Introduction Amateur radio VKV PA - October 2022

VKV PA - October 2022

Mapa spojení v októbrovom VKV PA na bližšie vzdialenosti
Map of connections in October VKV PA at closer distances

The Behringer XM8500 did an excellent service. The dynamic microphone is designed for voice, to which the frequency and direction characteristics are adapted. This vocal microphone is often compared to the Shure SM-58, which, however, is significantly more expensive. What are the advantages of a dynamic microphone to a transceiver?

Dynamic microphone and electret microphone

Frequency response of the Behringer XM8500
Frequency response of the Behringer XM8500

The electret microphone is lightweight, cheap, has a balanced frequency response, both high sensitivity and high output voltage. The directional characteristic is usually determined by the mechanical design. They are relatively good microphones for a radio station in a quiet environment.

A dynamic microphone such as the Behringer XM8500 has a lower sensitivity, the directional characteristic in the shape of a cardioid and the frequency characteristic is wavy and narrower in frequency. So the microphone naturally suppresses low frequencies, which are not necessary for communication via the radio station and at the same time emphasizes the spectrum above 1 kHz, which contributes to equalizing the frequency characteristic of the transmitted signal.

How to convince stations to attempt a QSO?

Imagine the situation, that you contact the station with a request for a sked. You know from experience, that the connection could succeed. However, the answer to your request is negative. What about that?

You also asked yourself why some stations from your area establish connections, while the data of your QTH, techniques and operator skills are similar? Maybe it's in that, that they convinced the opposing stations, that connection is possible.

TIP: when the connection is possible?

The basic criterion is the physical possibilities given by the frequency, distance, performance, antenna gain and receiver sensitivity. Often, however, the terrain profile still enters the equation, where obstacles on the route dampen the signal.

The attenuation of signal propagation in free space is given by the formula:

Au = 20 x ( – 4.622 – log f – log L)
Aw is attenuation (therefore, the numbers are expressed as negative) v dB, f is the frequency in GHz, L is the distance in km

After that: sent performance + gain of the transmitting antenna – signal propagation attenuation + receiving antenna gain = received power

TIP: how to increase the chances of a connection?

In the long term, it is possible to increase the gain of the antennas. If, for example, we increase the gain of the antenna z 8 dBd and 11 dBd, we get 3 dB into the equation. We achieve the same effect by doubling the performance. It's up to us, if we decide to go the way of improving the antennas (here we will also improve the income) or performance enhancement.

However, in the case of obstacles on the signal route, we also have the option of immediate improvement by using the reflection of the signal from, for example, an airplane. In this way, it is possible to connect even a significantly attenuated terrestrial signal propagation route.

We can also use the means for a connection agreement. Typically this is ON4KST chat, but the convention in other forms is not excluded either. But we have to follow the rule, that we do not exchange connection data through these communication channels. It has to happen on air.

October VKV PA

Sunny, but in the morning cold and still windy weather greets me above the village of Brestovec. The wind is quite strong. I am considering whether to build two antenna systems. First I build a square. I already have experience in this, it goes fast.

The mast for the car was increased. It achieves more than 8 meters. However, it bends significantly in the wind. I'm definitely not going to build a pair 8-element DK7ZB yagi, one will be enough. The course of VKV PA showed, that even one antenna was difficult to keep in the desired direction.

I have the setup ready shortly after nine o'clock. I start the power plant half an hour before the start of the contest. I find on the band DJ7R, HG1DRD and other stations. The test connection went without a problem.

I start more cautiously - I look for stations giving a challenge. Since things are going well, I also try the challenge, as a result of which two or three stations call at the same time several times. And even from greater distances than E77P, 9A1E, 9A1I and others. The connection with SP3KEY from JO71 - confirms, that when you want, so the connection succeeds (convention via ON4KST chat). In the first hour it is in the log 41 link.

However, the ON4KST chat keeps dropping out. The assumption is, that it is caused by a new antivirus on the computer, because the internet connection seems to be stable. In addition, the antivirus producer omitted the possibility of a simple shutdown.

It's a surprise I4GHG, who answered the call! Connection to 687 kilometers passed easily. After the second of three hours of VKV PA I had 72 connections - I have about that many after three hours of operation.

Map of connections in October VKV PA at closer distances
Map of connections in October VKV PA at closer distances
Map of connections in October VKV PA at closer distancesMap of connections in October VKV PA
Map of connections in October VKV PA at closer distancesMap of connections in October VKV PA

if it's possible, I look around for multipliers, for example OK1DOL. It seems subjective, but the lunchtime zone emptied. When connecting with SP6DHH the newspaper went on strike. Connection with YO5LD it is certain - Dani is a very skilled operator and the signal from him is also excellent. I am the last to log in OK1KQH. The counter stops at a number 96.

Point gain according to direction
Point gain according to direction

Several stations praised the signal, which is confirmation, that source exchange, using the Behringer XM8500 microphone is correct.

The result is a surprise, 7636 points. Aj 29 connection with Slovak stations is a high number. It is interesting, that the main point increase is not represented by connections towards the northwest, but to the southeast to southwest area. A hundred will fall next time? Let's be surprised.