> Can anybody tell me it is worth having? It is marked Aerial Tuning
> Unit No.9 ZA 476 80 D^D then embossed MPH 1959 and a serial number. It
> has a meter in the middle (swr?) of a two coax terminals. It looks
> somewhat over engineered to say the least. The twins love it because it
> has a dial and a knob or two: what era of HF is it from? 50's or 60's or
> 70's or what. It is approx. 6inches by 5inches wide by 5 inches deep.
> I have put some mog links on my web page.
Don't know the model Ross, but I do know what it does, and how. The ATU
is used to tune high-impedance antennas, ie antennas that do not have
a 50 or 600-ohm output. Most military vertical whips of the period were
high impedance, and having a natural wavelength of about 13-20 Mhz. They
were used on frequencies in the range 3-12 Mhz mostly depending on
manufacturer. I believe I have a very complete band-plan lying around
here somewhere. Anyway, it was done this way so that the antenna could
be tuned over the whole range of its frequencies without the natural
resonance that can be a problem in wide-band applications such as this.
The knobs you mention are probably "Load" and "Tune", which change the
amount of series inductance and parallel capacitance which the antenna
presents to the radio. The meter in the middle isn't an SWR meter, it is
for a built in RF level detector (kind of a diode-bridge). The antenna was
simply tuned for max deflection on the meter by using the "Load" knob,
after tuning for dip by using the "Tune" knob.
As for it being worth something... Well, unless you run into somebody who
just happens to be looking for one of that make and serial number.....
toss it away mate....
Regards
Gerry