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4 changed files with 93 additions and 61 deletions
48
zk/Antenna_gain_and_ERP.md
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48
zk/Antenna_gain_and_ERP.md
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---
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tags: [radio, ham-study]
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---
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[Antennas](./Types_of_antenna.md) like the Yagi have **gain**. This means they
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can increase the power that they receive from the transmitter via the
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[feeder](./Feeders.md).
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Gain is measured in decibels:
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| Antenna gain | Power muliplied by a factor of... |
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| ------------ | --------------------------------- |
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| 3dB | 2 |
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| 6dB | 4 |
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| 9dB | 8 |
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| 10dB | 10 |
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ERP is the **Effective Radiated Power**. This is the product of the power that
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the antenna is receiving from the feeder and the gain level.
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> ERP (Watts) = power feed x antenna gain
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Some example calculations:
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| Gain | Gain times | Power to antenna | ERP |
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| ---- | ---------- | ---------------- | --------- |
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| 3dB | x2 | 10 watts | 20 watts |
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| 6dB | x4 | 10 watts | 40 watts |
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| 9dB | x8 | 10 watts | 80 watts |
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| 10dB | x10 | 10 watts | 100 watts |
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### ERIP
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ERP is calculated relative to the half-wave dipole. This is the benchmark. The
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power that would be generated using this type of antenna.
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But, as noted above, the dipole has a distinct radiation pattern - diffusing in
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poles at right angles to the horizontal plane of the antenna.
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By being tied to the dipole, ERM is therefore not the most universal or
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objective unit of measurement.
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To remedy this, there is another unit: ERIP. This stands for **Effective
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Isotropic Radiated Power**. It's the same calculation but it uses a theoretical
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antenna that would radiate equally in all directions as the benchmark.
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Because of the equal radiation pattern in all directions, EIRP will always be
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higher than ERP. Roughly speaking, 10 Watts in EIRP would be 6 Watts in ERP.
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12
zk/Antenna_polarisation.md
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12
zk/Antenna_polarisation.md
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@ -0,0 +1,12 @@
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---
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tags: [radio, ham-study]
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---
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**Polarisation** means whether the antenna is positioned on a vertical or
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horizontal plane.
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Of the antennas covered at foundation level, only dipoles and Yagis can be
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positioned at variable polarities.
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VHF and UHF are received most effectively when the transmitter and receiver have
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the same antenna polarisation.
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@ -2,10 +2,12 @@
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tags: [radio, ham-study]
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---
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- Business and any commercial activity is not permitted
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- An amateur radio licence is _only for self-training in radio communications_
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- Ofcom is the UK TV and radio regulator
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- Ofcom issues amateur radio licences
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- Business and any commercial activity is not permitted
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- Ofcom is the UK TV and radio regulator and the body that issues amateur
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licenses
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## Ofcom rules
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**You must**:
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@ -22,7 +24,19 @@ tags: [radio, ham-study]
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- in cases of reported interference, ask you to log the transmissions you have
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made over a specified time period
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**Acceptable operating locations**:
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## The following types of activity are not permitteed
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- Business or commercial activity
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- The use of encryption or codes, other than Morse Code
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- Broadcasting, defined as "transmitting for general reception" (e.g. this would
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constitute "pirate radio")
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- The only scenario where broadcasting is permitted is during the CQ stage,
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when you are seeking a contact to talk to
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- Or when you are operating a "Net", defined as a conversation between three
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or more amateurs where communication is first established with at least one
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individual member of the net
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## Acceptable operating locations
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- UK
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- Channel Islands
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@ -33,3 +47,18 @@ they are in international water or airspace. (Note that TX from aircraft has
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power restrictions as specified in Schedule 1 listings.)
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The Foundation licence does not permit operating in any other countries.
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## EMF rules
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> "EMF" stands for _electromagnetic field_
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The Foundation licence specifies that amateur equipment must not expose the
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public to EMF over a certain threshold. This threshold is **10 Watts
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[ERIP](/zk/Antennas.md) or approximately 6.1 Watts ERP**.
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All amateurs must complete an EMF assessment to demonstrate they are operating
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within the required limits. Ofcom can request an assessment at any time.
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If you are likely to exceed the threshold you must demonstrate that actions are
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being taken to ensure the limits are maintained. If no provisions are necessary,
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you specify that "power levels are below the threshold".
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@ -75,60 +75,3 @@ In contrast to the others, the Yagi is directional and focused in one direction
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It basically works as a dipole with a reflector behind it. This helps to push
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the waves in the horizontal direction of travel, assisted by the director spoke
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in front.
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### Gain and ERP
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Antennas like the Yagi have **gain**. This means they can increase the power
|
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that they receive from the transmitter via the [feeder](./Feeders.md).
|
||||
|
||||
Gain is measured in decibels:
|
||||
|
||||
| Antenna gain | Power muliplied by a factor of... |
|
||||
| ------------ | --------------------------------- |
|
||||
| 3dB | 2 |
|
||||
| 6dB | 4 |
|
||||
| 9dB | 8 |
|
||||
| 10dB | 10 |
|
||||
|
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ERP is the **Effective Radiated Power**. This is the product of the power that
|
||||
the antenna is receiving from the feeder and the gain level.
|
||||
|
||||
> ERP (Watts) = power feed x antenna gain
|
||||
|
||||
Some example calculations:
|
||||
|
||||
| Gain | Gain times | Power to antenna | ERP |
|
||||
| ---- | ---------- | ---------------- | --------- |
|
||||
| 3dB | x2 | 10 watts | 20 watts |
|
||||
| 6dB | x4 | 10 watts | 40 watts |
|
||||
| 9dB | x8 | 10 watts | 80 watts |
|
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| 10dB | x10 | 10 watts | 100 watts |
|
||||
|
||||
### ERIP
|
||||
|
||||
ERP is calculated relative to the half-wave dipole. This is the benchmark. The
|
||||
power that would be generated using this type of antenna.
|
||||
|
||||
But, as noted above, the dipole has a distinct radiation pattern - diffusing in
|
||||
poles at right angles to the horizontal plane of the antenna.
|
||||
|
||||
By being tied to the dipole, ERM is therefore not the most universal or
|
||||
objective unit of measurement.
|
||||
|
||||
To remedy this, there is another unit: ERIP. This stands for **Effective
|
||||
Isotropic Radiated Power**. It's the same calculation but it uses a theoretical
|
||||
antenna that would radiate equally in all directions as the benchmark.
|
||||
|
||||
Because of the equal radiation pattern in all directions, EIRP will always be
|
||||
higher than ERP. Roughly speaking, 10 Watts in EIRP would be 6 Watts in ERP.
|
||||
|
||||
## Antenna polarisation
|
||||
|
||||
**Polarisation** means whether the antenna is positioned on a vertical or
|
||||
horizontal plane.
|
||||
|
||||
Of the antennas covered at foundation level, only dipoles and Yagis can be
|
||||
positioned at variable polarities.
|
||||
|
||||
VHF and UHF are received most effectively when the transmitter and receiver have
|
||||
the same antenna polarisation.
|
||||
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