Category Archives: Okategoriserade

What is e.i.r.p.

Effective Isotropic Radiated Power (e.i.r.p). What is it?

e.i.r.p. = Pout (from TX) – losses (in antenna and feeder etc) in dB + antenna gain in dBi.

The regulations for 5 MHz in Sweden with max 15 W e.i.r.p. will have some strange consequences:

An inverted vee dipole with apex at 13 m has a gain of 6.7 dBi. If losses in tuner and feedline amount to 1 dB, Pout should be 5.7 dBs lower than 15 W or 4 W. It holds for an antenna over even ground with average conductivity.

For a vertical ¼ wave GP with 2 to 4 radials at 2 m Pout max is rather 30W.

Click on the image for a better view.

Inv vee dipole at right angle to the antenna plane:                           Vertical:

Military telephone cable as the antenna wire. How big are the losses?

The DL-1000, which is the defense’s telephone wire, consists of 7 strands. 4 from copper and 3 galvanized steel wires and an insulating coating. It is popular as antenna wire. The question is how it stands against copper wire regarding losses on short wave.

The MMANA simulation program allows you to select materials in the antenna conductors. The difference in material losses between copper and steel wire amounts to more than 3 dB for a 20m dipole.

To make a practical measurement, a dipole for 14 MHz was mounted with the center 7 meters above ground and the ends one meter lower. A MINI VNA was connected to the 37 meter long RG 213 coaxial cable and the length was retracted. However, the cable is simulated as loss-free.

In addition to 1.5 square mm copper, 1 mm plastic coated soft steel wire was used, which is used in the garden.

The feed impedance was measured at the resonance point when it was pure resistive.

Results:

Impedance ohm

Copper         53

DL 1000        64.7

Steel wire     74.2

 

Thus, an additional loss resistance of 11.7 ohm for DL ​​1000 and 21.2 ohm for steel wire. This corresponds to 18% or 0.85 dB extra power loss for DL ​​1000 and 28.6% or 2.3 dB for the steel wire.

Additional information:

The DC resistance of a strand of DL1000 is 7 ohms/100m.

My Beverage antennas

There are three bevs:

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

2. A 185 m unterminated wire in 240 dgs. Great both ways.

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.

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:

 

 

Replacing the Beverage feeding system

I’m replacing my Beverage feeding system. The relays in the switchbox was powered through the feeder which was 40 m of buried RG-6 coax plus 70 m of military phone line in the trees. I had problems with noise from the relay voltages so now replacing it with buried outdoor UTP cable feeding the relays separated from the RF feeder.

The impedance of a UTP pair is 100 ohms and measured attenuation over 100 meters was as follows:

1.8 MHz                1.5 dBs

3.5 MHz                1.7 dBs

10.1 MHz             2.6 dBs

I took the transformers from the old 70 ohm system and measured the 50 ohm SWR all the way through 100 m UTP to a 560 ohm resistor in place of the Beverage wire:

The SWR was 1.35 at 1.8 MHz, 1.05 at 3.5 MHz and 1.55 at 10.1 MHz

 

Today Oct 4, the new beverage feeding system is up-and-running. Works as expected but the ground lead is too long picking up too much signal, especially on 40 and up. Had to move the relay unit from one tree to another. Will try to improve that.

Today November 8 I improved the ground with an extra ground stake. There is also a new NE wire running at 65 Dgs. It’s a 130 m long terminated wire.

 

Aurora and sporadic E

On 21st of December 2016 local K-index was 8 (with 9 as theoretical maximum) with severe aurora. Strange things happened. Sort of sporadic E (or maybe sporadic F) was formed by the strong radiation. So had a QSO with W9YXX in Indiana on 20, late in the evening with 599 signals. Normally the band closes early.  At such occasions the propagation is very patchy. I got a 31 dB RBN spot from WZ7I and a 27 dB spot from K3LR. No spot from anyone else in Europe or anywhere.  I was the only EU station heard at his end he was the only station heard here except for C91PA who was 59 on 20, SSB. The noise was virtually zero with the needle stuck at the bottom stop.

Part of the QSO with W9YXX:

 

So great fun in spite of non-existing normal propagation

Antennarbeten

2016-09-07

Tänkte prova 30m-tillsatsen för min A3WS. Den har legat och väntat i garaget i kanske 15 år. Filosofin har varit att passa på och montera den när det uppstod ett problem på beamen och jag skulle bli tvungen att ta ned den. Nu har ett fästband som hållit koaxen mot bommen gått av. Dags att agera.

Det visade sig bli ett större jobb än vad jag trott. För att kunna ta ned WARC-beamen måste jag ta ned min dipol för 40m och min trebandare FB-53. Jag tillverkade en linbana enligt tips på nätet. Det visade sig vara lättare sagt än gjort att få ned antennerna. Allting trasslar sig med allting och det som ska fungera i teorin har allvarliga brister när det kommer till verkligheten.

Idag har jag i alla fall fått ned 7 MHz-dipolen och FB-53an. Återstår A3WS.

2016-10-24

Efter ett par veckor sitter alla antenner på plats. 30-meterstillsatsen på WARC-beamen går förträffligt. 25 meters höjd verkar passa den bra.

FB-53an har sänkts i frekvens på 20 meter till 14070 kHz. I original ligger den på 14225 kHz. Det förbättrade SWR och F/B-förhållandet på CW-delen. Dessutom monterades 3 cm långa pinnar före trappsen på den närmsta 10/15-metersreflektorn för att försöka förbättra F/B-förhållandet på CW-delen på 10 meter, men det verkar inte ha haft någon större efekt.

Inför lågbandssäsongen har en 160-metersdipol hängts upp och ett parasitiskt element har satts parallellt med befintlig Invvee-dipol. Den antingen direktor eller reflektor genom att ändra längde ett par meter. Riktningarna är SV eller NO. Dessutom finns en inverted vee-dipol med bredsidan NV/SO.

A comparison of Cushcraft A3S and Mosley PRO-96

On August 14, 2016 in the afternoon these two antennas were run against each other at SK0QO’s QTH on Gålö South of Stockholm. They were mounted on separate masts about 18 meters above the ground with water in front in a northwesterly direction. The test was done using the Reverse Beacon on 20m towards North America. The power was 100 watts.
Receiver          A3S dB SNR spots    PRO96 dB SNR spots
W1NT             11, 9                            9, 11
W3UA            19, 23                          16, 23
KM3T             19, 20                          17, 22
K1TTT            6                                   5

This gives that the A3S was on average 1.5 dB stronger than the PRO-96