Tom,

You are correct in that the noise bridge is protected up to 300 watts.  This 
does not mean you can leave it turned on.  You must turn it off.  The 
protection circuit is just for, in case you forget.  You would place the 
noise bridge between your 590 and the amp.

The string of components should be as follows: 590, noise bridge, amp, SWR 
bridge and finally the tuner.

You would tune the tuner using the noise bridge without the amp on.  When 
you are done, the amp will see an SWR of 1:1 as can be verified on the SWR 
meter.

You should be able to tune the amp in to your dummy load and when you switch 
it to the tuner and antenna, it should see 50 ohms assuming you can achieve 
a 1:1 SWR with your tuner.  You should never have to transmit a signal on 
the air to adjust your tuner or tune your amp.

73

Howard #3

----- Original Message ----- 
From: "Tom Behler" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, January 01, 2014 10:40 AM
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