[Hallicrafters] RTMA Dummy Antenna needed for alignment?

[Jim Wilhite]

I don't need it, I have the dummy antenna accessory, 10 and 20 db 
attenuator pads that came with the URM generator.  Several years ago I 
used the antenna accessory to tune the receiver, then used the 50 ohm 
dummy antenna to compare.

I could not hear  any real discernable difference, so I don't use it 
since all my antennas are near 50 ohms.  As stated before, it was for 
lab measurements which I no longer care about.  Now when I taught 
students we covered the necessity of using the proper matching 
techniques so the measurements for Metrology would be verifiable.  But 
now this is just fun.

These things are nice to have but really not necessary.

Jim/W5JO

----- Original Message ----- 
From: "Roger D Johnson" <n1rj at roadrunner.com>

> If you have a 50 Ohm generator, and you want reasonably accurate
> measurements, you can use a matching pad. This ensures the generator
> is properly terminated and that the receiver sees it designed input
> impedance. In addition, you can design the pad for a known amount
> of attenuation which will allow accurate sensitivity measurements.
> Pads for 200, 300 and 450 Ohms at 20db attenuation should cover most
> all older receivers.
>
> Here is a program for designing pads:
>
> http://www.smeter.net/electronics/padmatch.php
>
> Most folks also recommend a pad for straight 50 Ohm systems to damp
> out any impedance variations between rx and generator.
>
> 73, Roger
>