Cootcraig Public Blog

Freq. / Wavelength


        λ1 = 3*10^8 m/s/1.6*10^6 Hz = 187.5 m shortest wl 
        λ2 = 3*10^8 m/s/5.5*10^5 Hz = 545.5 m longest wl

Frequency	Wavelength Meters	Wavelength Feet
550k	545m	1788ft
1600k	187m	614ft

Collected Posts

Instructions for Putting up a Long-Wire Antenna

Can you hang a random length wire outside? - Timbo in Oz

Posted by Timbo in Oz (A) on November 15, 2007 at 14:21:35

In Reply to: Antennae loop posted by sown gi on November 15, 2007 at 13:12:51:

use one side of some twisted 300 ohm ribbon as the down lead into the house and to the tuner, connect that side to the AM post and t’other to the gnd post.

then report back. the 1500 IIRC has a decent AM stage.

And one other thing, IF it did originally came with a very small loop, then you may NEED one connected to make the longish random work! OFTEN stated in the manual and true IME

most audio repair shope should have a few Small AM loops lying about.

You realy do still need an aerial as well, this is just a good ground

Posted by Timbo in Oz (A) on November 16, 2012 at 13:57:34

In Reply to: That IS interesting, thanks! posted by 1973shovel on November 10, 2012 at 06:54:24:

A random wire (with a good ground) tuned - by a cap and a tapped coil - to each station - or broadly tuned to cover the ones you want (like mine is) will be a good deal better than just a good ground.

MUCH quieter as the AM stage’s own AGC will cope with the higher input.

A multi-use Antenna Tuner

Antenna Tuning Unit

MDS975 - ATUs - ANTENNA TUNING UNITS

ATUs - ANTENNA TUNING UNITS

Below is the circuit diagram for my preferred choice of a T type circuit which includes a variable attenuator and which could not be simpler to construct. This circuit, with the coil described, covers from 500kHz medium wave to 30MHz short wave. Tuning capacitor VC1 is adjusted to match the aerial side while tuning capacitor VC2 is adjusted to match the receiver side. This circuit is often referred to as a TRANSMATCH, particularly in the USA.

My rooftop AM antenna - youtube

Midnight Science Catalog - Capacitor, 365 air variable

Capacitor, 365 air variable

As the surplus for 365pf caps has dried up, these little beauties were getting harder and harder to find. Not anymore! The Society now has a plentiful supply; we have them manufactured. They are brand new caps, 31 blade, .010-air-gap, 1/4” tuning shaft, and CW rotation decreases capacitance. Testing indicates a capacity range of 390 (fully meshed) to 16 pf (fully open). Shaft accommodates the point knob shown (sold separately), and a reduction drive for slower tuning (also sold separately).

Midnight Science Catalog

AM BAND ANTENNA TUNER KIT

This AM Band Tuner will work with most any crystal radio set. Tuners are attached to the antenna and inductively couple the signal captured into your crystal radio set. By adding the tuner to your station, selectivity and volume can generally be improved.

The backside of the tuner is shown at right. A dual-gang 365 pf capacitor is used to resonate the tuner coil and the antenna system as a whole. The result is an increase in the signal gleaned from the antenna and coupled to the set magnetically. The tuner uses a 6 by 5 inch front panel and a 6 by 8 in chassis. Two switches are used to configure the tuner. In addition, a nylon shaft is added to the tuning capacitor to reduce “hand capacity” while tuning. Kit time is less than one hour experienced builder and should add performance to your crystal radio station.