohm RG-11 type at a good proce. I don't have the part
number handy. I've been very happy with it at 100 watts. I'm thinking of
running 500 watts. The center conductor is copper clad steel. I'm
concerned about
On 6/13/2014 9:51 PM, Tom W8JI wrote:
The worse case SWR of a 50 ohm system with 75 ohm cable isn't 1.5:1
when normalized to 50 ohms. It is 2.25:1. 1.5*1.5 = 2.25
Wrong. If you're using 75 ohm line, it's a 75 ohm system -- the system
impedance is the line impedance. It's the the match of the
burial coax cable
Mike,
I like LMR400-DB. Not only is it direct burial but it is the lowest loss of
the RG8 type cables.
73,
Tom WA2BCK
-Original Message-
From: mstang...@comcast.net
Sent: Tuesday, June 03, 2014 10:10 AM
To: topband@contesting.com
Subject: Topband: 50 ohm direct
On 6/5/2014 5:43 AM, bruce whitney via Topband wrote:
Again,
You might want to compare this cable to the LMR400-DB.
It has performed well for me.
http://www.davisrf.com/buryflex.php
Bruce W8RA
Bury Flex is good cable, however, in comparison
to LMR400, its velocity factor is 10 to 15% lower.
whitney; Tom WA2BCK; mstang...@comcast.net; topband@contesting.com
Subject: Re: Topband: 50 ohm direct burial coax cable
On 6/5/2014 5:43 AM, bruce whitney via Topband wrote:
Again,
You might want to compare this cable to the LMR400-DB.
It has performed well for me.
http://www.davisrf.com
Mike,
I like LMR400-DB. Not only is it direct burial but it is the lowest loss of
the RG8 type cables.
73,
Tom WA2BCK
-Original Message-
From: mstang...@comcast.net
Sent: Tuesday, June 03, 2014 10:10 AM
To: topband@contesting.com
Subject: Topband: 50 ohm direct burial coax cable
Does anyone know of a source for 50 ohm RG-8 type direct burial coax able.
I can find many sources for CATV and Satellite 75 ohn cable but not 50 ohm.
Direct burial cable is coated with and anti-fungal compound. I''ve had success
with 75 ohm cables for receiving and want to purchase 50 ohm
Buryflex is a good one.
73,
Jorge
CX6VM/CW5W
Enviado desde mi iPhone
El 03/06/2014, a las 11:10, mstang...@comcast.net escribió:
Does anyone know of a source for 50 ohm RG-8 type direct burial coax able.
I can find many sources for CATV and Satellite 75 ohn cable but not 50 ohm.
http://www.davisrf.com/buryflex.php
73, Jim N7US
-Original Message-
Does anyone know of a source for 50 ohm RG-8 type direct burial coax
cable?
I can find many sources for CATV and Satellite 75 ohn cable but not 50 ohm.
Direct burial cable is coated with and anti-fungal compound.
lucky we'll see someone start making coax that way!
-Bill
-Original Message-
From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of
mstang...@comcast.net
Sent: Tuesday, June 03, 2014 10:10 AM
To: topband@contesting.com
Subject: Topband: 50 ohm direct burial coax cable
Bill,
Thanks. I will check it out.
Mike N2MS
- Original Message -
From: Bill Wichers bi...@waveform.net
To: mstang...@comcast.net, topband@contesting.com
Sent: Tue, 03 Jun 2014 14:58:51 - (UTC)
Subject: RE: 50 ohm direct burial coax cable
Usually direct burial cable is just a PE
Bill,
Thanks. I will check it out.
Mike N2MS
- Original Message -
From: Bill Wichers bi...@waveform.net
To: mstang...@comcast.net, topband@contesting.com
Sent: Tue, 03 Jun 2014 14:58:51 - (UTC)
Subject: RE: 50 ohm direct burial coax cable
Usually direct burial cable is just a PE
: Tuesday, June 3, 2014 11:18 AM
Subject: Re: Topband: 50 ohm direct burial coax cable
Bill,
Thanks. I will check it out.
Mike N2MS
- Original Message -
From: Bill Wichers bi...@waveform.net
To: mstang...@comcast.net, topband@contesting.com
Sent: Tue, 03 Jun 2014 14:58:51 - (UTC)
Subject
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