Antenna Question

classic Classic list List threaded Threaded
31 messages Options
12
Reply | Threaded
Open this post in threaded view
|

Antenna Question

Harlan Sherriff
OK all. I'm installing a 6m rotating beam and feeding it with LMR400. Would you connect the LMR to the antenna and allow it to move with the rotation, or run a short length of something much more flexible between the antenna and LMR? I have my concerns that the solid heavy inner conductor of the LMR won't take much movement.

Harlan
K4HES

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]
Reply | Threaded
Open this post in threaded view
|

Re: Antenna Question

stengrevics
I run LMR400 to my 6 & 2 meter antennas with no problems.  Just leave enough slack around the rotor and you’ll be fine.

John
WA1EAZ

> On Oct 10, 2016, at 6:14 PM, [hidden email] wrote:
>
> OK all. I'm installing a 6m rotating beam and feeding it with LMR400. Would you connect the LMR to the antenna and allow it to move with the rotation, or run a short length of something much more flexible between the antenna and LMR? I have my concerns that the solid heavy inner conductor of the LMR won't take much movement.
>
> Harlan
> K4HES
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]
Reply | Threaded
Open this post in threaded view
|

Re: Antenna Question

Elecraft mailing list
I don't know the suggested turning radius of LMR400.  In my system I use about 6 foot jumper of RG213 to do the section around the rotating section.  I use a KLM 8 el and the total length is longer.

Mel, K6KBE


      From: John Stengrevics <[hidden email]>
 To: [hidden email]
Cc: Elecraft Reflector <[hidden email]>
 Sent: Monday, October 10, 2016 3:17 PM
 Subject: Re: [Elecraft] Antenna Question
   
I run LMR400 to my 6 & 2 meter antennas with no problems.  Just leave enough slack around the rotor and you’ll be fine.

John
WA1EAZ

> On Oct 10, 2016, at 6:14 PM, [hidden email] wrote:
>
> OK all. I'm installing a 6m rotating beam and feeding it with LMR400. Would you connect the LMR to the antenna and allow it to move with the rotation, or run a short length of something much more flexible between the antenna and LMR? I have my concerns that the solid heavy inner conductor of the LMR won't take much movement.
>
> Harlan
> K4HES
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

   
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]
Reply | Threaded
Open this post in threaded view
|

Re: Antenna Question

Josh Fiden
In reply to this post by Harlan Sherriff
LMR400 is really stiff. When I used it as a rotor loop, I made a couple
of hoops around rather than directly flexing the cable around the tower.
Not sure if that makes sense. In any case, doing it again I would
definitely use a more flexible jumper for the rotor loop running to the
antenna. In the shack I'm making jumpers from RG-214 which is very
flexible and would work great as a rotor loop as well.

73,
Josh W6XU

On 10/10/2016 3:14 PM, [hidden email] wrote:
> OK all. I'm installing a 6m rotating beam and feeding it with LMR400. Would you connect the LMR to the antenna and allow it to move with the rotation, or run a short length of something much more flexible between the antenna and LMR? I have my concerns that the solid heavy inner conductor of the LMR won't take much movement.
>
> Harlan
> K4HES

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]
Reply | Threaded
Open this post in threaded view
|

Re: Antenna Question

Clay Autery
In reply to this post by Harlan Sherriff
You'll get lots of suggestions, but I believe the use of a single
unbroken feedline from the antenna to the shack (when possible) trumps
the inconvenience of properly engineering an install that does NOT put
unnecessary repetitive bending moments on the line.

Do the research....  There's all kinds of info on how to create/route a
feedline for rotator use...

Most of the people I know with tall towers and big antennae use LMR-400
(or similar size) AS the "smaller jumper".

No reason NOT to use LMR-400 from the antenna to the station...

______________________
Clay Autery, KY5G
MONTAC Enterprises
(318) 518-1389

On 10/10/2016 5:14 PM, [hidden email] wrote:

> OK all. I'm installing a 6m rotating beam and feeding it with LMR400. Would you connect the LMR to the antenna and allow it to move with the rotation, or run a short length of something much more flexible between the antenna and LMR? I have my concerns that the solid heavy inner conductor of the LMR won't take much movement.
>
> Harlan
> K4HES
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]
Reply | Threaded
Open this post in threaded view
|

Re: Antenna Question

Phil Kane-2
In reply to this post by Harlan Sherriff
On 10/10/2016 3:14 PM, [hidden email] wrote:

> Would you connect the LMR to the antenna and allow it to move with the rotation, or run a short length of something much more flexible between the antenna and LMR?

Commercial practice is to use a flexible jumper and "drip loop" between
the feedline and the antenna, even if the antenna is fixed solid to the
tower/mast.  This relieves the stress on the antenna connector.

73 de K2ASP - Phil Kane
Elecraft K2/100   s/n 5402

From a Clearing in the Silicon Forest
Beaverton (Washington County) Oregon
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]
Reply | Threaded
Open this post in threaded view
|

Re: Antenna Question

Josh Fiden
In reply to this post by Clay Autery
With an unbroken feedline, a failure or antenna swap can require
soldering connectors up the tower. Not fun. If you're concerned about
the additional loss of a barrel connector at 50MHz, you should be using
feedline with lower loss than LMR400 up the tower. Wrap the barrel
connection with good quality 3m vinyl tape and paint over with
Scotchkote to keep water out.

YMMV!

73,
Josh W6XU

On 10/10/2016 3:44 PM, Clay Autery wrote:
> I believe the use of a single
> unbroken feedline from the antenna to the shack (when possible) trumps
> the inconvenience of properly engineering an install that does NOT put
> unnecessary repetitive bending moments on the line.

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]
Reply | Threaded
Open this post in threaded view
|

Re: Antenna Question

k6dgw
In reply to this post by Phil Kane-2
As is military practice as well.  If you really want to get picky, the
400 should come up to the connector [sealed of course] and supported on
the tower, and then the jumper forms the drip loop to prevent water
running down the coax from running over ... and eventually into ... the
connector.

I don't think I'd run 400 all the way to a rotating antenna.

73,

Fred K6DGW
Sparks NV USA
Washoe County DM09dn


On 10/10/2016 4:34 PM, Phil Kane wrote:

> On 10/10/2016 3:14 PM, [hidden email] wrote:
>
>> Would you connect the LMR to the antenna and allow it to move with the rotation, or run a short length of something much more flexible between the antenna and LMR?
>
> Commercial practice is to use a flexible jumper and "drip loop" between
> the feedline and the antenna, even if the antenna is fixed solid to the
> tower/mast.  This relieves the stress on the antenna connector.
>
> 73 de K2ASP - Phil Kane
> Elecraft K2/100   s/n 5402

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]
Reply | Threaded
Open this post in threaded view
|

Re: Antenna Question

Clay Autery
In reply to this post by Josh Fiden
All things being equal... IF you are using LMR-400 as the main feedline,
there is NO REASON to use a different diameter at the rotator...

I was simply responding to what the OP said were the conditions... NOT
the "ideal"...

Bottom line... IF you engineer and install things properly, the fewer
breaks in the feedline, the better...

Fail to see why an antenna failure or swap would require soldering "up
the tower"... unless for some reason you change feedline to antenna
connector type....  not likely...  or you compromised a connector
termination or failed to weather protect properly....  In either case,
your odds of doing one of those things increase with every additional
connector you add to the line.

BTW, using the -DB suffix (if available) for any Times cable will
radically reduce the chances of moisture ingress on the feedline...

______________________
Clay Autery, KY5G
MONTAC Enterprises
(318) 518-1389

On 10/10/2016 6:49 PM, Josh Fiden wrote:

> With an unbroken feedline, a failure or antenna swap can require
> soldering connectors up the tower. Not fun. If you're concerned about
> the additional loss of a barrel connector at 50MHz, you should be
> using feedline with lower loss than LMR400 up the tower. Wrap the
> barrel connection with good quality 3m vinyl tape and paint over with
> Scotchkote to keep water out.
>
> YMMV!
>
> 73,
> Josh W6XU
>
> On 10/10/2016 3:44 PM, Clay Autery wrote:
>> I believe the use of a single
>> unbroken feedline from the antenna to the shack (when possible) trumps
>> the inconvenience of properly engineering an install that does NOT put
>> unnecessary repetitive bending moments on the line.
>
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]
Reply | Threaded
Open this post in threaded view
|

Re: Antenna Question

Bob-2
In reply to this post by Josh Fiden

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]
Reply | Threaded
Open this post in threaded view
|

Re: Antenna Question

John Parker
In reply to this post by Harlan Sherriff
There is a stranded center conductor version of the LM400, do not remember what the designation is. I plan to use some for the same reason, going around a rotor to a HexBeam.
73, John WB4UHCK3 #2165

    On Monday, October 10, 2016 6:16 PM, "[hidden email]" <[hidden email]> wrote:
 

 OK all. I'm installing a 6m rotating beam and feeding it with LMR400. Would you connect the LMR to the antenna and allow it to move with the rotation, or run a short length of something much more flexible between the antenna and LMR? I have my concerns that the solid heavy inner conductor of the LMR won't take much movement.

Harlan
K4HES

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]


   
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]
Reply | Threaded
Open this post in threaded view
|

Re: Antenna Question

Josh Fiden
In reply to this post by Clay Autery
On 10/10/2016 5:39 PM, Clay Autery wrote:
> All things being equal... IF you are using LMR-400 as the main feedline,
> there is NO REASON to use a different diameter at the rotator...
The point was using a lower loss cable for the long run up the tower,
such as hardline, then flexible cable for the rotor/drip loop and short
distance to the antenna feedpoint. At VHF, this is typical.
> Fail to see why an antenna failure or swap would require soldering "up
> the tower"...
Failure is not necessarily the antenna. It could be the solid center
conductor fracture after being flexed too many times :)

If you swap antennas and it's a single run of cable, you have to
manipulate the antenna on the tower to access the feedpoint. Then, for
example, if you put up a longer boom yagi, the feedpoint will most
likely be further away from the tower and your existing feedline won't
reach.

73,
Josh W6XU
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]
Reply | Threaded
Open this post in threaded view
|

Re: Antenna Question

Josh Fiden
In reply to this post by Bob-2
Completely agree. If access isn't a problem and the additional loss of
more flexible cable is tolerable, that's a great solution. I haven't
used Davis Bury-FLEX but heard very positive reports about it.

73,
Josh W6XU

On 10/10/2016 6:21 PM, Bob wrote:

>
> For sure a consideration.    There never is a perfect solution all is
> a compromise.   For me I wanted a single run because I see any extra  
> connectors as a potential failure points.  My Tower is crank
> up/tilt-over so not even as much of a repair or change issue.
>
> Nobody has mentioned it here but Times makes a LMR400 Ultraflex.  A
> possible solution.  Another cable I have been happy with is this:
>
> http://www.davisrf.com/buryflex.php
>

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]
Reply | Threaded
Open this post in threaded view
|

Re: Antenna Question

Bob-2
In reply to this post by Bob-2
OOPS...  Original left here in HTML not plain text.   Don't know why. Elecraft
in address book is listed as plain text only

Sorry,

Bob

K2TK



-------- Forwarded Message --------
Subject: Re: [Elecraft] Antenna Question
Date: Mon, 10 Oct 2016 21:21:14 -0400
From: Bob <[hidden email]>
To: Josh Fiden <[hidden email]>, Elecraft Reflector <[hidden email]>



For sure a consideration.    There never is a perfect solution all is a
compromise.   For me I wanted a single run because I see any extra  connectors
as a potential failure points.  My Tower is crank up/tilt-over so not even as
much of a repair or change issue.

Nobody has mentioned it here but Times makes a LMR400 Ultraflex.  A possible
solution.  The slightly increased loss on 50MC maybe about equal to the extra
connector loss.    Another cable I have been happy with is this:

http://www.davisrf.com/buryflex.php

A ham owned company that has been very responsive to requests.   Of my 7 feeds 6
use it and no issues and a few pieces are getting close to 8 years old.

73,

Bob

K2TK ex KN2TKR (1956) & K2TKR


<http://www.davisrf.com/buryflex.php>

On 10/10/2016 7:49 PM, Josh Fiden wrote:

> With an unbroken feedline, a failure or antenna swap can require soldering
> connectors up the tower. Not fun. If you're concerned about the additional
> loss of a barrel connector at 50MHz, you should be using feedline with lower
> loss than LMR400 up the tower. Wrap the barrel connection with good quality 3m
> vinyl tape and paint over with Scotchkote to keep water out.
>
> YMMV!
>
> 73,
> Josh W6XU
>
> On 10/10/2016 3:44 PM, Clay Autery wrote:
>> I believe the use of a single
>> unbroken feedline from the antenna to the shack (when possible) trumps
>> the inconvenience of properly engineering an install that does NOT put
>> unnecessary repetitive bending moments on the line.
>


______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]
Reply | Threaded
Open this post in threaded view
|

Re: Antenna Question

Clay Autery
In reply to this post by Josh Fiden
On 10/10/2016 8:37 PM, Josh Fiden wrote:

> On 10/10/2016 5:39 PM, Clay Autery wrote:
>> All things being equal... IF you are using LMR-400 as the main feedline,
>> there is NO REASON to use a different diameter at the rotator...
> The point was using a lower loss cable for the long run up the tower,
> such as hardline, then flexible cable for the rotor/drip loop and
> short distance to the antenna feedpoint. At VHF, this is typical.

Right...  I'd use the best/lowest loss feedline I could afford/source,
too...  and then use a smaller jumper...  I was simply responding to the
OP who said he was using LMR 400.... and saying that LMR-400 CAN and IS
frequently used as that "jumper" for the rotator loop...  or something
similarly sized in the .4-.5 inch range....
>> Fail to see why an antenna failure or swap would require soldering "up
>> the tower"...
> Failure is not necessarily the antenna. It could be the solid center
> conductor fracture after being flexed too many times :)

THAT would be the result of improper design/installation
>
> If you swap antennas and it's a single run of cable, you have to
> manipulate the antenna on the tower to access the feedpoint. Then, for
> example, if you put up a longer boom yagi, the feedpoint will most
> likely be further away from the tower and your existing feedline won't
> reach.

Point taken....  I'm not a big part swapper/upgrader...  I build things
the best I can so I don't have to upgrade, so I didn't think of that...
This situation would likely not occur for me, as I said above...  I
would likely NEVER use LMR-400 for a feedline run up a tower.  I'd use
the biggest/best feedline I could source/afford.

______________________
Clay Autery, KY5G
MONTAC Enterprises
(318) 518-1389

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]
Reply | Threaded
Open this post in threaded view
|

Re: Antenna Question

Mark E. Musick
In reply to this post by John Parker
I use LMR400-FLEX for my rotor loops and have had no problems. It has been
up since 1999 or 2000. LMR400-FLEX is the designator for the stranded center
conductor version. I also have used Davis FLEX LMR400 equivalent and if I
remember correctly Davis-FLEX that is what is stamped on the feedline. The
difference between LMR400 solid center conductor and LMR400 FLEX stranded
center conductor has a loss of about .1 or .2db more at 50 MHz. Again if my
memory is correct.

Mark, WB9CIF

-----Original Message-----
From: Elecraft [mailto:[hidden email]] On Behalf Of John
Parker
Sent: Tuesday, October 11, 2016 1:38 AM
To: [hidden email]; Elecraft Reflector <[hidden email]>
Subject: Re: [Elecraft] Antenna Question

There is a stranded center conductor version of the LM400, do not remember
what the designation is. I plan to use some for the same reason, going
around a rotor to a HexBeam.
73, John WB4UHCK3 #2165

    On Monday, October 10, 2016 6:16 PM, "[hidden email]"
<[hidden email]> wrote:
 

 OK all. I'm installing a 6m rotating beam and feeding it with LMR400. Would
you connect the LMR to the antenna and allow it to move with the rotation,
or run a short length of something much more flexible between the antenna
and LMR? I have my concerns that the solid heavy inner conductor of the LMR
won't take much movement.

Harlan
K4HES

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html Message
delivered to [hidden email]


   
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html Message
delivered to [hidden email]

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]
Reply | Threaded
Open this post in threaded view
|

Re: Antenna Question

Edward R Cole
In reply to this post by Harlan Sherriff
I do the same as Josh:
http://www.kl7uw.com/6m&Dish_Dec-2013_1.jpg

Multiple turns of LMR-400.  That connects to 7/8-Heliax coming up the
tower leg.

73, Ed - KL7UW

From: Josh Fiden <[hidden email]>
To: [hidden email]
Subject: Re: [Elecraft] Antenna Question
Message-ID: <[hidden email]>
Content-Type: text/plain; charset=windows-1252; format=flowed

LMR400 is really stiff. When I used it as a rotor loop, I made a couple
of hoops around rather than directly flexing the cable around the tower.
Not sure if that makes sense. In any case, doing it again I would
definitely use a more flexible jumper for the rotor loop running to the
antenna. In the shack I'm making jumpers from RG-214 which is very
flexible and would work great as a rotor loop as well.

73,
Josh W6XU



73, Ed - KL7UW
http://www.kl7uw.com
     "Kits made by KL7UW"
Dubus Mag business:
     [hidden email]

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]
Reply | Threaded
Open this post in threaded view
|

Re: Antenna Question

Victor Rosenthal 4X6GP
In reply to this post by Harlan Sherriff
One way to do it with a single piece of stiff coax is to place a standoff about a foot long above and below the rotor. Then form the coax into a spiral of several turns between the standoffs. Rotation will just tighten or loosen the spiral and not stress the coax at all. The standoffs also take the weight of the coax.

Vic 4X6GP

> On 11 Oct 2016, at 01:14, [hidden email] wrote:
>
> OK all. I'm installing a 6m rotating beam and feeding it with LMR400. Would you connect the LMR to the antenna and allow it to move with the rotation, or run a short length of something much more flexible between the antenna and LMR? I have my concerns that the solid heavy inner conductor of the LMR won't take much movement.
>
> Harlan
> K4HES
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]
Reply | Threaded
Open this post in threaded view
|

Re: Antenna Question

Jim Brown-10
In reply to this post by Josh Fiden
On Mon,10/10/2016 4:49 PM, Josh Fiden wrote:
> If you're concerned about the additional loss of a barrel connector at
> 50MHz, you should be using feedline with lower loss than LMR400 up the
> tower.

The loss in GOOD quality UHF connectors and barrels at 50 MHz is
negligible. There are urban legends (false, as usual) claiming that
every connector loses a dB. The grain of truth is that JUNK connectors
may introduce significant loss, but GOOD connectors and barrels do NOT.
"Good" means Amphenol 83-1SP for the PL-259s, and Amphenol or surplus
MIL-spec for the barrels.

Several years ago, I made up more than a dozen 100 ft cables using a
cable of somewhat better construction than LMR400 (Commscope 3227) for a
DX trip. The connectors were Amphenol 83-1SP that I soldered myself. To
test those cables, I spliced them together using Amphenol barrels and
measured the loss of about 1300 ft of cable up to 500 MHz using HP
generator and spectrum analyzer. The measured loss was LESS than the
manufacturer's spec. There were 27 83-1SPs and 13 barrels in line.

JUNK connectors are the shiny,unbranded stuff you see at ham flea
markets, and sold online and in ham magazines.

73, Jim K9YC

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]
Reply | Threaded
Open this post in threaded view
|

Re: Antenna Question

Nr4c
Why use barrels?  Doesn't Amphenol or Pastornack make a female UHF connector to put on cable end.  For this specific use, a custom  built cable seems appropriate.

Sent from my iPhone
...nr4c. bill


> On Oct 11, 2016, at 4:38 AM, Jim Brown <[hidden email]> wrote:
>
>> On Mon,10/10/2016 4:49 PM, Josh Fiden wrote:
>> If you're concerned about the additional loss of a barrel connector at 50MHz, you should be using feedline with lower loss than LMR400 up the tower.
>
> The loss in GOOD quality UHF connectors and barrels at 50 MHz is negligible. There are urban legends (false, as usual) claiming that every connector loses a dB. The grain of truth is that JUNK connectors may introduce significant loss, but GOOD connectors and barrels do NOT. "Good" means Amphenol 83-1SP for the PL-259s, and Amphenol or surplus MIL-spec for the barrels.
>
> Several years ago, I made up more than a dozen 100 ft cables using a cable of somewhat better construction than LMR400 (Commscope 3227) for a DX trip. The connectors were Amphenol 83-1SP that I soldered myself. To test those cables, I spliced them together using Amphenol barrels and measured the loss of about 1300 ft of cable up to 500 MHz using HP generator and spectrum analyzer. The measured loss was LESS than the manufacturer's spec. There were 27 83-1SPs and 13 barrels in line.
>
> JUNK connectors are the shiny,unbranded stuff you see at ham flea markets, and sold online and in ham magazines.
>
> 73, Jim K9YC
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]
12