The Behringer XM8500 performed exceptionally well. This dynamic microphone is designed for vocals, with both its frequency response and polar pattern tailored for that purpose. This vocal microphone is often compared to the Shure SM-58, which is, however, significantly more expensive. What are the advantages of a dynamic microphone for a transceiver?
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Dynamic Microphones vs. Electret Microphones
Frequency Response of the Behringer XM8500
An electret microphone is lightweight, inexpensive, and features a flat frequency response, high sensitivity, and high output voltage. The polar pattern is usually determined by the mechanical design. These are relatively good microphones for use with a radio in quiet environments.
A dynamic microphone such as the Behringer XM8500 has lower sensitivity, a cardioid polar pattern, and a frequency response that is uneven and narrower in the high-frequency range. The microphone therefore naturally attenuates low frequencies, which are not necessary for communication via a radio, while emphasizing the spectrum above 1 kHz, which helps to flatten the frequency response of the transmitted signal.
How can you convince stations to attempt a QSO?
Imagine a situation where you contact a station with a request for a QSO. Based on experience, you know the connection could be successful. However, the response to your request is a refusal. What can you do about it?
Have you ever wondered why some stations in your area are making contacts, even though your QTH, equipment, and operating skills are similar? Perhaps it’s because they convinced the other station that the contact is possible.
TIP: When is a connection possible?
The basic criteria are the physical limitations determined by frequency, distance, power, antenna gain, and receiver sensitivity. However, terrain often comes into play, as obstacles along the path attenuate the signal.
Signal attenuation in free space is given by the formula:
Au = 20 × (–4.622 – log f – log L)
Au is the attenuation (which is why the numbers are expressed as negative values) in dB, f is the frequency in GHz, and L is the distance in km
Therefore: transmitted power + transmit antenna gain – signal propagation attenuation + receive antenna gain = received power
TIP: How can you increase your chances of establishing a connection?
In the long term, one option is to increase antenna gain. For example, if we increase the antenna gain from 8 dBd to 11 dBd, we gain 3 dB in the equation. We can achieve the same effect by doubling the power. It’s up to us whether we decide to improve the antennas (which will also improve reception) or increase the transmit power.
However, when there are obstacles along the signal path, we also have the option of immediate improvement by utilizing signal reflections, for example, from an airplane. In this way, it is possible to establish a connection even over a significantly attenuated terrestrial signal propagation path.
We can also use means of establishing contact. Typically, this is the ON4KST chat, but communication via other means is not ruled out. However, we must adhere to the rule that we do not exchange connection data via these communication channels. That must take place over the air.
October VHF PA
Sunny, but cold in the morning and still windy weather greets me above the village of Brestovec. The wind is quite strong. I’m considering whether to set up two antenna systems. First, I set up the quadr. I already have experience with this, so it goes quickly.
The mast next to the car has been extended. It’s now over 8 meters tall. However, it bends significantly in the wind. I’m definitely not going to set up a pair of 8-element DK7ZB Yagis—one will be enough. The VHF PA contest showed that even a single antenna was difficult to keep pointed in the desired direction.
I have the setup ready shortly after nine o’clock. I start the generator half an hour before the contest begins. On the band, I find DJ7R, HG1DRD, and other stations. The test contact went off without a hitch.
I start off cautiously—looking for stations sending out a call. Since things are going well, I try calling out my call sign, which results in two or three stations calling me at once on several occasions. This includes stations from greater distances such as E77P, 9A1E, 9A1I, and others. I also managed a contact with SP3KEY from JO71—he confirms that if you really want to, the contact will work out (conversation via the ON4KST chat). In the first hour, I have 41 contacts in the log.
However, the ON4KST chat keeps dropping out, which is a nuisance. The assumption is that this is caused by the new antivirus software on the computer, since the internet connection seems to be stable. Furthermore, the antivirus vendor failed to include an option to easily disable it.
A surprise was I4GHG, who answered the call! The 687-kilometer contact went off without a hitch. After the second of three hours of VHF PA, I had 72 contacts—roughly what I usually get after three hours of operation.
Map of contacts during the October VHF PA at shorter distances
Map of contacts during the October VHF PA at shorter distancesMap of contacts during the October VHF PA
Whenever possible, I look for multipliers, such as OK1DOL. Subjectively, it seems that the lunch hour has emptied the band. During the contact with SP6DHH, the logbook went on strike. A contact with YO5LD is a sure thing—Dani is a very skilled operator, and his signal is excellent as well. I log OK1KQH as the last one. The counter stops at 96.
Points by direction
Several stations praised the signal, which confirms that switching the power source and using the Behringer XM8500 microphone was the right choice.
The result is a surprise: 7,636 points. The 29 contacts with Slovak stations is also a high number. Interestingly, the main source of points did not come from contacts toward the northwest, but rather from the southeast to southwest. Will we hit 100 next time? Let’s wait and see.