💾 Archived View for gemini.rawles.net › radio › my › antennas captured on 2021-12-04 at 18:04:22. Gemini links have been rewritten to link to archived content

View Raw

More Information

⬅️ Previous capture (2021-11-30)

-=-=-=-=-=-=-

📡 Antennas at my station

(updated 2021-03-30)

Which band for which antenna?

Antennas have a fundamental frequency at which they operate best. This frequency typically occupies one of the bands, but, depending on the design of the antenna, it might also be suitable for other bands.

For each of the antennas we have, these related bands are summarised below. Bands are marked by stars (⭑) describing their suitability for each antenna. Essentially, the more stars the better: ⭑⭑⭑ means the frequency is in band, ⭑⭑ means it is <1% away from the centre of the band, ⭑ means it is <3% away, and ⭒ means it is <10% away. Other bands are just omitted.

Antenna 1 (neon green)

This antenna is about 39m long and its fundamental frequency is therefore around the 80m band, at about 3.65MHz. The half-wave dipole⁽ᵃ⁾ can be operated at a frequency where its length is ANY ODD MULTIPLE of half-wavelengths long, namely 10.974MHz, 18.290MHz, and 25.606MHz. These bands are all pretty narrow unfortunately but on the other hand these so-called WARC⁽ᵇ⁾ bands are free of contesters and are therefore a bit more chilled-out. And, of course, you can still use the other bands and play around with the ATU.

(a) rsgb.org — via https

(b) en.wikipedia.org — via https

• ✳️1️⃣→ ⭑⭑⭑ 80m, 3.5-3.8MHz.

• ✳️6️⃣→ ⭑⭑ 17m, 18.068-18.168MHz.

• ✳️8️⃣→ ⭑ 12m, 24.89-24.99MHz.

• ✳️4️⃣→ ⭒ 30m, 10.1-10.15MHz.

Antenna 2 (yellow)

This antenna is about 20m long and its fundamental frequency will be around 7.125MHz. By the same principle, the bands to use with this antenna are:

• ✳️3️⃣→ ⭑⭑⭑ 40m, 7.0-7.2MHz.

• ✳️7️⃣→ ⭑⭑⭑ 15m, 21.00-21.45MHz.

Exposure

This information is computed from formulae ICNIRP's 2020 guidelines⁽ᵃ⁾, but please note that at present they don't cover instantaneous exposure or guidelines for incident power density, energy density, induced current, or specific energy absorption rate. We also assume limits are for the general public and not the occupational limits. These figures relate to what is possible to check with the cheap EMF meter we use⁽ᵇ⁾, though it doesn't measure H-field above 300Hz anyway!

(a) icnirp.org — via https

(b) meterk.com — via https

For the 160m band:

• The E-field should not exceed 184V/m averaged over 30 minutes or 413V/m averaged over 6 minutes.

• The H-field should not exceed 1.38μT averaged over 30 minutes or 3.07μT averaged over 6 minutes.

For the 80m band:

• The E-field should not exceed 117V/m averaged over 30 minutes or 263V/m averaged over 6 minutes.

• The H-field should not exceed 0.73μT averaged over 30 minutes or 1.62μT averaged over 6 minutes.

For the 60m band:

• The E-field should not exceed 92V/m averaged over 30 minutes or 206V/m averaged over 6 minutes.

• The H-field should not exceed 0.51μT averaged over 30 minutes or 1.14μT averaged over 6 minutes.

For the 40m band:

• The E-field should not exceed 75V/m averaged over 30 minutes or 168V/m averaged over 6 minutes.

• The H-field should not exceed 0.38μT averaged over 30 minutes or 0.85μT averaged over 6 minutes.

For the 30m band:

• The E-field should not exceed 59V/m averaged over 30 minutes or 132V/m averaged over 6 minutes.

• The H-field should not exceed 0.27μT averaged over 30 minutes or 0.61μT averaged over 6 minutes.

For the 20m band:

• The E-field should not exceed 46V/m averaged over 30 minutes or 103V/m averaged over 6 minutes.

• The H-field should not exceed 0.19μT averaged over 30 minutes or 0.43μT averaged over 6 minutes.

For the 17m band:

• The E-field should not exceed 39V/m averaged over 30 minutes or 88V/m averaged over 6 minutes.

• The H-field should not exceed 0.15μT averaged over 30 minutes or 0.34μT averaged over 6 minutes.

For the 15m band:

• The E-field should not exceed 35V/m averaged over 30 minutes or 78V/m averaged over 6 minutes.

• The H-field should not exceed 0.13μT averaged over 30 minutes or 0.29μT averaged over 6 minutes.

For the 12m band:

• The E-field should not exceed 31V/m averaged over 30 minutes or 70V/m averaged over 6 minutes.

• The H-field should not exceed 0.11μT averaged over 30 minutes or 0.25μT averaged over 6 minutes.

For the 10m band:

• The E-field should not exceed 27V/m averaged over 30 minutes or 62V/m averaged over 6 minutes.

• The H-field should not exceed 0.09μT averaged over 30 minutes or 0.21μT averaged over 6 minutes.

▣

You are here:

rawles.net

↳ radio

· · ↳ my

· · · · ↳ antennas