I would put the noise bridge in the line between the transceiver and the 
amplifier.  This would prevent it from seeing your 600 watts.  I don't know 
about the on-off switch.



Lloyd Rasmussen, Kensington, MD
http://lras.home.sprynet.com
-----Original Message----- 
From: Tom Behler
Sent: Wednesday, January 01, 2014 11:40 AM
To: [log in to unmask]
Subject: Re: Using MFJ Noise Bridge To Determine Antenna Resonant Frequency

Bob:

Ok on not using both the manual and internal tuners together. ... This is
what I suspected.

Ok also on confirming Howard's procedure for determining the resonant
frequency of an antenna using the MFJ noise bridge.

Now, I have one more question:

Here in the home shack, am I correct in saying that I'm ok with keeping the
noise bridge in the circuit at all times, as long as I am absolutely 100%
sure to turn the noise bridge off before transmitting with 100 watts, and
especially before tuning and then using my AL811H amplifier?  The amp puts
out about 600 watts, and I know the Noise Bridge only handles 300 watts.  I
realize that the noise bridge has a protective circuit, but I have learned
over the years not to totally trust those protective circuits.

Tom Behler: KB8TYJ


-----Original Message-----
From: For blind ham radio operators [mailto:[log in to unmask]]
On Behalf Of Bob, K8LR
Sent: Wednesday, January 01, 2014 11:20 AM
To: [log in to unmask]
Subject: Re: Using MFJ Noise Bridge To Determine Antenna Resonant Frequency

Tom,

The noise bridge works very well in getting your SWR down to 1-1.  The
really nice thing about the MFJ212 and the VEC512 is that you can transmit
with the noise bridge in line with a power of up to 300 watts.

I would not use your 480 internal tuner if your running an external tuner.
That combination could cause some really high voltages at the antenna
connector that could pop some components.

Howard has got it right on how to find a resonant frequency with the noise
bridge.

Bob, K8LR, [log in to unmask]

----- Original Message -----
From: "Tom Behler" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, January 01, 2014 9:49 AM
Subject: Using MFJ Noise Bridge To Determine Antenna Resonant Frequency


Hi, again, everyone.



Sometime late last Summer, someone on the list suggested that an MFJ 212
Noise Bridge might be useful for determining the resonant frequency of an
antenna, even one that might be resonant outside the ham bands.



Is this possible, and, if so, how exactly might that be done?



Tom Behler: KB8TYJ