Monthly Archives: November 2017

My Beverage antennas

There are four bevs:

1. A 110 m unterminated wire in 290 dgs. Works great for North America.

2. A 185 m teminated wire in 240 dgs.

3. A 130 m terminated wire in 60 dgs. Just a little bit better than number 2. Discriminates signals from SW with about 2 S-units. A bit disappointing.

4. A 120 m unterminated wire in 355 dgs.

Common mode measurement of DL1000 telephone cable.

I’ve been a bit sceptical about the balance of the military telephone cable called DL1000 in Sweden. It almost looks as if one wire is wound around the other rather than two twisted wires. So I made a measurement as outlined in the sketch below while listening on strong signals:

As reference I connected both wires in parallel connected directly to the measurement receiver.

The results were:

Frequency     Common mode rejection

7 MHz            25 dB

3.5 MHz         40 dB

There was no difference with and without the load resistor R.

So the telephone line is OK as a feeder for receiving antennas on 80 and below as regards to common mode pick up but doubtful on 40m.

Measuring attenuation of DL1000 military telephone cable.

I was using a 50m length of DL1000 telephone cable with a transformer with binocular BN73-202 at each end with a turn’s ratio of 2:3. There was a MINI VNA Pro used in transmission mode connected to the transformers.

 

 

 

 

 

 

Attenuation in the transformers:

 

Attenuation in transformers plus 50 m of DL1000 telephone cable: