[amsat-bb] Re: [Mw] Pre Fab Coax sections

TexasRF@aol.com TexasRF at aol.com
Thu May 21 18:17:28 PDT 2009

This is certainly a novel approach to making UG21 connectors work with  
LMR400 cable. But, considering you can buy brand new N connectors with silver  
plated center pin for only $5.95 (at Texas Towers) it seems like a lot of 
work  to maybe reuse an old connector. New UG21 connectors cost as much as one 
that  fits properly so there is no cost savings going that route.
Regular L:MR400 uses a copper plated aluminum center conductor. Messing  
with the center conductor on that cable is going to damage the copper plating; 
 making it impossible to solder.
Gerald Williamson K5GW
General Manager/Texas Towers
In a message dated 5/21/2009 8:00:02 P.M. Central Daylight Time,  
n5gdb at austin.rr.com writes:

Glenn  Little and others,

There is a neat way to use type N connectors on  LMR400 and LMR400UF. I 
an article for QST/QEX on the method and  passed it to Ray Mack, W5IFS, who 
is an editor for QEX. He has not passed  the article on as yet, though. 
Basically, the diameter of the inner  conductor is too large for the 
N connector, therefore that  diameter must be reduced to fit. The way to do 
that reduction effectively  when you are making up a number of cables is to 
make a set of "Center  Conductor Reduction Dies." Start with inch-long 
sections of 3/8-inch cold  rolled steel and drill all the way through each 
piece with a series of  numbered drills starting with the largest drill 
is the diameter of  the center conductor and ending with the drill that 
enters the center  pin of the N connector. This work is best done on a 
working lathe to  get a concentric hole. Center drill the entry end to 
provide a starting  chamfer. Using a thin cutoff wheel in your Dremel 
Moto-Tool, make two  cross cuts on the centerline to about 1/8-inch below 
chamfer on that  end and once on the other end without a chamfer. Now, 
the dies in  descending sequence, chuck the die in an electric drill. Strip 
the end of  the cable and expose a little more of the center conductor than 
is needed.  Insert the cable into the reduction die and spin the drill 
until the  end reaches the insulation (there will be a short section of 
unreduced  center conductor). Reverse the die in the drill and finish the 
to the  insulation. Move to the next die. Occasionally, trim the copper 
that  develops. Stop when the center conductor enters the center pin of the 
connector. For LMR400UF, you must make the center conductor a solid  
conductor by tinning the exposed center conductor. Again, inspect the face  
of the insulation and remove any copper flash to prevent a possible short.  
Now, you can assemble the cable to the N connector just as you would  
assemble it using RG8 cable. The cutting edges of the reduction die are  
those slots that you cut using the Dremel (you could do it with a hack saw  
as I did at first, but the Dremel is much faster). I have assembled about  
N-M and N-F connectors to LMR400 cables using this method which really  
trying to reduce the center conductor with a file when you have many  
connectors to install.


Lloyd Crawford, N5GDB,  EM10bf
n5gdb at austin.rr.com
Roadrunners Microwave Group
----- Original  Message ----- 
From: "D. McGarrett" <dmcgarrett at optonline.net>
To:  "Glenn Little WB4UIV" <glennmaillist at bellsouth.net>
Cc: "Microwave  list" <microwave at echo.valinet.com>; "'Amsat - BBs'"  
<amsat-bb at amsat.org>; "Jim Sanford"  <wb4gcs at amsat.org>
Sent: Thursday, May 21, 2009 6:41 PM
Subject:  Re: [Mw] [amsat-bb] Pre Fab Coax sections

> Glenn Little WB4UIV  wrote:
>> If you like throwing money at the problem, try  Pasternack.
>> 5 feet at $83.00 at S. M.  Electronics.
>> 5 feet at $78.25 at  Pasternack.
>> I always build my own. That way I can only  blame myself for bad cables.
>> 73
>>  Glenn
> I don't  have a solution for you, but when I was a working engineer, I
> found  that Pasternack was one of
> the most expensive solutions (to anything!)  there was.  I never heard of
> S.M. Electronics.  Google  will
> give you a list of  connector manufacturers and sales  people.  I'm with
> Glenn--build your own!       LMR-xx cable is a product of Times
> Microwave.  Excellent  cable!
> (If you can use LMR-400, it will be a lot cheaper, but you  _can't_  use
> regular type N connectors on it.)
> On the  other hand, type N connectors are a lot easier to use than the GD
> UHF  connectors, and
> work a heck of a lot better--but you probably know  that already.
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