[CQ-Contest] Coax Stubs...

[Dave Hachadorian]

You have the old version of the MFJ 259, so yes, use the 50 ohm 
resistor method.

Calculate the exact velocity factor (VF) of the ENTIRE LENGTH 
(you said about 100 feet) your specific cable, and then adjust 
the K2TR stub lengths by VF/0.66.

Dave Hachadorian, K6LL
Yuma, AZ


-----Original Message----- 
From: Douglas Ruz (CO8DM)
Sent: Thursday, January 14, 2016 9:12 AM
To: Dave Hachadorian
Cc: CQ-Contest
Subject: Re: [CQ-Contest] Coax Stubs...

Hi Dave,

Thanks for information about RG-6 cable...yes, it has foam 
insulation.

I have an old MFJ-259 ant analyzer...what do you suggest??...in 
the MFJ
manual said i must add a 50 ohms carbon resistor in serie with 
stub...is it
ok?

I think i can start with shortest stub 23 % longer than K2TR 
lenght...ok?

Any other idea is welcome.

TIA,

73....Douglas, CO8DM

"No creo que haya alguna emoción más intensa para un inventor que 
ver alguna
de sus creaciones funcionando. Esa emoción hace que uno se olvide 
de comer,
de dormir, de todo." - Nikola Tesla
----- Original Message ----- 
From: "Dave Hachadorian" <k6ll.dave at gmail.com>
To: "reflector cq-contest" <cq-contest at contesting.com>
Sent: Wednesday, January 13, 2016 5:49 PM
Subject: Re: [CQ-Contest] Coax Stubs...


I would use a regular TV-type male crimp connector for one end of
the stub, and then type F female to UHF male adapter:
http://www.showmecables.com/product/F-Type-Female-to-UHF-Male-Adapter.aspx?utm_source=google&utm_medium=cse&utm_campaign=925&zmam=49733141&zmac=5&zmas=1&zmap=925&gclid=CKaEu8ntp8oCFYaCfgodkwABjw

If you need a shorted stub, you can use a wire nut at the other
end:
https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwibgICJ7qfKAhXB4CYKHR4OAh0QjRwIBw&url=http%3A%2F%2Fwww.idealind.com%2FprodDetail.do%3FprodId%3Dwire-nut&psig=AFQjCNFEGVnkoG8vDszegO6oyMAI4hz0Cw&ust=1452811320423462

RG-6 has wide variation in velocity factor, so you need to use a
dip oscillator, or some other instrument to measure the resonant
frequency of the stub.  If your RG-6 has foam insulation, your
stubs will need to be roughly 23% longer than the K2TR lengths
shown here:
http://www.k1ttt.net/technote/k2trstub.html
You really need to measure the resonant frequency though, rather
than just cutting to length.


Dave Hachadorian, K6LL
Yuma, AZ