There is a Log-Periodic antenna on the roof of the National Museum of American
History which part of the Smithsonian Institution.
Paul Gates, KD3JF
Volunteer at the NMAH
Dave Heil <email@example.com> wrote: Ken Brown wrote:
>> Only in very few outlying Embassies are there any over the air type
>> communications. Everything is or was on line encrypted. Basically any
>> outside wiring or antennas not allowed.
> I have seen log periodics on buildings in Europe. I notice those kinds
> of things. Most times, when I have investigated to see what is in the
> building on which the antenna is mounted, it has been a foreign embassy.
Some countries *used*, at least until 2000, quite a bit of HF. The
Chinese are an example. The Bulgarians used to have a cage dipole in
Helsinki in the mid-1980's. They had to give up their embassy building
in the 1990's. It seems that it had been the Estonian embassy and the
newly independent Estonians wanted it back.
> (foreign to the country I was in) I would expect them to use encryption
> whether by wire or by wireless, and to use wire most of the time.
That depends much on the agreements between the foreign embassy and the
host government. In most spots in Africa, leased lines are not an
option. The choices are HF and satellite. HF is slow and subject to
the vagaries of wave propagation. Encryption at HF adds overhead,
slowing the data rate.
> would think they might want to have a backup to wire. Wires after all
> can be cut.
That's why there's always a backup.
> Many of the installations I have seen may well be left over
> from the days when satellite comm links were not commonly available.
...or are the backups to leased lines or satellite communications.
> Even so, I think it would be wise to maintain an HF backup to the
> satellite system.
There are also sat backups for sats. :-)
> Additionally, some scheduled transmissions, perhaps
> sending null messages, would be a good idea to make sure the system
> works when it is really needed, and so that the sudden resumption of
> transmission after none at all, would not reveal anything.
There are always tests of backup systems and backup power.
> intelligence can be gleaned from traffic analysis, without decryption of
> the traffic.
Not so much, really. With the encryption, there is always a steady
stream of data. Nothing can be gleaned by looking at the data stream.
All one would see is a constant stream, day after day after day.
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