3 ms·

Iridium operates at 1620 MHz. Many cell signals operate much lower than that (ie some 4G at 700mhz). If you can fit a 4G antenna in a phone you can easily fit o

Iridium operates at 1620 MHz. Many cell signals operate much lower than that (ie some 4G at 700mhz). If you can fit a 4G antenna in a phone you can easily fit one for iridium.

turminal 5y ago
The problem here is the distance to the satellite, which is an order of magnitude bigger than what 4G technology is capable of.
jsjohnst 5y ago
> If you can fit a 4G antenna in a phone you can easily fit one for iridium The frequency isn’t the issue, it’s the distance it needs to transmit. Increased output power/longer distance needs a bigger antenna. Iridium / Starlink / other LEO satellites are >300 miles above the earth. Your smartphone doesn’t have even remotely enough power to transmit that far, good luck getting even 1/10th that distance for even a very shaky connection. As a concrete example, your phone’s cell radio transmits at 100-200mW into an antenna which has minimal additional gain. Iridium / Inmarsat phones transmit at around 10W into a higher gain and significantly larger antenna. That’s two orders of magnitude more EIRP in the end. Apple might be able to do an emergency beacon like transmission from an iPhone into LEO, but assuredly can not do a continuous transmission like in a phone call, even at very poor audio quality, without a relatively massive change in phone dimensions.
- vitaflo 5y ago
  Transmit power has nothing to do with antenna length. In fact if you change the antenna length you change the resonating frequency of the antenna. Satellites are also line of sight and most sat antennas radiate straight up instead of multi-directional like cell antennas. In any case iridium devices usually output max 2w. Same as 4G.
  - jsjohnst 5y ago
    > In any case iridium devices usually output max 2w. Not according to Iridium’s data sheets I just read and provided values in my post > Same as 4G Nope, back in AMPS days power could be up to 2W, but 4G UEs are almost always limited to a maximum of 23dBm (aka 200mW). > Transmit power has nothing to do with antenna length. Correct if you are purely talking about antenna design from a generic pov. In the case of a phone, it does matter because you can’t transmit 10W into an omnidirectional antenna pressed up against someone’s ear due to current regulations, so it necessitates moving the antenna further away (hence one reason sat phones have a “whip antenna”, but there are other reasons too). This effectively makes the antenna “larger”.

Iridium operates at 1620 MHz. Many cell signals operate much lower than that (ie some 4G at 700mhz). If you can fit a 4G antenna in a phone you can easily fit one for iridium.

turminal 5y ago

The problem here is the distance to the satellite, which is an order of magnitude bigger than what 4G technology is capable of.

jsjohnst 5y ago

> If you can fit a 4G antenna in a phone you can easily fit one for iridium The frequency isn’t the issue, it’s the distance it needs to transmit. Increased output power/longer distance needs a bigger antenna. Iridium / Starlink / other LEO satellites are >300 miles above the earth. Your smartphone doesn’t have even remotely enough power to transmit that far, good luck getting even 1/10th that distance for even a very shaky connection. As a concrete example, your phone’s cell radio transmits at 100-200mW into an antenna which has minimal additional gain. Iridium / Inmarsat phones transmit at around 10W into a higher gain and significantly larger antenna. That’s two orders of magnitude more EIRP in the end. Apple might be able to do an emergency beacon like transmission from an iPhone into LEO, but assuredly can not do a continuous transmission like in a phone call, even at very poor audio quality, without a relatively massive change in phone dimensions.

vitaflo 5y ago
Transmit power has nothing to do with antenna length. In fact if you change the antenna length you change the resonating frequency of the antenna. Satellites are also line of sight and most sat antennas radiate straight up instead of multi-directional like cell antennas. In any case iridium devices usually output max 2w. Same as 4G.
- jsjohnst 5y ago
  > In any case iridium devices usually output max 2w. Not according to Iridium’s data sheets I just read and provided values in my post > Same as 4G Nope, back in AMPS days power could be up to 2W, but 4G UEs are almost always limited to a maximum of 23dBm (aka 200mW). > Transmit power has nothing to do with antenna length. Correct if you are purely talking about antenna design from a generic pov. In the case of a phone, it does matter because you can’t transmit 10W into an omnidirectional antenna pressed up against someone’s ear due to current regulations, so it necessitates moving the antenna further away (hence one reason sat phones have a “whip antenna”, but there are other reasons too). This effectively makes the antenna “larger”.