464
Item nr.


Gerard Loop Antenna Monitor

Check antenna operation.


Data for Gerard Loop Antenna
ProductionThe Netherlands, 2017.
BandsAM, roughly 150 - 3000kHz.
Semi-
conductors
TA7642.
CabinetPlastic profile.
PowerBatt 1.5V (AA, soldered).
DocumentsSchema.

The Design

In 2017, I built and bought myself a few loop antenna's. I decided to use some of my TA7642 stock to work out a small monitor.

The monitor connects to a loop antenna, which is basically a tuning tank, so it need not contain a tuning circuit. Also, I found a 700 Ohm earpiece in my junk, eliminating the need for R1 in the classical TA7642 basic circuit, altogether now reduced to the IC plus three electric components. The AA battery can be soldered, providing a reliable long term connection.


Obtained6/2017 from Home built.
Condition9.
DisposedStorage (inquire if interested to buy).

This Object

Putting this piece together took less time than to relocate the 3.5mm plug I had saved apart for this purpose. Because the TA7642 has a fairly high input impedance, I tried it both on the output of my TelRaam and directly on the tuning tank. The direct connection gave less stations and caused generation on the lower MW. So, the low impedance output is the place to be, and I attached the male coax connector.

At first I considered the idea of building the entire unit (with a watch battery) in a coax male plug. But studying the size of the inside of this plug made me abandon this plan. I built the monitor on June 26, 2017, and immediately received five MW stations using my TelRaam antenna: 621kHz Wavre (Belgium, French), 693 (BBC5), 1008 (GrootNieuws), 1053 (TalkSport, English), 1584 (R.Pardijs). Especially the English station on 1053 was quite a surprise to me, as its frequency is quite close to GNR (1008). I found out that the null in the directionality of my antenna is not equally sharp on both sides. If I try to null GNR on one side, it does not disappear sufficiently to hear Talk, but turning the antenna over 180 degrees completely silences GNR and opens Talk.


Part of Gerard's Radio Corner.
Generated by SiteBuilder on 26/2/2024 by Gerard (g.tel@uu.nl)