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ДНД на КВ антени спрямо а...
Форум: Антени
Последна публикация: mzk
23-09-2021, 08:19 PM
» Отговори: 0
» Разглеждания: 21
Йонограми и разчитане на ...
Форум: Радиолюбители
Последна публикация: mzk
20-09-2021, 12:29 AM
» Отговори: 0
» Разглеждания: 39
NVIS Near Vertical Incide...
Форум: Разни
Последна публикация: mzk
12-09-2021, 08:57 PM
» Отговори: 0
» Разглеждания: 117
Приземна вълна
Форум: Разни
Последна публикация: mzk
12-09-2021, 08:54 PM
» Отговори: 1
» Разглеждания: 161
Конструиране на 5/8 антен...
Форум: Антени
Последна публикация: mzk
29-08-2021, 10:11 AM
» Отговори: 0
» Разглеждания: 184
Схеми, ремонт и модификац...
Форум: Антени
Последна публикация: mzk
29-08-2021, 10:05 AM
» Отговори: 0
» Разглеждания: 182
Мощен линеен стабилизатор...
Форум: Линейни захранвания
Последна публикация: mzk
13-08-2021, 10:24 AM
» Отговори: 2
» Разглеждания: 456
Смесители / миксери
Форум: Радиа (приемници и предаватели)
Последна публикация: mzk
11-08-2021, 10:14 AM
» Отговори: 1
» Разглеждания: 404
Квадратурен детектор
Форум: Радиа (приемници и предаватели)
Последна публикация: mzk
11-08-2021, 09:45 AM
» Отговори: 0
» Разглеждания: 239
EFHW антени (крайно захра...
Форум: Антени
Последна публикация: mzk
10-08-2021, 11:28 AM
» Отговори: 0
» Разглеждания: 265

  ДНД на КВ антени спрямо антенната височина
Публикувано от: mzk - 23-09-2021, 08:19 PM - Форум: Антени - Без отговори

ДНД на хоризонтални диполи


The gain also depends on the ground conditions. This plot shows gain vs. height for an 80m dipole over 4 types of ground, to give a sense of the variation:
Notice that the peak of the gain curves are very broad, somewhere between 0.13 wavelengths (10m, 35 feet) and 0.25 wavelengths (20m, 65 feet) depending on soil characteristics. However, for any of the soil conditions, a dipole at 0.07 wavelengths (6m or 20 feet), as shown by the red arrow, is within about 3 dB of the peak, and, especially for portable operation, this may be more practical height. With an inverted vee, try to keep the ends at least half that height above the ground. At lower heights, ground losses increase, although contacts are often still possible with the antenna 1m (3 feet) above the ground, or even less.

TO = take off angle


ДНД на вертикални диполи / маркони


  Йонограми и разчитане на йонограми
Публикувано от: mzk - 20-09-2021, 12:29 AM - Форум: Радиолюбители - Без отговори

Световна карта н F2: https://www.sws.bom.gov.au/HF_Systems/6/5
Белгия: https://digisonde.oma.be/ionogif/latest.html
Италия: http://ionos.ingv.it/roma/latest.html
Полша: http://rwc.cbk.waw.pl/iono/
Германия: https://www.iap-kborn.de/fileadmin/user_...LATEST.PNG
Гърция (иска регистрация): http://www.iono.noa.gr/


Цитат:An ionogram is a graph of time-of-flight against transmitted frequency. Each ionospheric layer shows up as an approximately smooth curve, separated from each other by an asymptote at the critical frequency of that layer. The upwardly curving sections at the beginning of each layer are due to the transmitted wave being slowed by, but not reflected from, underlying ionisation which has a plasma frequency close to, but not equaling the transmitted frequency. The critical frequency of each layer is scaled from the asymptote, and the virtual height of each layer is scaled from the lowest point on each curve.
An ionogram can be much more complicated than just two layers. There can also be such phenomenon as;
  • The F1 layer. An additional layer which appears in the F region, between the two existing peaks. To tell the two Flayers apart, the upper layer is referred to as the F2 layer, and the lower layer the F1 layer.

  • Sporadic E, Es. This layer is a patchy, very dense layer sometimes exceeding 16 Mhz (3.1 x 10^11 /m^3). Despite their intensity, these layers do not extend over a large height range, and so do not exhibit an asymptote at the critical frequency, as the transition is too sudden. They appear on an ionogram as a narrow horizontal line at around 100km. An intense Es layer can prevent any echoes from reaching the upper layers This is known as blanketing.

  • Multiple hops The return signal can skip from the Earth to the ionosphere and back again, sometimes several times before it is attenuated. These multiple echoes appear on an ionogram at multiples of the original virtual height.

  • D-region Absorption. This is caused by ionisation in the D-region that absorbs the transmitted wave before it can return to the ground. This absorption is characterised by no echoes being received from the low frequency end of an ionogram.

  • Lacuna. When turbulence occurs (as the result of large electric fields for example), the stratified nature of the ionosphere gives way to a more complex structure. Under such conditions, the reflected signal may not reach the receivers, and so the height range at which the turbulence occurs is lost on the ionosonde trace. Such gaps are termed Lacuna and their position on an ionogram gives some indication as to the height at which the turbulence is occurring.

  • Spread-F. With an ionosonde, echos are received from any portion of the ionosphere where the electron density gradient is perpendicular to the transmitted wave. This most often happens overhead, but occasionally conditions exist such that echoes from other regions of the sky return to the ionosonde. If the electron concentration in these regions differs from the ionosphere overhead, two traces are observed. For a given angle from the zenith, the horizontal separation is greatest in the F-region, and so differences in ionospheric conditions are most likely to be observed in the F-region. If the geometry is right for echoes to be received from a whole range of locations and the ionospheric conditions vary over that range (such as when a trough is overhead) multiple traces will appear on an ionogram, and the F trace is said to be 'spread'. With a digital ionosonde, such as the Dynasonde, these traces can be resolved by considering the horizontal position of each echo.


Цитат:Previously on Wireless Waffle we have discussed ways of checking and even gaining some knowledge of the state of propagation of the short-wave bands. But for truly advanced users, there is a way to find out the actual state of propagation for a particular location in real time. Scattered around the world are a series of ionosondes. These ionosondes are rather like radars in that they transmit a signal to the ionosphere and measure the time taken to get a response. They do this across a range of short-wave frequencies.

The result is a chart called an ionogram. An ionogram is effectively a radar picture of the height of the ionosphere at the location immediately above the ionosonde as well as providing an indication of its refractivity, over a range of frequencies. An example ionogram taken from the ionosonde in Dourbes, Belgium, is shown below.


The ionogram is the ultimate way of assessing short-wave propagation. It tells us exactly what is going on. To help interpret the ionogram, there are also a useful set of figures provided in the diagram which give us some very useful information. So... how do we interpret the ionogram to help understand HF propagation?

In the ionogram above, the strong red/pink line extending from just below 3 MHz to just above 6 MHz shows that the ionosphere above Belgium was refracting radio signals in that frequency range straight back down again (ie at an angle of 180 degrees) - it was acting like a mirror for radio frequencies in this range. As the frequency goes above 6 MHz, the line bends upwards until eventually it goes off the top of the chart. This is the point at which the ionosphere stops refracting signals back down (at 180 degrees), however it will continue to refract signals at higher frequencies which hit it at lower angles (less than 180 degrees).

From this simple data, together with the height of the ionosphere (the scale up the left hand side of the chart) it is possible to calculate a number of very useful figures, and this is done for us.

Firstly, we have the maximum usable frequency (MUF). This is shown amongst the figures to the top right of the chart (in this case 27.62 MHz) and is also repeated at the bottom of the chart (under the label 3000 km). The MUF is the highest frequency which the ionosphere will reliably reflect radio signals. It is also the one which has the lowest refraction angle. What this means is that signals at this frequency will be refracted by the ionosphere (above Belgium in this case) but only where the path between the ends of the link hits it at a low angle, which equates to a path length of around 3000 km. Two stations, each 1500 km away from Belgium, the centre of whose path is above Belgium, will therefore be able to communicate at a frequency of 27.6 MHz. So a station in Western Ireland and one in Romania are likely to be able to communicate on this frequency. Equally one in Spain and one in Sweden might too.

The second useful frequency shown is the one shown as 'foF2' in the diagram (top right). In this example foF2 is 7.15 MHz. foF2 is the highest frequency at which the ionosphere above Belgium will refract signals at an angle of 180 degrees, ie straight back down. If you therefore want to communicate from somewhere in Belgium, to the same place in Belgium, using the ionosphere, this is the highest frequency I can use. How useful! But the best bit is the interpolations between foF2 and the MUF. These are the figures shown at the bottom of the chart under the various distances (from 100 km to 3000 km). These are the maximum frequencies I can use to communicate over the distance shown.

In this example, if my path length is 100 km, the highest frequency I can use is 7.9 MHz. If my path length is 1000 km, the highest frequency I can use is 11.7 MHz. Now this is really useful. If I want to communicate from London to Stuttgart, a distance of approximately 800 km, of which Belgium is roughly half way (in the centre of the path) the highest frequency I could use, in this instance, is 10.2 MHz.

What is the lowest frequency I could use? That is more difficult. What the diagram does tell us, however, is that for short paths, (ie from Belgium to Belgium) the ionosphere was successfully refracting signals at frequencies as low as 3 MHz. How do we know this? There is a nice red/pink reflection on the chart at this frequency. Below it, the picture becomes rather scattered indicating that the refracted signal was not reliable.

So, what can we ascertain:
The highest frequency being refracted by the ionosphere above Belgium is around 27.6 MHz. This is the highest frequency at which two stations separated by 3000 km for whom Belgium is in the centre of their path, will be able to communicate - the MUF.
The highest frequency which can be used to communicate from one location to the same location (in Belgium) using the ionosphere is 7.15 MHz - foF2.
For a range of distances, we can work out the maximum frequency which can be used.
For short paths, we can find out the lowest possible frequency being refracted by the ionosphere (around 3 MHz in this case) and thus the lowest frequency which can be used.

We can also take a stab at assessing how strongly the ionosphere is refracting. The phantom reflections shown at around 450 km height are signals which were refracted from the ionosphere, then reflected by the earth and then refracted again by the ionosphere. These phantom reflections would tend to suggest that the strength of refracted signals is particularly good, as it has been strong enough to rebound from the earth and refract again! Sometimes, three or even four phantoms can be seen, indicating very strong refractions which would suggest that short wave signals would be very strong.

Прикачени файлове Миниатюри

  NVIS Near Vertical Incidence Skywave
Публикувано от: mzk - 12-09-2021, 08:57 PM - Форум: Разни - Без отговори


Прикачени файлове
.pdf   nvis.pdf (Размер: 313.38 KB / Сваляния: 0)

  Конструиране на 5/8 антена (+ инструкция за бобина)
Публикувано от: mzk - 29-08-2021, 10:11 AM - Форум: Антени - Без отговори



146MHz 5/8 ground plane tower mounted antenna. Install December 2010
Requiring a new 2 metre band antenna for local FM simplex and repeater communication and after evaluated a couple of the main contenders for the project I settled on the 5λ/8 wave ground plane to be designed for approximately 146.5MHz.
The reason for selecting the 5λ/8 wave ground plane is that for a simple single element antenna it appeared to have increased capture aperture when compared to the standard λ/4 wave length ground plane antenna and has a relatively low angles of radiation in comparison with other similar antennas.
The decision to proceed with the 5/8 wave ground plane antenna was largely based information and analysis provided by the RSGB's. VHF UHF Manual - fourth edition by G. R. Jessop, G6JP

The increased capture aperture or gain for single radiating element increases as the radiating element length is increased until the length of the radiator exceeds the magical 5λ8 wave length at which point the increasing radiator length causes the radiation pattern to begin breaking up into a number lobes and nulls. The optimum length is in fact equal to or slightly less than 0.6λ.
The standard quarter-wave radiator loads up against a ground plan with a typical impedance of 36Ω which will match the standard 50Ω coax feed line with a SWR (standing wave ration) of about 1.5 to 1. Figure 1 show the impedance distribution along the radiating element of a typical λ/4 ground plan antenna with the ideal low impedance at the feed point. When the radiating element is extended out to a half-wave length we are now looking at a high impedance node at the feed point as shown in figure 2 that is impossible to match with the 50Ω coax feed line without some sort of matching circuit. If however the radiator element is increased to a 3/4 wave length the feed line will see an impedance value at the feed point that is similar to that of the quarter-wave radiator as shown in figure 3, however while this overcomes the matching issue the 3/4 wave length introduces a poorer radiation pattern.
The trick is to make the 5λ/8 radiator appear to the feed line as if it were a 3/4 wave length; establishing a good impedance match while at the same time achieving the ideal low angle of radiation that can be realised through the 5/8 wave radiator. By add a series loading coil at the base of the radiator to compensating for the lost λ/8 section a match of close to 50Ω can be obtained as shown in figure 4. It is also much easy to design a matching circuit for a 5λ/8 radiator than the more extreme impedance presented by the 1λ/2 radiator.
Figure 1  λ/4 Radiator Impedance
Figure 2  λ/2 Radiator Impedance
Figure 3  3λ/4 Radiator Impedance
Figure 4  5λ/8 Radiator Impedance

Having reviewed a number of designs I decided that the simplest approach was to cut a sample radiator to the physical 5λ8 for 146.5MHz reducing the overall length by about 5% to allow for the material physical diameter and then forming a loading coil from a λ/8 equivalent length of enamelled coated copper wire.  The size of the loading coil is then adjusted until a sufficiently good match is achieved.
The design consists of a re-hashed commercial whip antenna that was design for an unknown frequency, possibly low band VHF. The original antenna consisted of a stainless steel whip mounted on an insulated tube containing some sort of loading coil. After cutting thought the bottom end of the tube too asses the construction the existing loading coil was removed.
At this point it was decided to wind the new loading coil over the outside of the insulated tube and soldered the coil tails to the tube end caps, allowing for easy removal and experimental adjustment of the coil. The length of the loading coil wire was determined by the physical length of λ/8 at 146.5MHz less 5% to allow for the effect of the wire diameter and less the length of any metal antenna hardware between the bottom end of the coil and the attachment with feed line.  The additional tail from the top of the coil would ultimately be deducted of the final length of the 5λ/8 radiator as it would be part of the radiator.
Photo 1  Installed re-designed matching coil using recovered insulated tube.

There are two loading coil configuration for the 5λ/8 radiator. The first being popular with commercial mobile manufactures and which is also the approach that I have taken, which is to simply add the loading coil in series with base of the radiator. See fig 5. The second slightly more complicated method to set up is to ground the base of radiating element to the ground plan via the coil and tap the feed line into a the coil as in fig 6. The second method is in many way superior in that it allows the antenna to be turned to resonance eliminating any reactive component while achieving a perfect match to the 50Ω coax feed line. The first method is a bit of a compromise in that to achieve a good match to the feed line; however the antenna may be some what reactive.
The second method has the benefit that when the antenna is mound high on a mast that the entire antenna is at DC ground and will give some lightning protection to attached equipment. While the second method requires a lot more trial and error, it represents the superior approach and is intended to be employed on future prototype antennas of this type.
Figure 5 Series matching coil
Figure 6 Grounded matching coil

Despite the antenna and mounting hardware being of a reworked mobile vertical antenna, the intention is that it be used as mast mounted antenna and therefore feed it with something better than RG58.  A solution was to redesign a standards mobile antenna mount with a Female 'N' type coax cable connector that would be robust and more importantly weather proof.
Photo 3  Standard mobile antenna mount adapted to the ground plane assembly - Top view
Below is an explanation of how the standard mobile antenna mount was modified to for the feed attachment for the ground plane antenna. It is important to remember that mobile antenna mount of this type vary considerably in the design and any attempt to duplicate the this process should use this description as a guide only.
Figure 7 Explanation of how the standard mobile antenna mount was modified for the feed attachment for the ground plane antenna.
A - Retaining nut.
B - Weather proof cone.
C - Aerial mounting stud and insert guide.
D - Coax screen ground insert. (Remove, not required)
E - Ground plane mounting base.
F - Standard N connector (Female)
The standard mobile antenna mount is disassembled with the coax screen ground insert being discarded and the insert guide skirt of the aerial mounting stud assembly trimmed so that it remains flush with the bottom of the weather proof cone when assembled. The female N connector is pop-riveted to the ground plan base disc and the aerial mounting stud is connected with a very short and flexible lead to the female N connector centre pin. The weather proof cone is then seated over the aerial mounting stud and fixed in place with two self tapper screw to the ground plan base disc from beneath. A light bead of marine grade silicon is applied to the bottom of the weather proof cone before it is attached. The retaining nut is then installed with care not to over tighten. See below complete assembly.

Photo 4  Standard mobile antenna mount adapted to the ground plane assembly - Side view

With the antenna assembled on an easily accessible test mast well clear of the ground and surrounding metallic objects, the antenna was connected to an AIM 4170C antenna analyser to ascertain how the antenna loaded up.
The goal here is to find the operating frequency of 146.5MHz compromise between being close to the resonant frequency and achieving best possible impedance match resulting in an SWR of about 1.5 - 1 or less.
The AIM 4170C produces a display of all relevant data and most importantly it can project it's analysis to the antenna end of the coax giving a truer picture of the antenna.
The initial plot indicated that the antenna was resonant around 135MHz, while the 5/8 radiator can be trimmed at the final tweaking stage the most important feature of this antenna is to maintain a radiator length of slightly less than the 5/8 wave length, therefore the first component of the antenna to be adjusted is the loading coil. One complete turn was removed at the first attempt resulting in the analyser indicating a good SWR and resonant frequency of around 152MHz. Third time lucky, after winding a new loading coil with a third of a turn more than the previous coil the result showed a resonant frequency of around 146MHz after a bit of fine adjustment by compressing the coil a little.
Finally with only the most modest trimming of the radiating element the required parameters were realised with a resonant frequency of 146.5MHz and a SWR of 1.32 at 146.66 MHz.
It is important that the heat shrink tubing that will be used to weather proof the loading coil assembly is slipped over the coil to reveal the effect that it will have when it is finally shrunk into place as the effect of the heat shrink tubing lowers the resulting ideal frequency by as much as 1MHz. Once shrunk the ideal frequency is lowers slightly further.  Requiring a bit of guess work a very close result is not at all difficult and a bit of trimming of the main element will allow target specification to be achieved.

AIM 4170C antenna analyser explanation;
Standing Wave Ratio.
Total Impedance.
Resistive component of the total impedance
Reactive component of the total impedance also indicating the +/-sign of the value. Inductive being a positive value and capacitive being a negative number.
Phase angle between voltage and current.
Return Loss
Total reflected system loss.
I have been surprised at how little detail information actually exists on both the internet and resource book regarding the principles and performance of 5/8 wave ground plane and similar antennas. There is much discussion related to theoretical gains in comparison with similar antenna types, but little about the hash reality of real world antenna performance.
With some on air comparisons and antenna modelling there appears to be no dramatic performance advantage between for example a simple λ/4 ground plane and that of the 5/8 wave ground plane.
It appears that while the 5/8 wave ground plane exhibits some improvement in performance in comparison with the simpler λ/4 ground plane the big performance improvements for 144MHz and high is as everyone knows antenna height and high quality low loss coax.
This project has challenged a number of personal antenna myths, created the necessity of a bit of experimental tinkering along with detailed measurements and test to produce a new station antenna that has met the original design goals.

RSGB. VHF UHF Manual - fourth edition by G.R.Jessop, G6JP

For an example of a practical development of a 5/8 wave vertical antenna for the 4mtr band see: http://www.acanas.co.uk/g4zlz.co.uk/4met...tical.html

Article on Degrees of Antenna Occupied by a Loading Coil.
The purpose of this article is to provide a procedure for determining the number of degrees of antenna occupied by a loading coil. A later article will explain how that value applies to inductively loaded mobile antennas.
See: http://www.w5dxp.com/

A comparison of 10 meter verticals using modelling see: http://home.comcast.net/~nm5k/acompari.htm

A very interesting discussion on news group: rec.radio.amateur.antenna. regarding the comparison between 5/8 vertical and J-Pole antennas including lengthy discussion on 5/8 vertical performance. See complete discussion: Which is better: 5/8 wave vertical or J pole

Прикачени файлове Миниатюри

  Схеми, ремонт и модификация на фабрични антени
Публикувано от: mzk - 29-08-2021, 10:05 AM - Форум: Антени - Без отговори

Diamond X30

Diamond VX400

Diamond X500

Diamond X510N


  Мощен линеен стабилизатор с няколко LM338
Публикувано от: mzk - 12-08-2021, 10:47 AM - Форум: Линейни захранвания - Отговори (2)

Целта е да се направи филтриране на шумовете от импулсно захранване, като се използва мощен линеен стабилизатор. Захранването е за радиостанция. В спецификацията на LM338 е дадена схема за пралалелно свързване на няколко стабилизатора.

При пад на напрежение между 2 и 3 волта загубите при максималния ток от 15А биха били между 30 и 45 вата. В режим на покой и консумация на станцията от около 10 вата (около 1А), загубите биха били около 3 вата.

Прикачени файлове Миниатюри

  Смесители / миксери
Публикувано от: mzk - 11-08-2021, 09:53 AM - Форум: Радиа (приемници и предаватели) - Отговори (1)


Прикачени файлове
.pdf   lect15.pdf (Размер: 281.68 KB / Сваляния: 0)

  Квадратурен детектор
Публикувано от: mzk - 11-08-2021, 09:45 AM - Форум: Радиа (приемници и предаватели) - Без отговори


Това е извадка от инструкция за направа на УКВ радиоприемник. Цялата поредица от горепосочения сайт е много интересна и информативна.

Една от основните идеи за използването на квадратурното семплиране при приемниците с пряко преобразуване е да се избегне загубата на сигнал, ако фазите на приемания сигнал и локалния осцилатор не съвпадат. (тъй като честотата на локалния осцилатор съвпада с честотата на приемания сигнал, ако те се различават с 90 градуса, резултатът ще е 0, т.е. липса на сигнал).

Цитат:The Quadrature Sampling Detector stage ("QSD" - Quadrature Sampling Detector) acts like two traditional direct conversion mixers operating in tandem. Each takes in half of the filtered and down-converted RF from the RF/Control and one of the quadrature center frequency signals, then "mixes"/down-converts them to with an output being the traditional mixer products, in this case, two (infra) audio frequency signals that represent the difference between the two inputs (down-convertedRF and Local Oscillator). These two signals are referred to as the detected I (in-phase) and Q (Quadrature) signals and are fed into the high gain Op-Amps stage for amplification and delivery to the audio outputs (and, thence, to the PC's sound card).


  EFHW антени (крайно захранени полувънови антени)
Публикувано от: mzk - 10-08-2021, 11:28 AM - Форум: Антени - Без отговори



  J-Pole антени
Публикувано от: mzk - 01-08-2021, 10:49 AM - Форум: Антени - Без отговори

Сравнение на 1/2 с 5/8 вълнова J-pole