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Using a AA-55 to Null coax.

Dr_DX

Well-Known Member
Jan 29, 2006
239
287
73
Just my .02:

1. - Why would you use "published" VFs? Use your analyzer to determine the true VF of your coax and then use that # when you are trying to make a jumper.

2. - There is no need to use a Tee and DL. The MFJ and RE instructions clearly state how to make a stub (jumper). Screw the coax pl-259 into the so-239 on the analyzer. For 1/4 wave stubs, leave the other end open. For 1/2 wave stubs, short the cut end. Tune for lowest X & SWR @ the desired Freq.

It is not that hard to short the coax for a 1/2 wave jumper, but the result is more accurate than using a tee and DL.

Where the "calibration" really comes in handy is when you take an antenna feedline, and re-calibrate your analyzer using it. Simply screw one end into the analyzer, and then go into the calibration mode. The calibration mode makes use of the open, shorted, and 50ohm loads which are screwed onto the other end of the feedline. Once calibrated, your feedline is now "transparent" to your analyzer.

Now you screw it into the antenna and you can tune your antenna with the analyzer through the feedline.

BTW, The newer 55s have Bluetooth so you can screw them into the bottom of the antenna and use you cell phone or tablet to see the tune.
 

Metalhead

Member
Jan 15, 2020
7
2
13
61
Just my .02:

1. - Why would you use "published" VFs? Use your analyzer to determine the true VF of your coax and then use that # when you are trying to make a jumper.

2. - There is no need to use a Tee and DL. The MFJ and RE instructions clearly state how to make a stub (jumper). Screw the coax pl-259 into the so-239 on the analyzer. For 1/4 wave stubs, leave the other end open. For 1/2 wave stubs, short the cut end. Tune for lowest X & SWR @ the desired Freq.

It is not that hard to short the coax for a 1/2 wave jumper, but the result is more accurate than using a tee and DL.

Where the "calibration" really comes in handy is when you take an antenna feedline, and re-calibrate your analyzer using it. Simply screw one end into the analyzer, and then go into the calibration mode. The calibration mode makes use of the open, shorted, and 50ohm loads which are screwed onto the other end of the feedline. Once calibrated, your feedline is now "transparent" to your analyzer.

Now you screw it into the antenna and you can tune your antenna with the analyzer through the feedline.

BTW, The newer 55s have Bluetooth so you can screw them into the bottom of the antenna and use you cell phone or tablet to see the tune.
I think I'l give this a try but how do you short out the coax for a 1/2 wave and then cut it to measure it? Also My 55 has the Bluetooth but I'm not sure how to use it. What app works with it?
 

NightThumper

South of Pittsburg
Nov 8, 2017
651
1,522
153
AntScope is the application for Bluetooth. It’s available for Windows, Apple or Android. Here are two links for what they call OSL (open, short,load). The DXENGINEERING link is an OSL kits using an SO239 and the Amazon link is using N connectors.

I have an RE AA-2000 Zoom. Didn’t need the frequency range but I wanted the improved display and the Multe function.

DXENGINEERING
Amazon
 
Last edited:

Dr_DX

Well-Known Member
Jan 29, 2006
239
287
73
I think I'l give this a try but how do you short out the coax for a 1/2 wave and then cut it to measure it? Also My 55 has the Bluetooth but I'm not sure how to use it. What app works with it?

NOTE: This is for a 1/2 wave jumper.

For a 1/4 wave jumper, do NOT short the shield & center conductor together.

NOTE: It is critical to determine the true VF of your coax (with your analyzer) and using that # for the VF setting when creating your jumper. Don't rely on "Published" VFs.

Just like the video above shows (or the donkeystomper youtube video), except after cutting a piece of coax off, you short the shield and the center conductor and while shorted, you read the 55. If its not where you want it, cut off a little more,

Cut, short, read; Repeat until you get X=0 (or as close as you can get to it). SWR should be 1.0 and R=50 (+/-2).

WARNING, once you get X is less than +/-1, make VERY short cuts and allow the analyzer reading time to "settle". You can't cut coax longer...

As in the video, I use teflon dielectric silvered PL-259s. Just hold the cut end against the silvered body to short the shield and center conductor together.

Software: https://rigexpert.com/products/software/

AntScope2 for your desktop - Windows, MAC or Ubuntu

AntScope for Android - for your Bluetooth enabled Android OS device
AntScope for IOS - for your Bluetooth enabled IOS OS device

Once the correct software is installed on your BT device, just pair the BT enabled 55 with it. and you can then control your 55 from your BT device.

Good Luck.
 

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